Relative fluoride response of caries lesions created in fluorotic and sound teeth studied underremineralizing conditions

Abstract

Fluoride prevents caries by decreasing demineralization and promoting remineralization of enamel crystals during lesion formation and progression. The chemical, morphological, and histologic characteristics of teeth with fluorosis may alter the response of enamel to fluoride during the caries process. However, the effectiveness of fluoride in fluorosed teeth has not been thoroughly studied. Therefore, the current study utilized an in-vitro net remineralization model to study differences between fluorosed and sound enamel with regards to caries lesion remineralization and progression. Hypotheses: There is no significant difference in the effectiveness of fluoride to enhance caries lesion remineralization between fluorosed and non-fluorosed (sound) teeth after changes in enamel fluorescence relative to the lesion baseline. Objectives: The primary objective is to investigate the relative fluoride response of caries lesions created in sound and fluorosed teeth of varying severities under remineralizing conditions in vitro. Secondary objectives: a) To investigate the impact of the presence and severity of enamel fluorosis on caries lesion formation, and b) To investigate the acquired acid resistance of pH-cycled lesions relative to their fluorosis severity. Materials and Methods: Three hundred sixty (360) extracted human molars (sound and fluorosed) were collected and divided into four main groups based on their TF score (0; 1; 2; 3), with sample size of n = 45 per group. Each group was divided into two subgroups: no fluoride/placebo and fluoride/treatment. Artificial caries lesions were created on the teeth and pH-cycled for 20 days using a net remineralization model. The lesions were assessed to determine differences in acquired acid resistance. Quantitative light-induced fluorescence (QLF) was used throughout the study to determine changes in enamel fluorescence relative to a sound enamel window, thereby providing information about enamel de- or remineralization. The results of this study demonstrated that enamel fluorosis levels had a significant effect on lesion remineralization after pH cycling (p > 0.05). The teeth with moderate dental fluorosis had a significantly better response to remineralization and more resistance to a subsequent acid challenge than sound teeth in the presence of fluoride.