Dentinogenesis

Odontoblast differentiation
1. Ecto-mesenchymal cells of DP -> OD
2. Pre-OD to OD transformation - STRUCTURE RELATED TO FUNCTION
3. 1) IEE induces DP -> OD (BM presents signal via growth factors)
  1. RECIPRICOL INDUCTION
  2. Signal is required but also cells must have undergone certain number of cell divisions to be COMPETENT to receive the signal.
4. 2) OD secrete first pre-dentine, causes DBM to breakdown
5. 3) Pre-dentine is now in contact with IEE, causes IEE -> Ameloblast
  1. RECIPRICOL INDUCTION
6. OD's are said to be post-mitotic - cannot proliferate further
Dentine secretion
1. MANTLE dentine (first formed)
  1. Matrix contributions come from newly differentiated odontoblasts and cells of the dental papilla
  2. Mantle dentine is mineralised by MATRIX vesicles as OD have not fully developed the ability to mineralise dentine yet.
2. Circumpulpal dentine
  1. As the OD secrete matrix, they move pulpally (downwards), leaving a single OD process in dentinal tubule running through matrix. This permits communication with rest of matrix.
  2. S-shape in crown, Straight course in root
  3. Two main sites (vary in composition, not just orientation - > i.e. different to prismatic/interprismatic variations of enamel)
  4. ITD - inbetween the tubules - rest of the matrix that isn't PTD. Secretion of COLLAGEN + PG's into PreD from CELL BODY of OD - NOT secretory process. Essentially -> a collagenous matrix.
  5. PTD - immediately surrounding the tubular process of OD. Secretion of tissue specific matrix components at mineralisation front - e.g. PG's + phosphoproteins. LACKS collagenous fibres of ITD. >15% more mineralised. Essentially -> highly mineralised, ground substance rich matrix.
Background info
1. Begins at 17-18 weeks in utero
2. LATE bell stage in tooth development
3. Starts at cusp tips (gradient of secretion cervically - same as enamel)
4. Dentine secretion begins straight after DP -> OD
5. OD always on FORMATIVE SURFACE (OD-preD-Dentine)
6. Vital tissue - important to maintain D/P complex for functional dentition/tooth
Types of dentinogenesis
1. Primary dentine - until completion of root formation
2. Secondary dentine - much more slowly secreted than primary dentine. Secreted throughout life -> leads to pulp chamber occlusion.
3. Tertiary dentine (REACTIONARY) - if OD's survive caries attack
4. Tertiary dentine (REPARATIVE) - if OD's killed, generation of new OD-like cells to produce 3° dentine

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Dentinogenesis

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	Created by 0 9 over 8 years ago