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Marginal accuracy of metal copings produced with different ring casting techniques: An in vitro study

Objective: Evaluation and comparison of marginal accuracy of three porcelain fused with metal alloy using ringless and closed ring casting techniques. Materials and Methods: A total of 60 metal copings was fabricated on a metal die. Specimens were divided into two groups (Group I ringless and II ring casting techniques) of 30 patterns each. Groups are further divided into three subgroups of 10 each representing porcelain fused to metal alloys castings namely Mealloy, Wiron-99, and Bellabond plus. The measurement of fit of the metal copings was recorded by stereo photomicroscope at four different surfaces. Results: No significant difference (P < 0.001) was found when the mean vertical marginal integrity at all the buccal, palatal, mesial and distal surfaces among three porcelain fused to metal alloys for both the groups. However on comparing in between group I and group II, it showed that there is significant difference (P > 0.001). The mean of the vertical integrity for the group I (Ringless) was less than group II (Closed Ring). Conclusions: Within the limitations of the study design, it can be concluded that there is a significant difference between ringless and closed ring casting but both are clinically acceptable.