Age changes of the periodontal ligament of the molars were studied by morphometry using senescence accelerated mouse. These mice were from 2 to 16 months of age, and of both the resistant strain (SAMR1/Iw) and prone strains (SAMP2/Iw and SAMP8//Iw). The width and the cell number of the periodontal ligament at four parts of the maxillary first molar (M1), namely the mesial side of the mesial root (M), distal side of the distal root (D), furcation of Ml (F), and apex of the mesial root (A), were examined under light microscopy using IBAS-2000. Then, the numbers of epithelial rest of Malassez and of cementicles were counted in the periodontal ligament surrounding the mesial root and the distal root of the maxillary M1. Mean scores of the histological parameter were calculated, and the strain and age differences were statistically analyzed by analysis of variance.
The width and the cell number of the periodontal ligament were different according to the parts. No strain difference was seen in the width of the periodontal ligament at all four parts. At (M) and (A), the width of periodontal ligament did not change with age, but it decreased at (D). At (D), it was significantly different for 2 and 16 months of age in each strain. At (M) and (F), the cell number in the periodontal ligament did not change, but it tended to increase at (D). At (A), the cell number was slightly higher at 2 months of age in all strains, but thereafter they showed the same value throughout the experimental period. The epithelial rests of Malassez were often seen at the neck and the furcational area of the periodontal ligament. The numbers of epithelial rests of Malassez did not show any strain differences, and they were high in the young group and decreased with age. Cementicles were often observed in the apical periodontal ligament of the root. The numbers of cementicles also showed no strain differences, and increased with age.

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During dental treatment, accidents may happen. In this repotrt, we describe a case of acci dental swallowing of a metal core after aspiration.
The patient was an 80-year-old male. He accidentally aspirated a metal core. He had no symptoms except slight coughng. However we requested chest and abdominal X-Rays, as his reflex might be weak. A wax model of the metal core was brought to the hospital so that the doctar could its shape. The diagnosis was a dental foreign body in the reght middle bronchial tube B6.
The next day the patient was admitted to the hospital for removal of the foreign body. Though bronchoscopy was performed under general anesthesia, the metal core was not found, but only a bleeding point and a clot. Next, the metal core was identified in the stomach by abdominal X-ray. The patient seemed to have expectorated the metal core and swallowed it again in the night.
We conclude that the dental practitioner should prevent the accidental aspiration of dental foreign bodies.
If it happens, we should be prepared to handle the situation.

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[in Japanese]

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Japanese live longer and require dental services for more decades of their life than ever before. Disposable insome available for dental services has risen steadily, even though people have a reduced average income during their retirement years. Through education and financial stability, people have become increasingly concerned with their oral health. Elderly Japanese are now more able and willing to make significant investments in oral health care. In Japan, dentists are paid on a fee-for-service system. Insurance covers the majority of officially authorized dental procedures. But special procedures, such as orthodontic and prosthodontic care, are paid for by the patient. The purpose of this study was to investigate the differences in dental health beliefs between wearers of insurance-provided removable dentures and wearers of other removable dentures. A total of 182 patients with removable dentures who attended the Prosthodontic Clinic of Showa University Dental Hospital were interviewed before an oral examination. We found no significant differences in dental beliefs between wearers of insrance-provided dentures and wearers of other dentures except in denture-cleaning habits. The results suggest that patients with non-insrance-provided dentures should be more concerned about their remaining teeth.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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