Abstract
Purpose: To develop a new toothpaste for preventing root caries, we examined several ingredients based on root caries progression, and found that pyrrolidone carboxylic acid (PCA) can inhibit the development and progression of dentin demineralization. The purpose of this study was to estimate the efficacy of the new toothpaste containing PCA and fluoride (F) to prevent root caries by evaluating its inhibitory effects on dentin demineralization and collagen degradation in vitro. We also investigated the mechanism of the inhibitory effect of PCA on demineralization and collagen degradation.
Methods:
1. Toothpaste efficacy; Sound and collagen-exposed dentin blocks were obtained from bovine roots. Sound dentin blocks were treated with diluted toothpastes (1,450 ppm F [TP-1450F], 3,000 ppm F [TP-3000F] or 1,450 ppm F+PCA [TP-1450F+PCA]) and were immersed in artificial saliva. Collagen-exposed dentin blocks were treated with diluted toothpastes and immersed in artificial saliva containing collagenase. The blocks were then immersed in demineralized solution. The amount of released Ca ions was determined by atomic absorption spectroscopy. Furthermore, the amount of hydroxyproline (HYP) in the surface of collagen-exposed dentin blocks was determined by confocal Raman microscopy.
2. Mechanism of action; Sound and collagen-exposed dentin blocks were treated with diluted 1,450 ppm F (S-1450F) and 1,450 ppm F+PCA (S-1450F+PCA) solutions, respectively. F uptake to the blocks was measured using ion electrodes. Collagen and collagenase were incubated with PCA, and the amount of collagen degradation was determined. Moreover, the amount of PCA adhered to collagen and hydroxyapatite (HAP) before and after washing was examined, and the amount of PCA residues was calculated.
Results: 1. In the TP-1450F+PCA group, the amount of released Ca ions was significantly smaller than that in the TP-1450F group of both sound and collagen-exposed dentin blocks. The amount of HYP in the TP-1450F+PCA group was significantly larger than that in the TP-1450F and TP-3000F groups. 2. F uptake was larger in the S-1450F+PCA group than that in the S-1450F group of both sound and collagen-exposed dentin blocks. PCA inhibited collagen degradation by collagenase and the amount of PCA residues on collagen was larger than that on HAP.
Conclusions: TP-1450F+PCA significantly inhibited demineralization of both sound and collagen-exposed dentin blocks compared with TP-1450F in vitro. TP-1450F+PCA inhibited collagen degradation compared with TP-1450F and TP-3000F. The effects of PCA on F uptake to dentin, collagen degradation by collagenase and adherence to collagen may contribute to the efficacy of TP-1450F+PCA.
