Marginal Microleakage in Nickel-Chromium Copings Fixed with Different Resin Cements - A Comparative Study

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Objective: To evaluate marginal microleakage at the interface of teeth prepared for full metal-ceramic crowns and copings fixed with different resin cements, using methylene blue staining. Method: Forty teeth were prepared and impressions were obtained to fabricate Ni-Cr copings. The sample was assigned to four groups, according to the luting agent: Group I: coping cemented with Scotchbond and RelyX ARC; Group II: copings fixed with Single Bond and RelyX ARC; Group III: copings fixed with RelyX U100; Group IV: copings fixed with Pavavia F. The teeth were stored in distilled water at 37 oC for six months, subjected to a thermocycling regimen and stored again in water for another six months. The tooth surfaces were rendered waterproof except for the margins and were immersed in a 1% methylene blue solution for 72 h. The copings were sectioned with carborundum disks and evaluated with or without resin cement on the prepared dental surface. Each face was scored 0 to 4 for leakage. Results: Analysis of the samples with cement revealed that score 0 was attributed to 65% of the samples of Group I; 52% of Group IV; 42.5% of Group II and 5% of Group III. In the analysis of samples without cement, score 0 was attributed to 95% of the samples of Group IV; 90% of Group I; 57% of Group II and 50% of Group III. Statistically significant difference among the groups was found by the Kruskal-Wallis test (p<0.05). Groups I and IV were superior to the others. Conclusion: Before and after removal of the cement, Panavia F and Scotchbond + RelyX ARC presented greater resistance to dye penetration.