Comparison of third points of reference of two facebows

Objective: The objective of this study was to compare the difference of third points of reference and the relationship of the maxilla on the articulator and the horizontal plane using an arbitrary facebow and a kinematic facebow.

Method: Eight patients (six men and two women with an age range of 25 and 50) at the University of Texas Health Science Center were selected.  The third point of reference for the Denar (D) kinematic facebow was a point 43mm superior to the distal incisal line angle of the maxillary right central incisor and Nasion was used as the third point of reference for the Whipmix (W) articulator.  A maxillary cast of each patient was mounted on a (D) articulator and a (W) articulator.  The maxillary occlusal plane was established from the lowest point of the central incisal edge to a point at the  mesiobuccal cusp tip of the first maxillary molar.  The measurements of the mounted cast was carried out by extending the lines of the upper member of the articulator (the horizontal plane) and the established maxillary occlusal plane; the angle of the intersecting lines with measured by a protractor.

Result: A significant difference p ≤ 0.05 using paired t-tests was observed between the Denar kinematic facebow and the Whipmix arbitrary facebow.  The angle created with the Denar kinematic facebow was zero and parallel to the horizontal plane.  The mean for the angles created by the Whipmix arbitrary facebow was 25 with a STD Dev 3.5 and a mode of 28 and median 27. 

Conclusion: The (D) kinematic facebow and the  (W) arbitrary facebow are similar, but because of the differences between the location on the face of Nasion and the third point of reference 43mm superior to the central incisor, there was a significant difference when mounting a maxillary cast on an articulator.