Chewing Analysis by Means of Electromagnetic Articulography: Current Developments and New Possibilities.

Chewing is a complex procedure that involves sensory feedback and motor impulses controlled by the trigeminal system in the brainstem. The analysis of mandibular movement is a first approximation to understanding these mechanisms. Several recording methods have been tested to achieve this. Video, ultrasound, the use of external markers and kinesiographs are examples of recording systems used in research. Electromagnetic articulography is an alternative method to those previously mentioned. It consists of the use of electromagnetic fields and receiver coils. The receiver coils are placed on the points of interest and the 3D coordinates of movement are saved in binary files. In the Oral Physiology Laboratory of the Dental Sciences Research Center (Centro de Investigación en Ciencias Odontológicas-CICO), in the Faculty of Dentistry at the Universidad de La Frontera (Temuco, Chile) several research studies have been carried out using the AG501 3D EMA articulograph (Carstens Medizinelektronik, Lenglern, Germany). With this device, they developed a series of protocols to record mandibular movement and obtain new information, such as the 3D Posselt polygon, the area of each polygon, individualized masticatory cycles and speed and acceleration profiles. Other investigations have analyzed these parameters, but separately. The AG501 allows for holistic analysis of all these data without altering natural movement. A limitation of this technology is the interference generated by its metallic elements. The aim of the present work is to show the developed methods used to record mandibular movement in the CICO, using the AG501 and compare them with others used in several research studies.

Transcutaneous Electrical Nerve Stimulation in Nerve Regeneration: A Systematic Review of In Vivo Animal Model Studies.

OBJECTIVE: Transcutaneous electrical nerve stimulation (TENS) is a noninvasive electrical stimulation therapy indicated for pain control that has been applied for the regeneration of nerves. This systematic review aimed to analyze the evidence on TENS effectiveness on nerve regeneration. MATERIALS AND METHODS: A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria: PubMed/MEDLINE, Web of Science, ScienceDirect, and SciELO data bases. Primary research that evaluated TENS on nerve regeneration was considered. RESULTS: Several studies have investigated the use of TENS for pain treatment. A total of six animal studies analyzed TENS for nerve regeneration. The selected articles showed high quality (Animal Research: Reporting of In Vivo Experiments guidelines), with many unclear points related to bias opportunities (Systematic Review Center for Laboratory Animal Experimentation Risk of Bias tool). In general, TENS accelerated functional and motor recovery and increased axon quantity and diameter. More specifically, the application of low-frequency TENS resulted in a continuous basal lamina; a higher density of fibers with normal diameters, indicating normal myelination, showed signs of deterioration and delayed nerve regeneration. In contrast, the high-frequency TENS application stimulated motor regeneration and increased the diameter of the regenerated axons but revealed a small number of axons, demyelination, dark axoplasm, and an increase in the predisposition of neuropathic pain. CONCLUSIONS: Although there is some heterogeneous evidence in animal research, TENS seems to be a promising treatment for nerve injury that should be better explored. It is still necessary to improve the analysis of its application parameters, which can lead to the most satisfactory regeneration results and improve the understanding of its mechanisms on peripheral nerve regeneration.

Determination of Mandibular Position and Mouth Opening in Healthy Patients and Patients with Articular and/or Muscular Pathology: A Pilot Study with 3D Electromagnetic Articulography and Surface Electromyography.

Temporomandibular disorders (TMDs) are a group of pathologies that affect the temporomandibular joint and its related structures, producing intracapsular and muscular pathologies. The aim of this study is to describe, by electromagnetic articulography (EMA) and simultaneous electromyography (sEMG), the mandibular postural position and mouth opening in healthy patients and with articular and/or muscular pathology. MATERIALS AND METHODS: A pilot study was conducted with a sample of sixteen participants aged 18 years or older who attended the TMDs and Orofacial Pain Polyclinic of the University of La Frontera due to TMDs. The physiological inoculation space was evaluated from the mandibular postural position (MPP) with swallowing command and without command, in both healthy patients and patients with articular, muscular, and mixed TMDs, measured simultaneously with EMA and sEMG. An angular measurement of the oral opening was also performed with the data obtained. RESULTS: The physiological inoculation space was obtained from the determination of the MPP through the procedures with swallowing command and without command, and different mouth opening degrees were evaluated. CONCLUSIONS: Simultaneous position and sEMG records can be produced from EMA, and different characterization variables such as the vertical distance, Euclidean distance, and angle can be obtained.

A Novel Technique to Accurately Measure Mouth Opening Using 3D Electromagnetic Articulography.

The mouth opening is an important indication of the functionality of the temporomandibular joint (TMJ). Mouth opening is usually evaluated by asking the patient to open their mouth as wide as possible and measuring the distance between the edges of the frontal incisors with a ruler or caliper. With the advancement of technology, new techniques have been proposed to record mandibular movement. The aim of this work is to present a novel technique based on 3D electromagnetic articulography and data postprocessing to analyze the mouth opening considering distances, trajectories, and angles. A maxilla-mandible phantom was used to simulate the mouth opening movement and fixed position mouth opening. This was recorded using the AG501 3D EMA (Carstens Medizinelektronik GmbH, Bovenden, Germany). The collected data was processed using Matlab (Mathworks, Natick, MA, USA). Fix and mobile mouth opening of 1, 2, 3 and 4 cm were simulated. It was possible to evaluate the mandibular opening through the vertical distance, the Euclidean distance, the trajectory, and the opening angle. All these values were calculated and the results were consistent with expectations. The trajectory was the highest value obtained while the vertical distance was the lowest. The angle increased as the mouth opening increased. This new technique opens up new possibilities in future research since oral opening can be analyzed using multiple variables without the need to use different devices or depending on the researcher's experience. This will make it possible to establish which parameter presents significant differences between groups of patients or between patients who have undergone some treatment.

Non-Syndromic Familial Mesiodens: Presentation of Three Cases.

Mesiodens are the most common supernumerary teeth and are detected incidentally during routine radiographic examination, so late diagnosis complications are very common. The dentist must make a timely diagnosis and thus avoid clinical complications. Despite advances in knowledge of dental morphogenesis and differentiation, the etiology of mesiodens remains unclear. Therefore, several theories have been postulated to explain how and why they develop. It was described in the literature that heredity could play an important role in the appearance of supernumerary teeth, with a higher rate of appearance in relatives of those affected. This article reports three cases, a mother and two children, who present mesiodens, which shows that supernumerary teeth may involve a genetic factor. In addition, a literature review was carried out to assess the importance of the genetic factor as a possible cause of mesiodens. The relevance and implications of timely diagnosis in clinical practice to avoid manifestations of clinical complications are discussed. Therefore, the identification of the genetic risk factors responsible for the formation of supernumerary teeth is essential for developing a screening tool to determine an individual's genetic risk.

Polyhydroxybutyrate (PHB) Scaffolds for Peripheral Nerve Regeneration: A Systematic Review of Animal Models.

In the last two decades, artificial scaffolds for nerve regeneration have been produced using a variety of polymers. Polyhydroxybutyrate (PHB) is a natural polyester that can be easily processed and offer several advantages; hence, the purpose of this review is to provide a better understanding of the efficacy of therapeutic approaches involving PHB scaffolds in promoting peripheral nerve regeneration following nerve dissection in animal models. A systematic literature review was performed following the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA) criteria. The revised databases were: Pub-Med/MEDLINE, Web of Science, Science Direct, EMBASE, and SCOPUS. Sixteen studies were included in this review. Different animal models and nerves were studied. Extension of nerve gaps reconnected by PHB scaffolds and the time periods of analysis were varied. The additives included in the scaffolds, if any, were growth factors, neurotrophins, other biopolymers, and neural progenitor cells. The analysis of the quality of the studies revealed good quality in general, with some aspects that could be improved. The analysis of the risk of bias revealed several weaknesses in all studies. The use of PHB as a biomaterial to prepare tubular scaffolds for nerve regeneration was shown to be promising. The incorporation of additives appears to be a trend that improves nerve regeneration. One of the main weaknesses of the reviewed articles was the lack of standardized experimentation on animals. It is recommended to follow the currently available guidelines to improve the design, avoid the risk of bias, maximize the quality of studies, and enhance translationality.