September 14, 2012 — Intravenous heroin and methamphetamine abusers both suffer from the same patterns of rampant caries, suggesting the term "meth mouth" may be misleading, according to researchers reporting their findings in an article published in the September issue of the Journal of the American Dental Association.

"People assume they know what's going on with meth mouth, but I'm not sure that's the truth," coauthor Kevin Hursh, DDS, dental director at the San Francisco Native American Health Center and an assistant clinical professor at the University of California, San Francisco, told Medscape Medical News.

Many people think that meth mouth is caused by the direct effects of the smoked drug on the abuser's teeth, he said. But when the researchers surveyed people who inject heroin and people who inject methamphetamine, they found rampant dental decay similar to what has been called meth mouth.

Concerns about meth mouth may be increasing because the drug is being abused more often. The National Survey on Drug Use and Health in 2007 found that about 5% (13 million) of the US population older than 12 years had ever used methamphetamine, and in 2009 the agency reported an increase in the number of new methamphetamine users compared with the previous year, explain the authors.

Researchers have associated with meth users a pattern on buccal and lingual surfaces and widespread destruction of coronal surfaces. The pattern has come to be called meth mouth both in scientific and popular literature.

Possible Explanations

Possible explanations for the caries pattern include poor hygiene and diet, lack of dental care, and dry mouth. Others have theorized that methamphetamine may stimulate inhibitory alpha2-adrenergic receptors via the central nervous system, inhibiting unstimulated salivary flow.

However, the pattern can also be found in hyposalivation secondary to radiation treatment and has been reported in association with heroin and abuse of multiple drugs.

Researchers have never before studied a population of drug abusers to measure the prevalence of this pattern of caries.

To fill this gap, the researchers surveyed 17 people who predominantly used injected methamphetamine and 41 who predominantly used injected heroin. Both groups came from the Tenderloin neighborhood of San Francisco.

The meth group had a median of 28.6 decayed, missing, and filled surfaces, whereas the heroin group had 29.9. That difference was not statistically significant (P = .14), and neither was the number of residual roots: 18% of meth users and 2% of heroin users had 7 or more residual roots (P =.06).

The 2 groups were similar in age (18 - 36 years), and more than a third reported they had not had any lodging the night before. The only demographic difference the researchers found between the 2 groups was that more of the heroin users were white.

All the heroin users and 94% of the meth users smoked tobacco, with about half smoking at least a pack a day.

About half the meth users also drank 2 or more glasses of fruit juice per day compared with a quarter of the heroin users, but this difference fell just short of statistical significance (P =.06). A third of meth users drank 4 or more soft drinks per day compared with 5% of heroin users, which was also short of significance (P = .07).

Heroin users said they snacked more often, with 40% saying they had 6 or more snacks a day compared with 24% of meth users. Once again, however, the difference in snacking was not statistically significant (P = .25).

A third of meth users said they had "cotton mouth" often, and 35% said they needed to sip water to help them swallow food, but the researchers documented clinical signs of xerostomia, such as dry sticky oral mucosa, in only 29% of meth users and 39% of heroin users. Again, these factors were not statistically different from the heroin users.

Half Rarely Brush Their Teeth

About a half of both groups reported brushing their teeth seldom, if ever, and no participants from either group took advantage of an offer of a free dentistry appointment. In addition, median scores on the Simplified Oral Hygiene Index were statistically similar in the 2 groups.

Both groups reported using multiple drugs, calling into question the comparisons between the 2 groups, but previous studies have shown a strong correlation between the drug most used at baseline and the drug most used at subsequent visits, suggesting the 2 groups stuck largely to their predominant drugs.

The investigators conclude that a next step might include offering preventive measures such as chlorhexidine rinses or xylitol gum or the application of fluoride varnishes to injection drug abusers, regardless of the type of drugs. They suggest accomplishing this through outreach workers.

Asked to comment, Vivek Shetty, DDS, DrMedDent, a dentistry professor at the University of California, Los Angeles, told Medscape Medical News he didn't think offering prevention was practical. "Most of the dental decay results from an inability to focus on oral hygiene — the meth users are often caught up with their addiction," he said in an email.

Dr. Shetty and colleagues are working to distinguish a pattern of dental decay that truly separates meth abuse so that dental professionals can recognize it and refer patients for substance abuse treatment.

The study described in this article was supported by a grant from the National Institute of Dental and Craniofacial Research and a grant from the National Institute on Drug Abuse, National Institutes of Health, Bethesda, Maryland. The authors and Dr. Shetty have disclosed no relevant financial relationships.

JADA. 2012;143:992-1001. Full text