Summary. Caries is the most common dental disease originating from the ancient past and nowadays it is a considerable issue of pediatric dentistry (1,2). The WHO estimates approximately 15 % of children in their second year of life are already teeth afflicted by caries. This indicator increases with age and in the period of changeable occlusion it can reach 90 % depending on the territory where children reside. Investigation of caries indicators in children during the period of changeable occlusion is an important issue since eruption of the first permanent molars occurs, which are poorly mineralized, and have a specific relief of the masticatory surface (8). At this period of age children are often ill and do not thoroughly take care of their oral cavities (9,10,12).The aim of the study – to learn caries in children at the first period of changeable occlusion. Materials and Methods. In general 134 children aged from 7 to 9 during the 1st period of changeable occlusion were examined. The comparative group included children examined in Poltava during the period of 1997–1998. The results obtained were processed by means of variation statistics method.Results and Discussion. Comparative characteristics of caries indices was performed in the period of 1997–1998 (3,4) at the age periods of 7, 8 and 9 years which corresponds to the first period of changeable occlusion. 82.22 % of 8-year-old children were diagnosed to suffer from caries of temporary teeth. 14 examined children (31.11±6.98) % had caries of the permanent teeth, including 13 of them with caries of temporary teeth (92.86±7.14) %. An important fact was revealed that only in 2 (14.3±9.71) % children out of 14 permanent teeth were filled during preventive examination at the dentist. The rest 12 children were unaware of caries in their permanent teeth: carious cavities were small, toothache was absent; mastication surfaces were not accessible for careful examination by a child or parents; a dentist examination was more than half a year ago. All these factors should be considered while performing sanitary-educational and preventive work by a pediatric dentist.Conclusions. The analysis of caries index of the temporary and permanent teeth in children during the first period of changeable occlusion (7–9 years of age) in Poltava during the period of investigation in 1997–1998 and 20 later (2017) determined certain differences. A considerable attention should be paid to the indices of occurrence and intensity of caries in 8-year-old children. They are rather higher in 2017 as compared to1997–1998. The data concerning the condition of the dental hard tissues of the permanent teeth in children nowadays are especially alarming. They appeared to be considerably higher than 20 years ago. It requires more detailed investigation of the affecting factors as well as the attitude of children and their parents to dental health care, since the system of work of dentists in Poltava schools is maintained which is an important thing from the point of view of prevention of dental diseases and timely oral sanitation (8,11).