Observations of Hunter-Schreger bands.

DOURING the process of studying the physical damage and traumatic effects of various instruments on tooth structure, it became apparent that some consideration should be given to the Hunter-Schreger band formation as it exists in enamel structure. When examined by reflected light, these bands appear as alternating light and dark areas in the enamel portion of a longitudinal groundtooth section, starting at, or near, the dentino-enamel junction and passing outward toward the enamel periphery. The Hunter-Sehreger bands have been described generally as an optical manifestation of the direction in which the enamel rods have been sectioned relative to their axis. Despite many detailed studies of these bands, their significance, physical structure, and origin still remain obscure. It was because of the need for a better understanding of the physical arrangement of the enamel rods in human tooth enamel that this examination of the HunterSchreger bands was undertaken. This report will describe the results obtained when a method for examining Hunter-Schreger bands by means of a shadowed replica technic and shadowed tooth sections is employed. This method differs somewhat from the conventional methods which have been used in the past, that made use of examination of etched and unetched longitudinal ground sections with reflected light, or thin sections by transmitted light, and partially decalcified stained sections.