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Schematic drawings of the effect of head-tilting on the posterior and anterior teeth. Black, blue and red dashed lines represent the source-detector plane, a vertical axis perpendicular to source detector plane, and the longitudinal axes of corresponding teeth, respectively. Yellow fans represent alpha angle of teeth. (a) and b), forward head-tilting increases alpha angle for upper and lower molar teeth. (c) and d), lateral head-tilting increases alpha angle for anterior teeth.
