[Elimination of defects in the Schneiderian membrane during sinus lift operations]. / Ustranenie defektov membrany Shneidera vo vremya provedeniya operatsii sinus-liftinga.

PURPOSE: Evaluation of the effectiveness of a new method of plasty of an extensive defect in the mucous membrane of the Schneiderian membrane, which occurs during the sinus lift operation, using an artificial collagen membrane and a developed method for fixing it. MATERIAL AND METHODS: A total of 188 patients took part in the study, all of these patients underwent an open sinus lift operation with simultaneous or delayed implantation. Operations were performed under balanced anesthesia. Six months after the operation, according to computed tomography, the height of the formed bone regenerate was estimated. In the area of each missing tooth, the initial bone height and the resulting bone grafting were assessed. Then we compared the average values before and after the operation, the average height difference before and after the operation. RESULTS: In 19 patients during the sinus lift there was an accidental extensive rupture of the mucous membrane of the maxillary sinus. Elimination of the mucosal defect was carried out according to our patented method. All 188 patients were diagnosed with partial loss of teeth with bone tissue deficiency in the distal maxillary sinus. The height of the alveolar process in the projection of missing teeth ranged from 0.5 mm to 5 mm. Delayed dental implantation was performed when the height of the alveolar bone was less than 3 mm, direct when the presence of 3-5 mm. After 6 months, dental implants were installed in the reconstruction zone, after another 6 months - rational prosthetics. CONCLUSIONS: The proposed method of plastic surgery has the following advantages. Firstly, it allows to eliminate the defect of the mucous membrane together with an increase in the height of the alveolar ridge. Secondly, after this method, the integrity of the mucous membrane will be restored. Thirdly, with an alveolar bone height of 3 mm or more, dental implants should also be installed.

[Comparative analysis of different types of implant-abutment interface on the basis of three-dimensional finite element analysis data]. / Sravnitel'nyi analiz biomekhaniki pri razlichnykh uzlakh sopriazheniia implantata i abatmenta na osnovanii dannykh trekhmernogo konechno-élementnogo modelirovaniia.

The purpose of the study was to perform a comparative static and dynamic finite element analysis of various taper and cylindrical implant-abutment connections in three-dimensional (3D) models including: abutment, fixing screw, implant, cortical bone, cancellous bone. 3D implant model was IRIS LIKO-M system (Russia) 4 mm diameter and 10 mm length. All the models (M1-M6) were built in the same way. While maintaining the external design of IRIS LIKO-M implant, they differed only by taper angle 1.25°, 5°, 9° and its height - 0.45 and 1.85 mm; the models (M7, M8) had a cylindrical connection with a joint height of 0.45 and 1.85 mm. The bone model was 6 mm width, included cortical layer was 3 mm and the inner cancellous bone. The results of static FEA of an occlusal load showed that implant with 1.85 mm abutment connection transfer strain from edge of a cortical bone to its inner layer thus preventing marginal bone resorption. The best results showed implant model with conical taper 5° and 1.85 mm height: the smallest von Mises stress in cortical layer at tightening of the fixing screw and at masticatory load, and the larger margin of safety of an implant, the abutment and the fixing screw. The results of dynamic FEA of implant with cylindrical connection demonstrate that the gap between an abutment and an implant may occur and lead to fixing screw loosening or fracture. At the same time, the implant design with knot of interface of conical type 5° remains tight at dynamic load.

[Mathematical rationale and results of clinical use of IRIS short implants]. / Matematicheskoe obosnovanie i rezul'taty klinicheskogo ispol'zovaniia korotkikh implantatov IRIS.

The aim of the study was to provide a mathematical justification of the possibility of using 6.5 mm IRIS implants and to evaluate the results of orthopedic treatment in patients with partial loss of teeth. For the calculations was constructed of a composite three-dimensional computer models: the abutment screw-implant-bone. A total of 3 models were prepared: M1-implant in the spongy bone tissue, this model corresponds to the implantation on the HF when replacing one molar; M2-2 implants in the spongy bone tissue located at a distance of 4 mm connected via abutments, this model corresponds to the implantation of RF when replacing two molars; M3-implant in the cortical bone tissue, this model corresponds to the implantation of LF when replacing one molar. Loading of implants was carried out by occlusive force applied to its end surface. The results of the calculations showed that the equivalent stresses and limiting stresses of compression-tension are within the permissible values, which were obtained by us earlier in respect of the irregular implants and are consistent with the results of calculations for other systems of short implants. The clinical part of the work consisted in the treatment of 27 patients with partial loss of teeth, who had 41 iris evolution implants with a diameter of 5 mm, length of 6.5 mm after 3 years, there was a slow bone resorption in the cervical region not exceeding 0.35 mm, which corresponds to generally accepted international standards. During the first three years of operation there were no cases of loss of established implants. Thus, the data of mathematical modeling by finite element method and retrospective three-year analysis of prosthetics on IRIS evolution implants with length of 6.5 mm showed that the use of short implants in the recovery of upper and lower jaw molars is an effective method with a high success rate at long - term and resorption level of 0.34 mm.