Do repeated changes of abutments have any influence on the stability of peri-implant tissues? Four-month post-loading preliminary results from a multicentre randomised controlled trial

PURPOSE: To evaluate the influence of at least three abutment changes against the placement of a definitive abutment, which was no longer removed, on hard and soft tissue changes, and to compare the clinical outcomes of immediate non-occlusal loading versus conventional loading. MATERIALS AND METHODS: Eighty patients requiring one single crown or one fixed partial prosthesis supported by a maximum of three implants were randomised, after implants were placed with more than 35 Ncm, according to a parallel group design to receive definitive abutments which were loaded immediately (definitive abutment or immediate loading group) or transmucosal abutments which experienced delayed loading after 3 months and were removed at least three times: 1) during the making of the impression (3 months after implant placement); 2) when checking the zirconium core of titanium abutments at single crowns or the fitting of the metal structure at prostheses supported by multiple implants; 3) at delivery of the definitive prostheses (repeated disconnection or conventional loading group). Patients were treated in four centres and each patient contributed to the study with only one prosthesis followed for 4 months after initial loading. Outcome measures were: prosthesis/implant failures, any complication, peri-implant marginal bone level changes, and patient satisfaction. RESULTS: Forty patients were randomly allocated to each group according to a parallel group design. No patient dropped-out and no implants failed. However four provisional prostheses and one definitive prosthesis had to be remade because of misfitting (five single crowns) in the repeated disconnection group; and one provisional prosthesis had to be remade because of frequent debondings in the immediate loading group (difference=10%; 95% CI: -1%, 21%; P=0.109). Five complications (all debondings of the provisional prostheses) were reported in two patients of the immediate loading group, in comparison to three biological complications in three patients of the repeated disconnection group (difference=2%; 95% CI: -8%, 13%; P=1). All patients were very satisfied or satisfied with the function and aesthetics of the prostheses, and would undergo the same procedure again. Mean peri-implant marginal bone loss 4 months after loading was -0.08 (0.16) mm for the definitive abutment group and -0.09 (0.20) mm for the repeated abutment changes group (difference=0.01; 95% CI: -0.07, 0.09; P=0.97). There were no statistically significant differences for any of the outcome measures between the two procedures up to 4 months after initial loading. CONCLUSIONS: Preliminary short-term data (4-month post-loading) showed that repeated abutment changes do not alter bone levels significantly. Immediate non-occlusal loading of dental implants are a viable alternative to conventional loading. Therefore clinicians can use the procedure they find more convenient for their specific patient.