Biological factors - Saliva

Saliva plays one of the most important roles in the prevention and neutralisation of acid attacks. The efficacy of saliva against erosion is determined mainly by its composition and flow rate, which both are thought to vary within populations.


Composition:

  • Saliva is the source of the dental pellicle, which is a thin protein based layer on tooth surfaces that acts as a diffusion barrier and initially inhibits acid attacks.
  • Therefore, the pellicle reduces mineral loss during an acid attack.
  • A prolonged drop in pH results in the loss of most of the pellicle and consequently loss of protection against erosive (and abrasive) challenges.


Flow rate:

  • Salivary flow rate increases already before the direct exposure to acids, by visual or odour stimuli and, therefore, acts preventively (Christensen & Navazesh 1984, Lee & Linden 1992, Engelen et al. 2003).
  • Therefore, under normal conditions, even before direct exposure to acids, the tooth environment will show an increased buffering capacity through increased levels of carbonate, phosphate, calcium and fluoride ions.
  • Salivary flow rate will also increase before vomiting, but not before regurgitation, which is an involuntary response and thus independent of the autonomic nervous system.
  • Intra-oral stimuli and mastication also ensure an adequate saliva flow and protection of teeth.


Other factors:


  • Apart from the salivary flow rate and composition, the individual exposure of teeth to saliva plays an important role for the susceptibility of teeth to erosive processes.
  • For example, the facial tooth surfaces of upper incisors are more prone to erosion than lingual surfaces of lower teeth.

Exposure of enamel to saliva in vitro restores enamel resistance to erosive attacks within about an hour (Wetton et al. 2006). However, in situ, estimates for the time required are less conclusive due to variations in individual salivary flow rate and composition of the saliva. Up to 24 hours may be needed (Hannig & Balz 1999).

Click here to review possible effects of dental hygiene.
You may consider recommending tooth-friendly chewing gum to your patients. As chewing triggers salivary flow, patients may benefit from the erosion-protection properties of saliva.