Infiltration of natural enamel caries by capillarity: 2D real-time mapping in relation to prisms paths

Changes in enamel birefringence over time can be used to map infiltration of foreign liquids into carious enamel. The video shown was produced using orientation-indepedent polarizing microscopy with two liquid crystals variable retarders (so called dual polscope; Oldenbourg R. Polarization microscopy with the LC-PolScope. In: Goldman RD, Spector DL. eds. Live Cell Imaging: A Laboratory Manual. Cold Spring Harbor:Cold Spring Harbor Laboratory Press; 2005. 1-42)  using time intervals of 0.5 s. A dry natural enamel carious lesion was infiltrated with an aqueous Thoulet's solution with refractive index 1.40 and penetration coefficient of 3.200 cm/s (at 25 degrees Celsius) for 2.5 min. As the liquid penetrates, some parts present infiltration occurring both perpendicularly and parallel to the prism paths while others present infiltration only parallel to prism paths. This has implications in the penetration lengths, which, in turn, influences the time required for full infiltration to be completed. This technique could also be used to validate the most porous lesion area.