| dc.description.abstract | Marginal adaptation of crowns is an important factor affecting its clinical acceptability and durability. Lack of marginal adaptation results in the exposure of cement to the oral environment and its dissolution with bacterial plaque aggregation, recurrence of caries, and inflammation of gingival tissues. Purpose: The purpose of this study was to evaluate marginal adaptation of T-3 and Supremcast V base metal alloys before and after porcelain firing. Material and Method: In this experimental in vitro study, a sound maxillary first premolar was prepared with chamfer and shoulder/bevel finish lines in palatal and buccal surfaces, respectively. Then the metal dye was fabricated. Three points in the buccal and 3 points in the palatal surfaces were marked 1 mm apical to the margin. Twenty impressions were taken from metal dye by polyether impression material. After cast preparation, 10 frameworks were fabricated with T-3 and 10 frameworks with Supremcast V alloy. Marginal adaptation between the framework and the marked point on metal dyes were measured in vertical dimension before and after porcelain firing. Paired sample t-test was used to evaluate marginal adaptation of each alloy before and after porcelain firing. Comparison of differences in marginal discrepancies of various finish lines was carried out by ANOVA. In this study statistical significance was defined at p<0.05. Results: Before porcelain firing: The differences in marginal discrepancies in the buccal surface with shoulder/bevel finish line significant (p=0.148) and palatal surface with chamfer finish line (p=0.868) were not statistically significant. After porcelain firing: The differences in marginal discrepancies in the buccal surface with shoulder/bevel finish line were significant (p=0.001) and palatal surface with chamfer finish line (p=0.868) were not statistically significant. The mean marginal discrepancies of buccal and palatal surfaces with the two alloys were significantly lower before porcelain firing in comparison with those after firing (p<0.001). Conclusion: The results indicated that thermal cycles affect marginal adaptation and alloy and finish line type do not affect it. It was also concluded that marginal adaptation of the two alloys are clinically acceptable. | |
