The Effect of Topical Fluoride on Shear Bond Strength of Resin Modified Light Cured Glass Ionomer to the Enamel of the Primary Upper Canine: an In-Vitro Study

One of the most important goals of topical fluoride application is to prevent dental caries in children. General opinion reveals that topical fluoride has a negative effect on composite bond and adhesive materials to tooth; otherwise, it could be considered in pediatric dentistry. The aim of this research was to evaluate and compare the effect of topical fluoride on shear bond strength of resin modified light cured glass ionomer to the etched and non-etched enamel of the primary tooth under different preparing conditions. In this in-vitro experimental study, 108 primary canine teeth free of caries and crack were prepared in three main groups respectively: 1) immediately after using APF, 2) 24 hours after using APF, and 3) without using APF. Then, each main group was divided into three subgroups. The first subgroup received conditioner + GCFuii LC2, the second received GCFuii Lc2 + 3M phosphoric acid 35%, and the third one received composite 3Mz100 on the tooth surface. After thermocycling, the shear bond strength of the material on the teeth was measured by instron machine. Two- way ANOVA and Post hoc Bonferroni test was used for statistical analysis.There were no statistically significant differences between the mean shear bond strength of the groups in which APF was used and those which did not receive topical fluoride (p >0.05). There was not a statistically significant difference, between the mean shear bond strength of GC Fuji LC2, using polyacrylic acid 20% and the same material using phosphoric acid 35%. However, there was a significant difference between the strength of shear bond of the two above materials and composite 3MZ100 (p <0.001). According to the results of this study, it can be concluded that 1- Application of APF, has little effect on reducing the strength of shear bond in GC Fuji LC2 and 3MZ100 composite. Moreover, 2- Using polyacrylic acid 20% and phosphoric acid 35% have similar effects on the strength of glass ionomer GC Fuji LC2 to the primary tooth enamel.