This document summarizes the different types of dentin found in teeth: 1) Peritubular dentin surrounds dentinal tubules and is highly mineralized, while intertubular dentin is less mineralized and contains collagen fibers. 2) Intratubular dentin fills dentinal tubules and reduces permeability as people age or during caries. 3) Primary dentin is characterized by S-shaped tubules and daily growth lines. Mantle dentin is near the enamel and circumpulpal dentin forms the bulk. 4) Secondary dentin is less mineralized and forms slowly throughout life surrounding the pulp. Tertiary dentin responds to injury by sealing off areas.

1. DENTIN
Peritubular Dentin:
- Surrounds dentinal tubules and highly mineralized
- Not found near pulpal areas
Intertubular Dentin:
- Body of dentin
- Less mineralized than peritubular dentin
- Matrix of collagen fibres and hydroxyapatite
Intratubular Dentin:
- Sclerotic dentin that fills up the dentinal tubules
o Reduce permeability of dentinal tubules
o Generally observed in elderly people and slowly progression caries
o Prolong pulp vitality
- Dentinal tubules contains odontoblastic processes
o Cytoplasmic extensions of odontoblasts
o The process tapers towards DEJ, dentinal tubules as well
o The process contains protein-synthesizing organelles
Primary Dentin (Mantle and Circumpulpal)
- Characterized by S shape dentinal tubules
- Incremental lines can be seen
o A.k.a Von Ebner Lines
o Due to daily rhythmic deposition of dentin
o Neonatal line – separate prenatal and postnatal dentin
o Right angle to dentinal tubules
Mantle dentin (Primary)
- Found near DEJ
- First dentine layer formed during crown and root formation
- Interdigitated with enamel at DEJ and globular dentine (before circumpulpal)
Circumpulpal dentin (Primary)
- Bulk of dentin
- Formed before root completion
- More mineral than mantle dentin
Predentin
- Unmineralised, newly formed dentine by odontoblastic cells
- Found at Dentine-Pulp Junction

2. Secondary Dentin (Regular and Irregular)
- Formed after root completion
- Seen as narrow band surrounding the pulp (roof and floor of pulp)
- Forms slowly, throughout the life of the tooth
Tertiary Dentin (Reparative dentin)
- In response to pulpal stimulation (injury/trauma/caries)
- Localised
- It helps seal off the area of injury causing resolution of inflammation & removal of dead
cells.
Tomes’ Granular Layer
- Grainy appearance
- Root only, adjacent to cementum
- Layer widens from CEJ to apex of root
- Unmineralised
Innervation of Dentin
- Intratubular nerves, with close association with odontoblast
- Nerve endings packed with vesicles of neurotransmitter?

3. Pain Transmission Theories
- Direct neural transmission
o Nerve endings in the dentin, provoke pain sensation after being stimulated
o No nerve fibres demonstrated in dentin near DEJ
- Transduction
o Odontoblastic process excited by stimulus, able to transmit impulse due to the
origin of neural crest cells
o No neurotransmitter vesicles present in the gap junction
- Hydrodynamic
o Presence of dentinal fluid in dentinal tubules
o Stimuli affect movement of the fluid by mechanical disturbance of nerves that are
associated with the odontoblastic processes
o These stimuli can be heat, cold, desiccation, mechanical, chemical or osmotic
pressure