MATERIALS AND METHODS

A description of the study cohort presenting explanatory variables and univariate and multivariate implant survival analysis has been previously published. Details on recall and follow up are further described in a companion paper. In brief, this was a retrospective study consisting of 2,060 patients with an initial total of 4,591 implants. All implants were placed between 1999 and 2012, in Calgary, with all surgeries and measurements performed by one periodontist (DF). No intra‐examiner calibration was performed. Implant stability was evaluated at 2 to 3 months post‐insertion, using a 35 Ncm torque test and radiographic bone measurements, which served as baseline for future evaluation of the crestal bone level (CBL). Follow‐up was scheduled at 1‐, 3‐, 5‐ and up to 10 years. Follow‐up was less defined after 5 years as patients generally returned for complications, new surgical site, or were large complex restorations. The study was approved by the Clinical Research Ethics Board at the University of British Columbia (Vancouver # H13‐01664 titled UBC Implants) and was conducted in accordance with the Helsinki Declaration of 1975, as revised in 2000. All patients provided written informed consent to participate in the study.

The majority of the implants were standard design with regular or wide neck, diameters of 4.1 or 4.8 mm and lengths of 8, 10, or 12 mm. All surgeries were performed by open flap using surgical protocols described previously. All implants, except for immediate socket or bone graft scenarios, were inserted in suitable prosthetic positions with good primary stability and the border between the machined neck and the micro‐rough surface was positioned fully in bone for the circumference of the implant. The impact of guided bone regeneration and immediate socket placement on CBL was evaluated in addition to other risk indicators.