Introduction. The risk for active tuberculosis (TB) infection among dental healthcare workers (DHCWs) is controversial. Specifically, TB incidence is generally low among general dental practitioners, but it is higher than in the general population among hospital/prison dentists, DHCWs who work in endemic areas, students during clinical training with direct patient contact. Aim. To investigate prevalence of reactive tuberculin skin test (TST) among dental students and DHCWs in an Italian dental university hospital. Material and methods. DHCWs (n=76), dental (n=92) and dental hygienist (n=13) students, administrative staff (n=15, reference group), who were not previously vaccinated against TB, provided their consent to undergo the Mantoux test, the standard recommended TST. Unadjusted and adjusted odds ratios (ORs) of reactive TST for working categories and for years of practice in the dental hospital were assessed through logistic regression analysis. Results. Prevalence of reactive TST estimates were 0.0%, 17% (95% confidence interval, 95CI, 11-26%), 20% (95CI, 12-30%) and 7% (95CI, 1-30%) among dental hygienist students, dental students, dental healthcare workers and administrative staff, respectively. The adjusted ORs for working categories were non-significant, but they were significant at 95% level for the years of exposure (OR, 1.09 for each year of practice at the hospital; 95CI, 1.01-1.19). Conclusion. High prevalence values could be due to cross immunization from non-tubercular mycobacteria, frequently found in dental unit waterlines, or boosting from repeated TST occasions. However, these data suggest that the risk for TST conversion is associated with the years of practice in dental hospitals.