RATIONALE: As the trace element strontium (Sr) plays a significant role in dental health, it is important to determine the Sr concentration and isotope composition (Sr-87/Sr-86) of teeth and whether these values are related to caries formation, age and sex. METHODS: A total of 160 permanent teeth were collected from 7- to 79-year-old people from the southern Shaanxi area of China, including 100 healthy teeth and 60 carious teeth (men and women each accounted for half of the samples). The concentration and isotope composition of Sr elements in the dental enamel of the teeth were measured using inductively coupled plasma mass spectrometry (ICP-MS) and thermal ionization mass spectrometry (TIMS). RESULTS: A significantly lower Sr concentration was found in the enamel of the carious teeth than in that of the healthy teeth for individuals of varying ages and sex. The Sr concentration in human carious teeth ranged between 79.70 mu g/g and 85.80 mu g/g; while the Sr concentration in healthy teeth ranged between 128 mu g/g and 156.77 mu g/g. Our results also demonstrated that the Sr-87/Sr-86 ratio did not appear to be affected by the caries formation, age or sex. The Sr-87/Sr-86 ratio in the enamel of the healthy and carious teeth of individuals of varying ages and genders ranged between 0.710935 and 0.711037, which falls into the range of Sr-87/Sr-86 ratios found in the local, naturally occurring water, soils and rocks. CONCLUSIONS: Sr plays a significant role in dental health, and there is a negative correlation between Sr and the occurrence of dental caries. The Sr-87/Sr-86 ratio of teeth reflects the Sr-87/Sr-86 ratio of the associated environment, and there is no significant relationship with the frequency of dental caries, age or sex.