Measurements of Dental Cast Profile and Three- Dimensional Tooth Movement During

We have developed a system for measuring three-dimen- sional profiles of dental casts and three-dimensional tooth movement during orthodontic treatment. The profile measurement is based on the triangulation method which detects a laser sport on a cast using an image sensor. The system is computer-controlled and designed to achieve the depth and lateral resolutions of 0.05 and 0.1 mm, respec- tively, within a depth range of 25 mm. We have applied our system to measuring three-dimensional movement of teeth, including rotations, during orthodontic treatment. The movements have been obtained by means of three-dimensional registration of tooth profiles using a com- puter between casts serially taken at different stages of the treatment. Measurements over periods of 41 to 190 days on patients have revealed that this technique is capable of quantifying the difference in move- ments due to orthodontic therapeutics.