Shear Bond Strength and Remineralisation Effect of a Casein Phosphopeptide-Amorphous Calcium Phosphate-Modified Glass Ionomer Cement on Artificial "Caries-Affected" Dentine

This study investigated the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP)-modified glass ionomer cement (GIC) on shear bond strength (SBS) and remineralisation of artificial caries-affected dentine. Human dentine slices were demineralised and allocated to three groups: group 1, conventional GIC; group 2, CPP-ACP-modified GIC; and group 3, resin-modified GIC. The SBS was measured using a universal testing machine (n = 16 per group). Remaining samples (n = 8 per group) were subjected to pH-cycling for 28 days. After pH-cycling, lesion depth and micro-mechanical properties at the sample-bonding interface were investigated using micro-computed tomography (micro-CT) and nano-indentation, respectively. The SBS for groups 1 to 3 were 4.6 +/- 1.5 MPa, 4.2 +/- 1.1 MPa, and 5.9 +/- 1.9 MPa, respectively (p = 0.007; group 1, group 2 < group 3). Lesion depths determined by micro-CT for groups 1 to 3 were 186 +/- 8 mu m, 149 +/- 14 mu m, and 178 +/- 8 mu m, respectively (p < 0.001; group 2 < group 1, group 3). The mean (+/- SD, standard deviation) nano-hardness values for groups 1 to 3 were 0.85 +/- 0.22 GPa, 1.14 +/- 0.21 GPa, and 0.81 +/- 0.09 GPa, respectively (p = 0.003; group 1, group 3 < group 2). The mean (+/- SD) elastic moduli for groups 1 to 3 were 1.70 +/- 0.33 GPa, 2.35 +/- 0.44 GPa, and 1.59 +/- 0.13 GPa, respectively (p < 0.001; group 1, group 3 < group 2). The results suggest that the incorporation of CPP-ACP into GIC does not adversely affect the adhesion to artificial caries-affected dentine. Furthermore, CPP-ACP-modified GIC is superior to conventional GIC in promoting dentine remineralisation.