ИСТИНА

http://wcb2018.com/poster-schedule/, http://wcb2018.com/wp-content/uploads/2018/06/Programme-Numbers-for-Posters-29.06.18.pdf (Submission ID = 4336) Introduction Individualization of medical treat is one of the hot points of today’s medicine. A computer simulation of orthopedic rehabilitation planning for a patient (born in 1947) with implant placement onto the edentulous mandible was carried out. Methods In order to optimize the distribution of functional stresses in the bone tissue around the implants, as well as in prosthetic structures, several implantation schemes were considered: with 2, 4 and 6 implants. Implant computer models were created according to the data given in the accompanying documentation, as well as from the results of direct measurements. To personalize the diagnostic data, mandible cone-beam computerized tomography was done with the dental tomograph Galileos (Sirona). Image processing, including segmentation, creation of a three-dimensional triangulated surface model and a tetrahedral grid, was carried out in the MIMICS program (Fig. 1). The model obtained was supplemented with implants Fig. 1: Determination of the x-ray density of the mandible models and passed on to the finite-element complex ANSYS, where numerical simulation was carried out. Titanium and zirconium dioxide implants 10-11 mm long and 3.5 mm in diameter were taken. For removable dentures schemes were studied on a beam with a semi labile fixation and with rigid locking fastening to the beam, fixed dentures were provided with small cantilevers. Different loading schemes were considered, corresponding to central (nibble) and one-sided (chewing) occlusion. Central occlusion was modeled by applying vertical or oblique loads to two central implants. There were cases of complete (adhesion on the implant-bone interface) and incomplete (sliding or friction on the interface) osseointegration. Results Areas of stress concentration in the bone in all cases arose at the thread tops and carvings, and especially in the vicinity of the implant neck (platform). Micromotions (relative displacement of corresponding points on the implant-bone interface) in the case of complete osseointegration were absent, while for incomplete osseointegration (primary stability) the maximum micromotions appeared on the first (apex) thread. Conclusions 1. The material of implants and dentures (titanium or zirconium dioxide) has little effect on the stress-strain state of bone tissue. 2. Increased osseointegration (modeled by increasing friction from full slip to full adhesion) leads to a decrease in the concentration of both stresses and displacements. 3. Oblique loads are more dangerous than vertical ones, loading in the lateral part of the artificial dentition is more dangerous than in the frontal compartment. 4. Comparison of different implantation schemes shows that: • an increase in the number of implants somewhat smoothes the concentration of both stresses and displacements in bone tissues; • for prosthetics on an edentulous mandible, fixed dentures on a larger number of implants are biomechanically preferable compared to a removable denture. Acknowledgements RFBR №17-08-01579 and RFBR №17-08-01312.