Effect of dental implant macrogeometry on the probability of survival and strain distribution of an implant-abutment set.

Abstract

Background: The effect of the macrogeometry of dental implants with double trapezoidal threads on the probability of survival and the long-term success of oral rehabilitation is unclear.

Objectives: The purpose of this in vitro study was to evaluate the effect of dental implant macrogeometry on the probability of survival, failure mode and strain distribution of an implant-abutment set.

Material and methods: Dental implants were divided into 2 groups according to their macrogeometry (n = 21 per group): trapezoidal thread (control group); and double trapezoidal thread (test group). The macrogeometry analysis was performed with the use of computed microtomography (n = 1). The specimens were subjected to single load to failure (SLF) (n = 3), which permitted the step-stress profiles for design-based step-stress accelerated life testing (SSALT) (n = 18). The probability of survival and reliability for a mission of 50,000 cycles were calculated at 100 N and 150 N. The scanning electron microscope (SEM) was used to analyze the failure mode of the implant-abutment set. The digital image correlation (DIC) (n = 3) was performed using the implant-abutment set embedded in a polyurethane resin subjected to a static load of 250 N in axial and non-axial positions.

Results: No statistically significant differences were observed between the groups with respect to the probability of survival. All groups showed a reliability level higher than 95% at 100 N, while a decrease in reliability was observed at 150 N. The Weibull modulus and characteristic resistance exhibited no significant differences between the groups. The β mean values (control = 0.66, test = 0.33) indicated that failures were dictated by material strength. The SEM revealed an abutment and implant body fracture, characterized by fracture initiation on the lingual surface that subsequently propagated to the opposing buccal side. In the context of non-axial loading, the test group exhibited a higher concentration of tensile strain in the cervical region (152.05 μs), while the control group exhibited a predominance of compression strain (-800.00 μs).

Conclusions: The macrogeometry of dental implants did not influence the failure mode and probability of survival, but modified the strain distribution of the implant-abutment set.