The effectiveness of oral irrigators on periodontal health status and oral hygiene of orthodontic patients: a systematic review and meta-analysis

Abstract

Background

An Oral irrigator, known as a dental waterjet (DWJ), is an adjunctive oral hygiene tool to remove dental plaque. The aim of this study was to systematically evaluate the effectiveness of oral irrigators on orthodontic patients’ oral hygiene and periodontal status.

Methods

A comprehensive search was undertaken in five electronic databases (PubMed, EMBASE, Web of Science, Scopus, and Cochrane) up to 1 May 2024. Clinical trials comparing DWJ with other adjunctive tools or no adjunctive in healthy orthodontic patients were included. The outcome was periodontal health condition measured by periodontal indexes. The risk of bias of the included studies was assessed using the Cochrane risk of bias tool. Random- effects meta- analyses of mean differences (MD) with their 95% confidence intervals (CI) were conducted and the overall quality of evidence was evaluated by GRADE approach.

Results

Seven trials were included in the meta-analysis (Two with low, and others with unclear risk of bias). There was no statistically significant difference between automatic toothbrush (ATB) with DWJ and ATB alone in the gingival index (GI) (MD = 0.00; 95% CI -0.17- 0.18) (low quality of evidence). No statistically significant differences were found between (ATB + DWJ) and manual toothbrush (MTB) alone in the GI (MD= -0.11; 95% CI -0.31- 0.09) (very low quality of evidence). Also, no significant difference was detected between the two groups in the Plaque index (PI) (MD= -0.12; 95% CI -0.36- 0.11) (very low quality of evidence). There was no statistically significant difference between (MTB + DWJ) and MTB alone in the GI (MD= -0.06; 95% CI -0.16- 0.03) (very low quality of evidence). No statistically significant differences were revealed between the two groups in the PI (MD= -0.33; 95% CI -0.97- 0.32) (very low quality of evidence). No statistically significant improvements were found between these two groups in bleeding index (BI) (MD= -0.05; 95% CI − 0.12 − 0.01) (low quality of evidence).

Conclusions

Adding DWJ to either manual or automatic toothbrushes did not significantly enhance oral health of orthodontic patients. Orthodontists could recommend their patients to use either of these toothbrushes with or without DWJ. Further clinical trials are needed.

Trial registration number

The protocol of this study was registered on PROSPERO with the ID # CRD42023465849.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-024-05255-w.

Background

Fixed orthodontic appliances create obstacles for oral hygiene due to the additional retentive areas for plaque accumulation around the brackets, bands, and beneath the archwires [1–3]. Also, fixed appliances modify the supragingival and subgingival microbiota of oral biofilm, resulting in increased pathogenic bacteria colonization in the plaque [4]. Orthodontic patients with improper oral hygiene during the treatment are at higher risk of developing white spot lesions, dental caries, gingivitis, gingival enlargement, and periodontitis [5]. According to a recent systematic review, there is a correlation between orthodontic treatment and periodontal condition, and orthodontic treatment could be associated with several periodontal complications such as gingival recession, attachment loss, and alveolar bone loss [6].

An efficient and daily self-care routine is highly recommended for plaque removal, to maintain proper health of dental and periodontal tissues during an average length of 2 years for orthodontic treatment [7, 8]. Choosing the best oral hygiene tools is an essential part of motivating orthodontic patients. Numerous devices are available to provide good oral care such as manual toothbrushes with toothpaste, electric toothbrushes, orthodontic toothbrushes, toothbrushes with different head designs, oral irrigators, dental floss, and interproximal toothbrushes [9, 10].

It is widely accepted that the use of toothbrush alone is not sufficient for interproximal plaque removal and dental floss is required to reduce interdental bleeding and gingivitis. The rate of daily dental flossing is low, not only among the common population but also orthodontic patients [7]. Based on the evidence, dental floss is only effective on the anterior teeth of orthodontic patients, not on the posterior teeth, because of the difficulty of its application [11].

Oral irrigator, also named as dental waterjet (DWJ) or water flosser, is one of the oral hygiene aids that acts as a vehicle for delivering water with certain pressure and pulsation to subgingival, interdental, and unreachable areas [8]. Oral irrigator has been used as an adjunctive aid to tooth- brushing to remove dental plaque and improve oral hygiene [12]. Several clinical studies have demonstrated the benefits of water flosser in reducing gingival inflammation, bleeding, and pathogenic bacteria in various non-orthodontic patients, such as patients in a supportive periodontal maintenance program, patients with implants, crowns, or bridges, and diabetic patients [13–21].

The effects of oral irrigators on periodontal condition of patients undergoing orthodontic treatment remain controversial due to the varied results reported by several clinical studies [8–11, 22–30]. Some of these studies have shown positive results, however other studies did not report any benefit in using oral irrigators. To the best of our knowledge, no systematic reviews assessing the effects of oral irrigators on oral hygiene and periodontal health condition of orthodontic patients have been reported in the literature. The aim of the present study was to systematically synthesize data from the available literature to evaluate the effects of oral irrigators on orthodontic patients’ oral hygiene and periodontal status. Also, the study analyzed clinical outcomes including periodontal indexes (plaque index (PI), gingival index (GI) and bleeding index (BI)).

Methods

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) Statement Guidelines [31]. The protocol of this study was registered on PROSPERO (https://www.crd.york.ac.uk/PROSPERO/) with the ID # CRD42023465849.

Eligibility criteria

The study followed the PICOS format (i.e., Population, Intervention, Comparison, Outcome, and study design), with the following criteria: Population (P): healthy orthodontic patients; Interventions (I): the use of oral irrigator as an adjunctive aid; Comparison (C): alternative adjunctive aid or no adjunctive; Outcome measured (O): the periodontal health condition measured by periodontal-related indexes (GI, PI, and BI); and Study design (S): Randomized clinical trials (RCTs) and controlled clinical trials (CCTs), including both parallel-group and split-mouth designs. Thus, the focused question based on the PICOS format was: Does oral irrigator significantly enhance the periodontal health condition of orthodontic patients compared to the control group?

The following selection criteria were considered for this systematic review:

1. Inclusion criteria: Randomized clinical trials and controlled clinical trials, including both parallel-group and split-mouth designs, reporting the effects of oral irrigators on oral hygiene and periodontal health condition of orthodontic patients.

2. Exclusion criteria: Animal studies, in vitro histological studies, systematic review articles, case reports, letters to the editor, and studies recruiting patients with systemic diseases or those being medically treated were excluded.

Information sources and search strategy

An electronic search was performed up to 1 May 2024 to acquire potentially eligible studies in the following electronic bibliographic databases: PubMed, EMBASE, Web of Science, Scopus, and Cochrane. Search strategies of each database are presented in Table 1. The reference part of the retrieved full-text articles (cross-referencing) was also manually searched for further papers.

Table 1.

Databases, applied search strategy, and the number of retrieved studies

Database of published trials	Search strategy used	Hits
MEDLINE searched via PubMed, searched on 1 May 2024, via www.ncbi.nlm.nih.gov/sites	“waterjet“[Title/Abstract] OR “waterpik“[Title/Abstract] OR “water floss“[Title/Abstract] OR “water flosser“[Title/Abstract]) AND (“oral hygiene“[MeSH Terms] OR “oral hygiene“[Title/Abstract] OR “plaque removal“[Title/Abstract]	70
ISI web of science Core Collection was searched via web of knowledge on 1 May 2024, via apps.webofknowledge.com	‘waterjet’ OR ‘waterpik’ OR ‘water floss’ OR ‘water flosser’ (All Fields) and ‘oral hygiene’ OR ‘plaque removal’ (All Fields)	48
Embase searched via Embase on 1 May 2024, via www.embase.com	(‘water jet’/exp OR ‘water jet’ OR ‘waterpik’ OR ‘water floss’ OR ‘water flosser’) AND (‘oral hygiene’ OR ‘plaque removal’)	30
Scopus searched via Scopus on 1 May 2024, via https://www.scopus.com	(TITLE-ABS-KEY (“water jet” OR “watermark” OR “water flosser” OR “water floss”) AND TITLE-ABS-KEY (“oral hygiene” OR “plaque removal”))	13
Cochrane Central Register of Controlled Trials searched via the Cochrane Library Searched on 1 May 2024 via www.thecochranelibrary.com	‘waterjet’ OR ‘water jet’ OR ‘waterpik’ OR ‘water floss’ OR ‘water flosser’ in Title Abstract Keyword AND ‘oral hygiene’ OR ‘plaque removal’ in Title Abstract Keyword	118
Total		279

Study selection and data extraction

Two authors (Sh.T. and Z.Z.) screened the titles and abstracts of the searched studies independently. Studies were excluded if they were not relevant to the current study or duplicates. Full-text evaluation of publications was considered if sufficient information was not provided in the title and abstract. The disagreements were resolved through discussion. Where resolution was not possible, a third review author was consulted (L.S.). The review authors were not blinded to the author(s), institutions, or site of publication of the studies.

All the eligible studies then underwent validity assessment and data extraction. At least two review authors (Sh.T. and L.S.) extracted data independently. Any disagreement was discussed, and a third review author (Z.Z.) consulted where necessary. Agreement between reviewers was measured using the kappa statistic, which was within acceptable range of 0.86 to 1. Authors were contacted by email in case of any missing data.

Finally, the following data were extracted from the eligible studies using extraction forms: study design, sample size, baseline participant characteristics (age, gender), type of the oral irrigator, study groups, evaluation time, the outcome measured, and the main result.

Risk of bias assessment

The quality of all the included studies was assessed by two investigators (Sh.T. and L.S.) independently and in duplicate, using the Cochrane risk of bias assessment tool for Randomized Controlled Trials [32]. We assessed seven specific domains (namely random sequence generation, allocation concealment, selective reporting, blinding of participants and personnel, blinded outcome assessment, incomplete outcome data, and other biases) as at low, high or unclear risk of bias. A study was regarded as low-risk only if all the domains were evaluated as low-risk. If one or more domains were evaluated as unclear, the study was categorized as unclear-risk. Any domain examined as high-risk in that study was classified as a high risk of bias. A third review author resolved any controversies of the reviewers.

Summary measures and synthesis of results

A meta-analysis was performed using Stata software (Stata version 17, StataCorp LP, College Station, TX, USA). The data for the primary outcomes (PI, GI, and BI) were continuous, and the mean difference (MD) with 95% confidence intervals (CIs) were calculated. The heterogeneity among the included studies were assessed using I² statistic test. Weighted averages and 95% confidence intervals were pooled using a random-effects model. Meta-regression analysis was conducted based on follow up duration in months. P value less than 0.05 was considered statistically significant.

A network meta-analysis (NMA) was conducted using package “netmeta” in R (version 4.4.4; R Foundation for Statistical Computing, Vienna, Austria) to rank the most effective intervention groups for reducing the gingival index.

The publication bias could not be tested due to number of included studies (< 10 studies).

Quality of the evidence

The GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach was used to assess the overall quality of the evidence in each study [33].

Results

Results of the search and study selection

The electronic database searches resulted in 279 references, and further ten studies were identified through other sources and manual search. After removal of duplicates, 68 studies were identified. Twenty- nine potentially relevant studies were identified after title/ abstract screening and full text articles were retrieved. After further assessment, a total of 15 studies met the inclusion criteria [8–11, 22–30, 34, 35], only 7 studies were included in the meta- analysis (Fig. 1) [23, 25–27, 29, 30, 35].

Fig. 1.

PRISMA flow diagram

General characteristics of included studies

The detailed characteristics of the included studies are summarized in Table 2.

Table 2.

Baseline characteristics of the included studies

	Author/Year/Country	Study design	Sample size	Gender	Mean age (Range)	Type of waterjet	Study groups	Evaluation time	Assessment methods	Outcomes
1	Rathore et al. [35] 2024 India	single-blind, randomized clinical trial	80 patients	31 M 49 F	18–25	- water irrigator (ORACURA® OC001)	Group 1: Manual orthodontic toothbrush (STIM® Ortho MB) with active reminder Group 2: Powered toothbrush (Colgate® Charcoal 360) with water irrigator and active reminder Group 3: Manual orthodontic toothbrush (STIM® Ortho MB) Group 4: Powered toothbrush (Colgate® Charcoal 360) with water irrigator	Baseline(T0), 2(T1), 4(T2), 8(T3), 12(T4) weeks	- plaque index (PI) - Gingival index	Using powered toothbrushes and oral irrigators resulted in a statistically more significant reduction in plaque and gingivitis scores than conventional procedures. Active reminders had a catalytic effect in improving the oral hygiene.
2	AlMoharib et al. [34] 2024 Saudi Arabia	single-blind, randomized, parallel clinical trial	30 patients	Not reported	18 years or older, not reported in detail	Not reported	- Group 1: Manual toothbrush with interdental brush - Group 2: Manual toothbrush with waterjet flossing	Baseline, 14 days	- Gingival bleeding index (GBI) - Plaque index (PI) - Gingival index (GI)	Both water jet flossing and interdental flossing were effective in reducing plaque accumulation and gingival bleeding among orthodontic patients. While no significant differences were found between the two methods.
3	Tyler et al. [26] 2023 UK	Single- Centre, single-operator, two-arm, parallel-group, stratified, single-blind RCT	40 patients	Not reported	10–20	- Waterpik® Water Flosser Model WP-560 (Water Pik, Inc, Fort Collins, CO, USA) - Once a day at night for approximately 1 min	- Group 1: manual toothbrush with Waterpik® - Group 2: manual toothbrush only	Baseline (T0), 8 weeks (T1), 32 weeks (T2) and 56 weeks (T3)	- Orthodontic Modification of Plaque Index (OMPI) - Plaque Index (PI) (Silness and Loe - Gingival Index (GI) (Loe and Silness) - Interdental Bleeding Index (IBI) (Caton and Polson) - Adherence to oral hygiene regime - Satisfaction with oral hygiene regime - Trauma	-There is no benefit, in terms of plaque control or gingival health, in using a WaterPik® for patients wearing fixed orthodontic appliances.
4	Wiesmüller et al. [28] 2023 Austria	Randomizedcontrolled crossover study	20 patients	Not reported	18–49	- Oral irrigator with microburst technology (Airfloss®, Philips, Hamburg, Germany)/ three sprays per activation	- Group 1: orthodontic toothbrush with oral irrigator and routine brushing - Group 2: dental floss (Superfloss®) and routine brushing	28 days, 56 days, and 84 days	- Rustogi Modified Navy Plaque Index (RMNPI) - Gingival bleeding index (GBI)	Oral irrigators do not remove plaque and reduce gingival bleeding as efficiently as dental floss in easily accessible regions. However, in posterior regions, where the patients struggled with the application of dental floss, the oral irrigator showed similar results.
5	Al Hariri et al. [22] 2023 Syria	Three-arm, parallel‐group randomized controlled trial	45 patients	27 F 18 M	12.8 ± 1.37 (11–15)	- DWJ flosser with the orthodontic jet tip (Water Jet, JollyDent) / The flosser tip: at 90° angle to the tooth surface and for 3 s per tooth/ at medium pressure (70 psi) and 1200 pulses per minutes. - The overall cleansing time: around 2 min.	- Group1: Dental waterjet - Group 2: Orthodontic tooth brush (O-TH) - Group 3 (control): Conventional tooth brush (C-TH)	After 4 h of the last brushing then immediately after cleansing.	- Orthodontic Plaque Index (OPI) (assessing the plaque scores and marginal gingivae inflammation)	- The level of oral hygiene was not satisfactory in orthodontic patients. - The efficacy of the DWJ was not superior to O-TH nor to C-TH in plaque removal.
6	Sawan et al. [10] 2022 Saudi Arabia	single-blind, randomized, controlled, clinical trial with a split-mouth protocol	34 patients	17 F 17 M	18–35 (23.7 ± 7.7 years)	- Waterpik® water flosser/ the tip of the flosser at a 90-degree angle to the tooth surface/the pressure range between 45 and 75 PSI (3.103 to 5.171 Bar), with a flow rate per minute of 8 ounces (237 ml), and 1200 pulses per minute. - 2 min to brush and another 2 min to clean interproximal	- Group 1 (one side of the mouth): using a water flosser in addition to traditional brushing - Group 2 (other side of the mouth): using Super floss® (Oral-B) in addition to traditional brushing	Baseline, immediately after cleaning	- Rustogi et al. modified navy plaque index (RMNPI)	Both groups showed a significant reduction in plaque index postintervention - there was no significant difference between two groups.
7	Şahin et al. [8] 2022 Turkey	Randomized controlled trial	30 patients	Not reported	12–18	- Oral irrigator (Aquapick, AQ-300, Aquapick Co, Ltd, Korea)	- Group1: toothbrushes and additionally oral irrigators (OIs) - Group 2: toothbrushes and additionally interdental brush (IBs)	Baseline, 2nd, 4th, and 8th weeks	- Plaque index (Silness and Loe) - Gingival index (Loe and Silness) - Bleeding on probing (BOP) - probing pocket depth (PPD) - clinical attachment level (CAL) - Biochemical Evaluation: interleukin (IL)-1β, IL-10, matrix metalloproteinase (MMP)-1, MMP-8 mediators	- OI group shows lower PI, GI, and BOP values as compared to IB group. - There were no significant differences in IL-10 and (MMP)-1 levels between groups.
8	Mazzoleni et al. [23] 2019 Italy	RCT with a split mouth protocol	20 patients	10 F 10 M	13–32	- DWJ Philips Sonicare Airfloss - Once a day in the evening	- Group 1 (one side of the mouth): using a DWJ in addition to traditional brushing - Group 2 (control, other side of the mouth): just brushing	Baseline, at one, three and six-months follow-up.	- Gingival index (Loe and Silness) - Plaque index (Silness and Loe)	The dental water jet does not improve significantly the efficacy of home oral hygiene in orthodontic patients.
9	Quaranta et al. [24] 2018 Italy	RCT with a split mouth protocol	22 patients	Not reported	12–18	- Sonicare Air Floss®	- Group 1 (one side of the mouth): medium orthodontic toothbrush and Sonicare Air Floss® - Group 2 (control, other side of the mouth): medium orthodontic toothbrush only	Baseline, 15 days and one month	- Plaque control record (PCR) - Bleeding on probing (BOP) - Intraoral photos	Use of a mechanical interdental cleaning device combined with manual toothbrush improves self-performed plaque control and gingival health in orthodontic patients.
10	Patel et al. [27] 2015 India	Four-arm, parallel‐group randomized active-controlled trial	60 patients	Not reported	12–22	- Oral irrigation device with orthodontic tip (the Waterpik cordless Plus Water Flosser, USA)/ pulsating stream of water with exit pressure ranging from 45 to 75 psi/ capacity of 210 ml in the resorvior - Twice daily/ one minute irrigation	- Group 1: automatic tooth brush - Group 2: oral irrigation with manual toothbrush - Group 3: oral irrigation with automatic tooth brush - Group 4 (control): manual tooth brush	Baseline, one- month, and two-month periods.	- Gingival index (modified by Loe) - Plaque index (Silness and Loe)	Powered brushes alone or along with oral irrigation do not seem to be additionally beneficial when compared to the other groups.
11	Soni et al. [9] 2012 Gurgaon	randomized single-Centre, single-blind study	60 patients	Not reported	13–20	Not reported	- Group 1: orthodontic toothbrush only - Group 2: orthodontic tooth brush with mouthwash (chlorhexidine 0.12%) - Group 3: orthodontic toothbrush with waterjet device.	Baseline, 3rd, 6th, 9th and, 12th weeks	- Modified plaque index (mQHI) (according to Quigley & Hein) - Sulcus bleeding index (Muhlemann and Son)	The results showed a significant reduction of plaque index and bleeding index in dental waterjet group.
12	Sharma et al. [7] 2008 Canada	randomized, single-center, single-blind, parallel clinical study	106 patients	59 M 47 F	11–17	- DWJ with orthodontic jet tip (model WP-100 W; Water Pik, Fort Collins, Colo) - Once a day in the evening	- Group 1: DWJ with orthodontic jet tip (model WP-100 W; Water Pik, Fort Collins, Colo) and a manual toothbrush (MT) (Oral-B Soft Compact 35; Proctor & Gamble, Cincinnati, Ohio); - Group 2: unflavored waxed dental floss (FL) (Johnson & Johnson, Skillman, NJ) used with a floss threader (GUM Eez-Thru; Sunstar Americas, Chicago, Ill) plus a MT (Oral-B Compact 35) - Group 3: MT (Oral-B Compact 35) only.	Baseline, 2nd and 4th weeks	- Modified plaque index (PI) - Gingival bleeding index (BI)	The DWJ is more effective than flossing and routine brushing for the reduction of plaque and bleeding.
13	Kossack et al. [11] 2005 Germany	four-way, crossover randomized controlled clinical trial	40 patients	25 F 15 M	13.9 years (12–22)	- Water Pik® Flosser FL-110 (Intersanté, Bensheim, Germany).	- Group 1: manual interX short brush-head toothbrush - Group 2: Sonic Speed SR-100E sonic toothbrush - Group 3: Sonic Speed sonic toothbrush and the electric interdental cleaning device Flosser FL-110 - Group 4: Sonic Speed sonic toothbrush and multi-floss 3-phase dental floss	Three times during each test series, once before testing, once after 2 weeks, and once after 4 weeks.	- The Papillary Bleeding Index (PBI) (according to Mühlemann) - Modified plaque index (mQHI) (according to Quigley & Hein)	Plaque and gingivitis can be reduced by using an interdental cleaning aid especially in patients with poor oral hygiene. In the long run, the Flosser FL-110 is more effective than multi-floss 3-phase dental floss.
14	Burch et al. [29] 1994 USA	three-arm, parallel‐group randomized active-controlled trial	47 patients	Not reported	21–48	- Oral irrigation device (WaterPik, Teledyne WaterPik, Ft. Collins, Colo.) with tap water /a pulsating stream of water with an exit pressure of 55 to 65 psi, using 400 to 500 ml tap water for each irrigation. - Once per day in addition to brushing.	- Group 1 (control): manual toothbrush - Group 2: adjunctive oral irrigation device and manual toothbrush. - Group 3: adjunctive oral irrigation device and an automatic toothbrush	Baseline, one- month, and two- month periods	- Gingival index (Loe and Silness) - Plaque index (Silness and Loe) - Bleeding after probing (the method described by Muhlemann et al.) - Gingival sulcus depths	Significant reductions in plaque, gingival inflammation, and a tendency for reduced bleeding after probing occurred in both groups with the power device. These improvements were attributable to the effect of the oral irrigation device.
15	Jackson et al. [30] 1991 USA	Randomized controlled clinical trial	20 patients	12 F 8 M	- Not reported–4 Adults - 16 Adolescents	- Not reported - Twice a day/ 1 min irrigating after 1 min brushing	- Group 1: manual toothbrush - Group 2: electric toothbrush - Group 3: manual toothbrush and irrigation - Group 4: electric toothbrush and irrigation	Baseline, after at least 4 weeks	- Gingival health index (modification of the Silness and Loe) - Orthodontic plaque index	Although a significant difference between the groups was not found, the groups that used irrigation had the better overall gingival health scores.

Types of included studies

All of the studies were RCTs [8–11, 22–30, 34, 35]. Three RCTs were split- mouth trials [10, 23, 24]. Four RCTs were three- arm trials [9, 22, 25, 29], three were two- arm trials [8, 26, 34], and three RCTs were four- arm trials [27, 30, 35]. Two RCTs were cross- over trials [11, 28].

Characteristics of trial settings and investigators

Twelve of the studies were carried out in a hospital or university setting [8–10, 22–24, 26–30, 35]; the others were undertaken in private orthodontic office [11, 25, 34].

Characteristics of participants

A total of 654 orthodontic patients (ranging from 10 to 49) were included in the 15 studies overall. In eight studies, the gender distribution of participants was not reported [8, 9, 24, 26–29, 34]. The remaining studies included a total of 187 female and 158 male patients. There were more males than females in one study [25], two studies had equal number of male and females [10, 23], and other studies had more females than males. In total, the oral irrigator (dental waterjet) arm of the studies included 344 participants.

Participants with normal periodontal health were included in five studies [22, 23, 26, 34, 35], six studies included patients with generalized gingivitis [8, 9, 24, 25, 27, 29], and one study included participants with different oral health conditions [30].

Limited information was given in relation to the type of orthodontic treatment (extraction versus non- extraction); however, three studies only included patients requiring non- extraction orthodontic treatment [11, 23, 27].

Characteristics of interventions

An intervention evaluated in the identified studies was oral irrigator (dental waterjet, water flosser). In one study, oral irrigator was used alone in one of the study arms [22]. Participants in the oral irrigator group also received an automatic toothbrush (ATB) in five studies [11, 27, 29, 30, 35], orthodontic tooth brush (OTB) in three studies [9, 24, 28], and manual tooth brush (MTB) in nine studies [8, 10, 23, 25–27, 29, 30, 34]. The follow- up duration ranged from four hours to 56 weeks.

Characteristics of outcomes

Periodontal health was assessed by gingival index (GI), plaque index (PI), bleeding index, probing depth, and attachment level in included studies. One study also evaluated the incidence of oral hygiene-related trauma, adherence with an oral hygiene regime and satisfaction with an oral hygiene regime [26]. Evaluation of gingival crevicular fluid and intraoral photos were considered in two studies [8, 24].

Risk of bias assessment

The risk of bias in the included studies was assessed according to the Cochrane risk of bias assessment tool [36]. In the overall rating of the risk of bias, three studies were graded as having a low risk of bias [26, 28, 35], while the remaining twelve were graded as having an unclear risk of bias (Fig. 2). In all twelve studies with an unclear risk of bias, allocation concealment was not reported clearly. Among these twelve studies, seven were also rated as unclear due to inadequate random sequence generation [8–11, 23, 25, 27].

Fig. 2.

Risk of bias summary: authors’ judgments about each risk of bias item for each study

Main outcomes of included studies and meta-analysis

Automatic toothbrush and dental waterjet versus automatic toothbrush

Gingival index

This comparison included two studies (both trials at unclear risk of bias, 70 participants) that evaluated the differences in gingival index between (DWJ with ATB) and ATB alone in orthodontic patients [27, 30]. None of the studies found significant differences between two groups. There was no statistically significant difference between two groups in the meta-analysis (MD = 0.00; 95% CI -0.17 to 0.18, p = 0.98, I² = 0.00%). (Fig. 3A)

Fig. 3.

Forest plot of studies comparing DWJ + ATB versus ATB alone (A), DWJ + ATB versus MTB alone (B), and DWJ + MTB versus MTB alone (C) in terms of gingival index (GI)

Automatic toothbrush and dental waterjet versus manual toothbrush

Although there were 5 studies comparing (DWJ + ATB) with MTB alone, it was not possible to pool the results of one study in a meta- analysis. The design of this study was cross-over [11]. In the cross over studies, there might be carry-over effects for the different approaches on the periodontal health.

Gingival index

This comparison included four studies (three trials at unclear risk of bias and one at low risk of bias; 141 participants) that evaluated the differences in gingival index between (DWJ + ATB) and MTB alone in orthodontic patients [27, 29, 30, 35]. One of the four studies reported a significant reduction in the GI of intervention group compared to the control [29]. No statistically significant differences were found between two groups in the meta-analysis (MD= -0.11; 95% CI -0.31 to 0.09, p = 0.27, I² = 66.40%). (Fig. 3B)

Plaque index

This comparison included three studies (one at low risk of bias and two trials at unclear risk of bias, 101 participants) that evaluated the differences in plaque index between (DWJ + ATB) and MTB alone in orthodontic patients [27, 29, 35]. One study found a statistically significant greater reduction in the PI of intervention group [35]. In the meta-analysis, no statistically significant differences were found between the groups (MD= -0.12; 95% CI -0.36 to 0.11, p = 0.30, I² = 43.13%). (Fig. 4A)

Fig. 4.

Forest plot of studies comparing DWJ + ATB versus MTB alone (A), DWJ + MTB versus MTB alone (B) in terms of plaque index (PI)

Manual toothbrush and dental waterjet versus manual toothbrush

Although there were 8 studies comparing (DWJ + MTB) with MTB alone, it was not possible to pool the results of two studies in a meta- analysis, as the data from one study was presented as medians and interquartile ranges. This study reported a significant decrease in PI, GI, and BI in (DWJ + MTB) group compared to the control [8]. The other study had different evaluation time point (immediately after brushing) and modified periodontal index. It did not found significant differences between two groups [10].

Gingival index

This comparison included five studies (one at low risk of bias and four trials at unclear risk of bias; 181 participants) that evaluated the differences in gingival index between (DWJ + MTB) and MTB alone [23, 26, 27, 29, 30]. Four of the five studies reported no significant differences between groups [23, 26, 27, 30]. However, Burch et al. found a significant decrease in GI of (DW + MTB) group compared to the control [29].

In the meta-analysis, no statistically significant differences were found between the two groups (MD= -0.06; 95% CI -0.16 to 0.03, p = 0.19, I² = 19.96%). (Fig. 3C) Considering the longest follow-up (end point), the meta-regression analysis showed no statistical association with the individual effect sizes (p = 0.33).

Plaque index

This comparison included five studies (one at low risk of bias and four trials at unclear risk of bias; 212 participants) that evaluated the differences in plaque index between (DWJ + MTB) and MTB alone in orthodontic patients [23, 25–27, 29]. Two studies reported a significant decrease in PI of intervention group compared to the control [25, 27].

In the meta-analysis, no statistically significant differences were found between two groups (MD= -0.33; 95% CI -0.97 to 0.32, p = 0.32, I² = 98.22%). (Fig. 4B) Considering the longest follow-up (end point), the meta-regression analysis showed no statistical association with the individual effect sizes (p = 0.14).

Bleeding index

This comparison included three studies (one at low risk of bias and two trials at unclear risk of bias; 142 participants) that evaluated the differences in bleeding index between (DWJ + MTB) and MTB alone in orthodontic patients [25, 26, 29]. None of the studies found significant differences between two groups.

No statistically significant differences were found between two groups in the meta-analysis (MD= -0.05; 95% CI − 0.12 to 0.01, p = 0.11, I² = 0.00%). (Fig. 5)

Fig. 5.

Forest plot of studies comparing DWJ + MTB versus MTB alone in terms of bleeding index (BI)

Network meta-analysis (NMA)

The results of the network meta-analysis were represented in Fig. 6. The width of lines represents the number of trials in which each direct comparison is made. It was revealed that although there was no significant difference among different oral hygiene tools, (ATB + DWJ) showed more reduction in gingival index compared to (MTB + DWJ) or ATB alone.

Fig. 6.

Network diagram representing direct comparisons among Oral hygiene tools (A), and ranking of different Oral hygiene tools compared to MTB using NMA (B)

Quality of evidence

The overall quality of evidence was reported in Table 3.

Table 3.

GRADE assessment of the quality of the evidence

Outcomes	Mean difference (95% CI)	Number of participants (studies)	Quality of evidence (GRADE)
Automatic toothbrush and dental waterjet versus automatic toothbrush
Gingival index score	0.00 (-0.17 to 0.18)	70 (2 studies)	⊕⊕⊝⊝1 Low
Automatic toothbrush and dental waterjet versus manual toothbrush
Gingival index score	-0.11 (-0.31 to 0.09)	141 (4 studies)	⊕⊝⊝⊝ 2 Very low
Plaque index score	-0.12 (-0.36 to 0.11)	101 (3 studies)	⊕⊝⊝⊝2 Very low
Manual toothbrush and dental waterjet versus manual toothbrush
Gingival index score	-0.06 (-1.16 to 0.03)	181 (5 studies)	⊕⊝⊝⊝ 3 Very low
Plaque index score	-0.33 (-0.97 to 0.32)	212 (5 studies)	⊕⊝⊝⊝3 Very low
Bleeding index	-0.05 (-0.12 to 0.01)	141 (3 studies)	⊕⊕⊝⊝4 low

¹Downgraded twice: once for risk of bias and once for imprecision

² Downgraded three times: once for risk of bias, once for imprecision and once for inconsistency

³ Downgraded three times: once for risk of bias, once for imprecision and once for inconsistency

⁴ Downgraded twice: once for risk of bias, once for imprecision

Automatic toothbrush and dental waterjet versus automatic toothbrush

There was low quality of evidence to assess periodontal health of orthodontic patients based on gingival index scores. We downgraded the evidence due to unclear risk of bias and imprecision.

Automatic toothbrush and dental waterjet versus manual toothbrush

There was very low quality of evidence to assess periodontal health of orthodontic patients based on gingival index and plaque index. We downgraded the quality of evidence three times due to risk of bias, imprecision and inconsistency of the results.

Manual toothbrush and dental waterjet versus manual toothbrush

There was very low quality of evidence to assess periodontal health of orthodontic patients according to gingival index and plaque index scores. We downgraded three times due to risk of bias, imprecision and inconsistency of the results.

There was low quality of evidence to assess periodontal health of orthodontic patients according to bleeding index score. We downgraded the evidence due to unclear risk of bias and imprecision.

Discussion

Based on the evidence, fixed orthodontic treatment may worsen the patients’ periodontal conditions, particularly by increasing plaque accumulation and gingival inflammation [37, 38]. In the previous literature, it was found that orthodontic treatment could led to 0.13 mm alveolar bone loss and 0.23 mm increased pocket depth [39]. Proper oral hygiene instructions and patients’ motivation are important aspects of maintaining periodontal health during treatment. Oral hygiene aids could improve patients’ cooperation to achieve better results. DWJ is one of the homecare aids that offers the advantage of easy use for orthodontic patients, especially for hard-to-reach areas [28]. This systematic review and meta-analysis aimed to evaluate the effectiveness of DWJ on the periodontal status of orthodontic patients.

ATB with DWJ compared to ATB alone

Both studies in this comparison found no significant differences between the intervention and control groups [27, 30]. According to the meta- analysis results, DWJ did not have a significant impact on the periodontal health condition of the patients. It could be concluded that adding a DWJ to ATB did not offer any additional advantage, in terms of gingival health. However, this finding should be interpreted with caution due to the low quality of the evidence. The low quality of evidence was primarily due to the unclear risk of bias of included studies, and imprecision. A limited number of studies with small sample sizes in this meta-analysis contributed to the imprecision. The methods for random sequence generation, and allocation concealment required clarification in the included studies.

ATB with DWJ compared to MTB alone

Differing findings of the studies in this comparison could be attributed to the clinical heterogeneity among the studies, including variations in baseline characteristics of the participants, patients’ compliance, interventions (such as frequency of DWJ usage, water pressure, and type of waterjet), and periodontal condition of the participants at the baseline. Also, Hawthorne effect may have influenced the study outcomes, as participants may alter their oral hygiene behavior due to their awareness of being observed [40].

According to the meta-analysis results, there were no significant differences between (ATB + DWJ) and MTB alone. This finding indicated that a manual toothbrush could be as effective as a combination of automatic toothbrush and dental waterjet in terms of plaque control and periodontal health of orthodontic patients. It seems that the determining factor is the patient’s adherence to oral hygiene instructions. The results were consistent with those of Elshehaby et al., which showed no significant differences between manual and automatic toothbrushes in orthodontic plaque control [38]. Adding dental waterjet did not alter this outcome. The quality of evidence was very low, downgraded mainly due to the imprecision, unclear risk of bias of included studies, and inconsistency. The methods for random sequence generation, and allocation concealment were unclear in the included studies. Future well- designed trials are very likely to change the results.

Due to the lack of information about water pressure of DWJ, frequency of use, and patient compliance in most of the included studies, it was not possible to compare and interpret the results considering these confounding variables.

MTB with DWJ compared to MTB alone

In two of the studies that reported a significant difference in plaque index favoring the intervention group, the participants had generalized gingivitis [25, 29]. In contrast, the other studies with no significant results included patients with normal periodontium [23, 26]. This suggests that individuals with gingivitis may benefit more from the use of DWJ.

According to the meta-analysis, there were no significant differences between the group that used DWJ with MTB, and MTB alone for any periodontal variable. The quality of evidence ranged from very low to low. It was downgraded due to the imprecision, unclear risk of bias of included studies, and inconsistency. Random sequence generation, allocation concealment, and the outcome assessors’ blinding required clarification. This quality of evidence means that future trials might change the findings of this study. The population of three studies included in our meta-analysis consisted of patients with gingivitis [25, 27, 29]. Two studies included individuals with a healthy periodontium [23, 26], and one study included participants with different oral health conditions [30]. It should be noted that a mixed of good and poor periodontal health conditions in our meta-analysis could affect our outcomes. Considering that many orthodontic patients have some degree of gingivitis, examining patients with healthy gingiva may not accurately reflect common clinical conditions. Patients with good oral hygiene probably benefit less from additional devices due to their higher motivation and adherence to oral hygiene routines. Due to the lack of information about confounding variables (such as water pressure, frequency of use, and patient cooperation) in most of the studies, we could not compare the results considering these factors.

Although, interdental brushes and dental waterjet had higher rankings in reducing gingival inflammation in non-orthodontic patients, our results indicated that DWJ did not significantly improve the periodontal status of patients wearing fixed orthodontic brackets [37]. This difference could be attributed to the limited number of trials on orthodontic patients and clinical heterogeneity among the studies.

It should be noted that the time of assessment is one source of clinical heterogeneity among the studies. The follow-up intervals were different in included studies (from immediately after cleaning to a period of 56 weeks). The meta-regression analysis did not show any statistical difference in this study, and it suggests that the follow-up duration might not affect the DWJ’s effectiveness within the observed range. However, it should be interpreted with caution due to the small number of studies. This factor should be reevaluated when further trials are available.

Network meta-analysis (NMA) is a tool for comparing three or more groups simultaneously in a single analysis by combining both direct and indirect evidence. It performs better than conventional pair-wise meta-analysis in comparisons among multiple interventions [41]. According to the NMA results, ATB and DWJ reduced gingival inflammation more than three other approaches (albeit clinically and statistically non-significant). It revealed that the performance of four interventions were almost equal.

Conclusions

Available evidence (very low- to- low quality) suggests that the addition of dental waterjet to either manual or automatic toothbrushes does not significantly enhance oral health of orthodontic patients. Orthodontists could recommend their patients to use either of manual or automatic toothbrushes with or without dental waterjet. Each patient could choose any of these approaches based on personal preference. It should be noted that further well-designed studies are required due to the methodological limitations of included studies in this review.

Strengths

A comprehensive search strategy, the registration of its priori protocol in PROSPERO, and the use of GRADE approach to evaluate the certainty of evidence were the strengths of this study. Also, we categorized toothbrushes into automatic / manual, and differentially evaluated the effectiveness of each type in combination with DWJ.

Limitations

It should be noted that exclusion of gray literature may introduce potential publication bias. Also. the results of the current study should be interpreted with caution. Limited number of studies were included in each comparison, and the GRADE assessment of the evidence ranged from very low to low. We restricted the language of our search to English, which could reduce the number of studies. All studies examined short-term changes, with the maximum follow-up period of the trials being less than 3 months, except for one study which had a follow-up of 56 weeks [26]. This duration is relatively short compared to the whole duration of orthodontic treatment. Considerable heterogeneity was observed in all of the comparisons. It could be attributed to the limited number of trials and the use of modified indices across different studies.

Recommendations

More clinical trials on orthodontic patients need to be undertaken in order to increase the certainty of the findings. It is recommended that future randomized clinical trials adhere to the CONSORT Statement, as most of the studies did not adequately report their methods of randomization and concealment. Also, standardized indices should be applied in future studies to facilitate pooling the findings. Future studies should focus on patients with generalized gingivitis and poor periodontal health to evaluate the common clinical condition.

To improve the quality of future studies, it is also crucial to report the frequency of DWJ usage, water pressure, and the patient cooperation.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Abbreviations

DWJ

Dental waterjet

MTB

Manual toothbrush

ATB

Automatic toothbrush

NMA

Network meta-analysis

GI

Gingival index

PI

Plaque index

BI

Bleeding index

PRISMA

Preferred Reporting Items for Systematic Reviews and Meta-Analysis

GRADE

Grading of Recommendations Assessment, Development, and Evaluation

RCT

Randomized clinical trial

CI

Confidence interval

MD

Mean difference

Author contributions

Zahra Zarei (Z.Z.): Conceptualization, Methodology, Investigation, Writing-Original draft. Maryam Yazdi (M.Y.): Investigation, Formal analysis, Writing-Review and Editing, Supervision. Leila Sadeghalbanaei (L.S.): Investigation, Writing-Review and Editing, Supervision. Shabnam Tahamtan (Sh.T.): Conceptualization, Methodology, Formal analysis, Writing-Review and Editing, Supervision. All authors read and approved the final version of the paper.

Funding

Have no financial or non- financial support.

Data availability

The dataset(s) supporting the conclusions of this article is(are) included within the manuscript.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.