Marginal adaptation of the three indirect crowns

Good marginal adaptation is a prerequisite for a successful crown restoration while the incidence of microleakage, caries, damage to the base teeth and periodontal diseases is facilitated when this criteria is not achieved. Therefore, the present study determined the marginal gap in the porcelain crowns compared to indirect composite restorations of GC Gradia and Signum. In this invitro experimental study, 30 impressions were taken in the similar conditions and randomly assigned to receive porcelain crowns (Noritake super porcelain Ex-3) or indirect composite crowns of GC Gradia and Signum when no fluid and porosity were noted on them. The crowns were fitted on the master metal die and assessed by the stereomicroscope after complete sitting and finishing line preparation. The assessments were carried out on 8 points 1mm from the finishing line (buccal, lingual, mesial, distal, mesiobuccal, distobucaal, mesiolingual and distolingual). Then, 8 jigs were fabricated and total 240 readings were made. The values were converted to micron and the statistical comparisons were made using nonparametric Kruskal-wallis and Mann-whitney U tests. Marginal gap of porcelain crowns was29/08 ± 9/38μm and 84/53± 15/47μm on the lingual and disto lingual points andtheGC gradia indirect composite, was 43.63±13.40μm and 74.53±28.03μm on the distal and distolingual points as well as 39.08±17.68μm and 95.44±30.66μm on the distal and mesiolingual aspects of the Signum indirect composites respectively.No significant differences were noted between the three crowns brands on the mesial, distal, mesiobuccal, distobuccal, and mesiolingual aspects.only 3 points(buccal, lingual and disto lingual) had significant differences. Regarding clinically acceptable values of marginal gaps mentioned in the literature,porcelain jacket crowns and indirect composite crowns possesses the necessary criteria of marginal gap and can be successfully used for crown restorations.