Abstract: Objective To investigate whether there is a difference in the marginal bone loss (MBL) of purely conical retained implants with different initial biological widths (IBW). Methods Eighty-three patients with 122 implants (244 initial biological width sites mesial and distal aspects) who underwent implant restorations in the Fourth Affiliated Hospital of Nanchang University from January 2018 to December 2020 were selected for retrospective analysis. The initial biological widths were divided into four groups, A(1.24~3.56 mm), B(3.59~4.33 mm), C(4.36~5.21 mm), and D(5.23~8.53 mm), according to the different sizes, and the MBL was observed by taking imaging data at the the immediately post-surgery (T1), immediately post-prosthesis delivery (T2), and 3~5 year follow-up (T3), to explore whether the different initial biological widths of the purely taper-retained implant system would affect the peri-implant MBL. Results In the T1-T2 period, MBL was significantly lower in group A than in groups C and D (P<0.05), and in group B than in group D (P<0.05).In the T1-T3 period, MBL was significantly lower in group A than in group D (P<0.05).In the T2-T3 period, MBL was not statistically different among the four groups (P>0.05). In the comparison of mucosal thickness subgroups, there was no significant difference in MBL between thin and thick gingival sites in groups A and B (P>0.05), in group C, thin gingival sites showed more bone loss in the T1-T2 and T1-T3 periods compared to thick gingival group (P<0.05), and thin gingival group sites showed more bone loss in the T1-T2 period compared to thick gingival group in group D (P<0.05). Conclusion More marginal bone loss was observed at sites with larger IBW (≥4.36 mm) after implant placement to the stage of completion of prosthetic restoration, and the IBW of the simple taper-retained implant system has no significant effect on the MBL after functional loading; in the bone remodeling stage, the thicker gingival biotypes can inhibit the MBL to a certain extent compared with the thinner gingival biotypes; we recommend implanting purely conical retained implants to a subosseous depth of ≥2 mm in order to avoid early exposure of implant threads.

Key words: Taper-retained implant, Biological width, Mucosal thickness, Subcrestal placement depth, Marginal bone loss