Minimum Intervention: The Oral Ecosystem - Homeostasis and the Demin/ Remin Balance

Question 1

Composition of enamel

Answer 1

• 85-90% apatite by volume
• 2-3% protein and lipid
• 5-10% water
• Aprismatic/ amorphous (highly mineralised)
• Comprised of enamel rods: HAP crystals
• Laminar pores consist of water (ultrafiltrate) and proteins)

Question 2

What does the protein and moisture between enamel rods help with?

Answer 2

Physical properties of enamel: compressive stress and tensile stress

Question 3

Properties of enamel

Answer 3

• High compressive and tensile strength
• Supported by dentine
• Hardest biological tissue in the body
• Amorphous, acellular and avascular

Question 4

Composition of dentine

Answer 4

• 70% inorganic by weight
• 20% organic by weight
• Dentinal tubules: odontoblastic processes
• Lumen wider near the pulp
• More tubules near the pulp
• Intertubular dentine: mineralised collagen matrix
• Intratubular/ peritubular dentine: highly mineralised, smaller crystals than enamel

Question 5

Properties of pulp

Answer 5

• Positive fluid flow from the pulp outwards
• Fluid flow out contains Ca2+, PO4-, etc. = deposition of mineral
• Reduced tooth sensitivity with age

Question 6

Saliva

Answer 6

• Watery fluid produced by salivary glands (major and minor)
• Supersaturated with minerals (calcium, phosphate) that interacts with the enamel structure, as part of the remin cycle
• As part of the demin cycle, calcium and phosphate are displaced, into the saliva
• Buffering system in buffers: helps maintain the stable pH
• Flow rate of saliva, as well as whether its stimulated or unstimulated affects the oral environment
• Saliva can wash away hydrogen ions from the tooth’s surface, preventing demin

Question 7

Salivary glands

Answer 7

• Major
  o Sublingual: mainly mucous (some serous
  o Submandibular: mainly serous (some mucous)
  o Parotid: serous makeup, stimulated saliva has bicarbonate (buffering)
• Minor
  o All mucous except Von Ebners = circumvallate papillae (serous)
  o Everywhere in mouth, except gingiva (masticatory mucosa)

Question 8

What can dry mouth result in?

Answer 8

Dry mouth results in mucosal dryness and soreness, burning sensation of mucosa and tongue, difficulty wearing dentures, third, try lips, atypical caries pattern (root surfaces, smooth surfaces, cusp tips), and increases frequency of oral infections

Question 9

Biofilm

Answer 9

• Sticky film on tooth surface, made up of bacteria, and proteins (statherin), food debris etc. 97-99% of bacteria is in biofilms, whereas 1-2% is ‘free’ planktonic bacteria
• Components of biofilms (pellicle – proteins, bacteria, plaque fluid and ions, extracellular polymers) form a climax community: stable, but still dynamic
• Biofilm composition varies between sites in the mouth, i.e., interproximally, pits, fissures, sub-gingivally, crowded teeth
• Saliva interacts with the biofilm, resulting in higher concentration of ions in biofilm
• pH of biofilm is affected by diet. High protein, low carb = slightly alkaline. High carb, low protein = slightly acidic
• Epithelial cells in the biofilm are an active part of the immune system, and a physical barrier to bacteria. These cells produce molecules that keep mucosal bacteria (biofilms) in check. Turnover of epithelial cells also keep biofilms in check

Question 10

Sialo-Microbial-Dental Complex

Answer 10

Symbiotic relationship between saliva, biofilm and teeth. Facilitates mineral maintenance

Question 11

Understand how the oral biofilm has changed over time causing an imbalance and hence disease.

Answer 11

As diet has changed (more refined, softer food, refined carbs, e.g., sucrose, fermentation), to a more acidic diet, acidification of the biofilm has begun. This has resulted in changes in the ecology of the biofilm.
- ‘Good bacteria’ are lost
- Select for acidogenic and aciduric micro-organisms
- Resting pH lowered

Question 12

Understand the biochemical interactions that cause caries and erosion.

Answer 12

These factors result in demin being favoured opposed to remin – this is imbalance. More demin occurring results in diseases, like caries, manifesting. This often first appears as a white spot lesion. Caries manifest from demineralisation from acid attack from bacterial sources, i.e., from carbohydrate metabolism. These irregularly break down enamel rods, down the side. This can be repaired (to a certain degree) through remineralisation. Caries are slow manifesting.
Demineralisation that occurs because of acid from non-bacterial sources, i.e., from acid from diet that directly comes into contact with the tooth enamel, is known as corrosion. In these situations, acid displaces the saliva Corrosion shortens enamel rods. This cannot be repaired at all. This appears clinically as ‘dished’ or ‘scooped’ lesion – not a white spot. Erosion cares over a short time period typically.

Question 13

Pathogenesis of caries

Answer 13

1. Formation of plaque. This contains harmful bacteria that metabolise sugars to produce acids
2. Acid attack, from acids produced by bacteria in plaque. This can lead to demin of enamel, weakening the structure, creating a small hole or cavity
3. Cavity formation: over time, demin continues, and cavity gets bigger. If left untreated, cavity can progress deeper into the tooth, reaching the dentin layer

Question 14

Pathogenesis of erosion

Answer 14

1. Acidic exposure, from sources like acidic foods, drinks, or stomach acids
2. Acid attacks the enamel, causing it to soften and lose minerals (demineralisation). This occurs without bacterial involvement
3. Repeated acid exposure gradually wears away the enamel, making teeth thinner, and more prone to sensitivity and damage