2023, Vol. 27 ›› Issue (7): 985-991

Biomechanical analysis of All-on-Four and pterygomaxillary implants under different maxillary bone conditions

Zhu Lin1, 2, 3, Gu Weiping1, 2, 3, Wang Can4, Chen Gang1, 2, 3   

Abstract: BACKGROUND: Implant fixation has become a more satisfactory repair method for patients. All-on-Four and pterygomaxillary implants can meet the implant requirements under certain conditions. At present, there is no biomechanical comparative analysis of the two schemes under different bone quality conditions.
OBJECTIVE: To explore the appropriate implant scheme, three-dimensional finite element analysis was used to compare the stress distribution of All-on-Four and pterygomaxillary implant under different bone conditions.
METHODS: The cone beam CT data of an edentulous patient with severe maxillary bone deficiency were selected, in order to set up physical models with three kinds of cortical bone thickness (1.0, 1.5, 2.0 mm) and two cancellous bone densities (high density, low density). For each model, All-on-Four and pterygomaxillary implant schemes were designed respectively. A total of 12 models were established and 200 N vertical static forces were applied to the bilateral posterior teeth to calculate the von Mises stress values of implants and cortical bone, together with the deformation of titanium framework.
RESULTS AND CONCLUSION: (1) The von Mises stress values of implants and cortical bone were at the most distal site and the deformation of titanium framework was at the distal end of the stent in All-on-Four and pterygomaxillary implant designs. (2) Under the same cancellous bone density, the von Mises stress values of implants and cortical bone and the deformation of titanium framework were the highest in 1 mm cortical bone, and decreased with the increase of cortical bone thickness in All-on-Four and pterygomaxillary implant designs. (3) Under the same implant design, the von Mises stress values of implant, cortical bone and the deformation of titanium framework were larger in low-density cancellous bone than those of high-density cancellous bone. (4) Under the condition of the same bone, the von Mises stress values of implant, cortical bone and titanium framework deformation in pterygomaxillary implant group were lower than those in All-on-Four group (P < 0.05). (5) The results showed that the increase of cortical bone thickness and cancellous bone density could reduce the stress concentration of implants and cortical bone and the deformation of titanium framework. From the perspective of biomechanics, the pterygomaxillary implant was more favorable for long-term prognosis than All-on-Four.
Key words: All-on-Four, pterygomaxillary implant, three-dimensional finite element analysis, maxillary edentulous jaw, implant fixed restoration