[Study on the pressure on ceramic veneers during cementation]. / Izuchenie velichiny davleniya na keramicheskie viniry vo vremya ikh tsementirovaniya.

OBJECTIVE: The aim of the study is measuring the magnitude and determining the method of finger pressure exerted by doctors on ceramic veneers during their fixation. MATERIAL AND METHODS: A simulation model was designed in order to measure the volume of finger pressure. Veneers were produced for 2 central incisors. Doctors alternately placed veneers on the model and applied pressure on them for 20 seconds simulating the clinical stage of cementing. The operator recorded the maximum readings of the scales and entered the result on the research protocol. In addition, it was recorded which finger the doctor exerts on the veneer during its cementing to ensure a tight fit: thumb or index finger. RESULTS: The values obtained during cementation of 54% doctors ranged up to 1 kg, 27% of doctors from 1 to 2 kg and only 19% more than 2 kg. 80% of doctors applied the main pressure on the veneer using their thumb, while the pressure force was 1.4 kg. For those doctors who pressed the veneer to the tooth with their index finger, the impact value was 0.8 kg. CONCLUSION: The finger pressure on the veneer during cementation applied by dentists varies, the average pressure on the veneers was about 1.5 kg. The amount of pressure on cement during laboratory tests of cements for fixing veneers differs from clinical values many times. The development of a veneers fixation protocol, taking into account the conducted research, will ensure a reliable and accurate fit of the veneer at the stage of its cementing.

[Lower jaw virtual reposition accuracy research]. / Izuchenie tochnosti virtual'noi repozitsii nizhnei chelyusti.

OBJECTIVE: The aim is to study of the accuracy of the virtual reposition of the mandible (LF) by comparing the virtual and real position of the LF heads, as well as the analysis of factors contributing to the occurrence of errors. MATERIAL AND METHODS: An experimental model of a human skull with a movable LF was made of radiopaque material. The resulting computed tomogram (CT) of the upper and lower jaws and temporomandibular joint (TMJ) was combined with dental scans of dental rows and CT scans and a report on the position of the heads of the LF was obtained. Then the LF was shifted to another position and this position was fixed. Optical bite recorders were obtained using an intraoral scanner. An experimental model with a fixed new position of the LF was placed in a tomograph and repeated CT was obtained. In the program, according to optical registers, a virtual reposition of the LF was carried out. The correspondence of the virtual and real position of the mandibular heads was compared. RESULTS: The absolute difference of glenoid fossa space between the actual and virtual reconstruction was 0.542±0.3354 mm in the anterior joint section (M±Î´, M - average mean, δ - standard deviation); for the upper joint section - 0.309±0.2246 mm; and 0.260±0.1862 mm for the posterior section. The integral indicator of surface coincidence (q) when the virtual and actual position are directly compared was 0.296±0.1254 (s.u.). CONCLUSION: The total margin of error depends on the following factors: repeated scanning error (teeth arches and bite scans), repeated CBCT error, a combination of scan and CBCT error, a combination of teeth arch scan and bite scan error, error of TMJ separation. The latter two factors were the most significant.

[Comparison of the film thickness of composites of different degrees of viscosity]. / Tolshchina plenki kompozitov raznoi stepeni vyazkosti.

The measurement of the film thickness of the composite cement Variolink Esthetic («Ivoclar-Vivadent¼, Liechtenstein) and the microhybrid composite Enamel («Micerium¼, Italy) was carried out according to ISO 4049: 2009 standards with a load force of 5 kg. While reducing the load force to 5 kg, all materials showed an increase in the film thickness; the film thickness of the Variolink Esthetic composite cement was changed from 23 microns (at 15 kg) to 32 microns (at 5 kg), and the film thickness of the microhybrid composite film Enamel was changed from 39 microns (at 15 kg) to 102 microns (at 5 kg). After preheating, the film thickness was changed from 23 microns (at 15 kg) to 44 microns (at 5 kg).

[Study of the film thickness of dental composite resins after preheating]. / Izuchenie tolshchiny plenki kompozitov posle ikh nagrevaniia.

PURPOSE: To compare film thickness of adhesive resin cement and dental composite resins after they are preheated with hot air. MATERIAL AND METHODS: The film thickness was measured using adhesive resin cement Variolink esthetic (Ivoclar-Vivadent, Liechtenstein), micro-hybrid composite Enamel (Micerium, Germany) and nanofilled composite Estelite sigma quick (Tokuyama Dental, Japan) at different temperatures. RESULTS: The film thickness of the Variolink esthetic at room temperature was 23 µm, and the dental composites after preheating them with hot air and applying adhesive on both surfaces to be joined produced the following results: Estelite 62 µm and Enamel 25 µm. CONCLUSION: As a result of the study, it was found that the proposed method allows one to achieve a film thickness for high-viscosity composites comparable to the film thickness of composite cements.

[The 'axial' method of teeth preparation for fixed partial and telescopic dentures]. / 'Osevoi' metod preparirovaniia opornykh zubov pri protezirovanii mnogoopornymi konstruktsiiami.

The article describes the method preparation of teeth which would be united by single construction of prosthesis. The proposed method has 2 features from the currently known methods. Firstly, axial preparation lines are applied on each abutment teeth by using needle narrow diamond bur. Lines could be performed on 3 walls of abutment teeth (vestibular, occlusal, lingval) and should be parallel each other. Secondly, the mirror for intraoral dental photography is used during the preparation by this method. The large surface of this mirror allows to see several teeth at the same time. The mirror is placed in the mouth at different angles which helps to accurately visualize the convergence all walls of abutment teeth. The advantage of this method is ability to use a microscope or binoculars for magnification during preparation.

[Laboratory evaluation of retraction cords properties].

The aim of the study was the investigation of the effect of two factors on the diameter changings of different types of retraction cords. Using an optical microscope MBS-10 (x10) the diameter of the different retraction cords was measured. The measurement also was performed after tension and after wetting cords with distilled water. The cords diameter decreased after their tension and increased after wetting. The degree of diameter changes depends on the kind of cords weaving. Braided cords "00" and "1" sizes diameter after it tension decreased at 31% and 37%, knitted cords under tension changed the diameter at 53% and 48%, correspondingly. Cords features after wetting also varied. Wetting of the braided cords with distilled water did not lead to significant diameter changes while wetting of knitted cords increases their diameter at 13% (00) and 15% (1).

[Estimation of impression quality in fixed prosthesis oral rehabilitation].

In spite of the constant improvement of impression materials impression taking is still rather challenging procedure. Impression quality considerably defines the effectiveness of prosthodontics oral rehabilitation. The method for impression quality assessment was elaborated in the study and used to estimate the quality of impressions taken for fixed prosthesis (teeth preparation quality was not assessed). More than 50% of impressions had improper quality.

[A new method of imprint receiving for non-removable dentures].

An original method of precision imprint receiving is described that provides high dimensional precision under maximal dynamic pressure on impression material and its penetration into gingival crevice. Comparison of the new method of imprint receiving with different traditional methods of impression making for non-removable dentures is made.

[Influence of the type of impression material, impression tray and making impression technology on the dimensional accuracy and depth of impression material penetration into "gingival sulcus". In vitro study].

Results of the profound study of influence of the type of impression material, impression tray and making impression technology upon main quality characteristics of the precise impression (dimensional accuracy and depth of impression material penetration into gingival sulcus) are reviewed. Original method to investigate depth of impression material penetration into gingival sulcus on experimental model is described. The impression technology exercises more influence on quality characteristics of the precise impression than type of the used material and impression tray. Optimal combination of different viscosity impression materials with technology of making impression has been defined.