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Background. The vast majority of malignant neoplasms of the oral mucosa refer to squamous cell carcinomas. The development of squamous cell carcinoma of the oral mucosa is often promoted by previous potentially malignant diseases, with oral leukoplakia dominating among them.Objective. To determine the clinical significance of the pathogenicity of somatic mutations in oral mucosal leukoplakia.Methods. The study material included 24 samples of abnormal epithelium of the oral mucosa from leukoplakia patients. QIAamp DNA FFPE Tissue Kit (Qiagen, Germany) was used for deoxyribonucleic acid (DNA) extraction from the samples. DNA sequencing was performed using IlluminaNextSeq 550 sequencer and TruSight™ Oncology 500 DNA Kit For Use with NextSeq (Illumina, USA). All DNA extractions from biological samples, preparation and sequencing of DNA libraries were performed step-by-step in strict accordance with the guidelines provided with the respective reagent kits. Bioinformatics analysis was carried out using specific software Illumina Base Space (Illumina, USA) and Galaxy Project (The Galaxy Community, a non-profit international project) according to current guidelines. The desired power of the study accounted for 90%. Two Proportions Z test was performed by means of The Sample Size Calculation of Statistica 12 (StatSoft, Inc.) with the set option “one-tailed hypothesis”, because it was initially assumed that pathogenic (oncogenic) genetic variants occur in the tissue of oral leukoplakia much more frequently than in the human reference genome used for sequence alignment.Results. The pathogenic somatic mutations in the TP53, KRAS, APC, NRAs and BRAF genes, identified in this study, alone or in combination, are highly likely (hazard ratio 3000-11000) to be associated with the development of oral mucosal leukoplakia and low-grade epithelial dysplasia. The multiplicity of pathogenic and likely pathogenic genetic variants associated with epithelial dysplasia, as well as the fact that a number of variants do not occur in all patients, suggests that the same histotype of oral mucosal dysplasia may develop under the influence of different mutations.Conclusion. The pathogenic and likely pathogenic variants of the TP53, KRAS, APC, NRAS and BRAF genes, identified in this study, alone or in combination, are highly likely (hazard ratio 3000–11000) to be associated with the development of leukoplakia and low-grade epithelial dysplasia.

Background. The number of studies devoted to the molecular genetics of oral mucosal leukoplakia and squamous cell carcinoma is small, while the obtained results are usually preliminary in nature. We can assume the existence of region-specific pathogenic genetic variants involved in the development of oral mucosal leukoplakia and squamous cell carcinoma. With the knowledge of such variants, it would become possible to develop PCR (polymerase chain reaction) and NGS (next-generation sequencing) test systems for the detection of clinically significant germline mutations.Objectives — to identify pathogenic germline genetic variants in patients with oral mucosal leukoplakia accompanied by grade 1 epithelial dysplasia, as well as oral mucosal squamous cell carcinoma, using new-generation sequencing.Methods. Study design: prospective, observational, cross-sectional, without a control group. The sample included patients (48 persons) of either sex (18 years of age or older) with the following proven and morphologically confirmed diagnoses: oral mucosal leukoplakia accompanied by grade 1 squamous intraepithelial neoplasia of epithelium (24 people) and oral mucosal squamous cell carcinoma (24 people), who sought medical care at the Vitebsk Regional Clinical Dental Center and Vitebsk Regional Clinical Oncological Center in 2019–2020. The identified pathogenic and presumably pathogenic genetic variants involved in the development of these diseases were quantitatively assessed. The study was conducted at the Shareable Core Facilities GENOME of the Institute of Genetics and Cytology of the National Academy of Sciences of Belarus. In order to isolate deoxyribonucleic acid (DNA) from blood samples, a QIAamp DNA FFPE Tissue Kit (Qiagen, Germany) was used. The preparation of DNA libraries and sequencing were carried out by means of an Illumina NextSeq 550 sequencing system (Illumina, Inc., USA) using an Illumina Nextera DNA Exome kit (USA). Bioinformatic analysis was conducted using Illumina BaseSpace specialized software (USA) and Galaxy Project (Galaxy Community, an international non-profit project) in accordance with current guidelines. The obtained data were statistically processed employing specialized software packages Statistica 12 (StatSoft, Inc., USA) and MedCalc 18.9.1 (MedCalc Software, Ltd, Belgium).Results. Next-generation whole-exome sequencing of deoxyribonucleic acid samples isolated from the blood of patients with oral mucosal leukoplakia and squamous cell carcinoma has been conducted in the Republic of Belarus for the first time. The total number of unique germline genetic variants in the exome of both groups of patients was shown to be very high, yet most of them were not pathogenic. In the examined patients, the majority of germline mutations were found to be localized only in 19 exome genes: MAP2K3, DNAH5, HSPG2, OBSCN, SYNE1, HLA-DRB1, HLA-DQA1, HLA-DQB1, HLA-A, HLA-B, PKD1L2, TTN, AHNAK2, PDE4DIP, MUC3A, MUC4, MUC12, MUC16, and MUC17. In both clinical groups, the greatest number of genetic variants (> 40% of the total number) was detected in MUC3A, MUC4, MUC12, and MUC16, responsible for the synthesis of the glycoprotein mucin family.Conclusion. Oral mucosal leukoplakia and squamous cell carcinoma can arise from the pathogenic variants of MUC3A, MUC4, MUC12, and MUC16.

Musculoskeletal system disorders is one of the priority directions in dentistry. They can manifest as Kosten's syndrome, snapping jaw, painful dysfunction syndrome, increased tooth abrasion, splits, breaks, pain and spasms in muscles, etc. The study set the following objectives: to develop an algorithm for analyzing the movement pattern of the muscular-articular system by developing an algorithm for recording, analyzing, filtering and processing multichannel electromyograms of the maxillofacial muscles. Analysis of the proposed algorithm for processing multichannel electromyograms showed that 7.2 % of multichannel electromyograms could not be analyzed due to patients' violations of the movement algorithm; 8.7 % of electromyogram checkpoint values were corrected. The group without dysfunctions of the temporomandibular joint is characterized by the prevalence of the relaxation coefficient of the left temporal muscle over the coefficient of the right muscle. The dysfunctioned group has the opposite result. The value of the compression ratio of the temporal muscles exceeding 2.5 is typical for the group with dysfunctions of the temporomandibular joint. The studied groups differ as much as possible when analyzing the relaxation coefficients of the temporal muscles. When analyzing this coefficient, it was possible to truly determine the presence or absence of violations in 50 %, falsely – in 16 % of cases. The coefficient of relaxation of the masticatory muscles made it possible to obtain a true state of 24 %, a false one – in 8 %. We concluded that the compression ratio is less suitable for separating patients with and without dysfunction of the temporomandibular joint.

The results of experimental studies, the purpose of which was to study the effect of low-intensity pulsed ultrasound on the wettability of the surface of titanium dental implants are described. We studied 64 titanium dental implants. The control group consisted of 32 dental implants without ultra-sonication. The experimental group consisted of 32 dental implants, which were exposed to low-intensity pulsed ultrasound. Studies using low-intensity pulsed ultrasound showed that the wettability of the surface of all the experimental samples (32 dental implant) was 100 %, and the wettability of control samples (32 dental implant) was not observed. Thus the previously unknown property of low intensity pulsed ultrasound enabling the wetting of entire surface of the dental implant was discovered.

Aim. This research was conducted to study the type of clinical changes in the diseased periodontal tissues by means of using mesenchymal stem cells for treating gingival recession in the experiment.Materials and methods. Adipose tissue in a volume of 1-2 ml was sampled from one specimen in sterile conditions in order to obtain allogeneic mesenchymal stem cells before the beginning of the experimental studies. Random-bred female white rats (60 specimens) were used as a model in the experiment. The surgical intervention was performed in the area of incisors on the upper and lower jaws of rats. All animals were divided into 5 groups (10 rats in each group) depending on the planned method of the treatment. The control group, intact rats, consisted of 10 laboratory animals with a healthy gingiva. The creation of a model of the experimental gingival recession was carried out by the mechanical V-shaped excision of periodontal tissues.Results. The experimental studies showed the possibility of complete regeneration of the dentogingival papillae as well as periodontal tissues regeneration in the area of the experimental gingival recession during the first 28 days. Meanwhile, there is a complete absence of inflammatory signs in the 5th group (hyperemia, edema, gingival bleeding), along with their significant decrease in the 3rd and the 4th groups that confirms the pronounced therapeutic effect of mesenchymal stem cells and sterile bioplastic collagen material «Collost» (7% gel).The conclusion. While studying the type of clinical changes in diseased periodontal tissues using mesenchymal stem cells in the treatment of gingival recession, we established the positive dynamics in the experiment. The decrease in the intensity and prevalence of gingival inflammation starts from the 14th day. On the 28th day there was noted a complete absence of inflammatory signs in the animals after injecting the transplant consisting of the cell suspension on the sterile bioplastic material Collost (7% gel). Furthermore, the significant increase in the regeneration of the gingival margin was observed on the 24th day from the moment of creating the gingival recession model. The complete regeneration of the dentogingival papillae and the absence of the gingival recession were noted on the 38th day of general observation.

Aim. The research was conducted to develop and implement the complex of diagnostic activities in patients with dysfunction of temporomandibular joints with signs of bruxism.Materials and methods. To achieve this aim we conducted a comprehensive diagnosis of 61 patients aged 20-29 years with bruxism and temporomandibular joints dysfunction (TMJD), the patients were divided into two groups. To diagnose and analyze the results of the disease treatment in patients we used a computer analysis with visualization of changes of the osteoarticular surface and parameters of the joint gap in the TMJ. Depending on the ratio of prognostic risk criteria and the development of bruxism, we distinguished the area of low, medium and high level of risk of disease progression.Results. Comparison of the treatment results of patients with bruxism from two groups in 12-24 months showed that patients from the second group had good treatment results. Patients of the second group underwent a complex of diagnostic activities and its data increased the treatment effectiveness. The results obtained from the treatment of patients from the first group indicate the lack of data from the standard examination of patients with bruxism.Conclusion. The developed complex diagnostic activities in patients with bruxism in combination with dysfunction of the TMJ and occlusive attrition of teeth allow to assess not only the local status but also to determine the functional state of dentoalveolar system and the cerebral cortex which affects the amount of therapeutic activities in the patient.

A method of treating fully edentulous mandible with removable designs of dentures relying on dental implants is described. Data from the literature over the past 10 years is studied. After learning deficiencies a new method for fixing the total denture mandible implant is proposed. This method will increase the effectiveness of treatment fully edentulous mandible.

The device for laser-optical diagnostics (LODdsf) in dentistry. The use LODdsf for the functional estimation of periodontal diseases is proved. Sensitivity and high information LODdsf provided an opportunity to evaluate differentiated initial preclinical stage of the inflammatory process in all topographic zones of the gums, which determined the timely assignment of corrective therapy.

The article presents the results of the treatment of patients suffering from temporomandibular joint dysfunction with the use of the newly developed method of puncture vacuum-darsonvalization. Comprehensive treatment received 66 patients of 2 clinical groups. Objective evaluation of clinical data, as well as the dynamics of the recovery of the TMJ function were made based on the analysis of survey data, clinical examination and study of objective research methods developed by us with the inclusion of prognostic signs. The aim of the study was to improve the results of treatment of patients with TMJ disorder by analyzing prognostic markers and use of individual dental splints with puncture using vacuum-darsonvalization. The results of applied treatments of TMJ disfunctions using developed method of puncture vacuum-darsonvalization showed to be the most effective, allowing to obtain 97.1% of good results in long-term period.