Identification of esters in carious dentine Staining and chemo-mechanical excavation

Abstract

Dental caries is clinically seen as a yellowish-brown discoloration that can be explained by the reactions between proteins and sugars resulting in Maillard products. However, the discoloration of carious dentine is an imprecise indicator of whether or not the dentine is caries free. Other processes might act in concert with the Maillard reactions. This thesis describes how special functional groups formed in the carious process can be used in connection with dyes that selectively stain the carious tissue in order to avoid over excavation. The initial study aimed to analyse unique functional groups in sound and carious dentine and their presumed reaction with hydrazine derivative using Fourier Transform Infrared Spectroscopy (FTIR) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The second and third studies focused on the possible formation of covalent bonds between carious dentine and 15N2-hydrazine, 15N2-labelled Lucifer yellow, and stains carrying a hydrazine derivative respectively, using ToF-SIMS, solid-state NMR spectroscopy (13C and 15N) and light-microscopic observations. The latter aimed to evaluate the type of binding, electrostatic or covalent, to carious dentine. In a systematic review with an adjacent meta-analysis, the ability of a chemically based product in clinical caries excavation was evaluated by comparing the efficacy of chemo-mechanical excavation with that of traditional rotating instruments. The results revealed ester groups unique to the carious dentine, with a higher occurrence in the inner layer of carious dentine, which, after reaction with hydrazine derivative, form covalent bonds not seen in sound dentine. This is a selective binding in comparison with dyes with only an electrostatic binding capacity. The systematic review found that the chemo-mechanical excavation technique is as efficient as burs, albeit with a longer treatment time but with enhanced patient comfort. It is concluded that ester functional groups unique to carious dentine can be specifically stained with dyes carrying a hydrazine group, thereby acting selectively in distinguishing between sound and carious dentine. As a result, using a more precise indicator will support the identification of the end-point during clinical caries excavation.