A retrospective study on the factors associated with marginal bone loss of short implants placed in posterior regions

Purpose: This retrospective cohort study was performed to assess marginal bone loss (MBL) and its risk factors in patients with a short-er-than-conventional length implant in the posterior regions of the mandible or maxilla. Materials and Methods: The study sample was composed of short implants (7-mm length, 4-mm diameter). Periapical radiographs were taken immediately after functional loading, 6 months after prosthesis delivery, and at all follow-up visits. Measurements were per-formed using radiographs. The potential risk factors assessed by univariate and multivariate regression analysis were history of guided bone regeneration (GBR), prosthesis type, crown-to-implant ratio, and soft-tissue thickness. Results: In total, 105 implants in 78 patients were included. Mean follow-up period was 22.27±9.69 months, and mean cumulative peri-implant bone loss during follow-up was 0.13±0.19 mm (range, 0.0∼0.83 mm). MBL risk did not increase significantly according to a history of GBR, prosthesis type, or crown-to-implant ratio. Simple linear regression showed soft-tissue thickness was a risk factor of MBL. However, multiple linear regression failed to identify any significant risk factor of MBL. Conclusions: The results of this study suggest that insufficient soft-tissue thickness is a risk factor for MBL in patients with a short implant.