The use of sodium trimetaphosphate as a biomimetic analog of matrix phosphoproteins for remineralization of artificial caries-like dentin

Objectives: This study examined the use of sodium trimetaphosphate (STMP) as a biomimetic analog of matrix phosphoproteins for remineralization of artificial carious-affected dentin. Methods: Artificial carious lesions with lesion depths of 300 ± 30 μm were created by pH-cycling. 2.5% hydrolyzed STMP was applied to the artificial carious lesions to phosphorylate the partially-demineralized collagen matrix. Half of the STMP-treated specimens were bonded with One-Step. The adhesive and non-adhesive infiltrated specimens were remineralized in a Portland cement-simulated body fluid system containing polyacrylic acid (PAA) to stabilize amorphous calcium phosphate as nanoprecursors. Micro-computed tomography (micro-CT) and transmission electron microscopy (TEM) were used to evaluate the results of remineralization after a 4-month period. Results: In absence of PAA and STMP as biomimetic analogs (control groups), there was no remineralization irrespective of whether the lesions were infiltrated with adhesive. For the STMP-treated experimental groups immersed in PAA-containing simulated body fluid, specimens without adhesive infiltration were more heavily remineralized than those infiltrated with adhesive. Statistical analysis of the 4-month micro-CT data revealed significant differences in the lesion depth, relative mineral content along the lesion surface and changes in ΔZ between the non-adhesive and adhesive experimental groups (p < 0.05 for all the three parameters). TEM examination indicated that collagen degradation occurred in both the non-adhesive and adhesive control and experimental groups after 4 months of remineralization. Significance: Biomimetic remineralization using STMP is a promising method to remineralize artificial carious lesions particularly in areas devoid of seed crystallites. Future studies should consider the incorporation of MMP-inhibitors within the partially-demineralized collagen matrix to prevent collagen degradation during remineralization.