July 10th, 2009 by admin

Anticariogenic actions of saliva
Theoretically saliva can in uence the carious process in several ways (see
box).
Although there is no doubt that saliva possesses all the anticaries prop-
erties listed below, research workers have been frustrated in their attempts to
directly relate any particular salivary factor to the incidence of caries.
One of the reasons for their failure is the fact that caries is a process occur-
ring intermittently, in which host, microorganisms, and substrate are all
involved. Since saliva has the ability to affect all of them in several different
ways, it becomes easy to understand the difficulties encountered in trying to
evaluate any single anticaries factor at any one time. Nevertheless, there
is sufficient evidence to demonstrate a negative correlation between buffer-
ing capacity of stimulated and unstimulated whole saliva and caries. In addi-
tion, there is no doubt that when saliva is absent, or drastically reduced in
HOW SALIVA INFLUENCES THE CARIOUS PROCESS
• The  ow of saliva can reduce plaque accumulation on the tooth surface and
also increase the rate of carbohydrate clearance from the oral cavity.
• The diffusion into plaque of salivary components such as calcium,
phosphate, hydroxyl, and  uoride ions can reduce the solubility of enamel
and promote remineralization of early carious lesions.
• The carbonic acid–bicarbonate buffering system, as well as ammonia and
urea constituents of the saliva, can buffer and neutralize the pH fall which
occurs when plaque bacteria metabolize sugar. The pH and buffering
capacity of saliva is related to its secretion rate. The pH of parotid saliva
increases from about 5.5 for unstimulated saliva to about 7.4 when the  ow
rate is high. The respective pH values for submandibular saliva are 6.4 and
7.1. An increase in the secretion rate of saliva also results in a greater
buffering capacity. In both cases this is due to the increase in sodium and
bicarbonate concentrations.
• Several non-immunological components of saliva such as lysozyme,
lactoperoxidase, and lactoferrin have a direct antibacterial action on plaque
micro ora or may affect their metabolism so that they become less
acidogenic.
• Immunoglobulin A (IgA) molecules are secreted by plasma cells within the
salivary glands, while another protein component is produced in the
epithelial cells lining the ducts. The total concentration of IgA in saliva may
be inversely related to caries experience.
• Salivary proteins could increase the thickness of the acquired pellicle and so
help to retard the movement of calcium and phosphate ions out of enamel
quantity, caries can be rampant. Hence caries preventive measures must be
taken when there is any interference in salivary function which diminishes
flow and when buffering capacity is low.