ABSTRACT
Statement of the Problem: The adhesion of resin-modified glass-ionomer [RMGI] to composite resin has a very important role in the durability of sandwich restorations. Hydroxyapatite is an excellent candidate as a filler material for improving the mechanical properties of glass ionomer cement
Purpose: The aim of this study was to assess the effect of adding micro- and nano-hydroxyapatite [HA] powder to RMGI on the shear bond strength [SBS] of nanofilled and silorane-based composite resins bonded to RMGI containing micro- and nano-HA
Materials and Method: Sixty cylindrical acrylic blocks containing a hole of 5.5×2.5 mm [diameter × height] were prepared and randomly divided into 6 groups as Group 1 with RMGI [Fuji II LC] plus Adper Single Bond/Z350 composite resin [5.5×3.5 mm diameter × height]; Group 2 with RMGI containing 25 wt% of micro-HA plus Adper Single Bond/Z350 composite resin; Group3 with RMGI containing 25 wt% of nano-HA plus Adper Single Bond/Z350 composite resin; Group 4 with RMGI plus P90 System Adhesive/P90 Filtek composite resin [5.5×3.5 mm diameter × height]; Group 5 with RMGI containing 25 wt% of micro-HA plus P90 System Adhesive/P90Filtek composite resin; and Group 6 with RMGI containing 25 wt% of nano-HA plus P90 System Adhesive/P90 Filtek composite resin. The specimens were stored in water [37 degree C, 1 week] and subjected to 1000 thermal cycles [5 degree C/55 degree C]. SBS test was performed by using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed by two-way ANOVA and Tukey test [p< 0.05]
Results: There were significant differences between groups 1 and 4 [RMGI groups, p= 0.025], and groups 3 and 6 [RMGI+ nano-HA groups, p= 0.012]. However, among Z350 and P90 specimens, no statistically significant difference was detected in the SBS values [p= 0.19, p= 0.083, respectively]
Conclusion: RMGI containing HA can improve the bond strength to methacrylate-based in comparison to silorane-based composite resins. Meanwhile, RMGI without HA has the best bond strength to silorane-based composite resins