Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 5 1 2008 03 15 23 30 M. Moezizadeh Assistant Professor, Department of Operative Dentistry, School of Dentistry, Shaheed Beheshti Univer S. Moayedi 2015 10 03 Objective: The use of presently available dentin bonding systems has greatly reduced mi-croleakage; however, the ideal situation where the adhesive resin completely penetrates the demineralized dentin is not yet achieved. The purpose was to compare the microleak-age of fifth and sixth generation bonding agents at enamel and dentinal margins. Materials and Methods: Class V cavities were prepared at the CEJ of thirty extracted human premolars. The teeth were divided into three groups (n=10). In group I, cavities were treated with Prime&Bond NT; in group II, UniFil Bond; and in group III, Prompt L-Pop bonding agents were used following which composite resin (Z100) was placed incre-mentally. The specimens were stored in an environment of 100% humidity, immersed in a fresh solution of 50% Silver Nitrate each for 24 hours and then placed in a developing so-lution for 8 hours. After rinsing and being sectioned buccolingually through the center of the restoration, the samples were evaluated under a stereomicroscope at x50 magnificationfor microleakage along occlusal and gingival margins. The data were analyzed using Kruskal-Wallis and Multiple Comparison tests. Results: There wasa significant difference between the three groups. The fifth generation dentin bonding agent (Prime&Bond NT) showed the least amount of microleakage, while the sixth generation ones (UniFil Bond and Prompt L-Pop) showed higher amounts at enamel and dentinal margins. Conclusion: Fifth generation bonding agents seem to generate better results than those of sixth generation. https://fid.tums.ac.ir/index.php/fid/article/view/142 https://fid.tums.ac.ir/index.php/fid/article/download/142/142