关键词: 牙槽骨高度, 种植修复体, 上颌窦内提升, 动态载荷, 咬合, 应力, 骨组织, 植骨, 有限元分析

Abstract: BACKGROUND: In the field of oral implant restorations, the maxillary posterior region is often confronted with bone atrophy caused by a combination of factors, a phenomenon that greatly increases the complexity of the procedure. To improve the long-term success rate of the surgery, alleviate the discomfort suffered by the patient, and at the same time pursue the simplification and shortening of the surgical process, the maxillary sinus lift technique, especially the immediate weight-bearing method without additional bone grafting, has become a widely adopted strategy. The precise selection of the appropriate implant restoration plan for each individual case with different residual alveolar bone heights is crucial and decisive for ensuring the long term stability of the implant and maintaining the healthy level of the surrounding bone tissue.
OBJECTIVE: To analyze the influence of immediate loading of maxillary molars simulating dynamic occlusion on the stress distribution of implants and bone tissue under different residual alveolar bone height conditions with or without bone grafting using three-dimensional finite element method.
METHODS: Cone-beam CT data of one patient who needed to elevate the maxillary sinus region for implant restoration were obtained, and the maxillary model was constructed by Mimics 21.0 software. After importing the maxillary model into Solidworks 2017 software, the maxillary first molar alveolar bone height of 10 mm conventional single crown restoration model was constructed 7, 5, 3 mm bone-implanted or non-bone-implanted single crown restoration model, respectively. The dynamic occlusion process of posterior teeth was simulated in ANSYS Workbench 17.0 software, and dynamic loading was carried out in the buccolingual bevel of the functional cusp of the maxillary first molar, respectively, to analyze the stress distribution of the surrounding bone tissues under the immediate dynamic loading of bone grafting with or without bone grafting at different alveolar bone heights.
RESULTS AND CONCLUSION: (1) In the groups with different residual alveolar bone heights, the implants showed stress concentration in all stages of the occlusal cycle, which was concentrated in the cervical bone tissue. (2) In the case of bone grafting and non-implanted residual alveolar bone heights, the greatest increase in peri-implant bone stress occurred in the third stage (> 0.150-0.260 s), and in the fourth stage (> 0.260-0.300 s). At the 3-mm residual alveolar bone height, the equivalent force seals for each occlusal stage of the non-implanted group were larger than those of the implanted group. The peripheral bone stress was greater in the third and fourth stages of the 5-mm non-implanted group. At the 7-mm residual alveolar bone height, implantation or no implantation was not enough to cause concern about the distribution of the stresses. (3) In the non-implant group, with the decrease of the remaining alveolar bone height, the range of stress distribution was expanded, and the range of the maximum stress concentration area was more concentrated, especially at 3 mm and 5 mm, the range of stress distribution was not only confined to the neck of the implant, but also extended to the floor of the maxillary sinus. 

Key words: alveolar bone height, implant restorations, maxillary sinus endoprosthesis, dynamic loading, occlusion, stress, bone tissue, bone graft, finite element analysis