Relevance. Paediatric dentistry is a branch of medicine that provides oral health care for children from birth to 18 years. Prevention should be the primary task of paediatric dentists. Everyone knows that preventing a disease is much easier and more cost-saving compared with its diagnosis and treatment. Therefore, the modern dental field is extensively engaged in the prevention of dental diseases.
 There are many etiological factors, which can cause the carious process, namely: endogenous or general (poor nutrition, low fluoride content in drinking water, the state of the child's overall health, adverse environmental living conditions, genetic predisposition, etc.) and exogenous, or local (poor oral hygiene, excessive use of refined carbohydrates, changes in the composition and properties of oral fluid (saliva), reduced resistance of dental tissues, insufficient functional load of the maxillofacial system, etc.).
 Therefore, special attention should be focused on oral hygiene in children who are especially prone to respiratory infections, since a combination of factors of various nature can often lead to lesions of the hard dental tissues.
 Purpose of this study is to investigate the Green-Vermilion hygiene index in children who are frequently infected with SARS in 5 years following their undergoing treatment and prevention measures.
 Materials and methods. 80 children aged 11-12 years who were under the medical observation 5 years ago are examined and divided into 4 groups. Group 1 includes healthy children (they had SARS 1-2 times a year) and groups 2, 3 and 4 are formed with children who have confirmed respiratory viral infections 3 – 4 times a year.
 Results. During the first examination, the Green-Vermilion hygiene index in children of groups 2, 3 and 4 was unsatisfactory, in contrast to the children of group 1, who demonstrated satisfactory values of the respective index.
 A year following the first examination (participants receive prophylactic complexes twice); we repeatedly determined Green-Vermilion hygiene index and found a deterioration of the studied indicator in all observation groups. The best findings were detected in the healthy children of group 1, who used recommended hygiene products, but they also showed a slight deterioration. Among the participants, who have frequent SARS cases, the best results were found in the children of 4th group and equalled was 1.83±0.16 points. The children of this group strictly followed the prevention complex we recommended. The hygiene index, 1.86±0.18 points, was somewhat worse in children of the 3rd group who used the already known medical and preventive complexes aimed at increasing the resistance of the hard tissues of the teeth. The index of 1.95±0.18 points was detected in the children of group 2nd, who were only prescribed to follow common oral hygiene, and this hygienic index value was the worst oral hygiene index among all the examined groups with frequent SARS cases.
 The situation was almost the same during the examination, which was carried out in 2 years after the first examination. The worst hygiene indicators were observed in children of group 2 (1.89±0.17 points), who often suffer from acute respiratory viral infections and who were prescribed only common oral hygiene, and the best (1.32±0.13) in the healthy children of the 1st group.
 The last examination carried out in 5 years, demonstrated stable results, despite the time that had passed since the use of treatment and preventive measures. The investigated indicator slightly differed from 1st examination. The best Green-Vermilion hygiene index values were found in the children of group 1 (practically healthy), who were recommended to take recommended common oral hygiene. Among the groups of children suffering from acute respiratory viral infections, the best results (satisfactory), 1.79±0.18 points, were revealed in the children of 4th groups who took the prevention complex we proposed. In children of the 2nd and 3rd groups, the hygiene indices were 1.84±0.18 points and 1.81±0.17, respectively that also corresponded to an unsatisfactory state of oral hygiene.
 Conclusion. The results obtained have shown the dynamics of hygiene indicators in children of the examined groups almost did not change; somatically healthy children demonstrate better hygiene indicators than children who are frequent SARS cases. Children of the 4th group, who were treated with the treatment and prophylactic complex we developed, have the best Green-Vermilion hygiene index values among frequently ill children. This can be explained by the fact that during these 5 years children periodically took our complex.