Stress-strain state of bone tissue of the mandible at loading of the non-removal prosthesis on intraosseous dental implants at the substitution of the tooth defect of the teeth range

The aim of the study was three-dimensional mathematical modelling of the stress-strain state of the cortical bone tissue of the lower jaw with functional loads of 150 N non-removable prosthesis on implants with complete absence of teeth. The finite element method was used. The regions and magnitude of maximum stresses in the following modelling variants were analyzed: the load of the lateral or frontal parts of the prosthesis; presence of 3, 4 and 6 intraosseous implants; different length of implants - 8.0; 12.5 and 15.0 mm; different diameters of implants - 3.5; 3.9; 4.3 and 5.0 mm; installation of parallel implants or "All for Four" technology. The stress distribution patterns show their concentration in the area of contact with the implants. Based on the strength limits of cortical bone tissue - 130 MPa, the functional load of nonremovable prostheses on implants in the frontal part of the mandible does not cause marginal stresses in it, however, in the presence of thin and insufficiently dense cortical bone tissue, implant installation using the "All for Four" and "Branemark Novum" as a support of a permanent prosthesis with complete absence of teeth can promote functional overload of periimplant bone tissue. The lateral load of the prosthesis in these situations causes stresses 39.00 and 32.12 MPa, respectively, in the bone tissue around the extreme implants. Stresses decrease with increasing number, length and diameter of implants, as well as with intercortical and bicortical implant placement. The obtained biomechanical regularities can be useful in choosing the methods of implant installation, their number and size parameters for permanent prosthetics with complete absence of teeth.