The laser reflection method. Computerized analysis of speckle pattern.

The laser reflection method of remote measurements permits registration of small tooth movements. Its precision was investigated by studying the errors associated with patient repositioning in the apparatus using the computer controlled image scanner OSIRIS. Fifty repositionings of healthy subjects were evaluated. The results show that the mean error of repositioning is 2.8 micron laterally and 9.2 micron sagittally. This agrees with earlier manual-visual measurements but the higher precision due to computer evaluation of the speckle patterns gives much more reliable estimate of the repositioning error. The study confirms the fact that the laser reflection method permits accurate measurements of tooth movements.