Removal torque of a two-piece zirconia abutment with a novel titanium component in an internal connection implant system after dynamic cyclic loading

Abstract

IntroductionVarious ceramic materials have been replacing metals in prosthetic fields, including crowns, fixed partial dentures and implant restorations, because of their biocompatibility and optical qualities. When these ceramics were used, the soft tissue appeared more similar to the natural color and the bluish appearance of cervical soft tissues as encountered with metal restorations would be avoided.1 As the esthetic demands of dental patients increase, attempts to use zirconia materials for fabricating monolithic crowns in the posterior region have been widely accepted because of their mechanical properties and biocompatibility. However, when selecting implant abutments for the posterior region, zirconia abutments were not preferred over titanium abutments. 2-4 When using internal connection zirconia abutments, the implant-abutment connection area was vulnerable to cracking or fracture. 5 The development of various zirconia Purpose: The aim of this study was to evaluate screw removal torque of the two-piece zirconia abutment with the novel titanium component compared to the conventional onepiece titanium abutment in the internal connection implant before and after dynamic cyclic loading. Materials and methods: Two types of the abutment assemblies with internal connection were prepared and divided into the groups; titanium abutment-titanium abutment screw assemblies as control, and zirconia abutment-titanium socket-titanium abutment screw assemblies as experimental group. A total of 12 abutments and implants were used of six assemblies each group. Each assembly was tightened to 30 Ncm. A cyclic load of 300 N at an angle of 30 degrees in reference to the loading axis was applied until one million cycles or failure. The removal torque values (RTVs) of the abutment screws were measured with a digital torque gauge before and after cyclic loading. The RTVs of the pre load and post load were analyzed with t-test, and P-values < .05 were considered statistically significant. Results: The assemblies of both groups survived all after the dynamic cyclic loading test without screw loosening. The statistically significant differences were found between the mean RTVs before and after the cyclic loading in both groups (P < .05). The RTV differences for the control and the experimental group were -7.25 ± 1.50 Ncm and -7.33 ± 0.93 Ncm, respectively. Statistical analysis revealed that the RTV differences in both groups were not significantly different from each other (P > .05). Conclusion: Within the limitation of this study, the two-piece zirconia abutment with the titanium component did not show a significant RTV difference of the abutment screw compared to the titanium abutment after dynamic cyclic loading. (J Korean Acad Prosthodont 2017;55:151-5)