Effect of etching times and mechanical pretreatment on the enamel of primary teeth: an SEM study

The purpose of this SEM study was to evaluate the micromorphology of the enamel of primary teeth etched for 15, 30, 60 or 120 seconds, with or without previous mechanical pretreatment. A total of 40 non-carious primary teeth were used. One half of the facial surface of each tooth was ground with a #169 diamond bur mounted in a high-speed handpiece. The other half was left intact. A 37% phosphoric acid gel was applied with a small brush to the facial enamel and left undisturbed for 15, 30, 60 or 120 seconds. Each group had 10 teeth. All teeth were examined under the SEM. The results revealed that etching time had no significant effect on the micromorphology of the enamel surface of primary teeth. Grinding the enamel with the diamond bur before etching produced a uniform distribution of prismatic structure regardless of the etching time. If the enamel surface was not ground, a "coral-like" porous retentive surface was apparent in most of the cases with no defined prismatic structure. The term "coral-like" enamel is a better descriptor of the etched "prismless" enamel surface while observed under the SEM.