BDP: Caries 2 - Remineralisation and salivary flow

Remineralisation

• Remineralisation means regrowth and repair of existing hydroxyapatite (HAP) crystals - the return of minerals to previously demineralised dental hard tissue

• The main ions ionvolved are calcium (Ca²+), phosphate (PO4³-) and flourid (F-), coming mainly from saliva and flouride- containing agents. They diffuse through enamel pores into the demineralised area.

• Flouride can become incoporated into the mineral structure, making the remineralised enamel more resistant to future acidic attacks. Demineralised enamel can therefore also act as a flouride reservoir

• Process: Minerals (Ca²+, PO4³- and F-) → diffused into demineralised enamel → regrowth of mineral crystals → stronger enamel

Remineralising materials

• Different agents can promote remineralisation by combining the minerals together in the intact enamel

• A remineralising agent that help shift the dynamic balance away from demineralisation and toward remineralisation - Xylitol: Xylitol-containing products stimulate saliva flow (increases the secretion ratio of saliva), which improves buffering, increases the pH and results in higher Ca²+, PO4³- and HCO3- concentration. This supports a less cariogenic environment.

How we can reduce demineralisation

1. Reduce cariogenic plaque

• Mechanical removal: tooth brushing, dental floss and other mechanical plaque control

• Antibacterial functions: saliva

• Vaccine?

2. Reduce bacterial acid production

• Reducing the frequency of fermentable/refined carbohydrate intake

• Supporting salivary flow

3. Neutralise/remove acids

• Mainly through the buffering and clearance functions of saliva

Functions of saliva

• Saliva has physical, chemical and antimicrobial functions, which together generally protect against caries.

1. Physical protection

• Lubrication: mucins form a protective layer over oral hard and soft tissues

  • Protects soft tissues from desiccation and teeth from abrasion

• Flushing/rinsing: removes food debris, carbohydrates, acids and microorganisms

• Moistens food → facilitates chewing and swallowing

2. Chemical protection

• Buffering: neutralises bacterial acids and helps restore the pH after an acidic attack

• Maintins saliva supersaturated with Ca²+ and PO4³- → promotes remineralisation and reduce mineral loss

• Higher salivary flow rate → better clearance, buffering and mineral availability

3. Antimicrobial protection

• Saliva contains several antimicrobial components, lysozome among other components, which damages bacterial cell walls

4. But can also promote caries… (aggressive function)

• Some salivary components can support dental plaque and carbohydrate metabolism:

  • Mucins → can help with plaque formation by trapping bacteria

  • Salivary amylase → an enzyme that breaks down long-chain carbohydrates into msaller carbphydrates that bacteria can use

  • Carbohydrate hyperconcentration → increase bacterial acid production → promotes demineralisation

Salivary flow rate

• Unstimulated/resting saliva

  • Produced continuously when you are not eating or chewing and comes predominantly from the submandibular glands.

• Stimulated saliva

  • Increases during activities such as chewing

  • Gives approximately 1-2 mL/min

  • Higher salivary flow is generally protective because it means faster clearance of acids and carbohydrates + greater buffering capacity + greater availability of mineral ions

    • Xerostomia: If the salivary secretion of stimulated saliva is less than 0,7 mL/min - this stage is called xerostomia

      • Subjective sensation: “Dry mouth”

      • Objectively: Hyposalivation