A STUDY ON THE ELASTIC DEFORMATION AND STRESS DISTRIBUTION OF THE MANDIBLE WITH OSSEOINTEGRATED IMPLANT PROSTHESES USING THREE DIMENSIONAL FINITE ELEMENT ANALYSIS METHOD

Kim, Yong Ho; Kim, Yung Soo; Kim, Chang Whe

Abstract

The human mandible is always under the condition of loading by the various forces exterted by the attached muscles. The loading is an important condition of the stomatognathic system. This condition is composed of the direction and amount of forces of the masticatory muscles, which are controlled by the neuromuscular system, and always influenced by the movement of both opening and closing. Mandible is a strong foundation for the teeth or various prostheses, nevetheless it is a elastic body which accompanies deformation by the external forces on it. The elastic properties of the mandible is influenced by the various procedures such as conventional restorative treatments, osseointegrated implant treatments, reconstructive surgical procedures and so forth. Among the treatments the osseointegrated implant has no periodontal ligaments, which exist around the natural teeth to allow physiologic mobility in the alveolar socket. And so around the osseointegrated implant, there is almost no damping effect during the transmission of occlusal stree and displacements. If the osseointegrated implants are connceted by the superstructure for the stabilization and effective distribution of occlusal stresses, the elastic properties of mandible is restricted accordding to the extent of 'splinting'by the superstructure and implants. To investigate the change of elastic behaviour of the mandible which has osseointegrated impalnt prosthesis of various numbers of implant installment and span of superstructure, a three dimensional finite element model was developed and analyzed with conditions mentioned above. The conclusions are as follows : 1. The displacements are primarily developed at the area of muscle attachment and distributed all around the mandible according to the various properties of bone. 2. The segmentation in the superstructure has few influence on the distribution of stress and displacement. 3. In the load case of ICP, the concetration of tensional stress was observed at the anterior portion of the ramus(9.22E+6Nmm2) and at the lingual portion of the symphysis menti(8.36E+6Nmm2). 4. In the load case of INC, the concentration of tensional stress was observed at the anterior portion of the ramus(9.90E+6Nmm2) and the concentration of tensional stress was observed at the lingual portion of the symphysis menti(2.38E+6Nmm2). 5. In the load case of UTCP, the relatively high concentration of tensional stress(3.66E+7N/mm2) was observed at the internal surface of the condylar neck.