Fig. 2

Measurement of the gutter created by the US device and the abrader burr. a) Measurement planes (a-g) to assess the shape of the gutter, started at 3.5 mm apart from the start point. Upper was defined as right side. b) Depth (d) of the gutter on the right side. c) Angle (α) of the bottom at 0.15 mm. d) Cross-sectional area ratio of the gutter was defined as the curetted area “a” was divided by the minimum square area “a + b + c”