A study of the state and depth of resin penetration into acid-etched enamel

Abstract — The length and cross sectional structure of resin tags formed in the etched enamel of freshly extracted permanent central incisors was studied by floating optical photomicrography and SEM serial photomicrography. Penetration of the etched enamel was enhanced by placing the tooth under vacuum. Floating photomicrography avoided damage to the very fragile resin tags. In general, the tags were 150–200 microns long and in some cases up to 300 microns. They were found to be hollow tubules and not solid rods. The resin tubules had a diameter of 6–7 microns and a wall thickness of 1–1.5 microns.