The Effect of Different Screw Angulations on the Fracture Resistance of Implant Zirconia Single Crowns Made on Two Different Implant Platforms

Abstract

Purpose: The aim of this study was to investigate the effect of different implant screw channel angulation and implant platform on the fracture resistance of zirconia abutments without artificial aging.

Materials and Methods: ten implant replicas were mounted in printed resin block at 30 degrees angulation to vertical axis for each group. Sixty samples of NobelBiocare® conical connection implant restorations were divided into two implant platforms (regular and narrow platform), then each platform consisted of three different angulation of screw access channels (0-degree, 15-degree, and 25-degree). #8 implant single restoration was designed with Exocad and used this design as a template to fabricate every restoration for each sample to make sure that every restoration has the same dimension. The STL files for each group (N0, N15, N25, R0, R15, R25) were sent to the milling center to fabricate screw-retained monolithic 3Y-TZP single crown restorations. After that, the restorations were bonded to Dynamic TIBASE® abutment and torqued to 25Ncm on implant replicas that were mounted on resin blocks. The universal testing machine was used to test the fracture strength of each sample with 5mm/min crosshead speed. Fracture strengths were recorded in Newtons (N). The peak force measured prior to screw loosening or permanent deformation at the connection of the implant abutment was recorded for each specimen. All statistics and analyses were computed using SPSS software (SPSS Statistics version 28.0, IBM). Due to non-normal distributions, non-parametric Kruskal Wallis test for multiple tests were performed between and within groups comparisons with an α = .05 for all tests.

Results: The median compressive force values for all the specimens were 691.679N with an interquartile range of 150.9713N. The statistical analysis revealed no significant difference between and within each group (p > .05).

Conclusion: Neither angulation of the screw access channel nor the size of the connection platform of Nobel conical implant affect the fracture strength of the monolithic 3Y-TZP zirconia restoration on Dynamic TIBASE® angulated screw channel abutment.