The Influence of Repeated Abutment Changes on Peri-Implant Tissue Stability and Keratinised Tissue on Peri-Implant Health: 12-Year Post-Loading Results From a Multicentre Randomised Controlled Trial

AimsTo evaluate the influence of at least three abutment disconnections in conventionally loaded implants against placement of a definitive abutment in immediately non-occlusal loaded implants on hard and soft tissue changes. A secondary aim was to evaluate whether the presence of less than 2 mm of keratinised mucosa is associated with increased peri-implant marginal bone loss and soft tissue recessions.MethodsSixty patients requiring one single crown or one fixed partial prosthesis supported by a maximum of three implants were randomised, after implants were placed with a torque superior to 35 Ncm, according to a parallel group design to receive definitive abutments which were loaded immediately (definitive abutment group) or transmucosal abutments which were delayed loaded after 3 months and were removed at least three times (repeated disconnection group). Patients were treated in three centres, and each patient contributed to the study with only one prosthesis followed for 12 years after initial loading. Outcome measures were: prosthesis failures, implant failures, complications, pink esthetic score (PES), buccal recessions, patient satisfaction, peri-implant marginal bone level changes, and height of the keratinised mucosa.ResultsThirty patients were randomly allocated to each group according to a parallel group design. Six patients dropped out or died from the definitive abutment group and seven from the repeated disconnection group. At 12 years post-loading, no patient in the definitive abutment group had implant failures versus three patients who lost five implants in the repeated disconnection group (difference = 13.04%; 95% CI: -6.7 to 26.8 to; p = 0.109; Fisher's exact test). No patient in the definitive abutment group had a prosthesis failure versus four patients of the repeated disconnection group. The difference was statistically significant (difference = 17.39%; 95% CI: 1.9 to 32.9; p = 0.049; Fisher's exact test). Four patients from the definitive abutment group versus seven patients from the repeated disconnection group were affected by complications (difference = 13.77%; 95% CI: -37.8 to 10.2; p = 0.318; Fisher's exact test), the difference not being statistically significant. PES scores did not show any statistically significant differences between the two groups: 10.84 +/- 1.95 for the definitive abutment group and 10.31 +/- 2.57 for the repeated abutment changes group (difference = -0.53; 95% CI: -1.14 to 2.20; p = 0.505). Buccal recessions amounted to 0.30 +/- 0.98 mm for the definitive abutment group and 0.15 +/- 0.54 mm for the repeated abutment changes group with no statistically significant differences between the two groups (difference = -0.14; 95% CI: -0.69 to 0.41; p = 0.592). All patients were declared to be very satisfied with the function and aesthetics of the prostheses and would undergo the same procedure again. Mean peri-implant marginal bone loss was 0.25 +/- 0.49 mm for the definitive abutment group and 0.70 +/- 1.04 mm for the repeated abutment changes group (difference = 0.45; 95% CI: -0.16 to 1.05; p = 0.135), the difference not being statistically significant. Height of keratinised mucosa was 2.56 +/- 1.75 for the definitive abutment group and 2.77 +/- 2.07 for the repeated abutment changes group (difference = 0.21 mm; 95% CI: -1.06 to 1.49; p = 0.746). There was no significantly increased marginal bone loss (difference = 0.20; 95% CI: -0.06 to 0.33; p = 0.268) or buccal recessions (difference = 0.10; 95% CI: -0.05 to 0.33; p = 0.203) at implants having less than 2 mm of keratinised mucosa at loading.ConclusionMore prosthesis failures were observed at 12 years after loading when comparing implants that underwent at least three repeated abutment disconnections to implants subjected to no disc