Shear strength of visible light cured-urethane dimethacrylate and polymethylmethacrylate denture base material to cobalt chromium dental prosthesis: An in-vitro study

The aim was to compare the shear strength of visible light cured-Urethane dimethacrylate (VLCUDMA) and heat cure Polymethylmethacrylate (PMMA-HC) materials when bonded to Cobalt chromium (CoCr) alloy prosthesis. A Kennedy class IV denture design was used as the standard prosthesis for all specimens. Master cast with missing maxillary incisors was prepared for framework design and duplicated to form 20 models using auto-polymerizing resin. Refractory casts were fabricated for each model and wax-ups for a standard framework design were performed. Casting of frameworks was performed using CoCr alloy and sandblasted. VLC-UDMA (group A) and PMMA-HC (group B), were built-up on the saddle area (n = 10) to standardized dimensions with a palatal groove (8 mm×5 mm×2 mm). A jig was used to affix specimens (framework with base material) in position and the denture base was subjected to shear loads until failure (Instron 825). Data was analyzed using Levene’s and t-test. The maximum and minimum failure loads were observed in group-B (1268.30±336.93 N) and group A (602.111±138.311 N) respectively. Shear strength values among group A (UDMA-VLC) and group B (PMMA-HC) were, 4.014±0.922 MPa and 8.455±2.246 MPa respectively. PMMA-HC resin demonstrated higher failure loads and shear strength as compared to VLC-UDMA when bonded to CoCr metal alloy. Clinicians should exercise caution when using VLC-UDMA in dental prosthesis with CoCr base metal alloys.