A biomechanical analysis of the human maxilla-zygoma complex

Objective: Force distribution along the maxilla-zygomatic bony complex in human dentate and edentulous patients has received little theoretical biomechanical analysis. Methods: A free-body diagram applies vectors of all forces acting on a rigid body in equilibrium. Force magnitude, angulation and direction are indicated graphically on the diagram. The human maxilla-zygoma complex is assumed to act as one rigid body. This complex is modeled in the frontal and sagittal plane radiographically to comprehensively understand the mechanical distribution of forces within the system. Results: Results indicate that in the frontal view force decreases at frontomaxillary suture and force at the frontozygomatic suture increases as the bite position moves from the incisor posteriorly to the molar. In the saggital view, the force is compressive but decreases at the frontomaxillary suture as the bite position moves from the premolar bi-directionally toward the molar and central incisor. The force during a molar bite at the frontozygomatic suture is highly compressive but is zero when the bite force is over the premolar. During an incisal bite, the forces at the frontomaxillary suture are tensile and of slightly greater magnitude than the compressive forces at this suture produced during a canine or central incisor bite. The edentulous model in both the frontal and sagittal view results in the same pattern of forces although the magnitude of forces is four times less than the dentate force magnitudes. Conclusions:This information can be used to further study the biomechanics and inherent masticatory forces of the human midface and contribute to the understanding of forces on the maxilla-zygoma complex in normal dentate patients especially during growth and edentulous patients after the loss of their dentition.