Applications of proanthocyanidin in dentistry

In dentistry, repair and restoration of tooth structure to regain its mechanical properties is the ultimate aim of caries management. Currently, preventive therapies are preferred to operative interference. New preventive approaches are necessary to treat dental caries. Dentine is composed of an organic matrix, consisting of type 1. Degradation of collagen matrix is the main reason for breakdown of resin-dentine bonds and development of secondary caries over time. Hence, preservation of collagen fibrils is essential for preventive and reparative procedures in minimum intervention dentistry. Proanthocyanidin (PA) is a natural collagen cross-linker, which can be obtained from grape seeds, pine bark or elm tree. It has a high affinity to proline-rich proteins, like collagen. Cross-linking of the collagen fibrils increases their mechanical properties and their resistance to breakdown by proteolytic enzymes. Thus, in the first part of the study, with the aim of discovering other possible natural dentine collagen cross-linkers, the effect of two smaller molecular size flavonoids, naringin and quercetin, on the mechanical properties of demineralized dentine was compared to PA. Demineralized dentine treated with PA showed the greatest increase in mechanical properties, followed by quercetin and naringin. The protease inhibitory effect of PA was evaluated by examining its actions on soluble and collagen-bound matrix metalloproteinases and cysteine cathepsins. Proanthocyanidin, even at low concentration of 1%, exhibited excellent inhibitory effects on soluble and matrix-bound proteases. Secondly, PA was incorporated in a dental adhesive to facilitate its application in clinical situations. The effect of PA incorporation on durability of resin-dentine bond was evaluated. Up to 2% of PA could be added to dental adhesive with no adverse effects on immediate resin-dentine bond strength. However, the bond strengths of PA-incorporated adhesives dropped significantly following ageing. This could be attributed to the free radical scavenging effect of PA, which might also have interfered with polymerization of dental adhesive. The mechanical properties of PA-incorporated adhesive were evaluated and it was shown that up to 1% PA could be incorporated into an adhesive resin. With the addition of higher concentration of PA, the mechanical properties of the adhesive resin were reduced with increased solubility. Proanthocyanidin release from the cured resin showed an initial burst for 48 hours and was stabilized after five days. Finally, the remineralization potential of PA on artificial root caries was also compared with quercetin and naringin. All three flavonoids showed remineralization potential; however, their effects were inferior to fluoride. Proanthocyanidin formed a precipitate band on the superficial layer of carious lesion, preventing further mineral deposition. Subsequently, PA was incorporated in a CPP-ACFP (casein phosphoproteins amorphous calcium fluorophosphates) containing-paste to increase the mineral uptake in subsurface layer of caries lesion. Simultaneous application of PA and CPP-ACFP was shown to have a favourable outcome on mineral deposition in root caries lesion.published_or_final_versionDentistryDoctoralDoctor of Philosoph