Remineralization of dentin collagen by meta-stabilized amorphous calcium phosphate

Biomineralization of collagenous mineralized tissues (CMT), in vivo, stands as a precisely cell-controlled process. An organic insoluble collagenous matrix forms, then inorganic mineral is deposited on the matrix. The exact mechanism of action remains elusive and most researchers agree the amorphous mineral phase is crucial in CMT's development. Artificial demineralized dentin can be remineralized via amorphous calcium phosphate (ACP) precursor stage stabilized by 500 μg ml−1 polyacrylic acid (PAA). This remineralization is a step-by-step progression. ACP initially forms in the collagen matrix at its base, transforms into hydroxyapatite, and migrates towards the surface. The state of ACP, which is labile in liquid environments, can be controlled by PAA in a dose-dependent manner. Thus, the concentration of PAA is a key parameter influencing dentin remineralization. Low concentration of PAA (100 μg ml−1) fails to maintain liquidity of ACP, resulting in superficial remineralization. Conversely, high concentration of PAA (1000 μg ml−1) retards phase transformation of ACP and, thereby, inhibits remineralization. The purpose of this study is to demonstrate the balance between meta-stability and crystallization of ACP precursor phase. Our findings also provide evidence for the role of ACP during biomineralization and reveal a possible approach to repair CMT.