Fig. 3

Buccal boundary projection from scan T0 to T1 and T2 in the direction perpendicular to the mid-sagittal plane a. The scan T0, the red borders outline the upper third of the face and bilateral buccal regions; Obtain T0 right buccal model by “new object from selection”; b. Copy T0 right buccal model and name “ring model”; c-d, Copy line 3 (the normal line of the mid-sagittal plane) to “ring model”; Using “extrude boundary” function, extend the buccal boundary by 10 mm along the positive direction of line 3; e. extend the buccal boundary by 10 mm along the negative direction of line 3; f. delete the buccal boundary in the middle of “ring model” and obtain a complete ring with parallel edges; g. Perform Boolean subtraction between “ring model” and T1; h. Perform Boolean subtraction between “ring model” and T2