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Browsing by Subject "Temporomandibular Joint"
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Item Analysis of Bone Remodeling in the Mandibular Condyle of Female Retired-Breeder Rabbits Following Altered Loading(1992) Hunt, J. Todd; Garetto, Lawrence P.; Roberts, W. Eugene; Arbuckle, Gordon R.; Brown, David T.; Shanks, James C.Previous studies have associated increased occlusal loads with degenerative changes of the temporomandibular joint (TMJ). The purpose of this study was to analyze effects of increased occlusal loads in adult animals. It was hypothesized that increased functional loading would cause degeneration of the mandibular condyle. Twelve female retired-breeder rabbits (mean age = three years, one month) were divided equally into three experimental groups and one control group. Each of the experimental rabbits received maxillary and mandibular light-cured anterior splints at the beginning of the study to create a bilateral posterior openbite (~2 mm). Theoretically, this should have resulted in increased loads to the TMJ. The first two groups wore the appliances for six and 12 weeks, respectively, prior to euthanasia. The third group wore the appliances for 12 weeks and then had them removed for 12 weeks prior to being euthanized. Fluorescent bone labels were utilized, and the specimens were analyzed histomorphometrically. The cartilage thickness was not statistically different between groups, nor were there any signs of cartilage degeneration. There was a trend, however, toward thinner condylar cartilage in the 12-week group. The six-week group showed significantly less labeled subchondral bone than the control group (0.5 ± 0.1 % versus 2.6 ± 0.3%, respectively; p<.05). The six- and 12-week groups both revealed significantly less periosteal surface label of the condylar neck than the control group (1.5 ± 0.8% and 5.3 ± 1. 7% versus 22.0 ± 3.5%, respectively; p<.05). Likewise, they both showed significantly more label at the cartilage-bone interface (1.0 ± 0.2% and 1.4 ± 0.2% versus 0.4 ± 0.2%, respectively; p<.05) and moderately more label along the trabecular surfaces than the control group. These results indicated that the increased loading of the mandibular condyle initially (at six weeks) depressed remodeling of the subchondral bone and decreased periosteal bone formation. Modeling increased at the cartilage-bone interface and potentially along the trabecular bone surfaces. With continued elevated occlusal loads (at 12 weeks), modeling still was quite active at the cartilage-bone interface and on the trabecular surfaces. Periosteal surface modeling remained depressed compared to the control group, but remodeling in the subchondral bone region increased to that of the control group. The 12/12-week group tended to show findings similar to the control group. This suggests that once loading was returned to normal, the condyle also returned toward preexperimental physiologic conditions. Although this study did not show the obvious degenerative changes one typically equates with osteoarthrosis, the elevated modeling at the cartilage-bone interface following increased joint loads was consistent with the early degenerative changes observed by Radin et al. in their joint-loading model. However, the rapid osseous changes seen in this study refute the theory that the adult TMJ is unable to adapt to altered functional loading.Item Bone Remodeling and Strain Variation Following Altered Mandibular Condyle Loading in Retired Breeder Rabbits(1993) Puntillo, Anthony M.; Garetto, Lawrence P.; Roberts, W. Eugene; Arbuckle, Gordon R.; Chen, Jie; Burr, David B.Several investigators have demonstrated modeling of the mandibular condyle foil following a change in load. A recent study evaluated the effect of age on the ability of the condyle to adapt to such a change. The present study explored the early changes in the mandibular condyles of retired breeder rabbits following an alteration in load, and attempted to quantify this load. Twelve female retired breeder New Zealand white rabbits were divided into four equal groups. Under general anesthesia strain gauges were placed on the lateral inferior body of the mandible bilaterally in two of the groups. Two days post-surgery acrylic splints were placed on the anterior teeth (resulting in a posterior open bite) of one the strain gauge groups and one group that did not receive strain gauges. The splints were maintained for 26 days. A control group received neither strain gauges nor splints. Intravital bone labels were administered to all groups to allow for histomorphometric analysis of condylar modeling and remodeling. In addition, principal strain measurements were recorded pre- and post-splint placement. The histomorphometric findings revealed a significant (p<.03) decrease in the subcondylar space of animals that received splints. Splinted animals also showed a significant increase in labeled surface area (p<.02) and in volume percent label (p<.05) of the trabeculae in the condylar neck region. In addition, surgical placement of the strain gauges significantly (p<.05) decreased the labeling of the periosteal surface in the neck region. The strain gauges proved functional in most rabbits for only a few days and registered large variations and no discernible differences in average maximum microstrain, and average change in microstrain. It was concluded from these results that an incisal prematurity (causing a posterior openbite), 26 days in duration, caused an increase functional load on the condyle. This load resulted in an increase in trabecular label and decrease in porosity of the subchondral plate. The decreased subcondylar space is possibly an indication of stiffening in this region. A stiffening of this nature has been suggested in previous studies to be a precursor to osteoarthritic degeneration.Item A Comparison Study of Temporomandibular Joint Symptoms in Patients Following Mandibular Advancement by Bilateral Sagittal Split Osteotomies: Rigid Fixation Versus Nonrigid Fixation(1989) Flynn, Brent Cameron; Roberts, W. Eugene; Brown, David T.; Nelson, Charles L.; Shanks, James C.; Hennon, David K.Primary consideration must be given to the temporomandibular joint when planning and performing orthognathic surgical procedures. It has long been understood that the status of the temporomandibular joint can easily and unintentionally be altered during orthognathic surgery, regardless of the method of fixation used. With the advent of modern fixation techniques, many clinicians and investigators have questioned the effects of rigid fixation on the temporomandibular joint. To investigate this, a clinical study of 40 patients treated with mandibular advancement for retrognathism was performed. Twenty patients were treated with rigid fixation while another 20 patients had inferior border wires placed with anterior skeletal fixation. All patients were asked questions regarding the history of their temporomandibular joints. In addition, all patients received a clinical postoperative temporomandibular joints. In addition, all patients received a clinical postoperative temporomandibular joint evaluation. The results were statistically analyzed with the Chi-square analysis and Standard T test. It was determined that the Null Hypothesis could not be rejected for any of the symptoms evaluated in this study. The results support the belief that rigid fixation is no different when compared to wire osteosynthesis in terms of prevalence of temporomandibular joint symptoms.Item IGF-I Receptor Localization and Constant Infusion of a Supraphysiologic Dose of IGF-I in the Sprague-Dawley Rat(1993) Alford, Timothy J.; Simmons, Kirt; Roberts, W. Eugene; Garetto, Lawrence P.; Hughes, Christopher; Bixler, DavidPrevious studies have shown an increased growth of the tibial growth plate in rats infused with supraphysiologic doses of IGF-I. However, no one has demonstrated this effect on the TMJ in vivo. To determine the effect of a constant infusion of IGF-1 on the TMJ, 20 Sprague-Dawley rats were divided into three groups: (1) control, (2) surgical control, and (3) IGF-1 and placebo infused. IGF-I was delivered at a rate of 1 μg/day over the TMJ via osmotic minipumps. lntravital bone labels were administered at two-week intervals to monitor growth rate. Following sacrifice, seven mandibular (Mn) dimensions were measured anthropometrically. The mandibles were then imbedded in acrylic and stained with tetrachrome to visualize the Mn cartilage. Fluorescence microscopy was utilized to measure the Mn growth between bone labels and calculate growth rates. In addition, the hypertrophic cartilage layer thickness was measured photomicrographically. ANOVA showed no significant difference (P<0.05) in growth rates or cartilage thicknesses between the groups. However, multiple t tests did show an increase in several Mn dimensions (increase in length from gonion to the mental foramen; increase in length from condylion to the mental foramen; and increase in condylar head anterior-posterior length) in the experimental animals comparing the IGF-I infused side with the placebo infused control side. Therefore, it was concluded that IGF-I, when infused at a constant supraphysiologic dose, may increase mandibular growth in certain directions. The present study is not able to definitively demonstrate that these increases are due to direct effects on Mn cartilage growth.