Objective:To analyze the stress–strain states of bone and abutment teeth during the use of different prosthetic designs of fixed partial dentures with the use of relevant mathematical modeling principles.Materials and Methods:The use of Comsol Multiphysics 3.5 (Comsol AB, Sweden) software during the mathematical modeling of stress–strain states provided numerical data for analytical interpretation in three different clinical scenarios with fixed dentures and different abutment teeth and demountable prosthetic denture with the saddle-shaped intermediate part.Statistical Analysis Used:Microsoft Excel Software (Microsoft Office 2017) helped to evaluate absolute mistakes of stress and strain parameters of each abutment tooth during three modeled scenarios and normal condition and to summarize data into the forms of tables.Results:In comparison with the fixed prosthetic denture supported by the canine, first premolar, and third molar, stresses at the same abutment teeth with the use of demountable denture with the saddle-shaped intermediate part decreased: at the mesial abutment tooth by 2.8 times, at distal crown by 6.1 times, and at the intermediate part by 11.1 times, respectively, the deformation level decreased by 3.1, 1.9, and 1.4 times at each area.Conclusions:The methods of mathematical modeling proved that complications during the use of fixed partial dentures based on the overload effect of the abutment teeth and caused by the deformation process inside the intermediate section of prosthetic construction.

The purpose of the work was to study the activity of the carious process in people of different ages using the assessment of the Decayed, Missing, and Filled Teeth and the International Caries Detection and Assessment System index. Materials and methods. The study involved 53 people who were divided into groups: group 1 – 16 people aged 18 to 25 years, group 2 – 20 people aged 26 to 35 years and group 3 – 17 people aged 36 to 45 years. The intensity of caries was determined using the Decayed, Missing, and Filled Teeth index. The International Caries Detection and Assessment System index was used to assess the activity of carious lesions. Results. The indicators of the Decayed, Missing, and Filled Teeth index in the group of people aged 18-25 years significantly differed (p <0.05) from the indicators in the group of people aged 26-45 years. In the group of people aged 36-45 years the indicators were higher than in the group of people aged 26-45 years, but no significant difference (p˃0.05) was found. In the group of people aged 18-25 years the share of filled teeth was 61.5%, teeth affected by caries were found in 29.4%, and removed teeth – in 9.1%. In the group of people aged 26-45 years, the rate of filled teeth was lower compared to people of the 1st group, the share of carious teeth increased up to 35.0%, and the number of removed teeth increased up to 16.4%. In the group of people aged 36-45 years the share of teeth affected by caries was lower than in the 1st and 2nd groups and was equal to 27.3%, the share of filled teeth was 46.2%, which is lower than in other groups, but the share of removed teeth was the highest of the groups which were examined and was 26.5%. The results indicate a rapid increase in the intensity of caries in patients of main working age, namely persons of the 2nd and 3rd groups compared with persons of young working age of the 1st group. The study of the depth of caries in enamel and dentin according to the International Caries Detection and Assessment System showed that in patients aged 18-25 years, from all teeth which are affected by caries in 71.4% enamel caries was found, which averaged 1.81 ± 0.2 teeth and in 28.6% – dentin lesions, which was an average of 0.68 ± 0.2. In patients aged 26-35 years, codes 1-3 accounted for 41.0% of affected teeth (mean 2.05 ± 0.1 teeth) and code 4-6 accounted for 59.0% of affected teeth (average 2.95 ± 0.2 teeth). In patients of the oldest age group, the number of teeth affected by caries with a code of 1-3 was 27.9% (average of 1.12 ± 0.1 teeth) and with a code of 4-6 was 72.1% (average of 2.88 ± 0.2 teeth). Conclusion. As the age of patients increases, the proportion of filled teeth decreases, but the proportion of removed teeth increases. The highest percentage of teeth affected by caries was found in the 3rd group. As the age of patients increases, both the average number of carious teeth and the number of teeth with damage dentin increase