Polarized and transmitted light microscopic study of enamel after microabrasion

The purpose of this study was to observe microabraded enamel surfaces after various applications of Prema to evaluate the mineralized, dense outer-enamel layer. The loss of enamel during the manual method was also compared to that resulting from the mechanical method. Twenty-four intact, freshly extracted maxillary incisors were randomly divided into four groups: five applications, 10 applications, 15 applications, and 20 applications. Each group was further subdivided into manual or mechanical application. Round cavity preparations (about 3 mm) were made in the mesial or distal half of the facial surface and obturated to serve as a reference point. The compound was applied for 5 seconds, rinsed with tap water for 10 seconds, and air-dried, and applications were repeated. Manual applications were performed with a Prema Hand Applicator. After the prescribed applications, the teeth were sectioned mesiodistally. Enamel losses were measured by computer image analysis. No statistically significant difference was observed between the manual and mechanical techniques. The sections were further polished down to approximately 100 um thick and examined with polarized and transmitted light microscopy and microradiography. None of the sections showed the highly mineralized region that has been reported in previous studies. The dark superficial region reported elsewhere probably is an artifact caused by the Edge effect of thicker enamel sections.