Reliability of an ear-bow arbitrary face-bow transfer instrument

Statement of problem. Accuracy of techniques for recording the orientation of the maxillary arch to the articulation of the temporomandibular joints h as been reported. The variability contributed by the dentist and the equipm ent within a technique may also contribute to technical error. Purpose. This study investigated the variability of a group of dentists who used an arbitrary ear-face-bow instrument to mount a maxillary cast. Material and methods. The same maxillary cast on a single experimental subj ect was mounted on an articulator with a common arbitrary ear-face-bow inst rument. This cast was equipped with 4 reference points for the measurement of changes of spatial orientation of the cast, which were determined throug h coordinate measurements with a machinist's microscope. A repeated measure s analysis of variance was used to determine statistically significant chan ges in spatial orientation with a Wilks' Lambda test to compare mean values . Results. A confidence interval of 95% demonstrated that any dentist might e xpect a range of +/-1.2 mm error in using this instrument/articulator combi nation. The 3 dentists did not demonstrate any significant differences in t he spatial orientation of their mountings in the vertical or horizontal dir ections. However, there were significant differences in their mountings in linear distance changes of the patient's posterior right side. Conclusion. A range of inherent error attributable to the operator using th is instrument was recorded.