Surgical techniques for the removal of mandibular wisdom teeth

Edmund Bailey; Wafa Kashbour; Neha Shah; Helen V Worthington; Tara F Renton; Paul Coulthard

doi:10.1002/14651858.CD004345.pub3

. 2020 Jul 26;2020(7):CD004345. doi: 10.1002/14651858.CD004345.pub3

Surgical techniques for the removal of mandibular wisdom teeth

Edmund Bailey ^1,^✉, Wafa Kashbour ², Neha Shah ¹, Helen V Worthington ³, Tara F Renton ⁴, Paul Coulthard ⁵

Editor: Cochrane Oral Health Group

PMCID: PMC7389870 PMID: 32712962

Abstract

Background

Pathology relating to mandibular wisdom teeth is a frequent presentation to oral and maxillofacial surgeons, and surgical removal of mandibular wisdom teeth is a common operation. The indications for surgical removal of these teeth are alleviation of local pain, swelling and trismus, and also the prevention of spread of infection that may occasionally threaten life. Surgery is commonly associated with short‐term postoperative pain, swelling and trismus. Less frequently, infection, dry socket (alveolar osteitis) and trigeminal nerve injuries may occur. This review focuses on the optimal methods in order to improve patient experience and minimise postoperative morbidity.

Objectives

To compare the relative benefits and risks of different techniques for surgical removal of mandibular wisdom teeth.

Search methods

Cochrane Oral Health’s Information Specialist searched the following databases: Cochrane Oral Health Trials Register (to 8 July 2019), the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library; 2019, Issue 6), MEDLINE Ovid (1946 to 8 July 2019), and Embase Ovid (1980 to 8 July 2019). We searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform for ongoing trials. We placed no restrictions on the language or date of publication.

Selection criteria

Randomised controlled trials comparing different surgical techniques for the removal of mandibular wisdom teeth.

Data collection and analysis

Three review authors were involved in assessing the relevance of identified studies, evaluated the risk of bias in included studies and extracted data. We used risk ratios (RRs) for dichotomous data in parallel‐group trials (or Peto odds ratios if the event rate was low), odds ratios (ORs) for dichotomous data in cross‐over or split‐mouth studies, and mean differences (MDs) for continuous data. We took into account the pairing of the split‐mouth studies in our analyses, and combined parallel‐group and split‐mouth studies using the generic inverse‐variance method. We used the fixed‐effect model for three studies or fewer, and random‐effects model for more than three studies.

Main results

We included 62 trials with 4643 participants. Several of the trials excluded individuals who were not in excellent health. We assessed 33 of the studies (53%) as being at high risk of bias and 29 as unclear. We report results for our primary outcomes below. Comparisons of different suturing techniques and of drain versus no drain did not report any of our primary outcomes. No studies provided useable data for any of our primary outcomes in relation to coronectomy.

There is insufficient evidence to determine whether envelope or triangular flap designs led to more alveolar osteitis (OR 0.33, 95% confidence interval (CI) 0.09 to 1.23; 5 studies; low‐certainty evidence), wound infection (OR 0.29, 95% CI 0.04 to 2.06; 2 studies; low‐certainty evidence), or permanent altered tongue sensation (Peto OR 4.48, 95% CI 0.07 to 286.49; 1 study; very low‐certainty evidence). In terms of other adverse effects, two studies reported wound dehiscence at up to 30 days after surgery, but found no difference in risk between interventions.

There is insufficient evidence to determine whether the use of a lingual retractor affected the risk of permanent altered sensation compared to not using one (Peto OR 0.14, 95% CI 0.00 to 6.82; 1 study; very low‐certainty evidence). None of our other primary outcomes were reported by studies included in this comparison.

There is insufficient evidence to determine whether lingual split with chisel is better than a surgical hand‐piece for bone removal in terms of wound infection (OR 1.00, 95% CI 0.31 to 3.21; 1 study; very low‐certainty evidence). Alveolar osteitis, permanent altered sensation, and other adverse effects were not reported.

There is insufficient evidence to determine whether there is any difference in alveolar osteitis according to irrigation method (mechanical versus manual: RR 0.33, 95% CI 0.01 to 8.09; 1 study) or irrigation volume (high versus low; RR 0.52, 95% CI 0.27 to 1.02; 1 study), or whether there is any difference in postoperative infection according to irrigation method (mechanical versus manual: RR 0.50, 95% CI 0.05 to 5.43; 1 study) or irrigation volume (low versus high; RR 0.17, 95% CI 0.02 to 1.37; 1 study) (all very low‐certainty evidence). These studies did not report permanent altered sensation and adverse effects.

There is insufficient evidence to determine whether primary or secondary wound closure led to more alveolar osteitis (RR 0.99, 95% CI 0.41 to 2.40; 3 studies; low‐certainty evidence), wound infection (RR 4.77, 95% CI 0.24 to 96.34; 1 study; very low‐certainty evidence), or adverse effects (bleeding) (RR 0.41, 95% CI 0.11 to 1.47; 1 study; very low‐certainty evidence). These studies did not report permanent sensation changes.

Placing platelet rich plasma (PRP) or platelet rich fibrin (PRF) in sockets may reduce the incidence of alveolar osteitis (OR 0.39, 95% CI 0.22 to 0.67; 2 studies), but the evidence is of low certainty. Our other primary outcomes were not reported.

Authors' conclusions

In this 2020 update, we added 27 new studies to the original 35 in the 2014 review. Unfortunately, even with the addition of these studies, we have been unable to draw many meaningful conclusions. The small number of trials evaluating each comparison and reporting our primary outcomes, along with methodological biases in the included trials, means that the body of evidence for each of the nine comparisons evaluated is of low or very low certainty.

Participant populations in the trials may not be representative of the general population, or even the population undergoing third molar surgery. Many trials excluded individuals who were not in good health, and several excluded those with active infection or who had deep impactions of their third molars.

Consequently, we are unable to make firm recommendations to surgeons to inform their techniques for removal of mandibular third molars. The evidence is uncertain, though we note that there is some limited evidence that placing PRP or PRF in sockets may reduce the incidence of dry socket. The evidence provided in this review may be used as a guide for surgeons when selecting and refining their surgical techniques. Ongoing studies may allow us to provide more definitive conclusions in the future.

Plain language summary

Comparing different surgical techniques used to remove wisdom teeth from the lower jaw

Background

The removal of wisdom teeth is a common operation, but it can cause short‐ and long‐term side effects. People may have their wisdom teeth removed if they are causing pain or infection, or if they are damaging other teeth or not breaking through the gum properly. Surgery has a risk of complications. One of the most common is dry socket (also known as alveolar osteitis). This is when a blood clot fails to form in the socket that the tooth has come out of, or the clot is disturbed before the socket has properly healed. Because the bones and nerves underlying the socket are exposed, it can be a very painful condition.

Review question

We aimed to find out the benefits and harms of different surgical techniques used to remove wisdom teeth from the lower jaw, specifically how surgeons can reduce the risk of complications following surgery. We considered the most important outcomes to be: dry socket, wound infection, long‐term damage to the nerves supplying sensation to the tongue and skin of the lower lip and chin, and problems such as excessive bleeding or a broken jaw.

Study characteristics

We searched for relevant studies up to 8 July 2019. We included 62 studies with 4643 participants. Many studies excluded people who were not in excellent health so the participants in the trials may not be truly representative.

Key results

The available evidence is inconclusive.

It is unclear if the position of the cut into the gum makes any difference to the outcomes.

It is unclear whether it is possible to avoid damaging a nerve to the tongue by using a surgical instrument called a lingual retractor.

It is unclear as to whether the type of surgical tool (a chisel or a rotating drill) used to remove bone from the jaw makes a difference to the likelihood of the wound becoming infected.

It is unclear if the amount and method of delivering saltwater to clean the tooth socket after the extraction makes any difference to the outcomes.

It is unclear whether different methods to stitch the gum after the tooth is removed makes any difference to the outcomes.

Placing products that are derived from the patient’s own blood into the tooth socket may help to reduce the occurrence of dry socket (a condition that causes intense pain a few days after extraction).

Another three surgical approaches were tested in the studies, but they did not measure the important outcomes.

Certainty of the evidence

None of the included studies were at low risk of bias. All of the studies were quite small. The quality of the studies varied, with most having flaws that could have biased their results. In addition, some of the results were very imprecise, with variation between them that could not be explained. For these reasons, we consider the available evidence to be uncertain. Future research may be able to provide dental surgeons and patients with clearer conclusions than those listed above.

Summary of findings

Background

Description of the condition

Surgical removal of mandibular third molars (lower wisdom teeth) is one of the most common operations undertaken in oral and maxillofacial surgery. It is difficult to find accurate figures for the number of people undergoing such procedures; however, it is estimated that the UK National Health Service funds the removal of third molars of approximately 152,000 people per year in England alone (McArdle 2012; McArdle 2018a). Mandibular third molars are also removed in private practice in the UK, as elsewhere in the world, but national systems for this data collection are less developed.

There are many indications for third molar removal, but the most common reason is recurrent infection around the tooth as it attempts to erupt but is impacted against bone or soft tissues (pericoronitis); a recent retrospective study of 1431 extracted third molars found that 49% of these were removed due to pericoronitis (McArdle 2012; McArdle 2018b). Other indications include unrestorable caries, caries in the adjacent tooth (Toedtling 2016), pulpal and periapical pathology, fracture of the tooth, and cyst development, amongst others. Most commonly, the benefits of surgical removal of a wisdom tooth include alleviation of the symptoms and signs of pericoronitis and its potential consequences. The symptoms of pericoronitis are pain, foul taste, swelling of the associated soft tissues about the tooth but also of the face, and restricted mouth opening (trismus). Local infection may spread and be associated with lymphadenopathy, pyrexia, and malaise. More rarely, swelling may threaten airway patency and life. Surgery is frequently associated with postoperative pain, swelling, and restricted mouth opening (trismus). Less common complications include infection, including alveolar osteitis (dry socket), trigeminal nerve injuries (inferior alveolar, lingual, and mylohyoid nerves) and, rarely, fracture of the mandible.

People requiring surgical removal of wisdom teeth are frequently anxious about anticipated postoperative pain, which may be severe. Such is the predictability of postoperative pain that this type of surgery is used as a model of pain for the clinical evaluation of novel analgesics (Bailey 2013; Moore 2015). The severity of pain usually peaks within several hours after surgery and may last for several days or more. Facial swelling may also alarm patients and typically peaks at around one or two days before subsiding over the subsequent days. Restricted mouth opening results from inflammation of the muscles that move the jaw and may be considered initially as having a protective function by encouraging the patient to rest the surgical site and permit healing. However, it may lead to difficulty in eating and functioning if it persists for more than a few days.

Alveolar osteitis (dry socket) has a reported incidence of 1% to 2.9% (Goldberg 1985; Muhonen 1997). Other studies have investigated the role of smoking and complexity of the extraction on the incidence of dry socket (Parthasarathi 2011). The socket has exposed bone, which is extremely painful and sensitive to touch. This condition can be difficult to manage and usually causes pain for up to two weeks. Less commonly an infection presents with pus in the surgical site and may be associated with signs such as lymphadenopathy or raised body temperature. This infection may also spread to the surrounding tissue spaces. Damage to the branches of the trigeminal nerve may arise because of their proximity to the mandibular third molar and consequent physical damage during surgery. Sensory disturbance may be temporary or permanent, and is usually described as temporary if recovery of normal sensation occurs within four to six months (Mason 1988). The degree and description of altered sensation is variable and includes reduced sensation (hypoaesthesia), abnormal sensation (paraesthesia), and unpleasant painful sensation (dysaesthesia) (Jones 1992), and pain on touching (mechanical allodynia). The incidence of temporary and permanent nerve damage following the surgical removal of third molar teeth varies considerably between reports and may be related to a number of factors including the difficulty of surgery, surgical technique, and the skill of the surgeon. The incidence of temporary lingual (tongue) nerve disturbance has been reported to be 0%, Chiapasco 1993, to 15%, Rood 1983, and that of permanent disturbance to be 0%, Schultze‐Mosgau 1993, to 2%, Rood 1992. Inferior alveolar nerve damage has been reported to ocur in about 5% (temporary) and 0.2% (permanent) of patients (Smith 1997), and this affects the sensation of the skin of the lower lip and chin. In a study of 4338 mandibular third molar extractions, 0.35% experienced inferior alveolar nerve deficit and 0.69% experienced lingual nerve deficit; of these, 0.002% and 0.003% experienced inferior alveolar nerve or lingual nerve deficit after six months, respectively (Cheung 2010). Fracture of the mandible may occur during the surgery or postoperatively. The incidence of this rare complication is estimated to be about 1 in 28,000 operations (Libersa 2002). Whilst this complication may be managed very effectively with techniques such as reduction and fixation with mini plates, the patient may experience significantly increased pain and swelling along with the need for hospitalisation. In the UK National Health Service, outcome data on these complications is being analysed, with Patient Reported Outcome Measures (PROMs) and Patient Reported Experience Measures (PREMs) being used to assess the quality and safety of healthcare providers in relation to third molar surgery. In parts of the world without national health or reporting systems, it is not possible to collect accurate outcome data.

Description of the intervention

Various techniques have been developed to permit the successful removal of the third molar whilst minimising complication rates.

Surgical flap design

A surgical incision and soft‐tissue mucoperiosteal flap is typically raised to permit access to the wisdom tooth for removal. Various modifications to the design of the flap have been advocated in order to offer advantage and improve the outcome for the patient. Examples include envelope, triangular, comma‐shaped, bayonet flaps, and further variations of these (Chen 2017).

Lingual nerve protection

A mucoperiosteal flap is usually raised on the buccal aspect of the tooth to be removed, but the practice of also raising a lingual flap to improve access and protect the lingual nerve varies according to differing opinions and cultural and historic views. When bone is being removed buccally only, there is no danger to the lingual nerve that lies in close proximity to the wisdom tooth on its lingual aspect. However, the lingual nerve is at risk of physical injury from the bur when distolingual bone is removed. Distolingual bone may need to be removed to permit tooth removal according to its type of impaction and typically for distolingually impacted teeth. An instrument may be placed between the bone to be removed and the lingual flap enclosing the nerve to protect it from physical injury during bone removal. This ‘lingual nerve protection’ has been the tradition in the UK and in some other parts of the world, but less so in the USA (Pell 1933). Whilst the intention of placing a barrier instrument is to prevent permanent lingual nerve injury, some surgeons believe that it is preferable not to place an instrument for nerve protection, as there is the potential to cause a temporary nerve injury (Renton 2001). However, in this situation, it is imperative not to remove bone distal to the tooth and only bone on the buccal aspect.  The type of instrument to be used for lingual nerve protection has also been the subject of investigation, as some prefer to use a wider instrument to ensure more effective nerve protection, although this may be more invasive to place (Greenwood 1994).

Bone removal techniques

Bone removal may be carried out using drills, chisels or, more recently, a novel technique using piezoelectric surgery (Degerliyurt 2009). The choice of surgical technique has been implicated in the incidence of nerve damage as well as the severity of pain and swelling. The most common technique using a chisel is the 'lingual split bone technique', in which a section of distolingual bone about the wisdom tooth is fractured off to facilitate the removal of the impacted tooth, especially distoangular impacted teeth. This technique, in which the socket is saucerized, was originally developed to reduce infection at a time when this was common and fatalities were not unknown. It was later modified when the surgical drill was introduced (Ward 1956).

Wound irrigation techniques

Some surgeons have advocated using mechanical methods of irrigating the surgical wound on removal of the tooth rather than doing this manually. Similarly, it has been thought that larger volumes of irrigant are preferable for outcomes because ensuring removal of more bony debris may reduce the incidence of infection.

Wound closure

The amount of wound closure, whether complete, partial, or left open, has been the subject of debate, with proponents of each claiming a difference in postoperative pain and swelling (Bello 2011; Osunde 2012).

Suturing techniques

Suture technique may also have an impact on healing and surgical outcomes relating to third molar surgery (Waite 2006)

Surgical drains

Some surgeons have recommended placing a surgical drain to reduce the size of haematoma as well as postoperative complications (Osunde 2011b), although in many countries this practice is rarely used in the absence of a collection of pus. An alternative to the use of surgical drains is to allow drainage by not completely closing the surgical wound over the socket.

Use of autologous blood concentrates

Platelet‐rich fibrin (PRF) is a second‐generation platelet concentrate that was initially developed by a team based in France for use in oral and maxillofacial surgery (Dohan 2006). PRF is a product of centrifuged blood. Anticoagulant is unnecessary as activation of clotting of the sample is encouraged. This process produces fibrinogen as the end product of the coagulation cascade; circulating thrombin transforms this into fibrin. This fibrin clot can then be separated from the sample, and the clot will contain platelets within a fibrin mesh. Resistant autologous fibrin membranes can be derived from this mesh by driving the serum from the blood clot. PRF is considered to be a healing biomaterial that appears to accelerate physiologic healing (Choukroun 2006). A recent systematic review on the use of PRF in soft‐tissue wound healing concluded that the material has a positive effect on healing in a variety of soft‐tissue defects (Miron 2017). Commercially available fibrin sealants mimic the final part of the coagulation cascade (fibrinogen is converted to fibrin) in wounds; they are often used instead of sutures to encourage wound healing. These sealants have been shown to reduce postoperative bleeding from dental extraction sockets in patients who are anticoagulated with warfarin (Bodner 1998). The technique required the drawing of blood from the patient and the use of appropriate equipment to prepare the PRF/PRP, which may add significant cost.

Root retention techniques/coronectomy

If a wisdom tooth has a particularly intimate relationship with the inferior alveolar nerve, then injury is more likely on tooth removal, and some have advocated leaving a part of the tooth root in place to reduce this risk rather than removing the whole tooth. Retaining a small part of the root or root apex to reduce the risk of nerve injury has been common practice for many decades, but recently some surgeons have recommended leaving all of the tooth root in place in a technique known as coronectomy (Renton 2012). There has been discussion regarding the fate of the retained roots after coronectomy (Pedersen 2018). It is thought that the majority of root migration occurs within the first 6 to 12 months postoperatively (Leung 2018), but there has been concern about the potential for later pain and infection. Coronectomy may not be successful in that the root may be mobilised during the procedure (Jowett 2016).

How the intervention might work

Wisdom tooth removal is a frequently performed procedure. There is debate about the best way to remove wisdom teeth. It is important to review the evidence base for these surgical techniques in order to provide the best experience for patients and to minimise complication rates.

Why it is important to do this review

Cochrane Oral Health undertook an extensive prioritisation exercise in 2014 to identify a core portfolio of high‐priority reviews (Worthington 2015); this review was identified as a priority by the oral and maxillofacial surgery expert panel (Cochrane Oral Health priority reviews).

Research suggests that wisdom tooth removal has an immediate negative impact on patients' working and social lives. In one study, patients took an average of 1.6 days off work, with over one‐third of patients stating that the surgery had affected their performance at work (Colorado‐Bonnin 2006); participation in social activities, sports, and other hobbies is also negatively affected (Conrad 1999). For some patients, quality of life (QoL) is reduced for one to two weeks after surgery (Savin 1997), and it is considered a major event for large numbers of patients (Van Wijk 2007). A recent study emphasised the emotional impacts of third molar surgery and noted its effects on QoL in relation to anxiety and worry in particular (Beech 2017). The detrimental effects on QoL may be present for considerably longer for those who suffer nerve injury (Hillerup 2007). It is important to summarise and present the current evidence base for third molar surgical techniques so that every effort is made to reduce postoperative morbidity and improve the patient experience for this commonly performed surgical procedure.

Objectives

To compare the relative benefits and risks of different techniques for the surgical removal of mandibular wisdom teeth.

Methods

Criteria for considering studies for this review

Types of studies

Randomised controlled trials (RCTs) comparing surgical techniques for the removal of mandibular wisdom teeth.

Types of participants

People requiring the surgical removal of mandibular wisdom teeth. We excluded studies with participants who required surgical removal of a maxillary third molar tooth at the same operation unless the maxillary third molar was erupted and removed as a simple extraction with an elevator or forceps, or both. The reason for this is that it would not be clear which operation led to the reported outcome (e.g. pain, swelling, restricted mouth opening). We also excluded participants requiring removal of a mandibular wisdom tooth with only elevators or forceps without elevating a flap.

Types of interventions

Different surgical techniques to remove mandibular wisdom teeth, including surgical flap design, lingual nerve protection, root retention techniques, bone removal technique, wound irrigation technique, suturing techniques, wound closure, the use of surgical drains, and the use of plasma rich protein/plasma rich fibrin (PRF/PRP).

Types of outcome measures

Primary outcomes

Alveolar osteitis (seven days).
Infection: wounds becoming infected (presence of pus) (seven days).
Permanent altered tongue, chin, or lip sensation (more than six months).
Adverse effects, such as reactionary bleeding or fracture of the mandible (up to 30 days).

Secondary outcomes

Temporary altered tongue sensation (only the time point closest to one‐month postoperatively was used).
Temporary altered chin skin or lower lip sensation (only the time point closest to one‐month postoperatively was used).
Postoperative pain (only the time point closest to one‐day postoperatively was used).
Swelling (only the time point closest to one‐week postoperatively was used).
Trismus (restricted mouth opening) (only the time point closest to one‐week postoperatively was used).

We did not include studies solely looking at periodontal outcomes relating to the second permanent molar.

Search methods for identification of studies

Electronic searches

Cochrane Oral Health's Information Specialist conducted systematic searches in the following databases for RCTs and controlled clinical trials. There were no language, publication year, or publication status restrictions.

Cochrane Oral Health Trials Register (searched 8 July 2019) (Appendix 1).
Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 6) in the Cochrane Library (searched 8 July 2019) (Appendix 2).
MEDLINE Ovid (1946 to 8 July 2019) (Appendix 3).
Embase Ovid (1980 to 8 July 2019) (Appendix 4).

Subject strategies were modelled on the search strategy designed for MEDLINE Ovid. Where appropriate, they were combined with subject strategy adaptations of the Highly Sensitive Search Strategy designed by Cochrane for identifying RCTs and controlled clinical trials as described in Chapter 6 of the Cochrane Handbook for Systematic Reviews of Interventions (Lefebvre 2011).

Searching other resources

Cochrane Oral Health’s information specialist searched the following trial registries for ongoing studies:

US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (clinicaltrials.gov; searched 8 July 2019) (Appendix 5);
World Health Organization International Clinical Trials Registry Platform (apps.who.int/trialsearch; searched 8 July 2019) (Appendix 6).

We wrote to authors of the RCTs identified and personal contacts in order to identify unpublished or ongoing studies. We checked the bibliographies of papers and review articles for any further studies.

We checked that none of the studies included in this review was retracted due to error or fraud.

We did not perform a separate search for adverse effects of interventions used, considering only adverse effects described in the included studies.

Data collection and analysis

Selection of studies

We exported the results of the database searches for this 2020 update into Covidence (Covidence). Three review authors (WK, NS and EB) independently scanned the titles and abstracts (when available). We designed the search to be sensitive and to include controlled clinical trials; these were filtered out early in the selection process if they were not randomised. For studies that appeared to meet the inclusion criteria, or for which there were insufficient data in the title and abstract to make a clear decision, we obtained the full study report, which two review authors (WK, NS) independently assessed to establish whether the studies met the inclusion criteria or not. Any disagreements were resolved by discussion; we planned to consult a third review author (EB) if required. This was necessary in a small number of cases.

All studies meeting the inclusion criteria underwent a validity assessment in Covidence and data extraction by EB, WK, and NS. We recorded any studies excluded at this or subsequent stages, with reasons for their exclusion, in the Characteristics of excluded studies tables.

Data extraction and management

In the 2020 update, two review authors (WK, NS) independently extracted study data using specially designed data extraction forms. We piloted the data extraction forms on several papers and modified the forms as required before use. Any disagreements were discussed and a third review author (EB) was consulted where necessary. We contacted authors for clarification or missing information whenever possible.

For each trial, we recorded the following data:

year of publication, country of origin, source of study funding, design of the trial (split‐mouth or parallel group);
details of the participants including demographic characteristics, source of recruitment, and criteria for inclusion and exclusion;
details about the type of surgical intervention, and the control intervention;
details of the outcomes reported, including method of assessment and time intervals.

We also noted whether or not an a priori calculation had been undertaken for sample size.

Assessment of risk of bias in included studies

We undertook assessment of risk of bias in Covidence (Covidence), following the Cochrane 'Risk of bias' tool as described in Chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). The tool addresses the following domains: sequence generation; allocation sequence concealment; blinding of participants, surgeons, and assessors; incomplete outcome data; selective outcome reporting; and other bias. Blinding of participants was straightforward in some studies as participants were under a general anaesthetic.

We recorded each piece of information extracted for the 'Risk of bias' tool, together with the precise source of this information. The review authors were not blinded to the names of the authors, institutions, journal, or results of a study. Two review authors performed 'Risk of bias' assessment independently. Any disagreements were resolved by consensus, with the assistance of a third review author.

We tabulated the risk of bias for each included study (see Characteristics of included studies), along with a judgement of low, high, or unclear risk of bias for each domain. 'Risk of bias' summaries are presented in Figure 1 and Figure 2.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

Overall risk of bias for each trial

After taking into account the additional information provided by the authors of the trials, we grouped the studies into the following categories.

Low risk of bias (plausible bias unlikely to seriously alter the results) if all criteria were met.
Unclear risk of bias (plausible bias that raises some doubt about the results) if one or more criteria were partly met or there was insufficient information to know if they were met (for example, if study authors had made some attempt to conceal the allocation of participants, to blind the assessors, or to give an explanation for withdrawals, but these attempts were not judged to be ideal).
High risk of bias (plausible bias that seriously weakens confidence in the results) if one or more criteria were not met as described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).

Measures of treatment effect

In parallel trials, for dichotomous outcomes, we expressed the estimate of effect of an intervention as risk ratios (RRs) together with 95% confidence intervals (CIs). We used Peto odds ratios (ORs) when the event rate was very low. For continuous outcomes, we used means and standard deviations (SDs) to summarise the data for each trial employing mean differences (MDs) and 95% CIs. For data analysis from cross‐over or split‐mouth trials, we took into account the pairing of the data using generic inverse‐variance (GIV) outcome type in Review Manager 5 (RevMan; Stedman 2011). We estimated OR for dichotomous data produced by cross‐over and split‐mouth designed studies, after obtaining the log OR and its standard error (SE), using approved Cochrane methods (Becker‐Balagtas methods detailed in Curtin 2002, and assuming an intraclass correlation (ICC) of 0.5 to account for pairing). We estimated MDs, accompanied by 95% CI for relevant continuous outcome data, via GIV in Review Manager 5 by utilising SEs, and deriving these from SDs where SEs were unavailable (again, using standardised Cochrane methods as outlined in Chapter 7 of the Cochrane Handbook for Systematic Reviews of Interventions) (Higgins 2011).

Unit of analysis issues

Study participants had either one or two mandibular wisdom teeth, and these were frequently presented as independent data, so the CIs were slightly narrower than they should be, and P values slightly less. If we were unable to obtain data taking the clustering of the teeth within participants into account, we used these data but were careful about the interpretation. As expected, many of these trials were split‐mouth studies, where the teeth in each participant were surgically removed by different methods (either during the same operation, or at different times). We analysed the data from split mouth‐studies according to methods outlined in the Measures of treatment effect section.

Dealing with missing data

Data from split‐mouth studies are frequently presented omitting the 'paired' relationship of the data. We made estimates of the SE for the continuous outcomes assuming a correlation coefficient of 0.5, and methods for the dichotomous data are outlined in the Measures of treatment effect section. We estimated missing SDs using the methods outlined in Chapter 7 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Some published data related to pain, swelling, and maximum mouth opening could not be used in this review for reasons that are explained in Table 10, Table 11, and Table 12. We contacted trial authors to obtain the raw data for these studies, but no additional unpublished data could be obtained.

1. Unuseable published data related to pain at 24 hours.

Studies	Comparison	Subgroup	Reasons
Rabi 2017	Flap design	Triangular vs envelope flap	Pain assessed on a visual scale from no pain to severe pain.
Şimşek Kaya 2019	Flap design	Enveloped flap vs modified triangular flap	Standard deviations were not provided.
Basheer 2017	Bone removal techniques	Piezoelectric vs rotary osteotomy technique	Pain assessed on a visual scale from no pain to severe pain.
Mantovani 2014	Bone removal techniques	Piezoelectric (ultrsound) device vs traditional surgery with bur	Pain assessed at day 2
Acar 2017	Suturing techniques	Horiztonal mattress vs simple interrupted suturing	Unable to calculate MD and SE from data available
Gogulanathan 2015	Suturing techniques	Fibrin sealant vs conventional suturing	Not VAS ‐ numerical scale used
Kumar 2016	Surgical drain	Tube drain vs none	Pain assessed on a visual scale from no pain to severe pain.
Dutta 2016	Wound closure with autologous platelet concentrates	PRF vs none vs PRF + hydroxyapatite	Pain assessed on 6‐point scale.
Kumar 2015	Wound closure autologous with platelet concentrates	Plasma rich fibrin vs none	Data presented as mild, slight, severe.
Unsal 2018	Wound closure autologous with platelet concentrates	PRF vs none	A verbal rating scale was used to evaluate postoperative pain level, which comprised 6 pain severity descriptors: none, mild, moderate, severe, very severe, and excruciating. Not possible to convert this to VAS data
Uyanik 2015	Wound closure autologous with platelet concentrates	Plasma rich fibrin vs none	Data presented as a sum of 7 days.

Studies	Comparisons	Subgroup	Reasons
Şimşek Kaya 2019	Flap design	Modified triangular flap vs envelope	Trismus data were presented as a percentage of the differences between measurements.
Acar 2017	Suturing techniques	Horiztonal mattress vs simple interrupted suturing	Unable to calculate MD and SE from data available
Kumar 2015	Wound closure with autologous platelet concentrates	PRF vs none	Trismus data were presented as a percentage of the differences between pre‐ and postoperative measurements.
Uyanik 2015	Wound closure with autologous platelet concentrates	PRF or a combination of PRF and piezoelectric surgery vs conventional rotatory osteotomy	Trismus data were presented as a percentage of the differences between measurements.

Triangular flap compared with envelope flap for the removal of mandibular wisdom teeth
Population: adults with mandibular third molars requiring removal Setting: oral surgery Intervention: triangular flap¹ Comparison: envelope flap
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Envelope flap	Triangular flap
Alveolar osteitis (1‐week follow‐up)	132 per 1000²	48 per 1000 (19 to 73)	OR 0.33 (0.09 to 1.23)	187 (5 studies)	⊕⊕⊝⊝ low³	Triangular (short) vs envelope. Insufficient evidence to claim either is better
Wound infection (1‐week follow‐up)	46 per 1000²	14 per 1000 (2 to 90)	OR 0.29 (0.04 to 2.06)	65 (2 studies)	⊕⊕⊝⊝ low⁴	Triangular (long) vs envelope. Insufficient evidence to claim either is better
Permanent altered tongue, chin, or lip sensation (more than 6 months)	20 per 1000 ²	90 per 1000 (1 to 1000)	Peto OR 4.48 (0.07 to 286.49)	45 (1 study)	⊕⊝⊝⊝ verylow⁵	Triangular (long) vs envelope. Insufficient evidence to claim either is better
Adverse effects ‐ reactionary bleeding (up to 30 days)	Not reported
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; OD: odds ratio
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

Retractor compared with no retractor during the removal of mandibular wisdom teeth
Patopulation: adults with mandibular third molars requiring removal Setting: oral surgery Intervention: lingual retractor placed (subperiosteal or Free's) Comparison: no retractor
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	No retractor	Retractor
Alveolar osteitis (1‐week follow‐up)	Not reported
Wound infection (1‐week follow‐up)	Not reported
Permanent altered tongue, chin, or lip sensation (more than 6 months)	5 per 1000¹	1 per 1000 (0 to 33)	Peto OR 0.14 (0.00 to 6.82)	380 (1 study)	⊕⊝⊝⊝ verylow²	Insufficient evidence to claim either is better
Adverse effects ‐ reactionary bleeding (up to 30 days)	Not reported
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; OR: odds ratio
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

Bone removal techniques for the removal of mandibular wisdom teeth
Population: adults with mandibular third molars requiring removal Setting: oral surgery Intervention: bone removal techniques Comparison: conventional technique
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Bone removal with bur	Intervention bone removal technique
Alveolar osteitis (1‐week follow‐up)	Not reported
Wound infection (1‐week follow‐up)	58 per 1000¹	58 per 1000 (19 to 165)	OR 1.00 (0.31 to 3.21)	52 (1 study)	⊕⊝⊝⊝ verylow²	The intervention used lingual split with chisel. Insufficient evidence to claim either is better
Permanent altered tongue, chin, or lip sensation (more than 6 months)	Not reported
Adverse effects ‐ reactionary bleeding (up to 30 days)	Not reported
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; OR: odds ratio
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

Irrigation techniques (A compared to B) following the removal of mandibular wisdom teeth
Population: adults with mandibular third molars requiring removal Setting: oral surgery Intervention: irrigation technique A Comparison: irrigation technique B
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Irrigation technique B	Irrigation technique A
	Manual irrigation (low volume)	Mechanical irrigation (high volume)
Alveolar osteitis (up to 1‐week follow‐up)	10 per 1000¹	3 per 1000 (0 to 81)	RR 0.33 (0.01 to 8.09)	99 (1 study)	⊕⊝⊝⊝ verylow²	Single split‐mouth study. Insufficient evidence to claim either is better
Wound infection (up to 1‐week follow‐up)	20 per 1000¹	10 per 1000 (10 to 109)	RR 0.5 (0.05 to 5.43)	99 (1 study)	⊕⊝⊝⊝ verylow²	Insufficient evidence to claim either is better
Permanent altered tongue, chin, or lip sensation (more than 6 months)	Not reported
Adverse effects (up to 30 days)	Not reported
Mechanical irrigation (low volume versus high volume)
	Low volume (approximately 25 mL)	High volume (approximately 175 mL)
Alveolar osteitis (up to 1‐week follow‐up)	10 per 1000¹	5 per 1000 (3 to 10)	RR 0.52 (0.27 to 1.02)	211 (1 study)	⊕⊝⊝⊝ very low²	Insufficient evidence to claim either is better
Wound infection (up to 1‐week follow‐up)	28 per 1000¹	5 per 1000 (1 to 38)	RR 0.17 (0.02 to 1.37)	211 (1 study)	⊕⊝⊝⊝ very low²	Insufficient evidence to claim either is better
Permanent altered tongue, chin, or lip sensation (more than 6 months)	Not reported
Adverse effects (up to 30 days)	Not reported
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; RR: risk ratio
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

Primary versus secondary wound closure after the removal of mandibular wisdom teeth
Population: adults with mandibular third molars requiring removal Setting: oral surgery Intervention: primary (complete) wound closure Comparison: secondary (partial) wound closure
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Secondary wound closure	Primary wound closure
Alveolar osteitis (up to 1‐week follow‐up)	43 per 1000¹	43 per 1000 (18 to 103)	RR 0.99 (0.41 to 2.40)	375 (3 studies)	⊕⊕⊝⊝ low²	Insufficient evidence to claim either is better
Wound infection (up to 1‐week follow‐up)	50 per 1000³	13 per 1000	RR 4.77 (0.24 to 96.34)	82 (1 study)	⊕⊝⊝⊝ verylow⁴	Insufficient evidence to claim either is better
Permanent altered tongue, chin, or lip sensation (more than 6 months)	Not reported
Adverse effects ‐ reactionary bleeding (up to 30 days)	175 per 1000¹	72 per 1000 (19 to 257)	RR 0.41  (0.11 to 1.47)	82 (1 study)	⊕⊝⊝⊝ very low⁴	Insufficient evidence to claim either is better
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; RR: risk ratio
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

Horizontal mattress compared with conventional suturing after the removal of mandibular wisdom teeth
Population: adults with mandibular third molars requiring removal Settings: oral surgery Intervention: horizontal mattress/fibrin sealant Comparison: conventional suturing
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)
	Assumed risk	Corresponding risk

Alveolar osteitis (up to 1‐week follow‐up)	Not reported
Wound infection (up to 1‐week follow‐up)	Not reported
Permanent altered tongue, chin, or lip sensation (more than 6 months)	Not reported
Adverse effects ‐ reactionary bleeding (up to 30 days)	Not reported
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

Drain versus no drain after the removal of mandibular wisdom teeth
Population: adults with mandibular third molars requiring removal Setting: oral surgery Intervention: drain (tube drain or gauze drain) Comparison: no drain
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)
	Assumed risk	Corresponding risk
	No drain	Drain
Alveolar osteitis (up to 1‐week follow‐up)	Not reported
Wound infection (up to 1‐week follow‐up)	Not reported
Permanent altered tongue, chin, or lip sensation (more than 6 months)	Not reported
Adverse effects ‐ reactionary bleeding (up to 30 days)	Not reported
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

Wound closure with blood product compared to conventional method after the removal of mandibular wisdom teeth
Population: adults with mandibular third molars requiring removal Setting: oral surgery Intervention: wound closure with blood products (PRF) Comparison: conventional method
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	None	PRP/PRF
Alveolar osteitis (up to 1‐week follow‐up)	205 per 1000	91 per 1000 (54 to 147)	OR 0.39 (0.22 to 0.67)	128 (2 studies)	⊕⊕⊝⊝ low¹	Favours PRF
Wound infection (up to 1‐week follow‐up)	Not reported
Permanent altered tongue, chin, or lip sensation (more than 6 months)	Not reported
Adverse effects ‐ reactionary bleeding (up to 30 days)	Not reported
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; OR: odds ratio; PRP: platelet rich plasma; PRF: platelet rich fibrin
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

Coronectomy versus complete extraction of mandibular wisdom teeth
Population: adults with mandibular third molars requiring removal Setting: oral surgery Intervention: coronectomy Comparison: complete extraction
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)
	Assumed risk	Corresponding risk
	Complete extraction	Coronectomy
Alveolar osteitis (up to 1‐week follow‐up)	Not reported
Wound infection (up to 1‐week follow‐up)	Not reported
Permanent altered tongue, chin, or lip sensation (more than 6 months)	Not reported
Adverse effects ‐ reactionary bleeding (up to 30 days)	Not reported
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Alveolar osteitis (7 days)	7		Odds Ratio (IV, Random, 95% CI)	Subtotals only
1.1.1 Triangular flap (short) versus envelope flap	5	187	Odds Ratio (IV, Random, 95% CI)	0.33 [0.09, 1.23]
1.1.2 Pedicle flap versus envelope flap	1	52	Odds Ratio (IV, Random, 95% CI)	0.08 [0.01, 0.97]
1.1.3 Triangular flap (long) versus envelope flap	1	45	Odds Ratio (IV, Random, 95% CI)	0.37 [0.02, 8.31]
1.2 Wound infection (7 days)	4		Odds Ratio (IV, Fixed, 95% CI)	Subtotals only
1.2.1 Triangular flap (long) versus envelope flap	2	65	Odds Ratio (IV, Fixed, 95% CI)	0.29 [0.04, 2.06]
1.2.2 Pedicle flap versus envelope flap	1	52	Odds Ratio (IV, Fixed, 95% CI)	5.30 [0.47, 59.36]
1.2.3 Reverse‐L versus alternative single incision flap	1	33	Odds Ratio (IV, Fixed, 95% CI)	3.18 [0.56, 17.98]
1.3 Permanent altered tongue sensation (> 6 months)	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Subtotals only
1.3.1 Triangular flap (long) versus envelope flap	1	45	Peto Odds Ratio (Peto, Fixed, 95% CI)	4.48 [0.07, 286.49]
1.4 Adverse effects ‐ wound dehiscence (up to 30 days)	2		Risk Ratio (IV, Fixed, 95% CI)	Subtotals only
1.4.1 Triangular flap (short) versus envelope flap	1	19	Risk Ratio (IV, Fixed, 95% CI)	1.00 [0.16, 6.38]
1.4.2 Triangular flap (long) versus envelope flap	1	20	Risk Ratio (IV, Fixed, 95% CI)	0.14 [0.02, 1.06]
1.5 Pain present at 24 hours (yes/no)	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.5.1 Triangular flap (long) versus envelope flap	1	45	Risk Ratio (M‐H, Fixed, 95% CI)	1.25 [0.27, 5.70]
1.6 Mean pain at 24 hours (0 to 10 VAS)	7		Mean Difference (IV, Random, 95% CI)	Subtotals only
1.6.1 Triangular flap (short) versus envelope flap	4	161	Mean Difference (IV, Random, 95% CI)	‐0.84 [‐1.65, ‐0.03]
1.6.2 Comma‐shaped incision versus modified envelope flap	1	100	Mean Difference (IV, Random, 95% CI)	‐1.18 [‐1.37, ‐0.99]
1.6.3 Reverse‐L flap versus alternative single incision flap	1	33	Mean Difference (IV, Random, 95% CI)	‐0.80 [‐1.41, ‐0.19]
1.6.4 Triangular flap (long) versus envelope flap	1	25	Mean Difference (IV, Random, 95% CI)	‐0.83 [‐2.92, 1.26]
1.7 Swelling present (after 1 week) (yes/no)	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.7.1 Triangular flap (long) versus envelope flap	1	45	Risk Ratio (M‐H, Fixed, 95% CI)	0.25 [0.05, 1.21]
1.8 Mean swelling (after 1 week)	7		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
1.8.1 Triangular flap (short) versus envelope flap	2	99	Mean Difference (IV, Fixed, 95% CI)	0.60 [0.25, 0.95]
1.8.2 Pedicle flap versus envelope flap	1	52	Mean Difference (IV, Fixed, 95% CI)	0.21 [‐0.09, 0.51]
1.8.3 Comma‐shaped incision versus modified envelope flap	1	100	Mean Difference (IV, Fixed, 95% CI)	‐2.38 [‐2.81, ‐1.95]
1.8.4 Reverse‐L flap versus alternative single incision flap	1	33	Mean Difference (IV, Fixed, 95% CI)	0.20 [‐0.22, 0.62]
1.8.5 Triangular flap (long) versus envelope flap	2	40	Mean Difference (IV, Fixed, 95% CI)	0.68 [0.18, 1.18]
1.9 Trismus (after 1 week) (yes/no)	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.9.1 Triangular flap (long) versus envelope flap	1	45	Risk Ratio (M‐H, Fixed, 95% CI)	2.00 [0.24, 16.36]
1.10 Maximum mouth opening (after 1 week) (SMD)	2	158	Std. Mean Difference (IV, Fixed, 95% CI)	‐0.67 [‐1.04, ‐0.30]
1.10.1 Triangular flap (short) versus envelope flap	2	158	Std. Mean Difference (IV, Fixed, 95% CI)	‐0.67 [‐1.04, ‐0.30]
1.11 Maximum mouth opening (after 1 week) (MD)	3		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
1.11.1 Comma‐shaped incision versus modified envelope flap	1	100	Mean Difference (IV, Fixed, 95% CI)	1.20 [0.07, 2.33]
1.11.2 Triangular flap (long) versus envelope flap	2	65	Mean Difference (IV, Fixed, 95% CI)	‐1.22 [‐2.11, ‐0.33]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 Permanent altered sensation (up to 6 months)	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Subtotals only
2.1.1 Lingual flap and reflection versus no lingual flap	1	380	Peto Odds Ratio (Peto, Fixed, 95% CI)	0.14 [0.00, 6.82]
2.2 Temporary altered sensation (up to 1 month)	3	735	Odds Ratio (IV, Fixed, 95% CI)	4.18 [1.75, 9.98]
2.2.1 Subperiosteal lingual nerve protection versus none	1	300	Odds Ratio (IV, Fixed, 95% CI)	3.39 [0.35, 32.97]
2.2.2 Free's retractor lingual nerve protection versus none	1	55	Odds Ratio (IV, Fixed, 95% CI)	12.09 [1.03, 142.26]
2.2.3 Lingual flap and reflection versus no lingual flap	1	380	Odds Ratio (IV, Fixed, 95% CI)	3.64 [1.31, 10.08]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
3.1 Wound infection (7 days)	1		Odds Ratio (IV, Fixed, 95% CI)	Subtotals only
3.1.1 Lingual split chisel versus lingual split bur	1	52	Odds Ratio (IV, Fixed, 95% CI)	1.00 [0.31, 3.21]
3.2 Temporary alteration of tongue sensation (< 1 month)	1		Odds Ratio (IV, Fixed, 95% CI)	Subtotals only
3.2.1 Lingual split chisel versus lingual split bur	1	52	Odds Ratio (IV, Fixed, 95% CI)	3.06 [0.27, 34.48]
3.3 Temporary alteration of chin sensation (< 1 month)	1		Odds Ratio (IV, Fixed, 95% CI)	Subtotals only
3.3.1 Lingual split chisel versus lingual split bur	1	52	Odds Ratio (IV, Fixed, 95% CI)	0.24 [0.04, 1.31]
3.4 Pain at 24 hours (0‐to‐10 VAS)	2		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
3.4.1 Lingual split chisel versus lingual split bur	1	60	Mean Difference (IV, Fixed, 95% CI)	0.50 [0.08, 0.92]
3.4.2 Ultrasound versus bur	1	26	Mean Difference (IV, Fixed, 95% CI)	‐0.20 [‐1.32, 0.92]
3.4.3 Lingual split (bur or chisel) versus simplified bone removal	1	90	Mean Difference (IV, Fixed, 95% CI)	‐0.15 [‐0.43, 0.13]
3.5 Mean pain at 24 hours (0‐to‐10 VAS)	5	111	Mean Difference (IV, Random, 95% CI)	‐1.93 [‐3.08, ‐0.77]
3.5.1 Piezoelectric surgery versus conventional	5	111	Mean Difference (IV, Random, 95% CI)	‐1.93 [‐3.08, ‐0.77]
3.6 Swelling (after 7 days)	2		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
3.6.1 Lingual split chisel versus lingual split bur	1	60	Mean Difference (IV, Fixed, 95% CI)	‐0.10 [‐0.33, 0.13]
3.6.2 Ultrasound versus bur	1	26	Mean Difference (IV, Fixed, 95% CI)	0.37 [0.20, 0.54]
3.6.3 Lingual split (bur or chisel) versus simplified bone removal	1	90	Mean Difference (IV, Fixed, 95% CI)	0.15 [‐0.01, 0.31]
3.7 Maximum mouth opening (after 7 days)	4	110	Mean Difference (IV, Random, 95% CI)	2.68 [0.54, 4.81]
3.7.1 Piezoelectric surgery versus conventional ‐ split‐mouth	4	110	Mean Difference (IV, Random, 95% CI)	2.68 [0.54, 4.81]
3.8 Maximum mouth opening (after 7 days)	1		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
3.8.1 Ultrasound versus bur	1	26	Mean Difference (IV, Fixed, 95% CI)	2.90 [‐0.27, 6.07]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4.1 Alveolar osteitis (7 days)	2		Risk Ratio (IV, Fixed, 95% CI)	Subtotals only
4.1.1 Mechanical versus manual surgical wound irrigation	1	99	Risk Ratio (IV, Fixed, 95% CI)	0.33 [0.01, 8.09]
4.1.2 High‐volume versus low‐volume wound irrigation	1	211	Risk Ratio (IV, Fixed, 95% CI)	0.52 [0.27, 1.02]
4.2 Wound infection (7 days)	2		Risk Ratio (IV, Fixed, 95% CI)	Subtotals only
4.2.1 Mechanical versus manual surgical wound irrigation	1	99	Risk Ratio (IV, Fixed, 95% CI)	0.50 [0.05, 5.43]
4.2.2 High‐volume versus low‐volume wound irrigation	1	211	Risk Ratio (IV, Fixed, 95% CI)	0.17 [0.02, 1.37]

Date	Event	Description
7 July 2020	New citation required and conclusions have changed	The addition of 27 studies has led to slight changes in our conclusions.
8 July 2019	New search has been performed	Search updated. This review is an update of the first review, which was published in July 2014. We have added two new authors: Wafa Kashbour (WK) and Neha Shah (NS).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
5.1 Alveolar osteitis (7 days)	3	375	Risk Ratio (IV, Fixed, 95% CI)	0.99 [0.41, 2.40]
5.2 Wound infection (7 days)	1	82	Risk Ratio (M‐H, Fixed, 95% CI)	4.77 [0.24, 96.34]
5.3 Adverse effects ‐ reactionary bleeding	1	82	Risk Ratio (M‐H, Fixed, 95% CI)	0.41 [0.11, 1.47]
5.4 Pain at 24 hours (0‐to‐10 VAS)	5	474	Mean Difference (IV, Random, 95% CI)	0.94 [0.50, 1.38]
5.5 Swelling (after 7 days)	7	557	Mean Difference (IV, Random, 95% CI)	0.33 [0.09, 0.57]
5.6 Maximum mouth opening (after 7 days)	4	274	Mean Difference (IV, Random, 95% CI)	‐0.29 [‐0.90, 0.32]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
6.1 Maximum mouth opening	1	30	Mean Difference (IV, Fixed, 95% CI)	3.50 [2.69, 4.31]
6.1.1 Fibrin sealant versus conventional suturing	1	30	Mean Difference (IV, Fixed, 95% CI)	3.50 [2.69, 4.31]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
7.1 Pain at 24 hours (0‐to‐10 VAS)	2	180	Mean Difference (IV, Fixed, 95% CI)	‐0.19 [‐0.49, 0.12]
7.2 Swelling at 7 days	5	203	Mean Difference (IV, Random, 95% CI)	‐0.90 [‐1.62, ‐0.19]
7.3 Maximum mouth opening at 7 days	4	234	Mean Difference (IV, Random, 95% CI)	3.11 [2.20, 4.02]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
8.1 Alveolar osteitis (7 days) split‐ mouth studies (OR/BB)	2	128	Odds Ratio (IV, Fixed, 95% CI)	0.39 [0.22, 0.67]
8.1.1 Platelet rich fibrin versus none	2	128	Odds Ratio (IV, Fixed, 95% CI)	0.39 [0.22, 0.67]
8.2 Mean pain at 24 hours (0‐to‐10 VAS)	3	116	Mean Difference (IV, Fixed, 95% CI)	‐0.13 [‐0.59, 0.34]
8.2.1 Platelet rich fibrin versus none	3	116	Mean Difference (IV, Fixed, 95% CI)	‐0.13 [‐0.59, 0.34]
8.3 Swelling at 7 days	2	86	Mean Difference (IV, Fixed, 95% CI)	0.11 [‐0.12, 0.35]
8.3.1 Platelet rich fibrin versus none	2	86	Mean Difference (IV, Fixed, 95% CI)	0.11 [‐0.12, 0.35]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
9.1 Swelling at day 7	1	30	Mean Difference (IV, Fixed, 95% CI)	‐0.18 [‐0.63, 0.27]
9.2 Maximum mouth opening at day 7	1	30	Mean Difference (IV, Fixed, 95% CI)	‐2.94 [‐8.20, 2.32]

*Study characteristics*
Methods	Study design: RCT (split‐mouth) Conducted in: Department of Oral Surgery, University Dental School, Cardiff, Wales, UK
Participants	Inclusion criteria: 52 consecutive healthy patients scheduled for surgery entered the trial after assessment with dental panoramic radiograph. All had similarly impacted bilateral lower third molars. Exclusion criteria: patients were excluded if they had pericoronitis in the 6 weeks before surgery, or if they were allergic to any of the drugs in the standard regimen Age: mean 22 years Number randomised: 52 Number evaluated: 52
Interventions	Lingual split with chisel versus bur for bone removal under general anaesthesia Group A (n = 52 teeth): lingual split with chisel for bone removal Group B (n = 52 teeth): lingual split with bur for bone removal Follow‐up: 4 weeks All procedures were carried out under general anaesthetic. 43/52 participants had maxillary third molars extracted in same session.
Outcomes	Questionnaire assessment of lingual and inferior alveolar nerve function, swelling and pain were measured by a 4‐point scale at 6 h, 24 h, 48 h, and 7 days after the procedure. Participants also asked to indicate which side they felt was more swollen at these intervals. Infection was assessed by the presence of dry sockets or purulence or both.
Notes	Sample size calculation: not reported Email sent to author (12 February 2003). Unpublished data supplied.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...the method for a particular side and the third molar removed first were selected randomly" After contacting author, method of randomisation disclosed as "nurse blindly selecting a piece of paper on which was written either 'left' or 'right' from a bag in which were placed equal numbers of pieces of paper with 'left' and 'right' written on them".
Allocation concealment (selection bias)	Low risk	The operator was blinded to the above randomisation procedure. Comment: allocation concealed
Blinding (performance bias and detection bias) patient	Low risk	Quote: "...the trial was single‐blind to the patient as far as the surgical method was concerned" Comment: as the procedures were carried out under general anaesthetic, it can be assumed that the participants were blinded to which side received which intervention
Blinding (performance bias and detection bias) assessor	Low risk	Outcome assessors (the participants) were blinded for pain, swelling, and sensory disturbances. "on day 7... the wounds were examined by an independent observer"
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts
Selective reporting (reporting bias)	Low risk	The author was unable to specify which group (and indeed which socket ‐ upper or lower) received an acute abscess, despite direct correspondence on the matter.
Other bias	Unclear risk	In 43 of the 52 participants, maxillary third molars were also extracted; however, we contacted the author, who assured us that none of these were surgical. Author notes: "higher complication rates might have been found if this information had been supplemented by clinical assessments", noting the limitations of subjective assessment

*Study characteristics*
Methods	Study design: RCT; split‐mouth/cross‐over Conducted in: Turkey
Participants	Inclusion criteria: each participant had fairly symmetrically positioned, bone retained asymptomatic and class III B surgical difficulty grade (scales of Pell–Gregory and Winter) mandibular third molars Exclusion criteria: patients with any systemic disease, pregnancy, poor oral hygiene, or aged Age: above 18 years Number randomised: 30 participants/60 teeth; 4‐week interval between the 2 surgeries
Interventions	Horizontal mattress suturing versus simple interrupted suturing Group A: (30 teeth) 3 simple interrupted sutures on 1 side Group B: (30 teeth) 2 horizontal mattress sutures on the other side (both achieving primary closure) Preoperatively: 0.2% chlorhexidine mouth rinse for 30 seconds. Then, 2 mL and 1 mL of articaine with 1:200,000 epinephrine were administered to sustain local anaesthesia of the inferior alveolar nerve and buccal nerve, respectively.
Outcomes	Pain (0‐to‐100‐millimetre VAS) Trismus (interincisal distance) Swelling (mean of 5 measurements)
Notes	"The recorded data were analysed using the Statistical Package for Social Sciences (version 23.0; SPSS, IBM Corp, Armonk, NY). The Shapiro–Wilk test was used to test the normal distribution of individual parameters. Non‐parametric distributed data (pain, trismus, and swelling) were tested with the Mann–Whitney U test for differences in parameters between the groups. Wound healing was evaluated with Pearson correlation test for assessment of statistically significant differences. A value of P < 0.05 was accepted as statistically significant." Sample size calculation: reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The type of suturing technique was randomly selected for each side" Comment: no further details are given on the method of randomisation
Allocation concealment (selection bias)	Unclear risk	Comment: no details are given on any attempts to conceal the allocations
Blinding (performance bias and detection bias) patient	Unclear risk	Comment: not described, and the participant consent process was also not discussed
Blinding (performance bias and detection bias) assessor	Unclear risk	Quote: "These data were collected by another surgeon" Comment: it is not specified if the other surgeon was blinded to the allocations
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts reported.
Selective reporting (reporting bias)	Low risk	All outcomes reported.
Other bias	Low risk	None identified

*Study characteristics*
Methods	Study design: split‐mouth RCT Conducted in: Jordan University Hospital, Amman, Jordan
Participants	Inclusion criteria: symmetrically impacted mandibular third molars, with comparable positioning and angulation, no acute local inflammation or pathology Exclusion criteria: systemic diseases, pregnancy, lactation, smokers, medications that would influence the surgical procedure or wound healing Age: mean 21.4 ± 2.3, 18 to 26 years Number randomised: 20 Number evaluated: 19
Interventions	Buccal envelope flap versus triangular flap Group A (n = 19 teeth): sulcular incision from first to second mandibular molar with distal incision along mandibular ramus Group B (n = 19 teeth): incision commenced distally from the mandibular ramus to the disto‐buccal aspect of the second molar, then a sulcular incision near mesio‐buccal edge of M2 was made extending to its distal surface, finally a relieving incision from disto‐buccal aspect of M2 curving forward into mandibular vestibule Follow‐up: 14 days, 2‐week interval between the 2 sides All procedures were carried out by the same surgeon, using the same instruments (rotary and irrigation devices and materials) under sedation with intravenous midazolam and local anaesthetic.
Outcomes	Pain (VAS 1 to 10), swelling, trismus, periodontal examination of adjacent M2, alveolar osteitis, wound infection at 2, 7, and 14 days
Notes	Sample size calculation: not reported Although alveolar osteitis was one of the outcome measures, no cases of postoperative infection or dry socket occurred in either group.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "...randomly assigned using electronic randomization tables with patients numbered according to the order in which they presented for surgery"
Allocation concealment (selection bias)	Unclear risk	Unclear who performed the allocation and whether it was concealed from operator
Blinding (performance bias and detection bias) patient	Unclear risk	Not mentioned
Blinding (performance bias and detection bias) assessor	High risk	Not mentioned; assessment probably performed by operator
Incomplete outcome data (attrition bias) All outcomes	Low risk	One randomised participant did not have second procedure. This is unlikely to have introduced bias.
Selective reporting (reporting bias)	Low risk	Planned outcomes reported in full.
Other bias	Low risk	No other sources of bias identified.

*Study characteristics*
Methods	Study design: RCT (parallel group) Conducted in: Versilia Hospital, Lido di Camaiore, Italy
Participants	Inclusion criteria: people referred for lower third molar extraction at Versilia Hospital who were systemically healthy Exclusion criteria: people with a history of systemic diseases that would contraindicate surgery, pregnant and lactating women, people in whom there was no need to raise the mucoperiosteal flap to remove the third molar, and people who smoked more than 10 cigarettes per day Age: mean 31.2 years Number randomised: 26 Number evaluated: 26
Interventions	Ultrasound versus rotary instruments for bone removal Group A (n = 13): surgical removal of lower third molar using ultrasonic bone surgery under local anaesthesia Group B (n = 13): surgical removal of lower third molar using traditional rotary instruments under local anaesthesia (Rotary instruments were used for sectioning of teeth where necessary.) All procedures performed under local anaesthetic. Follow‐up: at days 1, 3, 5, and 7
Outcomes	Surgical time (start of first incision to last suture) Pain (0‐to‐10 VAS) at days 1, 3, 5, and 7 Trismus (interincisal distance measured using callipers) at days 1, 3, 5, and 7 Cheek swelling (measured with a standard calliper from the lingual aspect of the midportion of the crown of the first mandibular molar to the tangent of the cheek's skin) at days 1, 3, 5, and 7
Notes	Sample size calculation: not reported At baseline (parallel groups only) groups were comparable with regard to type of impaction.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "An independent evaluator allocated the patients into the test and control groups according to a computer‐generated randomisation list"
Allocation concealment (selection bias)	Low risk	Allocation was performed by an independent evaluator.
Blinding (performance bias and detection bias) patient	Unclear risk	All surgery performed on participants under local anaesthetic only, therefore blinding not possible
Blinding (performance bias and detection bias) assessor	Unclear risk	Unclear who carried out the postoperative assessments
Incomplete outcome data (attrition bias) All outcomes	Low risk	All randomised participants evaluated.
Selective reporting (reporting bias)	Low risk	Pain, swelling, trismus, analgesic consumption planned and recorded.
Other bias	Low risk	Groups appeared to be similar at baseline.

PERMALINK

Surgical techniques for the removal of mandibular wisdom teeth

Edmund Bailey

Wafa Kashbour

Neha Shah

Helen V Worthington

Tara F Renton

Paul Coulthard

Abstract

Background

Objectives

Search methods

Selection criteria

Data collection and analysis

Main results

Authors' conclusions

Plain language summary

Summary of findings

Background

Description of the condition

Description of the intervention

Surgical flap design

Lingual nerve protection

Bone removal techniques

Wound irrigation techniques

Wound closure

Suturing techniques

Surgical drains

Use of autologous blood concentrates

Root retention techniques/coronectomy

How the intervention might work

Why it is important to do this review

Objectives

Methods

Criteria for considering studies for this review

Types of studies

Types of participants

Types of interventions

Types of outcome measures

Primary outcomes

Secondary outcomes

Search methods for identification of studies

Electronic searches

Searching other resources

Data collection and analysis

Selection of studies

Data extraction and management

Assessment of risk of bias in included studies

1.

2.

Overall risk of bias for each trial

Measures of treatment effect

Unit of analysis issues

Dealing with missing data

1. Unuseable published data related to pain at 24 hours.

2. Unuseable published data related to swelling at 7 days.

3. Unuseable published data related to maximum mouth opening at 7 days.

Assessment of heterogeneity

Assessment of reporting biases

Data synthesis

Subgroup analysis and investigation of heterogeneity

Sensitivity analysis

Summary of findings and assessment of the certainty of the evidence

Results

Description of studies

Results of the search

3.

Included studies

Characteristics of the trial setting and investigators

Characteristics of the participants

Characteristics of the interventions

1. Surgical flap type

Triangular flap versus envelope or modified envelope flap (11 trials)

'Long' and 'short' triangular flaps

Pedicle flap versus envelope flap (one trial)

Modified triangular flap versus alternative single incision flap (one trial)

Buccal comma‐shaped incision versus modified envelope flap (one trial)

2. Lingual nerve protection

Lingual nerve retractor versus no retractor (three trials)

Broad retractor versus conventional (Howarth) lingual flap retractor (one trial)

*Study characteristics*
Methods	Study design: parallel RCT Conducted in: India
Participants	Inclusion criteria: healthy patients above 20 years of age. Individuals having vertical, mesioangular, horizontal mandibular third molar impactions based on radiographic interpretation Exclusion criteria: patients with systemic disease that could influence healing, patients who do not provide consent, patients on antibiotics in the past 6 weeks or who require antibiotic prophylaxis before extraction, and patients who had acute local infection involving the impacted teeth Age: above 20 years old Number evaluated: 30 participants/30 teeth
Interventions	Piezoelectric versus rotary osteotomy technique for bone removal Group I: piezoelectric osteotomy technique (frequency of 25 to 29 kHz with a microvibration of 60 to 200 mm/s was used with a boosted working mode) Group II: rotary osteotomy technique (35,000 rpm) All participants underwent surgical removal of impacted mandibular third molars under 2% lidocaine with 1:200,000 adrenaline, with inferior alveolar, lingual, and long buccal nerve blocks administered. Postoperatively, all participants received amoxicillin 500 mg 3 times a day and diclofenac sodium 50 mg 3 times a day for 3 days. Postoperative instructions were given, and the sutures were removed on the seventh day.
Outcomes	Pain VAS (no pain to severe pain) Trismus (interincisal distance) Swelling Other outcomes: time taken for the procedure; patient satisfaction
Notes	Descriptive analysis was done. Results are explained as mean ± standard deviation (min to max) and also as number (%): 5% was considered as level of significance with 95% confidence interval. Quantitative data were analysed using unpaired t‐test, and qualitative data were analysed using Fisher’s exact test. Sample size calculation: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "individuals were randomly allocated to study groups" Comment: method of randomisation was not described
Allocation concealment (selection bias)	Unclear risk	Comment: methods of concealment were not discussed
Blinding (performance bias and detection bias) patient	Unclear risk	Comment: it is unclear if the participants were blinded as they consented to the procedure
Blinding (performance bias and detection bias) assessor	Unclear risk	Comment: blinding is not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	There were no reported dropouts.
Selective reporting (reporting bias)	Low risk	All of the outcomes were reported.
Other bias	High risk	Quote "to standardize our results, it was conducted on 30 male individuals having their age ranging from 25 to 33 years, in order to remove the gender factor that may play a role in postoperative complications due to hormonal changes that may occur in females" Comment: this study only included males, therefore the results are limited to this study population

*Study characteristics*
Methods	Study design: RCT parallel group Conducted in: Department of Oral and Maxillofacial Surgery, National Hospital, Abuja, Nigeria Number of centres: 1 Recruitment period: not stated
Participants	Inclusion criteria: patients referred for extraction of 1 or 2 impacted mandibular third molars Exclusion criteria: patients with acute pericoronal infection, systemic diseases, or bleeding disorder, patients receiving steroid therapy or contraceptives, and smokers were excluded. Patients whose extraction procedure took more than 35 minutes were also excluded. Number randomised: unclear Number evaluated: 82
Interventions	Partial versus complete wound closure Group A (n = 40): partial wound closure was achieved using 4 interrupted sutures leaving a window communicating with the oral cavity Group B (n = 42): complete wound closure was achieved using 5 interrupted sutures that sealed off communication with the oral cavity All procedures done under local anaesthetic by the same surgeon. All participants received pre‐emptive antibiotics (amoxicillin and metronidazole) for 5 days and diclofenac for pain and inflammation for 3 days.
Outcomes	Pain (VAS 0 to 10) reported daily for 7 days. Maximal interincisal distance (as % of baseline value) and swelling (difference from baseline) were evaluated on days 2, 5, and 7. Numbers of postoperative complications (dry socket, infection, and secondary haemorrhage) were also noted.
Notes	Sample size calculation: not reported E‐mail sent 12 March 2012 requesting further information about the methods used. Reply received 21 March 2012 with unpublished data.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "randomly allocated" Comment: allocated by drawing lots to either partial or total (e‐mail correspondence)
Allocation concealment (selection bias)	Low risk	A paper was drawn by the assistant and shown to the surgeon prior to suturing (e‐mail correspondence).
Blinding (performance bias and detection bias) patient	Unclear risk	Not mentioned
Blinding (performance bias and detection bias) assessor	Unclear risk	Assessment done using a "clean proforma", but it is possible that the assessor knew which group the participant was in.
Incomplete outcome data (attrition bias) All outcomes	Low risk	90 patients were screened for inclusion but unclear how many were randomised. Patients were excluded when the procedure took more than 35 minutes (n = 3). 8 patients did not return for follow‐up assessment, 5 and 3 in each group.
Selective reporting (reporting bias)	Low risk	Planned outcomes of pain, trismus, swelling, and complications reported.
Other bias	Low risk	No other sources of bias identified. This study excluded patients whose surgeries exceeded 35 minutes; the reason for this was not explained.

*Study characteristics*
Methods	Study design: parallel‐group RCT Conducted in: Brazil (but researchers based in Italy)
Participants	Inclusion criteria: patients between the ages of 18 and 41 requiring extraction of mandibular third molars. Those with moderate impaction mesio‐angularly with a tilt degree more than 25° in relation to the second molar. Only impacted third molars with distil periodontal defects at the second molar with PPD ≥ 7 mm and CAL ≥ 6 mm were selected. Exclusion criteria: systemic disease, pregnancy, smoking, and medication (unspecified) Age: 18 to 45 years Number randomised: 45 Number evaluated: 45
Interventions	Laskin triangular flap versus Thibault and Parant modified envelope flap versus Laskin envelope flap Group A (n = 15): Laskin triangular flap Group B (n = 15): Thibault and Parant modified envelope flap Group C (n = 15): Laskin envelope flap All participants had a preoperative dental hygiene check, and procedures were performed under local anaesthetic. All participants given 1 g amoxicillin + sulbactam preoperation, and all used CHX mouthwash pre‐ and postoperation.
Outcomes	Short‐term complications (pain swelling and infection) and PPD and CAL at 3, 6, 12, and 24 months
Notes	Sample size calculation: not reported Gaetano Isola provided additional data on short‐term complications by e‐mail 7 March 2012.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: whilst the technique used in each case was randomly selected, the authors do not specify any further details on this allocation process
Allocation concealment (selection bias)	Unclear risk	Comment: no details of the allocation concealment provided
Blinding (performance bias and detection bias) patient	Unclear risk	Quote: "A clot of PRF, which was produced in a 10 ml tube, was enough to fill the socket of each patient." Comment: it is unclear if all participants had blood samples taken, or whether samples were only taken from participants in the PRF group. This could be a source of bias.
Blinding (performance bias and detection bias) assessor	Low risk	Quote: "all measurements were assessed by the same person (not the operating surgeon)" Comment: the assessor was blind to the allocations
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: all randomised participants were included until the end of the study
Selective reporting (reporting bias)	Low risk	All planned outcomes were reported on.
Other bias	High risk	Comment: some participants had unilateral extractions, whilst others had bilateral extractions. This could have influenced outcomes such as pain perception and trismus.

*Study characteristics*
Methods	Study design: RCT split‐mouth Conducted in: Pernambuco, Brazil Number of centres: 1 Recruitment period: not stated
Participants	Inclusion criteria: patients aged 14 to 30 years, with bilateral impacted third molars in similar positions on each side of the mouth Exclusion criteria: patients using medications that could interfere with healing or those with systemic disease Number invited: 5 patients underwent surgery "with the purpose of calibration", and a further 12 were excluded because they "proved to be unsuitable" Number randomised: 53 Number evaluated: 53
Interventions	Drain versus no drain Group A (n = 53): 1 side of the mouth, chosen at random, had a silicon tube drain inserted into the buccal fold. Drain in situ for 4 days Group B (n = 53): on the opposing side the wound was sutured with no drain All participants received preoperative antibiotic prophylaxis (amoxicillin) and postoperative cetoprophen for 4 days. All procedures performed under local anaesthesia.
Outcomes	Pain (0‐to‐10 VAS), maximal mouth opening, swelling (% of preoperative) on postoperative days 1, 3, 7, and 15
Notes	Sample size calculation: not reported E‐mail sent to Dr Vasconcelos at belmiroc@terra.com.br on 6 March 2012 requesting further information. No reply received.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The choice of treatment "was made randomly".
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding (performance bias and detection bias) patient	Unclear risk	Not mentioned and probably not possible
Blinding (performance bias and detection bias) assessor	High risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	All 53 participants were evaluated.
Selective reporting (reporting bias)	Low risk	Planned outcomes of pain, swelling, and trismus reported.
Other bias	Low risk	No other sources of bias identified.

*Study characteristics*
Methods	Study design: parallel‐group, single‐blind RCT Conducted in: oral surgery department of University of Nigeria Teaching Hospital, Enugu, Nigeria
Participants	Inclusion criteria: patients who were willing to come for their follow‐up appointments, who were free from pain or any other inflammatory symptoms (swelling, hyperaemia, TMD), had impacted lower wisdom teeth, were not on medication that could interfere with healing, and did not smoke or have any systemic disease Exclusion criteria: pregnant or lactating females were excluded from the study Number randomised: 100 Number evaluated: 100
Interventions	Rubber tube (Penrose) drain versus no drain Group A (n = 50): sutures plus Penrose rubber drain placement for 72 h Group B (n = 50): sutures only postoperatively All participants received 2 g amoxicillin preoperatively, and procedures were performed under local anaesthesia. Follow‐up: 24 h, 72 h, and 5 days
Outcomes	Pain (0‐to‐10 VAS), swelling (horizontal and vertical guide with tape and reference points), and trismus (interincisal callipers). Evaluated at 24 h, 72 h, and 5 days postoperatively
Notes	Sample size calculation: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...a prospective, randomised, single‐blind experimental study was undertaken" Comment: method of sequence generation not described
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding (performance bias and detection bias) patient	High risk	Participants could not have been blinded to the treatment group they were in, as they would have been aware of the presence of the Penrose rubber drain in their mouths. This is evidenced in the photographs.
Blinding (performance bias and detection bias) assessor	Unclear risk	There is no mention of assessor blinding other than "a prospective, randomised, single‐blind experimental study was undertaken". However, it is not clear to whom this single‐blinding refers.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals
Selective reporting (reporting bias)	Low risk	All planned outcomes reported on.
Other bias	Unclear risk	The study accepted all impactions, but there was no report of measures to account for possible differing degrees of difficulty with the extractions. Whilst appropriate randomisation should result in groups with similar proportions of high‐risk patients, no baseline characteristics were reported in this trial. It is unclear whether these biases were avoided.

*Study characteristics*
Methods	Study design: RCT (parallel) Conducted in: Eastman Dental Center, New York, USA
Participants	Inclusion criteria: unilateral wisdom tooth needing extraction Exclusion criteria: patients with clinical signs of pericoronitis, or those whose surgery took longer than 20 minutes from the first incision Number randomised: 21 Number evaluated: 21
Interventions	Gauze drain versus no drain Group A (n = 11): postextraction placement of a Vaseline‐coated gauze drain partially submerged into the socket, sutured in place Group B (n = 10): postextraction removal of a wedge of tissue distal to the second molar before closure Surgery was performed under local anaesthetic. Follow‐up: 2 and 7 days
Outcomes	Pain (0‐to‐10 VAS), swelling (examiner VAS, and comparisons with preoperative calliper measurements), trismus (interincisal distance), dry socket
Notes	Sample size calculation: not reported Baseline characteristics of groups not reported. Letter sent to author (May 2003). Reply that no additional data were available
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...made on a randomised basis by an individual other than the surgeon performing the procedure"; "the operator did not know whether a drain would be inserted until the time of closure"
Allocation concealment (selection bias)	Low risk	Quote: "The decision on whether a drain should be inserted was made on a randomised basis by an individual other than the surgeon performing the procedure" Comment: unclear if was this concealed from the surgeon
Blinding (performance bias and detection bias) patient	Unclear risk	Quote: "...the patients were not informed of the potential advantages or disadvantages of the drain", though participants still likely to detect presence of drain in operation site, therefore blinding of participants not possible
Blinding (performance bias and detection bias) assessor	Unclear risk	Subsequently, pain assessments by the participants using a VAS were not blinded either: "...the patients were routinely examined by an examiner who was not the surgeon and not aware of the treatment given", therefore assessor was blinded for swelling, trismus, and dry socket. Unclear when drain was removed and whether examiner could have determined whether a drain had been placed
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No withdrawals mentioned, but numbers evaluated not stated. Only means per group were reported.
Selective reporting (reporting bias)	Low risk	Although the authors only mention dry socket in the results section, it should be noted that the investigators were looking for dry socket at the outset, regardless of the fact that there was no incidence of this outcome in either group.
Other bias	Unclear risk	An exclusion criterion precludes any cases that took longer than 20 minutes from the first incision to removal of the tooth. The authors do not mention whether more participants were included in the study beforehand but subsequently had to withdraw because of lengthy surgery; these participants were not accounted for in the text, if indeed there were any.

*Study characteristics*
Methods	Study design: double‐blinded, randomised clinical trial, split‐mouth technique Conducted in: Iran
Participants	Inclusion criteria: 18 to 35 years of age, have American Society of Anesthesiologists physical status I or II; have bilateral mandibular third molars; have the same difficulty level of bilateral third molars based on the Pederson classification Exclusion criteria: pericoronitis of the mandibular third molar(s), received antibiotic regimen during the previous 2 weeks, had a smoking habit, was lactating or pregnant, was using oral contraceptives, had any lesions found on the panoramic radiograph, had any complications during extractions, or had received more than 2 anaesthetic cartridges during surgery Number randomised: 85 Number evaluated: 78 (bilateral impacted teeth) (33 male and 45 female; mean age 25.09 years)
Interventions	Comparison: placement of PRF versus none in the extracted socket PRF was placed in 1 of the sockets, and the other socket received no treatment. Group A intervention (n = 78) Group B control (n = 78) Note: postoperative prescriptions were amoxicillin (500 mg 3 times daily, n = 21) and paracetamol (500 mg 3 times daily, for a maximum of 3 days)
Outcomes	Alveolar osteitis at days 2 and 7 Based on the c2 analysis, the frequency of alveolar osteitis had a significant association with the application of PRF. Sockets that received PRF after extraction had a statistically significant decreased risk of developing alveolar osteitis compared with non‐PRF sockets (risk ratio 0.44, 95% confidence interval 0.148 to 0.989; P = 0.042).
Notes	Descriptive statistics (frequency, mean, and standard deviation) were determined for each variable. Data analysis was performed with c2 and t tests using SPSS 11.5 (SPSS Inc, Chicago, IL), with a confidence interval of 95%. Sample size calculation: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "PRF was randomly inserted into one of the sockets" Comment: coin toss technique was used to decide which side received intervention or control
Allocation concealment (selection bias)	Unclear risk	Comment: not clear whether randomisation of participants was done by someone different from the person who recruited participants
Blinding (performance bias and detection bias) patient	Unclear risk	Quote: an operator blinded to the surgery performed the PRF insertion and suturing. Hence, the participants and the surgeon were blind to the side in which PRF had been inserted. Comment: all participants had blood taken and PRF placed. However, a new surgeon coming in to work on one side of the mouth would reveal which side the PRF went into.
Blinding (performance bias and detection bias) assessor	Low risk	Quote: "the randomisation data were kept unknown by another investigator until the end of the study"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "eighty‐five patients met the inclusion criteria and entered the study; however, 6 patients received more than 2 anesthetic cartridges and 1 female patient had used oral contraceptives during the first postoperative week (as emergency birth control). Therefore, 78 patients (33 male and 45 female; mean age, 25.09 Æ 4.25 yr) completed the study" Comment: 85 participants were recruited, and the outcomes of 78 were reported. Justification for this was provided.
Selective reporting (reporting bias)	Low risk	Planned outcomes were reported.
Other bias	Low risk	No other sources of bias identified.

*Study characteristics*
Methods	Study design: RCT split‐mouth method Conducted in: India
Participants	Inclusion criteria: over 18 years of age; ASA 1 (American Society of Anesthesiology) patient with no systemic diseases or conditions; patient requiring surgical removal of bilaterally impacted mandibular third molars; bilateral impactions with a relatively similar classification and degree of difficulty, based on the Pell and Gregory system; patient agreement to the surgical procedure and clinical trial, providing informed consent Exclusion criteria: presence of systemic diseases; presence of bleeding disorders; patients on antiplatelet or anticoagulant therapy; pregnant or nursing mothers; patients with a known history of allergy to lidocaine; patient not consenting to the procedure or study Number randomised: 30 participants/60 teeth Number evaluated: 30 participants
Interventions	Fibrin sealant versus conventional suturing using 3–0 black silk Group A (n = 30): fibrin sealant Group B (n = 30): primary closure by suturing Using a split‐mouth study design, wound closure following extraction was done using fibrin sealant on the study side and primary closure suturing on the control side. Procedure was carried out under local anaesthetic.
Outcomes	Primary outcome measures were (1) the time taken to achieve wound closure and haemostasis and (2) postoperative mouth opening, pain, and swelling.
Notes	As this was a split‐mouth study, the paired t‐test was used to compare the mean values between the control and experimental groups. The paired t‐test was also applied for comparisons between time points. The level of significance was fixed as a = 0.05 (2‐ tailed). IBM SPSS Statistics for Windows, version 20.0 (IBM Corp, Armonk, NY, USA) was used for the data analysis. Sample size calculation: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The patient pool was sequentially numbered 1–30. Lots were drawn, one for each patient, from sealed envelopes that contained combinations of the agent (fibrin sealant/suturing) and the side to be operated (right/left)" Comment: sequentially numbered, sealed envelopes were used
Allocation concealment (selection bias)	Low risk	Comment: sealed envelopes were used
Blinding (performance bias and detection bias) patient	Unclear risk	Comment: it is unclear if participants were blinded to the procedure. This is not stated specifically; it is possible the participant would be aware of the presence (or absence) of sutures in mouth.
Blinding (performance bias and detection bias) assessor	Unclear risk	Comment: unclear if the assessor was different to the operating surgeon
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "no patients discontinued the trial or were lost to follow‐up" Comment: all participants were analysed
Selective reporting (reporting bias)	Low risk	All planned outcomes were reported.
Other bias	Unclear risk	This was a cross‐over trial. The order of the receiving of treatments was randomised. There is potential bias from a carry‐over effect; carry‐over effect was not evaluated.

*Study characteristics*
Methods	Study design: a randomised single‐blind clinical trial, parallel Conducted in: Turkey
Participants	Inclusion criteria: patients with no history of medical illness or medication that could influence the course of postoperative wound healing or alter their wound healing after surgery were selected Exclusion criteria: patients were excluded from randomisation if they had a pre‐existing abscess or cellulitis, acute pericoronitis, or pre‐existing conditions associated with their third molars. Those who required antibiotics for some other reason (such as prophylaxis for endocarditis) were also excluded, as were those who had been given radiotherapy. Immunocompromised patients, pregnant women, those already taking antimicrobials, and those with systemic diseases, such as diabetes, cancer, or renal failure, were excluded. Age: 18 to 29 Number randomised: 80 Number evaluated: 80
Interventions	Envelope flap type versus modified triangular flap type Group A (40 participants): envelope flap type Group B (40 participants): modified triangular flap type All operations were done under local anaesthesia (inferior alveolar block, 2 mL 2% lidocaine with 1:80,000 epinephrine). A primary wound closure was carried out in all cases. All participants were given amoxicillin (500 mg/8 h) for 7 days and diclofenac potassium (50 mg/12 h) for pain after surgery. Postoperative instructions for the participants included soft diet and oral hygiene with 0.2% chlorhexidine mouth rinse. Sutures were removed 7 days after surgery.
Outcomes	Primary outcome: any postoperative complication; alveolar osteitis classified as present or absent Secondary outcomes: postoperative side effects (including pain, swelling, and trismus assessed during the postoperative time periods) pain (0‐to‐10 VAS), daily for 7 days swelling (subjective and objective measurements). Subjective assessment was made of swelling on the second and seventh days after extraction, based on a 4‐point scale: 1 no swelling; 2 mild swelling; 3 moderate swelling; and 4 severe swelling. Objective measurement: 2 distances were measured by a modification of a tape‐measuring method on the second and seventh days after extraction. These 2 measurements were made between 3 reference points: tragus, pogonion, and the corner of the mouth. The preoperative sum of the 2 measurements was considered to be the baseline. trismus: maximum mouth opening was measured before surgery and again on the second and seventh days after extraction
Notes	This study was mentioned in the previous review update, but was not published at that time. Sample size calculation: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "investigators designed and implemented a randomized single‐blind clinical trial. The flap design was randomly assigned for each patient" Comment: unclear how the participants were recruited and randomised
Allocation concealment (selection bias)	Unclear risk	Comment: concealment approaches were not described
Blinding (performance bias and detection bias) patient	Low risk	Comment: unclear as it was not described. However, it is unlikely that the participant would have known which flap they had unless they were explicitly told.
Blinding (performance bias and detection bias) assessor	Low risk	Quote: "The surgeon that had operated on the patients was never involved in the preoperative or postoperative assessment" Comment: assessor blinding was appropriate
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: outcomes were reported for all participants (n = 80). 100 participants were initially recruited; the reason for the final number (80) was explained appropriately (they did not meet the inclusion criteria).
Selective reporting (reporting bias)	Low risk	All intended outcomes were reported.
Other bias	Low risk	No other sources of bias identified.

*Study characteristics*
Methods	Study design: prospective RCT, single‐blind, parallel Conducted in: Turkey
Participants	Inclusion criteria: bilateral vertically symmetrical impacted third molars on panoramic radiographs. All impacted mandibular third molars had to be in a comparable position bilaterally and carry the same degree of surgical difficulty requiring the same technique. All teeth were fully covered by mucosa and bone. All participants were non‐smokers, periodontally healthy, and well‐educated about their daily oral hygiene. Exclusion criteria: history of medical illness or medication that could influence the course of postoperative wound healing or alter wound healing after extraction. Also excluded were patients who had any pathological lesion in the area of the impacted third molar. The periods between the incision and insertion of the last suture were recorded, and if the operating time differed by more than 5 minutes between the 2 sides, the patient was withdrawn from the study. Age: 18 to 29 years Number randomised: 40 Number evaluated: 40
Interventions	Effect of tube drainage versus conventional suturing on postoperative discomfort after extraction Group experimental: a tube drain (n = 40 teeth): an infant feeding tube 3 cm long and 2.67 mm in diameter (8 Ch) (Bıc¸akcılar, Istanbul, Turkey) was inserted in the buccal incision line between the first and second molar. The tube drain was sutured to the vestibular mucosa to prevent it from coming out or becoming lost in the wound. Group B control: no drain (n = 40): a 3‐cornered mucoperiosteal flap was raised to expose the third molar. Bone was removed under constant irrigation with sterile 0.9% saline on the occlusal and buccal aspect of the third molar with rotating instruments of diminishing size. After extraction, potential nests of the dental follicle were removed. Primary wound closure with atraumatic silk sutures without tension (Medico Co. Ltd, China) was used on the side that had no drain.
Outcomes	Pain (VAS) from zero (no pain) to 10 (worst pain imaginable) daily for 7 days Degree of swelling (mm) at days 2 and 7 Maximum mouth opening at days 2 and 7 A quality of life questionnaire was used; all participants returned the questionnaires on day 7
Notes	Sample size calculation: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "groups by random selection in a cross‐over pattern. The trial was randomised, prospective, and single‐blind." Comment: method of randomisation not described
Allocation concealment (selection bias)	Unclear risk	Comment: concealment methods not described
Blinding (performance bias and detection bias) patient	High risk	Comment: "a single blinded study". It is unlikely that participants could be blinded with this study design.
Blinding (performance bias and detection bias) assessor	Low risk	Quote: "The surgeon who had operated on the patients was not involved in either the preoperative or the postoperative assessment"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcomes reported for all participants.
Selective reporting (reporting bias)	Low risk	All outcomes reported.
Other bias	Unclear risk	Carry‐over effect not evaluated.