Study on Diagnosis of Incipient Dental Caries at Fissures and Grooves

Utilizing remarkable difference of electric resistance between enamel and dentin, the thickness of enamel at the fissure parts was presumably measured. It was studied whether the morphologic and pathologic conditions at the fissure parts of extracted or vital teeth were judged by this measurement.<BR>The following results were obtained;<BR>1. The electric resistance of the teeth covered with enamel is rather high (4MΩ to ∞) . It becomes, however, lower and lower, with removing enamel from the tooth surfaces and is reduced in proportion to the thickness of enamel. When dentin is exposed, the resistance is keeping approximately constant value.<BR>2. It is clear by the experiments on 109 extracted teeth that the electric resistance of teeth depends upon their morphologic and pathologic conditions. The highest value is showed at the normal fissures (G) and the value is decreased with the order of the deep fissures (F₁), flask-typed fissures (F₂), enamel caries (C₁), the perfect tissues (F₃) and carries reached to dentin (C₂) . The electric resistance is varied by the thickness of enamel at the basis layer under fissures.<BR>3. When the morphologic and pathologic conditions are divided, by covering states of enamel under fissures, into such 3 groups, as G and Fl group (I), F and Cl group (II) and F₃ and C₂ group (III), the mean value of electric resistances of each group are, 2874, 1842 and 334 KΩ respectively. The difference among them is significant.<BR>4. The electric resistances are measured on 866 molars of 90 males and females, aged from 18 to 47 years. The average values of clinically healthy teeth, 132 incipient carious teeth (C₁) and apparent carious teeth (C₂) are, 1299, 276, and 63 KΩ respectively. There is a significant difference between the average value of healthy teeth and that of incipient carious teeth.<BR>5. 666 molars of 71 people, aged from 19 to 44 years are observed for 2 to 3 years. Of these teeth, 148 teeth showed the electric resistance below 280 KΩ, and 518 teeth above 290 KΩ. The caries attack rate of the former is 45.9 per cent and that of the latter 8.3 per cent.<BR>6. It is concluded that the value of electric resistance at fissures of molars can be apparently applied to the determination of morphologic and pathologic conditions at the fissure parts and that the caries attack rate can be judged by these value.