Abstract: Summary Laminagraphs were made of each temporomandibular joint of 20 subjects (1) with the mandible forcefully retruded to centric relation and (2) with the mandible positioned by a closing force while an anterior guidance prosthesis was being used. The radiographs were compared by measurements of condylar position; results indicated the condyles to be significantly more superior in the glenoid fossa when anterior guidance was used. The difference in anterior-posterior positioning of the condyles appeared to occur randomly. Measurements of the joint spaces with the mandible in centric relation using anterior guidance indicated that mandibular condyles were not centered in the fossae. There seemed to be a range in the size of the space that could be considered normal.

Abstract: A study was conducted that compared three arbitrarily located axes to the true hinge axis location on ten subjects. Of the 60 different arbitrary axis locations registered, 55% were within 6 mm of the true hinge axis. The results of this study revealed very small differences between a hinge axis face-bow. Hanau 132-SM face-bow, and the Whip-Mix ear face-bow. A linear deviation range of 0.116 to 0.268 mm is of doubtful clinical significance to complete denture construction. If an articulator like the New Simplex is used without a face-bow and with a 3 mm interocclusal wax record, it can be anticipated that there will be a 1 mm deviation in the anterior direction in centric occlusion. This discrepancy, incorporated with errors due to processing, can be eliminated by remounting the finished complete dentures with a new centric relation record for occlusal correction.

Abstract: Various types of acrylic resin therapeutic prostheses commonly used in the treatment of TMJ dysfunction-pain syndrome were described. Each design was related to recent data concerning optimum condylar positions in the fossae, the physiologic condylar suspension system, and individual treatment objectives for repositioning the mandibular condyles. For example, alteration of the vertical dimension of occlusion is a popular treatment procedure that is empirical in nature and is usually used without TMJ radiographs or a differential diagnosis. It can violate the physiologic requirements of the interocclusal distance or the speaking space and does not necessarily move the condyles forward as has been commonly thought. The dangers of empirical treatment procedures for a multicausal dysfunction syndrome have been pointed out. An example was cited where the mandible was moved forward for a long period of time with a repositioning prosthesis; this produced pathologic TMJ remodeling and continued pain. It was recommended that specific mandibular repositioning be based on the type of condylar displacement observed on the radiographs. Sometimes the condyles should be retruded, and other times they should be repositioned anteriorly or occasionally inferiorly on one side. Long-standing use of any acrylic resin repositioning prosthesis is contraindicated, particularly without close supervision. Acrylic resin anterior bite plates (with a minimum opening of 1 mm) were recommended for the relief of acute trismus or intractable pain. Usually the prosthesis is used in conjunction with heat and drug therapy. This type of prothesis can also be utilized to deprogram the muscles when a strong habit of eccentric occlusion develops as a result of missing teeth. (This should be confirmed by TMJ radiographs.) Occasionally atypical pain is present and a differential diagnosis can be established between TMJ dysfunction or neurologic etiology by the physiologic response to bite plate therapy. When it is necessary to reposition the mandibular condyles anteriorly the occlusion is adjusted to provide the planned anterior movement without increasing the vertical dimension of occlusion. A temporary acrylic resin prosthesis is used to retrain the muscle programming to the anterior therapeutic mandibular position. When the symptoms are relieved and the corrective condylar position is confirmed with TMJ radiographs, a more permanent repositioning prosthesis is made. The treatment of TMJ dysfunction-pain syndrome should be based on documented data including the pain history, TMJ radiographs, condylar position in the fossae, electromyographic evidence, and occlusal analysis. This information will help determine if the patient's centric relation is functional or dysfunctional and will indicate the recommended treatment procedures.

Abstract: Summary The postinsertion problems of complete denture prostheses are closely related to accurate recording of maxillomandibular relationships. It is essential that these recordings be made with stable record bases; making the final impressions within the record bases prevents movement and tilting. Face-bow and centric relation records properly orient the casts in the articulator. A method to obtain all of these records in one dental appointment has been described.

Abstract: When recording and transferring centric relation onto an articulator errors can be minimized by proper use of dental materials. Remaining errors may be due to either the patient or the clinician. 3 recording techniques (Lucia, Dawson, Ramfjord) are being tested by 2 operators on 12 patients. In order to get a proper centric relation one must not rely upon a technique of taking it but rather on an adequate clinical evaluation of the TMJ at that moment. The role of inadequate intermaxillary relationship upon painful TMJ syndroms cannot be underestimate.