Effect of lateral cranial base surgery on temporomandibular joint function.

Temporomandibular joint (TMJ) function in patients who experienced lateral cranial base tumor surgery was evaluated by a comparison of recordings of condylar movement in right and left parasagittal planes during opening and protrusive movements. The characteristic tracing and measurements of mandibular movements at the condyle of six patients after surgery were compared with a nonsurgical asymptomatic control group consisting of 16 subjects. Of the six surgical patients, three patients had the condyles disarticulated and rearticulated, and three patients had condyles surgically resected. The data gathered through computerized axiographic tracings of horizontal condylar inclinations at different intervals showed significant interaction effects among right and left sides within the groups (p 0.001). Medical histories and clinical examinations were used to diagnose or rule out the presence of TMJ disorders. Magnetic resonance imaging (MRI) and three-dimensional computerized tomograms (CT) imaging of the TMJs of these patients were investigated. MRI and CT scans illustrated the static detail and morphology of the TMJs. Computerized axiography revealed the dynamic detail and function of the TMJs in the various mandibular movements. The study of condylar pathways during opening and protrusive movements showed variations of mandibular deviation among patients having cranial base surgery. Increased mandibular deviation was found in patients who experienced resected condyles.

Influence of tooth contact on the path of condylar movements.

The correlation between condylar inclination and tooth guidance was tested by comparison of recordings of condylar movement in right and left parasagittal planes during lateral excursion, opening, and protrusive movements in 13 subjects with temporomandibular joint (TMJ) clicks and 15 subjects without TMJ clicks. The characteristic tracing of mandibular movements at the condyle with tooth-guided versus non-tooth-guided conditions were investigated by use of a computerized Axiograph graph. The generated tracings of each subject were graphed and analyzed to calculate the horizontal condylar inclinations as related to the axis orbital reference plane. Information from a standardized questionnaire provided evidence of a definite correlation between the presence of TMJ clicking and a specific prior medical event (tonsillectomy). The data from computerized tracings of all subjects revealed no significant difference (p 0.05) in the mean angles of condylar guidance at any of the millimeter intervals examined regardless of whether the craniomandibular contact was an articulation of natural teeth or an articulation of maxillary natural teeth against a tray clutch. These results do not suggest that dynamic interarch tooth guidance or the change in vertical dimension reflect a significant alteration in the recordings of condylar guidance in clicking or nonclicking groups.

The use of visible light-cured resin system in maxillofacial prosthetics and neuro-orthopedic surgery.

The use of visible light-cured (VLC) resin was evaluated in contrast to more traditional chemical-cured resins for reconstruction of the spine in experimental rats. Such procedures are used to reconstruct vertebra in humans following corpectomy for neoplastic destruction of the spine. Numerous disadvantages exist in the use of chemical-cured resins, including excessive heat generated during the polymerization, cytotoxic effects of the nonpolymerized monomers on adjacent tissues, increased risk of infection due to impaired immunity, and distortion problems with the polymers. A new visible light-cured resin, Triad, was tested for use in maxillofacial prosthetics and for vertebral body replacement in neuro-orthopedic surgery. This study evaluated the biocompatibility of the VLC resin system as a bone implant material. The results of this study have shown the VLC resins underwent polymerization without substantial exothermic reaction and the biologic testing indicated that they are nontoxic and biocompatible. Some of the advantages noticed by using VLC resin are accuracy of fit and ease of fabrication and manipulation.

The use of visible light-curing resin for vertebral body replacement.

The technology of visible light-curing resin has recently been developed for use in removable prosthodontics. A quartz halogen lamp producing a 400- to 500-nanometer wave-length spectrum of visible light is used to polymerize high-molecular-weight acrylic resin monomers. While several in vitro and in vivo studies of visible light-curing resin are found in the dental literature, no studies have yet been performed to evaluate it as an intracorporeal implant in surgery. The authors have designed a rat model of microcervical corpectomy to assess vertebral body replacement with visible light-curing resin in comparison to conventional autopolymerizing methyl methacrylate. Spinal cord function tests, spinal-implant stability assessments, and histological evaluations were made in a total of 41 rats at 2, 4, or 6 months postimplant. No animal developed a neurological deficit or radiographic instability, and at sacrifice there was no evidence of implant fracture-extrusion. In addition, there were no signs of adverse reaction in the surrounding tissues. Morphological investigation of the resin/bone interface at 6 months revealed very good implant anchorage. Visible light-curing resin was found to be far superior to methyl methacrylate for construction of spinal implants. Its waxy consistency makes it easy to handle. It remains pliable until light is applied, allowing adjustments in shape for a well-fitted implant without time constraints. Applied in layers, adjustments can be made even after polymerization of a previous layer. This new implantable resin will allow safer, immediate stabilization in patients with neoplastic destruction of the spine, and may also be advantageous for other neurosurgical applications, such as cranioplasty.

The relationship between condylar guidance and temporomandibular joint clicking.

The association between condylar inclination and temporomandibular joint (TMJ) clicking was tested by measuring the angles of condylar guidance in the sagittal plane during opening and closing movements in 12 subjects with temporomandibular joint clicks and 16 subjects without TMJ clicks. Each subject had tracings made by using a customized functional clutch. All subjects had full dentition and were without symptomatic mandibular dysfunction. Condylar inclinations were measured in parasagittal tracing planes. The travel path of the hinge axis of the condyle's movements was recorded, directly formed, and compared with a four-component axiograph recording that used the axis-orbital plane as a reference for the subjects. The measurements of angles along several distances (millimeters) of condylar guidance from the axis-orbital plane were obtained and evaluated. The measurements were made in the sagittal plane and through opening-closing movements starting from the actual occlusal vertical dimension of each subject. The results do not support the hypothesis that mean angles of the condylar guidance are significantly different in the group with TMJ clicking compared with the group without TMJ clicking.