Accuracy of an earpiece face-bow

Area of Science:

• Dental Articulation and Biomechanics
• Maxillofacial Prosthetics

Background:

• Accurate transfer of the patient's true hinge axis to an articulator is crucial for prosthetic restorations.
• Arbitrary face-bows are commonly used for hinge axis transfer, but their accuracy is debated.

Purpose of the Study:

• To clinically compare the validity of the Hanau ear-bow for arbitrary hinge axis transfer against the Hanau kinematic face-bow.
• To assess the accuracy and repeatability of the arbitrary hinge axis determined by the ear-bow.

Main Methods:

• A clinical study involving 18 randomly selected patients.
• Comparison of hinge axis locations determined by the Hanau ear-bow and the Hanau kinematic face-bow.
• Statistical analysis of discrepancies in anteroposterior and superior-inferior directions.

Main Results:

• A statistically significant difference was found between the arbitrary hinge axis (ear-bow) and the terminal hinge axis (kinematic face-bow).
• Discrepancies were significant in the anteroposterior direction.
• Only 50% of arbitrary hinge axes were within a 5 mm radius of the terminal hinge axis; 89% were within 6 mm.
• The ear-bow method demonstrated poor statistical repeatability.

Conclusions:

• The Hanau ear-bow is not a statistically valid method for accurately transferring the arbitrary hinge axis compared to the kinematic face-bow.
• Significant anteroposterior inaccuracies and poor repeatability limit the clinical reliability of the ear-bow.
• Further investigation and modifications are required to enhance the accuracy and practical value of arbitrary face-bows.