Natural enamel caries in quinoline: Volumetric data and the pattern of infiltration.

This study aimed to test the hypotheses that (i) a parameter related to permeability, αd (ratio of squared water volume by the nonmineral volume) is, among all major component volumes (mineral, water, and organic volumes) the best predictor of quinoline infiltration in natural enamel caries (NEC), and (ii) the pore volume fraction infiltrated by quinoline (Vqui ) in NEC is much lower than previous estimates that neglected water and organic enamel volumes. Mineral and nonmineral volumes and αd were measured at 341 histological points (from 20 approximal NEC lesions), and transport of quinoline was tracked by orientation-independent polarizing microscopy. R2 values of Vqui were 0.596 (αd ), 0.033 (mineral volume), 0.474 (water volume), and 0.011 (organic volume). Vqui values were 23% (body of the lesion), 7% (dark zone), and 9% (translucent zone), lower than previous estimates (with high effect size). Transport of quinoline occurred both parallelly and perpendicularly to prism paths, and dark zones were seen where only transport parallel to prisms occurred. In conclusion, αd was the main predictor of quinoline infiltration, but it differed from the water volume with a small effect size, and the pore volume fraction with quinoline was much lower than previous estimates.

Predicting infiltration of the surface layer of natural enamel caries.

AIM: To test the hypothesis that the water volume more easily available for diffusion (αd) is the best predictor among all major components of the proportion of pore volume infiltrated by a liquid in the surface layer of dry natural enamel caries (NEC). MATERIALS AND METHOD: Two aqueous solutions of mercuric and potassium iodide (Thoulet's solutions) with different refractive indexes (1.4 and 1.47) and penetration coefficients (3212 cm/s and 2297 cm/s) were tested at histological points (n = 63) of ground sections of NEC lesions. Component volumes were measured with microradiography and interpretation of birefringence. Real-time 2D mapping of capillary flow was performed with orientation-independent polarizing microscopy. RESULTS: αd was a good predictor for both liquids (T1.40: R(2) = 0.413; T1.47: R(2) = 0.505), but was similar to the water and air volumes for Thoulet's 1.47, and to the mineral and organic volumes for Thoulet's 1.40. From real-time 2D mapping, infiltration in ground sections occurred in two propagation directions, perpendicularly to the prism paths (at the centre of the lesion bodies) and axially to the prism paths (at all parts of the lesions), with two penetration rates, the faster related to prisms sheaths and the slower related to intraprismatic pores, affecting penetration length and air displacement. CONCLUSIONS: αd was a good predictor for both liquids, but was similar to the water and air volumes for T1.47 and to the mineral and organic volumes for T1.40. Both flow mechanics and component volumes are required to interpret infiltration of liquids into NEC.