Convenient sampling consisted of: 153 schoolchildren in the experiment group (chewing xylitol gum) and 147 schoolchildren in the control group (no chewing gum). All subjects were student at primary school Nguyen Van Tran, Binh Chanh, HoChiMinh city (non-fluoridated area) with high caries prevalence (DMFT + dmft ≥ 3).