PURPOSE: The purpose of the first phase of this two-part investigation was to determine if the opening motion of the mandible could be illustrated and described using a dynamic imaging method. The purpose of the second phase of the investigation was to determine if a center of rotation would be discovered. MATERIALS AND METHODS: Five volunteer subjects, 2 female and 3 male, whose temporomandibular joints had previously been determined to be asymptomatic, were examined by magnetic resonance imaging (MRI) during opening from a standardized position. The serial static images were reconstructed by the MRI's computer in "cine mode" to simulate dynamic motion, similar to a motion picture. For the second phase, each patient's series of static images were digitally added and manipulated by a computer graphics program to locate the center of hinge motion. RESULTS: After reviewing the animated images recorded on videotape, three independent dentist observers confirmed that the opening movement of the mandible was initially rotational, followed by translation within the glenoid fossa. A center of rotation was calculated to be in the anatomic center of the condylar head of all of the subjects in this study. CONCLUSIONS: This study showed that opening dynamics of the mandibular condyle could be studied by cine-MRI and that an opening hinge axis appears to be located in the anatomic center of the condylar head.
PURPOSE: The purpose of the first phase of this two-part investigation was to determine if the opening motion of the mandible could be illustrated and described using a dynamic imaging method. The purpose of the second phase of the investigation was to determine if a center of rotation would be discovered. MATERIALS AND METHODS: Five volunteer subjects, 2 female and 3 male, whose temporomandibular joints had previously been determined to be asymptomatic, were examined by magnetic resonance imaging (MRI) during opening from a standardized position. The serial static images were reconstructed by the MRI's computer in "cine mode" to simulate dynamic motion, similar to a motion picture. For the second phase, each patient's series of static images were digitally added and manipulated by a computer graphics program to locate the center of hinge motion. RESULTS: After reviewing the animated images recorded on videotape, three independent dentist observers confirmed that the opening movement of the mandible was initially rotational, followed by translation within the glenoid fossa. A center of rotation was calculated to be in the anatomic center of the condylar head of all of the subjects in this study. CONCLUSIONS: This study showed that opening dynamics of the mandibular condyle could be studied by cine-MRI and that an opening hinge axis appears to be located in the anatomic center of the condylar head.