['To study the effects of the cold-light bleaching technique on crystals and microstructure of the dental enamel.', 'The human premolars extracted for orthodontic reasons were treated by a standard cold-light bleaching procedure. After the treatment, all samples were detected by high resolution micro-area X-ray diffractometer, Fourier transform infrared spectroscope and scanning electron microscope.', "After the permanent teeth were treated with cold-light bleaching technique, the enamels' crystal dimension, crystallinity decreased and irregular surfaces and shallow disk pits appeared."] Do [ Effect of cold-light bleaching technique on human permanent teeth enamel surface ]?