Masticatory Activity Research Articles

Efficacy of Proprioceptive Neuromuscular Facilitation on Jaw Function in Bruxism Among Post Stroke Survivor: A Case Study

A 49-year-old male who was a known case of Type 2 diabetes mellitus and hypertensive had a history of an acute infarct in the left ganglia capsular region and a chronic infarct in the left parieto-occipital lobe, which was conservatively managed and was referred for physiotherapy rehabilitation for strengthening the right upper and lower limb. During the physiotherapy intervention, abnormal teeth grinding was observed, and the patient was asked about parafunctional behaviour. Upon examination, there was a restriction in the jaw range of motion assessed by measuring the jaw range using the vernier caliper and tightness in the masticatory muscle, as evidenced by palpating the masseter muscle. Proprioceptive neuromuscular facilitation and ultrasound therapy were given for 1 session per week for 2 weeks to treat bruxism along with standardized stroke protocol. At the end of 2 weeks after the intervention, there was an increase in jaw opening and reduced masticatory muscle activity. Jaw opening was measured using a vernier caliper, and masticatory activity was measured using electromyography of the masseter and temporalis muscles. This study suggests the importance of treating bruxism to prevent complications related to it. It concludes that proprioceptive neuromuscular facilitation and ultrasound therapy were effective in improving mouth opening and reducing the masticatory activity in bruxism among stroke patients with ganglia capsular involvement.

Influence of surface texturing and coatings on mechanical properties and integration with bone tissue: an in silico study.

This investigation delves into the mechanical behaviour of titanium dental implants, a preferred choice for tooth replacement due to their superior reliability over alternative materials. The phenomenon of implant loosening, frequently induced by masticatory activities, underscores the significance of surface modification or texturing to bolster the interaction between the implant and bone tissue. This research comprehensively examines the effects of four distinct surface texturing techniques and five varied bone quality conditions on the biomechanical performance of these implants. The scope of this study is delineated by its focus on implants of diameters 4mm and 6mm, with lengths measuring 9mm and 12mm respectively. Furthermore, the analysis incorporates the evaluation of four different coatings-hydroxyapatite, HA3TO, HA3Sr, and HA1.5TO1.5Sr-to investigate their efficacy in enhancing the osseointegration process on textured surfaces of dental implants. The experimental design entails the assessment of stress distribution within the implant and its coatings, alongside the strain exerted on the surrounding cancellous bone, under the conditions of an average vertical biting force. A comparative analysis between solid implants and those subjected to surface texturing techniques has been conducted. This comparison elucidates the advantageous microstrain profiles presented by certain textured surfaces, which are deemed more conducive to optimal osseointegration. Notably, across all examined textures, the application of hydroxyapatite (HA) and a modified HA composition (HA1.5TO1.5Sr) demonstrates significant improvements in mechanical stability, particularly in scenarios involving weak and very weak bone conditions. This study's findings contribute to the ongoing advancement in dental implant technology, emphasizing the critical role of surface texturing and coating strategies in promoting implant longevity and integration within the biomechanical environment of the human oral cavity.

Introduction of a model for the modification of masticatory activity to investigate induced neural and behavioral alterations in mice

In the literature, there is consistent evidence related to the influence of chewing on brain functions, either from experimental models or in humans. In the case of humans, most results are restricted to functional tests, lacking cellular or molecular evidence. In the described method, the possibility of using experimental models is presented, as well as the mimicry of deprivation and rehabilitation of masticatory activity and without stress impact. By opting for the use of mash feed, instead of extracting or implanting an intraoral device, alternations between restriction and rehabilitation of mastication were imposed on murine models. The animals completed various temporal windows, with aging also representing a potential factor for translational dementia associations. Additionally, animals were segregated into environments characterized as either standard, simulating a sedentary lifestyle, or enriched, rich in sensorimotor and visuospatial stimulation. Thus, it was possible to study the influence of changes in masticatory activity, associated with aging and environmental enrichment, on cells from subregions of the hippocampus, as well as on performance in tests of learning and spatial memory.•Animal model for masticatory activity alteration;•Masticatory deprivation and rehabilitation, and•Models to study the interaction among masticatory activity, aging and enrichment environment.

Unraveling the Life History of Past Populations through Hypercementosis: Insights into Cementum Apposition Patterns and Possible Etiologies Using Micro-CT and Confocal Microscopy.

The "teeth-as-tools" hypothesis posits that Neanderthals used their anterior teeth as a tool or a third hand for non-dietary purposes. These non- or para-masticatory activities (e.g., tool-making or food preparation prior to ingestion) have also been described in other past and extant human populations, and other Primates. Cementum is the mineralized tissue that covers the tooth root surface and anchors it to the alveolar bone. Under certain conditions (e.g., mechanical stress, infection), its production becomes excessive (i.e., beyond the physiological state) and is called 'hypercementosis'. Several studies in dental anthropology have established a correlation between the teeth-as-tools and hypercementosis. The present work aims to characterize the different patterns of cementum apposition on archeological teeth and discuss their supposed etiology. Using microtomography and confocal microscopy, the patterns of cementum apposition (i.e., thickness, location, and surface characteristics) were analyzed in 35 hypercementotic teeth (Sains-en-Gohelle, France; 7th-17th c. A.D.). Four groups were identified with distinct hypercementosis patterns: (1) impacted, (2) infected, (3) hypofunctional, and (4) hyperfunctional teeth. Characterizing hypercementosis can contribute to documenting the oral health status (paleopathology) and/or masticatory activity of individuals, even from isolated teeth. This has implications for the study of fossil hominins, particularly Neanderthals, known for their use of anterior teeth as tools and frequent and substantial occurrence of hypercementosis.

Three-dimensional changes in the cranial base associated with soft-diet feeding.

Masticatory activity affects the morphology of the maxillo-mandibular complex, however, its influence on the cranial base remains to be elucidated. The recent integration of quantitative morphometric analysis with 3D imaging enabled a comprehensive and high-resolution morphological characterization of the craniofacial complex. We aimed to investigate the influence of masticatory activity on the morphology of the growing cranial base by three-dimensional (3D) geometric morphometric approach using micro-CT. The micro-CT data was reanalyzed to illustrate the 3D shape of the cranial base, and wireframe models were generated by connecting landmarks on the images. In the original study, mice were fed a soft diet (SD) of powdered pellets or a conventional hard diet (HD) for 6 weeks from 3 to 9 weeks of age, immediately after weaning. A principal component (PC) analysis analyzed shape variations and assessed their significance, while canonical variate (CV) analysis facilitated the comparison and differentiation of groups based on shape, unveiling meaningful shape distinctions. Three PCs were extracted that significantly separated the SD and HD groups among those explaining variations in shape. These PCs were related to the length of the sphenoid bone, the width of the anterior part of the sphenoid bone, and the length of the cranial base. Furthermore, one CV effectively distinguished SD from HD, and CV analysis showed that the sphenoid was shortened in the length and narrowed at the border of the temporal bone in SD mice. Masticatory loading affects the skeletal development of the cranial base. The morphology of the sphenoid bone was affected in both the sagittal and transverse axes.

Interrelated Association between Edentulism, Cognitive Decline and Prosthodontic Rehabilitation: A Review

Aim and Objective: To establish a relationship between tooth loss and cognitive decline as well as the influence of removable dental prosthesis on cognitive health.
 Materials and Methods: Initial electronic search was carried out using the following electronic databases: Scopus, PubMed/Medline and Cochrane Database of case controls, systematic and literature re views using the following keywords: “Alzheimer’s Disease”, “Cognitive decline” “Dental prostheses or “Dementia” and “tooth loss” or “edentulism”.
 Results: A total of 13 studies were selected according to the selection criteria. Out of 13 studies, 8 studies were included, and 5 studies were excluded from the review.
 Discussion: Sensory information from the oral cavity is sent to the brain via the trigeminal nerve. Effective chewing increases oxygen levels in key brain areas and hence impaired chewing can lead to cognitive decline. Furthermore, people with more missing teeth were at a higher risk of developing Alzheimer's disease or dementia and those with normal cognitive function had significantly more teeth than those who were cognitively impaired, indicating a link between edentulism and risk of cognitive decline. Prosthodontic rehabilitation through dentures results in significant arousal of the dorsal prefrontal cortex and enhances patients' quality of life by improving their masticatory activity and comfort, thus potentially helping prevent cognitive decline leading to dementia.
 Conclusion: From this literature review we can gather that edentulism may be used as a marker for cognitive decline and that prosthetic rehabilitation may aid in the preservation of cognitive health.
 Clinical Significance: Prosthodontic rehabilitation in order to bring about effective mastication and chewing efficiency is imperative in prevention of decline in cognitive function.

Synchronization of Surface Electromyography and 3D Electromagnetic Articulography Applied to Study the Biomechanics of the Mandible: Proof of Concept

Background. The aim of this study was to propose and establish the proof of concept of an approach to synchronize 3D Electromagnetic Articulography (3D-EMA) with Surface Electromyography (SEMG) based on the standard components of this equipment. Methods. The appropriate equipment and instruments were selected according to specifications stablished for this study. Once the necessary equipment was gathered, the proper conditions to synchronize the signals were created. Thus, we selected a SEMG with a switch module incorporated to be able to achieve synchronization of the signals. After the system setup was stablished, chewing tasks were recorded on a healthy volunteer, collecting a proof-of-concept database. The variability among recordings of the database were analyzed in terms of its standard deviation in order to detect possible interferences. Results. The analysis of the chewing task recordings obtained with the synchronized 3D EMA and SEMG signals in the present study did not reveal significant distortions, and all values were within those that had been given by the manufacturers of both of the systems. The method presented the advantage of using only components that are already included with the equipment employed. Conclusion. The method of analysis described in this paper is an effective tool that facilitates the investigation of mandibular movements synchronized in two domains: articulatory movements and electromyographic activity. Thus, it seems promising that it can be applied in different clinical situations to improve the analysis of the complexity of masticatory activity in addition to being able to generate new insights on this topic.

0558 Sleep Bruxism and Sleep Breathing Disorder

Abstract Introduction Sleep bruxism (SB) is reported by 8-9% of the adult population and is mainly associated with rhythmic masticatory muscle activity (RMMA) characterized by repetitive jaw muscle contractions (3 bursts or more at a frequency of 1 Hz). The purpose of this study was to evaluate the relationship between the nature of sleep bruxism and the sleep breathing disoredr. Methods We prospectively studied 32 patients who were referred to the clinical sleep apnea laboratory for study. They underwent standard nocturnal polysomnographic examination; in addition, masticatory activity was measured with a masseter electromyogram. Patients slept in the supine and lateral decubitus positions. Results Nocturnal clenching was higher in patients with higher respiratory disturbance index. 28 among 32 patients were included in the criteria of obstructive sleep apnea; average respiratory disturbance index (RDI) was 12.7 280 clenches demonstrated in all patients. Conclusion We conclude that there is an association between sleep related breathing disorder and bruxisms that sleep position affects the incidence of both sleep disordered breathing and bruxisms, and that analysis of apneas and hypopneas and clenching events in both supine and lateral decubitus sleeping positions may be helpful. Support (if any)

The Masticatory Activity Interference in Quantitative Estimation of CA1, CA3 and Dentate Gyrus Hippocampal Astrocytes of Aged Murine Models and under Environmental Stimulation.

Studies indicating the influence of masticatory dysfunction, due to a soft diet or lack of molars, on impairing spatial memory and learning have led to research about neuronal connections between areas and cell populations possibly affected. In this sense, with scarce detailed data on the subfields of hippocampus in dementia neurodegeneration, there is no information about astrocytic responses in its different layers. Thus, considering this context, the present study evaluated the effects of deprivation and rehabilitation of masticatory activity, aging, and environmental enrichment on the stereological quantification of hippocampal astrocytes from layers CA1, CA3, and DG. For this purpose, we examined mature (6-month-old; 6M), and aged (18-month-old; 18M) mice, subjected to distinct masticatory regimens and environments. Three different regimens of masticatory activity were applied: continuous normal mastication with hard pellets (HD); normal mastication followed by deprived mastication with equal periods of pellets followed by soft powder (HD/SD); or rehabilitated masticatory activity with equal periods of HD, followed by powder, followed by pellets (HD/SD/HD). Under each specific regimen, half of the animals were raised in standard cages (impoverished environment (IE)) and the other half in enriched cages (enriched environment (EE)), mimicking sedentary or active lifestyles. Microscopic stereological, systematic, and random sampling approaches with an optical dissector of GFAP-immunolabeled astrocytes were done, allowing for an astrocyte numerical estimate. Stratum moleculare and hilus, from the dentate gyrus (DG) and Strata Lacunosum-Moleculare, Oriens, and Radiatum, similarly to the dentate gyrus, showed no significant change in any of the investigated variables (age, diet, or environment) in these layers. However, in Stratum radiatum, it was possible to observe significant differences associated with diet regimens and age. Therefore, diet-related differences were found when the HD 18M IE group was compared to the HD/SD/HD 18-month-old group in the same environment (IE) (p = 0.007). In the present study, we present modulatory factors (masticatory function, environmental enrichment, and aging) for the differentiated quantitative laminar response in the hippocampal regions, suggesting other studies to read the plasticity and responsiveness of astrocytes, including the molecular background.

The Effect of Accentuation of Curve of Spee on Masticatory Efficiency—A Systematic Review and Meta-Analysis

The appropriate alignment of the lower teeth is indicated by the Curve of Spee (COS), which can be observed in the sagittal profile view of human skulls. Graf Von Spee made the initial observation on this occlusal curvature. Through this systematic review and meta-analysis, we evaluated studies that looked at how COS affected masticatory activities. The databases PubMed-MEDLINE, Web of Science, Cochrane, and Scopus were all searched. A total of 12 documents were ultimately picked because they met the necessary inclusion and exclusion requirements. The data was then loaded into the RevMan 5 programme for meta-analysis after being chosen for information on the sample size, variables analyzed, and various aspects of the research. The Curve of Spee was found to have a noticeable impact on both the masticatory efficiency as well as dentofacial alignment in the 12 studies that we selected for the review and meta-analysis. In addition, other occlusal curvatures such as the Curve of Monson and the Curve of Wilson were found to be of vital importance on a similar level to the COS. The meta-analysis further revealed that seven of the included clinical trials had mentioned the noticeable impact on masticatory efficiency. This study focused on the significance of the COS on force distribution in the oral cavity as well as the necessity of COS corrections after receiving full orthodontic care. Following orthodontic treatment, the COS, along with other occlusal curves such as the Curve of Wilson and the Curve of Monson, is essential in removing strains from the condyle, as well as the maxilla and mandible, which enhances masticatory effectiveness and lessens the overall strain on a patient's oral cavity.

Effects of CX3CR1 and CXCR2 antagonists on running-dependent intramuscular neutrophil recruitments and myokine upregulation.

Muscle contractile activity stimulates intramuscular recruitment of immune cells including neutrophils emerging to serve as a prerequisite for exerting proper muscular performance, although the underlying mechanisms and their contributions to myokine upregulation remain ill-defined. We previously reported that pharmacological inhibition of CX3CR1, a fractalkine receptor, dampens gnawing-dependent neutrophil recruitment into masseter muscles along with compromising their masticatory activity. By using a running exercise model, we herein demonstrated that hindlimb muscles require collaborative actions of both CX3CR1- and CXCR2-mediated signals for achieving neutrophil recruitment, upregulation of myokines including interleukin (IL)-6, enhanced GLUT4 translocation, and adequate endurance capability. Mechanistically, we revealed that a combination of CX3CR1 and CXCR2 antagonists, i.e., AZD8797 and SB2205002, inhibits exercise-inducible ICAM-1 and fractalkine upregulations in the area of the endothelium and muscle-derived CXCL1 upregulation, both of which apparently contribute to the intramuscular neutrophil accumulation in working muscles. Intriguingly, we also observed that 2 h of running results in intramuscular augmentation of innate lymphoid type 2 cells (ILC2s) markers, i.e., Bcl11b mRNA levels and anti-GATA-3-antibody-positive signals, and that these effects are completely abolished by administration of the combination of CX3CR1 and CXCR2 antagonists. Taken together, our findings strongly suggest that the exercise-evoked regional interplay among working myofibers, the adjacent endothelium, and recruited immune cells including neutrophils and possibly ILC2s, mediated through these local factors, plays a key role in the organization of the intramuscular microenvironment supporting the performance of hindlimb muscles during running.NEW & NOTEWORTHY This study provides compelling evidence that running-dependent intramuscular neutrophil recruitment requires both CX3CR1- and CXCR2-mediated signals that prime not only myofiber-derived myokine upregulations but also endothelium ICAM-1 and fractalkine expressions. The results revealed the importance of the exercise-evoked regional interplay among working myofibers, the adjacent endothelium, and recruited immune cells, including neutrophils and possibly ILC2s, which plays a key role in the organization of the intramuscular microenvironment supporting the performance of hindlimb muscles during running.

Electromyographic analysis of the stomatognathic system of children with Molar-incisor hypomineralization.

Molar-incisor hypomineralization (MIH) is a qualitative defect of dental enamel that affects one or more permanent first molars, with or without involvement of the incisor teeth. This condition leads to challenges to dental care and treatment planning. Based on the hypothesis that children who have MIH possibly present alterations in postural and masticatory activities and considering the absence of studies investigating these parameters, the present study evaluated the functionality of the stomatognathic system considering the mentioned aspects. The comparison of individuals with (MIHG; n = 32) and without MIH (CG; n = 32) was evaluated by electromyographic activity of the masseter and temporal muscles (right and left), as well as evaluation of the masticatory cycles during habitual mastication. MIHG showed muscle hyperactivity in postural and dynamic conditions compared to the CG; higher electromyographic values for MIHG when compared to CG in the following postural conditions: at rest for the right temporal (p = 0.00) and left temporal muscles (p = 0.03); in the protrusion to the right temporal muscle (p = 0.02); in the right laterality for the right masseter (p = 0.00) and left temporal muscles (p = 0.01); in the left laterality for the right masseter (p = 0.03) and left temporal (p = 0.04) muscles. In dynamic conditions with consistent food, significance was observed for the left temporal (p = 0.01); and with soft food for the right (p = 0.01) and left temporal muscles (p = 0.04). Children with MIH seem to have impaired functionality of the stomatognathic system. Children with MIH have alterations in the stomatognathic system.

Assessment of craniofacial growth in individuals with ectodermal dysplasia after complete denture rehabilitation: A preliminary study.

The main purpose was to evaluate the effect of complete denture rehabilitation on the jaw growth pattern in individuals with ectodermal dysplasia from an early age to maturity. This was a prospective in vivo study performed in the Department of Prosthodontics, King George Medical University, Lucknow, India. Rehabilitation with three sets of conventional complete dentures was completed in an ectodermal dysplasia case at the age of 5, 10, and 17 years. Cephalometric and diagnostic cast analyses were the methods performed to evaluate jaw growth patterns. Linear and angular measurements obtained after denture rehabilitation were averaged and compared with mean standard values of nearly corresponding ages, as given by Sakamoto and Bolton. Conversely, alveolar ridge arch width and length were evaluated for their dimensional changes during the same age intervals. Mann-Whitney U-test was used to check the difference between the groups. The significance of the level adopted was 5%. Nasion-anterior nasal spine, anterior nasal spine-menton, anterior nasal spine-pterygomaxillary fissure, gonion-sella, and gonion-menton lengths were found to be not statistically significant than the mean standard values of nearly corresponding ages (P > 0.05). The decrease in facial plane angle, increase in Y-axis angle, and mandibular plane angle after complete denture rehabilitation were statistically significant when compared to their mean standard values (P < 0.05). Cast analysis showed more increase in the length compared to the width in both arches. Complete denture rehabilitation did not significantly affect the jaw growth pattern, although it improved facial esthetics and masticatory activity by establishing adequate vertical dimensions.

The Difference in Electromyographic Activity While Wearing a Medical Mask in Women with and without Temporomandibular Disorders

Wearing a medical mask influences resting activity of the temporalis anterior and masseter muscles in healthy young women. However, no studies link medical mask-wearing with masticatory muscle activity in patients with temporomandibular disorders (TMDs). Therefore, this study aims to compare electromyographic patterns while wearing a medical mask between women with and without temporomandibular disorders. Based on the Research Diagnostic Criteria for Temporomandibular Disorders, 115 adult women qualified for the study. Participants were divided into the following two groups: diagnosed TMDs (n = 55; mean age: 23.5 ± 2.3 years) and healthy women (n = 60; mean age: 23.7 ± 2.6 years). Examinations of the resting and functional electromyographic activity of the temporalis anterior (TA), superficial masseter (MM), anterior bellies of the digastric muscle (DA), and the middle part of the sternocleidomastoid muscle (SCM) were carried out using the BioEMG III™. Both groups showed statistically significant decreases in resting masticatory muscle activity during medical mask examination compared to no mask measurement. The significant differences in no mask measurement between both groups were noted regarding resting masticatory activity, clenching in the intercuspal position, and clenching on dental cotton rollers. During medical mask examination, women with TMDs showed differences in resting masticatory activity and clenching on dental cotton rollers compared to the healthy group. In all analyzed variables, both groups showed similar electromyographic patterns in the maximum mouth opening measurement during medical mask and no mask examination. A medical mask influences the resting bioelectric activity of the masticatory muscles in women with temporomandibular disorders and healthy women. We observed differences and some similarities in resting and functional electromyographic patterns within masticatory and neck muscles in both groups during medical mask and no mask examination.

Impact of habitual chewing on gut motility via microbiota transition

The gut environment, including the microbiota and its metabolites and short-chain fatty acids (SCFA), is essential for health maintenance. It is considered that functional recovery treatment for masticatory dysphagia affects the composition of the gut microbiota, indicating that habitual mastication, depending on the hardness of the food, may affect the gut microbiota and environment. However, the impact of chronic powdered diet feeding on the colonic condition and motility remains unclear. Here, we evaluated various colonic features in mice fed with powdered diets for a long-term and a mouse model with masticatory behavior. We observed a decreased abundance of the SCFA-producing bacterial genera in the ceca of the powdered diet-fed mice. Based on the importance of SCFAs in gut immune homeostasis and motility, interestingly, powdered diet feeding also resulted in constipation-like symptoms due to mild colitis, which were ameliorated by the administration of a neutrophil-depleting agent and neutrophil elastase inhibitors. Lastly, the suppressed colonic motility in the powdered diet-fed mice was significantly improved by loading masticatory activity for 2 h. Thus, feeding habits with appropriate masticatory activity and stimulation may play a key role in providing a favorable gut environment based on interactions between the gut microbiota and host immune system.

The Sedentary Lifestyle and Masticatory Dysfunction: Time to Review the Contribution to Age-Associated Cognitive Decline and Astrocyte Morphotypes in the Dentate Gyrus.

As aging and cognitive decline progresses, the impact of a sedentary lifestyle on the appearance of environment-dependent cellular morphologies in the brain becomes more apparent. Sedentary living is also associated with poor oral health, which is known to correlate with the rate of cognitive decline. Here, we will review the evidence for the interplay between mastication and environmental enrichment and assess the impact of each on the structure of the brain. In previous studies, we explored the relationship between behavior and the morphological features of dentate gyrus glial fibrillary acidic protein (GFAP)-positive astrocytes during aging in contrasting environments and in the context of induced masticatory dysfunction. Hierarchical cluster and discriminant analysis of GFAP-positive astrocytes from the dentate gyrus molecular layer revealed that the proportion of AST1 (astrocyte arbors with greater complexity phenotype) and AST2 (lower complexity) are differentially affected by environment, aging and masticatory dysfunction, but the relationship is not straightforward. Here we re-evaluated our previous reconstructions by comparing dorsal and ventral astrocyte morphologies in the dentate gyrus, and we found that morphological complexity was the variable that contributed most to cluster formation across the experimental groups. In general, reducing masticatory activity increases astrocyte morphological complexity, and the effect is most marked in the ventral dentate gyrus, whereas the effect of environment was more marked in the dorsal dentate gyrus. All morphotypes retained their basic structural organization in intact tissue, suggesting that they are subtypes with a non-proliferative astrocyte profile. In summary, the increased complexity of astrocytes in situations where neuronal loss and behavioral deficits are present is counterintuitive, but highlights the need to better understand the role of the astrocyte in these conditions.

Morphometric anlaysis of mandibular coronoid, condyle and sigmoid shape using panoromic view for personal identification in south Indian population.

ObjectiveThe shape of the condyle, coronoid, and the intervening sigmoid notch is unique due to attachments and direction of pull of temporalis muscle, different chewing habits, hormones, etc. So morphometric variation of these mandibular landmarks can be used in individual identification.Material And MethodsThe study was carried out on 500 panoramic view images. Visual tracing assisted assessment of thousand sides (left and right) was done. Sexual dimorphism of left and right mandibular ramus parts (sigmoid notch bordered by coronoid and condylar process). The shape of coronoid process, condyle, and sigmoid notch were interpreted.ResultsThe most prevalent shape of sigmoid notch was wide variant (41.2%), condyle was convex type (50%) and coronoid was round (53.4%). Condyle and coronoid showed asymmetry between right and left with p-value 0.001 and 0.019, respectively. This study has illustrated that triangular-shaped coronoid was more in females (p-value 0.012).ConclusionSexual dimorphism is observed in the shape of the mandible due to masticatory activity at the point of insertion of temporalis muscle, biting force, hormones, and various genetic reasons. The results have exemplified that the morphometric variation of condyle, coronoid and sigmoid notch can be used as a tool for personal identification.

Electromyographic Study of Masticatory Muscle Function in Children with Down Syndrome.

This study assessed the electrical activity of the masticatory muscles in both children with down syndrome (DS) and healthy children. After applying the inclusion and exclusion criteria, 30 patients aged between 7.9 and 11.8 years participated in the study. They were divided into two groups of 15: DS and non-DS. A DAB-Bluetooth device (Zebris Medical GmbH, Germany) was used to record the electromyographical (EMG) activity of the right and left temporal and of the right and left masseter muscles at rest and during maximum voluntary clenching (MVC). The asymmetry index between right and left masticatory muscle EMG activity was calculated for each position. The Mann–Whitney U test was applied to analyze the study results. There were no differences in the electrical activity of the temporal and masseter muscles at rest between the groups. During MVC, the asymmetry index for the masseter muscles was significantly higher in subjects with DS. The electrical potentials of the temporal and masseter muscles in children with DS were significantly lower compared to the corresponding parameters for healthy children when clenching.

Evaluation of Stomatognathic System Parameters After Bariatric Surgery.

The present study aimed to evaluate electromyographic activity, bite strength, and masticatory muscle thickness in women without obesity and with severe obesity elected for bariatric surgery. Also, patients with obesity underwent bariatric surgery and were re-evaluated 3 and 6months after surgery to analyze the influence of bariatric surgery outcomes on the stomatognathic system, a functional anatomical system comprising teeth, jaw, and associated soft tissues. Thirty-seven women were enrolled in the study. Twenty-one women with class II and III obesity according to the body mass index (BMI) and eligible for bariatric surgery composed the obesity pre-surgery group (Ob). Sixteen women with a normal weight according to BMI composed the non-obesity group (NOb). Afterward, the patients from the Ob group were followed up for 3 and 6months after undergoing Roux-en-Y gastric bypass. Anthropometry, body composition, and parameters of the stomatognathic system were evaluated. The stomatognathic system of the Ob group had less muscle activity and bite strength, but the thickness of masseter and temporal muscles was larger than the NOb group. We also observed a significant change in the muscular activity and bit strength of the stomatognathic system post-bariatric surgery. Evaluating the stomatognathic system indicated that women with clinically severe obesity have less masticatory efficiency than non-obese. Also, we found a positive influence of bariatric surgery in masticatory activity after 3 and 6months. Thus, monitoring the parameters of the stomatognathic system could be important in the indication and outcomes of bariatric surgery.

Preclinical study of additive manufactured plates with shortened lengths for complete mandible reconstruction: Design, biomechanics simulation, and fixation stability assessment

BackgroundA combination of short titanium plates fabricated using additive manufacturing (AM) provides multiple advantages for complete mandible reconstruction, such as the minimisation of inherent implant deformation formed during AM and the resulting clinical impact, as well as greater flexibility for surgical operation. However, the biomechanical feasibility of this strategy is still unclear, and therefore needs to be explored. MethodThree different combinations of short mandible reconstruction plates (MRPs) were customised considering implant deformation during the AM process. The resulting biomechanical performance was analysed by finite element analysis (FEA) and compared to a conventional single long MRP. ResultsThe combination of a long plate and a short plate (Design 3 [LL61 mm/RL166 mm]) shows superior biomechanical properties to the conventional single long plate (Design 1 [TL246 mm]) and reveals the most reliable fixation stability among the three designs with short plates. Compared to conventional Design 1, Design 3 provides higher plate safety (maximum tensile stress on plates reduced by 6.3%), lower system fixation instability (relative total displacement reduced by 41.4%), and good bone segment stability (bone segment dislocation below 42.1 μm) under masticatory activities. ConclusionsPreclinical evidence supports the biomechanical feasibility of using short MRPs for complete mandible reconstruction. Furthermore, the results could also provide valuable information when treating other large-sized bone defects using short customised implants, expanding the potential of AM for use in implant applications.