Observation of the Internal Structure of the Zygomatic Bone by Micro-Computed Tomography

Abstract

The purpose of this study was to use micro-computed tomography to investigate the internal structure of the zygomatic bone, and to evaluate the effects of biting force on the zygomatic bone by comparing the internal structure of this bone between dentulous and edentulous maxillae. In this study, 20 zygomatic bones of dentulous maxillae and 28 zygomatic bones of edentulous maxillae were used (mean age : dentulous maxillae, 72.6 years ; edentulous maxillae, 79.6 years). Specimens were obtained from the skulls of cadavers, from the sutura frontozygomatica, posterior to the sutura temporo-zygomatica, down to the sutura zygomatico-maxillaris. From 2-dimensional slice images, we reconstructed the three-dimensional structure by volume rendering methods using micro-computed tomography. We used two anthropological reference points : jugale (Ju) at the most concave point between the lateral margin of the upper zygomatic bone and the upper margin of the zygomatic arch ; and zygomaxillare (Zm) at the lowermost point of the zygomaticomaxillary suture. We examined the structure of the zygomatic bone at Ju, Zm and the mid-point between Ju and Zm. The dentulous maxillae had thicker trabeculae at these points than the edentulous maxillae. The thicker trabecular structure in the Ju area was especially pronounced in the dentulous maxillae. These findings indicate that stress from biting force influences the trabecular structure in the zygomatic bone. They also suggest that stress in the zygomatic bone is concentrated in the Ju area, because the masseter muscle and fascia temporalis adhere to the zygomatic bone.