Comparative evaluation of shear bond strength of nano-hydroxyapatite incorporated glass ionomer cement and conventional glass ionomer cement on dense synthetic hydroxyapatite disk: An in vitro study.

Aim: The aim was to evaluate and compare the shear bond strength of nano-hydroxyapatite (Nano-HAp) incorporated and conventional glass ionomer cement (GIC).

Materials And Methods: Nano-HAp GIC was prepared by replacing 8 wt% of GIC powder with nano-HAp powder. Twenty-six HAp disks were used as substrate for bonding and divided into two equal groups. Before bonding the HAp disk was prepared by silicon carbide (no. 2500) followed by 10% polyacrylic acid conditioning. The standardized samples were prepared using split teflon mold on customized bonding jig so as to adhere testing materials to pretreated HAp disk. These samples were stored in distilled water for 24 h at 37°C before bond strength testing.

Results: The descriptive statistical analysis and independent samples t-test were used. The nano-HAp incorporated and conventional GIC had the mean shear bond strength of 3.28 ± 0.89 MPa and 5.25 ± 0.88 MPa, respectively. Nano-HAp incorporated GIC had lower shear bond strength with very high level of significance (P < 0.001). The nano-HAp incorporated GIC showed mainly mixed type of failure whereas conventional GIC showed mainly a cohesive failure.

Conclusion: The lower shear bond strength of nano-HAp incorporate GIC revealed that the addition of nano-HAp interfered with the bonding ability of GIC to the substrate interface, but the mixed type of failure in nano-HAp incorporated GIC suggests that it increases the strength of the matrix. However, the role of nano-size particles on the micro-size particles of GIC for the bonding mechanism and the ratio and proportions of nano-HAp to the GIC needs further elucidation.