Topography and presence of a smear layer in deciduous molars prepared with high-speed cutting and ultrasonic abrasion: an in-vitro study

Abstract

Objective. The aim of this in-vitro study was to compare the effect of high-speed cutting (HS) with ultrasonic abrasion (US) concerning the internal topography and the presence of a smear layer in a cavity preparation performed in healthy deciduous molars. Material and methods. Seven first deciduous molars were used. Two occlusal cavity preparation were done, one in the medial fossula and another in the distal fossula, which were chosen randomly. One preparation was carried out with a diamond point adapted to the HS system (GI), while a chemical vapor deposition (CVD) point adapted to a US device (GII) was used for the other preparation. Subsequently, all samples (n = 14) were cleaved to observe the inside and then prepared for evaluation using scanning electron photomicroscopy. The internal topography of the prepared cavities was descriptively analyzed. In order to assess the presence of a smear layer, scores were tabulated using the 2000 GMC program and analyzed using the Mann–Whitney test. Results. Concerning the internal topography, the presence of striae was verified in both groups. In the GI group they were finer, found in a greater number, and with narrower spaces between them. In the GII group, the striae were undulating, similar to the effect of wheels on sand, and with wider spaces between them. As regards the presence of a smear layer, there was no statistically significant difference between the groups (P > 0.05). Conclusions. In view of the methodology employed, it may be concluded that cavity preparation with a CVD point in a US abrasion system led to the formation of fewer striae and both devices promoted the marked presence of a smear layer, obstructing dentinal tubuli.