A- and B-Type Proanthocyanidins Enhance Mineral-Mechanical Recovery of Root Caries

Objectives: Proanthocyanidins were found to assist in dentin bioremineralization. This study investigated the effect of inter-flavan linkages (IFL) and degrees of polymerization (DP) on in vitro root caries remineralization using PAC-DESIGNERs biomodulation.
Methods: Standard formulations of A and B-type Dimer and Trimer PACs were obtained by depletion and enrichment of select ingredients generating normalized extract resources (DESIGNER) approach, resulting in experimental four PAC-DESIGNERs. Root caries lesions were induced by chemical demineralization (pH 4.6, 96 hr, 37°C) to obtain 100-µm lesion in human molars. The biomodulation process consisted of 1-time 1% (w/v) PAC-DESIGNERS treatment for 1 hour. Demineralized dentin and Tris buffer were used as negative and positive controls, respectively. A Tris buffer with Ca/P ratio=2.1 was used as a remineralization solution for 14 days at 37°C. Nano-mechanical dynamic properties (complex modulus - E* and damping capacity - Tan δ) (n=5) were determined using tribo-indentation (Ti980 Hysitron/Bruker) at different lesion depths (40 to 100 µm). The mineral density (n=8) (mgHA/cm³) was assessed using a micro-CT 50 (Scanco Medical) and expressed as mineral recovery percentage. Data were statistically analyzed using ANOVA and post-hoc tests (α=0.05).
Results: PAC-treated groups presented higher E* at all different depths (p<0.05), where A-type PACs resulted in the highest increase in the complex modulus of dentin (p<0.05). The damping capacity of dentin decreased for all PAC-treated groups. (p<0.05). Dimers (A- and B-type) induced the highest dentin mineral recovery percentage (p<0.05).
Conclusions: IFL and DP have a modulatory role in the remineralization potential of PACs. Dimeric A-type PACs seem to induce higher remineralization outcomes. This remineralization ability of investigated PAC-DESIGNERs is believed to be driven by controlling the rates of intra- and extra-fibrillar mineralization.