Objective. The cause of considerable elasticity and plasticity of human dentin is discussed in the relationship with its microstructure. Methods. Structural state of teenage and mature human dentin is examined by using XRD and TEM techniques, and their deformation behavior under compression is studied as well. Result. XRD study has shown that crystallographic type of calcium hydroxyapatite in human dentin (calcium hydrogen phosphate hydroxide Ca9HPO4(PO4)5OH; Space Group P63/m (176); a = 9,441 A; c = 6,881 A; c/a = 0,729; Crystallite (Scherrer) 200 A) is the same for these age groups. In both cases, dentin matrix is X-ray amorphous. According to TEM examination, there are amorphous and ultrafine grain phases in teenage and mature dentin. Mature dentin is stronger on about 20% than teenage dentin, while teenage dentin is more elastic on about 20% but is less plastic on about 15% than mature dentin. Conclusion. The amorphous phase is dominant in teenage dentin, whereas the ultrafine grain phase becomes dominant in mature dentin. Mechanical properties of human dentin under compression depend on its structural state, too.

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During the course of this experimental study tomograms of extracted teeth were analyzed before and after filling the root canals with an endodontic material and fragments of broken metal instruments for root canal treatment. During the first stage of the experiment, untreated extracted teeth were scanned using conebeam computed tomography and microfocus cone-beam computed tomography. A comparative assessment of capabilities of the two methods of cone-beam computed tomography based on examination of untreated root canals was carried out. The second part of the study is dedicated to visualization of root canals that contain foreign high-density materials.

The structure features of primary tooth hard tissues were studied at teenage, person of young age and patient’s age from 20 to 50 years by means of methods using in physical material science (metallography, x-ray analysis and transmission electron microscopy). The  findings, which agree with the results of dental volume tomography, allow determining the features of microstructure of crown and root dentin of patients at different age. On the basis of the this data the criteria of degree of formation and maturity of the root was objectified that allow variably change the endodontic treatment.

The evaluation of the distribution of complaints about manifestations of musculoskeletal fatigue in the cervical spine among dentists-therapists on the basis of the survey data. Through photogoniometer research method the evaluation of working posture of specialists depending on the magnification system used was carried out.