Abstract
ABSTRACT Objective The aim of this study was to evaluate, in vitro, the union stability of resin cements to the dental substract through microtensile bond strength (µTBS) analysis and scanning electron microscopy (SEM). Methods Fifty-four third human molars, stored in water for a short (24 hours) and long period of time (1 year) presented a flat oclusal superficial dentin. The teeth were distributed in six different groups: G1- Panavia F2.0/Kuraray; G2- RelyXUnicem/3M ESPE; G3- G-Cem/GC; G4- Biscem/ Bisco; G5- Panavia F2.0/Kuraray without pre-treatment and G6- Multilink Sprint/Ivoclar-Vivadent which were adhered to its respective indirect resin composite restoration, (G1- Clearfil AP-X/Kuraray; G2- Filtek Z350/3M ESPE; G3- Gradia Direct X(tm)/GC; G4- Aelite(tm)/ Bisco; G5- Clearfil AP-X/Kuraray; G6- Tetric Ceram/ Ivoclar-Vivadent). The resin blocks were cemented and the sticks were obtained by tooth, with an area of adhesive interface of 0,8mm² (±0,2). Results The mean values, submitted to Mann-Whitney and Kruskal-Wallis tests (α = 5%) were in MPa after 24 hours: G1 = 9.66 (A), G2 = 13.37 (A); G3 = 15.89 (A); G5 = 4.18 (B); G6 = 11.01 (A) and after 1 year: G1 = 9.75 (A), G2 = 11.73 (A); G3 = 20.10 (B); G5 = 6.80 (A); G6 = 21.09 (B). All G4 group presented pretest failures. Conclusion During the one year period, with the exception of BisCem, the self-adhesive resin cements were a favorable alternative for the adhesive cementation, standing out among these, the G-Cem and Multilink Sprint.
Highlights
The clinical success of indirect restorations is attributed to the effective union between the mineralized tissues and luting systems, as defined by the combination of resin cement and adhesive agent
Discontinuities were present along the interface with dentin and porosities could be noticed within the cement layer (G2), the hybrid layer was thin to undetectable and no tags were formed (Figure 2B)
The primer of Panavia F2.0 consists of three amphiphilic monomers (HEMA, MDP and 5-NMSA) with low molecular weight, the latter being responsible for the demineralization of the dentin
Summary
The clinical success of indirect restorations is attributed to the effective union between the mineralized tissues and luting systems, as defined by the combination of resin cement and adhesive agent. Adhesion degradation occurs via enzymatic attack of the collagen fibers not protected by the adhesive and dissolution of the resin components infiltrated into the dentin matrix. When acid etching agents are used to remove the smear layer, resulting in demineralization of the dentin surface, there is a risk that, the adhesive does not fully enclose the collagen fibers, which remain exposed[7]. Such fibers become susceptible to the action of proteolytic enzymes present in the human dentin - endogenous metalloproteinases (MMPs) - resulting in the dissolution of the hybrid layer. The dissolution of the adhesive components can occur if there is an incomplete polymerization of the adhesive on the hybrid layer due to the presence of residual water in dentin during its application
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