Teeth With Mild and Moderate Enamel Fluorosis Demonstrate Increased Caries Susceptibility In Vitro

Abstract

Subjects In this laboratory study, 49 human unerupted third molars extracted for clinical reasons and classified as scores 0-4 using the Thylstrup and Fejerskov (TF) index (n = 9 for TF0, n = 10 for TF1, n = 10 for TF2, n = 10 for TF3, and n = 10 for TF4) were included. TF1-TF4 teeth were collected in Colombia, and TF0 teeth were obtained from the University of Copenhagen. Ethical approval was obtained. Key Risk/Study Factor Teeth in the study were subjected to pH cycling to induce caries lesions.

Main Outcome Measure The primary outcome measure was resistance to a cariogenic challenge determined using cross-sectional microhardness. A series of indentations, starting at 10 μm below the anatomic surface down to 200 μm, were placed in the teeth using a Knoop indenter. These measurements were performed before and after pH cycling, yielding baseline and demineralization areas, both calculated “by numerical integration of the hardness vs depth values using the trapezoidal rule.” The demineralization data were then normalized for differences at baseline and a “percentage reduction” was calculated, with higher numbers being indicative of greater susceptibility to caries lesion formation.

Main Results Teeth with scores of TF3 and TF4 exhibited greater susceptibility to caries lesion formation than all other teeth, with no differences being observed between unaffected teeth (TF0) and teeth with scores of TF1 and TF2. Teeth with scores of TF3 and TF4 also displayed a lower mean baseline area than those with TF1 and TF2, although not compared to TF0 teeth, indicative of greater hypomineralization.

Conclusions The authors concluded that the results of their study suggest that teeth with moderate fluorosis had an increased caries susceptibility when compared to teeth with very mild or no fluorosis. They hypothesized that these differences in caries susceptibility are mainly due to dissimilarities in porosity of the enamel—in fluorotic teeth, a greater subsurface mineral area is exposed to demineralization, and deeper acid diffusion through enamel is facilitated.