Abstract
Purpose: Atraumatic, oscillating ultrasonic instruments have recently been developed for prosthodontic margin finishing. This in vitro observational pilot study aimed to compare the condition of crown preparation margins finished using new ultrasonic instruments with margins finished with conventional rotary instruments. Methods: Two extracted human canine teeth were prepared for crowns. A split-tooth model was used to refine the margins: half of the margin was finished with conventional rotary instruments, the other with ultrasonic instruments. The profiles of the margins were observed using scanning electron microscopy, and a quantitative comparison of surface roughness was obtained using surface roughness analysis software. Results: The margins finished with the ultrasonic instruments exhibited a better-defined axial wall/margin angle and a smoother marginal surface. Rotary instruments produced a sharper and more continuous external line angle. Two-dimensional surface roughness analysis showed that the margins produced with the ultrasonic instruments were approximately half as rough as the margins prepared with the conventional rotary instruments. Conclusion: The ultrasonic instruments produce margins in better condition than the current standard and appear to have some practical advantages.