Background: Peri-implantitis is a common complication following replacement of teeth using dental implants to restore esthetics, and function. Bone defect configuration at teeth with periodontitis appears to differ at teeth between anterior and posterior positions and with 4-wall defects as the most common defect type. Early studies in periodontal research using regenerative procedures have suggested that circumferential bone defects have a good potential to regenerate.

Aim/Hypothesis: The objectives of the present study were to assess if- (I) the alveolar bone defect configuration at dental implants diagnosed with peri-implantitis is related to clinical parameters at the time of intervention.(II) the outcome of surgical intervention of peri-implantitis is dependent on defect configuration at the time of treatment.

Material and Methods: 39 patients with 74 implants with a diagnosis of peri-implantitis were included in a single blinded, randomized clinical study. A minimum of one osseo-integrated implant with ≥ 2 mm alveolar bone loss defined by comparing intra-oral radiographs at the time of screening for this study with bone loss assessed from radiographs taken at the placement of the supra-structure. a PD ≥ 5 mm, and with BOP suppuration the study implants must have an angular peri-implant bone defect 3 mm in depth as determined from intra-oral digital radiographs only cases with clinical evidence of a 2, 3, or 4 wall defects at time of surgery were included. After receiving surgical debridement, the subjects were randomly assigned to placement of an autogenous bone graft (AB) or a bovine derived xenograft (BBX- Bio-Oss®, Geistlich Pharma, Wolhusen, Switzerland) in the osseous defects at implants. In all cases, a resorbable membrane (OsseoGuard®, Biomet3I Inc., Palm Beach, FL, USA) was placed over the bone graft. Radiographic defect fill was assessed at 1 year. Definition of bone walls at dental implant(1) two-wall defects requiring two surfaces without a bone wall, but with vertical angulated bone loss towards two implant surfaces. (2) three-wall defects requiring one surface without a bone wall, but with vertical angulated bone loss towards three implant surfaces. (3) four-wall defect includes vertical angulated defects towards the implant at all four surfaces. The four-wall defect can also be described as a saucer-like defect.

Results: When all cases with 3-wall defects were included improvements in BOP scores (P < 0.001), and probing depths (mean diff 1.5, S.E. ± 0.3, 95% CI- 1.5, 2.8, P < 0.001) were identified. The analyses failed to demonstrate differences in plaques cores, or evidence of defect changes between baseline and year 1. At 4- wall defects the analysis identified radiographic evidence of defect fill (mean diff- 1.2 mm, ± S.E. 0.5, 95% CI 0.1, 2.4, P = 0.05). Probing depth reductions (mean diff- 2.4, S.E. ±0.5, 95% CI- 1.3, 3.5, P < 0.001), and. BOP % reduction over time (mean diff- 34.6, S.E. ± 10.0, 95% CI- 12.8, 56.5, P < 0.01) but no differences in plaque scores could be verified

Conclusion and Clinical Implications: (I) The buccal-lingual width of the alveolar bone crest was explanatory to defect configuration (II) 4-wall defects demonstrated more defect fill(III) deeper defects resulted in more defect fill(IV) autologous bone was less effective than an exogenous bone augmentation material.