Abstract
OBJECTIVES: This study aimed to evaluate the microshear bond strength (µSBS) of resin-modified glass ionomer cement (RMGIC) to primary dentin and the fracture resistance of primary molars restored with RMGIC, with and without the incorporation of mesoporous zinc oxide nanoparticles (ZnO NPs) and bacterial cellulose nanocrystals (BCNCs). MATERIALS AND METHODS: A total of 100 extracted primary mandibular second molars were divided into two tests: the µSBS test (40 teeth) and the fracture resistance test (60 teeth). The µSBS test included four groups: (1) RMGIC (control), (2) RMGIC + 5 wt.% mesoporous ZnO NPs, (3) RMGIC + 1 wt.% BCNCs, and (4) RMGIC + 5 wt.% mesoporous ZnO NPs and 1 wt.% BCNCs. The fracture resistance test included these groups along with an intact teeth group (positive control) and a prepared but unrestored teeth group (negative control). A universal testing machine was used for all mechanical tests. RESULTS: The RMGIC + 1 wt.% BCNCs group exhibited the highest µSBS (6.35 ± 1.98 MPa), significantly surpassing the control and other experimental groups (p < 0.001). For fracture resistance, the negative control had the lowest value (422.70 ± 44.50 N, p < 0.05), while the positive control had the highest, significantly outperforming all groups except RMGIC + 1 wt.% BCNCs (p > 0.05). The RMGIC + 1 wt.% BCNCs group (1280.40 ± 340.87 N) demonstrated significantly greater fracture resistance than both RMGIC and RMGIC + 5 wt.% mesoporous ZnO (p < 0.05). CONCLUSIONS: Incorporating 1 wt.% BCNCs into RMGIC significantly enhanced both microshear bond strength and fracture resistance, leading to a higher proportion of restorable fractures. The positive correlation between bond strength and fracture resistance suggests that BCNCs-modified RMGIC is a promising restorative material for improving durability in primary molars.