Cutting efficency of a new diamond bur for tooth preparation

Objectives: The aim of this study is to compare the cutting efficiency of a recently introduced diamond bur (314.S-6878.016, Komet Brasseler) for tooth preparation with its conventional variant (314.6878.016). Both burs have the same diameter, profile and diamond grains (160µm), but the 6878 have a polygonal section at the cutting portion level; this is claimed to have a percussion effect which can improve the hard tissue removal. Materials and methods: four burs from each type have been selected. Tablets made of human tooth fragments embedded in epoxy resin (4 to 1 w/w ratio) were used as test specimens. Their abrasion resistance is about 14% higher than that of the dentin. The burs were mounted on a turbine (Hi-Power M, Castellini) and operated under water spray (50 ml/min) applying a 1 N force interrupted for 0.2 seconds 30 times per minute. Each bur carried out 25 passages on each tablet, which was abraded 0.5 mm in depth and 5 mm in height. Two tablets for each bur were used. Cutting efficiency was measured in µg of material removed per second by weighing the tablets before and after five consecutive passages. After the test, the burs were observed under the SEM. Results: the cutting efficiency of the two burs was similar, 1.130.014 and 1.1280.017 for S-6878 and conventional 6878, respectively. The difference was not significant (P=0.915. However, the S-6878 showed a greater efficiency during the first third of the whole working cycle, whereas the conventional type was better in the last third. Conclusions: the polygonal S-6878 bur is very effective during the initial phases of tooth removal, but the crystal loss probably occurs very early, leading to a rapid decrease of the efficiency. The crystal loss, confirmed by SEM observation, is probably due to the high stress caused by the polygonal design.