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Objective: The purpose of this study was to analyze and compare the differences in chewing efficiency among patients with different vertical skeletal types of Angle Class I and Angle Class II malocclusions, to provide reference for orthodontic clinical practice. Method and materials: Sample size estimation revealed a minimum of 53 for each class. Thus, a total of 108 patients with Angle Class I and Angle Class II malocclusions were selected. Lateral skull radiographs were taken, and head measurements were analyzed via geometric tracing software. Chewing efficiency was measured using the gravimetric method to compare between the two groups. The vertical skeletal pattern was classified via Steiner analysis. Results: Significant statistical differences in chewing efficiency were observed between patients presenting with Angle Class I and Angle Class II malocclusions (P<.05). Additionally, significant differences in chewing efficiency were observed among patients with different vertical skeletal patterns (P<.05). Furthermore, a statistically significant difference in chewing efficiency was found between men and women (P<.05). Conclusions: Patients with Angle Class I malocclusions exhibited significantly higher chewing efficiency compared to those with Angle Class II malocclusions. Among patients with different vertical facial types, the chewing efficiency followed theorderof low angle> normal angle> high angle. Moreover, men demonstrated a higher chewing efficiency than women. [ABSTRACT FROM AUTHOR]

The present study assessed the impact of a fixed prosthetic rehabilitation on masticatory function in patients diagnosed with stage IV periodontitis. Eligible participants were adults in need of complex rehabilitation due to masticatory dysfunction. Masticatory function was evaluated using the two‐ colored chewing gum mixing ability test (VOH) at the diagnostic phase (T0), 1 week after delivery of the prosthetic prototype (T1), and 1 week after delivery of the final prosthetic solution (T2). Ten subjects were treated with a fixed prosthesis following periodontal and implant surgery using an individualized, fully digital workflow. Full-mouth plaque and bleeding scores, pocket depth, and clinical attachment level improved significantly. VOH was 0.472 ± 0.168 at T0, 0.358 ± 0.166 at T1, and 0.250 ± 0.123 at T2. A significant improvement in VOH was observed from T0 to T1 (difference: –0.114; 95% CI: –0.199 to –0.029; P = .014) and from T1 to T2 (difference: –0.108; 95% CI: –0.200 to –0.015; P = .027). From T0 to T2, VOH increased by 44.3%. Self-perceived assessment of masticatory function also improved from T0 to T2 (P = .002). The fixed prosthetic rehabilitation in patients with stage IV periodontitis allowed for a significant improvement in objective and subjective measurements of masticatory function. [ABSTRACT FROM AUTHOR]

The management of horizontally fully edentulous atrophic ridges is a common problem in dental implantology. This case report describes an alternative modified two-stage presplitting technique. The patient was referred for an implantsupported rehabilitation of their edentulous mandible. CBCT scans showed a mean available bone width of about 3 mm. At the first stage, four linear corticotomies were performed using a piezoelectric surgical device. At the second surgical stage 4 weeks later, bone expansion was performed, and four implants were placed in the interforaminal area. The healing process was uneventful. No fractures of the buccal wall and no neurologic lesions were observed. Postoperative CBCT scans showed a mean bone width gain of about 3.7 mm. Implants were uncovered 6 months after the second surgery, and 1 month later, a fixed provisional screw-retained prosthesis was delivered. This approach could be used as a reconstructive technique that avoids using grafts and reduces treatment times, possible complications, postsurgical morbidity, and costs by exploiting the patient's native bone as much as possible. Considering the limitations of a case report, randomized controlled clinical trials are needed to confirm the results and validate this technique. [ABSTRACT FROM AUTHOR]

Objectives: Work in animal models has implicated excessive occlusal forces and occlusal trauma as co-destructive factors for periodontitis. The main aim of the present study was to make a radiographic assessment of the effects of excessive occlusal forces, ie occlusal/incisal tooth wear, widening of the periodontal space, and the presence of a mandibular torus, on interproximal marginal bone loss in a large series of patients. A secondary aim was to evaluate the statistical correlation between the parameters in two specific teeth and those of 12 teeth for marginal bone loss and six teeth for occlusal/incisal tooth wear within the same individual. Method and materials: A total of 1,950 full-mouth radiographic surveys were analyzed retrospectively. Interproximal marginal bone loss was quantified relative to the root length (Schei ruler technique). In addition, occlusal/incisal tooth wear and periodontal ligament space widening of the periodontal space were assessed, as well as the presence of a mandibular torus. Odds ratio and logistic regression analysis were used to determine the association between occlusal trauma and marginal bone loss. Results: The correlation of the measured parameters between the values for specific teeth and the whole dentition was evaluated from data from the first 400 radiographs. Teeth 41 and 33 showed the best correlation to the whole dentition: 0.85 for interproximal marginal bone loss, 0.83 for widening of the periodontal space, and 0.97 forocclusal/incisal tooth wear. The results of a logistic regression analysis with age as an independent variable, revealed a significant association between bone loss and both tooth wear (odds ratio = 2.767) and bone loss and widening of the periodontal space (odds ratio = 2.585). Conclusion: Tooth wear was positively correlated to both widening of the periodontal space and marginal bone loss. No correlation was found between the presence of a mandibular torus and marginal bone loss. [ABSTRACT FROM AUTHOR]

Background: An integral component of comprehensive temporomandibular disorder (TMD) treatment involves what is commonly referred to in literature as patient counselling or patient education. Despite its importance, a clear definition of the concept is lacking. Objectives: To describe the concept of counselling (i.e. what is it, what should it consist of, and when should it be given) through a concept analysis of the literature. Eligibility Criteria: All papers that include a description of counselling or education for TMD are included. Sources of Evidence: Literature searches were performed in the electronic databases PubMed, Cinahl, and PsycInfo. Charting Methods: A qualitative analysis was done using the principle‐based concept analysis approach, where descriptions of counselling from the included papers were analysed by the researchers. Results: A total of 71 articles were included. Based on the qualitative analysis of the included articles and descriptions of counselling, the following content themes were identified: (1) general information on TMD; (2) overuse of the masticatory system; (3) posture education; (4) lifestyle and psychosocial factors; (5) exercise‐ and thermotherapy; and (6) additional information and therapies. Conclusions: A definition and framework of counselling for TMD has been provided, which can be used in the clinic, research, and educational programs. [ABSTRACT FROM AUTHOR]

Background: The literature is unclear about how the different attachment systems for overdentures impact the maximum bite force, the masticatory efficiency and how this impact in the oral health self‐perception in patients. Objective: To evaluate the effect of two attachment systems (O‐ring and Locator) for mandibular overdenture using single implant on quality of life, maximum bite force (BF) and masticatory efficiency (ME). Methods: Twenty‐eight completely edentulous denture wearers with a mandibular symphysis implant were randomly selected and allocated into two groups in a crossover study, considering O‐ring and Locator attachment types. The quality of life and self‐perception of oral health were assessed using the Oral Health Impact Profile (OHIP‐Edent) and Geriatric Index of Determination of Oral Health (GOHAI) questionnaires, respectively. BF was measured using a gnathodynamometer and ME by chewing silicone cubes and almonds in different numbers of cycles. Results: There was no difference between the attachment systems about self‐perceived oral health and impact on quality of life (p >.05). The O‐ring‐type system obtained a significantly higher BF than the locator‐type system (p =.04). Regardless of the food chewed, no statistically significant difference was observed with the type of attachment (p >.05). The ME was directly proportional to the masticatory cycles only for almonds (p <.01). Conclusions: Locator and O‐ring inserts had a similar impact on patients' quality of life, self‐perception of oral health and ME. Additionally, the O‐ring system exhibited superior properties in the BF. [ABSTRACT FROM AUTHOR]

Objective: To detect whether myotatic reflex activation of masticatory muscles during drug-induced sleep endoscopy (DISE) can be an indirect marker for temporomandibular disorder (TMD) in patients suffering from obstructive sleep apnea (OSA). Methods: OSA patients were prospectively recruited and underwent a complete TMD examination prior to undergoing DISE with the addition of electrodes applied over masticatory muscles. A positive activation of myotatic reflex was considered in case of an increase in muscle tone of at least 50%. Results: Of the 41 patients included, 48.8% presented activation of myotatic reflex. Of these patients, 45% presented a TMD diagnosis, 40% presented pain at masticatory muscles palpation, and 15% did not report pain during clinical examination. Conclusion: An increase in EMG activity during mandibular advancement is not associated with TMD presence, but it can be an indirect marker of pain in the orofacial area in OSA patients. [ABSTRACT FROM AUTHOR]

Objective: To determine the role of emotional state in the masticatory system function in a group of young adults. Methods: Ninety-six generally healthy randomly selected students aged 18–21 were examined. They were subjected to a questionnaire survey determining their emotional state, clinical examination, and instrumental diagnostics (EMG, Cadiax Compact, JVA). Results: The stress symptoms group revealed a greater intensity of neck and shoulder muscles pain (p < 0.05) and an increase of electrical potential of the masseter muscles in maximal voluntary clench (p < 0.05). They reported more often headache (p < 0.001), tension/contracture of the head, neck and nape (p < 0.05), and pain while opening the mouth wide (p < 0.05). The values of parameters obtained in the instrumental diagnostics did not reveal differences between the groups. Conclusion: Stressful situations increase muscular tension but do not have a direct impact on the temporomandibular joints function. [ABSTRACT FROM AUTHOR]

Background: Cancer cachexia is prevalent in head and neck cancer patients. The L3 skeletal muscle index (SMI) is often used to assess sarcopenia and cachexia but is infrequently able to be measured in this population. Masseter muscle thickness (MT) may serve as an alternative predictor of cachexia. Methods: SMI and MT were calculated from 20 trauma (CTRL) and 40 cachectic (CA‐CX) and non‐cachectic (CA‐NCX) head and neck cancer patients. Area Under the Curve of the Receiver Operating Characteristics (AUC‐ROC) analysis was performed for SMI and MT. Results: Both SMI and MT were significantly decreased in CA‐CX patients (vs. CA‐NCX mean difference −19.5 cm2/m2 and −2.06 mm, respectively) and significant predictors of CA‐CX (AUC = 0.985 and 0.805, respectively). When analyzed by sex, the same findings were observed for MT in males and trended toward significance in females. Conclusions: Compared with SMI, MT is a good alternative prognostic biomarker to determine CA‐CX status in HNC patients. [ABSTRACT FROM AUTHOR]

ABSTRACT Background Objective Methods Results Conclusion Temporomandibular disorders (TMD) are multifactorial musculoskeletal pain and dysfunctions in temporomandibular joints (TMJs) and masticatory muscles. Genetic factors play a role in TMD‐related pain, but only a few genome‐wide association studies (GWAS) have been conducted.The aim of this GWAS was to explore genetic factors associated with painful TMD in Finnish populations.Data from two epidemiological surveys, the Northern Finland Birth Cohort 1966 (NFBC1966) and the Health 2000 Survey in Finland, including altogether 468 cases and 6833 controls, were used. Case definition was based on pain on palpation of masticatory muscles and/or TMJs. GWASs of the whole data and stratified by sex were conducted from both cohorts using additive models, followed by meta‐analysis of the two cohorts. Replications of the previously reported TMD risk loci (rs73460075, DMD; rs4794106, SGCA; rs73271865, SP4; rs60249166, RXP2; rs1531554, BAHCCI; rs5862730, OTUD4/SMAD1; rs10092633, SFRP1; rs34612513, SOX14/CLDN18; rs878962, TSPAN9) were also investigated.Four genome‐wide significant loci were found in sex‐stratified analysis of NFBC1966, including associations at three loci in males (rs1023114, PRIM2, p = 5 × 10−9; rs4244867, ALG10, p = 3 × 10−8; rs79841648, ADCYAP1, p = 4 × 10−9) and one locus in females (rs148476652, DNER, p = 4 × 10−9). However, the results could not be replicated in the Health 2000 Survey or in the meta‐analysis of these two cohorts. The previous TMD GWAS associations did not replicate in our data either.Several TMD pain‐associated variants were found in sex‐stratified analysis of NFBC1966, suggesting the role of neuroendocrine stress responses and central nervous system. These findings need to be confirmed in future studies. [ABSTRACT FROM AUTHOR]

Objectives: The Functional Clear Aligner (FCA) is a novel orthodontic appliance designed for the treatment of Class II malocclusion with mandibular retrognathia in adolescents. The aim of this study was to investigate the biomechanical characteristics of the masticatory muscles, jawbone, and temporomandibular joint (TMJ) during mandibular advancement using either FCA or Class II elastics combined with clear aligner (Class II elastics) through finite element analysis. Materials and methods: A 3D finite element model of the 'muscle-jawbone-TMJ-appliance' system was constructed based on CBCT and MRI images of a boy with skeletal Class II malocclusion. Masticatory muscles included masseter, temporal, medial pterygoid, and lateral pterygoid muscles. The TMJ consists of the temporal bone's glenoid fossa, disc, and mandibular condyle. To observe the biomechanical characteristics of the muscles and TMJ during orthodontic appliance wearing and the retention phase, two different protocols were used: Model 1: The mandibular advancement using FCA; Model 2: The mandibular advancement using Class II elastics. Results: The FCA group produced greater and more coordinated masticatory muscle forces compared to the Class II elastics group. Temporal and masseter muscles exhibited the most pronounced variation in muscle strength during mandibular advancement. The FCA group exhibited greater TMJ region stress compared to the Class II elastics group. Interestingly, the stress on the articular discs in both models decreased over time. Tensile stresses were observed in both the condyle and the posterior region of the articular fossa. Conclusion: During skeletal Class II malocclusion treatment, masticatory muscle forces and stress on the TMJ were higher in the FCA group compared to the Class II elastics group. In both models, stress cushioning was provided by the articular disc. [ABSTRACT FROM AUTHOR]

Background: Disorders affecting the temporomandibular joint (TMJ), related structures, and the masticatory muscles are called temporomandibular disorders (TMD). The two most typical symptoms are mouth opening restriction and pain. Costen noted the connection between TMD and tinnitus in 1934. These conditions are brought about by the shared structures that connect the TMJ and the auditory apparatus (bones and muscles) through a shared innervation source and specific ligaments. Wright addresses Costen ideas, which suggest that otological symptoms of TMD could be caused by auriculotemporal nerve damage, Eustachian tube restriction, or other factors causing an incorrect intratympanic pressure adjustment. Methods: Cross-sectional observation was regulated at Oral and Maxillofacial Surgery Department, Faculty of Dentistry, Cairo University. The following are the inclusion criteria: patients with a TMD diagnosis and those older than 16 years old. The following conditions are excluded: neurological or oncological disorders, ear infection, and a history of face trauma. Results: The total number was 196 patients, 63.8% females and 36.2% males. A total of 76.5% had bilateral joint pain, and 21.9% had unilateral joint pain. While 70.4% had bilateral muscle pain, 18.9% had unilateral muscle pain. A total of 91.8% had mild tinnitus, while 8.2% had moderate tinnitus. Conclusion: In this study, 8.2% of patients complaining of tinnitus had severe tinnitus, while 91.8% had mild tinnitus. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) progressively impairs motor neurons, leading to muscle weakness and loss of voluntary muscle control. This study compared the effects of SOD1 mutation on masticatory and limb muscles from disease onset to death in ALS model mice. Notably, limb muscles begin to atrophy soon after ALS-like phenotype appear, whereas masticatory muscles maintain their volume and function in later stages. Our analysis showed that, unlike limb muscles, masticatory muscles retain their normal structure and cell makeup throughout most of the disease course. We found an increase in the number of muscle satellite cells (SCs), which are essential for muscle repair, in masticatory muscles. In addition, we observed no reduction in the number of muscle nuclei and no muscle fibre-type switching in masticatory muscles. This indicates that masticatory muscles have a higher resistance to ALS-related damage than limb muscles, likely because of differences in cell composition and repair mechanisms. Understanding why masticatory muscles are less affected by ALS could lead to the development of new treatments. This study highlights the importance of studying different muscle groups in ALS to clarify disease aetiology and mechanisms. [ABSTRACT FROM AUTHOR]

Background: It is widely recognized that periodontal disease is associated with diabetes mellitus. Periodontal disease is accompanied by inflammation of the periodontal tissue, impaired masticatory function, and the presence of periodontopathic bacteria, all of which may affect glycemic control. However, the exact relationship between these factors and glycemic control has not yet been established. In this study, we aimed to investigate the relationship between periodontal disease-related factors and glycemic control in Japanese community-dwelling individuals. Methods: We conducted a cross-sectional study involving 671 participants aged 29–92 (65.3 ± 12.1) years, using data from the Nagasaki Islands Study. Participants underwent routine medical examinations, including body mass index (BMI) and hemoglobin A1c (HbA1c) levels. Information on the participants' demographics (age and sex) and whether they were on diabetes medications, had an exercise habit, consumed alcohol, engaged in late-night eating, had regular dental checkups, and smoked was obtained using a self-administered questionnaire. Dental examinations were performed to examine dentition status, probing pocket depth, clinical attachment level (CAL), and bleeding on probing. Functional tooth units (FTUs), defined as pairs of occluding posterior teeth, were used as an indicator of occlusal support area. Saliva samples were collected and levels of two species of periodontopathic bacteria (Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans) were determined using real-time polymerase chain reaction. We analyzed the association between HbA1c levels and variables related to periodontal status, masticatory function, and salivary levels of periodontopathic bacteria. Results: Bivariate analysis showed that HbA1c levels were significantly associated with age, sex, exercise habit, BMI, diabetes medications, CAL, salivary P. gingivalis level, number of teeth, and three FTU subcategories. In the multiple regression analysis, age, BMI, diabetes medications, and total FTU score (i.e., including natural teeth, implant-supported artificial teeth, fixed prostheses, and removable dentures) remained associated with HbA1c levels (B = 0.23, 0.14, 0.52, and − 0.12; p < 0.001, p < 0.001, p < 0.001, and p = 0.008, respectively). Conclusions: In this community-based cross-sectional study, total FTU was significantly associated with HbA1c levels, independent of other risk factors. This suggests that reconstructed occlusal support areas, including dentures, are associated with glycemic control in the older population. [ABSTRACT FROM AUTHOR]

Masticatory muscle forces influence craniofacial morphology development. The antegonial notch (Notch) is a bony concavity on the inferior border of the mandible. Considering the Notch is located anteriorly to the insertion of the masseter muscle and varies among individuals, we hypothesised that these muscles influence the formation of the Notch. Therefore, this study aimed to investigate the correlation between mandible morphology and Notch formation. Sixty Japanese patients who visited the Department of Orthodontics at our university hospital were retrospectively evaluated. Morphological and morphometric analyses of the Notch and related craniofacial parameters were conducted using lateral cephalograms taken at the patients' initial visits. Standard values for the Notch area and depth were determined, and the morphology of the Notch and mandible was analysed using Spearman's rank correlation coefficient (p < 0.05). The mean Notch area and depth was 78.71 ± 36.54 mm2 and 3.11 ± 1.09 mm, respectively. The Notch area was significantly correlated with ramus inclination (p = 0.044, r = 0.261) and with the Y-axis (p = 0.039, r = 0.267). This study indicated that both the masticatory muscles and mandibular growth could contribute to the Notch formation. [ABSTRACT FROM AUTHOR]

Background: Sleep‐related bruxism (SB) is the habit of grinding or clenching the teeth during sleep, mediated by the non‐peripheral central nervous system. Purpose: The objectives of this cross‐sectional study were to evaluate associations between SB, microarousals and oxyhaemoglobin desaturations and to compare the frequency of SB and microarousals in sleep stages, in an apnoeic population. Methods: Two hundred and forty individuals composed the sample, who underwent a single full‐night polysomnography. Self‐reports and clinical inspections were not considered for assessing SB. The polysomnographic assessment of SB was performed using electrodes placed on masseter muscles and chin. SB was defined as more than two events of rhythmic masticatory muscle activity per hour of sleep. Microarousals were considered when there were abrupt changes in electroencephalogram frequencies, without complete awakening, lasting from 3 to 15 s. Oxyhaemoglobin desaturations were defined as significant drops (≥3%) in basal oxygen saturations. With these data, SB, microarousals and oxyhaemoglobin desaturations were evaluated and submitted to statistical analysis. Results: Statistically significant differences were observed between bruxers and non‐bruxers when comparing the rates of microarousals (p <.001) and oxyhaemoglobin desaturations (p =.038). There was a higher number of SB and microarousals in NREM (non‐rapid eye movement) two sleep stage (p < 0.001). Bruxers had a greater risk of higher numbers of microarousals (OR = 1.023; p =.003), which did not occur for oxyhaemoglobin desaturations (OR = 0.998; p =.741). Conclusions: A higher number of microarousals presents relationship with SB; associations between SB and oxyhaemoglobin desaturations remained inconclusive; higher frequency of SB and microarousals was observed in NREM 2 sleep stage. [ABSTRACT FROM AUTHOR]

Background: Oral and social problems can exacerbate long‐term care. Understanding the relationship between social aspects and oral hypofunction can help identify high‐risk factors for long‐term care. Objective: This study aimed to investigate the social aspects of oral hypofunction among medical outpatients. Methods: This retrospective cross‐sectional study included patients who visited an outpatient clinic for frailty. The oral function was assessed using seven items: oral hygiene, occlusal force, masticatory function, tongue‐lip motor function, tongue pressure, oral dryness and swallowing function. Participants with three or more functional declines were classified as having 'oral hypofunction'. Social aspects were assessed using 21 items in four categories: general resources, basic social needs, social resources and social behaviours/activities. We analysed the relationship between oral hypofunction and each social aspect. Results: A total of 316 participants (age 78.5 ± 6.4 years) were included, and 128 (41%) had oral hypofunction. Participants with oral hypofunction were significantly more likely to have limited education, require long‐term care, not use transportation, depend on others for shopping, not participate in events, lack association membership and not engage in charity or volunteer work. After logistic regression analysis, 'long‐term care' and 'no association membership' remained significantly associated with oral hypofunction (odds ratios 2.3, 2.3; 95% CI 1.1–5.0, 1.1–4.7, respectively). Conclusion: Participants with oral hypofunction faced challenges in 'general resources' and 'social behaviour/activities', which were linked to oral function issues. Future longitudinal studies are necessary to further investigate this relationship. [ABSTRACT FROM AUTHOR]

Objective: To identify the available evidence on the ultrasonographic characteristics of masticatory muscles in subjects with myogenous TMD, as well as the potential use of ultrasonography as a diagnostic and treatment assessment outcomes tool. Method: An electronic search of the PubMed, Web of Science and Scopus databases was performed using the following terms: 'ultrasonography', 'ultrasound', 'masseter', 'temporal', 'masticatory muscles', 'temporomandibular disorders', 'temporomandibular joint disorders'. Full‐text articles were obtained from the records after applying the inclusion/exclusion criteria. Results: Thirteen articles were included for analysis: one comparative cross‐sectional study, five case–control studies, six clinical trials and one randomised clinical trial. Main ultrasonographic characteristic assessed were local cross‐sectional dimension and intramuscular ultrasonographic appearance. Retrieved studies reported the use ultrasonography for diagnosis or treatment assessment purposes showing heterogeneous results. For diagnosis purposes, the results of local cross‐sectional dimension are not consistent; therefore, its diagnostic value for myogenous TMD diagnosis is weak. However, more homogeneous results were observed for intramuscular ultrasonographic appearance showing a higher prevalence of type‐II pattern in myogenous TMD subjects than non‐TMD subjects. On the other hand, for treatment assessment purposes, muscles were observed thinner after treatment compared to pre‐treatment. Also, results of intramuscular ultrasonographic appearance show disappearance or reduction of anechoic areas, higher prevalence of type‐II pattern and significant distinction of echogenic bands were observed after treating TMD subjects. Conclusion: Ultrasonography cannot be considered as a diagnostic instrument, but maybe as a complementary tool for treatment assessment of myogenous TMD subjects, even though future research is required to confirm its utility. [ABSTRACT FROM AUTHOR]

Objective: This study aims to evaluate the effects on bite force and muscle thickness of the botulinum toxin (BoNT) injection for patients with sleep bruxism (SB) by comparing injections into the masseter muscle only and both the masseter and the anterior belly of the digastric muscle (ABDM) in a clinical trial. Methods: Twelve SB patients received BoNT‐A injections using US‐guided techniques into the masseter muscle only (Group A), while the remaining 12 SB patients received injections into both the masseter and ABDM (Group B). Bite force and muscle thickness were measured before injection, as well as 1 and 2 months after injection. Results: The bite force and masseter muscle thickness decreased in both Group A and Group B before injection, and at 1 and 2 months after injection. However, there was no significant difference (p >.05, repeated measures analysis of variance) between the two groups, and there was also no significant difference in ABDM thickness (p >.05, repeated measures analysis of variance). Conclusion: This study is the first to assess the short‐term effects of BoNT injected into ABDM for SB control. Results show no influence on SB reduction, suggesting the need for further research on BoNT's effectiveness in controlling intense ABDM contractions during sleep and assessing suprahyoid muscle potential impact on rhythmic masticatory muscle activity occurrence. [ABSTRACT FROM AUTHOR]

Background: Activation of β2 adrenergic receptors reduces cutaneous mechanical pain thresholds in rats. While β2 adrenergic receptor activation may contribute to mechanisms that underlie temporomandibular joint pain, its effect on masticatory muscle pain sensitivity is uncertain. Objectives: The current study sought to determine the extent to which β adrenergic receptors are expressed by masticatory muscle afferent fibres, and to assess the effect of local activation of these receptors on the mechanical sensitivity of masticatory muscle afferent fibres in rats. Methods: Trigeminal ganglion neurons that innervate the rat (n = 12) masseter muscle and lower lip were identified by tissue injection of fluorescent dyes and were then stained with antibodies against β1 or β2 adrenergic receptors. Extracellular recordings from 60 trigeminal ganglion neurons that innervate the masticatory muscle were undertaken in a second group of anaesthetised rats of both sexes (n = 37) to assess afferent mechanical activation thresholds. Thresholds were assessed before and after injection of the β adrenergic receptor agonists into masticatory muscle. Results: β1 and β2 adrenergic receptor expression was greater in labial skin than in masticatory muscle ganglion neurons (p <.05, one‐way ANOVA, Holm–Sidak test). There was a higher expression of β2 adrenergic receptors in masticatory muscle ganglion neurons in males than in females. The mixed β agonist isoproterenol increased afferent mechanical activation threshold in male but not female rats (p <.05, Mann–Whitney test). In male rats, salbutamol, a β2 selective agonist, also increased afferent mechanical activation threshold but hydralazine, a vasodilator, did not (p <.05, Mann–Whitney test). Conclusion: Activation of β2 adrenergic receptors decreases the mechanical sensitivity of masticatory muscle afferent fibres in a sex‐related manner. [ABSTRACT FROM AUTHOR]

Background: Orofacial myofunctional disorders (OMD) are often associated with limitations of oral ingestion of solid food. The Test of Masticating and Swallowing Solids (ToMaSS) is a simple diagnostic tool to assess and quantify oropharyngeal efficiency while eating a standardised cracker. Objectives: The objective of this study was to investigate the applicability and clinical utility of the ToMaSS in children with OMD. Methods: In this case–control study, data were collected from 18 children between 4 and 11 years with confirmed OMD. Inter‐rater reliability and age effects on the ToMaSS parameters were investigated and the specific performance profile of the OMD children was identified. Results: Inter‐rater reliability was excellent for the ToMaSS parameters 'bites' (ICC =.999), 'masticatory cycles' (ICC =.961), 'time'(ICC≧.999) and good for 'number of swallows' (ICC =.810). 'Masticatory cycles' and 'time' decreased as a function of age with a significant difference in the 'number of masticatory cycles' between the youngest (4–6 years) and oldest (10–14 years) participants (p =.006, Z = −2.739). Deviations from normative data in at least one of the four ToMaSS parameters were found in 90% of the OMD children with 'bites', and 'masticatory cycles' predominantly corresponding to the performances expected in typically‐developing children in younger age groups. Conclusions: The ToMaSS is a reliable diagnostic instrument and clinically useful to detect limited efficiency of oral solid bolus intake and specific impairments in chewing function and duration of food intake in children with OMD. Our data suggest that OMD is associated with delayed development of efficient solid bolus preparation. [ABSTRACT FROM AUTHOR]

Opossums (marsupials of the Didelphidae family) retain a generalized masticatory apparatus and tribosphenic molars, often used as models to understand the evolution of mastication in early therian mammals. Like all marsupials, their growth goes through a stage when pups complete their development while permanently attached to the mother's teats before weaning and starting feeding on their own. Yet, while the masticatory muscles of adults are known, as is the ontogeny of the cranium and mandible, the ontogenetic changes in the masticatory muscles remain unknown. Here we describe for the first time the changes in the masticatory muscles observed in lactating pups, and weaned juveniles, subadults, and adults in the White‐eared opossum, Didelphis albiventris, through dissection of 25 specimens and quantification of relative muscle masses, lines of actions and mechanical advantages whenever possible. We also assessed the scaling patterns of muscle masses and mechanical advantages through ontogeny. The main changes, as expected, were found between suckling and weaned specimens, although some changes still occurred from juveniles to adults. The adult adductor musculature is similar to the other Didelphis species already known, with a dominant m. temporalis that originates on the lateral wall of the skull, up to the sagittal and nuchal crests, and fills the zygomatic arch when inserting into the lateral and medial surfaces of the coronoid process, respectively through the pars superficialis and pars profunda. The m. masseter is also subdivided in superficial and deep bundles which originate posteriorly in the maxilla and zygomatic arch, and insert into the angular process and masseteric fossa in the mandible. The m. pterygoideus medialis originates from the palatine, the pterygoid bone and the alisphenoid, and it inserts on the angular process medially. Suckling pups showed muscles with more restricted attachments, reduced muscle lines of action, and less diversity in the fiber orientation. The absence of the postorbital constriction also resulted in a distinct morphology of the m. temporalis pars profunda, through two bundles, one anterior and one posterior, which insert more inferiorly into the mandible. These major changes can be related to the onset of mastication and to size‐related changes in growing weaned age classes. In general, all adductor muscles grew with positive allometry, and increased their fixation areas through, in part, the development of specific regions of the cranium and mandible. Their lines of action also increase and diversify along ontogeny. These changes can be related to the functional requirements for fixation during lactation, which shift to adduction and mastication movements after weaning. [ABSTRACT FROM AUTHOR]

This retrospective study examined the clinical outcomes and complications in 6 cases of compound Meige's syndrome, presenting with blepharospasm and masticatory muscle spasm, following treatment with CT-guided radiofrequency ablation targeting bilateral facial nerves and mandibular branches of the trigeminal nerve. After the operation, the symptoms of eyelid spasm and masticatory muscle spasm resolved, but mild facial paralysis and numbness of mandibular nerve innervation persisted. Follow-up for 4–28 months showed that the symptoms of facial paralysis resolved within 2–5 (3.17 ± 0.94) months after the operation, whereas the numbness in the mandibular region persisted, accompanied by a decrease in masticatory function. During the follow-up period, none of the 6 patients experienced a recurrence of Meige's syndrome. These findings suggest that CT-guided radiofrequency ablation of the bilateral facial nerve and mandibular branches of the trigeminal nerve may offer a promising approach to treating compound Meige's syndrome. [ABSTRACT FROM AUTHOR]

Surface electromyography (sEMG) could be used for diagnostic and therapeutic purposes in various health conditions. For example, sEMG biofeedback is shown to be beneficial in adults with swallowing disorders (dysphagia), whereas there are no easily identifiable studies to support such evidence in paediatrics. The current review aimed to evaluate the feasibility of implementing sEMG during swallowing tasks in paediatric populations with various diagnoses. Additionally, the review aimed to describe findings in publications involving participants with cerebral palsy (CP) and dysphagia. Paediatric-related publications were sourced using English keywords and phrases across the following seven databases: PubMed, EMBASE, CINAHL, Web of Science, PsycINFO, and ProQuest Dissertations and Theses Global. The search included all available publications without language and date restrictions. Publications using sEMG during chewing tasks were also accepted in the review as chewing is considered to be part of the act of swallowing. The feasibility of measuring sEMG during swallowing in children with various health conditions was supported by 116 publications (n = 6 literature reviews) that met the inclusion criteria for the final full-text review. However, a few publications described some difficulties occurring directly during the sEMG data collection sessions. The review identified 15 publications involving 177 participants with CP who underwent sEMG while swallowing (n = 1 publication focused solely on the assessment of chewing). Ten publications described studies that recruited children with dysphagia. Children with CP who had dysphagia were recruited in five of these studies. Conclusions: The acquisition of sEMG measurements while performing swallowing tasks was shown to be feasible in children with various diagnoses including those who have CP and dysphagia. Future studies should investigate the implementation of sEMG as a part of paediatric dysphagia therapy alongside biofeedback swallowing skill training. What is Known: • Surface electromyography (sEMG) could be implemented for diagnostic and therapeutic purposes in various health conditions. • Biofeedback using sEMG is beneficial in adults with swallowing disorders (dysphagia). What is New: • Implementation of sEMG was shown to be feasible during swallowing tasks in paediatric populations with various diagnoses, including dysphagia and cerebral palsy. • The usage of sEMG biofeedback as a part of paediatric dysphagia management should be investigated in future studies. [ABSTRACT FROM AUTHOR]

Purpose: To analyze the functions of the stomatognathic system in children with or without molar-incisor hypomineralization (MIH). Methods: For this cross-sectional study, 72 children aged 6–12 years were recruited and divided in two groups: with MIH (G1) and without MIH (G2). T-SCAN was used to verify the distribution of occlusal contacts, gnathodynamometer to measure maximum molar bite force, and Iowa Oral Pressure Instrument (IOPI) to assess the strength of facial expression muscles. The t test and paired t test (p ≤ 0.05) were used for statistical comparisons. Results: The molars affected by MIH exhibited lower distribution of occlusal forces (p < 0.001) and lower maximum molar bite force (p < 0.05) compared to the molars in the control group. However, there was no difference between the MIH-affected sides compared to the unaffected side, nor between the molars affected by MIH and their antagonists (p > 0.05). There were no differences in the forces of the facial expression muscles between the groups. Conclusions: These findings suggest that MIH significantly impacts occlusal force distribution and bite force, but not facial expression musculature. [ABSTRACT FROM AUTHOR]

Fatigue of temporomandibular joint (TMJ) tissues reflects the effects of magnitude (energy density; ED) and frequency of loading (jaw muscle duty factor; DF). This observational study measured these variables and tested for differences in mechanobehavior scores (MBS = ED2 × DF) and component variables in subjects with and without TMJ disc displacement (±D). In accordance with Institutional Review Board and STROBE guidelines, written informed consent was obtained, and examination and imaging protocols identified eligible adult subjects. Specifically, magnetic resonance imaging was used to assign subjects' TMJs to ±D groups. Subjects were trained to record in-field jaw muscle activities, from which DFs (percentage of recording time) were determined. EDs (mJ/mm3) were estimated using modeled TMJ loads and in vivo dynamic stereometry. Multivariate analysis of variance, post hoc independent t tests, and K-means cluster analysis identified significant group differences (P < 0.05). Of 242 individuals screened, 65 females (TMJs: 78 +D, 52 −D) and 53 males (TMJs: 39 +D, 67 −D) participated. Subjects produced 312 daytime and 319 nighttime recordings of average duration 6.0 ± 0.2 h and 7.6 ± 0.1 h, respectively, and 219 (114 right, 105 left) intact dynamic stereometry recordings. Average EDs were 2-fold and significantly larger in +D than −D TMJs (P < 0.0001). DFs were on average 3-fold larger during the daytime versus nighttime for both masseter and temporalis muscles and 1.8- and 3.0-fold larger for the masseter versus temporalis muscle during the daytime and nighttime, respectively. Daytime masseter MBSs for +D TMJs in females were the largest overall at 621 ± 212 (mJ/mm3)2% and 2- to 43-fold larger versus −D TMJs in both sexes during daytime and nighttime. Cluster analysis (P < 0.0001) identified groups 2 and 3, which comprised 87% +D TMJs and had average MBSs 21-fold larger than group 1. The results show MBS as a potential biomarker to predict homeostasis versus progression or reversal of degenerative TMJ structural changes. [ABSTRACT FROM AUTHOR]

Purpose: Age-related changes to the swallowing mechanism, or presbyphagia, may put older adults at a higher risk for developing diseases and dysphagia. Maintaining swallowing functions could help prevent frailty and facilitate healthy ageing. This review summarises and appraises the effects of oropharyngeal exercises on the swallowing functions of healthy older adults without dysphagia. It is hypothesised that these exercises will strengthen and improve the structures and functions of the normal ageing swallow. Method: This review was reported according to the PRISMA 2020 guidelines. Five electronic databases (Medline, Embase, Cochrane Library, Web of Science, CINAHL) and Google Scholar were searched in June 2021. A rerun was done in January 2023. Study selection, data extraction, and quality assessment were done by two independent raters. Result: A total of 23 studies were reviewed. Meta-analysis was not conducted due to the heterogenous training protocols and outcomes. Majority (n = 21) had fair quality due to incomplete reporting. Exercises targeting oral structures were implemented the most (n = 15), followed by variations of the head lift (n = 4), and effortful swallow exercise (n = 1). Others implemented combined or multiapproach exercise studies (n = 3). Apart from surface electromyography findings, statistically significant improvements in oral and pharyngeal phase swallowing outcomes such as increased lingual isometric and swallowing pressures, bite force, muscle thickness, hyolaryngeal excursion, and upper oesophageal sphincter opening diameter were reported in 95% of the studies (n = 22). Conclusion: Collective evidence suggests that strength training for swallowing-related structures leads to increases in structural strength, endurance, and muscle mass. The effects of exercises on overall swallowing efficiency and safety remain unclear. Results should be interpreted with caution due to methodological limitations. Further research should examine the long-term effects of these exercises in preventing frailty and reducing the burden of dysphagia in older adults. [ABSTRACT FROM AUTHOR]

ABSTRACT Background Objectives Methods Results Conclusion Temporomandibular disorders (TMDs) are conditions that involve the temporomandibular joints, masticatory muscles, and associated tissues, causing orofacial pain. Central sensitisation (CS) is a relevant part of the TMD pathophysiology. Migraine, psychological aspects, parafunctional oral habits and widespread pain are commonly associated with both TMD and CS and could confound the association between them.To investigate the association between painful TMD and the Central Sensitisation Inventory (CSI) score, and to assess the presence of confounders in this association.Cross‐sectional study that assessed women with and without orofacial pain complaints using telehealth. The TMD Pain Screener and an online physical examination determined the presence of painful TMD. The following questionnaires were applied: CSI, Headache Screening Questionnaire, Generalized Anxiety Disorder‐7, Patient Health Questionnaire‐9, Oral Behavior Checklist, Jaw Functional Limitation Scale and the Nordic musculoskeletal questionnaire. A single regression investigated the association between the CSI score and TMD, and a multiple regression investigated the effect of the other outcomes as possible confounders. Confounding was considered present when the association between TMD and the CSI score changed more than 10% after adding a possible confounder to the regression model.Forty‐two women with painful TMD and 53 without TMD were included. There was a significant association between the CSI score and the presence of painful TMD (R2 = 0.639; p < 0.001). This association changed when the following outcomes were added to the model: presence of migraine, symptoms of depression, widespread pain and parafunctional oral habits.The positive association between TMD and the CSI score was confounded by migraine, symptoms of depression, widespread pain and parafunctional oral habits. [ABSTRACT FROM AUTHOR]

Background: The anatomic characteristics of the masticatory muscles differ across craniofacial skeletal patterns. Objective: To identify differences in the anatomic characteristics of masticatory muscles across different sagittal and vertical craniofacial skeletal patterns. Eligibility criteria: Studies measuring the thickness, width, cross-sectional area (CSA), volume and orientation of masticatory muscles in healthy patients of different sagittal (Class I, Class II, and Class III) and/or vertical (normodivergent, hypodivergent, and hyperdivergent) patterns. Information sources: Unrestricted literature searches in 8 electronic databases/registers until December 2023. Risk of bias and synthesis of results: Study selection, data extraction, and risk of bias assessment with a customised tool were performed independently in duplicate. Random-effects meta-analysis and assessment of the certainty of clinical recommendations with the GRADE approach were conducted. Results: 34 studies (37 publications) were selected with a total of 2047 participants and data from 16 studies were pulled in the meta-analysis. Masseter muscle thickness in relaxation was significantly greater by 1.14 mm (95% CI 0.74–1.53 mm) in hypodivergent compared to normodivergent patients while it was significantly decreased in hyperdivergent patients by − 1.14 mm (95% CI − 1.56 to − 0.73 mm) and − 2.28 mm (95% CI − 2.71 to − 1.85 mm) compared to normodivergent and hypodivergent patients respectively. Similar significant differences were seen between these groups in masseter muscle thickness during contraction as well as masseter muscle CSA and volume. Meta-analyses could not be performed for sagittal categorizations due to insufficient number of studies. Conclusions: Considerable differences in masseter muscle thickness, CSA and volume were found across vertical skeletal configurations being significantly reduced in hyperdivergent patients; however, results should be interpreted with caution due to the high risk of bias of the included studies. These variations in the anatomic characteristics of masticatory muscles among different craniofacial patterns could be part of the orthodontic diagnosis and treatment planning process. Registration: PROSPERO CRD42022371187. [ABSTRACT FROM AUTHOR]

(1) Background: This study aims to analyze the bioelectrical activity of the masticatory and cervical muscles in a subject with anisometropia. (2) Methods: A female patient aged 23 years with a best-corrected visual acuity of 1.0 in the right eye and 0.1 in the left eye, a refractive error of −2.25 Dsph in the right eye and +4.25 Dsph in the left eye, and astigmatism of −1.75 Dcyl axis 24° was examined. A comprehensive ophthalmological examination and the study of the bioelectrical activity of the muscles were carried out. During the ophthalmological examination, best-corrected visual acuity was determined, refractive error (spherical equivalent) was assessed, and additionally, retinal thickness, choroidal thickness, axial length, and intraocular pressure were measured. (3) Results: It was demonstrated that higher tension in the resting mandibular position and pain-free maximum unassisted opening were observed on the right side (myopia). Conversely, higher tension during maximum voluntary clenching in the intercuspal position and maximum voluntary clenching on dental cotton rolls in the intercuspal position was observed on the left side (hyperopia and astigmatism). (4) Conclusions: In the case study, muscle asymmetry was demonstrated, which is likely associated with anisometropia. This phenomenon requires further investigation. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to present three indicators that represent the proximal contact area gap change under intercuspal occlusion and to see if and how these indicators influence food impaction with tight proximal contact. Materials and Methods: Ninety volunteers were recruited for bite force measurement and intraoral scanning. Three‐dimensional surface data and buccal bite data were obtained for 60 impacted and 60 non‐impacted teeth. The scanning data were imported into the Geomagic Studio 2013 to measure three indicators, which included the gap change maximum (Δdm, μm), the buccolingual position of Δdm (P), and the gap expanded buccolingual range (S, mm). The difference between two groups of three indicators and their relationship with food impaction with tight proximal contact were analyzed by the t test, the Pearson chi‐squared test, the nonparametric Mann–Whitney U test, and the binary logistic regression analysis (a = 0.05). Results: All indicators (Δdm, P, and S) were statistically different (p < 0.001, p = 0.002, and p < 0.001) in the impacted and non‐impacted groups. Food impaction with tight proximal contact was affected by Δdm and S (p < 0.001, p = 0.039), but not by P (p = 0.409). Conclusion: The excessive increase of the gap change maximum and the gap expanded buccolingual range under bite force promoted the occurrence of food impaction with tight proximal contact. Clinical Significance: The use of intraoral scanning to measure the characteristics of the proximal contact area gap change under bite force may help to deepen our understanding of the pathogenesis of food impaction with tight proximal contact. Importantly it can provide a reference basis for individualizing and quantifying occlusal adjustment treatment. [ABSTRACT FROM AUTHOR]

Background: A quantitative approach to predict expected muscle activity and mandibular movement from non‐invasive hard tissue assessments remains unexplored. Objectives: This study investigated the predictive potential of normalised muscle activity during various jaw movements combined with temporomandibular joint (TMJ) vibration analyses to predict expected maximum lateral deviation during mouth opening. Method: Sixty‐six participants underwent electrognathography (EGN), surface electromyography (EMG) and joint vibration analyses (JVA). They performed maximum mouth opening, lateral excursion and anterior protrusion as jaw movement activities in a single session. Multiple predictive models were trained from synthetic observations generated from the 66 human observations. Muscle function intensity and activity duration were normalised and a decision support system with branching logic was developed to predict lateral deviation. Performance of the models in predicting temporalis, masseter and digastric muscle activity from hard tissue data was evaluated through root mean squared error (RMSE) and mean absolute error. Results: Temporalis muscle intensity ranged from 0.135 ± 0.056, masseter from 0.111 ± 0.053 and digastric from 0.120 ± 0.051. Muscle activity duration varied with temporalis at 112.23 ± 126.81 ms, masseter at 101.02 ± 121.34 ms and digastric at 168.13 ± 222.82 ms. XGBoost predicted muscle intensity and activity duration and scored an RMSE of 0.03–0.05. Jaw deviations were successfully predicted with a MAE of 0.9 mm. Conclusion: Applying deep learning to EGN, EMG and JVA data can establish a quantifiable relationship between muscles and hard tissue movement within the TMJ complex and can predict jaw deviations. [ABSTRACT FROM AUTHOR]

Background: It remains unclear how the salivary flow and the fat content of food affect bolus formation during mastication. Objectives: We aimed to clarify: (1) how hyposalivation affects jaw‐closing and hyoid‐elevating muscle activities in bolus formation, and (2) if the effect of hyposalivation on muscle activity depends on the fat content of food. Methods: Eighteen healthy male volunteers were instructed to freely ingest four test foods: Plain, Fat without seasoning, Fat with seasoning, and Soft rice crackers. Masseter and suprahyoid electromyographic activities were recorded before and 30 min after the administration of atropine sulfate, a muscarinic receptor antagonist that induces hyposalivation. Results: Hyposalivation extended the masticatory duration significantly in all the test foods except Fat with seasoning. Masticatory cycle time was significantly longer with vs without hyposalivation for the Soft (p =.011). Suprahyoid activity/cycle was significantly greater with vs without hyposalivation (p =.013). Masticatory cycle time was significantly longer at the late stage with vs without hyposalivation for the Soft (p <.001). Suprahyoid activity/cycle was significantly greater at the middle (p =.045) and late stages (p =.002) with vs without hyposalivation for the Soft and greater at the late stage with vs without hyposalivation for the Plain (p =.043). Changes in masticatory cycle time and suprahyoid activity/cycle for these foods had significantly positive relationship (p <.001). Conclusion: Hyposalivation‐induced changes in masticatory behaviours resulted from the middle and late stage suprahyoid activity. Fat content and seasoning compensate for salivary flow inhibition. [ABSTRACT FROM AUTHOR]

Background: The temporal tendon is a structure often compromised in patients suffering from temporomandibular disorders (TMD), yet its intraoral location makes a standardised assessment difficult. Objectives: To evaluate the variability and accuracy to target force of a newly designed intraoral extension for a palpometer device (Palpeter, Sunstar Suisse) when compared to manual palpation, in addition to clinically assessing the mechanical sensitivity and referred sensations of the temporal tendon in healthy individuals. Methods: Experiment 1: 12 individuals were asked to target on a scale 0.5, 1 and 2 kg, for 2 and 5 s by using five different methods (Palpeter, Palpeter with three different extension shapes and manual palpation). Experiment 2: 10 healthy participants were recruited for a randomised double‐blinded assessment by applying pressure of 0.5, 1 and 2 kg to the right temporal tendon with the three extensions and manual palpation. Participants rated the intensity of their sensation/pain on a 0–50–100 numeric rating scale (NRS), unpleasantness on a 0–100 NRS, and if present, they rated and drew the location of referred sensations. Repeated measures analysis of variance (ANOVA) was used in both experiments to compare differences between palpation methods. Tukey's HSD tests were used for the post hoc comparisons, and p values below.05 were considered significant. Results: Experiment 1: The extensions showed no significant differences between them regarding reliability and accuracy for all forces and durations (p >.05). The manual method was significantly less reliable and accurate when compared to the other methods (p <.05). Experiment 2: There were no significant differences between the Palpeter extensions regarding pain intensity or unpleasantness NRS scores (p >.05), but all the extensions had significantly increased pain intensity and unpleasantness when compared to manual palpation (p <.05). Similarly, the frequency of referred sensations was similar between extensions but increased when compared to manual palpation. Conclusions: The new Palpeter extensions proved to be significantly more accurate and have lower test–retest variability than the manual method in a non‐clinical setting. Clinically, they showed no significant differences in NRS scores for pain intensity nor unpleasantness, with no major differences in referred sensations, making any of the extensions suitable for clinical testing of the temporal tendon in future studies. [ABSTRACT FROM AUTHOR]

Background: Class II subdivision is a malocclusion characterized by dental and functional asymmetry that is difficult to manage. Impaired muscle function can result in asymmetrical growth, leading to occlusal instability. Objective(s): The study aimed to assess occlusal force in patients with Class II subdivision malocclusion using Innobyte. Additionally, the discrepancies of force generated at the position of maximum intercuspidation between the left and right sides of the arches were evaluated. Methods: The occlusal force of 66 patients with Class II subdivision malocclusion (group S) was measured and compared with that of 66 patients with Class I (group I) and 66 patients with Class II malocclusion (group II). The S group patients had a Class I molar on the right side and a Class II molar on the left side. ANOVA test, followed by the Games‐Howell post hoc test, was performed to compare the mean of the total force among the groups. To assess the difference in force between the right and left arches, one‐way ANOVA test followed by Tukey's post hoc comparison was performed. Finally, a boxplot was created to show the trend of occlusal force recorded in the three groups of patients. Results: The occlusal force differed significantly among the groups (p <.001). Post hoc Games‐Howell analysis showed significant differences as follows: the total force in group S was 165.24 N greater than in group II and in group I was 218.06 N greater than in group II. The difference (right–left) in total force between the groups was statistically significant (p <.001). Tukey's post hoc test showed following significant correlation: in group S was 53.51 N greater than in group II and 63.12 N greater than in group I. Conclusions: Among the analysed groups, patients with Class II malocclusion exhibited the lowest value of occlusal force. In patients with Class II subdivision malocclusion, force asymmetry, characterised by a higher value on the Class I side and a lower value on the Class II side was observed. [ABSTRACT FROM AUTHOR]

Objective: To assess the efficacy of microcurrent electrical nerve stimulation (MENS) therapy in treating myofascial pain of the masticatory muscles. Methods: In this systematic review and meta-analysis, the efficacy of MENS was evaluated, with the primary outcome being the reduction in pain on palpation of the masticatory muscles. Results: Four independent comparisons based on three studies were included in the meta-analysis (n = 140). In comparison to placebo and other therapies, treatment with MENS showed an improved mean reduction in pain of −0.57 points (CI: −0.91 to −0.23 points, I2 = 83.7%). Conclusion: Evidence from this meta-analysis shows that MENS is an effective non-invasive treatment that can be used to reduce pain in patients with myofascial pain of the masticatory muscle; however, the study was limited by the small number of articles relevant to the research question as well as variability between the selected studies. [ABSTRACT FROM AUTHOR]

Background and Objectives: The aim was to compare the activity of the masseter muscles in children with different types of breathing. Materials and Methods: A cross-sectional study was conducted including patients aged 6–12 years with mixed dentition, who came for oral care at the Master's Degree in Pediatric Dentistry program at the Complutense University of Madrid (UCM), according to inclusion and exclusion criteria. The sample was divided into three groups: nasal breathers without dental alterations (control group), oral breathers with dental malocclusion, and oral breathers with previous orthodontic treatment. An electromyography was performed, and statistic methods were conducted with a 95% confidence to contrast hypothesis. Results: A total of 122 children were analyzed and distributed into three groups. The electrical muscle activity of masseters was significantly different between the study groups (p < 0.001 for all comparisons). Pairwise comparisons revealed a significantly higher electrical muscle activity in the control group (nasal breathers) during chewing compared to both groups of oral breathers (p < 0.001 for both comparisons). Orthodontic treatment decreased electrical muscle activity during isometric contraction in oral breathers compared to nasal breathers (p < 0.001), but did not significantly affect electrical muscle activity during chewing. Higher decompensation values were obtained in oral breathers without previous orthodontic treatment compared the other study groups (p < 0.001 for both comparisons), although electrical muscle activity values were similar in both groups of oral breathers (p > 0.05 for both comparisons). Conclusions: Differences in electrical muscle activity between nasal and oral breathers can be confirmed. Oral breathers with and without orthodontic treatment showed lower electrical muscle activity of masseters during chewing than nasal breathers, while at isometric contraction, only oral breathers with previous orthodontic treatment showed lower electrical activity. Higher decompensation values were found in oral breathers without previous orthodontic treatment, in comparison to the control group and oral breathers with previous orthodontic treatment. [ABSTRACT FROM AUTHOR]

Abstract Objectives The Functional Clear Aligner (FCA) is a novel orthodontic appliance designed for the treatment of Class II malocclusion with mandibular retrognathia in adolescents. The aim of this study was to investigate the biomechanical characteristics of the masticatory muscles, jawbone, and temporomandibular joint (TMJ) during mandibular advancement using either FCA or Class II elastics combined with clear aligner (Class II elastics) through finite element analysis. Materials and methods A 3D finite element model of the ‘muscle-jawbone-TMJ-appliance’ system was constructed based on CBCT and MRI images of a boy with skeletal Class II malocclusion. Masticatory muscles included masseter, temporal, medial pterygoid, and lateral pterygoid muscles. The TMJ consists of the temporal bone’s glenoid fossa, disc, and mandibular condyle. To observe the biomechanical characteristics of the muscles and TMJ during orthodontic appliance wearing and the retention phase, two different protocols were used: Model 1: The mandibular advancement using FCA; Model 2: The mandibular advancement using Class II elastics. Results The FCA group produced greater and more coordinated masticatory muscle forces compared to the Class II elastics group. Temporal and masseter muscles exhibited the most pronounced variation in muscle strength during mandibular advancement. The FCA group exhibited greater TMJ region stress compared to the Class II elastics group. Interestingly, the stress on the articular discs in both models decreased over time. Tensile stresses were observed in both the condyle and the posterior region of the articular fossa. Conclusion During skeletal Class II malocclusion treatment, masticatory muscle forces and stress on the TMJ were higher in the FCA group compared to the Class II elastics group. In both models, stress cushioning was provided by the articular disc.

Abstract Background The anatomic characteristics of the masticatory muscles differ across craniofacial skeletal patterns. Objective To identify differences in the anatomic characteristics of masticatory muscles across different sagittal and vertical craniofacial skeletal patterns. Eligibility criteria Studies measuring the thickness, width, cross-sectional area (CSA), volume and orientation of masticatory muscles in healthy patients of different sagittal (Class I, Class II, and Class III) and/or vertical (normodivergent, hypodivergent, and hyperdivergent) patterns. Information sources Unrestricted literature searches in 8 electronic databases/registers until December 2023. Risk of bias and synthesis of results Study selection, data extraction, and risk of bias assessment with a customised tool were performed independently in duplicate. Random-effects meta-analysis and assessment of the certainty of clinical recommendations with the GRADE approach were conducted. Results 34 studies (37 publications) were selected with a total of 2047 participants and data from 16 studies were pulled in the meta-analysis. Masseter muscle thickness in relaxation was significantly greater by 1.14 mm (95% CI 0.74–1.53 mm) in hypodivergent compared to normodivergent patients while it was significantly decreased in hyperdivergent patients by − 1.14 mm (95% CI − 1.56 to − 0.73 mm) and − 2.28 mm (95% CI − 2.71 to − 1.85 mm) compared to normodivergent and hypodivergent patients respectively. Similar significant differences were seen between these groups in masseter muscle thickness during contraction as well as masseter muscle CSA and volume. Meta-analyses could not be performed for sagittal categorizations due to insufficient number of studies. Conclusions Considerable differences in masseter muscle thickness, CSA and volume were found across vertical skeletal configurations being significantly reduced in hyperdivergent patients; however, results should be interpreted with caution due to the high risk of bias of the included studies. These variations in the anatomic characteristics of masticatory muscles among different craniofacial patterns could be part of the orthodontic diagnosis and treatment planning process. Registration: PROSPERO CRD42022371187 .

Purpose: To evaluate oral health-related quality of life in patients with temporomandibular disorders (TMDs; masticatory muscle pain, disc displacement with reduction, or both) and to determine the possible associations of these disorders with anxiety.Materials and Methods: This study consisted of 150 patients with TMDs and 50 healthy controls. The patients were diagnosed and then divided into three diagnostic groups according to the Diagnostic Criteria for Temporomandibular Disorders Axis I: masticatory muscle pain (group MP), disc displacement with reduction (group DD), or both (group MPDD). All participants completed the Oral Health Impact Profile-14 (OHIP-14) and Generalized Anxiety Disorder-7 (GAD-7) questionnaires for oral health-related quality of life and anxiety assessment, respectively. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U post hoc paired comparison tests.Results: A total of 121 patients (60.25%) were women, and 79 (39.75%) were men, with ages ranging from 18 to 68 years (mean age: 37.32 ± 13.62). Gender distribution, mean age, and educational and occupational status were similar among groups. The OHIP-14 global and domain scores and the distribution of GAD-7 levels were significantly different among the groups (P < .001). For the psychologic discomfort and disability domains, group MPDD statistically scored the highest, followed by groups MP and DD and the healthy control group (P < .05). Correlation analyses showed that, within group MPDD, there were positive correlations between the GAD-7 and all OHIP-14 scores (r = 0.438, P < .001).Conclusion: Oral health-related quality of life is negatively affected by TMDs, and OHRQoL seems to decrease as the severity of anxiety increases. Therefore, physical conditions and anxiety of the TMD patients should be simultaneously considered for treatment and maintenance. [ABSTRACT FROM AUTHOR]

Purpose: To compare subjects' sensory responses to horizontal and vertical forces on tooth- and implant-supported restorations. Materials and Methods: In this prospective study, three protocols simulating the horizontal or vertical forces that occur during mastication were used to obtain subjective responses from subjects. These protocols included the measurement of horizontal force intensity during excursive movements and the identification of initial contact during guided and free vertical closure. Responses were recorded using a 1- to 10-point visual analog scale (VAS) and/or monitored with electromyography (EMG) and Tekscan. Results: The study included 30 patients with a single implantsupported restoration (ISR) with a contralateral tooth-supported restoration (TSR). For horizontal forces similar to those of mastication (0.6 N), subject VAS scores were similar for both ISRs and TSRs at 6.3 vs 6.1, respectively. At reduced forces (0.2 and 0.4 N), subject responses were greater for the TSR at 3.4 and 5.4, respectively, as opposed to 1.2 and 2.6 for ISR, respectively (P < .01). During vertical guided closure (Test 1) at 25% of maximum bite force (MBF), subjects were more successful at correctly identifying initial contact of TSRs at a rate of 12 out of 17, compared to ISRs, which achieved a rate of 4 out of 13 (P < .1). In vertical free closure (Test 2), subject responses for the correct identification of initial contact at 50% MBF were similar for both TSRs and ISRs at 13 out of 17 and 9 out of 13, respectively. However, comparing the correct responses for subjects whose initial contacts were ISR showed a significant improvement in correct answers from Test 1 to Test 2, from 4 out of 13 correct to 9 out of 13 correct (P < .05). Conclusion: While the mechanism is not clear, subjects' ability to discern the horizontal and vertical forces at levels comparable to mastication appear similar between TSRs and ISRs. [ABSTRACT FROM AUTHOR]

At the present stage of diagnostics and treatment of dental diseases, morphofunctional disorders of the dento-maxillary system associated with a decrease in the height of occlusion are becoming more common. In the scientific literature, this pathological condition is described under the name "occlusion" that decreases. The reasons that cause it include partial or complete loss of teeth, irrational prosthetics and untimely restoration of dentition defects, doctors' mistakes in the restructuring of the masticatory apparatus, and a generalized form of pathological abrasion of hard tooth tissues. The purpose of the study – demonstration of a clinical case of pathological abrasion of hard tissues of teeth with a decrease in bite height, complicated by defects in the dentition. Patient S., 47 years old, applied for orthopedic help with complaints of anatomical deformity, significant abration of teeth on the upper and lower jaws, increased sensitivity to various types of irritants, partial absence of teeth, impaired masticatory function, periodic clicking in the temporomandibular joint, aesthetic and phonetic defects. Based on the data obtained, we established the following diagnosis: generalized form of pathological abrasion of hard teeth tissues, subcompensated form of reduced bite height, complicated by defects in the dentition of the upper jaw – class I according to the Kenedy classification, lower jaw – class III according to the Kenedy classification. The loss of chewing efficiency according to Agapov was 68%. Patient S. was recommended a two-stage orthopedic treatment, which involves preliminary separation of the bite with the help of individual vinyl mouth guards which have an increasing thickness of 2, 4 and 6 mm, made for the lower jaw.The planned treatment period with each of the muscle relaxant splints will be 2 months. Subsequently, 15, 14, 13, 12, 11, 21, 22, 23, 24 will be restored with one-piece metal crowns with ceramic cladding, and the final defects in the lateral areas will be restored with a clasp prosthesis with a locking system of fixation. The included defect of the lateral part of the lower jaw is planned to be restored with a metal-ceramic bridge-like prosthesis with a support on 47, 45, 44, and the worn-out hard tooth tissues will be completely restored with photopolymer material. In patients with a reduction in bite height of more than 2 mm, it is advisable to carry out treatment in two stages. At the first stage, we normalize the occlusal height and rebuild the function of the masticatory muscles. At the second stage, we provide rational prosthetics. Orthopedic rehabilitation with myorelaxing splints of increasing thickness makes it possible to correctly rebuild myostatic reflexes and prevent functional disorders in the TMJ. Any case of complex treatment of patients with a decrease in bite height due to pathological abrasion of the hard tooth tissues deserves the attention of both scientists and dentists in practical health care.

Myogenous temporomandibular disorder (M-TMD) is one of the main subtypes of temporomandibular disorder (TMD) and typically manifests as masticatory myofascial pain; the incidence of TMD has been increasing annually in recent years. Botulinum toxin type A (BTX-A) is a potent neurotoxin produced by Clostridium botulinum. BTX-A inhibits the release of acetylcholine from the presynaptic membrane, thereby blocking neuromuscular junction signaling. The noncosmetic application of BTX-A in the oral and maxillofacial regions is a prominent research topic. In recent years, an increasing number of studies have focused on the application of BTX-A in the treatment of M-TMD. The results of a literature review revealed that an appropriate dose (10-50 U unilaterally) of BTX-A administered in a single injection into the masticatory muscles can effectively treat myalgia over a period of 3-6 months. Common adverse effects, such as masticatory weakness and facial paralysis, are transient and can be avoided by standardized injection techniques. However, there is a lack of standardized guidelines for injection techniques in clinical practice.

Background Objective Methods Results Conclusion Masticatory muscle training by chewing gum can be performed easily and improve masticatory muscle function and strength. However, increased masticatory muscle activity and function may alter the mandibular shape.We aimed to investigate the effects of gum chewing training on the occlusal force, masseter muscle thickness (MMT) and mandibular shape in healthy adults.We conducted a prospective randomised controlled trial from January 2020 to September 2020 at the Yonsei University College of Dentistry. Fifty‐eight participants were randomly assigned to the training and control groups. The training group chewed gum three times a day for 6 months, while the control group received no training. Changes in the maximum occlusal force and MMT were evaluated at baseline and after 1, 3 and 6 months. Changes in the mandibular shape were evaluated at baseline and after 6 months.The mean maximum occlusal force of the training group at 3 months was significantly higher than that at baseline, which was also significantly different from that in the control group (p < .001). As the maximum occlusal force increased, the occlusal contact area also increased (p = .020). There was no statistically significant difference in MMT or mandibular shape compared to the baseline.Mastication training using gum increases maximum occlusal force due to an increase in occlusal contact area but has no effect on MMT or mandibular shape. [ABSTRACT FROM AUTHOR]

Background: The screw-in effect is a tendency of a nickel-titanium (NiTi) rotary endodontic file to be pulled into the canal, which can result in a sudden increase in stress leading to instrument fracture, and over-instrumentation beyond the apex. To reduce screw-in force, repeated up-and-down movements are recommended to distribute flexural stress during instrumentation, especially in curved and constricted canals. However, there is no consensus on the optimal number of repetitions. Therefore, this study aimed to examine how repeated up-and-down movements at the working length affect torque/force generation, surface defects, and canal shaping ability of JIZAI and TruNatomy instruments. Methods: An original automated root canal instrumentation device was used to prepare canals and to record torque/force changes. The mesial roots of human mandibular molars with approximately 30˚ of canal curvature were selected through geometric matching using micro-computed tomography. The samples were divided into three groups according to the number of up-and-down movements at the working length (1, 3, and 6 times; n = 24 each) and subdivided according to the instruments: JIZAI (#13/0.04 taper, #25/0.04 taper, and #35/0.04 taper) or TruNatomy (#17/0.02 taper, #26/0.04 taper, and #36/0.03 tape) (n = 12 each). The design, surface defects, phase transformation temperatures, nickel-titanium ratios, torque, force, shaping ability, and surface deformation were evaluated. Data were analyzed with the Kruskal-Wallis and Dunn's tests (α = 0.05). Results: The instruments had different designs and phase transformation temperatures. The 3 and 6 up-and-down movements resulted in a smaller upward force compared to 1 movement (p < 0.05). TruNatomy generated significantly less maximum torque, force, and surface wear than JIZAI (p < 0.05). However, TruNatomy exhibited a larger canal deviation (p < 0.05). No statistical differences in shaping ability were detected between different up-and-down movements. Conclusions: Under laboratory conditions with JIZAI and TruNatomy, a single up-and-down movement at the working length increased the screw-in force of subsequent instruments in severely curved canals in the single-length instrumentation technique. A single up-and-down movement generated more surface defects on the file when using JIZAI. TruNatomy resulted in less stress generation during instrumentation, while JIZAI better maintained the curvature of root canals. [ABSTRACT FROM AUTHOR]

Diagnosis of bruxism is challenging because not all contractions of the masticatory muscles can be classified as bruxism. Conventional methods for sleep bruxism detection vary in effectiveness. Some provide objective data through EMG, ECG, or EEG; others, such as dental implants, are less accessible for daily practice. These methods have targeted the masseter as the key muscle for bruxism detection. However, it is important to consider that the temporalis muscle is also active during bruxism among masticatory muscles. Moreover, studies have predominantly examined sleep bruxism in the supine position, but other anatomical positions are also associated with sleep. In this research, we have collected EMG data to detect the maximum voluntary contraction of the temporalis and masseter muscles in three primary anatomical positions associated with sleep, i.e., supine and left and right lateral recumbent positions. A total of 10 time domain features were extracted, and six machine learning classifiers were compared, with random forest outperforming others. The models achieved better accuracies in the detection of sleep bruxism with the temporalis muscle. An accuracy of 93.33% was specifically found for the left lateral recumbent position among the specified anatomical positions. These results indicate a promising direction of machine learning in clinical applications, facilitating enhanced diagnosis and management of sleep bruxism. [ABSTRACT FROM AUTHOR]

Summary The objective of the current study was to evaluate the clinical utility of bruxism episode index in predicting the level of masticatory muscle pain intensity. The study involved adults (n = 220) recruited from the Outpatient Clinic of Temporomandibular Disorders at the Department of Experimental Dentistry, Wroclaw Medical University, during the period 2017–2022. Participants underwent medical interview and dental examination, focusing on signs and symptoms of sleep bruxism. The intensity of masticatory muscle pain was gauged using the Numeric Rating Scale. Patients identified with probable sleep bruxism underwent further evaluation through video‐polysomnography. Statistical analyses included the Shapiro–Wilk test, Spearman's rank correlation test, association rules, receiver operating characteristic curves, linear regression, multivariate regression and prediction accuracy analyses. The analysis of correlation and one‐factor linear regression revealed no statistically significant relationships between bruxism episode index and Numeric Rating Scale (p > 0.05 for all analyses). Examination of receiver operating characteristic curves and prediction accuracy indicated a lack of predictive utility for bruxism episode index in relation to masticatory muscle pain intensity. Multivariate regression analysis demonstrated no discernible relationship between bruxism episode index and Numeric Rating Scale across all examined masticatory muscles. In conclusion, bruxism episode index and masticatory muscle pain intensity exhibit no correlation, and bruxism episode index lacks predictive value for masticatory muscle pain. Clinicians are advised to refrain from employing the frequency of masticatory muscle activity as a method for assessing the association between masticatory muscle pain and sleep bruxism. [ABSTRACT FROM AUTHOR]

Purpose: The potential relationship between mastication ability and cognitive function in idiopathic normal pressure hydrocephalus (iNPH) patients is unclear. This report investigated the association between mastication and cognitive function in iNPH patients using the gray level of the co-occurrence matrix on the lateral pterygoid muscle. Methods: We analyzed data from 96 unoperated iNPH patients who underwent magnetic resonance imaging (MRI) between December 2016 and February 2023. Radiomic features were extracted from T2 MRI scans of the lateral pterygoid muscle, and muscle texture parameters were correlated with the iNPH grading scale. Subgroup analysis compared the texture parameters of patients with normal cognitive function with those of patients with cognitive impairment. Results: The mini-mental state examination score correlated positively with the angular second moment (P < 0.05) and negatively with entropy (P < 0.05). The dementia scale (Eide's classification) correlated negatively with gray values (P < 0.05). Gray values were higher in the cognitive impairment group (64.7 ± 16.6) when compared with the non-cognitive impairment group (57.4 ± 13.3) (P = 0.005). Entropy was higher in the cognitive impairment group (8.2 ± 0.3) than in the non-cognitive impairment group (8.0 ± 0.3) (P < 0.001). The area under the receiver operating characteristic curve was 0.681 (P = 0.003) and 0.701 (P < 0.001) for gray value and entropy, respectively. Conclusion: Our findings suggest an association between heterogeneity of mastication and impaired cognitive function in iNPH patients and highlight muscle texture analysis as a potential tool for predicting cognitive impairment in these patients. [ABSTRACT FROM AUTHOR]

Summary: Rhythmic masticatory muscle activity (RMMA) is a periodic muscle activity that characterises sleep bruxism (SB) events. These can occur as a single event, in pairs, or in clusters. Since RMMA episodes often occur in clusters and the relevance of this occurrence is unknown, we conducted a study to investigate the effect of RMMA clusters on sleep fragmentation and the severity of orofacial muscle pain. This study involved a secondary analysis using data from 184 adult subjects with orofacial muscle pain who underwent definitive polysomnography (PSG) for sleep bruxism diagnosis. Self‐reported orofacial muscle pain (OFMP) was assessed using the numeric rating scale, and additional evaluation of side‐to‐side equivalence (symmetry) was described using a binary system. Among the 184 participants, 60.8% (n = 112) did not exhibit clusters and among the 72 participants with clusters, 36.1% (n = 26) and 63.9% (n = 46) were in the high and low RMMA frequency groups, respectively. The high SB group had significantly three times more phasic RMMA events than the noncluster group. A total of 89.67% (n = 165) of subjects reported orofacial muscle pain. While there was no difference in the severity of OFMP among groups, a significant decrease in symmetry between the severity of temporal muscle pain on the left and right sides was noted in the cluster group compared with the noncluster group. Clustering of RMMA events is associated with sleep fragmentation. The asymmetry of temporal muscle pain is related to the presence of RMMA clusters in sleep bruxism. [ABSTRACT FROM AUTHOR]