Background: Since the radionuclides concentration in teeth is a good indicator of the human body’s radioactive contamination, the purpose of this study was to measure the track density of alpha particles emitted from the human teeth and to assess the resulting cancer risk. Material and Methods: In this cross-section study, 93 permanent and unfilled tooth samples were collected from the patients residing in Khorramabad, Iran, and visiting dental clinics in this city. The alpha track density for the tooth samples was measured using CR-39 nuclear track detector. Annual effective dose (AED) and excess lifetime cancer risk (ELCR) were estimated based on the recommendations made by ICRP and UNSCEAR. Results: The mean alpha track density from ²²²Rn in patients’ teeth was410.15 tracks cm^-2, whereas the mean for women and men equaled 441.42 and 378.20, respectively. This difference was not statistically significant (P=0.22), but there was a statistically significant difference between the track densities in different age groups (P˂0.001).In this study, the average radon activity concentration was 40.62 Bq m^-3. Also, the mean annual effective dose and the mean ELCR were calculated as 1.02 mSvy^-1 and 3.59 ×10^-3, respectively. Conclusion: The AED value was higher than the permissible dose limit and also the mean ELCR was higher than the global average. Based on the results, it is necessary to perform periodical monitoring to detect pollution sources.