[Effect of incorporating nano-hydroxyapatite and nano-zinc oxide into resin modified glass lonomer cement on metal bracket debonding]

ABSTRACT

Fluoride releasing adhesives are favorable for bracket bonding since they decrease the risk of demineralization around orthodontic brackets given that they provide acceptably high shear bond strength [SBS]. The aim of this study was to evaluate the SBS of resin-modified glass ionomer cements [RMGIC] reinforced by nano-zinc oxide [NZnO] and nano-hydroxyapatite [NHA] particles in comparison with composite resins.In this experimental study, 80 extracted human premolars were used. The teeth were randomly divided into 4 groups as follows Group 1 Transbond XT as the control group, Group 2 RMGIC [Fuji II LC], Group 3 RMGIC with 5% NHA and Group 4 RMGIC with 2% NZnO. After enamel etching, brackets were bonded. The SBS was calculated for each group. The percentage of adhesive remained on the enamel was quantified by calculating the adhesive remnant index [ARI]. The data were analyzed using one-way ANOVA and the Kruskal Wallis test.According to the results of ANOVA, there were no significant differences in SBS of groups [P=0.075]. The mean SBS in groups 1 to 4 was 15.43 +/- 4.61, 14.95 +/- 4.34, 17.97 +/- 3.65 and 17.08 +/- 3.59 MPa, respectively. According to the Kruskal-Wallis test, there were no significant differences in degree of ARI among groups [P=0.413]. The SBS was similar among all groups and adding NZnO and NHA particles had no negative effect on SBS of RMGIC. In all groups, less than half the adhesive remained on the enamel after bond failure