Purpose: To evaluate marginal bone level changes over 3 years around platform-shifting implants with internal conical connections, and to identify the factors relating to bone level changes.
Materials and methods: Systemically healthy patients who lost one tooth or two consecutive teeth were enrolled in the study. The subjects received one or two implants with platform-shifting and internal conical connections in healed bone in a submerged manner. Digital standardized periapical radiographs were obtained at the time of implant placement, at prosthesis delivery, at 1 year, and at 3 years after the definitive restorations. Marginal bone level changes were measured at the mesial and distal aspects of each implant. Spearman correlation coefficients were calculated to examine the correlation between marginal bone level changes and clinical factors (age, vertical mucosal thickness, implant length and diameter, insertion torque value, and vertical implant position).
Results: Twenty-five patients with 30 implants (8 men and 17 women, mean age: 61.24 ± 13.18 years) were followed up to 3 years after the definitive restorations. The implant survival rate was 100%, and no remarkable complications were found. Mean peri-implant marginal bone level changes were -0.41 ± 0.61 mm (from placement to prosthesis delivery: C1); -0.08 ± 0.54 mm (from prosthesis delivery to 1 year: C2); -0.04 ± 0.95 mm (from prosthesis delivery to 3 years: C3); and 0.04 ± 0.60 mm (from 1 year to 3 years: C4), respectively. Statistically significant differences in bone level changes were observed between C1 and C3, and C1 and C4. Significant correlations of marginal bone level changes with implant diameter in C1 and with vertical implant position in C2 and C3 were observed.
Conclusion: Within the limitations of this study, platform-shifting implants with internal conical connections appeared to prevent marginal bone resorption, especially after delivery of definitive prostheses, although marginal bone resorption attributed to the reestablishment of biologic width following subcrestal placement might be unavoidable.