A low concentration of carbonic anhydrase isoenzyme VI in whole saliva is associated with caries prevalence

Carbonic anhydrases maintain pH homeostasis in various tissues of the human body by catalyzing the reversible reaction CO2 + H2O double left right arr ow HCO3- + H+. Carbonic anhydrase isoenzyme VI (CA VI) is secreted into hum an saliva by the serous acinar cells of the parotid and submandibular gland s. Although it represents about 3% of the total protein in stimulated parot id saliva, its exact physiological significance in the saliva has not been established. In the present study, saliva samples were collected under stri ctly controlled conditions from young, healthy men and assayed for CA VI co ncentrations using a specific time-resolved immunofluorometric assay. Saliv ary secretion rate, pH, buffering capacity, alpha-amylase activity levels, lactobacillus and Streptococcus mutans counts were also determined, and the results were correlated with the dental status of the subjects. Salivary C A VI concentration, pH and buffering capacity values correlated negatively with the numbers of decayed, missing and filled teeth (DMFT index). The cor relations between salivary CA VI concentration and DMFT index were most sig nificant in subjects with poor oral hygiene. No correlation was found betwe en salivary CA VI concentration and lactobacillus or Streptococcus mutans c ounts. As predicted, salivary lactobacillus and Streptococcus mutans counts sh owed a close positive correlation with the DMFT index. In contrast, no significant correlation was seen between salivary secretion rate or amylase activity and the DMFT index. The present results indicate that low salivar y CA VI concentrations are associated with increased caries prevalence, par ticularly in subjects with neglected oral hygiene.