The purpose of this study was to measure the physical properties of enamel and cementum of permanent teeth and to determine the correlation between them. This study was conducted on 50 maxillary premolars that were collected from 26 orthodontic patients (10 males and 21 females, mean age: 19.51 years, range: 12-35 years). The hardness and elastic modulus of the enamel and cementum were measured at the surface of the crown and root at three locations (cervical third: CC, middle third: CM, and apical third: CA). There were individual differences in the hardness and elastic modulus of enamel and cementum. The hardness of the cementum decreased from the cervical to apical regions on the root surfaces in the moderate and soft groups (p<0.01). Individual variations were observed in the hardness and elastic modulus of the human first premolar cementum. A correlation was noted between the hardness and elastic modulus of the enamel and cementum in the CA group (hardness: r=0.551, p<0.01, elastic modulus: r=0.552, P<0.01). These results suggested that the physical properties of cementum may be involved in the occurrence of root resorption caused by orthodontic forces.
A robot that supports independent living by assisting with eating and other activities involving the use of the hand using the operator's own hand would be helpful for people suffering from tremors of the hand or any other body part. In this study, the proposed adaptive filter estimates tremor frequency with a time-varying property and individual differences online, and insulates the voluntary motion signal from the sensor signal containing tremor components. As a result, the developed human-machine interface makes it possible for the person with a tremor to manipulate the supporting robot without causing operability to deteriorate and without hazards due to improper operation.
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