ISD4 The Dentine Pulp Complex

Dentine:

• The internal mineralised structure of the tooth

• It’s overlaid by enamel in the crown and cementum in the roots

  • At the CEJ, you can have either/both/neither enamel and cementum

• Dentine composition: 70% mineral, 20% organic and 10% water.

  • 45% volume of calcium hydroxyapatite (mineral)

  • 30% volume of collagen (90%) and non-collagenous proteins (DPP&DSP) (organic)

  • 25% volume of water

• Is not quite as hard as enamel but the added water/collagen/organic components give it more elasticity.

• Early dentine is similar to bone

  

  • Osteocytes embedded in the bone

  • Single units of osteons

  • Through the middle of each osteon is the Haversian canal

  • Polarised odontoblasts on the periphery with trailing odontoblast process

    • It migrates away from the dentine as it lays down so it ends up on the inner surface of the dentine

    • As they are producing the dentine precursor and mineralising it, they leave behind the odontoblast process. This occupies the dentinal tubule

• Many dentine variations:

  • Primary:

    • Mantle:

      • Peripheral dentine (supporting overlying enamel)

    • Peritubular Or Intertubular dentine:

      • Circumpulpal dentine (overlies the pulp)

  • Secondary

  • Tertiary (reactionary or reparative)

• Primary dentine = 3-3.5mm thick

  • Predentine matrix secreted by cells that become mineralised

  • Mantle:

    • Atubular

    • 20um thick

    • Under/unphosphorylated proteins

    • Elastic/Resilient

    • Dissipates forces to avoid fracture propagation

    • Tomes Granular Layer/Tomes Layer)

  • Intertubular dentine - predentine mineralises - 4-10um per day

  • Peritubular (Intra) - odontoblast process modifies amorphous matrix

    • 15% more mineralised than intertubular

    • Accelerated with tubular sclerosis during an insult

    • Reduces permeability of dentine to endodontic irrigants i.e. older teeth or those which have had chronic inflammation are less permeable to irrigants

Amelodentineal Junction:

• Scalloped in appearance at areas of high-load

• Dentinal tubules follow S-shaped curvature - “Primary curvatures” - more pronounced in the crown than the root.

• Secondary dentine

  • Commences production when the tooth becomes functional

  • <1 micron per day

  • Becomes the most internal layer of circumpulpal dentine

  • Very similar structure to primary dentine

• Tertiary dentine

  • Reactionary - upregulation of pre-existing odontoblast layer to secrete more predentine which is subsequently mineralised

  • Reparative - Odontoblast cells are killed or removed and then local stem cells/progenitor cells are recruited to repair the tissue. Atubuler, an irregular structure that is rapidly produced following more severe insults that disrupt the odontoblast layer.

Key Player = Odontoblast

→ Cells polarise

→ Produce pre-dentine

→ Secrete non-collagenous proteins and enzymes that initiate mineralisation

• Condense together as cells migrate centrally from ADJ to pulp so the surface area of the dentine-pulp layer is less than at the enamel-dentine layer. This means that the odontoblast process and dentine tubules condense closer together so they occupy a greater area. Therefore, there are more dentinal tubules towards the pulp than the ADJ.

  • Tubular % surface area:

    • 1% just beneath the enamel

    • 22% towards the pulp

    This increase is associated with a corresponding increase in the dentine water content towards the pulp

  • Diameter of the tubules:

    • 3um adjacent to the pulp

    • ~0.8um near the ADJ

    If you were trying to reduce the depth of your restoration, as you go further into the dentine, you are exposing more tubules and wider tubules.

  • Length of odontoblast process:

    • 0.1-1mm in length (approximately the inner third of dentine)

    The shallower the restoration, the better in order to disrupt less odontoblast processes.

Dental Pulp

• Unmineralised, loose connective tissue

• Vascular

• High water content (~75%)

• Organic components predominantly type 1 and 3 collagen

• Cellular components predominantly fibroblasts

• Peripheral odontoblasts

• Immune cells - lymphocytes, macrophages, dendritic cells

• Endothelial cells (pericytes) and lymphatic vessels also

Pulp-Dentine Complex

AKA - Dentopulpal Complex/Dentine Pulp Complex

Dentine protects the pulp ←→ Pulp serves the dentine

• The odontoblasts process extends into dentine

• It is best to consider both structures as one

Zones of the Pulp

1. Odontoblast layer

2. Cell free zone

3. Cell rich zone

4. Pulp core

• Histological zones

• Pulp site-dependent

• It is best considered a continuum

Peripheral Fishnet Appearance:

• Central arterioles and venules

• Subodontoblastic plexus (beneath the dentine, immediately below the odontoblasts)

• Aterio-venous and venous-venous anastomosis surrounding these structures

Embryology

• Tooth development involves complex interactions between Ectoderm (external layer) and Mesenchyme (internal layer)

• Epithelium forms from Ectoderm - enamel is ectodermal origin

• Neural crest cell migration is imperative for dentine, pulp, cementum - ectomesenchyme

Amelodentinal Junction:

• Inner enamel epithelium and dental papilla

• Ameloblasts (enamel producing)

• Odontoblasts (dentine producing)

Functions of the Pulp:

• To create dentine

• Supply nutrients to the odontoblasts

• Innervate the tooth

• Defend against insult, especially bacteria

Pulpal Inflammation

• Predominantly opportunistic micro-organisms

• Caries (most common)

• Acid-producing bacteria - demineralises dentine

• Sequestered growth factors are liberated (liberated-dentine-derived ECM proteins)

• Diffuse into odontoblast layer

• Odontoblasts upregulate secretion

• Innate responses - vascular changes:

  • Normal blood flow in the pulp

  • Normal fluid flow into dentine

  Can be caused by drilling and causing damage to odontoblast processes which, in turn, release cytokines and cell mediators which increase blood flow and increase the likelihood of causing pulpitis

• Cellular responses follow - upregulation

Pulpal Innervation and Pain

• Pupal nerve fibres - A-delta, A-beta, C fibres and sympathetic fibres

• Peripherally-sited A-delta (myelinated)

• Centrally-located C-fibres (unmyelinated)

• The majority of nerve fibres are reported to be unmyelinated

• A-delta = short sharp pain of short duration

• C-fibres = dull aching pain associated with more advanced pulpal inflammation.

Hydrodynamic Theory:

• Peripherally sited A-delta (myelinated)

  • Not thermally mediated

  • Outward flow of fluid due to contraction and expansion of dentine to the thermal changes

• Cold = outward flow

• Heat = inward flow

Indirect Pulp Cap

- Cavity ½ dentine depth

• Assuming pulpal pressure stays the same

  • Radius increases x16

  • Length of tubule x0.5

  • Fluid flow increase x32

- Cavity ¾ dentine depth

• Assuming pulpal pressure stays the same

  • Radius increases x256

  • Length of tubule x0.25

  • Fluid flow increases x1024

Key Message:

• Deeper cavities:

  • Expose a greater number of tubules

  • These tubules have a greater diameter (i.e. surface area)

  • Cause greater damage to odontoblast processes i.e. less reactionary dentine

  • Have greater fluid flow

  • Wet environment for bonding

  • Allow greater pulpal irritation from restorative materials

Vital Pulp Therapies

“Strategies aimed at maintaining the health of all or part of the pulp”

i.e. avoiding RCT or XLA

1. Indirect pulp cap

2. Selective removal CT (1 stage) to firm or soft dentine

3. Stepwise excavation (2 stage)

4. Non-selective removal CT (total caries removal)

5. Direct pulp cap

   a. Class I - trauma or iatrogenic

   b. Class II - deep/extremely deep carious lesion

6. Partial pulpotomy

7. Full pulpotomy

Clinical diagnosis is fundamental:

• Pulpal diagnosis’Depth and extent of caries (revisit ICDAS)

Take Home Message:

• Asymptomatic tooth

• Reversible pulpitis

• Deep caries

= Avoiding pulp exposure is considered best practice!

Includes: severe reversible pulpitis - increased pain to stimuli for more than several minutes that may require analgesics (Do options 1-3 from above)

• Irreversible pulpitis

= Requires caries removal and pulp exposure

Most cases will require partial/full pulpotomy

Vital Pulp Therapies

What to do if you expose the pulp during caries removal?

→ Place cotton pellet soaked in saline to stop bleeding

→ Place biodentine and review

• Hydraulic calcium silicate cement

• Antibacterial

• More consistent dentine bridge than CaOH

• Remineralise dentine

• Weak mechanical characteristics

→ Speak to supervisor if not in scope (adult tooth)

If biodentine is not available, then:

1. Setting CaOH cement should be used e.g. DyCal or Life

2. Non-setting CaOH paste e.g. HypoCal

Then on top you use GIC or zinc oxide eugenol.