“Effects of flap modification on third molar extraction outcomes”-A randomised split mouth study

Abstract

Aim

The main purpose of this experimental study was to compare whether modifications in flap design influence the post-operative outcome of third molar surgeries.

Materials and methods

This study was designed as a randomized, single-blinded,split-mouth cross-over comparative study. The predictor variables were the flap type; Conventional Ward's was used to expose the tooth with a difference in the anterior release incision between the groups.Oblique anterior releasing incision and vertical anterior releasing incisions were used for the control and study group respectively.The primary outcome variables were pain measured using VAS (Visual analogue scale), swelling in mm; mouth opening measured in mm, periodontal probing depth in a mm, wound healing by modified Landry's score and surgical accessibility. Statistical significance was set at 5% (α = 0.05).

Result

Twenty five patients with bilateral, mirror-image impacted mandibular third molars participated in the study.The study group was associated with moderate swelling that was not statistically significant. .The outcome variables i.e. pain, wound healing, mouth opening, and periodontal pocket depth had no statistical difference on comparing the two groups. In terms of accessibility, the control group was found to be better with the statistical significance of p = 0.00184.

Conclusion

Modifying conventional Ward's design influences the degree of swelling and surgical accessibility. Vertical anterior releasing incision in conventional Ward's has no advantage over conventional Ward's with oblique anterior releasing incision.

1. Introduction

Surgical removal of the mandibular third molar has become a common procedure considering the evolutionary pattern. Often large flaps are needed to attain good visibility to the surgical site that will facilitate the adequate ostectomy for odentectomy. A large volume of literature on the flap designs that have been published have assessed the flap designs based on subjective outcomes of pain, swelling, and trismus.1, 2, 3, 4 Apart from this, considering that the normal tissue is being used as a leverage to access the pathology, it is essential that good healing with restoration of normal health of the flap and the adjacent structures is restored without disrupting the normal periodontal health of the adjacent teeth. Considering the aforesaid factors, we hypothesize that modifying the anterior limb of the conventional Ward's incision can provide better access to the surgical site without interfering with the normal periodontal health of the second molar. An oblique anterior release incision was primarily designed to have a broad base that will provide adequate vascularity to the flap.^5,6 A straight release incision is adequate considering the posterior limb extends onto the external oblique ridge which provides a broad base irrespective of anterior release. Apart from this, the extensive vascular supply of the face prevents any vascular compromise even with the application of a straight anterior release.^7,8 Closure of the surgical site with a anterior oblique release leads to displace the tissues in the buccal vestibule that can interfere with the healing distal to second molar leading to post-operative periodontal pocket formation.⁹ This can be effectively avoided by using a straight anterior release incision.

Considering the aforesaid factors, we aimed to compare the efficacy of modified wards incision with the conventional wards incision for surgical removal of mandibular 3rd molar.

2. Materials and methods

2.1. Study design and sample

A split-mouth experimental design was used, with both side of the mandible being randomly allocated to one of two flap design groups. The criteria for inclusion were- patients who required removal of infected or prophylactic teeth having bilateral mirror image impacted mandible third molars replicating the same angulation, class and position according to Pell and Gregory classification¹⁰ were included in the study. (Table 1) The criteria for exclusion were, patients with the history of use of alcohol/tobacco or who had co- morbid diseases like diabetes, renal failure, epileptic, cancer, endocarditis, immune compromised, pregnant women, patients who had prophylactic radiotherapy and who were extremely uncooperative were excluded from the study. The flap design compared in the study incorporated vertical anterior release incision and oblique anterior release in the same conventional Wards incision. This study was done in accordance with Consolidated Standards of Reporting Trials (CONSORT) statement after being reviewed and approved by Institutional Review Board for ethical clearance [IRB Approval: SRMDC/IRB/2016/MDS/NO.403].

Table 1.

Ease of accessibility based on Type, Class & Position of impacted teeth.

Type of impaction/class/position [number]	Accessibility	Study N = 25	Control N = 25
Mesioangular/I/A [2]	Easy	2	2
	Moderate
	Difficult
Mesioangular/II/A [1]	Easy		1
	Moderate	1
	Difficult
Mesioangular/II/B [4]	Easy	2	2
	Moderate	2	2
	Difficult
Distoangular/I/A [6]	Easy	2	6
	Moderate	3
	Difficult	1
Vertical/II/A [4]	Easy	4	4
	Moderate
	Difficult
Vertical/II/B [1]	Easy		1
	Moderate	1
	Difficult
Horizontal/I/A [4]	Easy		2
	Moderate	2	2
	Difficult	2
Horizontal/ II/A [1]	Easy		1
	Moderate
	Difficult	1
Horizontal/II/B [1]	Easy		1
	Moderate
	Difficult	1
Horizontal/II/C [1]	Easy		1
	Moderate
	Difficult	1

Predictor variables: Oblique anterior release in A Conventional Ward's: The incision extending obliquely from the distobuccal line angle of the second molar with a buccal sulcular incision following the facial surface of the impacted third molar on to the external oblique ridge. The incision in to measuring ~8–10 mm. (Fig. 1, Fig. 2) Vertical anterior release in conventional Ward's: A vertical incision made along the distofacial line angle of the second molar with a buccal sulcular incision along the buccal aspect of the impacted third molar to the external oblique ridge. The incision approximately measures ~8–10 mm. (Fig. 3, Fig. 4) Variables used to assess the primary outcome of the flap designs were pain, swelling, mouth-opening, wound-healing, periodontal probing depth, and accessibility. A single investigator assessing the patients postoperatively was blinded. Patients were enrolled in the study only after obtaining surgical consent, and the procedure was carried under local anaesthesia. Radiographic assessment of the wisdom teeth was carried using Orthopantomogram (OPG) and Pederson's difficulty index score was recorded preoperatively. Pain was graded by the patient in a 10 cm visual analogue scale (VAS) of 0–10. Swelling was measured objectively using 3 reference-point measured using a measuring tape along the following facial references, I - The lateral corner of the eye to the angle of the mandible, II - Tragus to the corner of mouth, III-Tragus to pogonion; mouth opening was measured pre and post-surgery by the investigator between the maxillary and mandibular central incisors, the maximum inter- incisal distance with a ruler. These measurements were graded twice and recorded. Wound healing was scored using modified Landry's wound healing criteria¹¹; periodontal probing depth was measured from distal to the second molar was calibrated using William's periodontal probe. Apart from these normal routine parameters, surgical accessibility was assessed by a single operating surgeon as easy, moderate, and difficult based on the exposure, and the ease of reflection. Bilateral impaction surgery was planned with a time interval of 1 month following the previous surgery. Post-surgical assessment of pain, swelling, mouth opening, and wound healing and periodontal probing depth were evaluated and tabulated on day 1, day 3, day 7, and 1 month respectively.

Fig. 1.

Oblique anterior release in conventional wards.

Fig. 2.

Closure of oblique anterior release incision in conventional Ward's.

Fig. 3.

Vertical anterior release in conventional Ward's.

Fig. 4.

Closure of vertical anterior release incision in conventional Ward's.

3. Data collection and methods

Data was collected regarding the age, sex, and type of impaction of each subject for each third molar extracted. We recorded age in years at the time of the interview (continuous variable) Pre-operative mouth opening; periodontal depth and swelling was recorded before the procedure. Operative variables like accessibility and type of incision design was recorded.

4. Statistical analysis

The sample size was calculated using the software GPower version 3.1.9.2. The normality tests Kolmogorov-Smirnov and Shapiro-Wilks test results revealed that variables follow normal distribution. Paired Samples T-Test was applied to compare mean values between time points and to analyse the mean values between the groups. We recorded the data of the patients and added to the database SPSS (IBM SPSS Statistics for Windows, Version 23.0, and Armonk, NY: IBM Corp. Released 2015). Significance level was set at 5% (α = 0.05).

5. Results

This prospective randomized clinical split-mouth study conducted at the Department of Oral and Maxillofacial Surgery comprised a sample of 25 healthy patients (12 males, 13 females). Patients were 18–35 years old with an average age of 26.5 years. There was a significant difference evident on the VAS score (pain) on the seventh post-operative day between the control, and the study groups. (p = 0.003). According to the statistical test used to assess maximum interincisal distance (mouth opening) showed a statistical significance on post-operative day one and day three were evident, but the differences between the recording times (day 1-1 month, day 3-1 month, and day 7–1 month) were not significant. Wound healing calibrated using modified Landry's score did not prove any significance between the incision designs. Periodontal probing depth was measured from distal of second molar using William's periodontal probe. No statistical significance on measuring periodontal depth was noted/observed in both the incision groups. (p = 0.110). The statistical values for pain, mouth opening, periodontal probing depth and wound healing is illustrated in Table 2. On the 3rd postoperative day (7.06785) and 1-month postoperative day (6.43336), the facial swelling was significantly lesser compared with vertical anterior release in conventional Wards. (Table 3). Based on the surgeon's score for surgical accessibility 40.0% of 10 cases were easy, 36.0% of cases had moderate access, and 24.0% cases reported with difficulty to access in the study group (Fig. 5). In contrast to the study side, the control group exhibited high statistical significance with 21 (84.0%) cases having a easy access, 4 being moderate and none without a difficult approach (p = 0.00184) (Table 4) (Fig. 6).

Table 2.

Comparison of parameters between control group and study group.

Variables	Assessment Group (mean)		Assessment group (SD)			t-value	p-value
	Study group	Control group	Study group	Control group
Pain
Day 1	2.80	3.52	1.354		1.503	1.790	0.086
Day 3	2.20	2.48	1.155		1.194	0.942	0.356
Day 7	0.84	1.32	1.473		1.557	3.361	0.003
1st month	0.0	0.0	0.0		0.0	–	–
Mouth Opening
Day 1	29.60	28.64	11.339		9.036	0.449	0.657
Day 3	32.56	32.68	7.885		7.111	0.077	0.940
Day 7	39.68	37.72	7.586		1.557	1.301	0.205
1st month	45.32	44.40	5.706		6.178	0.693	0.495
Wound Healing
Day 1	4.48	4.96	0.554		0.200	1.000	0.327
Day 3	4.76	5.00	0.879		0.000	1.365	0.185
Day 7	4.92	5.00	0.000		0.000	1.000	0.327
1st month	0.00	0.00	0.000		0.000	0.000	0.000
Periodontal probing depth
1st month	4.56	4.80	0.507		0.500	−1.659	0.110

Table 3.

Comparison of facial swelling between study and control groups.

Time	Group	Mean swelling	Std. Deviation	p-value
Day 0	Study	121.4267	7.99046	0.006
	Control	124.3067	6.43336
Day 1	Study	127.4000	7.93317	0.071
	Control	130.0667	7.43988
Day 3	Study	123.0800	8.46905	0.005
	Control	127.1467	7.06785
Day 7	Study	121.1200	9.54127	0.064
	Control	124.1733	6.57515
Day 30	Study	121.4267	7.99046	0.006
	Control	124.3067	6.43336
Day 0 - Day 1	Study	−5.9733	4.18542	0.853
	Control	−5.7600	4.13714
Day 0 - Day 3	Study	−1.6533	4.49741	0.159
	Control	−2.8400	4.00592
Day 0 - Day 7	Study	.3067	4.34392	0.878
	Control	.1333	3.21455
Day 0 - Day 30	Study	.0000	.00000	–
	Control	.0000	.00000
Day 1 - Day 3	Study	4.3200	4.91641	0.165
	Control	2.9200	3.33372
Day 1 - Day 7	Study	6.2800	4.48731	0.783
	Control	5.8933	4.48528
Day 1 - Day 30	Study	5.9733	4.18542	0.853
	Control	5.7600	4.13714
Day 3 - Day 7	Study	1.9600	5.17322	0.440
	Control	2.9733	4.61471
Day 3 - Day 30	Study	1.6533	4.49741	0.159
	Control	2.8400	4.00592
Day 7 - Day 30	Study	-.3067	4.34392	0.878
	Control	-.1333	3.21455

Fig. 5.

Surgical accessibility of vertical anterior release incision in conventional Ward's.

Table 4.

Retrospective review of studies on flap design comparison.

Author/Year	Flap design compared	Sample size	Parameters	Result
Stephen J.R et al. (1983)24	A. Envelope flap B. Modification of the envelope flap	15	Periodontal pocket depth	Not significant
Krik D.G. et al. (2007)25	A. Buccal envelope flap B. Modified triangular flap	32	Pain, mouth opening, swelling, incidence of alveolar ostietis	Not significant
Chin Quee T.A et al. (1984)3	A. Envelope flap B. Vertical flap	30	Alveolar bone height and Periodontal pocket depth	Not significant
Rosa et al. (2002)9	A. 3 cornered flap B. Szmyd flap	14	Probing depth and Clinical attachment level	Not significant
Nageshwar et al. (2002)17	A. Distolingually based flap by Buccal comma shaped incision B. Conventional modified envelope incision	50	Pain, swelling, trismus, periodontal status	Buccal comma shaped incision shows parametric significance.
Saurez et al. (2003)16	A. Para marginal flap B. Marginal flap	27	Wound healing, periodontal pocket depth, pain, swelling, trismus	Not significant
Erdogan Ö et al. (2011)13	A. Envelope flap B. Triangular flap	20	Pain, mouth opening, facial swelling	Not significant
Silva et al. (2011)18	A. Vertical incision [technique A] B. L-shaped flap [technique B]	24	Periodontal probing depth.	No statistically significant difference in flap design. The alternative flap technique (technique A) better wound healing.
Briguglio et al. (2011)19	A. Envelope flap modified [Thibauld and parant] B. Laskin triangular flap C. Envelope flap modified [Laskin]	45	Periodontal health, Clinical attachment	Statistical significance in reduction of pocket probing depth and increase of clinical attachment level in group B compared to the other groups.
Koyuncu et al. (2013)12	A. Envelope flap B. Modified triangular flap	80	Incidence of alveolar osteitis, Postoperative pain, swelling,	The envelope flap design was associated with a higher incidence of AO that was not statistically significant. Second day postoperative pain and swelling was observed as significantly different with the envelope flap technique.
Desai et al. (2014)10		30	visibility, accessibility, excessive bleeding during surgery, healing of flap, sensitivity of adjacent teeth, and dry socket	No statistical differences were noted between the groups in terms of visibility, accessibility, excessive bleeding during surgery, healing of flap, sensitivity of adjacent teeth, and dry socket. A statistically significant difference was observed in postoperative hematoma, wound gaping, and distal pocket in adjacent tooth, which was significant in Ward's triangular incision.

Fig. 6.

Surgical accessibility of oblique anterior release incision in conventional Ward's.

6. Discussion

The advent of new flap designs in third molar impaction surgery is truly based on various surgical challenges faced by oral surgeons. The most commonly incorporated incisions that are currently followed are the Wards, and the envelope incision.¹² Several complications commonly associated with third molar impactions comprise of pain, swelling, trismus, nerve injury, and dry socket.¹³ Various flap designs were modified to minimize the aforesaid complications and long-term studies were conducted to assess and evaluate the efficacy of flap designs. Regardless of variations in flap design, the fundamental principle of flap vascularity aiding wound healing should be abided.^5,6 According to Pederson et al. (1985),⁸ the interrelationship between trismus and pain has been reported in many studies. Pain was the main reason for reduced mouth opening after third molar surgery. Post-operative pain after third molar surgery is a result of biochemical mediators involved in the pain process, mainly histamine, bradykinin, prostaglandins, and is directly related to resultant cellular and tissue destruction.¹⁴ Hence, flap injury incurred during impaction surgery plays a vital role in pain score (VAS) rather than flap design. Similarly, infection and iatrogenic trauma to hard/soft tissue contribute significantly to postoperative swelling which is prominent after 19–24 h and subsides in about 7 days.¹⁵ The majority of studies on flap designs performed by various authors over the years concluded that no statistical significance was noted in the parametric variance evaluated. Chin Quee et al. (1984),³ in their study compared vertical and envelope flap, evaluated the periodontal attachment levels distal to the second molar. Their study revealed a significant loss of attachment for both flap designs and conferred that the initial height of alveolar bone distal to the second molar had no significance on attachment loss. Kugelberg et al. (1985)⁴ in their study found a significant periodontal pocket depth of greater than 7 mm distal to second molar which was directly affected by plaque formation over a period of two years. In our study, the control group had a mild increase in periodontal probing depth after one month of a surgery compared to the control group emphasizing the fact that mobilization of the flap can be comfortably achieved by applying a straight anterior release without feathering the buccal soft tissues. Suarez et al. (2003),¹⁶ stated that flap design influences primary wound healing after third molar surgery. A comparison between paramarginal and marginal flap revealed a higher incidence of wound dehiscence in the former due to tension. However, other parametric variances like pain, mouth opening, and swelling did not prove significant. Studies conducted by Nageshwar et al. (2002),¹⁷ Silva et al. (2011),¹⁸ Briguglio et al. (2011),¹⁹ Boscho et al. (1977)²⁰ and Desai et al. (2014)¹⁰ had provided statistical significance among one or more parametric variances to prove the superiority of one flap design over the other. According to Bataineh et al. (2016)²¹ modified flap design replicating the outline of the impacted lower crown; whereas standard posterior and vertical incision was made at a variable length required that provided an adequate exposure when compared with the other flap patterns of impactions without reflecting the lingual flap and gives protection to the lingual nerve damage. Korkmaz et al. (2015)²² compared 3- cornered LRF (Laterally rotated flap) with 1° closure and an envelope flap with 2° closure for partially impacted third molar showed a considerable influence on the periodontal status of the second molar. 3-cornered LRF(Laterally rotated flap) design group had severe pain and swelling, even though this had an early influence on periodontal healing when compared to the envelope flap. AmparoAloy-Prósper et al. (2010)²³ stated that flap design does not influence on probing depth or attachment level on the distal aspect of the lower second molar following surgery of the lower third molar. The study incision was found to be convenient in case of partially impacted teeth with class I, position A category, whereas, in deep-seated case in class II, position C categories of impaction, Ward's incision with oblique relieving incision had better favourability in tooth exposure.Accessibility and flap exposure for the study incision was better in mesioangular and vertical impaction, whereas the Wards' incision was better preferred for horizontal and distoangular impaction. Various studies comparing two or more flaps have proved less significant in multiple parametric variances that were assessed statistically irrespective of large sample size (Table 5). Our study too showed similarity in their results, with minimal significance between study and control group except for accessibility. The literature review on several third molar incision studies mostly follows the routine parameters for flap design evaluation but has not emphasized the role of surgical accessibility provided by the flap in creating inoperable surgical space as per the surgeon's convenience. Our study, by incorporating accessibility as a key parameter was able to determine the appropriate flap design needed to implement for different kinds of impactions based on its position.

Table 5.

Statistical comparison on surgical accessibility between study and control group incision.

Group	Study	Control	Total	P value
Easy Moderate Difficult Total	10 (40.0%) 9 (36.0%) 6 (24.0%) 25	21 (84.0%) 4 (16.0%) 0 (0.0%) 25	31 13 6 50	0.00184 (<0.05,Highly significant)

7. Conclusions

The conventional Ward's incision with oblique anterior release incorporated in third molar surgery provided better accessibility and ease to the operating surgeon. Though there was no statistical significance between the flaps designs, we could observe that closure of the surgical site with an anterior oblique release leads to displace the tissues in the buccal vestibule that can interfere with the healing distal to second molar leading to post-operative periodontal pocket formation. This can be effectively avoided by using a straight anterior release incision; hence we favour the use of vertical anterior release incision in conventional Ward's. The routine parameters implemented to evaluate flap design is not always the sole reason predicting the surgical outcome of third molar impaction surgery, but also depends on various other factors such as the level of surgical difficulty, patient's compliance, surgeon's skill and experience that directly influences the duration of surgery.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors’ contributions

All the authors have contributed equally for the following study.

Declaration of competing interest

“The authors certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript”.