Objective: The objective of this study was to evaluate the peri-implant soft tissue and marginal bone loss (MBL) around implants with platform-switching and internal conical connection placed at crestal and subcrestal levels in posterior areas.
Materials and methods: Nineteen partially edentulous patients with at least two adjacent missing teeth in posterior areas unilaterally or bilaterally were included. Forty-two implants were placed randomly at the crestal or subcrestal (1 mm) level in a split-mouth design. Implant-supported fixed dental prostheses with screw retention were delivered after 4 months of healing. Clinical and radiological measurements were performed at implant placement (T0), restoration delivery (T1), and 1-year follow-up after loading (T2). MBL was calculated as the change in distance from the implant-abutment interface to the first radiographically visible bone-implant contact. A repeated-measures mixed ANOVA followed by a paired Student's t-test with the Bonferroni correction was used for statistical analysis. p < 0.05 was considered statistically significant.
Results: Eighteen patients with thirty-eight implants completed the study at T2. The MBL was lower in the subcrestal group than in the crestal group (0.04 ± 0.08 vs. 0.17 ± 0.17 mm, p = 0.004). The peri-implant probing depth (PD) was 2.31 ± 0.48 mm in the subcrestal group and 1.92 ± 0.43 mm in the crestal group; this difference was statistically significant (p = 0.002). Intragroup comparison showed no significant differences in MBL, or PD around the crestal group and subcrestal group from T1 to T2.
Conclusion: After 1 year of functional loading, subcrestal placement of implants with platform-switching and internal conical connection showed lower MBL and was associated with greater PD and peri-implant soft tissue height than implants placed at the crestal level.
Keywords: dental implant; implant placement depth; internal conical connection; marginal bone loss; platform switching; randomized controlled trial.
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