Goldsmith 2012.

Study characteristics
Methods	Study design: split‐mouth RCT Conducted in: University of Otago, New Zealand
Participants	Inclusion criteria: patients aged 16 to 40, American Society of Anesthesiologists Physical Status classification I or II, with bilateral symmetrically impacted partially erupted mandibular third molars, no associated pathology, no medical conditions that might alter wound healing potential Exclusion criteria: history of abuse of midazolam, allergy to any of the medications to be used, pregnancy, present or previous radiotherapy to third molar region of lower jaw, long‐term steroid or bisphosphonate use, bone disorder or fibrous dysplasia Number randomised: 57 Number evaluated: 52 (42 for pain outcome)
Interventions	Envelope flap versus pedicle flap Group A (n = 52 teeth): incision placed in the buccal gingival sulcus from the mesio‐buccal line angle of the first molar to the most distal visible aspect of the third molar. The relieving incision then extended up the external oblique ridge. Group B (n = 52 teeth): pedicle flap design involved the same initial incision, in the buccal gingival sulcus, but distil to the third molar the incision was extended approximately 1 cm and then curved towards the buccal sulcus allowing for rotation of the flap and primary closure over sound bone Follow‐up: 7 days 3 weeks between procedures. All procedures were carried out by the same surgeon under sedation with midazolam and local anaesthetic. All participants received standard pain relief medication regimen (ibuprofen/paracetamol plus codeine phosphate if required) and 0.2% CHX mouth rinse to be used 3 times daily for 5 days.
Outcomes	Alveolar osteitis, wound infection, pain, swelling, trismus, wound dehiscence on days 2 and 7 (envelope flap only)
Notes	Sample size calculation: stated that sample size was determined by a power calculation using previously collected data Funding: New Zealand Dental Research Foundation and University of Otago Fuller Scholarship E‐mail from authors 22 August 2013 provided additional information.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "randomly allocated into one of two groups using the Logan envelope technique.... In one group the first procedure was carried out using the envelope flap design... both flap designs were randomly allocated to left or right side of each participants lower jaw again using Logan envelope technique" E‐mail from author: "...a larger envelope contained smaller pieces of paper that had the type of flap to be assigned to a patient, on the day of the procedure the surgeon's assistant would 'blindly' pick out a piece of paper and the surgeon would then use that type of flap. The same was done for assigning which side of the mouth would be operated on"
Allocation concealment (selection bias)	Low risk	Allocation concealed from operator.
Blinding (performance bias and detection bias) patient	Low risk	E‐mail from author: "Patients were not aware of what type of flap they received nor were the clinicians who did the follow‐up clinical outcomes"
Blinding (performance bias and detection bias) assessor	Low risk	E‐mail from author: "Patients were not aware of what type of flap they received nor were the clinicians who did the follow up clinical outcomes"
Incomplete outcome data (attrition bias) All outcomes	Low risk	10 participants excluded from pain evaluation due to missing data, but unlikely to result in bias in split‐mouth study.
Selective reporting (reporting bias)	Unclear risk	Trismus outcome data not reported.
Other bias	Low risk	No other sources of bias identified.