Understanding graphic records of mandibular movements

Abstract

1 wo methods of recording maxillomandibular relationships in eccentric movements or positions are commonly in use. They are the positional or interocclusal registrations, and graphic recordings. Positional registrations aim to record eccentric relations of the mandible to the maxillae which correspond to certain border mandibular movements, either protrusive or lateral ones. The graphic recordings give an indication of the movements of the mandible along the entire course of the recording, and therefore are more desirable. To attain the ideal condition, the graphic recordings should be scribed at the very place where the movement is initiated; that is, within the temporomandibular joints. However, in many instances, the recording represents a projection of the movement over a definite recording plane that is located at some distance from the joints. Since the recording surfaces do not coincide with the actual planes of movement within the mandibular joints, the tracing represents a combination of movements which cannot be interpreted as the trajectory of the sought-after point. As a result, dentists may be led to wrong conclusions regarding mandibular movement. It is the purpose of this article to analyze graphic recordings in order to disclose a correct clinical evaluation of the information obtained by them.