Radiographic study on the anterior portion of the neck of the condylar process. Aged-related developmental changes based on Hellman's dental stage

The condylar process is directly and indirectly influenced by the masticatory muscles and the temporomandibular joint, which functions to regulate jaw movement. Age-related changes in the condylar process were found in both external and internal structures. Observation of X-ray profiles afforded identification of areas of interest in the anterior portion of the neck of condylar process. This portion anatomically includes the pterygoid fovea; moreover, the process serves as a terminal for the lateral pterygoid muscle. Rather than directly analyzing bone structure, we made distinct measurements in regions of interest by X-ray image analysis. Subsequently, changes in occlusion during each developmental stage were evaluated. In addition, bone mineral density measurements were performed. Greater growth was recognized in the long axis of the condylar process in comparison to the short axis. The long axis indicated a 2.7-fold increase in ODL (length along the major axis) from the IA period to the VA period; additionally, the total absolute length increased by 3.1-fold. The short axis demonstrated a 2.3-fold increase in ODS (length along the minor axis) from the IA period to the VA period; furthermore, the total average length revealed a 1.9-fold increase. Bone mineral density was highest in the anterior portion (region of interest) and was higher in the posterior portion (cortical bone); than in the middle portion (central bone). Among these 3 areas, density differences became larger as the developmental stage of occlusion progressed. Detailed measurements in the region of interest demonstrated significant increases from the IIC period to the IIIA (B) period, and distinct peak times of increases were observed in bone mineral density: the center bone structure, as well as the posterior cortical bone, showed significant increases between the IIIC period and the IVA period. The anterior border displayed to constant increase with an exception for the period between stages IIIB and IVA. We concluded that the region of interest was mechanically influenced by occlusion, especially by the lateral pterygoid muscle. (author)