Long-Term Impact of 1-mm Versus 3-mm Definitive Abutments on Marginal Bone Loss and Peri-Implant Disease: A 7-Year Randomised Clinical Trial

Abstract

Aim: To evaluate bone level changes in implants with 1-mm- or 3-mm-high abutments over a 7-year period and to investigate therole of abutment height upon peri-implant status.Materials and Methods: Two-piece implants were placed 1.5 mm subcrestally with either 1-mm (control) or 3-mm (test) highdefinitive abutments. Marginal bone level change from the first to seventh year was the primary outcome. Peri-implant statusand other patient and peri-implant clinical variables (smoking, peri-implant maintenance therapy compliance, interproximalhygiene, vertical soft tissue thickness and keratinised mucosa width) were also assessed.Results: After 7 years, 37 subjects (63 implants) were analysed: 17 subjects with 32 implants in the 1-mm abutmentgroup, and 20 subjects with 31 implants in the 3- mm abutment group. Significant differences in marginal bone level changes wereobserved at 7 years. The 3-mm abutment group showed smaller changes compared to the 1-mm abutment group at mesialsites (−0.27 ± 1.32 mm vs. −0.42 ± 0.50 mm, respectively) and distal sites (−0.33 ± 1.39 mm vs. −0.35 ± 0.38 mm), with both differ-ences being statistically significant (p < 0.001). In the control group, 18 implants (54.6%) presented peri-implant mucositis and 6implants (18.2%) showed peri-implantitis. In the test group, 23 implants (74.2%) presented peri-implant mucositis and 1 implant(3.2%) showed peri-implantitis. No statistically significant differences were found (p = 0.158).Conclusions: Subcrestally inserted implants with 3-mm definitive abutments experienced minimal bone loss over long-termfollow-up compared to 1-mm abutments. However, since the differences were not statistically significant, no conclusions couldbe drawn on the protective effect against peri-implantitis.