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The influence of flap design on patients’ experiencing pain, swelling, and trismus after mandibular third molar surgery: a scoping systematic review

Abstract

Third molar removal surgery usually comes accompanied by postoperative discomfort, which could be influenced by the surgical approach chosen. This scoping systematic review aimed at compiling the available evidence focused on the influence of flap design, including envelope flap (EF), triangular flap (TF), and modified triangular flap (MTF), on postoperative pain, swelling, and trismus, as primary outcome measures, and any result mentioning healing promotion or delay, as secondary outcome measure, after mandibular third molar extraction surgery. An electronic search, complemented by a manual search, of articles published from 1999 to 2020 was conducted in the Medline (PubMed), EMBASE and Web of Science databases including human randomized controlled trials, prospective, and retrospective studies with at least 15 patients. The risk of bias of the included studies was assessed either with the Cochrane’s Risk of Bias tool or with the Newcastle-Ottawa scale. Every step of the review was performed independently and in duplicate. The initial electronic search recovered 2102 articles. After applying the inclusion criteria, 12 articles were included. For patient’s perceived postoperative pain, TF and MTF frequently reported better results than EF. For swelling, the literature is divided, despite a trend favoring EF. For trismus, data showed that its occurrence is mostly associated with the duration of the surgery rather than with the chosen flap. For healing, the limited data is inconclusive. Finally, randomized studies showed a high risk of bias, whereas nonrandomized studies were mostly of good quality and low risk of bias. Although there was no clear consensus regarding the influence of different flap designs for third mandibular molar extraction on postoperative clinical morbidities; the surgeon’s experience, estimated surgical difficulty, molar position and orientation, and surg ery duration should be considered when choosing among the different flap designs.

Molar, third; Surgery, oral; Tooth extraction; Surgical flaps; Pain; Swelling; Trismus

Introduction

Impacted teeth refer to a particular anatomical condition in which a tooth fails to erupt within the expected time of physiological development. Third molars are the most common impacted teeth, present in almost 77% of people, and its extraction is the most common oral surgical procedure.11 - Carter K, Worthington S. Morphologic and demographic predictors of third molar agenesis: a systematic review and meta-analysis. J Dent Res. 2015;94(7):886-94. doi: 10.1177/0022034515581644
https://doi.org/10.1177/0022034515581644...
In fact, 33% of the population has at least one impacted third molar, which frequently leads to food retention, caries, pain, edema, and second molar root resorption and, consequently, its surgical extraction.22 - Arta SA, Pourabbas Kheyradin R, Mesgarzadeh AH, Hassanbaglu B. Comparison of the influence of two flap designs on periodontal healing after surgical extraction of impacted third molars. J Dent Res Dent Clin Dent Prospects. 2011;5(1):1-4. doi: 10.5681/joddd.2011.001
https://doi.org/10.5681/joddd.2011.001...
,33 - Suarez-Cunqueiro MM, Gutwald R, Reichman J, Otero-Cepeda XL, Schmelzeisen R. Marginal flap versus paramarginal flap in impacted third molar surgery: a prospective study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003;95(4):403-8. doi: 10.1067/moe.2003.84
https://doi.org/10.1067/moe.2003.84...
Despite the frequent surgical removal of third molars, the occurrence of accompanying postoperative morbidities is relatively common.22 - Arta SA, Pourabbas Kheyradin R, Mesgarzadeh AH, Hassanbaglu B. Comparison of the influence of two flap designs on periodontal healing after surgical extraction of impacted third molars. J Dent Res Dent Clin Dent Prospects. 2011;5(1):1-4. doi: 10.5681/joddd.2011.001
https://doi.org/10.5681/joddd.2011.001...
,33 - Suarez-Cunqueiro MM, Gutwald R, Reichman J, Otero-Cepeda XL, Schmelzeisen R. Marginal flap versus paramarginal flap in impacted third molar surgery: a prospective study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003;95(4):403-8. doi: 10.1067/moe.2003.84
https://doi.org/10.1067/moe.2003.84...
The invasive manipulation of soft and hard tissues during tooth extraction involves different factors that can influence the patient’s postoperative course in terms of pain, swelling, trismus, and healing.44 - Monaco G, Dapril G, Tavernse L, Corinadelsi G, Marchetti C. Mandibular third molar removal in young patients: an evaluation of 2 different flap designs. J Oral Maxillofac Surg. 2009;67(1):15-21. doi: 10.1016/j.joms.2007.05.032
https://doi.org/10.1016/j.joms.2007.05.0...
In this context, the selection of the surgical access flap can affect the post operative outcomes following third molar surgery, including many complications.

Among the available surgical access flaps for third molar surgery, the envelope flap (EF) consists of a linear incision along the top of the alveolar ridge distal to the second mandibular molar, followed by an intrasulcular incision that extends from the distal of the second molar up to, sometimes, the first mandibular molar (Figure 1A), the triangular flap (TF) differs from EF by incorporating a vertical or oblique relief incision in the middle of the second molar vestibular wall, after the intrasulcular incision that reaches 1/3 or 2/3 of its vestibular wall (Figure 1B). Similarly, the modified triangular flap (MTF) starts with an incision from the top of the alveolar crest that reaches the second mandibular molar, but leaves a 2 mm gingival collar around its buccal side, and finishes with a final vertical or oblique relief incision (Figure 1C). Whereas EF uses a single horizontal incision and flap elevation, causing minimal disruption of the vascular supply and facilitating wound closure, TF and MTF use an additional vertical buccal releasing incision, which allows better visibility and accessibility during osteotomy.55 - Chen YW, Lee CT, Hum L, Chuang SK. Effect of flap design on periodontal healing after impacted third molar extraction: a systematic review and meta-analysis. Int J Oral Maxillofac Surg. 2017;46(3):363-72. doi: 10.1016/j.ijom.2016.08.005
https://doi.org/10.1016/j.ijom.2016.08.0...
Thus, with increasing studies favoring the use of specific flap designs while describing the disadvantages of the other designs, consensus regarding the most harmless flap design for third molar extraction has not yet been achieved.

Figure 1
Envelope Flap (A), triangular flap (B) and modified Triangular Flap (C)

Although surgeon’s skills and experience often lead to an uneventful third molar removal, this rather invasive intervention is always accompanied by different degrees of postoperative pain, swelling, and trismus. Indeed, individuals that have undergone third molar surgery are frequently impeded to perform their everyday activities. Besides, this surgery is often done on otherwise healthy young people with no history of previous surgeries. Thus, third molar surgical extraction could influence patient’s perceived well-being in different manners, including psychological and social factors affected by pain and discomfort, and consequently on patient’s quality of life. Therefore, this systematic review aimed at analyzing the influence of flap design (intervention), including EF, TF, and MTF (comparison), in mandibular third molar surgery (patient) on the patient’s perceived postoperative pain, swelling, and trismus, considered as primary outcome measures, and any mention of healing promotion or delay, such as the presence of dehiscence or wound gaps, alveolar osteitits, or periodontal health compromise by probing depth augmentation, etc. as secondary outcome measure (outcomes).

Methodology

Protocol

The protocol for executing this scoping systematic review, including selection, extraction, and risk of bias assessment phases, was approved a priori by all the authors and was constructed following the recommendations of the PRISMA-P checklist, with no posterior amendments.66 - Moher D, Shamseer L, Clarke M, Ghersi D, Liberati A, Petticrew M, et al. Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement. Syst Rev. 2015;4(1):1. doi: 10.1186/2046-4053-4-1
https://doi.org/10.1186/2046-4053-4-1...
In addition, for the reporting of this systematic review, the PRISMA Statement was followed accordingly. The formulated focused PICO research question was the following: “In patients (P) that require mandibular third molar surgery (I) is there a difference among performing EP, TF, or MTF (C) regarding patient’s perceived postoperative pain, swelling, trismus, and healing (O)?

Eligibility criteria

To answer the PICO research question, the inclusion and exclusion criteria were: Randomized controlled trials (RCTs) and nonrandomized prospective or retrospective studies performed in humans, including at least 15 patients treated for third molar extraction, comparing at least two flap designs (EP, TF, or MTF), evaluating at least two patient’s postoperative clinical outcomes, including pain reported using a visual analogue scale (VAS), swelling estimated by measuring the operation area before and after the procedure, trismus estimated by measuring the mouth opening distance before and after the procedure, and any mention of healing promotion or delay, such as the presence of dehiscence or wound gaps, alveolar osteitis, or periodontal health compromise by probing depth augmentation, and published in English. Publication status or grey literature were not considered as exclusion criteria.

Literature search

A search strategy using the combination of free-text words including: "Mandibular third molar surgery", "mandibular third molar flap design", "envelope flap ", "triangular flap", "modified triangular flap", was performed in the Medline (PubMed), EMBASE, and Web of Science databases up to May 2020. In addition, the search on the included studies references was complemented manually. If data were missing, corresponding authors were reached via e-mail.

Data selection and extraction

Data selection (F.D and G.D) and extraction (F.D and CM.C) were performed by two authors, independently. First, titles and abstracts were assessed for potential inclusion. Then, full-text articles were evaluated against the inclusion criteria. The inclusion and exclusion of studies were decided by consensus between the two authors in every step of the selection phase. If disagreements occurred, inclusion or exclusion of the studies was consulted with a third author (A.L). Data extraction was performed in a pre-designed sheet by collecting the following data: Authors, study design, number of patients, flap design, the position of the extracted third molars, according to the Pell and Gregory classification,77 - Pell GJ, Gregory GT. Impacted mandibular third molars: classification and modified techniques for removal. Dent Digest. 1933;39(9):330-8. follow-up period, and patient’s reported postoperative clinical outcomes.

Risk of bias and quality of the studies assessment

The risk of bias of the included studies was evaluated independently and in duplicate by two reviewers (G.D and F.D). To analyze randomized controlled trials, the Cochrane risk of bias tool, analyzing selection, performance, detection, attrition, reporting, and other biases, was used by assessing the following parameters: random sequence generation, allocation concealment, blinding of the examiner and/or patient, post-operative follow-up and incomplete outcome data.88 - Higgins JP, Green S, editors. Cochrane handbook for systematic reviews of interventions. Version 5.1.0. London: The Cochrane Collaboration; 2011. Moreover, to analyze nonrandomized clinical studies, the Newcastle – Ottawa Scale (NOS) was used.99 - Wells GA, Shea BJ, O’Connell D, Peterson J, Welch V, Losos M, et al. The Newcastle-Ottawa Scale (NOS) for assessing the quality of non randomised studies in meta-analyses [internet]. 2014 [cited 2020 Jan 15]. Available form: http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp.
http://www.ohri.ca/programs/clinical_epi...
This scale uses a star system, in which a study is judged based on three broad perspectives: The selection of the study groups (up to 4 stars), the comparability of the groups (up to 2 stars), and exposure or outcome of interest for case-control or cohort studies, respectively (up to 3 stars). Studies that met five or more of the Newcastle – Ottawa Scale criteria were considered as low risk of bias and good quality. Finally, data from the included studies were assessed in a qualitative manner.

Results

The initial search identified 2,102 potential items. After reading the titles and abstracts, 41 articles were selected for full-text revision. Then, the full-text analysis excluded 32 studies that did not evaluate at least two of the examined flaps or at least two of the postoperative clinical outcomes. Finally, nine articles were considered eligible. Subsequently, three articles were added after the manual search, leading to a total of 12 articles included in the review,1010 - Alqahtani NA, Khaleelahmed S, Desai F. Evaluation of two flap designs on the mandibular second molar after third molar extraction. J Oral Maxillofac Pathol 2017;21(2):317-8. doi: 10.4103/jomfp.JOMFP_75_17
https://doi.org/10.4103/jomfp.JOMFP_75_1...

11 - Mohajerani H, Esmaeelinejad M, Jafari M, Amini E, Sharabiany S. Comparison of envelope and modified triangular flaps on incidence of dry socket after surgical removal of impacted mandibular third molars: a double-blind, split-mouth study. J Contemp Dent Pract. 2018;19(7):836-41.

12 - Mobilio N, Vecchiatini R, Vasquez M, Calura G, Catapano S. Effect of flap design and duration of surgery on acute postoperative symptoms and signs after extraction of lower third molars: a randomized prospective study. J Dent Res Clin Sent Prospects. 2017;11(3):156-0. doi: 10.15171/joddd.2017.028
https://doi.org/10.15171/joddd.2017.028...

13 - Rabi A, Haris PM, Panickal DM, Ahamed S, Pulikkottil VJ, Haris KT. Comparative evaluation of two different flap designs and postoperative outcome in the surgical removal of impacted mandibular third molar. J Contemp Dent Pract. 2017;18(9):807-11. doi: 10.5005/jp-journals-10024-2131
https://doi.org/10.5005/jp-journals-1002...

14 - Desai A, Patel R, Desai K, Vachhani NB, Shah KA, Sureja R. Comparison of two incision designs for surgical removal of impacted mandibular third molar: a randomized comparative clinical study. Contemp Clin Dent. 2014;5(2):170-4. doi: 10.4103/0976-237X.132308
https://doi.org/10.4103/0976-237X.132308...

15 - Koyuncu BÖ, Cetingül E. Short-term clinical outcomes of two different flap techniques in impacted mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(3):179-84. doi: 10.1016/j.oooo.2011.12.023
https://doi.org/10.1016/j.oooo.2011.12.0...

16 - Baqain ZH, Al-Shafii A, Hamdan AA, Sawair FA. Flap design and mandibular third molar surgery: a split mouth randomized clinical study. Int J Oral Maxillofac Surg. 2012;41(8):1020-4. doi: 10.1016/j.ijom.2012.02.011
https://doi.org/10.1016/j.ijom.2012.02.0...

17 - Erdogan O, Tatlı U, Ustün Y, Damlar I. Influence of two different flap designs on the sequelae of mandibular third molar surgery. Oral Maxillofac Surg. 2011;15(3):147-52. doi: 10.1007/s10006-011-0268-7
https://doi.org/10.1007/s10006-011-0268-...

18 - Sandhu A, Sandhu S, Kaur T. Comparison of two different flap designs in the surgical removal of bilateral impacted mandibular third molars. Int J Oral Maxillofac Surg. 2010;39(11):1091-6. doi: 10.1016/j.ijom.2010.07.003
https://doi.org/10.1016/j.ijom.2010.07.0...

19 - Kirk DG, Liston PN, Tong DC, Love RM. Influence of two different flap designs on incidence of pain, swelling, trismus, and alveolar osteitis in the week following third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;104(1):1-6. doi: 10.1016/j.tripleo.2007.01.032
https://doi.org/10.1016/j.tripleo.2007.0...

20 - Dolanmaz D, Esen A, Isik K, Candirli C. Effect of 2 flap designs on postoperative pain and swelling after impacted third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(4):244-6. doi: 10.1016/j.oooo.2011.11.030
https://doi.org/10.1016/j.oooo.2011.11.0...
-2121 - Saima M, Muslim K, Sana W. Outcome of envelope and triangular flap design in surgical management of impacted mandibular third molar. JKCD. 2017;7(1):2. as shown in the data selection flow chart (Figure 2). The data regarding the number of patients, the examined flaps, and clinical outcomes are shown in Table 1 and Table 2.

Figure 2
PRISMA Flow chart for the data selection process

Table 1
Descriptive summary of included studies
Table 2
Reported differences between postoperative occurrence of pain, swelling, trismus and healing after using different access flap designs for third molar surgery in the included studies

Flap selection effect over postoperative pain

Many authors agree that TF and MTF have better results than EF regarding postoperative pain after third molar surgery;1515 - Koyuncu BÖ, Cetingül E. Short-term clinical outcomes of two different flap techniques in impacted mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(3):179-84. doi: 10.1016/j.oooo.2011.12.023
https://doi.org/10.1016/j.oooo.2011.12.0...
,1818 - Sandhu A, Sandhu S, Kaur T. Comparison of two different flap designs in the surgical removal of bilateral impacted mandibular third molars. Int J Oral Maxillofac Surg. 2010;39(11):1091-6. doi: 10.1016/j.ijom.2010.07.003
https://doi.org/10.1016/j.ijom.2010.07.0...
however, these differences are not all statistically significant.1717 - Erdogan O, Tatlı U, Ustün Y, Damlar I. Influence of two different flap designs on the sequelae of mandibular third molar surgery. Oral Maxillofac Surg. 2011;15(3):147-52. doi: 10.1007/s10006-011-0268-7
https://doi.org/10.1007/s10006-011-0268-...
According to Sandhu,et al.1818 - Sandhu A, Sandhu S, Kaur T. Comparison of two different flap designs in the surgical removal of bilateral impacted mandibular third molars. Int J Oral Maxillofac Surg. 2010;39(11):1091-6. doi: 10.1016/j.ijom.2010.07.003
https://doi.org/10.1016/j.ijom.2010.07.0...
(2010), patients in the EF group experienced significantly more pain as compared to the MTF group (P<0.05). Similarly, Koyuncu and Cetingül1515 - Koyuncu BÖ, Cetingül E. Short-term clinical outcomes of two different flap techniques in impacted mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(3):179-84. doi: 10.1016/j.oooo.2011.12.023
https://doi.org/10.1016/j.oooo.2011.12.0...
(2013) described that MTF-intervened patients also reported less postoperative pain. Kirk, et al.1919 - Kirk DG, Liston PN, Tong DC, Love RM. Influence of two different flap designs on incidence of pain, swelling, trismus, and alveolar osteitis in the week following third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;104(1):1-6. doi: 10.1016/j.tripleo.2007.01.032
https://doi.org/10.1016/j.tripleo.2007.0...
(2007), in turn, showed no statistically significant differences between the EF and MTF groups regarding pain.

Although EF is the most commonly used surgical approach for lower third molar removal, the extensive exposition of buccal bone from the adjacent second molar during this procedure has been frequently associated with patients perceiving more pain, when compared with the other less invasive approaches.1515 - Koyuncu BÖ, Cetingül E. Short-term clinical outcomes of two different flap techniques in impacted mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(3):179-84. doi: 10.1016/j.oooo.2011.12.023
https://doi.org/10.1016/j.oooo.2011.12.0...
This could be also attributed to the incision, the damage to the second molar periodontal tissues, the reflection of the mucoperiosteal flap, and the removal of bone during the procedure. Moreover, the occurrence of wound dehiscences at the distofacial edge of the second molar and the length of the surgical procedure could also lead to a prolonged period of discomfort and pain. Besides, experience of the surgeon, type of impact, administration of preoperative or postoperative corticosteroids, and compliance to postoperative instructions could also affect the pain experienced by the patient.1717 - Erdogan O, Tatlı U, Ustün Y, Damlar I. Influence of two different flap designs on the sequelae of mandibular third molar surgery. Oral Maxillofac Surg. 2011;15(3):147-52. doi: 10.1007/s10006-011-0268-7
https://doi.org/10.1007/s10006-011-0268-...
,1818 - Sandhu A, Sandhu S, Kaur T. Comparison of two different flap designs in the surgical removal of bilateral impacted mandibular third molars. Int J Oral Maxillofac Surg. 2010;39(11):1091-6. doi: 10.1016/j.ijom.2010.07.003
https://doi.org/10.1016/j.ijom.2010.07.0...
Finally, most articles agreed that pain was the most frequently reported comorbidity, mostly on the immediate days after surgery, and that it decreased continuously over the healing course, regardless of the surgical technique. Since it requires a soft diet and several rest days, it negatively affects patient’s daily routine and, consequently, the patient’s quality of life.2222 - Larsen MK, Kofod T, Starch-Jensen T. Therapeutic efficacy of cryotherapy on facial swelling, pain, trismus and quality of life after surgical removal of mandibular third molars: a systematic review. J Oral Rehabil. 2019;46(6):563-73. doi: 10.1111/joor.12789
https://doi.org/10.1111/joor.12789...

Flap selection effect over postoperative swelling

Alqahtani, Khaleelahmed and Desai1010 - Alqahtani NA, Khaleelahmed S, Desai F. Evaluation of two flap designs on the mandibular second molar after third molar extraction. J Oral Maxillofac Pathol 2017;21(2):317-8. doi: 10.4103/jomfp.JOMFP_75_17
https://doi.org/10.4103/jomfp.JOMFP_75_1...
(2017) compared EF and MTF during third molar surgery, showing significantly better outcomes for the EF group regarding postoperative swelling. Similarly, Baqain, et al.1616 - Baqain ZH, Al-Shafii A, Hamdan AA, Sawair FA. Flap design and mandibular third molar surgery: a split mouth randomized clinical study. Int J Oral Maxillofac Surg. 2012;41(8):1020-4. doi: 10.1016/j.ijom.2012.02.011
https://doi.org/10.1016/j.ijom.2012.02.0...
(2012) reported that patients intervened with EF, when compared with TF, showed significantly less postoperative swelling. On the other hand, Dolanmaz, et al.2020 - Dolanmaz D, Esen A, Isik K, Candirli C. Effect of 2 flap designs on postoperative pain and swelling after impacted third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(4):244-6. doi: 10.1016/j.oooo.2011.11.030
https://doi.org/10.1016/j.oooo.2011.11.0...
(2013) showed no significant differences regarding swelling when comparing patients treated with an EF approach and with an MTF approach. Sandhu, Sandhu and Kaur1818 - Sandhu A, Sandhu S, Kaur T. Comparison of two different flap designs in the surgical removal of bilateral impacted mandibular third molars. Int J Oral Maxillofac Surg. 2010;39(11):1091-6. doi: 10.1016/j.ijom.2010.07.003
https://doi.org/10.1016/j.ijom.2010.07.0...
(2010) also claimed that there was no difference in postoperative swelling between the patients treated with EF and those treated with MTF. Koyuncu and Cetingül1515 - Koyuncu BÖ, Cetingül E. Short-term clinical outcomes of two different flap techniques in impacted mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(3):179-84. doi: 10.1016/j.oooo.2011.12.023
https://doi.org/10.1016/j.oooo.2011.12.0...
(2013) and Kirk, et al.1919 - Kirk DG, Liston PN, Tong DC, Love RM. Influence of two different flap designs on incidence of pain, swelling, trismus, and alveolar osteitis in the week following third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;104(1):1-6. doi: 10.1016/j.tripleo.2007.01.032
https://doi.org/10.1016/j.tripleo.2007.0...
(2007), in turn, reported less swelling among the patients treated with the MTF approach when compared with the EF group; however, these differences were not statistically significant. Despite the considerable trend favoring that the EF approach could lead to less postoperative swelling after third molar extraction, the literature available is divided.

TF and MTF association with increased facial swelling could be explained, at least partly, by the buccal releasing incision, which provokes increased local inflammation and subsequent edema in the buccal tissues.1010 - Alqahtani NA, Khaleelahmed S, Desai F. Evaluation of two flap designs on the mandibular second molar after third molar extraction. J Oral Maxillofac Pathol 2017;21(2):317-8. doi: 10.4103/jomfp.JOMFP_75_17
https://doi.org/10.4103/jomfp.JOMFP_75_1...
,1616 - Baqain ZH, Al-Shafii A, Hamdan AA, Sawair FA. Flap design and mandibular third molar surgery: a split mouth randomized clinical study. Int J Oral Maxillofac Surg. 2012;41(8):1020-4. doi: 10.1016/j.ijom.2012.02.011
https://doi.org/10.1016/j.ijom.2012.02.0...
In fact, surgical incisions extension and quantity of bone removal have been associated with the severity of facial swelling. Furthermore, the incidence of facial swelling also depends on the type of third molar impact, the difficulty of extraction operation, and the oral hygiene of the patient. Although many studies have attempted to determine predictive factors and preventive interventions for facial swelling, inconsistency between the results compromises patients’ perception of the quality of the dentist’s service, follow-up, and of their own quality of life.2323 - Zhang W, Li J, Li ZB, Li Z. Predicting postoperative facial swelling following impacted mandibular third molars extraction by using artificial neural networks evaluation. Sci Rep. 2018;16;8(1):12281. doi: 10.1038/s41598-018-29934-1
https://doi.org/10.1038/s41598-018-29934...

Flap effect over postoperative trismus

Erdogan, et al.1717 - Erdogan O, Tatlı U, Ustün Y, Damlar I. Influence of two different flap designs on the sequelae of mandibular third molar surgery. Oral Maxillofac Surg. 2011;15(3):147-52. doi: 10.1007/s10006-011-0268-7
https://doi.org/10.1007/s10006-011-0268-...
(2011) reported that there were no statistically significant differences between the EF and TF groups regarding trismus. Similarly, Sandhu, Sandhu and Kaur1818 - Sandhu A, Sandhu S, Kaur T. Comparison of two different flap designs in the surgical removal of bilateral impacted mandibular third molars. Int J Oral Maxillofac Surg. 2010;39(11):1091-6. doi: 10.1016/j.ijom.2010.07.003
https://doi.org/10.1016/j.ijom.2010.07.0...
(2010) and Kirk, et al.1919 - Kirk DG, Liston PN, Tong DC, Love RM. Influence of two different flap designs on incidence of pain, swelling, trismus, and alveolar osteitis in the week following third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;104(1):1-6. doi: 10.1016/j.tripleo.2007.01.032
https://doi.org/10.1016/j.tripleo.2007.0...
(2007) showed no differences in the occurrence of postoperative trismus between patients approached with EF and those approached with MTF. Conversely, Baqain, et al.1616 - Baqain ZH, Al-Shafii A, Hamdan AA, Sawair FA. Flap design and mandibular third molar surgery: a split mouth randomized clinical study. Int J Oral Maxillofac Surg. 2012;41(8):1020-4. doi: 10.1016/j.ijom.2012.02.011
https://doi.org/10.1016/j.ijom.2012.02.0...
(2012) showed a statically significant difference favoring TF over EF group regarding trismus. Nevertheless, Mobilio, et al.1212 - Mobilio N, Vecchiatini R, Vasquez M, Calura G, Catapano S. Effect of flap design and duration of surgery on acute postoperative symptoms and signs after extraction of lower third molars: a randomized prospective study. J Dent Res Clin Sent Prospects. 2017;11(3):156-0. doi: 10.15171/joddd.2017.028
https://doi.org/10.15171/joddd.2017.028...
(2017) showed that the duration of surgery, and not the flap design, was associated with the acute postoperative symptoms, including trismus, after lower third molar extraction. Thus, the analyzed data showed that the occurrence of trismus could be associated with the duration of the surgery, although patients treated with TF or MTF flaps presented fewer trismus events.

Traumatic manipulation of tissues during third molar extraction can lead to trismus. Mouth opening length reduction accompanied by a decrease of masticatory muscle activity has been frequently reported after third molar surgery. Indeed, the reduction of muscular activity on the intervened site has been considered as an innate protective and analgesic function to diminish pain. Moreover, direct muscle damage and acute inflammation may provoke adjacent muscle spasms and lead to limited mouth opening.2424 - Buesa-Bárez JM, Martin-Ares M, Martínez-Rodriguez N, Barona-Dorado C, Sanz-Alonso J, Cortés-Bretón-Brinkmann J, et al. Masseter and temporalis muscle electromyography findings after lower third molar extraction. Med Oral Patol Oral Cir Bucal. 2018;1;23(1):e92-e97. doi: 10.4317/medoral.21992
https://doi.org/10.4317/medoral.21992...
Finally, trismus-provoked dysphagia is also a frequent undesired effect of third molar surgery, which negatively affects patient’ s quality of life by limiting conventional eating and requiring unpleasant soft or liquid diets.2525 - Ortigara GB, Schulz RE, Soldera EB, Bonzanini LIL, Danesi CC, Antoniazzi RP, et al. Association between trismus and dysphagia-related quality of life in survivors of head and neck cancer in Brazil. Oral Surg Oral Med Oral Pathol Oral Radiol. 2019;128(3):235-42. doi: 10.1016/j.oooo.2019.05.009
https://doi.org/10.1016/j.oooo.2019.05.0...

Flap effect over tissue healing

Healing is often not reported as a clinical parameter after third molar surgery; however, the few articles analyzing healing showed better healing in patients treated with the MTF approach.1111 - Mohajerani H, Esmaeelinejad M, Jafari M, Amini E, Sharabiany S. Comparison of envelope and modified triangular flaps on incidence of dry socket after surgical removal of impacted mandibular third molars: a double-blind, split-mouth study. J Contemp Dent Pract. 2018;19(7):836-41.,1414 - Desai A, Patel R, Desai K, Vachhani NB, Shah KA, Sureja R. Comparison of two incision designs for surgical removal of impacted mandibular third molar: a randomized comparative clinical study. Contemp Clin Dent. 2014;5(2):170-4. doi: 10.4103/0976-237X.132308
https://doi.org/10.4103/0976-237X.132308...
,1818 - Sandhu A, Sandhu S, Kaur T. Comparison of two different flap designs in the surgical removal of bilateral impacted mandibular third molars. Int J Oral Maxillofac Surg. 2010;39(11):1091-6. doi: 10.1016/j.ijom.2010.07.003
https://doi.org/10.1016/j.ijom.2010.07.0...
Mohajerani, et al.1111 - Mohajerani H, Esmaeelinejad M, Jafari M, Amini E, Sharabiany S. Comparison of envelope and modified triangular flaps on incidence of dry socket after surgical removal of impacted mandibular third molars: a double-blind, split-mouth study. J Contemp Dent Pract. 2018;19(7):836-41. (2018) showed that the application of MTF might lead to a reduction in dry socket incidence and better healing 7 days after lower-impacted third molar surgeries. On the other hand, Desai, et al.1414 - Desai A, Patel R, Desai K, Vachhani NB, Shah KA, Sureja R. Comparison of two incision designs for surgical removal of impacted mandibular third molar: a randomized comparative clinical study. Contemp Clin Dent. 2014;5(2):170-4. doi: 10.4103/0976-237X.132308
https://doi.org/10.4103/0976-237X.132308...
(2014) reported no statistical differences between EF and TF-treated patients in the healing of flap due to presence of gaps, hematoma, sensitivity of adjacent teeth, and dry socket. When considering the initial phases of healing, alveolar osteitis (AO) can be considered as a relatively frequent complication. In this context, Koyuncu and Cetingül1515 - Koyuncu BÖ, Cetingül E. Short-term clinical outcomes of two different flap techniques in impacted mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(3):179-84. doi: 10.1016/j.oooo.2011.12.023
https://doi.org/10.1016/j.oooo.2011.12.0...
(2013) found no differences between the incidence of AO when using either EF or MTF approaches. Interestingly, Elo, et al.2626 - Elo JA, Sun HH, Dong F, Tandon R, Singh HM. Novel incision design and primary flap closure reduces the incidence of alveolar osteitis and infection in impacted mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2016;122(2):124-33. doi: 10.1016/j.oooo.2016.01.024
https://doi.org/10.1016/j.oooo.2016.01.0...
(2016) proposed a modified approach by incorporating a double-pass single-layered running continuous primary closure to provide a tighter protection of the clot. The modified flap design, which consisted in a sulcular incision starting at the midfacial portion of the second molar and extending distolaterally across the lateral body or ramus of the mandible, resulted in a significantly less risk of developing AO and other complications when compared with both the traditional EF and MTF designs.

Clinical healing delay negatively affects patient’s oral health-related quality of life recovery, and has been associated with symptomatic third molars and surgical difficulty.2727 - Ruvo AT, Shugars DA, White RP Jr, Phillips C. The impact of delayed clinical healing after third molar surgery on health-related quality-of-life outcomes. J Oral Maxillofac Surg. 2005;63(7):929-35. doi: 10.1016/j.joms.2005.03.007
https://doi.org/10.1016/j.joms.2005.03.0...
Besides, surgical extraction of unerupted impacted third molars can damage to the second molar periodontium permanently. However, a recent meta-analysis found variations in second molar probing depth around 1 mm, only during the first three months after surgery, thus having a limited clinical impact.2828 - Chen YW, Lee CT, Hum L, Chuang SK. Effect of flap design on periodontal healing after impacted third molar extraction: a systematic review and meta-analysis. Int J Oral Maxillofac Surg. 2017;46(3):363-72. doi: 10.1016/j.ijom.2016.08.005
https://doi.org/10.1016/j.ijom.2016.08.0...
Moreover, triangular flaps with paramarginal incisions are expected to better preserve second molar periodontal health by leaving an untouched band of keratinized tissue around the second molar.2828 - Chen YW, Lee CT, Hum L, Chuang SK. Effect of flap design on periodontal healing after impacted third molar extraction: a systematic review and meta-analysis. Int J Oral Maxillofac Surg. 2017;46(3):363-72. doi: 10.1016/j.ijom.2016.08.005
https://doi.org/10.1016/j.ijom.2016.08.0...

Risk of bias and quality of the included studies

Tables 3 and 4 shows the outcomes of the risk of bias assessment of included studies. All four RCTs studies1111 - Mohajerani H, Esmaeelinejad M, Jafari M, Amini E, Sharabiany S. Comparison of envelope and modified triangular flaps on incidence of dry socket after surgical removal of impacted mandibular third molars: a double-blind, split-mouth study. J Contemp Dent Pract. 2018;19(7):836-41.,1212 - Mobilio N, Vecchiatini R, Vasquez M, Calura G, Catapano S. Effect of flap design and duration of surgery on acute postoperative symptoms and signs after extraction of lower third molars: a randomized prospective study. J Dent Res Clin Sent Prospects. 2017;11(3):156-0. doi: 10.15171/joddd.2017.028
https://doi.org/10.15171/joddd.2017.028...
,1414 - Desai A, Patel R, Desai K, Vachhani NB, Shah KA, Sureja R. Comparison of two incision designs for surgical removal of impacted mandibular third molar: a randomized comparative clinical study. Contemp Clin Dent. 2014;5(2):170-4. doi: 10.4103/0976-237X.132308
https://doi.org/10.4103/0976-237X.132308...
,1616 - Baqain ZH, Al-Shafii A, Hamdan AA, Sawair FA. Flap design and mandibular third molar surgery: a split mouth randomized clinical study. Int J Oral Maxillofac Surg. 2012;41(8):1020-4. doi: 10.1016/j.ijom.2012.02.011
https://doi.org/10.1016/j.ijom.2012.02.0...
showed a high risk of bias in one or two key domains. One study showed an unclear risk of bias in both allocation concealment and blinding during the result survey,1414 - Desai A, Patel R, Desai K, Vachhani NB, Shah KA, Sureja R. Comparison of two incision designs for surgical removal of impacted mandibular third molar: a randomized comparative clinical study. Contemp Clin Dent. 2014;5(2):170-4. doi: 10.4103/0976-237X.132308
https://doi.org/10.4103/0976-237X.132308...
whereas all studies showed an unclear risk of bias in at least one of them, as shown in Table 4. The scores of the five nonrandomized studies eligible for the NOS ranged from 5 to 8 stars.1010 - Alqahtani NA, Khaleelahmed S, Desai F. Evaluation of two flap designs on the mandibular second molar after third molar extraction. J Oral Maxillofac Pathol 2017;21(2):317-8. doi: 10.4103/jomfp.JOMFP_75_17
https://doi.org/10.4103/jomfp.JOMFP_75_1...
,1313 - Rabi A, Haris PM, Panickal DM, Ahamed S, Pulikkottil VJ, Haris KT. Comparative evaluation of two different flap designs and postoperative outcome in the surgical removal of impacted mandibular third molar. J Contemp Dent Pract. 2017;18(9):807-11. doi: 10.5005/jp-journals-10024-2131
https://doi.org/10.5005/jp-journals-1002...
,1515 - Koyuncu BÖ, Cetingül E. Short-term clinical outcomes of two different flap techniques in impacted mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(3):179-84. doi: 10.1016/j.oooo.2011.12.023
https://doi.org/10.1016/j.oooo.2011.12.0...
,1717 - Erdogan O, Tatlı U, Ustün Y, Damlar I. Influence of two different flap designs on the sequelae of mandibular third molar surgery. Oral Maxillofac Surg. 2011;15(3):147-52. doi: 10.1007/s10006-011-0268-7
https://doi.org/10.1007/s10006-011-0268-...

18 - Sandhu A, Sandhu S, Kaur T. Comparison of two different flap designs in the surgical removal of bilateral impacted mandibular third molars. Int J Oral Maxillofac Surg. 2010;39(11):1091-6. doi: 10.1016/j.ijom.2010.07.003
https://doi.org/10.1016/j.ijom.2010.07.0...

19 - Kirk DG, Liston PN, Tong DC, Love RM. Influence of two different flap designs on incidence of pain, swelling, trismus, and alveolar osteitis in the week following third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;104(1):1-6. doi: 10.1016/j.tripleo.2007.01.032
https://doi.org/10.1016/j.tripleo.2007.0...

20 - Dolanmaz D, Esen A, Isik K, Candirli C. Effect of 2 flap designs on postoperative pain and swelling after impacted third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(4):244-6. doi: 10.1016/j.oooo.2011.11.030
https://doi.org/10.1016/j.oooo.2011.11.0...
-2121 - Saima M, Muslim K, Sana W. Outcome of envelope and triangular flap design in surgical management of impacted mandibular third molar. JKCD. 2017;7(1):2. According to the authors’ definitions, the overall ranking showed no studies with a low risk of bias and that all of them were of good quality.

Table 3
Risk of bias and quality assessment of included nonrandomized studies using the Newcastle-Ottawa Scale

Table 4
Risk of bias assessment of included RCTs using the Cochrane’s Risk of Bias tool

Discussion

Although the removal of mandibular third molars is one of the most common surgical procedures, it is often associated with patients experiencing postoperative complications, such as perceived pain, swelling, and trismus, regardless of the surgical approach.2929 - Warraich R, Fasial M, Shaheen A, Rana M, Gellrich NC. Evaluation of postoperative discomfort following third molar surgery using submucosal dexamethasone - a randomized observer blind prospective study. J Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(1):16-22. doi: 10.1016/j.oooo.2012.12.007
https://doi.org/10.1016/j.oooo.2012.12.0...
Thus, this review aimed at investigating if the use of different flaps design (EF, TF or MTF) for third molar surgery influenced patients’ perceived postoperative clinical occurrences.

Each of the three analyzed flaps has particular advantages and disadvantages.3030 - Obiechina AE. Updates in the technique of third molar surgery. Ann Ib Postgrad Med. 2003;11(1):40-5. doi: 10.4314/aipm.v1i1.39100.
https://doi.org/10.4314/aipm.v1i1.39100...
According to Mohajerani, et al.1111 - Mohajerani H, Esmaeelinejad M, Jafari M, Amini E, Sharabiany S. Comparison of envelope and modified triangular flaps on incidence of dry socket after surgical removal of impacted mandibular third molars: a double-blind, split-mouth study. J Contemp Dent Pract. 2018;19(7):836-41. (2018), the decrease in surgical complications following third molar surgery is an important issue, which could be achieved by designing an appropriate flap. Different clinical studies have reported the advantages of using TF and MTF approaches,1515 - Koyuncu BÖ, Cetingül E. Short-term clinical outcomes of two different flap techniques in impacted mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(3):179-84. doi: 10.1016/j.oooo.2011.12.023
https://doi.org/10.1016/j.oooo.2011.12.0...
,3131 - Karaca I, Simşek S, Uğar D, Bozkaya S. Review of flap design influence on the health of the periodontium after mandibular third molar surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;104(1):18-23. doi: 10.1016/j.tripleo.2006.11.049
https://doi.org/10.1016/j.tripleo.2006.1...
including an increase in the operative visibility of the surgical site, lower incidence of damage to the flap, and better management of intra operative complications, especially for a less experienced surgeon. In the case of the EF approach, its main advantage is less intraoperative bleeding due to the less surgical invasiveness, and to the fewer damage to the periosteum and buccinator muscle.

Patients’ experiencing negative postoperative outcomes could be decreased if surgical decision-making was based on tooth radiographic location and orientation. Despite being dated, the most accredited third molar inclusion classifications are the Classification of Winter from 19263232 - Winter GB. Principles of exodontia as applied to the impacted third molar. Yale J Biol Med. 1928;1(1):63. and Classification of Pell and Gregory from 1933.77 - Pell GJ, Gregory GT. Impacted mandibular third molars: classification and modified techniques for removal. Dent Digest. 1933;39(9):330-8. Winter classified the impacted teeth according to their angulation in vertical, horizontal, mesioangular, and distoangular.3333 - Khojastepour L, Khaghaninejad MS, Hasanshahi R, Forghani M, Ahrari F. Does the Winter or Pell and Gregory Classification System Indicate the Apical Position of Impacted Mandibular Third Molars? J Oral Maxillofac Surg. 2019;77:2222.e1-2222.e9. doi:10.1016/j.joms.2019.06.004
https://doi.org/10.1016/j.joms.2019.06.0...
Alternatively, Pell and Gregory classified the impacted teeth according to their relation with the second molar occlusal plane, in classes A, B, and C, and according to their proximity to the anterior border of the mandibular ramus, in classes I, II, and III.77 - Pell GJ, Gregory GT. Impacted mandibular third molars: classification and modified techniques for removal. Dent Digest. 1933;39(9):330-8. Different clinical approaches have been recommended depending on tooth position; the MTF is suggested for impacted mandibular third molars in Class 3-Position C, whereas the EF approach is recommended for teeth in Class 1-Position A. However, intermediate classes and positions, i.e. combinations including Class 2 and Position B, are not the most frequently reported.3333 - Khojastepour L, Khaghaninejad MS, Hasanshahi R, Forghani M, Ahrari F. Does the Winter or Pell and Gregory Classification System Indicate the Apical Position of Impacted Mandibular Third Molars? J Oral Maxillofac Surg. 2019;77:2222.e1-2222.e9. doi:10.1016/j.joms.2019.06.004
https://doi.org/10.1016/j.joms.2019.06.0...
In these cases, the choice of the access flap is determined by the estimated difficulty of the intervention, by considering the depth of the inclusion and the position of the third mandibular molar. Indeed, based on the preoperative data, the Pederson’s scale was used to define the level of difficulty of all extractions before the surgery, classifying them as easy, moderately difficult, or very difficult.3434 - Diniz-Freitas M, Lago-Mendez L, Gude-Sampedro F, Somoza-Martin JM, Gandara-Rey JM, Garcia-Garcia A. Pederson scale fails to predict how difficult it will be to extract lower third molars. Brit J Oral Maxillofac Surg. 2007;45(1):23-6. doi: 10.1016/j.bjoms.2005.12.004 When Pederson’s scale is easy, the EF approach is chosen and, when preoperative Pederson's scale is moderately difficult or difficult, the use of TF or MTF is preferred.

According to two recent systematic reviews, Lopes da Silva, et al.3535 - Lopes da Silva BC, Machado GF, Primo Miranda EF, Galvão EL, Falci SG. Envelope or triangular flap for surgical removal of third molars? A systematic review and meta-analysis. Int J Oral Maxillofac Surg. 2020;49(8):1073-86. doi: 10.1016/j.ijom.2020.01.001 (2020) and Glera-Suárez, et al.3636 - Glera-Suárez P, Soto-Peñaloza D, Peñarrocha-Oltra D, Peñarrocha-Diago M. Patient morbidity after impacted third molar extraction with different flap designs. A systematic review and meta-analysis. Med Oral Patol Oral Cir Bucal. 2020;25(2):e233-e239. doi: 10.4317/medoral.23320
https://doi.org/10.4317/medoral.23320...
(2020), there are no statistically significant differences regarding postoperative clinical morbidities when comparing the use of different access flaps for third mandibular molar surgery in the literature when assessing RCTs. In the context of our study, when assessing intervention and observational studies, substantial heterogeneity was found among the included studies. In fact, their results could be influenced by different parameters, such as patients characteristics (sex and age), intervention features (surgeon experience, surgical materials, and duration of surgery), and outcome measures (pain rating scale, swelling assessment methods, outcomes, and follow-up). These limitations are often found when comparing clinical trials in Dentistry,3737 - Saltaji H, Armijo-Olivo S, Cummings GG, Amin M, Costa BR, Flores-Mir C. Impact of selection bias on treatment effect size estimates in randomized trials of oral health interventions: a meta-epidemiological study. J Dent Res 2018;97(1):5-13. doi: 10.1177/0022034517725049
https://doi.org/10.1177/0022034517725049...
,3838 - Saltaji H, Armijo-Olivo S, Cummings GG, Amin M, Flores-Mir C. Randomized clinical trials in dentistry: risks of bias, risks of random errors, reporting quality, and methodologic quality over the years 1955–2013. PLoS One. 2017;12(12):e0190089. doi: 10.1371/journal.pone.0190089
https://doi.org/10.1371/journal.pone.019...
impeding the performance of an adequate quantitative analysis in systematic reviews, such as the case of our investigation. We suggest that future research should consider the standardization of the outcome measures for evaluating postoperative events, clear patient selection, and similar operator experience. Finally, an estimated surgical difficulty and probability of tissue damage, based on a reliable radiographic tooth position and orientation classification, should be considered to establish a defined surgical protocol for third mandibular molar extraction, with minimal postoperative complications.

Conclusion

There was no clear consensus among the reviewed studies that a particular flap design for third mandibular molar surgery could have advantages regarding patient’s perceived postoperative clinical morbidities. Cumulative evidence suggest that flap selection association to surgical difficulties is mainly determined by impacted tooth position. In fact, the tissue manipulation performed during flaps, which leads to patient’s discomfort, aims to increase surgical visibility area and further reduce surgical time. Thus, a flap design is chosen based on surgeon’ s experience, molar position and orientation and, finally, these characteristics along with the duration of the surgical procedure, directly affect patients’ postoperative experience.

Acknowledgements

EAC was a recipient of a PhD Scholarship from the Graduate School of the Faculty of Dentistry, Universidad de Chile.

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Publication Dates

  • Publication in this collection
    04 June 2021
  • Date of issue
    2021

History

  • Received
    9 Nov 2020
  • Reviewed
    6 Feb 2021
  • Accepted
    11 Feb 2021
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