Discussion
STM, fractures, peri-implantitis, peri-implant mucositis
SCREW LOOSENING, COMPLICATION, COMPLICATIONS
The present long-term randomized controlled clinical trial comparing two types of dental implants with non-matching implant-abutment junctions supporting fixed restorations at 10 years of loading revealed: i) high survival rates for both types of dental implants, ii) stable marginal bone levels, iii) a higher rate of technical complications in group AST, iv) a higher rate of peri-implant mucositis in group STM.The present study demonstrates an overall survival rate of 100% on the patient level and 89.7% for group AST and 96.8% for group STM on the implant level. This finding is consistent with prior publications, which have also reported high implant survival rates in short- and long-term observation periods [The available evidence shows that both systems assessed in this study exhibited implant survival rates ranging from 90.9% to 100% (AST) and 96.5% to 99.3% (STM) during observation periods spanning 1 to 10 years [When utilizing two-piece dental implants featuring a non-matching implant-abutment junction, studies report the maintenance of marginal bone in close proximity to the implant shoulder [The present investigation reveals that at the 10-year time-point, the median changes of the marginal bone levels between baseline and 10 years amounted to a loss of 0.07 mm for group AST, and to a gain of 0.37 mm for group STM. While the intergroup difference rendered a statistical significance, the clinical significance of this disparity remains uncertain. Absolute marginal bone levels between the two implant systems were clinically negligible at 10 years (median difference of 0.26 mm). Nevertheless, this difference is in line with recent publications. In a recent meta-analysis comparing the same systems amongst others, present study’s group AST showed favorable marginal bone maintenance. The authors also pointed out that even if statistically significant, the mean amount of marginal bone level change is small (MBL change ATO: -0.29 mm; SLA: -0.83 mm; NBT: -0.87 mm) [The rates of technical complications differed between the two implant systems investigated, with group AST demonstrating more technical complications (27.0%) than group STM (15.6%) during the observation period of 10 years overall. Interestingly most of those complications occurred at earlier time-points, leaving rates of only 8.7% (AST) and 0% (STM) within the last two years of follow-ups (between TComparing those rates to priorly published literature, they are higher than the reported range between 5 and 15% over 5 years for implant supported single crowns [However, looking at the overall annual complication rate for implant supported single crowns in a systematic review and meta-analysis (4.2%, ranging from 1.7% to 15.5%), the results are in line with the technical complication rates withing the last two years of follow-ups in present study (8.7% for group AST and 0% for group STM) [A recently published 6-year retrospective study investigated screw loosening with respect to several parameters, showing an overall rate of 7.2%. The highest frequency of screw loosening was investigated in the first 6 months after loading, predominantly in the molar region and significantly more frequent in implants with external than internal implant-abutment connections [The higher rates of technical complications in present study can be attributed to a difficult comparison with prior literature. In a systematic review of outcome and measures, Sailer et al. state, that additionally to the finding that proshtetic failure is the least reported outcome measure, an inconsistent reporting about chippings and extended fractures of the veneering ceramic was found [In the current investigation, the incidence of peri-implant mucositis was found to be 29.7% in group AST and 50.1% in group STM. The prevalence of peri-implantitis was 0% in group AST and 6.3% in group STM, aligning well with the conclusions of recent systematic reviews.Previous systematic reviews have investigated the prevalence of peri-implant mucositis and peri-implantitis ranges between 19% – 65% and 1% to 47% respectively [One limitation of the present study is the absence of a formal sample size calculation. The primary outcome of interest at the time the study was initiated was the change in marginal bone levels, which was considered as a key parameter/metric for assessing implant success. Since data on STM was not available at the time, a convenience sample of patients was recruited based on the required number. Despite this limitation, the results of this study are deemed to be representative of a general dental practice, as a wide range of inclusion criteria were employed, limited only to fixed restorations. However, the wide range of inclusion criteria, which encompassed various factors such as implant location (maxilla, mandible, anterior, posterior), the use of guided bone regeneration (GBR), type of healing (submerged, transmucosal), loading time, retention type, and restoration material, may also be considered a potential drawback. The vertical component of the prosthetic part, mucosal thickness, and the anatomic location of the implants are recognized as crucial parameters that exert influence over peri-implant tissue stability. While these aspects were not reported within the scope of this study, their potential impact remains relevant for further investigation.