Envelope or triangular flap for surgical removal of third molars? A systematic review and meta-analysis


The aim of this systematic review was to compare the triangular and envelope flaps in mandibular third molar surgery with regard to pain, oedema, and trismus. Secondary outcomes assessed were dehiscence, ecchymosis, alveolar osteitis, periodontal condition, and surgical time. The PRISMA guidelines and recommendations in the Cochrane Handbook were followed, and the review was registered before commencement (PROSPERO; CRD42018112373). The literature search was conducted in the Web of Science, PubMed, Virtual Health Library, Cochrane Library, and Scopus databases and in the grey literature; randomized clinical trials, indexed through November 2018 were included. Three reviewers independently examined the studies. Twenty studies were included in the qualitative analysis, of which 18 were included in the meta-analyses. The flap design did not influence pain, oedema, trismus, dehiscence, or osteitis. The triangular flap was associated with a greater occurrence of postoperative ecchymosis (odds ratio 4.58, 95% confidence interval 1.34 to 15.91, I 2 = 0) and lower periodontal probing depth on day 7 postoperative (standardized mean difference −1.36, 95% confidence interval −2.68 to −0.03, I 2 = 88%) when compared to the envelope flap in mandibular third molar surgeries.

Lower third molars are known to be related to a series of complications, from eruption to the postoperative period following their removal . Although the complexity of third molar extractions depends on their position in the mouth and the oral condition, such as the presence of infection, these surgeries are often associated with a marked postoperative inflammatory process, which can lead to pain, oedema, and trismus, negatively affecting patient quality of life . Consequently, many surgical approaches have been considered to minimize such complications .

The surgical flap design should provide optimal visibility and access, as well as subsequent healing of the surgically affected area . The choice of flap design is made to allow the ideal surgical access and to minimize postoperative complications, such as pain, oedema, trismus, osteitis, haematoma, wound healing problems, and periodontal damage . The envelope flap and triangular flap are the most commonly used flap designs for impacted lower third molar surgeries .

Many studies have been performed to evaluate the effect of flap design on the surgical extraction of impacted third molars. These studies, however, have reported conflicting results regarding postoperative complications. Although a systematic review evaluating the effect of flap design on periodontal healing after impacted third molar extraction has been published recently , there is a lack of evidence in the literature about which flap design favours better postoperative conditions in general . Therefore, the objective of this systematic review was to compare the effects of the triangular and envelope (intrasulcular) flaps in mandibular third molar removal, on postoperative pain, oedema, and trismus, through an approach based on scientific evidence.

Materials and methods

This systematic review with meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and the Cochrane Handbook recommendations . The protocol was registered before commencement in the International Prospective Register of Systematic Reviews (PROSPERO; CRD42018112373).

The clinical question was formulated based on the PICO process (P: patient, problem, or population; I: intervention; C: comparison; O: outcomes). Thus, the question was: In patients submitted to lower third molar surgeries (P), does the use of the triangular flap design (I) result in differences in pain, oedema, and trismus (O) when compared to the use of the envelope flap (C)? Secondary outcomes assessed were wound dehiscence, ecchymosis, alveolar osteitis, periodontal condition, and duration of surgery.


Inclusion criteria were clinical trials in humans that evaluated the effect of the flap design (triangular or envelope) on pain and/or oedema and/or trismus in the surgical removal of mandibular third molars. The presence of outcomes dehiscence, alveolar osteitis, ecchymosis, and periodontal condition (evaluated through probing depth) were also considered for study inclusion. There was no restriction on publication language or date of publication.

Search strategy

An electronic search was conducted including articles published through November 2018 in the following databases: Web of Science, PubMed (MEDLINE), Virtual Health Library (VHL; LILACS and IBECS), Cochrane Library, and Scopus. The search strategy comprised a combination of medical subject heading (MeSH) terms. The terms used in the databases were: (third molar OR third molars OR tooth, wisdom OR wisdom tooth OR teeth, wisdom OR wisdom teeth) AND (flap* OR triangular flap* OR surgical flap OR flap, surgical OR flaps, surgical OR intrasulcular flap OR envelope flap OR approach).

The grey literature was also assessed to complete the search ( www.opengrey.eu ; scholar.google.com.br ).

Study selection

Three researchers (BCLS, GFM, and EFPM) independently evaluated the identified references. All references were managed and the duplicates removed using reference manager software (EndNote Web, Clarivate Analytics). To verify inter-rater concordance, prior to the beginning of the study selection, 10% of randomly retrieved articles were used to calculate the Cohen kappa index (0.84). After searching the databases, the titles and abstracts of all identified articles were evaluated independently by the same researchers against the eligibility criteria. All articles that met the inclusion criteria or did not provide enough information in the abstract to determine their inclusion, were read in full. After reading the articles in full, those that did not met the inclusion criteria were excluded. At this stage, all reasons for excluding the articles were recorded.

Data extraction

The same three researchers independently collected the methodological, clinical, and patient characteristics of the primary included studies. The following data were assessed: author, year of publication, country of origin, place where the surgical procedure was performed, study design, sample size, follow-up period. Patient characteristics included demographic variables (age and sex), involved third molar (38 or 48), presence of preoperative complication, pericoronitis, and tooth position. The following clinical characteristics were also recorded: flap design evaluated, postoperative complications (pain, oedema, trismus, ecchymosis, alveolar osteitis, dehiscence, and periodontal condition of the second molar), use of sedation, anaesthetic medication and anaesthetic technique, preoperative and postoperative drug protocol, surgical time, suture technique and thread, and the main conclusions of each study. The periodontal condition of the second molar was assessed by probing depth measurements.

Quality assessment

The same three researchers (BCLS, GFM, and EFPM) independently assessed the quality of the included studies through the Cochrane Risk of Bias Tool for Randomized Controlled Trials. Based on this tool, the following criteria were evaluated: random sequence generation, allocation concealment, blinding of patients and personnel, blinding of outcome assessor, incomplete outcome data, and selective outcome reporting. A further two criteria that could interfere in the success of the procedure were assessed: presence and description of the inclusion and exclusion criteria, and the evaluation of the presence of possible preoperative infections and pericoronitis. Each one of these components was classified according to the risk of bias as low risk, unclear risk, or high risk. This evaluation was guided by RevMan 5.3 software (Cochrane Collaboration, Oxford, UK).

Statistical analysis

The meta-analyses were conducted using R software version 3.3.2, with ‘meta’ and ‘metafor’ packages activated (R Foundation for Statistical Computing). Statistical heterogeneity among the results of the selected studies was tested by I 2 statistic. When I 2 was equal to 0, a fixed-effects model was used; when I 2 was >0, a random-effects model was used. The outcome measures were the mean difference (MD) for variables with standardized scales and the standardized mean difference (SMD) when there was no standardization (scales and metrics) in the data collection among the studies. The statistics were performed through the mean, standard deviation, and number of participants in each study group. The group of patients receiving a triangular flap were considered the experimental group, while those receiving an envelope flap were considered the control group. To analyse the statistical significance, confidence intervals (CI) of the results of each meta-analysis were evaluated.


Systematic search

The search strategy identified 2455 articles, of which 1449 were duplicates. Thus, 1006 articles remained for title and abstract reading. At this stage, 942 studies were excluded ( Fig. 1 ). The remaining 64 articles were considered potentially relevant and were read in full. Finally, 20 studies met the eligibility criteria and were included in the review . The included articles reported third molar surgery in 770 patients. The triangular flap was used for 556 teeth and the envelope flap for 559 teeth. However, only 18 articles (including 695 patients) provided enough information to be included in the meta-analyses .

Fig. 1
Flow chart of the screening process.

Description of the studies

The sample size of the included studies ranged from 12 to 196 patients. All patients in the primary studies were healthy and all studies compared the triangular flap with the envelope flap.

Most of the articles (70%) reported studies with a crossover clinical trial design, in which the same patient received both interventions at different time points and served as their own control . In these crossover studies, the mean reported washout period varied from 30 to 45 days. The included studies were published between 2002 and 2018, and most of them were from Europe and Asia , . All articles were written in English.

The patients ranged in age from 15 to 61 years. Seventeen of the 20 articles reported the sex distribution, showing a predominance of females (464 female and 249 male patients). Of all included studies, 11 evaluated pain , , 11 evaluated oedema , , and eight evaluated trismus , after the surgical removal of mandibular third molars. Dehiscence, the presence of ecchymosis, osteitis, and the periodontal condition of the second molar were evaluated by nine studies , , (45%), four studies (20%), six studies , (30%), and seven studies , (35%), respectively.

Most of the studies did not report preoperative protocols (antibiotic therapy, anti-inflammatories, and analgesics) , ; only seven described the preoperative protocol , and four of these performed antibiotic prophylaxis . The anaesthetic most used was 2% lidocaine associated with epinephrine (1:80,000; 1:100,000; 1:200,000) , . Articaine and mepivacaine were also used in the surgeries. With regard to the postoperative protocol, most of the prescriptions were for antibiotics (amoxicillin) , , and analgesics (diclofenac potassium, ibuprofen, codeine, ketoprofen, paracetamol associated with codeine, flurbiprofen, naproxen) . The main characteristics of the included studies, characteristics of the participants, and clinical characteristics are presented in Tables 1–3 , respectively.

Table 1
Main methodological characteristics of the included studies.
First author
Country Location Study design Sample ( n ) Follow-up
Iran Department of Oral and Maxillofacial Surgery, Babol Dental School, Babol RCT crossover 20 3, 7, 14 days and 4 weeks
Saudi Arabia Dental School, King Khalid University RCT crossover 60 1, 3, 7, 8, 15 days and 3 weeks
Jordan Unit of Oral and Maxillofacial Surgery at the Jordan University Hospital RCT crossover 19 2, 7, 14 days
India Department of Oral and Maxillofacial Surgery, K.M. Shah Dental College and Hospital, Vadodara RCT 30 15 days
Turkey Selcuk University RCT crossover 30 7 days
Turkey Department of Oral and Maxillofacial Surgery and Traumatology, Dental School, Çukurova University RCT crossover 20 3, 7 days
India Department of Oral and Maxillofacial Surgery, Dental School of Thiruvananthapuram Government RCT 50 2, 3, 7 days
Brazil Faculdade de Odontologia, Pontifícia Universidade Católica do Rio Grande do Sul RCT 34 7, 14 days
Austria Karl-Franzens University Graz RCT 60 1, 7, 14 days
Turkey Faculty of Dentistry, Ege University, Bornova, İzmir RCT 80 1, 2, 7 days
Italy Ambulatory patients, Dental Clinic, University of Ferrara RCT 25 2, 7 days
New Zealand NR RCT crossover 32 1, 2, 7 days
Turkey Faculty of Dentistry, Ondokuz Mayis University in Samsun RCT crossover 18 7, 14, 30 days and 1 year
Iran School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran RCT crossover 31 3, 7 days
USA Western University of Health Sciences, Pomona, CA RCT crossover 196 5, 7 days
Italy Department of Oral and Maxillofacial Surgery, Dental School of Bologna RCT crossover 12 7 days and 3, 6 months
Iran Mashhad University of Medical Sciences, Mashhad RCT crossover 60 7, 30 days
Turkey Gazi University Dental School, Ankara RCT crossover 28 7, 90 days
India Institute of Dental Sciences and Research, Mall Mandi, Amritsar, Punjab RCT crossover 20 1, 3, 7, 14, 30 days
Brazil Pontifícia Universidade Católica de Minas Gerais PUC-MG RCT crossover 15 3, 6, 12, 24 months

RCT, randomized clinical trial; NR, not reported.

Table 2
Characteristics of the populations enrolled in the included studies.
First author (year) Age, years
Mean (range)
Included third molar: left ( n ) Included third molar: right ( n ) Pell and Gregory classification (class/position)
Abandansari (2016) 23.5 (18–35) 12/8 20 20 I, II/A, B
Alqahtani (2017) NR (18–40) 60/0 60 60 NR
Baqain (2012) 21.4 (18–26) 12/7 19 19 NR
Desai (2014) 25.0 (25–30) NR NR
Dolanmaz (2013) NR (17–31) 16/14 30 30 NR
Erdogan (2011) 23.9 (20–32) 14/6 20 20 I, II/A, B
Rabi (2017) 25.5 (20–30) 26/24 NR
Nunes (2005) 22.5 (16–39) 21/13 I, II, III/A, B
Jakse (2002) 25.0 (15–60) 32/28 NR
Koyuncu (2013) 26.29 (18–45) 55/25 NR
Mobilio (2017) 27.88 (18–61) 18/7 NR
Kirk (2007) 24.2 (18–34) 24/8 32 32 NR
Kırtıloglu (2007) 20.8 (16–32) 12/6 18 18 NR
Mohajerani (2018) 20.1 (17–24) 19/9 28 28 I, II/C
Elo (2016) NR (NR) NR 126 126 NR
Monaco (2009) 16.0 (15–19) 5/7 12 12 NR
Rahpeyma (2015) NR (17–25) NR 60 60 I/B
Korkmaz (2015) 22.43 (18–28) 21/7 28 28 NR
Sandhu (2010) 25.0 (20–30) 3/17 20 20 NR
Briguglio (2011) NR (18–41) NR 15 15 NR
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Aug 10, 2020 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Envelope or triangular flap for surgical removal of third molars? A systematic review and meta-analysis
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