Operative dentistry: Caries of dentin

Dentin structure:
?The characteristic feature of dentin structure is the dentinal tubules. The dentinal tubules have a hollow structure and they are responsible for dentin permeability. The number and size of dentinal tubules is different at different locations on the dentin. Their course is S-shaped between the junction of dentin and enamel (DEJ) and the pulp, in the crown, and between the junction of dentin and cementum (CDJ) and the pulp, in the root.
?The peritubular (sometimes referred to as intra-tubular) dentine is a highly mineralised structure of dentine which has a thickness of approximately 0.5-0.8?m. It is more highly mineralized than intertubular dentine and it contains no organic collagenous fibres in comparison with the intertubular dentine which surrounds it.
?The dentinal is a hydrated nano-composite of hydroxyapatite crystallites with diameter of approximately 5 nm in diameter and they are distributed in a scaffold of type-I collagen fibrils, which are around 50-100 nm in diameter, and the remaining parts are fluids and non-collagenous proteins. The hydroxyapatite crystals differ in enamel and dentin, being larger and more regular in enamel than dentin.
Dentin morphology & histology:
?Unlike enamel, dentin formation continues after tooth eruption and throughout the life of the pulp. The dentin forming the initial shape of the tooth is called primary dentin and is usually completed 3 years after tooth eruption (for permanent teeth).
?Dentin is located between the enamel or cementum of the external tooth and the pulp internally.
?Most of the volume of the tooth is dentin.
?The dentin and the pulp are morphologically and embryologically a single unit.
?It is a hydrated, porous tissue containing dentinal tubules, resulting from the deposition of a collagenous matrix around the cytoplasmic processes of odontoblasts (Tomes fiber), which subsequently mineralises, encasing the odontoblast processes within the tissue.
?The dentinal tubule allows fluid movement and ion transport necessary for remineralization of intertubular dentin, apposition of peritubular dentin, and/or perception of pain.