Schwarz 2006b.

Methods	4‐year follow‐up, randomised, parallel group study. Blinded outcome assessor. 3 patients were withdrawn: 2 1 year after treatment from the nanocrystalline hydroxyapatite group and 1 3 years after treatment from the anorganic bovine bone group because of recurrence of peri‐implantitis.
Participants	Patients having at least 1 implant affected by peri‐implantitis with an infrabony component > 3 mm and PD > 6 mm. Exclusion criteria were absence of peri‐implant keratinised mucosa, regular smokers, hollow cylinder implants, evidence of overload and any systemic diseases that could influence the outcome of the therapy. Adults treated in Heinrich Heine University, Düsseldorf, Germany. 22 patients enrolled (11 in each group) and results given for 19.
Interventions	Patients were previously treated with a single‐course non‐surgical instrumentation with plastic curettes followed by pocket irrigation with 0.2% chlorhexidine and subgingival application of chlorhexidine gel. After flap elevation and removal of granulation tissues, implants were debrided using plastic curettes and rinsed with saline solution. Sites were filled or with nanocrystalline hydroxyapatite (Ostim, Heraeus Kulzer, Hanau, Germany) injected using a ready‐to‐use paste in a syringe or with a bovine‐derived xenograft (Bio‐Oss, Geistlich, Wolhusen, Switzerland, particle size 0.25 to 1 mm) in combination with a resorbable collagen barrier (Bio‐Gide, Geistlich) of porcine origin. The trial included Brånemark System® (Nobel Biocare, Göteborg, Sweden), Camlog Screw Line® (Camlog, Wimsheim, Germany), KSI Bauer Schraube (Bad Nauheim, Germany), ITI both SLA and TPS (Straumann, Waldenburg, Switzerland), Spline Twist MTX and Tapered Screw Vent (Zimmer Dental, Freiburg, Germany), and ZL‐Duraplant Ticer (ZL Microdent, Breckerfeld, Germany) implants.
Outcomes	Implant failure, recurrence of peri‐implantitis, PAL, PPD, REC, plaque, BOP and complications/side effects at baseline and 6, 12, 18, 24, 36 and 48 months.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The defects were randomly assigned before surgery to the following test and control groups according to a computer‐generated protocol (RandList, DatInf, GmbH, Germany)".
Allocation concealment (selection bias)	Unclear risk	No information in the article. Author's reply failed to clarify the issue.
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "All measurements were made at 6 aspects per implants by one blinded and previously calibrated investigator (K. B.). All treatments were performed by the same experienced surgeon (F. S.)".
Incomplete outcome data (attrition bias) All outcomes	High risk	2 patients from the Ostim group and 1 from the Bio‐Oss group were withdrawn from the study because of severe pus formation 1 and 3 years after initial treatment, respectively. They were treated with Er:YAG laser decontamination and augmented Bio‐Oss and Bio‐Gide barriers as in the control group. No data were presented regarding the outcomes of the their re‐treatments.
Selective reporting (reporting bias)	High risk	Pre and postoperative radiographs at 6 and 24 months were taken and evaluated but there was no description of how they were assessed nor data apart from an approximate subjective quantification. Missing data for the patient excluded by the authors.
Other bias	Low risk	None apparent. Interestingly the trial was sponsored by both biomaterial manufacturers whose products were compared.