Titanium-base abutments may have similar long-term peri-implant effects as non-bonded one-piece abutments

Design A single-centre (private practice), prospective, longitudinal, split-mouth, single-blind, randomised controlled clinical trial reported peri-implant parameters of individualised abutments bonded to titanium (Ti) bases during a five-year follow-up. The study complied with the ethical principles of the Helsinki Declaration and the CONSORT (Consolidated Standards of Reporting Trials) guidelines. It was approved by the Medical Ethical Committee of the University of Freiburg (013/1630) and registered in the German Clinical Trials Register (DRKS00006163).Case selection The included subjects had to be over 17 years of age, have an American Society of Anaesthesiologists score of 1, be a non-smoker, have a full-mouth plaque index (PI) below 20%, full-mouth bleeding index (BI) 20%, and planned with at least two dental implants but not adjacent to each other. Participants were excluded if they required simultaneous augmentation, were pregnant or breastfeeding, or had a history of periodontitis. Marginal bone loss (MBL) was the main clinical outcome, while local bleeding on probing (BoP), probing pocket depth (PPD), plaque Index (PI), local recession (REC), and relative attachment level (RAL) were also evaluated. The study timeline consisted of a screening (visit 1) and implant surgery (visit 2). Stage two was three months after implant surgery (visit 3), impression was two weeks after stage two (visit 4), followed up by baseline with a standardised radiograph (visit 5), one-year follow-up with radiographic and clinical parameters (visit 6), two-year follow-up (visit 7), three-year follow-up (visit 8), four-year follow-up (visit 9) and five-year follow-up (visit 10). In total, 24 subjects received two bone-level implants (Conelog, Camlog Biotechnologies, Basel, Switzerland) in the same arch and region up to 1 mm subcrestally. Their implant-abutment connection was an internal 7.5 degree conical connection platform-switch. Each subject received two abutments (one control and one test) as per the split-mouth design. The control abutments consisted of individualised, one-piece, computer-aided design/computer-aided manufacturing (CAD/CAM) titanium abutments, whereas the test abutments were CAD/CAM titanium abutments bonded to Ti-bases. The decision which implant was restored and in which way was made by a coin flip. The surgeon, patient and prosthodontist were blinded regarding the treatment allocation.Data analysis Descriptive measures and quantitative parameters were obtained from means, standard deviations, minimum and maximum values and 95% confidence intervals. The means of clinical parameters (six sites per implant) were MBL, BoP, PPD, PI, REC, and RAL. Paired t-tests were used for intragroup comparisons at different intervals as well as for intergroup comparisons within each time point. All data collected were considered until participants dropped out (that is, intention-to-treat principle). The significance level alpha was set to 0.05. The post-hoc power calculation of the MBL intergroup comparison dammed this trial as underpowered (power = 34%).Results All implants were osseointegrated after the healing stage and no implants were lost during the trial. Two subjects dropped out (one after the two-year follow-up and the other at the last appointment). Regarding MBL, no significant intergroup differences were found between the abutment groups. Nonetheless, significant intragroup differences were found at several visits (visit 6 to visit 10) compared to the baseline MBL (visit 5), indicating continuous bone level alterations. Concerning the BoP, no significant differences were identified. In terms of PPD, significant intergroup differences were found at visits 9 (p = 0.006) and 10 (p = 0.024), favouring Ti-base abutments. There were significantly intergroup differences in terms of REC (p = 0.014) at visit 10, with higher values in the one-piece abutment group. No differences were found in terms of PI.Conclusions A preliminary conclusion of this underpowered trial was that Ti-base abutments have a similar long-term effect to one-piece abutments on human peri-implant tissues.