000) and Group II (P=0.000) but in Group III three consecutive adhesive applications were significantly decreased the microleakage in dentinal margins so there was no statistically significant difference (P=0.051) www.selleckchem.com/products/carfilzomib-pr-171.html between enamel and dentinal marginal microleakage scores in this group. DISCUSSION Clinical trials remain the gold standard in evaluating the performance of dental materials but it must also take into consideration that the products under investigation may become absolute by the time useful clinical data are collected. Thus, preclinical screening via laboratory tests is still an important tool for the evaluation of dentin adhesives.18 Clinicians and researchers use microleakage as a measure for assessing the performance of restorative materials in the oral environment.

Different techniques are used for microleakage evaluation, but the most employed method is the migration of dye along the tooth/restoration interface.19�C21 Although this method is simple, economic, and fast technique, the subjectivity of reading the specimens has been noted as a shortcoming related to this methodology.22 Despite the continuing evaluation of adhesive systems, up to now no available adhesive technique can produce predictable results when the preparation margins are located in dentin.22�C24 Contraction stresses generated during placement of a composite restoration contribute significantly to early marginal leakage, especially in dentin.25 The lower bond strength obtained in dentin is not strong enough to counteract the stress developed during polymerization shrinkage which impairs the sealing capacity.

26 The conventional Class V cavity employed in this study represents a great challenge to the adhesive systems used due to the high C-factor.27,28 In the present study, higher leakage was detected in dentin when compared to enamel in Group I and II. This finding is in agreement with some authors who used different combinations of dentin bonding agents and resin based composites in both Class II and Class V restorations29�C32 but in Group III there was no difference in enamel and dentinal margins (P=0.049) and this finding is due to the decreased microleakage at the dentinal margins and increased microleakage in enamel margins after three consecutive adhesive applications. The higher leakage scores detected in dentin when compared to enamel in Group I and II, can be related to the composition of these two tissues.

Bonding to enamel is relatively simple process without major technical requirements or difficulties. On the other hand, bonding to dentin presents a much greater challenge. Several factors account for these difference between enamel and dentin bonding whereas enamel is a highly mineralized tissue composed of more than 90% (by volume) GSK-3 hydroxyapatite. Dentin contains a substantial proportion of water and organic materials, it presents a moist surface which impairs the bonding mechanism.