Causes
The dental effects of long-term methamphetamine use are often attributed to its effects on saliva. The reduction in saliva increases the likelihood of dental caries, enamel erosion, and periodontal disease. Although it is clear that use of the drug decreases saliva, the mechanism by which it does so is unclear. One theory is that the drug causes vasoconstriction (narrowing of the blood vessels) in salivary glands, decreasing salivary flow. This constriction is thought to be due to the activation of alpha-adrenergic receptors by norepinephrine, the levels of which are dramatically increased by methamphetamine use. These factors can be compounded by dehydration, which occurs in many methamphetamine users after drug-induced increases in metabolism. The characteristics of the saliva produced during use of the drug, which includes high protein content, may also contribute to the sensation of dry mouth.
Long-term methamphetamine use can cause parafunctional habits, routine actions of a body part that are different than their common use, which can result in tooth wear and exacerbate periodontal diseases. One such habit that may affect the development of meth mouth is bruxism, particularly as the drug's effects wane and stereotypy occurs, a phase that is often referred to as "tweaking". This bruxism may be due to a drug-induced increase in monoamines. Other behaviors of long-term methamphetamine users that may cause or accelerate the symptoms of meth mouth are the failure to pay attention to oral hygiene and excessive food intake during binges, especially sugary foods; the drug's users often report strong cravings for sugar and consume large amounts of high-sugar beverages. The altered mental state that accompanies methamphetamine use lasts longer than that of some other common drugs, increasing the amount of time the user engages in drug-induced behavior.
No academic reviews have supported the idea that the use of hydrochloric acid in methamphetamine's manufacturing process contributes to dental decay. Speculation that oral consumption of the drug causes tooth decay by raising the acidity of users' mouths is also unsupported. Meth mouth is generally most severe in users who inject the drug, rather than those who smoke, ingest or inhale it.
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