There are conditions that can affect the formation of enamel, and thus increase the risk of demineralization. These include the genetic disorder amelogenesis imperfecta, in which enamel is never completely mineralized and flakes off easily, exposing softer dentin to cariogenic bacteria. Other conditions are linked with increased enamel demineralization, such as gastroesophageal reflux disease (GERD) and the eating disorder bulimia, because stomach acid keeps the oral cavity highly acidic. Other special needs patients include those with an inability to remove plaque because of a mental or physical limitation, and patients with xerostomia (dry mouth) due to certain medications, cancer therapies, or conditions such as Sjögren’s Syndrome.1
While one could list a group of diseases that affect dental caries or one could simply categorize the diseases into a single category that involves simply those that either through direct involvement or through treatment affect salivary function and salivary flow. Anything that reduces salivary flow will surely increase dental caries. Caries attack rates in the absence of saliva can be 10-20 times as great as a normal individual.
An example of a condition like that could be, for example, a cancer of say the parotid gland or in the head and neck area where radiation treatments are used to treat the disease. The radiation treatments will destroy the salivary glands and their ability to function, so you inevitably have reduced salivary flow and enormous caries attack rates, in one month equivalent to what would normally be seen in perhaps two years in an individual.
Other diseases could be those that affect renal function and diabetes, or anything that causes the perception of dry mouth or the medications that are used to treat any disease. They may also reduce salivary flow and it’s recognized that the majority of medications that are prescribed for medical reasons have the ability to reduce, or the side effect of, reducing salivary flow.
So patients on medications are almost certainly at risk for increased caries.