Criteria for tooth extraction in periodontitis

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Biting force (kg), occlusal contact area (mm<@D12@>D1) and biting pressure (kg/mm<@D12@>D1) were measured using pressure detecting sheets: Prescale<@D1(] SY.encircledR.[)@>D1, to estimate the masticatory ability. 934 of the subjects cooperated in this study.1. Descriptive epidemiology of the masticatory ability: (1)The masticatory ability was mostly explained by number of teeth, and followed sex. (2)In school ages, the most effective factors on the masticatory ability were age and sex, but not tooth-number. (3)The sexual difference of the masticatory ability was observed from the age of 8. (4)The maximum of the masticatory ability was shown around 20-years old, and decreased with the age. (5)Biting pressure increased in the persons who had less than 20 of teeth. It might be over load for the present teeth in the case of the lesser than 20 of teeth.2. Analytical epidemiology of the masticatory ability. (1)The masticatory ability were about 70 per cent for crown bridge wearers, 30 per cent for removable partial denture wearers and 7 per cent for full denture wearers at the base of 100 per cent for the persons having 28 of teeth. (2)No difference of the masticatory ability was observed before and after setting of the crowns and bridges. (3)The reduction of biting pressure was observed after the wearing the removable partial denture. (4)Adaptation for prosthetic apparatus was observed. The masticatory ability increased with time after setting the prosthesis. (5)The masticatory ability of the patients with mobile teeth showed no difference to the subjects without mobile teeth in the matching test in age, sex and the number of teeth.The tooth extraction of mobile teeth results in decrease of the number of teeth. It becomes to lower the masticatory ability. It is suggested that criteria of tooth extraction in periodontal disease should not be settled by tooth mobility.