Elgendy 2015.

Methods	Trial design: randomised, split‐mouth trial Location: Department of Periodontology, Faculty of Dentistry, October 6 University and Tanta University, Egypt Number of centres: 2 Recruitment period: February to December 2013 Source of funding: not stated Ethical approval: Research Ethical Committee of Tanta University, Egypt Number of surgeons: not stated
Participants	Inclusion criteria: presence of 2 almost identical interproximal intrabony defects, 1 on either side of the arch based on radiographic observations with clinical probing depth ≥ 6 mm in teeth Exclusion criteria: any systemic disease that affect the periodontium and contraindicate for periodontal surgery; patients having insufficient platelet count for PRF preparation; patients with coagulation defect or anticoagulation treatment; pregnant or lactating mothers; postmenopausal women; people who take anti‐inflammatory drugs, antibiotics or vitamins within the previous 3 months; people who use mouthwashes regularly; heavy smoking (> 10 cigarettes/day); history of alcohol abuse; unacceptable oral hygiene after the re‑evaluation of phase I therapy Age at baseline: group I 44.25 ± 8.45 years, group II 39.70 ± 6.36 years Gender: not stated Smokers: heavy smokers (> 10 cigarettes/day) were excluded Teeth treated: not reported Number randomised (participants/teeth): 20/40 Number evaluated (participants/teeth): 20/40
Interventions	Comparison: PRF + NcHA bone graft versus NcHA bone graft alone Test group: PRF + NcHA bone graft (n =20) Control group: NcHA bone graft alone (n = 20) Surgical technique: OFD + intrabony defects were treated with NcHA bone graft alone in control group and PRF was additionally applied in test group Follow‐up duration: 6 months
Outcomes	Clinical: PI, GI, PPD, CAL Radiographic: bone density Other: none
Notes	Sample size calculation: reported Comparability at baseline: yes, assessed Complications reported: no Dropouts: not reported, reasons not given
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Selected sites were randomly divided into 2 groups" Comment: insufficient information regarding the random sequence generation method
Allocation concealment (selection bias)	Unclear risk	Quote: "Selected sites were randomly divided into 2 groups" Comment: insufficient information regarding allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Impossible to blind the operator given the surgical nature of the treatment
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information is provided
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	It is unclear wether or not all patients completed the study
Selective reporting (reporting bias)	Low risk	All outcomes properly reported