Summary The use of cannabis by adolescents in Switzerland has almost doubled in the past decade. Empirical observations in private dental practices indicate that cannabis users have more carious lesions than those who do not use cannabis. The aim of this study was to investigate the hypothesis that regular cannabis use increases the risk of caries because of hyposalivation or lifestyle. Forty-three regular cannabis users were enrolled in the test group and 42 tobacco smokers were used as a negative control group. All subjects were 18–25 years old. Data were
obtained using a standardized questionnaire and a clinical examination. There was no significant difference between
groups in decayed and filled surfaces (DFS), saliva flow rate and plaque and gingival indices. The cannabis group had, however, significantly higher DS (decayed surface) values (p = 0.0001) and significantly lower frequencies
of daily tooth brushing and dental control visits (p < 0.0001) than the control group. Additionally, the cannabis group reported a significantly higher consumption of sugarcontaining beverages than the control group (p = 0.0078). To obtain more objective data relations, the DS values of male cannabis users were also compared with those of Swiss military recruits found in another study. The
cannabis users had more caries on smooth surfaces than the military recruits. Although comparison with epidemiological
data suggested that the prevalence of caries on smooth surfaces is elevated in cannabis users, DFS data indicated that cannabis users do not have an increased risk of caries. Lifestyle combined with short-term hyposalivation
after delta-9-tetrahydrocannabinol consumption is the most probable cause of the high prevalence of caries on smooth surfaces in cannabis users. Further studies are needed to
investigate the effects of cannabis use on oral health.