A retrospective study of 12,538 internal conical connection implants focused on the long-term integrity of implant-abutment complexes

Objective: To evaluate the long-term integrity of implant-abutment complexes in implant systems with two internal conical angles.

Material and methods: 12,538 bone-level implants of two systems placed between January 2012 and December 2018 were retrospectively analyzed. Cumulative abutment/implant fracture rates in systems with larger (LA, 7.5°) and smaller (SA, 5.7°) internal conical angles were estimated using the Kaplan-Meier analysis and compared between groups. The association between implant systems and jammed abutment retrievability was evaluated by multivariable generalized estimating equation logistic regression modeling.

Results: For LA, the 8-year cumulative incident rate was 0.10% (95% confidence interval (CI): 0-0.24%) for implant fracture and 0.26% (95% CI: 0.11%-0.41%) for abutment fracture, demonstrating a significant difference in gender (p = .03), implant diameter (p = .01), jaw (p = .006), and antagonist tooth (p < .001). For SA, the 8-year cumulative incident rate was 0.38% (95% CI: 0-0.79%) for implant fracture and 2.62% (95% CI: 0.05%-5.13%) for abutment fracture, which was influenced by implant diameter (p < .001) and site (p = .03). The cumulative implant/abutment fracture rate was lower for LA implants, particularly for LA implant-supported single crowns (SCs) (p < .05). The abutment-retrieval success rate was 92.9% for LA and 57.1% for SA (p = .055).

Conclusion: LA implants exhibited a lower incidence of fracture in abutment-implant complexes and a relatively higher retrievability success rate for jammed abutments.