Abstract
Objective: To assess the short-term effect of two in vitro erosive challenge protocols on the bond strength of metal orthodontic brackets on bovine enamel. Methods: Sixty bovine incisors were selected and randomly divided into six groups: AS7 (artificial saliva - 7 days, Control Group); CC7 (Coca-Cola™ - 7 days); LJ7 (lime juice - 7 days); AS30 (artificial saliva - 30 days, Control Group); CC30 (Coca-Cola™ - 30 days); LJ30 (lime juice - 30 days). Microhardness testing was performed prior to the erosive challenge to verify the standardization of samples. Immersion was performed 4x/day for five minutes, for either 7 or 30 days. After immersions were concluded, the brackets were bonded and shear bond strength was assessed after 48 hours. The Adhesive Remnant Index (ARI) was also assessed. Data were analyzed by two-way ANOVA, followed by Tukey’s post-hoc and Student’s t test for paired samples, and the Kruskal-Wallis non-parametric test (α = 5%). Results: The mean and standard deviation of microhardness testing of total samples were 281.89 ± 44.51 KHN. There was no statistically significant difference in shear bond strength for the time factor (7 or 30 days; F5.54= 0.105; p = 0.901). However, there was a statistically significant difference for the solution factor (F5.54= 6.671; p = 0.003). These differences occurred among solutions of Saliva x Coca-Cola™ (p = 0.003) and Coca-Cola™ x Lime Juice (p = 0.029). The assessment of the Adhesive Remnant Index showed no significant difference between groups. Conclusions: The immersion time used in the erosion protocols did not affect the bond strength of brackets to teeth. Coca-Cola™ induced significantly higher shear bond strength values than lime juice and artificial saliva. However, the short term effects of 7/30 days in this in vitro study may not be extrapolated for in vivo ones. Clinical studies should be conducted, substantiating the laboratory results.
Highlights
Dental erosion is a problem with increasing incidence in the worldwide population.[1]
The bond strength values obtained for the group immersed in Coca-ColaTM were significantly higher when compared to those of the groups subjected to Artificial Saliva and Lime Juice
The results of this study indicated that the storage in the erosive solutions (Coca-ColaTM and lime juice) did not affect the bond strength of the brackets to bovine enamel
Summary
Dental erosion is a problem with increasing incidence in the worldwide population.[1]. Several commercially available acidic beverages accelerate the erosion process, such as citric acidbased[4,5,6,7,8] and cola-based[3,4,7,8,9,10,11,12,13,14] drinks, energy drinks,[15] and isotonic drinks.[4] The erosive potential of these beverages is related to their low pH and low buffering capacity. Acidic foods and beverages with pH lower than 5.5 may cause the dissolution of hydroxyapatite and fluorapatite present in tooth enamel.[5]
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