Relevance. The properties of shape memory, superelasticity and plasticity in nickel-titanium tools make the visual prediction of breakage as difficult as possible. Therefore, an important role is given to research, the purpose of which is to predict the time of their work and to identify the main factors affecting the probability of a fracture.

Aim. Comparison of cyclic fatigue resistance of Ni-Ti rotary endodontic instruments of various manufacturers.

Materials and methods. The influence of the autoclaving procedure and the angle of bending of the root canal on the resistance of a rotating endodontic instrument to cyclic loads was studied using an author's patented device that simulates the rotation of an instrument in a real channel; the number of cycles completed by each instrument before its fracture was recorded. The morphology of fractures, the microstructure of specimens under fractures, and the microhardness of specimens of endodontic instruments after testing were studied.

Results. It has been established that resistance to fatigue fractures of instruments of various endodontic systems decreases with an increase in the bending angle of the root canal. For Endostar E3 Basic Rotary System tools, the number of cycles decreased by 1.2 times, for Protaper Universal tools by 2.9 times. The tools of the Protaper Next system reduced the number of cycles at a bending angle of the artificial root canal of 60 degrees by 1.5 times compared with the number of cycles at a bending angle of 45 degrees. At the same time, statistical data and the study of the microstructure of samples of new and past 6 cycles of autoclave tools did not show a connection between the autoclaving procedure and a decrease in their resistance to cyclic loads.

Conclusions. When working in complex bent over 45 degrees channels, it is rational to choose an endodontic instrument that has undergone heat treatment at the production stage (in the framework of this study, it was Protaper Next 25/06 M-Wire alloy). This will reduce the likelihood of a file fracture and associated dangerous complications of endodontic treatment.

Aim. To evaluate the effectiveness of prepolymerization heating of composite filling materials.

Materials and methods. For the study, two composite filling materials Enamel plus HRi® dentin and enamel were used. During the tests, the coefficient of linear thermal expansion, glass transition temperature, Young's modulus and penetration depth, electron scanning microscopy were determined.

Results. According to the results of the study, the difference between heated and unheated dentin samples in terms of Young's modulus, as well as changes in the penetration depth in the samples of the original enamel and enamel after heating, was revealed.

Conclusions. In the course of the work, it was found that the material that underwent preliminary heat treatment is much less deformed under load than the material that does not have a thermal history.

Compliance with the algorithms of endodontic treatment in most cases ensures the quality of treatment. However, real, long-term and sometimes immediate results that occur in clinical practice are not always successful. In general, the main reason for the unfavorable outcome of dental treatment is an incomplete sanitation of the root canal system. Modern publications by J. F. Siqueira, I. N. Rocas, and D. Ricucci (2019) note that many issues of endodontic treatment are unresolved. It follows that improving the quality of endodontic treatment is still relevant.

Aim. To compare two systems of instruments for root canal preparation with different types of rotation.

Materials and methods. To identify a tool that will increase the efficiency of root canal preparation, taking into account their anatomy using CBCT, 24 teeth were removed, taken according to orthodontic or pristidintic indications, without previous endodontic treatment. Among them there were 2 incisors, 1 canine, 6 premolars, 15 molars. In total, 60 canals were examined.

Results. The shape changes throughout the canal, turning into a round, oval, slit-like, complementing the configuration by the isthmuses between the canals in 13.3% of cases. WaveOne Gold showed a change in cross-sectional shape after preparation, while ProTaper Universal retained a rounded section of 6.67% after preparation of the slit-like channels.

Conclusion. Identified priority technique of root canal preparation, allowing to reduce the number of instruments and, as a consequence, the possibility of technological failures in the root canal to reduce machining of the mouth of the channel, retaining dentine playing a major role in the further prosthesis and positive prediction of remote results.

The success of endodontic treatment depends on many factors. The most important of them are the knowledge and manual skills of the dentist.

Materials and methods. We analyzed the condition of teeth after endodontic treatment in 300 patients aged 20 to 70 years. Were studied 300 images of CBCT, the number of treated teeth and the number of cases of unsuccessful endodontic treatment was analyzed.

Results. According to CBCT data, high-quality obturation of the root canal system was observed in 1335 (75%) endodontically treated teeth. The reasons for successful endodontic treatment are under-sealing of the root canal (16%), removal of material beyond the apex (5.6%), and missed root canals (3.4%).

Conclusion. Clinical dental patient examination revealed that maxillary and mandibular molars most often undergo endodontic treatment.

Aim. Optimization of an endodontic retreatment by performing the following tasks, including the selection of an optimal and safe solvent.

Materials and methods. In order to choose the most suitable solvent for the problem, an experiment was conducted with clove, mint, eucalyptus, orange, and grapefruit oils. The surface tension coefficient was measured by the Rebinder apparatus. In order to justify the choice of an effective essential oil, as well as the dissolving ability and the absence of solvent and debris after irrigation with sodium hypochlorite in the root canal, a tube-shaped electron scanning microscopy was performed.

Results. Grapefruit oil has the most dissolving activity (p < 0.05). In addition to the solubility of the filler and siller, grapefruit essential oil is able to dissolve the smear layer.

Conclusion. Optimization of the endodontic retreatment with root canals previously filled with gutta-percha, is possible using essential oils, however, a grapefruit oil is the most effective.

Study of the dynamics of blood parameters in the disease of the oral mucosa in patients with extraoral oncopathology.

Aim. To study the changes in the indicators of the General blood test in patients with diseases of the oral mucosa on the background of cancer.

Materials and metods. To perform the study on the basis of the hospitals of THE Nizhny Novgorod regional clinical Oncology dispensary, a survey of the dental status of patients with cancer of various localization was carried out. The study groups included patients compared by age, sex, concomitant dental diseases in remission. The criteria for exclusion from the examination were cancer patients receiving chemotherapy and radiation therapy, patients who refused to participate in the examination and patients with stage 1 and 4 cancer. All subjects underwent a clinical blood test with further investigation.

Results. The study included 66 women. There were changes in certain blood parameters depending on localization of the pathology and nosology of dental disease, namely, hematocrit, hemoglobin, the average volume of erythrocytes, the average concentration of hemoglobin in erythrocyte mass, mean content of hemoglobin in a single erythrocyte, the relative width of the distribution of erythrocyte volume, the absolute content of lymphocytes.

Conclusions. The study revealed the presence of signs of the initial stage of anemia, which occurs against the background of malignant education.

Calcium hydroxide is widely used as a interappointment root canal filling material due to its favorable alkaline effect. It is assumed that the action occurs from the diffusion of hydroxyl ions through the apical foramen. The aim of this article was to review studies of the various properties of pure calcium hydroxide, as well as its commercial analogues.

The review gives a contemporary notion about vital pulp minimally invasive diagnosis of temporary and permanent teeth. The latest information in Russian and foreign articles concerning new diagnostic methods that were proposed to increase diagnostic reliability is given in present review. The authors analysed advantages and disadvantages of diagnostic tools, studied their clinical effectiveness and made a conclusion about the possibility of predicting the status of pulses in the long term.

Internal resorption is a separate category of diseases of hard tissues of teeth, characterized by the loss of dentine as a result of activation and activity of osteoclasts. The article discuss issues concerning etiology, the prevalence of internal resorption, its diagnosis, emphasise the contribution of computed tomography in the diagnosis and prediction of treatment success, clinical decisions and therapeutic treatment of this disease. Describe modern endodontic treatment methods, including the use of magnification, ultrasound in endodontic treatment, the use of certain materials for temporary and permanent root canal filling. Under these conditions, the prognosis of conservative treatment of internal resorption of dental hard tissues is improved, even if there is a perforation of the walls of the tooth cavity.

Clinicians often have to deal with severely destroyed teeth. One of the keys to long-term success of the prosthetic restorations is the presence of "ferrule" effect. This case report describes how а proper ferrule effect of tooth 2.5 was achieved with the rapid orthodontic extrusion and restored with ceramic-layered zirconium.

Internal tooth discoloration is a problem in aesthetic restorations in the anterior maxilla, which requires analysis of many causative factors, assessment of restoration possibilities, as well as aesthetics of soft tissues, including the position of the lips with regards to a smile and the often encountered blue gum zenith. This article presents a clinical case in which an aesthetic direct restoration of the maxillary incisors was performed as an alternative to prosthodontic treatment after drawing up a treatment plan and determining indications.

Dental morbidity is an acute and urgent problem among children and young people with disabilities. This category of the population is deprived of proper prevention and timely treatment. A volunteer movement, «DobroDent», has been created in the Ivanovo Region, promoting a healthy lifestyle and the prevention of dental diseases. The aim of the study was to optimize measures to increase the level of prevention of dental morbidity in children and adults, including those with disabilities (HIA). On the basis of specialized and general educational, medical institutions, the monitoring of the indicators of the oral cavity of 446 children and adolescents aged 12 and 15 years was carried out using subjective and objective methods recommended by ERO-FDI-WHO experts in dentistry. The insufficient level of dental education of children is confirmed by unsatisfactory indicators of dental status. Volunteers have sufficient information and technical resources to carry out their activities to stabilize the local dental situation.

In dentistry, the method of laser flowmetry (LDF) is used to assess the microcirculatory changes of the oral cavity in normal and pathological conditions. This method is simple and atraumatic, which allows us to quickly and reliably carry out functional diagnostics. LDF is also widely used in related disciplines. The purpose of this review is to assess the microcirculation of intact periodontal tissues in children.

Aim. To assess the significance of dental fluorosis for public health using the CFI index.

Materials and metods. Dental fluorosis was evaluated in 622 students of 12.15 years old according to the WHO methodology and CFI was calculated for four settlements of the Tver region.

Results. The average prevalence of dental fluorosis was 36.5% with variability in the values of groups of schoolchildren from 5.2% to 66.7%. The significance of dental fluorosis for public health ranged from “negative” to “medium” (CFI 0.1–1.2) in the settlements of the region, from “insignificant” to “medium” (CFI 0.7–1.7) in city Tver.

Conclusions. When planning measures to prevent dental fluorosis in children in the Tver region, it is recommended that CFI indicators be taken into account.

Aim. Is to evaluate the dental status of students studying at the Dental Faculty of FSBEI HE PRMU MOH of the Ministry of Health of the Russian Federation and to identify its effect on the psycho-emotional state.

Materials and metods. The study involved 500 students of the Faculty of Dentistry FSBEI HE PRMU of the Ministry of Health of the Russian Federation. All subjects, in accordance with the index of the OHI-S index, were divided into three groups depending on the index of cavity hygiene: the first group, the OHI-S index was less than 0.7 points (good level of oral hygiene) – group 1A-in it included 125 Russian students (50%), group 1B-95 of foreign students (38%); The 2nd group, the OHI-S indicator is from 0.8 to 1.6 points (a satisfactory level of oral hygiene) – group 2A – it includes 80 Russian students (32%), group 2B – it includes 65 foreign students (26%); Group 3: the OHI-S indicator is more than 1.7 points (unsatisfactory index of oral hygiene) – group 3A – it included 45 Russian students (18%), group 3B – it included 90 foreign students (36%). The prevalence and intensity of the carious process was evaluated using the DMF index, the oral hygiene was assessed using the OHI-S index according to J. Green, J. Vermillion, the periodontal tissue condition was assessed using the CPI index (complex periodontal index), and Kechka bleeding index. The following tests were used to assess the psychoemotional status: Spilberger-Hanin anxiety test, HAM test, suggestibility and stress tolerance test. To assess the results and conduct comparative characteristics, we used the analysis of variance, the Biostat program, and also the Microsoft Excel software product using the Student criterion.

Results. The prevalence of dental caries is 98%. The average rate of tooth decay in Russian students was 5.8 ± 0.23, and in foreign students 7.6 ± 0.3. A study of the CPI index revealed with a satisfactory level of hygiene: mild periodontal tissue lesions in 28% of Russian students, 4% have a medium periodontal lesion, 18% of foreign students have a mild periodontal tissue lesion, 6% have an average periodontal lesion; with an unsatisfactory level of hygiene, 16% of Russian students have an average degree of periodontal damage and 2% have a severe periodontal disease, 32% of foreign students have an average periodontal disease and 4% have a severe periodontal disease. Analysis of the HAM test showed a decrease in the number of foreign students by the 5th year of study with a high level of well-being, for Russian students by the 5th year of study, the average level of well-being, activity and mood was characteristic. A low level was characteristic of 2nd year students of the Russian and foreign departments.

Conclusions. A study of the psychoemotional state of students at a medical university revealed a high level of activity, well-being and mood among students of the Russian department and average rates among students of a foreign department, which is explained by low oral hygiene and high caries intensity, a change in climatic conditions and place of residence, a change in diet, emotional and physical overload.