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Quantitative morphometric analysis of molar teeth and alveolar bone using micro-computed tomography in aged mice
Ryutaro Ono1, Makoto Abe2, Nobuya Koike3
1Department of Dental Medicine, Graduate School of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, 602-8566, Japan; Department of Physiology and Systems Bioscience, Graduate School of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, 602-8566, Japan.
Objectives:
Irreversible morphological regressions of the teeth or related structures in older people can diminish their overall health. However, research on human aging in dentistry is complicated by several confounding factors. In this study, we conducted a morphometric analysis of the mandibular second molars and surrounding alveolar bone in C57BL/6 mice to evaluate age-related changes in the oral cavity.
Methods:
The animals were divided into five groups based on their age: 4 weeks (juvenile mice; n = 5); 20 weeks (n = 7), 50 weeks (n = 5), 77 weeks (n = 7), and 100 weeks (n = 5); changes were evaluated using micro-computed tomography.
Results:
The molars of juvenile mice had sharp and pointed cusps and presented maximum heights. With age and occlusal wear, the cusp heights demonstrated a significant decrease (up to 75%) until the last stage of life. Conversely, apparent lesions were not observed on the basal portion of the crown, even in the most heavily worn teeth. The roots of the molars continued to grow in length at 4 weeks of age. Alveolar bone resorption begins to occur in middle age and continues throughout life. The proportion of vertical bone loss reached approximately 40% of the entire root length, demonstrating a remarkable increase between weeks 77 and 100.
Conclusions:
Overall, these morphological changes were similar to those observed in humans. Therefore, it might be appropriate to use aged mice as an experimental model for basic and clinical research in geriatric dentistry.
