A thorough knowledge of the morphological characteristics and the sizes of the human natural teeth will be of an important reference in prosthetic restoration of the teeth. If dental crown surface area can be accurately determined, the knowledge, together with that of the dental root surface area, will be of value in ascertaining masticatory requirement. Measuring the dental crown surface, however, is difficult because the forms of the dental crowns are irregular and uneven. The author, therefore, examined a silver-plating measurring method for irregular shaped test pieces. A preliminary experiment was conducted with 60 regular-shaped measurable test pieces comprising 6 varieties each of two types and modifications were made on the method. A total of 140 extracted natural teeth, 14 pieces each from each position, were measured by the modified method. The results obtained were as follows : 1. Duplicates of the test pieces to be measured were mode with epoxy resin and non-electro and electoro plating were done on the surface. The surface areas (A) was obtained by applying to the formula A≒K/w・r, the value ascertained of plating weight (K), plating thickness (w), and specific gravity of plating (r). 2. The surface areas of the duplicate test pieces were measured by the modified plating method and the measurements were compared with the theoretical values calculated mathematically in advance. An average error of 0.6% was obtained as a result. 3. The crown surface areas were : of the upper jaw, central incisor : 242.3mm^2, lateral incisor : 195.8mm^2, canine : 229.0mm^2, first premolar : 226.6mm^2, second premolar : 203.0mm^2, first molar : 344.1mm^2, and second molar : 312.4mm^2. Of the lower jaw, central incisor : 146.0mm^2, lateral incisor : 155.0mm^2, canine : 187.9mm^2, first premolar : 190.0mm^2, second premolar : 184.3mm^2, first molar : 351.3mm^2, and second molar : 314.4mm^2. 4. The ranks of sizes in descending order were : of the upper jaw, first molar, second molar, central incisor, canine, first premolar, second premolar, and lateral incisor. Of the lower jaw, first molar, second molar, first premolar, canine, second premolar, lateral incisor, and central incisor. 5. The first and second molars of the lower jaw showed greater values than the corresponding teeth of the upper jaw. For the other positions, those of the upper jaw showed greater values.
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