ABSTRACT
OBJECTIVES: The aim of this study was to evaluate the plastic deformation of the hexagonal connection, and the removal torque of the implant-abutment joint of two dental implants combined with internal or external hexagonal connection implants after mechanical cycling. MATERIALS AND METHODS: Twenty-four dental implants were used in the study. Half of the implants had internal hexagonal connections (IH; Titamax II Plus) and the other half had external hexagonal connections (EH; Titamax Ti Ex). Four groups of two types of dental implant abutments (titanium: Ti, UCLA II Plus and zirconia: Zr, fabricated by CAD/CAM; n = 6) were investigated. The abutments received a metallic crown and the settings were submitted to mechanical cycling (MC; 106 cycles, axial load, 120N). The connection surface area was measured by scanning electron microscope (SEM) images. The removal torque was evaluated and the plastic deformation of the hexagonal surface of the implant was measured by comparing the images before and after MC. STATISTICAL ANALYSIS: Paired-t test was used to analyze the data statistically at a significance level of α = 0.05. RESULTS: The torque values decreased for all groups after MC, and the hexagonal surface area decreased due to plastic deformation for IH and EH associated with Zr abutments. CONCLUSIONS: Zirconia abutments showed the worst plastic deformation of the implant connection surface and torque loosening when associated with IH implant.