The normal stiffness of the jawbone is seldom considered, as opposed to the mechanical properties of its individual cortical and trabecular components. Our standpoint is essentially structural, rather than purely material-oriented, as the jawbone is considered as a natural load-bearing structure. Throughout the work, 3 representative sections in the mandible and the maxilla are modelled and compared. Specifically, we evaluate the sections' elastic structural stiffness numerically, according to the recent geometrical classification proposed by Shemtov Yona (2021). Each case is modelled using two extreme configurations for the cortical-trabecular interaction, namely bonded and unbonded. Those two configurations reflect extreme interfacial conditions, though the bonded one is more physical. For the unbonded cases, the structural stiffness is the sum of the individual stiffnesses of the components. By sharp contrast, the bonded case results in a much larger stiffness than that obtained by the simple sum of the individual stiffnesses, indicating a strong synergistic stiffening effect between the components through their interface. We also investigate the role of the elastic moduli, whose reported values vary widely in the literature, emphasizing the role of the trabecular Poisson's coefficient, whose stiffening effect is evidenced when it exceeds about 0.3. The bone's structural stiffness shown here complements the geometrical classification of the jawbone types with a fundamental mechanical/structural property delineating the coupling between the mechanical properties and the geometry. The adopted approach is not limited to the jawbone and applies in principle to other bone types. From a clinical standpoint, the results presented here complement not only the basic mechanical aspects of the geometrical characterization, but also provide a starting point for future studies on dental implant placement and stability, the latter being directly related to the structural stiffness.