[Comparative evaluation of the accuracy of 3D TMJ analysis performed by different methods of processing computed tomograms]. / Sravnitel'naya otsenka tochnosti 3D-analiza elementov visochno-nizhnechelyustnogo sustava, vypolnennogo raznymi sposobami obrabotki komp'yuternykh tomogramm.

OBJECTIVE: The aim of this study. Comparison of the accuracy of segmentation of TMJ elements in different ways and assessment of the suitability of the data obtained for the diagnosis of TMJ dysfunction. MATERIALS AND METHODS: To study the segmentation of the bone elements of the TMJ (articular fossa, head of the LF), 60 computed tomograms of the maxillofacial region of patients were randomly selected in various ways (archival material). In group 1, the results of CT processing by AI diagnostics algorithms (Russia) were collected; in group 2, the results of CT processing based on the semi-automatic segmentation method in the Avantis3D program. The results of CT processing by Avantis3D AI algorithms (Russia) with different probability modes - 0.4 and 0.9, respectively, were selected for the third and fourth groups. Visually, the coincidence of the contours of the LF heads and articular pits isolated using different methods with their contours on all possible sections of the original CT itself was evaluated. The time spent on TMJ segmentation according to CT data was determined and compared using the methods described above. RESULTS: Of the 240 objects, only 7.5% of the cases showed a slight discrepancy between the contours of the original CT in group b1, which was the lowest of all. A slight discrepancy in the TMJ contours to be corrected is characteristic of the semi-automatic method of segmentation by optical density was detected in 50.4% (group 2). The largest percentage of significant errors not subject to correction was noted in the first group, which made it impossible to perform a full 3D analysis of the TMJ, and the smallest in the second and fourth. The magnitude of the error in determining the width of the articular gap in different groups is comparable to the size of one voxel per CT. When segmentation is carried out using AI, the difference between segmented objects is close to zero values. The average time spent on TMJ segmentation in group 1 was 10.2±1.23 seconds, in group 2 - 12.6±1.87 seconds, in groups 3 and 4 - 0.46±0.12 seconds and 0.46±0.13 seconds, respectively. CONCLUSION: The developed automated method for segmenting TMJ elements using AI is obviously more suitable for practical work, since it requires minimal time, and is almost as accurate as other methods under consideration.

[Metal 3D printing in dentistry]. / 3D-pechat' iz metallov v stomatologii.

The article describes the use of 3D printing in dentistry, the principle of operation of 3D printers for metals, a review of comparative data on the quality and accuracy of the final product of 3D metal printing is carried out. Possibilities and prospects of using 3D metal printing in dentistry are indicated.

[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.

[3D analysis of anatomical and functional parameters of TMJ and their correlation]. / Tsifrovoi 3D analiz anatomicheskikh i funktsional'nykh parametrov VNChS i ikh korrelyatsiya.

THE AIM OF THE STUDY: Was determination of TMJ anatomical and functional parameters in patients without clinical manifestations of TMJ dysfunction and analysis of possible relationships between them. MATERIAL AND METHODS: TMJ anatomical parameters of 25 volunteers (22-27 years old) without TMJ dysfunction, malocclusion and more than one tooth adentia were determined on CT scans and lab teeth scans: inclination of the distal slopes of the articular eminence (DS AE), height and width of the condyles, height of AE, inclination of the longitudinal axes of the condyles; as well as functional parameters of LJ movements: horizontal condylar inclination (HCI) during protrusion and laterotrusion, lateral condylar inclination during protrusion and laterotrusion, immediate side shift, incisor and canine guidance, and correlations between them were evaluated. RESULTS: The majority of the TMJ anatomical parameters are almost equal by mean values on the right and left sides. The main TMJ functional parameters on the right and left sides also have similar values but much higher variability, asymmetry and unpredictability. The existing anatomical asymmetry of the DS AE is compensated by articular discs, which makes HCI more symmetrical. CONCLUSION: Protrusion movements have a higher probability of reproduction by mechanical articulators while laterotrusion movements have a very low probability. The existence of relationship between the inclination of DS AE and HCI, between HCI and the incisor guidance, between the inclination of DS AE and the incisor guidance is questionable. The conducted research proves the weakness or complete absence of correlation between them.

[Validation of the technique of TMJ 3D analysis based on computer tomography]. / Obosnovanie metodiki 3D-analiza visochno-nizhnechelyustnogo sustava po dannym komp'yuternoi tomografii.

OBJECTIVE: The main aim of the study is devoted to optimization of the technique of 3D analysis of TMJ parameters, analysis of the causes of possible errors. MATERIALS AND METHODS: The technique of 3D analysis of the width of the articular gap, the size of the condyle, the height and slope of the distal slope of the articular tubercle in the Avantis3D software (Russia) according to computed tomography is presented. The influence of repeated manual corrections of the condyles and articular fossa contours, shifting of the sectors measuring center, the position of starting point of the measurement sectors, and different algorithms for determining the longitudinal axis of the condyles on the accuracy of TMJ parameters detection. RESULTS: The study showed that any artificial displacement of the center of measurement sectors, which coincides with the longitudinal axis of the condyle, leads to significant value changes of the parameters. In this regard, the exact determination of the longitudinal axis of the condyles, independent of the human factor, is of particular importance. The greatest inaccuracy and variability of the results of measuring the parameters of the TMJ, as shown by the study, is associated with the possible manual correction of the contours of the surfaces of the condyles and articular fossa. The study did not find a noticeable difference in measurements if the sectors starts from the top of the articular tubercle or from the line parallel to the Frankfurt horizontal. As the optimal settings of the developed method was determined, it was used to determine the average values of the TMJ parameters for patients with a conventional «norm¼, as well as for patients with TMJ dysfunction. A noticeable and statistically significant difference was found between the groups only for upper and posterior width of the joint space. CONCLUSION: The average values of the intra-articular spaces width were justified, and can be used as the basis for the virtual assignment of the lower jaw reconstructive position for prosthetic or orthodontic treatment.

[3D analysis of occlusal surfaces of teeth and their contacts. Part III. Development of a method for assessing the balance of occlusal contacts]. / 3D-analiz okklyuzionnykh poverkhnostei zubov i ikh kontaktov. Chast' III. Razrabotka metoda otsenki balansa okklyuzionnykh kontaktov.

OBJECTIVE: The aim of the study was to develop a technique for 3D analysis of the occlusal balance of teeth. MATERIAL AND METHODS: The development was carried out on the basis of the Avantis 3D software («Avantis 3D¼ LLC, Russia) using teeth scans of 50 subjects with Class I and II (Division 1) malocclusion and different degree of tooth wear. The algorithm and formulas for calculating the balance of symmetry and antero-posterior occlusal balance are presented. The essential features of the technique and the interpretation of the obtained indicators are explained on different clinical cases. Statistical analysis of the results of measuring occlusal balance of patients with different degree of teeth wear and malocclusion is presented. RESULTS: It is determined that the balance of common contacts is more important than the balance of direct contacts. CONCLUSION: Alignment of teeth without noticeable wear provides a better occlusal balance then before. The occlusal balance of worn teeth after alignment may be not good and require selective grinding or restoration of their occlusal surfaces.

[3D analysis of occlusal surfaces of teeth and their contacts. Part II. Assessment of the degree of wear of occlusal surfaces]. / 3D-analiz okklyuzionnykh poverkhnostei zubov i ikh kontaktov. Chast' II. Otsenka stepeni iznosa okklyuzionnykh poverkhnostei.

THE PURPOSE: Of this study was to evaluate the informativeness of the developed tools for 3D analysis of occlusal surfaces and their mutual contacts on the example of tooth rows with different degrees of abrasion and bite features. MATERIAL AND METHODS: The developed method of 3D analysis of occlusal contacts (in the range of 0-300 microns of occlusal surfaces separation) was tested in 50 people with different degrees of tooth abrasion. RESULTS: It is determined that the area of direct contacts (in the range of separation 0-50 microns) increases from 30 to 150% depending on the degree of abrasion of teeth during virtual optimization of contacts. The area of occlusal contacts increases as the teeth wear out, and the relief index decreases. With virtual alignment of abnormally placed teeth, the contact area also increases, with the exception of patients with tooth abrasion up to dentin. When teeth wear out, the proportion of direct contact zones increases relative to the total contact area and the proportion of near-contact zones decreases (200-300 microns). CONCLUSION: Four key indicators and ranges of their values for differential diagnosis of the degree of tooth abrasion were determined.

[3D analysis of occlusal surfaces of teeth and their contacts. Part I. Development of a method for assessing the area of the occlusal surface, the severity of its relief and the histogram of contacts]. / 3D-analiz okklyuzionnykh poverkhnostei zubov i ikh kontaktov. Chast' I. Razrabotka metoda otsenki ploshchadi okklyuzionnoi poverkhnosti, vyrazhennosti ee rel'efa i gistogrammy kontaktov.

The article is devoted to the development of methods and software for 3D analysis of the occlusal surface of teeth and occlusal contacts between antagonists. An algorithm for accurately determining the boundaries of the occlusal surface on the tooth surface for subsequent quantitative analysis: the area of the occlusal surface, the relief index, and the height of the cusps is presented. The area of not only direct contacts, but also near-contact zones in any of the selected surface separation ranges is quantified. Examples with geometric primitives and clinical examples explain the features and interpretation of 3D analysis datas obtained using the developed software.

[Virtual positioning of the mandible to the position of the central relationship in a clinical example]. / Virtual'noe pozitsionirovanie nizhnei chelyusti v polozhenie tsentral'nogo sootnosheniya na klinicheskom primere.

On the example of a clinical case of functional TMJ disorders associated with loss of bite height, an algorithm for virtual determination of the Central relation position of the jaws based on the controlled width of the articular gap and the height of the bite is described. The subsequent 3D design and application of the repositional splint showed the reality of achieving the pre-planned position and the possibility of implementing the proposed approach in clinical practice.

[Assessment of supracontacts size at digital positioning of scans in habitual occlusion]. / Opredelenie velichiny okklyuzionnykh suprakontaktov pri virtual'nom sovmeshchenii skanov v polozhenii privychnoi okklyuzii.

The study is devoted to the error analysis of digital registration of lower and upper jaws laboratory and intraoral scans in position of habitual occlusion. It was found that in both cases, penetrating contacts (supracontacts) are formed, and their depth is in the range (-50) - (0) microns. The number and area of these contacts is higher for lateral teeth. The number and area of supracontacts is higher for laboratory scanning (3.7±1.81 mm2) than for intraoral scanning (0.5±0.42 mm2). Applying virtual contact optimization does not change the localization of contacts, but rather normalizes them in both cases. It is recommended to perform this preliminary correction before the planning stage in 3D dental treatment.

[3D analysis of the temporomandibular joint and occlusal relationships based on computer virtual simulation]. / 3D-analiz visochno-nizhnechelyustnogo sustava i okklyuzionnykh vzaimootnoshenii na osnove komp'yuternogo virtual'nogo modelirovaniya.

AIM: To develop a method for automated analysis of TMJ elements based on computed tomography and a method for analyzing the features of the ratio of TMJ elements when changing the position of the mandible without repeated CT examination. MATERIAL AND METHODS: To complete method required a computer tomogram of the temporomandibular joint in habitual occlusion recorded on spiral or cone-beam imaging; and 3D scans of the dentition obtained with intraoral and laboratory scanners; computer software - 3D graphics editor that can handle volumetric CT data and 3D mesh objects. RESULTS: Analysis of the joint space of the temporomandibular joint in the entire volume, not a single slice represents a more complete and reliable information about the condition of the joint. The presented method of predicting the position of TMJ heads on the basis of obtaining bite registers eliminates the probable errors of the doctor and the need for repeated CT scans, which reduces the radiation load on the patient. Virtual simulation of movements of the mandible from the position of habitual occlusion in the position of Central correlation, protrusion, right and left literaturesee with the visualization of movements of the articular heads helps to better understand the biomechanics of the TMJ, diagnostics and to obtain valuable data about the individual characteristics of the masticatory apparatus of the patient. CONCLUSION: The developed virtual articulator (patent No. 2567604) is another useful step in the development of digital technologies in dentistry.

[X-ray assessment of the position of the lower jaw heads in different types of face]. / Rentgenologicheskaia otsenka polozheniia golovok nizhnei cheliusti pri razlichnykh tipakh litsa.

AIM: To increase the efficiency of diagnosis and orthodontic treatment of patients with temporomandibular joint dysfunction based on the study of the relationship between the features of the position of the heads of the lower jaw and various face types in patients aged 25 to 44 years according to cone beam computed tomography. We examined 100 people who were divided into two main groups (50 males, 50 females). To study the formed groups index method for diagnosing facial types according to Isar was used. The facial indicator was determined: the percentage of physiognomic height to the morphological width of the face. The structural features and relative positions of the TMJ bone structures in patients with TMJ dysfunction in various face types were studied in the Avantis 3D computer program. It was noted that the upper position of the lower jaw heads in women and men with a narrow type of face was observed in 50% and 40% of cases, respectively; the distal position of the lower jaw heads in women and men with a wide type of face was observed in 50% and 42.3% of cases, respectively. The results of the study indicate that there is a relationship between different types of face and the position of the lower jaw heads in the lower jaw, which should be considered in comprehensive treatment planning. The most at risk of temporal dysfunction is the TMJ of a woman with a narrow type of face, in which dominates the upper position of the lower jaw heads and a woman with a wide type of face with the distal position of the lower jaw heads. Before orthodontic treatment it is necessary to investigate the position of the TMJ heads with the help of CBCT and make a mandatory correction before the beginning of orthodontic treatment.

[A comparative analysis of reproducibility of the jaws centric relation determined with the use of digital technologies]. / Sravnitel'nyi analiz vosproizvodimosti tsentral'nogo sootnosheniia cheliustei s ispol'zovaniem tsifrovykh tekhnologii.

AIM: To compare the precision of centric relation (CR) assessment by various methods using digital technologies. MATERIAL AND METHODS: Determination of the CR was carried out in the clinic of prosthetic dentistry on patients with intact dentition using methods of bilateral manipulation, anterior jig, leaf gauge and device for intraoral recording of the gothic arch angle. Optical jaw impressions were obtained using the intraoral 3D scanner Trios (3Shape) and the CR registers were scanned using the laboratory scanner Prime (DOF). To evaluate the reproducibility of the CR, the computer program of 3D modeling Avantis (Russia) was used, which integrated the obtained optical impressions and digital copies of the CR registers. RESULTS: None of the methods showed 100% accuracy in CR assessment. The most stable reproducibility of the position of the mandible in the CR relative to the first registration was determined by the method using an anterior jig (of our own design) and amounted to 0.119±0.012 mm, which is significantly less than using the methods of bilateral manipulation (0.225±0.028, p≤0.05) and a leaf gauge (0.207±0.02, p≤0.05). We observed a similar mean values of the reproduction accuracy when determining the CR by recording the Gothic arch angle (0,120±0,013, p≤0.05), which also has a significantly lower value (p≤0.05) compared to other methods for CR determining.

[Analysis of the color changes in teeth at different depths preparation]. / Analiz izmeneniia tsveta zubov pri ikh soshlifovyvanii na razlichnuiu glubinu.

Spectrophotometric analysis of the extract and intact teeth revealed the color characteristic of teeth ranged from the cervical area to the cutting edge, as well as by preparation of dental hard tissue to 0.3 mm, 0.6 mm, 0.9 mm depth. Lightness increased as preparation approached dentine. The intensity of the Lightness was more pronounced in the cervical region which is associated with a thin layer of enamel performing the lens function. It is found that Hue values weakly depend on the depth and location of the preparation, the tooth reflecting a relatively constant range of visible wavelengths. During preparation of the hard tissue at different depths the color difference δE* was greater than 2.6 meaning that the color must be registered before and after preparation.

[Cephalometric estimation of vertical dimension of occlusion]. / Opredelenie vysoty prikusa po rezul'tatam tsefalometricheskogo analiza bokovoi telerentgenogrammy.

The aim of the present study was to develop algorithms for determination of vertical dimension of occlusion on the basis of methods of cephalometric fnalysis suggested by different authors. Proposed methods of cephalometric fnalysis allow to additionally evaluate markers for vertical dimension determination in dental reconstructive treatment.

[The method of quantitative assessment of dentition aesthetic parameters].

This article describes the formula for calculating the aesthetic index of treatment outcome. The formula was derived on the basis of the obtained regression equations showing the dependence of visual assessment of the value of aesthetic violations. The formula can be used for objective quantitative evaluation of the aesthetics of the teeth when smiling before and after dental treatment.

[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).

[Visual perception of dentition esthetic parameters (part 1)].

The article presents a study on the impact of violations of aesthetic parameters as the inclination of the incisalline, thedislocation of median interincisal line and the width of dental arch on visual perception. Comparison of the data of objective assessment data the subjective assessment of the respondents was conducted. It is proved that all dependencies are linear and can be described by a linear regression equations. A similar method can be used for objective quantitative method for the assessment of aesthetics teeth when you smile before and after dental treatment.

[Experimental study of the collagen matrix for increase the gums using a 3D-modeling].

In an experimental study on mini-pigs demonstrated that the use of collagen matrix Mucograft open method leads to the formation of mature connective tissue around the implants, more pronounced after 70 days, and the width of attached mucosa already 45th day (from 4.4 ± 0.3 to 7.7 ± 0.5 mm) is comparable to that of free gingival graft. Three-dimensional computer modeling of jaws experimental animals showed the soft tissue augmentation by 0.8 ± 0.1 cm3 after use of collagen matrix Mucograft and 1.1 ± 0.12 cm3 after free gingival graft.