Influence of placement depth and abutment connection pattern on bone remodeling around 1-stage implants: a prospective randomized controlled clinical trial.

Objectives: The aim of this study is to evaluate peri-implant marginal bone level changes in relation to crestal or subcrestal implant placement and type of fixture/abutment connection 3 months after implant placement.

Materials And Methods: The duration of the study was 3 months. A total of 105 implants were placed in 81 subjects following a one-stage surgical procedure and assigned into four groups. In the first and second groups, implants with a screwed tapered internal connection were placed subcrestally and crestally, respectively, while in the third and fourth groups, implants with an internal conical seal connection were similarly placed. Clinical recordings and standardized periapical digital radiographs were taken the day of implantation and 3 months later, before placement of the final prosthetic restoration. The modified plaque index (mPLI), modified gingival index (mGI), and probing depths (PD) were recorded at four sites around each implant, and the vertical distance between fixture/abutment junction and alveolar crest at the mesial and distal sites of each implant utilizing subtractive radiography were all measured on placement and at 3 months.

Results: There was no statistically significant difference between the four groups for PD. The highest values of mPLI and mGI were recorded for Group 2. The mean (±SE) peri-implant bone loss was recorded as follows: Group 1: 0.68 ± 0.07 mm, Group 2: 0.79 ± 0.06 mm, Group 3: 0.49 ± 0.06 mm, and Group 4: 0.40 ± 0.07 mm. The statistical analysis revealed significant differences in bone resorption between groups with different abutment connections.

Conclusions: The connection between fixture/abutment rather than vertical implant placement in relation to alveolar bone level seems to affect peri-implant marginal bone resorption.