Dentine

• describe Dentine

  Dentine is the hard tissue component of the pulp-dentine complex

  
• what does mature dentine consist of?

  - 70% inorganic material (hydroxyapatite)

  - 20% organic material (mainly type 1 collagen)

  - 10% water.
• Dentine is harder than overlying enamel, and slightly harder than bone

  TRUE/FALSE

  FALSE

  
  

  Dentine is softer than overlying enamel due to its higher water and organic content, but dentine is slightly harder than bone
• what does dentine look like in radiographs?

  dentine is more radiopaque (lighter) than bone, but more radiolucent (darker) than enamel

  
• what are the histological differences between enamel and dentine which affect the bonding strategy during treatments?

  • Enamel:

  acid etching of prismatic enamel leaves behind a roughened mineral surface to which materials can bond

  
  

  • Dentine:

  acid etching removes the mineral but leaves behind a layer of soft collagen to which materials must bond

  
  

  (Acid etching is using an acidic substance to prepare the tooth's enamel/dentine for the application of dental adhesive. The layer is microscopically roughened as a result of the acid, which results in increased retention (absorption) of the resin sealant)
• Unlike enamel, dentine is a living tissue, even after tooth eruption

  TRUE/FALSE

  TRUE
• The pulp and dentine can be considered as a single developmental and functional unit.

  TRUE/FALSE

  TRUE

  
  

  -> the pulp tissue supports the odontoblast to help them produce and maintain the dentine tissue
• what is the function of Dentine and the pulp?

  • Structural support and site of attachment for enamel and cementum

  • Sensitivity (nociception)

  • Mechano-sensory (proprioception)

  • Immune responsive

  
• what are the dentinal tubules in the dentine?

  they are the the trackways left behind by the dentine producing cells: the odontoblasts.

  
• what is in each dentinal tubule?

  • Odontoblast processes (produced by odontoblast)

  • Peritubular fluid**

  • Nerve filaments

  • More dentine (over time)
• what happens to the odontoblasts as they produce the dentine?

  Odontoblasts do not become entombed in their matrix

  -> the dentine tubules mark their path as they migrate away from the dentine secretory front.
• what are the Two types of curvatures of the dentine tubules?

  • Primary (S-bends, longer term)

  as the dentine walls converge in on each other the odontoblast makes room for each other by accommodating the s-bend

  
  

  • Secondary (squiggly undulations, shorter term)

  odontoblasts wiggly up and down as they produce dentine
• what several types is dentine subdivided into based on their topological, histological, and developmental properties?

  • Intertubular dentine

  • Peritubular dentine

  • Coronal dentine

  • Radicular dentine

  • Sclerotic/Translucent dentine
• describe Intertubular dentine

  More fibrous matrix.

  
• describe Peritubular dentine

  • Deposited gradually by odontoblast processes along the walls of the dentine tubules.

  • Hypermineralized compared to intertubular dentine.

  • NO collagen!

  • over time the peritubular dentine constricts the width of the Tubules (so tubule diameter decreases with age)

  -> this also decreases the sensitivity of this region of dentine

  
• describe Coronal dentine

  • Dentine within the crown

  • Underlies the enamel

  
• describe Radicular (root) dentine

  • Dentine within the root

  • Underlies the cementum

  
• describe Sclerotic/Translucent dentine

  dentine that forms from occlusion (infilling) of tubules, often with peritubular dentine (sometimes with mineral only).

  
  

  • Gives dentine a glassy appearance (hence "translucent dentine").

  • Occurs naturally with age, reducing the porosity/permeability of dentine.

  
• what types of dentine are there at different stages of development?

  1. Primary dentine

  (formed before root completion)

  
  

  2. Secondary dentine

  (formed after root completion rhythmically every day)

  
  

  3. Tertiary dentine

  (related to the adaptive role of dentine)
• primary dentine

  
  

  what are the layers of primary dentine (put them in the order they come in- earliest to latest)?

  1. Mantle (in the crown)

  2. Circumpulpal (crown and root- around the pulp)

  2. Root/Radicular
• primary dentine

  
  

  describe mantle dentine

  • The first dentine layer to form, 20-150 µm of dentine below the Enamel- Dentine Junction (EDJ)

  • Histologically distinct from the underlying circumpulpal dentine (matrix and mineralization patterns are unique).

  • Lots of branching dentine tubules

  
• primary dentine

  
  

  what makes the matrix and mineralization patterns of the mantle dentine unique?

  • Collagen fibers of mantle dentine matrix are oriented at right angles to the EDJ

  -> von Korff's fibers.

  
  

  • due to the odd angle orientation, it alters the optical appearance of mantle dentine under a microscope under crosspolarized light.

  
• primary dentine

  
  

  what are von Korff's fibers?

  collagen fibres of mantle dentine matrix that are orientated at right angles to the EDJ

  
• primary dentine

  
  

  describe Circumpulpal dentine

  • Forms the bulk of the dentine in the crown and the root.

  • Rhythmic deposition of dentine matrix by odontoblasts leads to the formation of different rhythmic growth lines.

  • Calcospheritic mineralization leaves large circular patterns in the mature dentine.

  
• primary dentine

  
  

  what causes the rhythmic growth lines in Circumpulpal dentine

  Rhythmic deposition of dentine matrix by odontoblasts
• primary dentine

  
  

  how does Circumpulpal dentine mineralise?

  via Calcospheritic mineralisation:

  
  

  -> calcospherites (globular mineralizations of the collagen matrix) can form.

  If neighbouring calcospherites fail to merge, globular dentine is formed.

  
• primary dentine

  
  

  what makes Circumpulpal dentine different from the mantle dentine?

  • Matrix collagen fibers are oriented parallel to the EDJ/secretory front (unlike in mantle dentine)

  • Circadian (daily) variation in odontoblasts' matrix secretion rates and collagen fiber orientations generate von Ebner lines (~3-4 µm per day).

  • Supra-daily (~5-9 day rhythm) variations that coincide with changes in dentine tubule curvatures manifest as contour lines of Andresen.
• primary dentine

  
  

  what are von ebner lines in circumpulpal dentine?

  Circadian (daily) variation in odontoblasts' matrix secretion rates and collagen fiber orientations generate von Ebner lines

  (~3-4 µm per day).

  
• primary dentine

  
  

  what are contour lines of Andresen in circumpulpal dentine?

  Supra-daily variations that coincide with changes in dentine tubule curvatures manifest as contour lines of Andresen.

  (~5-9 day rhythm)

  
• primary dentine

  
  

  what are the 2 layers that Root/radicular dentine has?

  • Hyaline layer of Hopewell-Smith

  • Granular layer of Tomes
• primary dentine

  
  

  describe the Hyaline layer of Hopewell-Smith


  • Thin region (around 10 microns thick) lacking tubules or other features

  • Appears clear in thin section ("hyaline") and is adjacent to the cementum

  • May contain more enamel-like matrix proteins

  • Serves to bond dentine to cementum?

  
• primary dentine

  
  

  describe the Granular layer of Tomes

  • Hypomineralised regions?

  • Special arrangement of proteins?

  • Looped ends of dentine tubules?

  
  

  -> Many interpretations, but its appearance along the outermost regions of the root dentine and close to the cementum is very consistent

  
• secondary dentine

  
  

  when does secondary dentine develop?

  after root formation is complete
• secondary dentine

  
  

  what is the mineral content of secondary dentine?

  Same mineral content as primary dentine, but develops more slowly and less regularly
• secondary dentine

  
  

  how does secondary dentine grow?

  Grows continuously throughout life of tooth, but not evenly, resulting in pulp recession (decrease in pulp volume with age)

  
• secondary dentine

  
  

  what is the boundary between primary and secondary dentine usually marked by?

  a contour line, due to change in odontoblast/tubule direction

  
• tertiary dentine

  
  

  what is tertiary dentine deposited as a response to?

  an external stimulus (caries, trauma, attrition etc.).

  
  

  -> Odontoblasts and resulting dentine matrix will respond differently depending on severity of the stimulus.
• tertiary dentine

  
  

  if the stimulus is mild/slow, how do odontoblasts and resulting dentine matrix respond?

  odontoblasts may react and deposit reactionary dentine (tubules continuous with those of secondary/primary dentine, mineralization pattern may be different).
• tertiary dentine

  
  

  if the stimulus is strong/fast, how do odontoblasts and resulting dentine matrix respond?

  odontoblasts die, new odontoblasts deposit reparative dentine (irregular, tubule-poor, sealing tissue).