Evaluation of the effect of home bleaching gel on microleakage of different glass ionomers reinforced with micro-hydroxyapatite

AIM: This study aimed to evaluate the effect of home bleaching gel on microleakage of glass-ionomer cements reinforced with micro-hydroxyapatite (HAP). METHODS: Class V cavities prepared on the forty extracted third molars were restored in four groups (n = 10): Group 1, Zirconomer; Group 2, resin-modified glass ionomer (RMGI); Group 3, Zirconomer + micro-HAP (20% WT); and Group 4, RMGI + micro-HAP (20% WT). After thermocycling (1000 cycles at 5 ± 2/55 ± 2°C, a dwell time of 30 s), each group was randomly divided into two groups. The first half was kept in distilled water and the restorations of the second half were bleached with carbamide peroxide 15% (14 days, each time 6 h/day). A uniform thickness of bleaching agent (0.5–1 mm) was applied on the surfaces of the restorations, extending 1 mm beyond the margins, and the bleaching agent was exchanged every 6 h. Microleakage was evaluated using dye penetration technique that is based on the amount of dye penetration (0.5% basic fuchsine solution) from the occlusal/gingival margins up to the axial wall. RESULTS: In distilled water, no significant difference was found between the occlusal microleakage scores (P > 0.05). The lowest and highest gingival scores in distilled water were observed in Group 4 and Group 3, respectively. In bleaching environment, there was no significant difference between four groups (P > 0.05). Comparing each glass ionomer in two environments revealed statistically significant differences in gingival and occlusal microleakage of Group 4 and in occlusal microleakage of Group 1 (P < 0.05). CONCLUSIONS: Micro-HAP incorporation did not affect the microleakage of the RMGI and Zirconomer in bleaching environment and their occlusal microleakage in distilled water. The lowest and highest gingival scores in distilled water were observed for the RMGI + micro-HAP and Zirconomer + micro-HAP, respectively. Bleaching procedure negatively affects the microleakage score of RMGI + micro-HAP and occlusal microleakage of Zirconomer.