محسن نوری ساری

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.

Preventing enamel demineralization around brackets is a concern for orthodontists. Fluoride releasing materials have been recommended to overcome this problem. The aim of this study was to evaluate the effect of incorporating nano-hydroxyapatite (NHA) into resin modified glass ionomer cements (RMGIC) on ceramic bracket debonding. In this experimental study, 80 human premolars were divided into 4 bonding groups as follows: group 1: Transbond XT (control group), group 2: Fuji II LC (RMGIC), group 3: 5% NHA added to RMGIC and group 4 10% NHA added to RMGIC. After enamel etching, ceramic brackets were bonded. The shear bond strength (SBS) and the adhesive remnant index (ARI) were calculated for each group. The data were analyzed using one-way ANOVA, Tukey’s post hoc HSD test and the Kruskal Wallis test. According to ANOVA, 10% NHA added to RMGIC had a significantly lower SBS compared to other groups (11.93±2.11) but no significant difference was found among the remaining groups. The mean SBS was 17.33±4.07 in group 1, 17.22±3.55 in group 2 and 16.56±2.59 in group 3. According to ARI, the predominant failure mode in RMGIC groups was cohesive. Resin modified glass ionomer cements containing 5% NHA can be as effective as composite resins for bonding ceramic brackets.