Pastukhova V. A., Grishyuk M. G.

CONTENTS

Scentific article

Aim of the study. The study was aimed at understanding of effects of extreme hyperthermia and dynamic physical exerts on mineral contents of bone and dentin minerals of the mandible of adult rats. Materuals and methods. The whole experiment comprised 112 adult male rats with initial body weight of 150-160 grams. The animals were separated into three groups as follows: the first group (C) comprised intact animals, the second and the third groups comprised animals that were exposed to high ambient temperature. The second group was exposed only to everyday 5-hour ambient temperature of 44-45 °C (extreme chronic hyperthermia – EH) while in the third group temperature exposure was combined with physical exerts (swimming for 15-20 minutes was chosen as exerting method, group was marked as EH+PE). Upon expiration of observation terms (1, 7, 15, 30 and 60 days) the animals were withdrawn from the experiment by means of decapitation under general anesthesia. The mandibles were excised and then separated into bony and dental tissues. The incisors were then released from enamel and cement and dentin was grounded for X-ray scatter analysis. X-ray analysis was performed by means of DRON-2 X-ray device with goniometric holder GUR-5. X-ray parameters were like the following: Kcopper radiation with wavelength of 0. 1542 m and anodic voltage and amperage of 30 kV and 20 A respectively. Diffracted X-rays were registered in angle range from 2° to 37° with recording speed of 1° per minute. Using the records we then measured the most expressed peaks and calculated dimensions of the coherent scatter blocks using Selyakov-Scherer equation and calculated microtexture coefficient using reflex ratio method. All the data obtained were analyzed by means of variation statistics using standard software. Results and discussion. Under effects of EH sizes of elementary cells of bone mineral along a-axis were higher than those of the controls by 0. 17% and sizes along c-axis were higher by 0. 19%. Sizes of crystallites in dentin were higher than those of the controls by 10. 19% and microtexture coefficient was lower by 2. 87% as compared to control values. Combined effects of EH and PE were even worse than simple EH for both bone and dentin. By the first day after HE+PE onset significant differences as compared to simple EH yet were not found. In readaptation period after combined influence, instability signs reduced to baseline values. EH+K influence on bone tissue as compared to I group values resulted in enlarged crystallites – by 4. 96% and decreased microtexture coefficient by 7. 88%. And as compared to EH group microtexture coefficient was higher by 9. 65%. In dentin, the crystallites were larger than those of K group and microtexture coefficient lower by 1. 64%. Significant differences between EH+K and EH groups were not found. Conclusions. Extreme hyperthermia during 60 days results in instability of ultrastructure of both bone and dentin of mandible. Combined action of hyperthermia and physical exerts during the same period intensified instability in ultrastructure of minerals. In readaptation period negative effects of experimental conditions reduced yet even by the end of readaptation significant changes were still found. After combined action of hyperthermia and physical exerts the affected parameters restored slower than those of EH group.

rats, mandible, bone tissue, dentine, biomineral, extreme hyperthermia

«Bulletin of problems biology and medicine» Issue 2 part 2 (108), 2014 year, 080-083 pages, index UDK 591. 471. 42:615. 37»46»