In the thesis the authors present complex results of the epidemiological study of oral health of the 6 - 12-year old schoolchildren attending elementary schools in Presov [Slovakia] who participated in the Healthy Smile Prevention Project. The participants of the Project were represented by the pre-school children and schoolchildren from the age of 4 years attending the pre-school facilities and elementary schools and the project was performed by the dental hygienist, dental disease prevention officer, and school dental care assistant under supervision of a dental practitioner. The oral health of the abovementioned project participants was compared with the oral health of the group of children not participating in the prevention project. The project was supported by the Swiss company GABA.