Purpose was to study the effect of professionally applied topical fluoride on oral health status on the population level in adolescents with lower socio-economic status. Adolescents attending dental clinics where professional fluoride application is a routine procedure (high-fluoride group) were compared to adolescents from other clinics (low-fluoride group). The study consisted of a questionnaire, a clinical examination with two bitewing radiographs. X-rays showed no statistically significant differences in the number of DS, FS or DFS. Clinically, there were no statistically significant differences in the number of FS or in the number of DFS. The low-fluoride group had a statistically significant higher number of DS than the high-fluoride group. The results suggest that professionally applied fluoride has a limited effect on caries and treatment experience in a population. These results justify a randomised clinical trial to study the effectiveness of professionally applied topical fluorides.