The relationship of upper facial proportions and the plane of occlusion to anatomic reference planes.

A study was made of 28 dentulous Chinese (Singaporean) adults by using lateral skull radiographs. The dimensions of the maxillae and various craniofacial reference lines related to prosthodontic use were analyzed. The craniofacial reference angles that reflect the vertical height and horizontal depth of the maxillae in Chinese adults differed significantly from the norms obtained in a white North American adult population. By comparison, Chinese adults have a vertically high and horizontally receded upper face that could cause planes such as the Frankfort horizontal plane or an arbitrary axis-orbitale plane to assume a steeper anterior inclination, thus modifying the mechanical inclination of the maxillary cast and occlusal plane on the articulator.