"Myo-Monitor centric": an evaluation

Ten patients had three “Myo-Monitor centric” records made at each of three appointments. Terminal hinge axis determination and interocclusal registration of centric relation were used to accurately mount maxillary and mandibular casts on a modified articulator. The characteristics of “Myo-Monitor centric” were investigated by: evaluation of the reproducibility of “Myo-Monitor centric” records; comparison of “Myo-Monitor centric” position to centric relation contact position and centric occlusion; comparison of the tooth contact on hinge closure from “Myo-Monitor centric” with centric relation contact; evaluation of the effect of the anteroposterior head position on the number and location of tooth contacts during “Myo-Monitor centric” mandibular closure; and a comparison of the anteroposterior relationships among “Myo-Monitor centric,” centric relation, and centric occlusion.Examination and appropriate statistical analysis of the data revealed several characteristics of “Myo-Monitor centric”: The axis of rotation determined by “Myo-Monitor centric” was always anterior and inferior to the patient's terminal hinge axis; “Myo-Monitor centric” registrations within individuals were non-reproducible; with “Myo-Monitor centric” registrations, centric relation contacts on the mandible were anterior to both centric relation and centric occlusion contacts on the maxillae; variation of anteroposterior head position affected Myo-Monitor-produced mandibular closure; and eight of ten patients had “Myo-Monitor centric” contact anterior to their centric relation contact.