The proposed trial is fouble-blinded and involves children 11-12 years of age who shall be assigned randomly to two test groups(TiF4 and APF) and one placebo-control group. The selected study site must be stable, have a high prevalence of dental caries, have less than 0.4 ppm F in the drinking water and have a low level of dental care. The sample size will be estimated according to the increment of dental caries in that particular population, the variance, the expected magnitude of the difference, and the attrition rate. Treatments are to be given at the initiation of the study and every six months thereafter for a period of two years. DMFS clinical data will be obtained immediately prior to initiation of treatments, and at 12 and 24 month intervals.