Discussion
dentine erosion, erosion, dentine, dentine pellicle, caries
DEMINERALIZATION, EROSION, CAVITY, CARIES
Health benefits from polyphenol-rich plants include protection in the oral cavity, since the polyphenols can interact with salivary proteins from the pellicle, and they can protect against caries [Regarding the first mechanism of action (interacting with dentine pellicle), one must focus on the molecular structure of the polyphenols. They have a basic chemical structure of phenol rings and galloyl esters or hydroxyl groups. These moieties can form complexes with salivary proteins, especially proline-rich proteins (PRP) [Previous studies have already shown the positive effects of green tea against erosion [Regarding the grape seed extract, it mainly contains purified oligomeric proanthocyanidin (OPC). This polyphenol has catechin and epicatechin units with partial galloylation [Regarding the second and third mechanisms of action (interacting with the collagen layer and inhibiting the MMPs), one must understand the erosion process on dentine. This process is particularly affected by the organic matrix, in other words, the collagen layer in dentine. With acid attacks, the dentine surface demineralizes, causing an initial loss of its mineral component. With increasing attacks, the demineralized layer exposes the organic component of the dentine. The amount of exposed collagen layer increases as the erosion process progresses, but when this layer reaches a certain thickness, it acts as barrier against further acid attacks, and the demineralization rate decreases. However, this layer can be degraded by MMPs present in saliva or in the dentine itself. If the collagen layer is degraded by the MMPs, the mineral part of the dentine will be further exposed to the acids and the demineralization will progress. So, if the collagen layer is cross-linked and preserved, and if the MMPs are also inhibited from degrading the collagen, this organic layer will remain on the surface of the dentine for longer, protecting it against further demineralization.The EGCG from green tea has the galloyl moiety, and this can change the conformation of the MMPs, thus inhibiting the proteases and hindering their effect on the collagen [Likewise, the grape seed extract can also protect the dentine against surface loss by its effect on the collagen and the MMPs. The OPC can bind to the organic layer in the dentine, they are also known natural cross-linking agents that easily bind to the collagen fibers [When observing the two subgroups of our study (solutions with and without fluoride), we observed generally a significant better protection in the solutions where fluoride was present. The protection of fluoride against erosion is rather believed to be related to the formation of CaF2-like particles on the tooth surface, which serve as a physical barrier against the acid challenges [We therefore conclude that the plant extracts showed a protective effect against dentine erosion, regardless of the presence of salivary pellicle, and that the fluoride seems to improve their protection. Future studies should test this combination of plant extracts and fluoride using in situ models. Besides, these compounds could be formulated using a composition more closely to a commercial mouthrinse or even as active ingredients in toothpastes. Furthermore, the impact of brushing challenges would also be of interest. Finally, proteomics studies could be conducted to gain further insight into the exact mechanism of the protection provided through the treatment with these compounds.