In vitro Study of the Role of Human Neutrophil Enzymes on Root Caries Progression

Abstract

The role of the host immune system in caries progression is mainly speculative, and it is believed that it entails the enzymatic degradation of the dentin organic matrix. The aim of this study was to evaluate the proteolytic effect of human neutrophil enzymes on root caries progression. For this, specimens of bovine root dentin were divided into 4 groups (<i>n</i> = 30): caries (C), caries + neutrophils (C + N), no caries (Control), and no caries + neutrophils (Control + N). <i>Streptococcus mutans</i> biofilm (10<sup>5</sup> CFU/mL) was grown on the root surface to artificially induce root carious lesions (C and C + N groups). Specimens were then exposed to neutrophils (5 × 10<sup>6</sup> cells/mL) for 48 h (C + N and Control + N groups). Caries development and neutrophil exposures were repeated a 2nd and 3rd time. Caries depth (CD) and dentin demineralization (DD) were assessed by infiltration of rhodamine B using fluorescence microscopy. Collagen fibril ultrastructure was characterized under a polarized microscope with Picrosirius red staining. There were no significant differences (<i>p</i> > 0.05) in CD and DD between the C and C + N groups for 1, 2, and 3 caries-neutrophil exposures. Immature collagen was significantly less present in the carious groups (C, <i>p</i> = 0.003; C + N, <i>p</i> = 0.01) than in the noncarious groups in the most superficial 200 µm. We thus concluded that human neutrophil enzymes did not influence short-term root caries progression, and immature collagen fibrils were more susceptible to degradation during <i>S. mutans</i>-induced root caries progression.

In Vitro Models Used in the Formation of Root Caries Lesions—A Review of the Literature

“…Consequently, microbiological models have been created which utilise bacteria cultured on root dentine and are known to be important in the caries process in vivo. Cariogenic mono-species biofilms were found to be the most common microbiological models in this review [10,19,21,24,25,30,[32][33][34]50,56]. Bacteria, such as Streptococcus mutans (S. mutans), Lactobacilli, and Actinomyces species, that are acidogenic and aciduric are inoculated for growth on tooth surfaces and are important in the aetiology of root caries lesions [72,73].…”

“…The benefits of using human teeth are that they provide findings more translatable to clinical practice, since the substrate used is the human root, which reflects the clinical situation. Bovine roots were the second common substrates used in the reviewed articles [2,10,[42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58]. Bovine dentine has been a valuable substrate used in research methodologies for the prevention or treatment of dentinal carious lesions [58].…”

“…Notably, there is a concern that antimicrobial solutions can have adverse effects on the mineral content and compositional structure of dentine [62]. The most common method used to prevent bacterial contamination in extracted teeth was to store them in a thymol solution [4,23,30,[33][34][35][36][37][38][39]54,56]. Thymol causes the perforation of cell membranes, resulting in bacterial cell death [63].…”