Shear-bond-strength And Remineralisation-effect Of CPPACP-modified Glass-ionomer To Artificial Caries-affected Dentine

Objectives: To investigate the effect of casein phosphopeptide-amorphous calcium phosphate (CPPACP) modified glass-ionomer cement (GIC) on shear bond strength (SBS) and remineralisation to artificial caries-affected dentine. Methods: Human dentine slices were demineralised to mimic caries-affected dentine. They were then randomly allocated to three restoration groups (n=16 per group): group-1, conventional GIC; group-2, CPPACP modified GIC; and group-3, resin modified GIC. The SBS of the samples was measured using a universal testing machine (n=8 per group). The failure modes of the fractured samples were analyzed by scanning electronic microscopy (SEM). The remaining samples (n=8 per group) were subjected to pH cycling for 28 days. After pH cycling, lesion depth and micro-mechanical properties of the samples were investigated by micro-computed tomography (micro-CT) and nano-indentation, respectively. Results: The SBS for group-1, group-2 and group-3 were 4.5±1.6 MPa, 4.3±1.2 MPa and 6.6±1.7 MPa, respectively (p=0.01; group-1, group-2 < group-3). The results of failure modes of the 3 groups were summarized in Table 1. Representative modes of failure under SEM were shown in Figure 1. Micro-CT determined lesion depths for group-1, group-2 and group-3 were 186±8 µm, 149±14 µm and 178±8 µm, respectively (p<0.001; group-2< group-1, group-3). The mean nano-hardness values for group-1, group-2 and group-3 were 0.17±0.04 GPa, 0.25±0.06 GPa and 0.14±0.05 GPa, respectively (p<0.001; group-1, group-3< group-2). The mean elastic moduli for group-1, group-2 and group-3 were 6.02±0.59 GPa, 7.27±0.86 GPa and 5.70±1.14 GPa, respectively (p=0.005; group-1, group-3< group-2). The load-displacement curve of the 3 restoration groups was shown in Figure 2. Conclusions: The results indicate that the incorporation of CPPACP into GIC would not adversely affect the adhesion to artificial caries-affected dentine. Furthermore, it is superior to conventional GIC in promoting remineralisation on artificial caries-affected dentine and hence can be a better restorative material than conventional GIC for restoration