A method for tooth surface lustre measurements with a scanning reflectance sensor system is described. A fiber optic light beam of high intensity is projected onto the labial tooth surface. The reflected light at position X is conducted through the same fiber optic to a photodiode, amplified and recorded on an X-Y recorder. Position X is measured by a potentiometer in the rotation center of a rod to which the fiber optic head is attached and which can be moved parallel to the arcade of anterior teeth to be measured. The experimental system allows the assessment of differences in light reflection caused by light scattering resulting from roughened enamel surfaces and by stains.