In this work the structural behaviour of a mandible considering a unilateral occlusion is numerically analysed by means of the Finite Element Method (FEM). The mandible, considered as completely edentolous, is modelled together with its articular disks, whose material behaviour is assumed as elastic or hyper-elastic. The mandible model is obtained by computer tomography scans. The anisotropic and non homogeneous bone material behaviour is considered and the loads applied to the mandible are those related to the active muscle groups during unilateral occlusion. The results of FEM analysis are presented mainly in terms of stress distribution on the mandible. Because of uncertainty on the determination of the adopted parameters, a sensitivity analysis is provided, showing the way in which the variation of articular disc stiffness and temporomandibular joint friction coefficient has an impact on the mandible stress peak and occlusal force.