## 1 Introduction  
In reconstructive surgery of extensive mandibular defects, implants predominantly made of titanium are used, which are custom-designed thanks to the widespread adoption of CAD/CAM technology. Implant design aims to achieve stiffness comparable to bone by reducing the stiffness of metal implants, whose material has an elastic modulus several times greater than that of bone tissue. Cortical bone exhibits an elastic modulus between 8 and 20 GPa, whereas titanium has an elastic modulus of 100-120 GPa. An excessively rigid implant leads to bone overload in the bone screw regions and simultaneous underloading in areas where the implant, rather than the bone, transfers the load. This results in bone resorption from both causes. Reducing implant stiffness improves load distribution to the bone, which can be achieved by adjusting the wall thickness or decreasing the elastic modulus. Additive manufacturing technologies allow the use of metals or polymers with low elastic modulus and enable the production of thin walls, shortening the extent of osseointegration with the bone for lattice structures and cellular materials. These solutions are currently very popular and clinically applied due to their expected beneficial effects on load distribution. The most severe clinical failure is mandibular prosthesis fracture; therefore, the design and manufacturing of bone implants require strength analysis to ensure that reducing stiffness does not compromise the required load-bearing capacity. The most effective method for assessing implant load-bearing capacity is numerical simulation [1, 2].  
However, the accuracy of the analysis depends on boundary conditions, including loading and support conditions of the model, as well as material properties. In the case of the mandible, it is crucial to replicate occlusal loading conditions in the model, especially the oblique forces associated with mastication.  
Current mandibular implant design lacks the application of previous research findings that highlight the significance of asymmetric occlusal load transfer in the mandible. [PERSON] et al. [3] demonstrated that occlusal loads are transferred asymmetrically, with the balancing-side joint being significantly more loaded. It was noted that if the greatest bite force occurs on the left side, the contralateral joint on the right side bears the highest load. A clinical study confirmed a greater reduction in temporomandibular joint (TMJ) space on the balancing condyle compared to the working condyle during mastication, with intra-articular distances significantly increasing for bolus thicknesses between 5 and 15 mm. The study showed that despite the absence of support in one joint due to fracture and loss of the mandibular head, bite forces within the normal range can still be generated. However, previous simulation studies have employed an overly simplified occlusal force model, considering only forces perpendicular to the occlusal plane. The current mandibular implant design lacks the application of findings that underscore the importance of asymmetric occlusal load transfer [4, 5].  
The objective of this study was to evaluate, using the Finite Element Method (FEM), the load-bearing capacity of a mandibular prosthesis under unilateral joint support contralateral to the occlusal side while generating a lateral oblique masticatory force. The hypothesis of this study was that the load-bearing capacity of extensive mandibular prostheses is significantly underestimated when assuming mandibular support in the joint on the occlusal side, compared to the assumption of a perfect osseointegration between the implant and the bone. FEM simulations of occlusal load transfer considered two TMJ's support scenarios: one with both joints supported and another with only the joint opposite to the bite side supported. Additionally, the influence of bone ingrowth or its absence at the implant interface was examined.