Vertical Dimension, Jaw Relation Records and Occlusion

Abstract

The problems of vertical dimension, jaw relation records and occlusion are complex, and they involve a complete study of what is commonly called the stomatognathic system. There are many methods available for the determination of the correct vertical dimension. Some are dependent on measurements, some on phonetics, others on cephalometrics and still others on tactile sense. The reliability of any of these methods may be questioned because there is no scientific proof of their accuracy, but their true value lies in the fact that they are aids which will help to resolve the problem of vertical dimension. Free-way space and physiologic rest position are the most sought-after aids in the establishment of the desirable vertical dimension for the edentulous patient. The use of jaw relation records is predicated on the fact that the maxillary cast has been properly oriented to the articulator so that the maxillary cast has the same relation to the temporomandibular articulation as it does in the mouth. This is accomplished through the use of the facebow. Jaw relation records generally fall into two main classifications, the interocclusal method and the tracing device method. To obtain the most accurate results from either method necessitates a knowledge of their limitations, advantages, and disadvantages. The complexity of the problem of occlusion has been stressed. The more important factors in the development of the occlusal scheme have been emphasized. Some of the more important points are these: 1. The movements of the temporomandibular articulation are many and varied. 2. The muscles of the body, to be in a state of equilibrium, must be at their true physiologic resting position or in a state of isotonic contraction. 3. Vertical dimension of rest and vertical dimension of occlusion are not one and the same. 4. The composition of bone is such that it cannot withstand a sustained force. Dentures must be constructed with a separation of the teeth when the mandible is at rest, and the teeth must be so positioned as to create forces of occlusion that are favorable to the bone, to prevent rapid resorption. 5. The plane of occlusion should be so positioned that favorable leverages will be exerted on both arches. 6. Centric relation and the hinge axis are considered a terminal position, but to call the rest relation a terminal position would be incorrect. 7. Centric relation is found at the apex of the needlepoint tracing. Patients may also have formed a habit, or functional relationship. With patients who have an acquired or functional eccentric relationship it is not advisable to lock the occlusion to the apex. This may be accomplished by allowing the teeth to gain an additional range of horizontal movement without engaging the inclined planes. 8. Cusp teeth, with their thickness of occlusal pattern and cuspal inclinations, lend themselves well to the establishment of occlusal balance and the reduction of traumatic forces to the underlying bone. 9. Flat teeth, lacking cusp height and inclination, will not be a factor in the reduction of trauma in denture construction. 10. Balanced occlusion means an equalized contact between masticating surfaces within their functional range, which will include centric and eccentric movements. 11. The eccentric movements of the mandible are controlled by condylar guidance, incisal guidance and Bennett movements. 12. The balancing factors for eccentric movements are the plane of orientation, compensating curve, cusp height and inclination. 13. Each patient is an individual in regard to age, sex, physical, mental, and physiologic factors. This obviously means that no one stereotyped pattern of tooth with an arbitrary degree of cuspal inclination will satisfy the needs of all patients.