ИСТИНА

http://wcb2018.com/poster-schedule/, http://wcb2018.com/wp-content/uploads/2018/06/Programme-Numbers-for-Posters-29.06.18.pdf (Submission ID = 4367) Introduction One of the key factors in the success of dental implantation is osseointegration. Excessive micromobility on the implant-bone (I-B) interface (IF) at loading violates the osseointegration. A natural question arises: is it possible to minimize micromobility by controlling the structural characteristics of the implant, in particular, of the threads? Methods In this paper, the emphasis was on immediate loading (primary stability), when osseointegration has not yet occurred and there is no complete adhesion at the I-B IF. The bone was modeled by a half-space, the im-plant – by a cylinder flush with the half-space surface, the slip condition was set on the implant-bone inter-face, typical values were taken for the load, geometrical and mechanical characteristics of the bone and im-plant. Calculations were conducted in ANSYS. Results The change in the thread profile was modeled by the variation in the slope angle of the profile sides with a successive transition from the triangular through the trapezoidal and square threads to the dovetail thread. With this, the implant subsidence (global mobility) varied little (a fraction of a percent). At the same time, the maximums of local displacements (relative displacements of the implant and bone corresponding points) – and they are that affect osseointegration – could vary at times (with a general tendency to fall) with this change in the profile of the thread (Fig. 1). Apparently, this is due to the increase in the engagement and, Fig. 1: Evolution of the displacements pattern at the interface of a dental implant and bone versus thread profile under vertical loading consequently, in constraint of movements on the faces of the thread. Minima of maximum local displace-ments were obtained for the square and dovetail profiles. Their values were microns, which corresponds to the results of other authors. In this case, the displacements values grew monotonically from the last turn to the first (apex) one and the maximum was invariably observed at the apex thread turn. Since the dovetail profile may be problematic in manufacturing the effect of the thread depth and pitch was studied on the square profile. It turned out that an increase in the thread depth from 0.1 to 0.4 mm (as well as reducing the thread pitch from 2.0 to 0.4 mm) led to a decrease in the implant sediment by 3-6% and to a significant (multiple) monotonic fall in the displacements on the IF. Conclusions With the same occlusal load values and observed macromobility of the implant the thread characteristics can change micromobility on the implant-bone interface by times. Minimal local displacements were obtained for the square and dovetail profiles. Maximum of local displacements was observed at the apex thread turn. Acknowledgements RFBR №17-08-01579 and RFBR №17-08-01312.