The principal hypothesis of this study is that SS patients are at a higher risk of caries development not just because of reduced salivary flow (xerostomia) but also changes in the output of organic and inorganic microbial regulatory components in saliva secondary to their auto-immune disease. These alterations favor a selective increase in the proportion of cariogenic microflora in plaque located on their teeth. Specifically, mutans streptococci (MS) and Lactobacillus (LB) species are increased in frequency and number in SS patients compared with xerostomic patients with no detectable auto-immune disease.