X-RAY SPECTRAL ANALYSIS OF DENTAL HARD TISSUE TRACE ELEMENTS (ELECTRON-MICROSCOPIC EXAMINATION).

The role of trace elements (microelements) in maintaining oral health has not been fully investigated and still remains the subject of research and discussion. Some trace elements contribute to the development of caries, while others, on the contrary, prevent formation of this process and accelerate the restoration of dental hard tissues. Penetration of trace elements into human dental structures via saliva, food, water and other routes contributes to the formation of carious diseases, or, conversely, its cessation and/or regression. Analyzing the studies allowed us to conclude that there is very scarce information available in the literature about the layered, zonal distribution of "vital" trace elements in healthy (intact) teeth dentin and enamel. However, to study the distribution of caries-static elements (Ca, F, P) on the enamel surface as well as in para-pulpal dentin is of great importance as well. It was aimed to identify trace elements in human teeth structures (enamel, dentin and cementum), as well as to determine their localization and concentration. To reach this objective, X-ray spectral analysis on 6 intact, extracted teeth has been performed by Scanning Electron Microscopy (SEM). Identification of trace elements was performed on the 6 sites/locations of these teeth: enamel surface layer, enamel thickness, enamel-dentin border, parapulpal dentin, root dentin, and cementum. As a result, it has been found that the distribution of essential trace elements in dental hard tissues is uneven, while such an important element in maintaining healthy teeth as Fluorine has been found in only minimal concentrations in hard tissues.

EVALUATION OF THREE OBTURATION TECHNIQUES IN THE APICAL PART OF ROOT CANAL.

The purpose of endodontic treatment is root canal preparation, irrigation and reliable filling. If this procedure results in quality tooth restoration, then long-term tooth function is guaranteed. All stages of the endodontic treatment process are important, but the final treatment procedure is root canal obturation, in which the dentist discusses the intended purpose. The process of root canal obturation is a time-consuming and costly manipulation. In this process, complete filling of the apical (peak) root is crucial. Therefore, the aim of this study was to determine the quality of canal filling in apical third of root using 3 techniques: lateral condensation, and thermoplastic Gutta Master and Gutta Fussion obturators. The quality of obturation was evaluated on 36 extracted human teeth. Teeth were divided into 3 groups according to the obturation technique (A, B, C study groups). In each group, the roots of the tooth were sectioned by 2 transverse cuts (perpendicular to the long axis) into 3 segments - apical, middle and coronal thirds. A scanning electron microscopic (SEM) study of apical thirds was performed. The SEM study had to identify the gap between material and root dentin, distant from the canal in all three techniques. The extent of the gap was assessed using modified criteria by R. Tanikodas (2016). The study revealed that absolutely no hermetic obturation of the canal system was recorded in any of the study groups. In all cases, microleakage of different degree and localization between the filling material and the canal wall was observed. However, the worst results were revealed in group A, where interphase weakening was the most frequent. Gutta-Master and Gutta-Fussion thermoplastic obturation showed better adhesion to the walls, but the degree of obturation in group C teeth was better than the results in specimens where the canals had been filled with Gutta-Master.

EFFICIENCY OF CHELATING IRRIGATION AGENTS FOR REMOVING A LUBRICATED DENTIN LAYER OF ROOT CANAL.

The study is aimed at investigating the smear layer, formed on the walls of dental root canals as a result of endodontic treatment, by using scanning electron microscope (SEM) and determining its removal and/or modification quality after applying water solution of 18% ethylenediaminetetraacetic acid (EDTA) and gel. 50 extracted teeth preliminary prepared using Step-Back technique has been studied. Experimental teeth were randomly divided into the following 3 groups: control group (20 teeth), study group I (15 teeth) and study group II (15 teeth), respectively, irrigated by water solution of 18% ethylenediaminetetraacetic acid (EDTA). SEM examination was carried out for 3 different areas of preliminary prepared separated dental roots: coronal, middle and apical portions. The entire study was based on the analysis of 900 electron microscope photo- images. SEM study revealed formation of the thick smear layer on the surface of root canal dentin, practically covering the openings of canal tubules. Both the water solution and/or gel of 18% ethylenediaminetetraacetic acid provided partial or complete removal of the mentioned smear layer; among them, EDTA 18% water solution appeared to be more effective for coronal and middle thirds of dental root (P<0.05). Removal of the smear layer from root canals by using the chelating agents was less effective in the apical third. Having studied these areas, the portions covered with the smear layer and blocked dentinal tubules on canal surfaces were revealed.