Marginal bone changes around platform-switched conical connection implants placed 1 or 2 mm subcrestally: A multicenter crossover randomized controlled trial

AbstractIntroduction:This study analyzes early marginal bone modifications occurring aroundplatform-switched implants with conical connection placed 1 or 2 mm subcrestally.Methods:This crossover randomized controlled trial enrolled partially edentulouspatients needing two implants in either the posterior maxilla or mandible. Eachpatient received two platform-switched implants with conical connection inserted2 mm (Test) and 1 mm (Control) subcrestally. Definitive abutments were immediatelyconnected and, after 4 months of unsubmerged healing, screwed metal-ceramiccrowns were delivered. Radiographs were taken at implant placement (T0), prosthesisdelivery (T1), and after 1 year of prosthetic loading (T2).Results:Fifty-one patients (25 males and 26 females; mean age 61.2 ± 12.1 years)totaling 102 implants were included in the final analysis. Mean peri-implant bonelevel (PBL) reduction from T0 to T2 was not significantly different around Test (0.49± 0.32 mm) and Control implants (0.46 ± 0.35 mm;p=0.66). Multivariate linearregression models highlighted a significant positive correlation between history ofperiodontitis and PBL reduction. At T2, no Test group implant and 6 Control groupimplants exhibited PBL below the implant platform (11.8% of Control groupimplants).Conclusion:No significant differences in peri-implant marginal bone changes weredemonstrated after 1 year of prosthetic loading between platform-switched implantswith conical connection inserted either 1 or 2 mm subcrestally. However, 2 mm sub-crestal placement resulted in deeper implant positioning at T2, with no exposure oftreated implant surface and potential preventive effect against subsequent peri-implant pathology.