Pathohistologic Study on the Aging Changes in Human Mandibular Condyle

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  • Kaneko Masayuki
    Department of Orthodontics Kyushu Dental College:Department of Pathology Kyushu Dental College

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  • ヒト下顎頭の加齢的変化に関する病理組織学的研究
  • ヒト カガク トウ ノ カレイテキ ヘンカ ニ カンスル ビョウリ ソシキガク

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Abstract

Changes in the mandibular condyles during the growth period are greatly affected by growth restraint of the mandible due to orthodontic therapy and by displacement of the mandible. Furthermore, advances in the therapeutic methods made the average age of orthodontic patients higher and widened the age range of the patients subject to therapy. A grasp of aging changes of the mandibular condyle therefore has become an important subject in considering the effects of aging on the temporomandibular joint. The author therefore made an observation of localization of cells, centering around the bone and cartilage, of human mandibular condyles, from the new-born to the aged. For the study, non-decalcified specimens of the least damage to the tissue and suitable for a detailed investigation of the tissue were used. Comparison with microradiogram was made for each specimen. The results were as follows : 1. The articular disk up to the teens contained many young fibers and a large number of fibroblasts was observed. In the ages twenties and older, the collagen fibers were found to be arranged closely and the number of the fibroblasts decreased significantly. No increase due to aging in the chondroid cells was observed and tendency for the chondroid to decrease was observed after forty years of age. 2. The collagen fibers in the articular zone became large and close with aging. The fibroblasts decreased and were rather few in the prime of life and thereafter. The chondroid cells were observed scattered near the surface layer, from about three years of age, and did not vary much in number thereafter but decreased in the aged. 3. The proliferative zone was composed of the chondroblasts. The cells decreased with aging and became flat. The chondroblasts ceased to be observed in some locations in the ages twenties and almost disappeared after forty years of age. 4. The hypertrophic zone became rather thin with aging and the collagen fibers were arranged closely. Accompanying this, the cartilage cells decreased and became smaller. These changes appeared markedly in the ages twenties. The cells became rather few after forty years of age and lost the characteristics and disappeared along with the proliferative zone. 5. Halisteresis occurred, in the prime of life, beginning in the surface, in the layer of mineralized fibrocartilage and the layer became rather thin. 6. The subarticular bone was formed completely in the ages twenties but halisteresis occurred shortly, beginning in the surface layer, and osteolysis increased with aging. 7. The bony cortices of the new-born did not show continuity and a significant bone remodeling was observed in the teens. The bony cortices became thickest between late twenties and thirty years of age and became rather thin thereafter. Halisteresis spreaded diffusely in the surface layer of the bony cortices in the ages twenties. 8. The bony trabeculae, in infancy, were thin and short, distributed closely and arranged about parallel with the length of the mandibular condyle. The bony trabeculae grew thicker and longer till the prime of life but became rather thin thereafter and the number decreased. 9. Arteriolosclerosis (elastic intimal thickening or media thickening) was observed in the arteries distributed in the temporomandibular joint in the ages twenties. These changes showed a tendency to be intensified with aging. Based on the foregoings, it is desirable to commence therapy as early as possible and to complete therapy including retention before the patient reaches the age of twenty.

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