Decreased salivary flow rate is associated with increased dental caries because the buffering capacity of saliva is not present to balance the acidic environment created by certain foods. As a result, medical conditions that reduce the amount of saliva produced by the salivary glands, especially the submandibular gland and the parotid gland, are more likely to lead to dry mouth and consequently to widespread dental caries. Examples include Sjögren’s syndrome, diabetes mellitus, diabetes insipidus, and sarcoidosis.[49] Medications, such as antihistamines and antidepressants, can also impair saliva flow. Stimulants, most notably methylamphetamine, also block salivary flow to an extreme degree. This is known as meth mouth. Tetrahydrocannabinol (THC), an active chemical in cannabis, also causes an almost complete blockage of saliva, colloquially known as “cotton mouth”. Furthermore, 63% of the most commonly prescribed medications in the United States list dry mouth as a known side effect. [49] Radiotherapy to the head and neck may also damage cells in the salivary glands, which somewhat increases the possibility of caries formation.[50][51]
The susceptibility to caries can be related to an alteration of the tooth’s metabolism, in particular to the fluid flow in the dentin. Experiments in rats showed that a high-carosene diet high in sucrose “significantly inhibited the rate of fluid movement” in dentin. [52]
Tobacco use may also increase the risk of caries formation. Some brands of smokeless tobacco are high in sugar, which increases the susceptibility to caries.[53] Tobacco use is an important risk factor for gum disease, which can cause gums to recede. [54] When the gums lose attachment to the teeth due to gingival recession, the root surface becomes more visible in the mouth. If this occurs, root decay is a concern because the cementum covering the roots of the teeth is more easily hydrolyzed by acids than the enamel.[55] Currently, there is insufficient evidence to support a causal relationship between smoking and coronal caries, but evidence indicates an association between smoking and root surface caries.[56] Exposure of children to second-hand smoke is associated with tooth decay.[57]
Exposure to lead and neonates leads to tooth decay.[58][59][60][61][62][63][64] Besides lead, all atoms with an electrical charge and ionic radius similar to divalent calcium,[65] like cadmium, mimic the calcium ion, and thus exposure to it may promote dental caries.[66]
Poverty is also an important social determinant of oral health.[67] Dental caries has been linked to lower socioeconomic status and may be considered a disease of poverty.[68]
Models are available to assess the risk of dental caries when treating dental conditions; This system using Evidence-Based Caries Through Risk Assessment (CAMBRA).[69] It remains unknown whether identification of high-risk individuals can lead to more effective long-term patient management that prevents the initiation of dental caries and arrests or reverses the progression of lesions.[70]
Saliva also contains iodine and EGF. Effective EGF results in cellular proliferation, differentiation and survival.[71] Salivary EGF, which also appears to be regulated by dietary inorganic iodine, plays an important physiological role in maintaining oral (and gastroesophageal) tissue integrity, and on the other hand, iodine is effective in preventing dental caries and maintaining oral health [72].
