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Background: Metal ceramic restorations are popular in restorative dentistry due to their better esthetics and strength. Plaque removal is easier when gingival tissues are in contact with vacuum-fi red glazed porcelain. However, failures due to cohesive fracture within porcelain or adhesive fracture at porcelain-metal-phase boundary are frequent.

Aims and Objectives: The aim of this paper is to find out if varying the temperature and the duration of oxidation heat treatment would have any effect on the shear bond strength of porcelain to Co-Cr alloy.

Materials and methods: 80 samples of wax pattern of 6.4mm diameter and 1.6mm thick were casted cleaned and polished using silicon carbide papers of different grits. The samples were divided in different groups and were subjected to oxidation heat treatment at 920°C, 950°C, 980°C and 1010°C for a duration of 3, 4, 5 and 6 minutes respectively. Then single layers of wash opaque, opaque and dentinal porcelain were applied to form a porcelain cylinder, which was later subjected to shear bond test in a Universal testing machine.

Results: The statistical analysis showed that the samples subjected to the oxidation heat treatment at 980°C for duration of 5 minutes exhibited the highest bond strength with the Mean of the Maximum Load value of 414.69640 N. The samples fi red at 950°C and 980°C showed higher bond strength as compared to the samples fi red at 920°C and 1010°C. The samples fi red for the duration of 4 to 5 minutes showed better strength than the samples fired for the duration of 3 or 6 minutes.

Conclusion: From this study we can say that the variation in time and temperature has an effect on the bond strength of porcelain to metal and the cohesive failure seen within porcelain fi red at 980°C for 3, 4 and 5 minutes suggests sufficient bond between porcelain and metal.

Oxidation Heat Treatment, Shear bond strength, Porcelain and Co-Cr alloy