In Vitro Comparative Evaluation of Bond Strength of CAD/CAM Monolithic Zirconia Copings Influenced by Luting Agents and Finish Line Design.

AIM: The aim of the in vitro study was to comparatively evaluate the bond strength of CAD/CAM monolithic zirconia copings using three luting agents and two different finish lines. MATERIALS AND METHODS: For the evaluation of bond strength, 60 extracted human maxillary first premolars were prepared to receive CAD/CAM monolithic zirconia copings. They were randomly divided into six groups of 10 samples each to receive CAD/CAM monolithic zirconia copings to bond with three different luting agents on two different finish lines. The luting agents used were RelyX U200, RMGIC, and Maxcem Elite with finish lines which were incorporated were 90° shoulder and radial shoulder finish lines. The tensile bond strength for all 60 samples was tested using the universal testing machine. RESULTS: Between and within the group differences in tensile bond strength were analyzed using one-way ANOVA test of significance with Tukey's post-hoc analysis. The statistical analysis revealed that the CAD/CAM zirconia copings used a combination of 90° shoulder and RelyX U200 as the luting agent (Group II) which offered the maximum bond strength. CONCLUSION: Within the constraints of this study, it could be concluded that CAD/CAM monolithic zirconia copings luted with RelyX U200 cement on a 90° shoulder finish line is the preferred method, taking the bond strength into consideration. CLINICAL SIGNIFICANCE: The results of this study can be extrapolated into a clinical scenario to help the clinician decide the most apt combination of finish line design and the luting agent to achieve superior bond strengths in CAD/CAM zirconia crowns and fixed dental prosthesis.

Comparison of Tensile Bond Strength of Addition Silicone with Different Custom Tray Materials Using Different Retentive Methods.

AIM: To compare the bond strength of addition silicone with different commonly used custom tray materials by means of different retentive methods (mechanical, chemical, and a combination of chemical and mechanical methods). MATERIALS AND METHODS: Fabrications of 90 samples of different tray resin materials were done using an aluminum mold. They were divided into three main groups. Perforations, adhesive application, and a combination of both were done according to the grouping of samples. Polyvinyl siloxane material (medium body) was loaded over the samples. A universal testing machine with a crosshead speed of 5 mm/minute was used to determine the tensile bond strength of tray resin samples to medium body impression material. Based on these values, Student's-test, group statistics, and ANOVA test were used for statistical analysis. RESULTS: Visible light cure (VLC) resin showed the highest bond strength in chemicomechanical methods. This was followed by repair resin material. Tray resin material showed poor bond strength in all three retentive methods. The mechanical method was the least retentive in all three resin materials. CLINICAL SIGNIFICANCE: VLC tray resin material can be used with chemical and mechanical retention in clinical situations to make predictably accurate elastomeric impressions. CONCLUSION: It was concluded that VLC tray resin shows good bond strength with polyvinyl siloxane impression material when both mechanical perforations and adhesive applications were done.