Kumar 2015.

Study characteristics
Methods	Study design: parallel RCT Conducted in: India
Participants	Inclusion criteria: healthy patients 19 to 35 years old, mesioangular or horizontal mandibular third molar impaction, and a preoperative platelet count higher than 150,000/mm3 Exclusion criteria: patients in whom the second molar was missing or was indicated for extraction, patients with any underlying systemic disease or compromised immunity, and pregnant or lactating women Age: mean 26.1 years Number randomised: 31 Number evaluated: 31
Interventions	Only primary closure versus PRF placed in the socket followed by primary closure Group A intervention (n = 16): the impacted mandibular third molar was surgically removed, and 5 mL of venous blood was drawn and centrifuged at 3000 rpm for 10 minutes to prepare the PRF, which was placed into the extraction socket followed by flap approximation Group B control (n = 15): treated with surgical removal of the impacted mandibular third molar and flap re approximation
Outcomes	Follow‐up at first day and at 1 and 3 months Clinical evaluations: Pain and swelling were recorded on a VAS on the first postoperative day and at 1 and 3 months. Interincisal distance was evaluated using a divider and a scale on the first postoperative day and at 1 and 3 months. Pocket depth was measured at 1 and 3 months postoperatively and compared with preoperative values. Radiographic evaluations: IOPAs and OPGs at 1 and 3 months postoperatively
Notes	The student t‐test was used to determine a statistical difference between groups in the parameters measured. Proportions were compared by c2 test with Yates correction. Sample size calculation: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "randomised by the closed‐envelope method and divided into 2 groups" Comment: randomised by closed envelopes
Allocation concealment (selection bias)	Low risk	Quote: "patients were randomised by the closed‐envelope method and divided into 2 groups." Comment: concealed envelopes used
Blinding (performance bias and detection bias) patient	High risk	Quote: "in the case group, after the tooth was delivered, 5 mL of venous blood was drawn and centrifuged at 3,000 rpm for 10 minutes and PRF was obtained" Comment: the control group did not have blood taken, therefore there is a high chance they would know what group they were in
Blinding (performance bias and detection bias) assessor	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals
Selective reporting (reporting bias)	Low risk	Planned outcomes reported.
Other bias	Low risk	No other sources of bias identified.