Fig. 6

Analysis of the achieved depths. a The depths achieved by the two experimenters stay under the preset limits of 0.5 mm and 1.5 mm respectively. The less experienced person (Exp. 1) created a slightly but significantly lower depth in comparison to the expert (Exp. 2) when 1.5 mm depth was intended. Thus, the surgical instrument qualifies as secure in use, irrespective of the expertise of the user. b The levels of the inner part of the defects were cleared by the front mill. The results show small deviations from the reference grooves created by the crown mill (Fig. 6a) for both experimenters. Note the scale with steps of 0.01 mm in contrast to (a)