Method: 195 ground/polished 3x3x2mm sound human-enamel-specimens were divided into three groups and demineralized using a multispecies microbial caries-model [Actinomyces naeslundii, Lactobacillus casei, Streptococcus mutans, Streptococcus salivarius and Streptococcus sanguinis] for 3, 6, or 9 days. Specimens were then remineralized with 1,100 ppm-F as NaF solution for 10 days using a pH-cyclic-model. Measurements for sound, demineralized and remineralized enamel were obtained by microfocus computed tomography [µ-CT: mineral volume (µm3)], reflection, roughness, and QLF. The surface was hydrated and fluorescence images were acquired at 1-second intervals for 10s. During image acquisition, specimens were dehydrated with continuous compressed air. Changes in ΔQ per second (ΔQD: %×mm2/sec) at 5 and 10s were obtained.
Result: Reflectance decreased from sound to demineralization for all groups (p<0.0001); remineralization groups were higher than demineralization (p<0.001), but not different from sound (p>0.32). Ra increased from sound to demineralization for all groups (p<0.0001) and remineralization groups were also higher than sound (p<0.0001). DQ10 increased from sound to demineralization for all groups (p<0.0001), and remineralization decreased compared to demineralization (p<0.02), but was higher than sound (p<0.0001). Similarly DQD at both 5 and 10 seconds increased from sound to demineralization for all groups (p<0.0001), and remineralization decreased compared to demineralization (p<0.05), but was higher than sound group (p<0.0001). The correlations between mineral volume (µ-CT) and others (reflectance, roughness, DQ10 and DQD) were -0.63, 0.71, 0.82, and 0.82, respectively (p<0.0001).
Conclusion: Reflection, roughness and QLF could distinguish between sound and demineralized enamel. Reflection and QLF were able to distinguish between demineralized and remineralized enamel. Supported by NIH/NIDCR R21 DE018390-01A2.