Abstract
The purpose of this study was to evaluate the bonding interface between a self-adhesive resin cement to in vitro eroded dentin. Seventy-two third molars were used and divided into two groups: sound dentin and in vitro eroded dentin. The in vitro erosion was performed following a demineralization protocol, in which the specimens were immersed in a demineralizing solution for 2 minutes per cycle and remineralizing solution for 10 minutes per cycle for 9 days. Both groups were submitted to four dentin surface treatments: control group (without any treatment), 2% chlorhexidine, 20% polyacrylic acid, and 0.1 M EDTA (n = 9). Blocks of resin-based composite were bonded with RelyX U200 self-adhesive resin cement applied on the pretreated dentin surfaces. The teeth were sectioned into beams (1mm2) and submitted to microtensile bond strength testing to evaluate the bond strength of self-adhesive resin cement to dentin after 24 hours and 8 months of immersion in artificial saliva. Three specimens of each group were longitudinally cut and evaluated using confocal laser scanning microscopy to analyze the dentin/cement interface. Eroded dentin showed higher bond strength values when compared to sound dentin for the 2% chlorhexidine group (p = 0.03), 24 hours after adhesion. When considering eroded dentin, the 0.1M EDTA group showed higher bond strength values with a statistically significant difference only for the control group (p = 0.002). After 8 months of storage, the present results showed that there was no statistically significant difference between the two substrates for all experimental groups (p>0.05). Analysis of the microscopy confocal showed different types of treatments performed on dentin generally increased tags formation when compared to the control group. The eroded dentin showed a significant increase in density and depth of resinous tags when compared to sound dentin. The storage of samples for 8 months seems to have not caused significant degradation of the adhesive interface.
Highlights
The focus of restorative dentistry has changed over time
Analysis of the micromechanical interaction of the adhesive interface was performed using confocal microscopy. This method evaluates the micropermeability and the sealing ability of the resin tags at the adhesive interface by using fluorescent dyes in the dental substrate and/ or resinous material [36], allowing for the evaluation of the subsurface. This is a non-destructive method which offers more details regarding the identification of the structures that constitute the adhesive interface [29] with less artefacts and decreased halo formation in the image when compared to scanning electronic microscopy [36]
The results showed that the bond strength values were generally higher after 24 hours of storage when compared to evaluation after 8 months, rejecting the third null hypothesis of the study
Summary
Caries disease was the main restorative concern; non-carious cervical lesions have increased in clinical relevance due to the significant incidence of the cases [1], especially for erosive lesions. This increase is due to the natural aging of a large part of the population, which allows teeth to be maintained longer in the mouth due to improved oral health, and increased consumption of acidic foods [2,3]. Dental erosion may be defined as an irreversible loss of dental tissue when exposed to a chemical process without bacterial involvement [4] It has a multifactorial etiology and could be intrinsic or extrinsic. The presence of abrasive substances in a dentifrice, as well as the diameter of the toothbrush bristles, could affect the erosion process [10,11]
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