Indirect versus direct pulp capping: reactionary versus reparative dentin

They colonize and enlarge the dentino-enamel junction, widening the gap between the carious enamel and the soft carious dentin. Debris such as cell walls remnants remaining after by vegetal chewing, and fibers issued from muscle-like ‘meat’ may also be present. The soft carious dentin located beneath this zone of food debris is a mixture of bacteria and demineralized dentin that may be removed without drilling, using only manually sharp excavators. At the surface of this layer, the carious dentin is fully demineralized. The soft carious dentin displays enlarged tubules, containing bacteria acting within these reservoirs. This layer is totally deprived of peritubular dentin. From the surface to the depth of the lesion, the dentin progressively is less demineralized. Apatitic crystals provide some consistency to this layer. Gradually peritubular dentin reappears. The next carious layer includes a mixture of infected tubules filled by cariogenic bacteria and bacteria-free tubules. A continuous ring of peritubular dentin surrounds the lumens of the canaliculi. Intertubular dentin gradually reach the original structure. Demineralization and reprecipitation occurs at the surface of apatitic crystals, increasing their size in three directions. In the sound dentin, crystals display the following main dimensions: 34Å thick, 139Å wide and 250Å long. In the carious dentin, the crystals increase in thickness, and enlarge. Measurements indicate a 90Å (65-70Å) thickness x 300Å in width, and a length of x 500Å. Crystals reach a final diameter of 120-135Å according to Takuma et al.1