Distribution of stress patterns in the human zygomatic arch and bone

A three-dimensional photoelastic model was reproduced from a human skull. The insertions of the superficial and deep portions of the masseter muscle and the temporalis fascia were simulated with leather bonded to the appropriate areas. The following loading conditions were employed: (1) bilateral loading of the masseter muscle; and (2) bilateral loading of the masseter muscle together with a bilateral occlusal load. Ther stress freezing technique was used to lock the resulting stress patterns into the model skull. The stress trajectories were observed and photographed in a circular polariscope. The results suggest that the major stress trajectories to the zygomatic bone and arch follow an alveolo-maxillary-zygomatic-temporal direction. Stresses were highly concentrated in the zygomatic process of the temporal bone. Generally, the stresses were concentrated in those areas of the bone where architectural reinforcement had been demonstrated by other methods.