[Studies on the causative factors of cervical wedge-shaped defect of human teeth from three dimensions]

To investigate causative factors of cervical wedge-shaped defect of human teeth and the significance of methods for measurement of the defect.

Experimental cervical defects on 9 pairs of premolars were created by cross-brushing, erosion, or fatigue of occlusion force separately or combinedly and measured in depth and area of profile as well as in volume.

1. Profile depth of defects caused by three factors separately showed no statistical difference, but the profile depth caused by combining factors was much more than that caused by each individual factor; 2. The hardness of enamel and dentin in defect area was lower than that in normal area of tooth samples; 3. Measurement from one-dimension (depth) and two-dimension (area) showed only low relation in profile depth, however, measured three-dimensionally (volume) there existed moderate relationship.

For study of cervical defect, the profile depth is feasible provided that is a large sample group and without equipment for volume measuring; if the sample size is limited and there is sophiscated instrument for volume measuring, the 3-dimensional measurement is the most sensitive one.