Insufficient salivary flow decreases buffering capacity, leading to and sustaining an acidic environment.36 A dry oral environment favors the proliferation of acidogenic cariogenic pathogens, such as Streptococcus mutans and Lactobacillus spp. Acidogenic microbes are responsible for the initial pH drop. In response to the acidic environment, aciduric microbes initially change their gene expression to tolerate lower pH levels. Once acclimated to the lower pH levels, aciduric microbes begin acid production that further supports continued low pH levels.41-46
S. mutans and Lactobacillus spp., have long been associated with the caries process43,44 and are relatively easy to identify and culture, but research has shown 10% of subjects with rampant caries do not have detectible levels of S. mutans.42,45,46 Candida albicans is often present in plaque biofilms of children with early childhood caries.47,48
Root caries in elderly patients is associated with complex, polymicrobial communities that vary from subject to subject; however, S. mutans, lactobacilli and Actinomyces are typically present.49 Dozens of acidogenic and aciduric microbes are now implicated in the caries process, with some organisms favoring specific tooth surfaces or primary or secondary dentition.45
Candida albicans, a common and aggressive fungal organism, favors a highly acidic environment.50 Patients with dry mouth are at increased risk for oral candidiasis infections. C. albicans can be associated with periodontal disease.43,50
It is now possible to identify the presence of Streptococcus mutans, Streptococcus sobrinus and Lactobacillus casei, bacteria that are known to increase caries risk. The simple-to-administer test uses an oral rinse saliva sample that can be collected chairside. The same saliva sample can be used to determine the presence of a variety of Candida species.
Erosion is defined as the loss of hard tooth structure as a result of acid demineralization that does not involve bacterial activity. It is considered the leading cause of erosive tooth wear (ETW) and dentinal hypersensitivity (DH). Both ETW and DH are fueled by dietary factors and are exacerbated by dry mouth.30,36
Research has shown that patients with hypersensitivity have eight times more open dentinal tubules that are twice the mean diameter than those who do not have this problem.51 The prevalence of dentinal hypersensitivity is rising in all age groups and is directly related to dry mouth syndrome and dietary behaviors. Decades ago, hypersensitivity was primarily a problem reported by adults, but young children are now showing signs of erosion.36,52
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