<p>The design of an immobilizing splint was optimized for periodontitis treatment by computer simulation based on the finite element method. Two variable parameters were its shape and thickness with the aim of thinning it, but ensuring both immobilization of teeth and load-bearing capacity during the warranty period. The possible presence of microcracks in the ZrO₂ ceramics, formed at the manufacturing (milling) stage, was considered as one of the limiting factors. In addition, the deformation behavior of the “teeth – immobilizing splint – periodontal ligament – alveolus” dental structure was analyzed. In Part 1 of the paper, the main attention was paid to the preliminary splinting stage, at which temporary polymer splints were installed in order to determine the comfortable shapes for patients. For this purpose, both stresses and displacements were calculated when varying materials and thicknesses of the splints. It was shown that computer simulation facilitated planning periodontitis treatment at various stages of its development, in particular by optimizing the design of the immobilizing splints considering typical loads upon biting off and mastication. It was found that the use of high performance polymer - polyetheretherketone enabled to improve the mechanical properties of such dental structure components comparing with those of conventional polymethyl methacrylate.</p>