A Randomized, Double-Blind, Placebo-Controlled Study of the Efficacy of Steroid Supplementation After Temporomandibular Joint Arthrocentesis.

PURPOSE: In patients with unilateral intra-articular temporomandibular joint (TMJ) pain, the efficacy of steroid supplementation compared with placebo after TMJ arthrocentesis was examined in a randomized, double-blind, placebo-controlled clinical trial. PATIENTS AND METHODS: Female patients unsuccessfully treated by usual therapy were recruited. After informed consent was obtained, 24 patients were randomly assigned to either the experimental group or placebo group. After local anesthesia, TMJ arthrocentesis, consisting of joint lavage using 100 mL of lactated Ringer solution, was performed by a single investigator. Depending on group assignment, triamcinolone acetonide (steroid) or lactated Ringer solution (placebo) was infused into the superior joint space. Patients, blinded to the procedure, were evaluated at baseline and 2, 6, and 12 weeks after arthrocentesis using a visual analog scale for primary outcome pain measures (pain intensity, pain unpleasantness, and chewing pain). A clinical examination using the Research Diagnostic Criteria for Temporomandibular Disorders was performed at each time point by a separate calibrated, blinded examiner. Data were analyzed using an intention-to-treat model. RESULTS: Significant decreases in visual analog scale pain scores over time were found between baseline and the post-arthrocentesis time points for both groups. The steroid group had significantly less chewing pain at 6 and 12 weeks than the placebo group. Mean maximum mandibular openings without pain or with pain were significantly greater at all post-arthrocentesis time points than at baseline in the steroid group, whereas the placebo group had a larger mandibular opening at 6 weeks. At 12 weeks, significantly more patients in the steroid group (75%) had a nearly normal mandibular opening without pain (38 mm) compared with the placebo group (20%). In addition, the proportion of patients with a greater than 50% improvement in chewing pain in the steroid group (90%) was significantly higher than that in the placebo group (<40%). CONCLUSIONS: The results of this randomized controlled trial support steroid supplementation after TMJ arthrocentesis to achieve longer-lasting pain management and increased pain-free mandibular mobility.

Mouse incising central pattern generator: Characteristics and modulation by pain.

INTRODUCTION: Vertebrate incising and chewing are controlled by a set of neurons comprising the central pattern generator (CPG) for mastication. Mandibular positioning and force generation to perform these tasks is complex and requires coordination of multiple jaw opening and closing muscle compartments located in muscles on both sides of the jaw. The purpose of this study was to determine the characteristics of the CPG by recording mouse incising forces in the home cage environment to evaluate changes in force characteristics with incising frequency and force direction. A second purpose was to evaluate the effects of jaw closing muscle pain on CPG output parameters. METHODS: Digitized incising forces were recorded for approximately 24 h using a 3-dimensional force transducer attached to solid food chow. Male and female CD-1 mice were evaluated during their last (fourth) baseline assessment and seven days after a second acidic saline injection into the left masseter muscle when maximum pain was experienced. Incising force resultants were calculated from the three axes data and force parameters were assessed including inter-peak intervals (IPI), peak amplitude, load time and unload time. Multiple regression analyses were conducted to identify incising episodes that had parameters of force that were significantly correlated (p < 0.001). These incising episodes were considered to represent the output of the CPG with a steady state of incoming sensory afferent inputs. Incising parameters were evaluated for each of the discrete incising frequencies (4.6, 5.3, 6.2, 7.6 Hz) and the predominant force directions: jaw closing (-Z), jaw retrusion (+X) and jaw protrusion (-X). RESULTS: A significant correlation between incising frequency (IPI) and the load time was observed. A significant decrease in peak amplitude was observed with higher incising frequency while the load rate significantly increased. The force peak amplitude and load rates were found to be statistically different when the force direction was considered, with smaller peak amplitudes and smaller load rates found in the jaw closing direction. The effect of pain on incising was to reduce the peak amplitude and load rate of incising compared to the baseline condition at lower incising frequencies. CONCLUSIONS: Like the central pattern generator for locomotion, the CPG for incising controls rhythmicity, peak amplitude and force load duration/rate. However, unlike the CPG for locomotion, the amplitude of incising force decreases as the frequency increases. During incising, load rate increases with faster rhythm and is consistent with the recruitment of larger motor units. Muscle pain reduced the excitatory drive of the CPG on motoneurons and provides further support of the Pain Adaptation Model.

Orthognathic Surgery as a Treatment for Temporomandibular Disorders.

Well-controlled clinical trials supporting orthognathic surgery as the primary management for temporomandibular disorders (TMDs) are lacking. Most published studies lack an adequate experimental design to minimize biases. Studies that did minimize some biases do support an overall reduction in the frequency of TMD signs and symptoms in some Class III and Class II patients who had orthognathic surgery. However, Class II correction with counter-clockwise rotation of the mandible increased TMD. Individual variability precludes the ability to predict TMD outcome after surgery. Irreversible therapies such as orthognathic surgery should not be primary treatments in the management or prevention of TMDs.

Evaluation of Early Postoperative Complications Following Tracheotomy.

PURPOSE: The purpose of this study was to evaluate the early postoperative complications related to tracheotomy performed by surgeons and residents in the Department of Oral and Maxillofacial Surgery (OMS) at the University of Florida College of Dentistry (UFCD; Gainesville, FL). The authors hypothesized that complications with this surgical technique would be substantially different among the different medical diagnoses of these patients and the number of complications would positively correlate with the American Society of Anesthesiologists (ASA) physical status classification. PATIENTS AND METHODS: The authors implemented a retrospective study of all patients who underwent a tracheotomy procedure by the UFCD OMS department from July 2011 through March 2015. Patients were evaluated for medical comorbidities (predictor variables) and tracheotomy complications (outcome variable) within 1 week of the procedure and were compared across ASA classes. RESULTS: A total of 319 patients were evaluated in this retrospective study. There were 14 patients identified with recorded complications, including 11 patients with a bleeding complication (3.4%), and 3 patients with other complications (0.9%). The other complications included dislodgement of the tube, subcutaneous emphysema, and cellulitis. The distribution of patients across ASA groups was not statistically different for patients with no bleeding versus bleeding complications (P > .05 by χ2 test). However, the distribution of patient gender was found to differ across ASA groups (P < .001 by χ2 test). The proportion of men to women in the bleeding complications group was not statistically different (P > .1 by binomial test). However, mean age was found to be statistically different for bleeding complications between men and women (63.4 yr for men; 42.7 yr for women; P < .05 by t test). CONCLUSIONS: The result of this study supports a low rate of complications after a tracheotomy procedure performed by faculty and residents at the UFCD OMS department and is lower than published tracheotomy complication rates reported by other surgical specialties.

Atypical temporomandibular joint pain: a case report.

Atypical temporomandibular joint (TMJ) pain can consist of an unusual intensity, location or set of pain descriptors that do not match what is traditionally observed for TMJ capsular pain, disc displacements or arthritic conditions. Presented in this case report is an atypical pain report regarding a unilateral TMJ pain as the chief complaint. An overview of typical vs atypical TMJ pain is also reviewed to highlight unusual signs and symptoms so that the clinician can identify these atypical presentations and pursue further diagnostic approaches.

Increased vertical dimension effects on masseter muscle fiber phenotype during maturation.

OBJECTIVE: To determine changes in mouse myosin heavy chain (MyHC) protein expression that may occur with a clinically relevant vertical dimension of occlusion (VDO) increase. MATERIALS AND METHODS: Six CD-1 male mice (age: 6 weeks) underwent a 10% bite opening to replicate the clinical condition using composite on the maxillary molars and were compared to six age-matched controls. Mice were sacrificed at day 7 and 14 after bite opening. A representative masseter transverse cryosection from each animal was examined in selected sampling regions (anterior, posterior, posterior-deep, and posterior-intermediate) to assay fiber phenotype proportions and fiber size. RESULTS: In control masseter muscles, the proportion of muscle fibers containing MyHC IIb increased in the posterior-intermediate and posterior-deep regions between 7 and 14 days (ANOVA, P < .05). The increase in the proportion of MyHC IIb fibers in the bite opening group did not occur when compared to the control group (P < .05). In addition, after 14 days of bite opening, the proportion of fibers positive for MyHC IIa was decreased in the anterior region compared to control masseter muscles. Muscle fiber diameter remained unchanged in both groups (experimental and control) and over time (P > .10). CONCLUSION: These data are consistent with a selective plasticity of the expression of MyHC IIb protein in the deep regions of the male masseter muscle in response to a clinically relevant VDO increase.

Use of a novel thermal operant behavioral assay for characterization of orofacial pain sensitivity.

Orofacial pain has been well-characterized clinically, but evaluation of orofacial pain in animals has not kept pace. The objective of this study was to describe behavioral responses to facial thermal stimulation and inflammation with/without an analgesic using a novel operant paradigm. Animals were trained to voluntarily place their face against a stimulus thermode (37.7-57.2 degrees C) providing access to positive reinforcement. These contingencies present a conflict between positive reward and tolerance for nociceptive stimulation. Inflammation was induced and morphine was provided as an analgesic in a subset of animals. Six outcome measures were determined: reward intake, reward licking contacts, stimulus facial contacts, facial contact duration, ratio of reward/stimulus contacts, and ratio of facial contact duration/event. Animals displayed aversive behaviors to the higher temperatures, denoted by a significant decrease in reward intake, total facial contact duration, and reward licking events. The number of facial contacts increased with increasing temperature, replacing long drinking bouts with more frequent short drinks, as reflected by a low ratio of facial contact duration/event. The number of reward licking/facial contact events was significantly decreased as the thermal stimulus intensity increased, providing another pain index derived from this operant method. These outcomes were significantly affected in the direction of increased nociception following inflammation, and these indices of hyperalgesia were reversed with morphine administration. These data reflect an orofacial pain behavior profile that was based on an animal's responses in an operant escape paradigm. This technique allows evaluation of nociceptive processing and modulation throughout the neuraxis.

Sex differences in rabbit masseter muscle function.

The proportions of fibers of different phenotypes in the rabbit masseter muscle differ strikingly in adult males and females. Muscles from females contain similar proportions of small fibers that express both the slow/beta and cardiac alpha myosin heavy chain (MyHC) isoforms and larger fibers containing the IIa MyHC isoform. In muscles from males, nearly 80% of fibers are of the IIa phenotype. To evaluate the functional significance of these sex differences, we used finely graded intramuscular microstimulation to study the contractile properties of masseter motor units in >6-month-old male and female rabbits. Twitch forces and torques in males were significantly greater in magnitude than those of females. Greater proportions of units that produced larger forces/torques were encountered in the males. The same motor units produced force or torque more rapidly in males than in females, principally because units in which twitch rise times were >22 ms were found only in females. The forces applied to the mandible and the torques generated about the right mandibular condyle were studied during cortically evoked rhythmic activation of the masticatory muscles. The overall range of torque rise times and the magnitudes of the peak torques did not differ between sexes. The mean rise time was significantly shorter and the mean peak torque was significantly greater in males. We conclude that sex differences in fiber phenotype proportions are reflected in sex differences in motor unit properties and in the function of these motor units during rhythmic activation.

Sex differences in rabbit masseter motoneuron firing behavior.

To evaluate whether sex differences in the proportions of fibers of different phenotypes in the masseter muscle might be the result of differences in the behavior of their motoneurons, we studied the firing patterns of masseter motoneurons in adult male and female rabbits. Activity in individual motoneurons was determined from high spatial resolution EMG recordings made during cortically evoked rhythmic activation of the masticatory muscles. Although some motoneurons could be said to fire according to slow-tonic or fast-phasic patterns, most did not. In both sexes a substantial range of median firing rates and median firing durations was found. In adult males, masseter motoneurons fired more rapidly than those recorded from adult females. No significant sex differences in motoneuron firing duration were found. These results are consistent with the hypothesis that androgen-induced differences in rabbit masseter muscle fiber phenotype are a reflection of differences in motoneuron firing rate. Whether this effect of androgen is directly upon the motoneurons or is the result of a response of muscle fibers to androgen remains to be investigated.