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Keypoints labelled on the lip video. Dotted line indicates mucosal border on the lower lip that makes contact with the upper lip when the mouth is closed. A and B—commissures; C and D—centre of the upper and lower lip, respectively (defined by philtrum midpoint and not necessarily equidistant from A and B); E—equidistant from A and C; F—equidistant from A and D; G—equidistant from B and C; H—equidistant from B and D.
