Flap design and mandibular third molar surgery: a split mouth randomized clinical study


The aim of this study was to investigate the effects of two commonly used flap designs (envelope and triangular) used for the removal of mandibular third molars (M3) on postoperative morbidity. 19 patients with bilateral symmetrically impacted mandibular M3 were studied using a split mouth design. Swelling, pain and trismus measures were recorded on days 2, 7 and 14; periodontal indices were recorded on days 7 and 14, one final measure of probing depth on the distal aspect of the mandibular second molar (M2) was taken at the last follow up appointment. Data were analysed using the χ 2 test, the Mann–Whitney U -test and Pearson’s correlations. The mean age of the patients was 21.4 ± 2.3 years (± SD). Facial swelling and the reduction in mouth opening were significantly greater in the early postoperative period ( P < 0.05) with pyramidal flap designs. There was no significant difference in pain scores, plaque accumulation and bleeding on probing indices between the two flap designs ( P > 0.05). Probing depth was significantly greater with envelope flaps in the early postoperative period ( P < 0.005). In conclusion, flap design in mandibular M3 surgery has an effect on postoperative recovery.

Third molars (M3) are the most commonly impacted teeth and their surgical removal is one of the most common surgical procedures performed by oral and maxillofacial surgeons. Surgical removal of impacted mandibular M3 requires raising a mucoperiosteal flap and occasionally ostectomy. This common procedure carries well known potential complications ; one often overlooked complication is compromised periodontal status of the adjacent second molar. Different flap designs have been suggested for the surgical removal of mandibular M3 to minimize the patients’ discomfort and to prevent periodontal complications.

The aim of this study is to compare two flap designs; a buccal envelope flap and a triangular, three cornered, flap. A prospective randomized split mouth study was conducted investigating postoperative morbidity, pain, swelling, trismus, alveolar osteitis, wound infection and the periodontal health of the adjacent second molar (M2).

Materials and methods

Patients scheduled for surgical removal of mandibular M3 in the Oral and Maxillofacial Surgery (OMFS) unit at Jordan University Hospital (JUH) were considered for inclusion in this study. Panoramic radiographs were taken to assess M3 eruption and angulation versus the adjacent M2. Inclusion criteria included symmetrically impacted mandibular M3 with comparable positioning and angulation, in the absence of acute local inflammation or pathology at the time of tooth removal. Exclusion criteria included patients with systemic diseases, pregnancy, lactating females, smokers and patients on medications that would influence the surgical procedure or postoperative wound healing.

Patients were informed about the surgery, postoperative recommendations, and possible complications and signed a consent form indicating their agreement to participate in the study. The flap design and side of operation were randomly assigned using electronic randomization tables with patients numbered according to the order in which they presented for surgery. The time interval between the two sides was at least 2 weeks. The study protocol was approved by the JUH Research Board (protocol no 155/2010).

The following variables were studied. Trismus was assessed by measuring the maximum inter-incisal opening to the nearest millimetre using a rigid metric rule; it was calculated as: [(preoperative measurement − postoperative measurement)/preoperative measurement] × 100%. Facial swelling was determined by tape measurements between the tragus and soft tissue pogonion (A), tragus and lateral corner of the mouth (B), lateral corner of the eye and the angle of the mandible (C). The facial measurement was calculated as: (A + B + C)/3, and facial swelling (%) was calculated as: [(postoperative measurement − preoperative measurement)/preoperative measurement] × 100%. Pain was scored on a visual analogue scale (VAS) (0–10, representing no pain to excruciating pain). Periodontal examination of the adjacent M2 included plaque index, bleeding index and probing depth. The latter was measured using a CPITN probe and defined as the distance between the free gingival margin and the bottom of the pocket in millimetres. The presence of alveolar osteitis or wound infection was also recorded. Variables were recorded preoperatively on the day of surgery, and 48 h, 7 and 14 days postoperatively, one final probing depth measure was recorded after a mean of 22 weeks (median 17 weeks). Data were recorded on a special sheet, and all measurements were recorded by a single examiner.

Surgical procedures were performed in the same theatre, by the same operator, using the same surgical instruments, rotary and irrigation devices, and materials. Sedation was initiated, intravenously (IV), with an initial dose of 0.03 mg/kg midazolam; further doses were titred according to the patient’s need. All patients were given 8 mg dexamethasone and 1 g co-amoxiclav IV at induction. Local anaesthesia was applied using 2% lidocaine with 1:100,000 adrenaline by local tissue infiltration and inferior alveolar nerve block. With envelope flaps a sulcular incision was performed from the first to the second mandibular molar with a distal incision along the mandibular ramus ( Fig. 1 ). With triangular flaps, the incision commenced distally from the mandibular ramus to the distobuccal aspect of the second molar, then a sulcular incision starting near the mesiobuccal edge of M2 was made extending to its distal surface, finally a relieving incision was made from the distobuccal aspect of M2, without cutting the interdental papilla, dropping at a slight oblique angle curving forward into the mandibular vestibule ( Fig. 2 ). Bone was removed using a round bur in a straight handpiece under copious irrigation with sterile normal saline.

Fig. 1
Incision for the envelope flap.

Fig. 2
Incision for the triangular flap.

If third molar sectioning was required this was achieved using a fissure bur and a straight elevator. After the tooth was removed, the socket was inspected, dental follicular tissue was curetted, the socket was irrigated copiously with normal saline, the flap was then repositioned and sutured with 4-0 silk. The operation time was noted from the time of incision until the flap was sutured. A gauze pack was pressed against the surgical site for the patient to bite on. All patients’ escorts were given written postoperative instructions and discharge medications (a non-steroidal analgesic for 5 days and a mouth wash).

Statistical analysis

Statistical analysis was performed using SPSS for Windows release 16.0 (SPSS Inc., Chicago, IL, USA). Descriptive statistics were generated. The χ 2 test, Mann–Whitney U -test, and Pearson’s Correlation ( r ) were used to examine differences between groups. Results were considered significant if P -values were less than 0.05.


20 patients met the inclusion criteria but one withdrew before the second surgery leaving a total of 19 patients; 7 males and 12 females with a mean age (± SD) of 21.4 ± 2.3 years (range 18–26 years). The reason for extraction was chronic pericoronitis in all cases. Following random assignment there were no statistically significant differences between the flap design and the side of surgery ( P = 0.11). The operation time according to flap design was also comparable ( P = 0.62); the mean for the gingival flap group was 11.8 ± 7.9 min and 13.3 ± 9.6 min for the triangular flap group. Bone removal was performed in 16 cases (84.2%) and tooth sectioning in 10 cases (52.6%) of each study arm.

Table 1 compares the two flap designs with respect to postoperative facial swelling. Significant differences in the mean percentage of facial swelling were observed on postoperative days 2 and 7. The triangular flap design resulted in greater postoperative swelling; the difference on day 14 was not significant. The triangular flap design resulted in a significantly greater reduction in maximum inter incisal mouth opening and this was observed on postoperative days 7 ( P = 0.039) and 14 ( P = 0.004) ( Table 2 ). No significant differences in mean VAS scores were observed on postoperative day 2 ( P = 0.167), day 7 ( P = 0.988), or day 14 ( P = 0.859) ( Table 3 ).

Table 1
Mean percentage of facial swelling in gingival and triangular flaps at 2, 7, and 14 days postoperatively.
Postoperative days Flap design N Facial swelling P value
Mean % SD 95% CI for mean
2 Gingival 19 6.25 1.53 5.51–6.99 0.012
Triangular 19 7.77 1.92 6.85–8.70
7 Gingival 19 1.74 0.73 1.39–2.09 0.021
Triangular 19 2.42 1.02 1.93–2.92
14 Gingival 19 0.20 0.49 −0.03–0.44 0.667
Triangular 19 0.26 0.57 −0.01–0.54
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Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Flap design and mandibular third molar surgery: a split mouth randomized clinical study
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