Crestal bone loss in soft tissue level implants versus bone level implants in posterior mandible

Background: The long-term stability and success of dental implants is an interplay of many factors. Among these, the preservation of the crestal bone stability is still considered the most important one. The crestal bone stability is highly dependent on the implant design in the crestal area -implant neck and the type of implant – abutment connection.

Aim/Hypothesis: The aim of this comparative randomized clinical study was to radiographically evaluate the crestal bone level changes in soft tissue level implants versus bone level implants with platform-switched/hexagonal abutment connection placed in a single-stage manner in the mandibular molar region. Material and Methods: The study was carried out with inclusion criteria of non-smoking patients missing single or multiple teeth in the posterior mandible. Individuals with systemic diseases, poor oral hygiene and periodontal diseases were excluded from the study. Local inclusion criteria were sufficient bone width for implant placement and vertically gingival thickness >3 mm. Patients were divided into two groups. Group I: soft- tissue level implants, (TRI Octa, TRI, Swiss) included 18 patients who received 30 implants; group I: bone level implants, (TRI Vent, TRI, Swiss) included 15 patients who received 30 implants. The crestal bone level (CBL) was assessed with digital software measurement in peri-apical radiographs imaged with Carestream 2200 generator and RVG 6200 sensor (Carestream, NY, USA) using the paralleling technique. The radiographical assessment was done at three time points: the time of implant surgery, 3 months later and 12 months post loading with screwretained zirconia restorations.

Results: All implants in both groups showed a 100% survival and success rate at 1 year post- surgery. The data was analysed using two-way ANOVA test and p value < 0.05 was considered statistically significant. At three months post- surgery, mean CBL for group I was 0.22 mm (SD 0.48), whereas mean CBL for group II was 0.21 mm (SD 0.5), without statistically significant difference. At 12 months post-loading, mean CBL for group I was 0.19 mm (SD 0.51) and mean CBL for group II was 1.4 mm (SD 0.8). There was a statistically significant

difference between the CBL in both groups (p < 0.001) at this timepoint.

Conclusion and Clinical Implications: Within the limitations of the sample size of this study, both implant designs showed minimal crestal bone loss at 3 months postoperatively. However, at 1-year post-loading, soft-tissue level implants showed less crestal bone loss compared to bone-level implants with hexagonal platform-switched connection, which may have clinical relevance regarding long-term implant survival.

I confirm that ethical permits and approvals are in place in accordance with regulations: Yes, I confirm that ethical permits and approvals are in place.

Disclosure of Interest: None Declared.

Keywords: Clinical studies/trials, Dental implants, Marginal bone loss