The influence of submerged healing abutment or subcrestal implant placement on soft tissue thickness and crestal bone stability. A 2-year randomized clinical trial

Purpose Aims of the study were: (a) to register crestal bone loss around 1.5 mm subcrestally placed implants and epicrestally placed implants with soft tissue tenting technique, (b) to record bone remodeling in subcrestal group, and (c) to determine the increase of vertical soft tissues after tenting. Materials and methods Thirty-two patients with vertically thin tissues of 2 mm or less received 40 submerged bone level platform-switched implants, divided into two groups-(a) 1.5 mm subcrestally placed implants and (b) epicrestally placed implants with soft tissue tenting over 2 mm healing abutments. At the second stage surgery, implants received 4 mm healing abutments, soft tissue thickness was measured in epicrestal group, and later implants were restored with zirconia-based screw-retained single restorations. Radiological images were taken at the second stage surgery, restoration delivery and after 2 years of follow-up. Bone loss was calculated as a distance between implant neck and first radiographically visible bone-to-implant contact. Bone remodeling was calculated as a distance between the bone crest and implant neck. Mann-WhitneyUtest was used for statistical analysis, significance set to 0.05. Results After 2 years of follow-up, Group 1 (subcrestal) had 0.18 +/- 0.32 mm of bone loss, Group 2 (epicrestal with 2 mm healing abutment) had 0.51 +/- 0.4 mm of bone loss, with statistically significant difference (P= .001). Bone remodeling in Group 1 (subcrestal) was 1.17 +/- 0.51 mm. Vertical tissue thickness in epicrestal group before the intervention was 1.85 +/- 0.26 and 3.65 +/- 0.41 mm after the use of 2 mm healing abutment, with a statistical difference (P= .005). Conclusion Subcrestal implant placement can significantly reduce crestal bone loss, compared to vertical soft tissue thickening by tenting of epicrestally placed implants, although soft tissue tenting can significantly increase soft tissue thickness.