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4Robot technology in analyzing tooth removal, a proof of concept69Fig. 6: Comparison of rotations of an upper incisor (21) and upper first molar (16)When compared to the movements during removal of a first upper molar (tooth number 16) on the right side, a difference in movement pattern can be found. This first molar had, as usual, 3 roots. This means that rotation of the tooth is geometrically unfavorable. In Fig. 6, this can be recognized by the flat character of z-axis meaning no rotation takes place throughout the entire procedure. Rotation around the y-axis shows a buccal movement which increases over time. Movement around the x-axis (mesiodistal movement) shows a slight movement towards the mesial side during this buccal movement, which means the tooth is moved in the direction of the opening of the mouth.Forces and torquesWhen explaining tooth removal to dental students, usually one of the first things that is explained is that, the idea of ‘pulling’ a tooth is incorrect. A tooth needs to be ‘pushed’ out. In terms of forces, one could expect a negative force in the tooth’s root axis (z-axis). Fig. 7 shows the forces exerted during removal of a central upper incisor. It can be appreciated that, during the first phase of the treatment, the tooth is actually Tom van Riet.indd 69 26-10-2023 11:59