A comparative evaluation of shear bond strength of porcelain fused to metal substructure fabricated using conventional and contemporary techniques: an in vitro study

Base metal alloys due to their low cost, are being used more often as the substructure because of their good mechanical properties, excellent metal ceramic bonding and biocompatibility. The bonding of porcelain to metal is an important point to be considered for the success of the restoration.

To compare and evaluate the shear bond strength of porcelain fused to metal substructure fabricated using conventional and contemporary techniques.

Thirty sample discs were fabricated – 10 of cast nickel chromium alloy, 10 of cast cobalt chromium alloys and 10 of laser sintered cobalt chromium alloy. Conventionally used feldspathic porcelain was used and fired over the metal discs. These samples were placed in a specially fabricated jig, which was held in a universal testing machine. The samples were subjected to shear stress until they fractured and the readings were noted. The fractured surface of the sample was then viewed under stereomicroscope.

The mean shear bond strength was highest in group C (porcelain fused to laser sintered cobalt chromium), followed by group A (porcelain fused to cast nickel chromium) and group B (porcelain fused to cast cobalt chromium) which was the least. The level of significance was fixed at p < 0.05. After applying Student's Unpaired ‘t’ test there is no significant difference in shear bond strength in group A compared with group B, highly significant in group A and group C and very highly significant in group B and group C.

All the three groups showed adequate, but laser sintered cobalt chromium alloy had the highest shear bond strength to porcelain. Nickel chromium alloy fabricated by conventional casting method showed lesser values of the shear bond strength, followed by cobalt chromium alloy fabricated by conventional casting, which had the least shear bond strength.