Split cast discrepancies and arbitrary axis dental cast articulator mounting

Summary Ths split cast technique has been advocated as a useful clinical tool for checking the reproducibility of jaw registrations. As originally described it requires the use of a kinematic face bow. Since the arbitrary axis used with the Whip‐Mix face bow has been demonstrated to be close to that of the kinematic axis, it is feasible that the split cast technique could be used with such a face bow. Casts of ten subjects were mounted with retruded jaw registrations, made at different degrees of vertical separation. The upper casts were mounted using both kinematic and arbitrary face bow transfers, and the accuracy of mating of the split components measured. With the arbitrary face bow, the components of the split cast system only mated when repeated registrations were of exactly the same thickness, i.e. the same vertical dimension. Small differences in vertical dimensions produced the largest errors at the split. Any slight variations in the thickness of the retruded registrations will therefore invalidate the use of the split cast method in conjunction with an arbitrary face bow. The importance of the correct spatial relationship of mounted dental casts for the adequate diagnosis and treatment of a variety of oral and associated masticatory system disturbances is well documented (Lucia, 1961; Lucia, 1964; Celenza, 1973). However, accurate execution of the clinical and laboratory stages is necessary if the required information is to be obtained from articulated casts.