Occlusion and Disocclusion Time Analysis in Young Patients Affected by Bruxism

Introduction: Bruxism is an involuntary parafunctional habit performed unconsciously during sleep by the jaw muscles in which the tooth rows are pressed against each other and move horizontally. The symptoms in the oral cavity are slightly elusive which makes it difficult to diagnose.Aim: The aim of this study was to analyze the occlusion and disocclusion times in young adults affected by bruxism compared with healthy subjects.Materials and methods: Thirty-four patients (15 men and 19 women) aged between 20-25 years were included in the study. They were allocated into two groups: group 1 – controls (n=13), and group 2 – patients who reported clenching or grinding their teeth (n=21). The study was conducted using a T-Scan Novus occlusion diagnostic device. The results obtained for the occlusion and disocclusion times were analyzed using the latest version of the T-Scan system software (ver. 9.1). The values for occlusion and disocclusion times of all subjects were recorded in the T-Scan.Results: The occlusion times in the control group were found to be longer than those in the bruxism group. The disocclusion times of the subjects in group 1 were found to be shorter than those in group 2.Conclusions: The T-Scan system makes it possible to quantify the occlusion and disocclusion times, which helps to diagnose an initial form of bruxism in individuals at a young age.

Defective Neuronal Positioning Correlates With Aberrant Motor Circuit Function in Zebrafish

Precise positioning of neurons resulting from cell division and migration during development is critical for normal brain function. Disruption of neuronal migration can cause a myriad of neurological disorders. To investigate the functional consequences of defective neuronal positioning on circuit function, we studied a zebrafish frizzled3a (fzd3a) loss-of-function mutant off-limits (olt) where the facial branchiomotor (FBM) neurons fail to migrate out of their birthplace. A jaw movement assay, which measures the opening of the zebrafish jaw (gape), showed that the frequency of gape events, but not their amplitude, was decreased in olt mutants. Consistent with this, a larval feeding assay revealed decreased food intake in olt mutants, indicating that the FBM circuit in mutants generates defective functional outputs. We tested various mechanisms that could generate defective functional outputs in mutants. While fzd3a is ubiquitously expressed in neural and non-neural tissues, jaw cartilage and muscle developed normally in olt mutants, and muscle function also appeared to be unaffected. Although FBM neurons were mispositioned in olt mutants, axon pathfinding to jaw muscles was unaffected. Moreover, neuromuscular junctions established by FBM neurons on jaw muscles were similar between wildtype siblings and olt mutants. Interestingly, motor axons innervating the interhyoideus jaw muscle were frequently defasciculated in olt mutants. Furthermore, GCaMP imaging revealed that mutant FBM neurons were less active than their wildtype counterparts. These data show that aberrant positioning of FBM neurons in olt mutants is correlated with subtle defects in fasciculation and neuronal activity, potentially generating defective functional outputs.

Role of neuronal positioning in jaw motor circuit function in zebrafish

Development of the vertebrate nervous system involves substantial cell migration, where immature neurons move to specific locations to generate functional circuits. Precise neuronal migration and positioning are essential for proper brain architecture and function. Abnormal neuronal migration can contribute to neurological disorders such as lissencephaly, autism and schizophrenia. However, the consequences of abnormal neuronal migration for circuit organization and functional output are poorly understood. To provide some insight, I used the facial branchiomotor (FBM) neurons in zebrafish as a model system to analyze the effects of aberrant neuronal migration on circuit function. The FBM neurons are a subset of the branchiomotor neurons, which are generated in the vertebrate hindbrain and innervate facial and jaw muscles. During development in zebrafish and mice, FBM neurons migrate caudally from rhombomere 4 (r4) to r6 to form the facial motor nucleus and innervate jaw and gill muscles (in fish). In order to examine the consequences of aberrant neuronal migration, one must first characterize the normal functional output of the FBM circuit that drives jaw movements. In collaboration with colleagues in the MU Department of Computer Science, we developed an automated image analysis system to extract motion features from video recordings of jaw movement, enabling rapid and accurate high-throughput analysis. We used this software to examine the emergence of jaw movement in zebrafish larvae between 3-9 days post fertilization (dpf). While gape, the displacement of the lower jaw to form the mouth opening, was minimal at 3 dpf, gape frequency increased sharply by 5 dpf, and stabilized by 7 dpf. A detailed analysis of branchiomotor axons and neuromuscular junctions (NMJs) on jaw muscles suggest that this "maturation" of branchiomotor circuit output may be driven by changes in presynaptic structures at the jaw NMJs. To evaluate the consequences of defective neuronal migration on circuit output, I examined whether jaw movement was affected in the zebrafish off-limits (olt) mutant in which FBM neurons fail to migrate out of r4. In olt mutants, the increase in gape frequency occurred normally between 3-5 dpf. However, the average gape frequency was [approximately] 50 [percent] lower than wildtype siblings from 5-9 dpf while gape amplitude was unaffected. Given the jaw movement defect in olt mutants, I evaluated food intake, an independent measure of jaw movement and another functional output of the branchiomotor circuit. Olt mutants ate poorly compared to their wildtype siblings, consistent with their reduced jaw movement. I then tested several potential mechanisms that could generate the functional deficits in olt mutants. While fzd3a, the gene inactivated in olt mutants, is ubiquitously expressed in neural and non-neural tissues, jaw cartilage and muscle developed normally in olt mutants, and muscle function also appeared to be unaffected. Although FBM neurons were mispositioned in olt mutants, axon pathfinding to jaw muscles were unaffected. Moreover, neuromuscular junctions established by FBM neurons on jaw muscles were similar between wildtype siblings and olt mutants. Interestingly, FBM axons innervating the interhyoideus jaw muscle were frequently defasciculated in olt mutants. Furthermore, GCaMP imaging revealed that mutant FBM neurons were less active than their wildtype counterparts. These data suggest that aberrant positioning of FBM neurons in olt mutants results in subtle defects in fasciculation and neuronal activity, potentially generating defective functional outputs. In the future, we will examine modulatory inputs from other brain regions to the branchiomotor neurons and examine their roles in impacting circuit output in olt mutants.

Detection of EMG Signals by Neural Networks Using Autoregression and Wavelet Entropy for Bruxism Diagnosis

Bruxism is known as the rhythmical clenching of the lower jaw (mandibular) by the contraction of the masticatory muscles and parafunctional grinding of the teeth. It affects patients’ quality of life adversely due to tooth wear, pain, and fatigue in the jaw muscles. Recently, effective diagnosis methods that use electromyography, electrocardiography, and electroencephalography have been developed for bruxism. However, these methods are not economical since they require specialization and can be performed in clinical conditions. Although using surface electromyography signals alone is an economical solution, it is difficult to identify fatigue and parafunctional movements of the jaw muscles via electromyography signals due to peripheral effects. In this study, to achieve an accurate diagnosis of bruxism economically with only electromyography measurements, a new approach based on Autoregression and Shannon Entropies of Discrete Wavelet Transform Energy Spectra to identify jaw muscle activities and fatigue conditions is proposed. By using Artificial Neural Networks in the proposed model, bruxism activities can be detected most accurately.

Blepharospasm, Oromandibular Dystonia, and Meige Syndrome: Clinical and Genetic Update

Meige syndrome (MS) is cranial dystonia characterized by the combination of upper and lower cranial involvement and including binocular eyelid spasms (blepharospasm; BSP) and involuntary movements of the jaw muscles (oromandibular dystonia; OMD). The etiology and pathogenesis of this disorder of the extrapyramidal system are not well-understood. Neurologic and ophthalmic examinations often reveal no abnormalities, making diagnosis difficult and often resulting in misdiagnosis. A small proportion of patients have a family history of the disease, but to date no causative genes have been identified to date and no cure is available, although botulinum toxin A therapy effectively mitigates the symptoms and deep brain stimulation is gaining increasing attention as a viable alternative treatment option. Here we review the history and progress of research on MS, BSP, and OMD, as well as the etiology, pathology, diagnosis, and treatment.

Signs and Symptoms of Temporomandibular Disorder in Male Narghile Smokers versus Male Cigarette Smokers.

Objective: Narghile smoking is highly prevalent in Egypt. The act of narghile smoking involves strong contraction of the jaw muscles, which would putatively cause overloading of the temporomandibular joint; thereby leading to internal derangement of the joint. The current study compared symptoms and signs related to temporomandibular disorder in male narghile smokers versus male cigarette smokers. Methods: This prospective clinical study involved 233 male narghile smokers and 233 male cigarette smokers. A questionnaire and examination findings protocol was applied for each participant. Results: There was a significant increase in incidence of signs of internal derangement in the temporomandibular joints of narghile smokers versus those of cigarette smokers (p=0.001). Tympanic membrane retractions were also more common in narghile smokers versus cigarette smokers(p=0.001), reflecting the significant effects of jaw muscle mechanical efforts on the middle ear system, associated with narghile smoking. Conclusion: Narghile smoking is a traumatizing habit as regards its effects on the temporomandibular joints and ear structures.

Fatigue resistant jaw muscles facilitate long-lasting courtship behaviour in the southern alligator lizard ( Elgaria multicarinata )

The southern alligator lizard ( Elgaria multicarinata ) exhibits a courtship behaviour during which the male firmly grips the female's head in his jaws for many hours at a time. This extreme behaviour counters the conventional wisdom that reptilian muscle is incapable of powering high-endurance behaviours. We conducted in situ experiments in which the jaw-adductor muscles of lizards were stimulated directly while bite force was measured simultaneously. Fatigue tests were performed by stimulating the muscles with a series of tetanic trains. Our results show that a substantial sustained force gradually develops during the fatigue test. This sustained force persists after peak tetanic forces have declined to a fraction of their initial magnitude. The observed sustained force during in situ fatigue tests is consistent with the courtship behaviour of these lizards and probably reflects physiological specialization. The results of molecular analysis reveal that the jaw muscles contain masticatory and tonic myosin fibres. We propose that the presence of tonic fibres may explain the unusual sustained force properties during mate-holding behaviour. The characterization of muscle properties that facilitate extreme performance during specialized behaviours may reveal general mechanisms of muscle function, especially when done in light of convergently evolved systems exhibiting similar performance characteristics.