Determination of the physiologic equilibrium point of the mandible by electronic means

The location of the physiologic equilibrium point of the mandible was determined by electronic means while the subjects clenched their teeth in centric relation with a force of 24 pounds. A total of 20 occlusal relationships were observed. In 14 Angle's Class I occlusal relationships, the equilibrium point, when projected at right angles to the midsagittal plane, was observed lined up within the mesial third of the mandibular first molar. In four Angle's Class II occlusal relationships, it was lined up within the distal half of the mandibular second premolar; and in two Class III Angle's occlusal relationships, it was lined up within the middle third of the mandibular first molar. When referenced to the maxillary arch, 16 occlusal relationships lined up within the mesial third of the first molar and four within the distal half of the second premolar. In the coronal plane, the equilibrium point was estimated as being in or close to the midsagittal plane. The biomechanical significance of the equilibrium point was discussed. The location of the equilibrium point was expressed mathematically using a model of the mandible as a beam on resilient supports. Further studies considering the clinical significance of the equilibrium point in relation to centric occlusion registrations and orthodontic treatment are suggested.