The aim of this work is to increase the effectiveness of prosthetic rehabilitation of edentulous patients by means of clinical and biomechanical substantiation of indications for the use of implants in removable dental prosthetics. At the first stage of our work, we conducted a comparative study of 72 patients with complete adentia who use traditional designs of complete removable dentures and 31 persons who had removable dentures supported on implants. Visually, the condition of the mucous membrane of the prosthetic bed in patients with different types of removable designs did not differ significantly. However, after macrohistochemical dyeing, signs of chronic inflammation were diagnosed in 78.8% of patients with complete removable dentures and 68.8% – with supporting on implants. In patients with complete removable dentures, the generalized nature of inflammation prevailed. When using traditional designs of complete removable dentures for mandible, a reliably lower degree of preservation of bone tissue was established in the frontal area, compared to prosthetics on implants. So, the use of intraosseous support allowed evenly distributing chewing pressure between the base plane and supporting implants. In patients with removable dentures supporting on implants, more pronounced atrophy was observed in the lateral areas. At the second stage of our work, we studied 24 virtual end-element models "complete removable denture – mandible" and "removable denture – intraosseous implants – mandible", which differed from each other in the direction of applying forces and the shape of the alveolar part of the mandible. Additional fixation of removable dentures on implants in imitation models led to a significant increase in stresses in the alveolar bone. According to the calculations, the use of complete removable dentures is most indicated under the first type of toothless mandible, when it is possible to avoid quick atrophy of the distal parts of the alveolar part of the mandible. In the second type, significant uniform atrophy of the alveolar part of the mandible is an indication for dental implantation. According biomechanics, in the third and forth types of atrophy of the toothless mandible it is advisable to use implants, but their location in areas of low alveolar process is desirable. In general, to prevent atrophy of the alveolar bone in all types of toothless mandible, it is advisable to consider the possibility of increasing the number of supporting implants. As a result of the treatment of 90 patients with complete defects of the lower dentition it was found, that under the forth type of toothless mandibles, good and satisfactory fixation of prostheses can be achieved only by applying an additional support on implants. "Classic" removable dentures had a high degree of efficiency for the first type of atrophy. In the second and third types of alveolar atrophy, no complete removable denture had a good fixation. At the same time, supporting on implants provided sufficient fixation of dentures, while there was a particularly noticeable difference in the effectiveness of prosthetics of patients with the second type of mandible atrophy. Chewing efficiency was higher among patients, in which complete defects of the lower dentitions were restored by designs supporting on implants, mainly with locator-abutments. However, in cases of prosthetics with complete removable dentures under the first type of mandible atrophy, the results could be matched with the data obtained as a result of dental implantation. During the computer diagnostics, the occlusion disharmony was established in cases of uneven atrophy of the alveolar part when using both complete removable dentures and supporting on implants. Only under uniform bone atrophy, uniform distribution of occlusial contacts can be achieved. According to computer tomography in patients with the first type of atrophy, when using "classic" complete removable dentures, there was a uniform widespread loss of bone tissue, while the use of implants leads to a more pronounced loss in the lateral areas. In the second type of atrophy, there were no reliable differences between shapes of the alveolar parts for different types of fixation of removable dentures. Under the third type of toothless mandible, atrophic processes more intensively occurred in the frontal parts when using complete removable dentures, while for lateral parts there was no significant difference. Under the fourth type of atrophy of the toothless mandible, fixation on implants was gentler in terms of preserving the alveolar part in the frontal part, and in the lateral parts the same effect was for complete removable dentures. But there were no reliable differences between the indicators of research groups. It is indicative, when implants were used, the alveolar process in the lateral parts of the fourth type of mandible atrophy was preserved to a greater extent than under the first one.
