In different investigations, the destructive effect of ultrasonic scalers on the margins of composites has been studied, but there are very few studies on the effects of ultrasonic scalers on the microleakage of poly-acid modified composite resin and resin modified glass ionomers. The main purpose of this study was to evaluate the marginal microleakage of class V preparations restored with resin modified glass ionomer and poly-acid modified composite resin before and after scaling with an

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... onic scaler. Methods: This in vitro study was performed on 160 premolar teeth. Standard class V cavities were prepared on the buccal surfaces of the selected teeth. Occlusal and cervical margins were placed entirely in enamel and cementum, respectively. Teeth were randomly divided to two groups of eighty, each. For one half of each group, (40 teeth) resin modified glass ionomer and for the other half, polyacid modified composite resin was used. Each one of the binary groups was subdivided to two groups. First subgroup was restored with Fuji II Lc (Fuji Japan) and Vitremer (3M USA ) and the second subgroup was restored with F2000 compomer (3M USA) and Compoglass(Vivadent Germany). For bonding to enamel, dentinte,cementum Singlebond (3M USA) and Adhese 2 (Vivadent Germany) were used and all of the restorations were done according to instructions of the manufacturers. In ten teeth of each group, ultrasonic scaling was done and in the other ten teeth, scaling was not done. After that, all of the teeth were thermocycled and immersed in fuschin. After cutting the microleakage was evaluated. The data was analyzed by Mann – Whitney, Kruskal – Wallis and Wilcoxon tests and significant border was 0.05 . Results: The results showed that the degree of microleakage in enamel margins of poly –acid modified resin composites was lower than resin modified glass ionomers and in all groups and subgroups, the microleakage in enamel and cementum after scaling was significantly more than the groups without scaling. Conclusion: Use [...]