Surface roughness of restoration margin preparations: A comparative analysis of finishing techniques

This study compared the margin profile and surface roughness created by the tips of four different finishing instruments: fine diamond, dura white stone, tungsten carbide, and ultrasonic diamond-coated tips (UDTs). The aim was to determine which of these instruments produced the smoothest finish and created the most evenly contoured margin characteristics. It was hypothesized that UDTs would produce a rougher dentin surface than a fine diamond bur, that a tungsten carbide bur would provide a smoother finish than a fine diamond, and that the dura white stone would produce an intermediate finish. Forty extracted premolars were divided into two groups. For the first group, a 1.5 x 3.0-mm dentin slot was prepared in 30 teeth using a control 50-μm diamond bur, followed by one of the four finishing instruments. The surface roughness (R_a) was then measured using a surface profilometer and a one-way analysis of variance followed by a post hoc Bonferroni test to assess whether any statistical difference existed among the R_a values. For the second group, shoulder margins were prepared in 10 teeth. They were then refined with one of the four finishing instruments and examined with scanning electron microscopy (SEM). The fine diamond bur created a significantly smoother surface than the control diamond (P < .001), UDTs (P < .007), and tungsten carbide bur (P < .010). The fine diamond was not found to be significantly smoother than the dura white stone. SEM images of the fine diamond showed divoting on the margin floor. The dura stone showed a well-defined, undamaged margin. The tungsten carbide bur created frequent chipping in enamel margins. The UDT specimens showed an inconsistent finish and discrete patches of open dentinal tubules. The fine diamond created the lowest R_a values; however, the dura stone offered efficient finishing and less damage to the margin profile.