ABSTRACT
BACKGROUND: This research aims to assess the impact of oxidation heat treatment (OHT) and dual opaquing techniques on enhancing the bond strength between metal and ceramic. MATERIAL AND METHOD: Eighty rectangular patterns with dimensions of 0.5x3x25 mm (according to ISO 9693-2012) were fabricated in a custom-made silicon mold by using auto-polymerized pattern resin material. These rectangular patterns were cast using base metal alloys. The samples were split into two primary groups: group A, subjected to OHT, and group B, without oxidation treatment. Each primary group was then split up into subgroups according to the application of single layers (group A1, B1) or double layers (group A2, B2) of opaque porcelain. After pre-surface treatment and Ceramco 3 paste opaque application, dentin porcelain (Ceramco 3) was applied to the mid-region of the samples, followed by firing to achieve a standardized thickness. Flexural strength determination was conducted via a three-point bend test performed on the universal testing machine (UTM) (Instron Corp., Model 2519-107, USA), adhering to ISO standard 9693. Post-testing failure types were analyzed by morphological assessment of debonding surfaces via a scanning electron microscope (SEM). The statistical analysis was performed with SPSS version 16, incorporating ANOVA for intergroup analysis and independent t-tests for intragroup comparisons. RESULTS: Group A2 exhibited the highest mean flexural bond strength (P<0.05) at 41.85 MPa when compared to group A1 at 37.60 MPa, group B2 at 35.47 MPa, and group B1 with the least mean flexural bond strength at 30.41 MPa. SEM observations revealed cohesive bond failure for groups A1, A2, and B2 and adhesive bond failure for groups B1. CONCLUSION: It is evident that OHT and opaquing technique are important factors in determining the bond strength of ceramo-metal restorations. When combined, these techniques greatly increase the overall success and durability of metal-ceramic restorations, underscoring their significance in contemporary dental prostheses.