Hanna 2004.

Methods	Trial design: randomised, split‐mouth, double‐blinded trial Location: The University of Texas Health Science Center at Houston, Texas, USA Number of centres: 1 Recruitment period: not reported Source of funding: not stated Ethical approval: yes, Committee for the Protection of Human Subjects at the University of Texas Health Science Center at Houston, Texas, USA Number of surgeons: 1
Participants	Inclusion criteria: patients between 35 to 75 years of age; exhibited plaque score of 20% or less prior to the surgical phase; teeth with mobility less than Miller's Class III or mobile teeth requiring splinting; and teeth responding normally to vitality testing or with stable endodontic therapy Exclusion criteria: known systemic diseases and/or drug therapy known to interfere with wound healing; known drug allergies to any of the medications used in the study; using systemic antibiotics or having received antibiotic therapy in the last 3 months; abnormal platelet counts disclosed by a complete blood count (CBC) test performed within 1 month prior to surgery; and participation in other dental clinical trials Age at baseline: 37 to 74 years Gender: F 8/M 5 Smokers: yes, 1 heavy smoker (> 20 cigarettes/day) Number randomised (participants/teeth): 13/26 Number evaluated (participants/teeth): 13/26
Interventions	Comparison: BDX + PRP versus BDX alone Test group: BDX + PRP (n = 13 defects) Control group: BDX alone (n = 13 defects) Surgical technique: OFD + intrabony defects treated with BDX alone in control group and additionally PRP was applied in test group Follow‐up duration: 6 months
Outcomes	Clinical: GI, PI, PD, CAL, recession as the position of the gingival margin from the CEJ, and BOP Radiographic: none reported Other: none
Notes	Sample size calculation: not reported Comparability at baseline: yes, assessed Complications reported: yes Dropouts: reported, no dropouts
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization was performed immediately following defect debridement by the flip of a coin" Comment: correct method for random sequence generation
Allocation concealment (selection bias)	Unclear risk	Quote: "Randomization was performed immediately following defect debridement by the flip of a coin" Comment: not sufficient information provided regarding the method of allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Impossible to blind the operator due to the surgical nature of the treatment
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "13 patients were enrolled in a randomized, split‐mouth, double‐masked clinical trial" Comment: blinding of outcomes likely to have been done properly
Incomplete outcome data (attrition bias) All outcomes	Low risk	All randomised patients completed the study
Selective reporting (reporting bias)	Low risk	All outcomes properly reported