16 healthy teeth extracted have been selected and their color and structural change have been observed at the fixed temperatures of $200^{circ}F$., $400^{circ}F$., $600^{circ}F$., and $800^{circ}F$. respectively at the intervals of 10min. 30min and 60min. The results were as follows: 1) $200^{circ}F$ Groop: At the 60 minutes interval, crown surface shows pattern simliars to mottled teeth and roots take on light yellowish colar and interglobular dentin tends to be rough. 2) $400^{circ}C$ Groop: at the 30 minutes interval, cracks begin to show in the direction of long axis of the teeth and crown surface have been observed on the verge of fracture at the 60 minutes interval. 3) $600^{circ}F$ Groop: Crowns take on grayish-white color thoroughout 10, 30 and 60 minutes intervals and roots reveal black color. Moreover the seperation of enamel from dentin has been confirmed at the 60 minutes interval and inner dentin has changed black. 4) $800^{circ}F$ Groop: Crowns take on the same grayish-white color as at the $600^{circ}F$ at the 10, 30 and 60 minutes intervals and roots reveal gray color at the 30 and 60 minutes intervals, while parts of the crown have fractured at the 10 minutes interval. Inner dentin has turned gray at the 60 minutes interval.