Abstract
The purpose of this study was to determine the influence of hydrochloric acid on surface roughness of composite resins subjected to brushing. Sixty samples measuring 2 mm thick x 6 mm diameter were prepared and used as experimental units. The study presented a 3x2 factorial design, in which the factors were composite resin (n=20), at 3 levels: microhybrid composite (Z100), nanofilled composite (FiltekTM Supreme), nanohybrid composite (Ice), and acid challenge (n=10) at 2 levels: absence and presence. Acid challenge was performed by immersion of specimens in hydrochloric acid (pH 1.2) for 1 min, 4 times per day for 7 days. The specimens not subjected to acid challenge were stored in 15 mL of artificial saliva at 37 oC. Afterwards, all specimens were submitted to abrasive challenge by a brushing cycle performed with a 200 g weight at a speed of 356 rpm, totaling 17.8 cycles. Surface roughness measurements (Ra) were performed and analyzed by ANOVA and Tukey test (p≤0.05). Surface roughness values were higher in the presence (1.07±0.24) as compared with the absence of hydrochloric acid (0.72±0.04). Surface roughness values were higher for microhybrid (1.01±0.27) compared with nanofilled (0.68 ±0.09) and nanohybrid (0.48±0.15) composites when the specimens were not subjects to acid challenge. In the presence of hydrochloric acid, microhybrid (1.26±0.28) and nanofilled (1.18±0,30) composites presents higher surface roughness values compared with nanohybrid (0.77±0.15). The hydrochloric acid affected the surface roughness of composite resin subjected to brushing.
Highlights
Dental erosion is one of the main factors for tooth wear [1] that occurs without bacterial involvement by chemical dissolution of the dental structure [1,2,3] by acids [1]
The association between gastroesophageal reflux and brushing was simulated, whereas other external factors that could contribute to tooth and restorative material erosion were eliminated
The first null hypothesis was rejected, since surface roughness value was higher for specimens immersed in hydrochloric acid compared with those that were not subjected to acid challenge
Summary
Dental erosion is one of the main factors for tooth wear [1] that occurs without bacterial involvement by chemical dissolution of the dental structure [1,2,3] by acids [1] These acids are derived from the dietary and endogenous factors, such as eating disorders and gastroesophageal reflux [1,4]. Dental erosion can damage the physical and mechanical properties of the composite [3], leading to organic matrix degradation and exposure of the inorganic filaments [7]. These changes lead to increase of surface softening and roughness, which are responsible for the decrease in restoration durability [8]
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