The aim of this research is to study the influence of size and location of wedge-shaped defects of teeth on stress and strain state of restorative material on the basis of biomechanical analysis. Materials and methods: Biomechanical analysis of the stress-strain state was performed on a jaw bone fragment with canine and premolar inclusion. Results: Tangential stress increase both in the adhesive layer and in restorative material with depth and width (medial-distal size) of restored wedge-shaped defects of teeth,. The most unfavorable loading on a tooth is a joint action of vertical and horizontal loading in lingual- vestibular or vestibular-lingual direction, depending on localization of the restored wedge-shaped defects of teeth. The formation of retention grooves in wedge-shaped defects of teeth reduces the value of the maximum tangential stress in the adhesive layer of restorative material to 25% and extends the longevity of restorations. Conclusions: The difference in maximal values of tangential stress increases in adhesive layer of restorative material with or without retention grooves with increasing depth of defect. Thus, it is advisable to form retention grooves in cases of wedge-shaped teeth defects that exceed 1.5 mm. In case of restoration of subgingival wedge-shaped defects of teeth of small height it is recommended to create one retention groove on the gingival or incisal planes of a carious cavity due to significant inconveniences, and sometimes impossibility of formation of traditionally located retention grooves.

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Introduction. Tooth restorations fabricated of any material carry multiple loads in the oral cavity. The ability of restoration materials to resist the forces of shear, bending, and abrasion without losing their functional and aesthetic properties is a valuable factor on which the choice of a dentist and a patient will depend on the stage of coordinating the type and material of restoration. Objectives. Determination of the abrasion resistance of samples of dental restoration materials: light composite resin samples EsthetX (Dentsply-Sirona), feldspatic ceramics EX3 (Noritake), ceramics based on leucite glass IPS Empress Esthetic (Ivoclar Vivadent). Materials and methods. To carry out the corresponding experiment, plates 10 × 10 mm in size and 1 mm thick were prepared from the tested restoration materials. Before testing, the samples were degreased with ethyl alcohol and their density was determined by hydrostatic weighing. Samples of plates (composite or ceramic) were fixed on plates of organic glass. Abrasion of the samples was determined by 200 revolutions of the volcanic disk. At the end of the elongated shoulder of the lever suspended the load, selected so that the shoulder of the lever was in the test in a horizontal position. After testing, the samples were weighed again. Results. Ceramic based on leucite glass has the most optimal parameters from the specific gravity and abrasion resistance. structures made of this material will have a significantly lower weight compared to feldspar ceramics (apr. 43.1% lighter), and 14.2% composite resin material with the same restoration thicknesses. Conclusions. Expluatation of restorations made of leucite glass, according to the experiments, will also be a more extended due to the high abrasion resistance of leucite glass in comparison with the light curing composite resin (17.5% higher), and 77.5% higher comparing to feldspatic ceramics.

Resume. Nowadays, aesthetics plays an important role in dentistry due to the increased attention of people to the beauty and attractiveness of the smile, which is known as an effective tool in achieving both personal and professional purposes. Therefore, the whitening of discolored teeth is one of the promising directions in aesthetic dentistry. To date, there is much controversy among dentists about the effectiveness and, the most importantly, the safety of teeth whitening. The prevention of dentin hypersensitivity is among the main tasks associated with the safe and comfortable treatment and follow-up period for patients. In order to avoid the negative consequences of hyperesthesia, the teeth whitening procedure should be finished with remineralizing therapy. Thought there are a large number of techniques and products for the treatment of hyperesthesia, the question of their most appropriate selection and combination is remaining unresolved and is relevant to meet the steadily growing population demands. Purpose: to highlight the latest views on techniques and products for remineralizing therapy in the process of teeth whitening based on the analysis of relevant literature. Results. Numerous bleaching methods are mainly based on applying high concentrations of hydrogen peroxide. At present, the safety of whitening methods remains controversial and thus requiring further research. The problem of improving techniques aimed at preventing the side effects of professional whitening on the oral tissues and organs are remaining relevant. The problems associated with professional whitening include the decreased resistance of hard dental tissues, the appearance of areas of demineralization and hyperesthesia in the hard dental tissues. At present, a wide range of products has been proposed to treat and prevent the development of teeth hypersensitivity. However, the most effective of them, which could be offered to patients after professional whitening have not been identified yet. To prevent and treat dental hyperesthesia effectively, fluoride-containing remineralizing remedies are widely used to diminish dentin sensitivity. There are studies demonstrating the highest incidence of teeth hyperesthesia during light catalytic and chemical bleaching Therapeutic and prophylactic agents, which contain calcium, phosphorus and fluoride ions, which promote dental enamel remineralization, have been proposed. The use of remineralizing gels before the procedure of medical teeth whitening reduces the occurrence of dental hyperesthesia. That is why many manufacturers of bleaching systems have begun to add desensitizing components to their composition. Thus, Opalescence Boost PF gel contains potassium nitrate and fluorine, Philips Zoom whitening gel contains amorphous calcium phosphate, in addition; remineralizing gel Relief ACP with amorphous calcium phosphate is offered to reduce the occurrence of teeth hypersensitivity during whitening procedure. The results of our research have shown the most significant changes expressed by a decrease in organic acids, maximum increase in concentrations of calcium ions in oral fluid, occur when using photo-bleaching system Beyond Polus, while minimal changes are observed when using chemical activation system Opalescence Xtra Boost. The combination of a reminalizign remedies based on zinc-substituted hydroxyapatite carbonate with laser phonophoresis can be recommended be apply after any bleaching techniques and they have been proved to be the most effective. Conclusion. There is a wide range of techniques and products of remineralizing therapy applied in the process of teeth whitening. Various options of remineralizing therapy and applying different compounds reducing teeth sensitivity after teeth whitening procedure are described in the article. Many formulas have been already developed to ensure patient comfort after a whitening procedure, and in particular to prevent the development of hyperesthesia. Some manufacturers incorporate remineralizing remedies in the whitening system that allows dentists to solve the problem of teeth hypersensitivity effectively.