Absi 1993.

Study characteristics
Methods	Study design: RCT (split‐mouth) Conducted in: Department of Oral Surgery, University Dental School, Cardiff, Wales, UK
Participants	Inclusion criteria: 52 consecutive healthy patients scheduled for surgery entered the trial after assessment with dental panoramic radiograph. All had similarly impacted bilateral lower third molars. Exclusion criteria: patients were excluded if they had pericoronitis in the 6 weeks before surgery, or if they were allergic to any of the drugs in the standard regimen Age: mean 22 years Number randomised: 52 Number evaluated: 52
Interventions	Lingual split with chisel versus bur for bone removal under general anaesthesia Group A (n = 52 teeth): lingual split with chisel for bone removal Group B (n = 52 teeth): lingual split with bur for bone removal Follow‐up: 4 weeks All procedures were carried out under general anaesthetic. 43/52 participants had maxillary third molars extracted in same session.
Outcomes	Questionnaire assessment of lingual and inferior alveolar nerve function, swelling and pain were measured by a 4‐point scale at 6 h, 24 h, 48 h, and 7 days after the procedure. Participants also asked to indicate which side they felt was more swollen at these intervals. Infection was assessed by the presence of dry sockets or purulence or both.
Notes	Sample size calculation: not reported Email sent to author (12 February 2003). Unpublished data supplied.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...the method for a particular side and the third molar removed first were selected randomly" After contacting author, method of randomisation disclosed as "nurse blindly selecting a piece of paper on which was written either 'left' or 'right' from a bag in which were placed equal numbers of pieces of paper with 'left' and 'right' written on them".
Allocation concealment (selection bias)	Low risk	The operator was blinded to the above randomisation procedure. Comment: allocation concealed
Blinding (performance bias and detection bias) patient	Low risk	Quote: "...the trial was single‐blind to the patient as far as the surgical method was concerned" Comment: as the procedures were carried out under general anaesthetic, it can be assumed that the participants were blinded to which side received which intervention
Blinding (performance bias and detection bias) assessor	Low risk	Outcome assessors (the participants) were blinded for pain, swelling, and sensory disturbances. "on day 7... the wounds were examined by an independent observer"
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts
Selective reporting (reporting bias)	Low risk	The author was unable to specify which group (and indeed which socket ‐ upper or lower) received an acute abscess, despite direct correspondence on the matter.
Other bias	Unclear risk	In 43 of the 52 participants, maxillary third molars were also extracted; however, we contacted the author, who assured us that none of these were surgical. Author notes: "higher complication rates might have been found if this information had been supplemented by clinical assessments", noting the limitations of subjective assessment