Abstract
The objective of this study was to evaluate the bond strength to superficial (SU) and deep (D) dentin, accessed via apical (DA) or occlusal (DO), using One-Step adhesive system applied according to the manufacturer's instructions (C) or following deproteinization with 10% sodium hypochlorite (H) for 60s, after acid etching. Three sound extracted human molars were prepared for each experimental condition. Restorations were performed using Z100 in 2mm increments, each one being light-cured for 40s. Teeth were longitudinally sectioned to obtain stick-shaped specimens with a cross-sectional area of 0.8mm², which were submitted to bond strength test (0.6mm/min). Results obtained after statistical analysis using a two-way ANOVA (substrate vs. surface treatment) and Tukey's test were: SU (35.4 ± 12.3), DO (26.5 ± 8.5), DA (26.1 ± 10.2) following conventional surface treatment, and SU (28.82 ± 12.7), DO (24.3 ± 8.3) and DA (23.5 ± 8.5), after surface treatment using sodium hypochlorite. The interaction of the factors was not significant (p>0.05). However, the main factors were significant (p<0.05). Mean bond strength values in superficial dentin were statistically superior to deep dentin (p<0.05), although no statistically significant difference was observed between the two via of access to deep dentin (SU>DO=DA). The conventional surface treatment resulted in higher bond strength values than the sodium hypochlorite treatment (p<0.05). It was concluded: 1) bond strength values were higher in superficial dentin, 2) no difference was found between the two deep substrate preparations, and 3) the application of sodium hypochlorite following dentin acid etching may reduce bond strengths.
Highlights
The dentin acid etching was firstly proposed by Fusayama, et al.[8] (1979) and allowed the complete elimination of smear layer and smear layer plugs
The mean microtensile bond strength value obtained for superficial dentin (SU) was statistically superior to both deep dentin preparations (p
Similar results were observed between mean values obtained in both deep preparations (p>0.05), indicating that the access via had no influence on microtensile bond strength results as noted in table 3
Summary
The dentin acid etching was firstly proposed by Fusayama, et al.[8] (1979) and allowed the complete elimination of smear layer and smear layer plugs This approach facilitated the penetration of adhesive systems into inter and intratubular dentin, resulting in the formation of a hybrid layer and resin tag formation[15]. No objective criteria about how to keep the ideal moisture, in which maximum infiltration of resin monomers can occur is yet to be addressed. It seems that there is a strong relationship between the composition of each employed bonding agent and the ideal moisture degree on dentin surface. A different degree of surface moisture is necessary for each adhesive system, making the establishment of such specification difficult due to the great variety of materials present in the market[21,22]
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