WSLs in Human Enamel Under Microcosm Biofilm: QLF/TMR characterization

Objectives: This study characterized artificial white spot lesions (WSLs) produced in human enamel under microcosm biofilm for different experimental periods. Fifty human enamel specimens (4X4 mm) were assigned to 5 distinct groups (n=10/group) differing according to the period of microcosm biofilm formation (2, 4, 6, 8 or 10 days).
Methods: Microcosm biofilm was produced on the specimens from a mixture of human saliva and McBain saliva at the first 8h. From this moment until the end of the experiment, the enamel samples were exposed to McBain saliva containing 0.2% sucrose. After the experimental periods, the WSLs formed were characterized by quantitative light-induced fluorescence (QLF) and transverse microradiography (TMR).Data were analyzed by (ANOVA/Tukey or Kruskal-Wallis/Dunn tests (p<0.05).
Results: Regarding QLF analysis, median (95% CI) changes in fluorescence (ΔF, %) were -7.04 (-7.74 – -6.45)^a, -8.52 (-8.75 – 8.00)^ab, -9.17 (-10.00 – -8.71)^bc, -9.58 (-10.53 – -8.99)^bc, -10.01 (-11.44 – -9.72)^c for WSLs formed during 2, 4, 6, 8 and 10 days, respectively. For the lesion area (mm²), the respective mean values (SD) were 0.04 (0.05)^a, 1.23 (0.20)^b, 1.40 (0.31)^b, 1.85 (0.38)^b, 2.26 (0.35)^b, respectively. As for TMR, mean lesion depths (SD, µm) were 53.7 (12.3)^a, 71.4 (12.0)^a, 103.8 (24.8)^b, 130.5 (27.2)^bc, 167.2 (39.3)^c, respectively, while the median (95% CI) integrated mineral losses (ΔZ, vol%.µm) were 1410 (1299–1479)^a, 2420 (2327–2604)^ab, 2775 (2573–2899)^bc, 3305 (3192–3406)^cd, 4330 (3972–4465)^d, respectively. A clear time-response pattern was observed for both analyses, but TMR, as expected, was able to better discriminate among the different lesions.
Conclusions: This is the first study to characterize artificial WSLs formed on human enamel under microcosm biofilm. Our data provide important information regarding the characteristics (extent of mineral loss and depth) of the lesions obtained employing different experimental periods. This information can be used in future studies aiming to test caries preventive products.