Mishchenko O. Clinical and experimental study of new methods in dental implantation with exploitation of implants from zirconium alloys

The dissertation presents theoretical substantiation and practical solution of actual scientific problem - increase of efficiency of dental defects replacement with fixed dentures with reliance on dental implants by improvement of physical and mechanical properties of implants, their construction and surface structure. Taking into account the multidisciplinary tasks, research was structured into 4 stages, which include 1) development of a new alloy with predicted biomechanical parameters; 2) identification of surface modification methods; 3) processes modeling of mechanical interaction in the system "implant-bone tissue"; 4) clinical study of the effectiveness of establishing new types of dental implants. The novelty of the work is in the creation of a new low-modulus Zr-Ti-Nb alloy with the lowest Young's modulus, which can significantly reduce the problem of stress shielding effect during implant exploitation. Using the method of three-dimensional modeling, the optimal shape of the intraosseous part of the implant with the greatest contact with bone tissue is established, which can accelerate the processes of osteointegration. The cell culture model established the biocompatibility of the new alloy and increased the proliferation of osteoblasts with its modification by hydroxyapatite. A new method of mesoporous surface formation by plasma electrolytic oxidation with the formation of a bioactive layer, which is able to stimulate the processes of osteointegration, has been developed and implemented. A nanostructured surface was first created using laser ablation in the femtosecond range, which is able to stimulate the adhesion and proliferation of both osteoblasts and fibroblasts, with a predominant effect on the latter. Analysis of the proliferative activity of osteoblasts after 3 and 7 days from the beginning of cultivation indicates their active growth and proliferation in the group with calcium phosphate coating. It can be argued that the presence of hydroxyapatite stimulates the proliferation of osteoblastic cells. Animal experiments with different alloys (Ti and Zr) with hydroxyapatite modification showed that at the early stages after implantation of metal alloys, organic matrix adhesion occurs on their surface, while the presence of hydroxyapatite coating provides a more stable adhesion, is a predictor of direct osteointegration. In general, the biomechanical parameters of the alloys play a key role in the process of bone reconstruction around the implants. At the same time, implantation of β (Zr-Ti) alloy results in a slight alteration of the tissues in the implantation area. When comparing the clinical efficacy of traditional titanium alloy implants with our proposed low-modulus titanium-zirconium alloy implants, it was found that zirconium alloy screw implants showed a lower bone loss by 30.1 ± 3.8% compared to the titanium implantants group of implants functioning. The bleeding index of the gums at the implant site, as one indication of an inflammatory process, directly correlates with the volume of bone loss in the surrounding implant areaand in group with Zr implants was in 41% less compare the Ti. The results obtained were implemented through the production of new implant systems both in Ukraine (PP Eksima) and abroad (Nano Prime, Poland), which made it possible to implementation in practical dentistry.