The effect of dehydration on quantitative light-induced fluorescence analysis of early enamel demineralization

The purpose of this study was to determine the effect of hydration [distilled water (DH2O) and saliva] on lesions of varying severity and determine an optimal drying method to obtain reliable quantitative light-induced fluorescence (QLF) readings. Ten previously extracted molars were placed into a demineralizing solution for 7, 14 and 21 days. Between each demineralizing cycle the teeth were removed. To test for in vitro reliability the teeth were rinsed in DH2O for 1 min and then QLF images were taken every 10 s (control cycle with no drying employed - bench drying only). This was repeated following (i). compressed air drying for 30 s or 15 s and (ii). 30 s cotton wool roll application (CWR). To test for in vivo reliability the experiment was repeated using whole human saliva in place of DH2O. Control groups demonstrated the effect of hydration on QLF reliability; at 7 days reliable results were obtained after 370.4 s (DH2O) and 432.3 s (saliva). Air drying of both DH2O and saliva-rinsed teeth reduced reliability time to 2.1 (+/-6.0) and 3.2 s (+/-7.6), respectively. Cotton wool roll application produced reliable results in 89 s with DH2O and 110 s with saliva. As lesion severity increased [14 days mean deltaQ 115 (+/-90.2), 21 days mean deltaQ 168.0 (+/-120.7)] time to reach reliability significantly increased under control drying and CWR (P > 0.05). Time taken for compressed air-dried teeth to produce reliable results was not significantly different across the groups. Compressed air-drying for 15 s produces reliable results with both DH2O and saliva-hydrated lesions. Future in vivo experiments will be required to determine if the air-drying can be reduced further in a clinical situation.