Influence of the casting technique and dynamic loading on screw detorque and misfit of single unit implant-supported prostheses

Abstract

Objective. This study aimed to evaluate the influence of the casting procedure and cyclic loading of prosthetic frameworks on detorque of prosthetic screws and marginal misfit of single unit implant-supported prostheses. Materials and methods. Twenty specimens were obtained, each one consisting of a set of an implant (external hexagon 3.75 × 13 mm – Branemark type), a prosthetic abutment (entirely calcinable or overcasted UCLA) and a prosthetic screw. After the specimens were obtained, the prosthetic screws were tightened with 30 Ncm torque and released 24 h later in order to evaluate initial detorque. The screws were retightened and marginal gaps were assessed. All specimens were submitted to 10⁶ loading cycles, performed with 2 Hz frequency and 130 N load. The specimens were re-evaluated for marginal misfit and detorque after the mechanical loading (final marginal misfit/final detorque). The results were submitted to analysis of variance for repeated measurements, followed by Tukey HSD test (α = 0.05). Results. No statistically significant differences were found on detorque values of the prosthetics screws for all groups and intervals evaluated (p = 0.8922). The entirely calcinable abutments showed higher initial marginal misfit compared to the overcasted ones (p = 0.0438). There was no statistically significant difference on marginal misfit before and after mechanical loading for both groups (p > 0.05). Conclusions. It can be concluded that the overcasted abutments showed lower misfit values when compared to the entirely casted abutments. No difference was observed on detorque values of prosthetic screws. After mechanical loading there was no difference on marginal misfit and detorque between the groups.

Key Words::

• dental implant
• marginal adaptation
• cobalt–chromium alloys

Acknowledgments

This study was supported by the São Paulo Research Foundation (FAPESP 2009/18473-7) and Coordination for the Improvement of Higher Level Personnel (CAPES).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.