The present study was so designed to evaluate the change of topesthesia based on the degree of resorption of deciduous teeth and the grade of root formation of permanent teeth. A total 12315 teeth (6140 deciduous teeth and 6175 permanent teeth) from 311 boys and 364 girls, whose ages ranged from 3.9 to 17.2 years (average 8.3 years) were examined. After taking dental X-rays, 20 g of pressure was applied on the axially direction on each tooth, and then the child was requested with his index finger to identify which tooth was perceived to be pressed. A specially designed tooth pressing device was used. For reference, the measurement of the root surface was made on an extracted tooth using a digital image analyzer (MAGISCAN-IIA). The followings were the results obtained in the present study. 1) The topesthesia of the teeth was found to be more accurate in mesially located teeth than in distally located teeth. Some children falsely indicated the mesially located teeth. 2) The topesthesia of deciduous teeth was increased more as the resorption of the teeth was progressed. 3) The topesthesia of the permanent teeth decreased as the root formation developed. 4) Negative correlation was noticed between the topesthesia and amounts of the root surface remaining. (Correlation coefficient of upper jaw -0.94, lower jaw -0.89).