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 the role 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) high definitive abutments. Marginal bone level change from the first to seventh year was the primary outcome. Peri‐implant status and other patient and peri‐implant clinical variables (smoking, peri‐implant maintenance therapy compliance, interproximal hygiene, 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 abutment group, and 20 subjects with 31 implants in the 3‐mm abutment group. Significant differences in marginal bone level changes were observed at 7 years. The 3‐mm abutment group showed smaller changes compared to the 1‐mm abutment group at mesial sites (−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 differences being statistically significant ( p < 0.001). In the control group, 18 implants (54.6%) presented peri‐implant mucositis and 6 implants (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‐term follow‐up compared to 1‐mm abutments. However, since the differences were not statistically significant, no conclusions could be drawn on the protective effect against peri‐implantitis.