総義歯床基底面の機能的形態に関する研究

Abstract

In order to make analysis of functional form of full denture, plaster models of 49 edentulous patients were used and denture basal surface was measured by the electroless plating method and projected basal surface by photographs. Alveolar ridge form of the mandibular first molar region which is the main bearing area was expressed numerically and analyzed. Changes in biting force with a decrease in denture basal surface in four subjects were measured by the strain-gauge method and denture basal surface which enables full dentures to function sufficiently was studied. The results were as follows : 1. The basal surface area was 49.9±10.6 cm^2 for the maxilla and 30.1±7.7 cm^2 for the mandlble. The projected basal surface area was 22.6±2.8 cm^2 for the maxilla, 6.0±1.4 cm^2 for the maxillary buccal region, 16.7±1.9 cm^2 for the palatal region, 11.8±2.1 cm^2 for the mandible, 5.7±1.3 cm^2 for the mandibular buccal region, and 6.1±1.3 cm^2 for the mandibular lingual region. The surface area of the lateral retention region which is the difference between the basal surface area and projected basal surface area was 27.3±8.7 cm^2 for the maxilla and 18.3±6.8 cm^2 for the mandible. A highly significant difference was observed between the maxilla and mandible. No significant correlation was observed in the basal surface area between the maxilla and mandible. In projected basal surface, however, significant correlation was observed and the projected basal surface area of the palatal region showed a value three times those of the other parts measured. 2. In the mandibular alveolar ridge form, no difference was observed in every measured item between the left side and right side. However, the buccal height was 4.0±3.2 mm for the left side and 4.0±3.0 mm for the right side, and the lingual height was 5.7±3.1 mm for the left side and 5.3±2.8 mm for the right side. A significant difference in the alveolar ridge height was observed between the buccal and lingual sides for each lateral side. The buccal width was 6.5±1.9 mm for the left side and 6.8±2.0 mm for the right side, the lingual width was 6.5±1.8 mm for the left side and 6.6±1.6 mm for the right side, and the sum of buccal and lingual widths was 13.0±2.5 mm for the left side and 13.3±2.4 mm for the right side. No significant difference in the alveolar width was observed between the buccal and lingual sides for each lateral side. The buccal alveolar ridge angle was 28.6±17.7° for the left side and 28.0±17.5° for the right side. The lingual alveolar ridge angle was 39.3±17.0° for the left side and 37.6±16.0° for the right side. A highly significant difference in the alveolar ridge angle was observed between the buccal and lingual sides for each lateral side and the lingual side was more acutely inclined. 3. The relation between the projected basal surface area and biting force was examined in four full denture patients. The patients complained of poor retention of the bite plate when the maxillary palatal plate was reduced by 20∿45% of the projected basal surface area. The biting force at this point was reduced by 22% or less. Every patient complained of pain when the mandibular lingual region of the plate was reduced by 10∿20% of its projected surface area and further removal could not be made. The biting force at this point was reduced by 20% reduction of the buccal region of the plate by 20∿30% caused a reduction in the biting force by 50%. Based on the forgoings, it appears to be necessary to increase basal surface area, as much as possible, of the mandibular lingual side to relieve pain and of the mandibular buccal side to prevent decrease in biting force.