The validation of Quantitative light-induced fluorescence to quantify acid erosion of human enamel

Objective: The purpose of this study was to validate the Quantitative light-induced fluorescence (QLF) device against transverse microradiography (TMR) with regard to the quantification of enamel erosion in vitro. Design: Longitudinal in vitro. Methods: Thirty previously extracted, caries free, human premolars were selected and prepared by gentle pumicing and coating in an acid-resistant nail-varnish save for an exposed window on the buccal surface. QLF baseline images were taken and the teeth then exposed to an erosive solution, 0.1% citric acid (pH 2.74). Teeth were removed at 30 min intervals, air-dried and QLF images taken. At this time one tooth was randomly selected, removed from solution and sectioned through the lesion at three sites. The polished sample (100 μm) was subjected to TMR and analysed for erosive mineral loss using proprietary software, with the ΔZ values noted. QLF images were analysed by a blinded examiner with ΔF and ΔQ values recorded. Data were entered into SPSS and the correlation between the ΔZ and ΔF, and ΔZ and ΔQ values calculated. Results: A wide range of erosive lesions was produced, with a steady increase in both ΔZ and ΔF over time; ΔZ (24.0 (S.D. 1.2)–6114.3 (S.D. 1177.57)); ΔF (1.8–11.2), ΔQ (2.5–202.6). The results were scatter plotted and a regression line calculated. A positive correlation between ΔZ and ΔF of 0.91 was found, and for ΔZ and ΔQ; 0.87. Conclusions: The ability for QLF to detect and longitudinally monitor in vitro erosion has been shown. The strong positive correlation of ΔF with ΔZ suggests that percentage fluorescence loss as measured by QLF could be of great value in the development of a non-destructive, longitudinal tool for use in vitro, in situ and possibly in vivo.