ABSTRACT
Increasing PFM restorations longevity is one of the objectives in restorative dentistry and marginal fitness is an important factor to gain this purpose. In this study the effects of heat treatment on marginal fitness using both base metal and precious alloys are surveyed. Forty wax pattern on 40 standard model has been provided. Thirty of them with base alloy and 10 with precious alloy were cast. After divesting, marginal gap for each model have been measured [reflective microscope x 200]. Then samples were divided into 4 groups as follows: Group 1: Cold working- oxidizing- marginal gap measuring. Group 2: Reinvesting the model- heat treating at 1100°C for 20 minutes- ensuing stages same as group 1. Group 3: These samples were made from precious alloy and all procedures were followed as group 2. Group 4: Oxidation- gap measurement - ensuing stages same as group 1. Data were analyzed by ANOVA, T-test and Duncan test. Mean marginal gap in group I was the most and in group III was the least. Mean marginal gap in group II was Lesser than IV and in base alloy was more than precious. Heat treatment of metal framework make marginal adaptation better. If metal framework is reinvested and heat treated before any cold working and oxidization, marginal adaptation will improve