 Statistical methods All data are processed with the IBM-SPSS software version 19.0, Chicago IL, USA. The categorical data are subjected chi-square tests. Continuous measurements will be calculated with aid of non-parametric tests. The caries incidence is calculated as the difference in dmfsdmft between follow-up and baseline. Comparisons are carried out between the study groups at baseline and at the follow-ups. The group concealment will not be unveiled until after the statistical calculations. A p value less than 0.05 is considered as statistically significant. 