Abstract
The aim was to evaluate the influence of different dentin preparation mode in the smear layer characteristics (SL), hybrid layer (HL), and microtensile bond strength (µTBS) to dentin with two resin cements. The occlusal dentin of 120 third molars was exposed. The teeth were divided into 4 groups (n=30) according to the dentin preparation mode: 1- fine grain diamond bur; 2- coarse grain diamond bur; 3- multi laminate carbide steel bur; and, 4- ultrasonic CV Dentus diamond bur. Each treated dentin group was divided into 2 sub-groups (n=15) according to the resin cement: (1) RelyX U200 and (2) RelyX ARC. Resin composite blocks were cemented on dentin. After storage at 37o C for 24 h, beams with a cross section area of 1.0 mm2 were obtained, and tested in a universal testing machine at a crosshead speed of 0.5 mm/min. Two additional teeth for each sub-group were prepared to analyze the SL and HL on a scanning electron microscopy. According to Kruskal-Wallis test and Dunn tests, there was no significant difference in µTBS among the rotary instruments within each resin cement group. RelyX ARC obtained higher µTBS values compared to RelyX U200 (p<0.05). RelyX ARC formed evident HL, which was not observed for RelyX U200. The dentin mode preparation did not influence the µTBS of the resin cements. The SL was different for all instruments. The cementing agent is more determinant in the hybrid layer formation and bond strength to dentin than the instruments applied on dentin.
Highlights
In the last decades, the resin cements became more popular and reliable
There was no significant difference in μTBS among the instruments within each resin cement group
Mixed failure was observed in RelyX ARC groups and adhesive failure was predominant in RelyX U200 groups
Summary
The resin cements became more popular and reliable. Their evolution has resulted in different kind of materials that vary mostly in the manner of application, as well as some differences in composition [1]. Self-adhesive resin cements have been used in a large range for all kinds of indirect restorations. They contain acid monomers that remove partially the smear layer, resulting in micro-mechanical retention to the tooth structure. Conventional resin cements require surface pretreatment with etching followed by application of a bonding system
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