Renton 2005.

Study characteristics
Methods	Study design: RCT (parallel/split‐mouth) Conducted in: Department of Oral and Maxillofacial Surgery, Guy's Dental Hospital London, UK
Participants	Inclusion criteria: patients who required removal of third molars and were judged to be at high risk of injury to the inferior alveolar nerve based on radiographic features Exclusion criteria: patients who were predisposed to local infection, or who had systemic infections, and those with previous or existing defects of the inferior alveolar nerve. Patients with neuromuscular disorders or non‐vital third molars were also excluded. Number randomised: 128 participants, 196 teeth Number evaluated: unclear
Interventions	Coronectomy versus complete surgical removal Group A (n = 94 teeth): coronectomy ‐ sectioning 3 to 4 mm below the crown, reducing roots with bur and leaving in situ. No treatment to the pulp Group B (n = 102 teeth): complete surgical removal of teeth 60% of teeth were treated under general anaesthesia, 30% under local anaesthesia, and 10% under sedation + local anaesthesia. 3 surgeons performed the procedures. Follow‐up: 2 years
Outcomes	Verbal assessment and mechanosensory testing of inferior alveolar nerve, dry socket infection or soft‐tissue infection assessed immediately postoperation, on day 3, and after 1 to 2 weeks
Notes	Sample size calculation: not reported Unit of randomisation is teeth. Patients having non‐surgical extraction were excluded. In order to overcome problems related to the study being a mixture of split‐mouth and parallel‐group designs, 1 site per participant was randomly selected. Additional information supplied by author.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "...the teeth to be removed were randomised (using a table of random numbers that was concealed from the surgeon)"
Allocation concealment (selection bias)	Low risk	Quote: "...the teeth to be removed were randomised (using a table of random numbers that was concealed from the surgeon)"
Blinding (performance bias and detection bias) patient	Unclear risk	Blinding of participants not mentioned. Surgeons would have an ethical duty to inform their patients that some of their tooth was remaining in situ.
Blinding (performance bias and detection bias) assessor	High risk	Not mentioned whether or not outcome assessors were blinded. Method of pain assessment not discussed.
Incomplete outcome data (attrition bias) All outcomes	High risk	128 participants were included, but it is unclear how many participants were in each group. Denominators for outcomes are teeth not people, and participants not analysed in the groups into which they were originally randomised: presence of the failed coronectomy subgroup confounds the intention‐to‐treat analysis. 22 of the 196 teeth were simple elevation extractions, and there does not appear to be any statistical accounting for this. "Of the 58 patients who had coronectomy 47 (81%) attended the department for review within the first 6 months." No reasons given for these failures of follow‐up. No mention of follow‐up in extraction group
Selective reporting (reporting bias)	High risk	All prespecified outcomes reported on, but some outcomes not reported for each randomised group. Some data were supplied by the authors, but it is unclear when and how pain was assessed. Pain is reported per tooth, but participants with 2 teeth in the study would be expected to have greater pain.
Other bias	Unclear risk	No mention of how pain was assessed or if any statistical tests were done on it. 196 teeth from 128 participants, and it is often unclear which numbers were used in analysis.