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.

BACKGROUND: Oral food processing is an important part of daily food intake. A major part of this process is mastication, which prepares a bolus of food for swallowing by mechanically crushing and grinding ingested food between the teeth using rhythmic movements. Masticatory dysfunction is common in the elderly and in some neurological disorders and can have serious negative health consequences.
OBJECTIVE: This study investigated the effect of restricted mastication, achieved by experimentally reducing the duration of mastication, on masticatory patterns and subsequent swallowing function.
METHODS: Thirty healthy men (25 ± 3 years old) were instructed to chew gum jelly with a free mastication duration (G100), a half and a quarter duration of G100. Masseter and digastric electromyographic (EMG) activity was recorded to assess mastication and swallowing activity, respectively. In addition, the acceleration of the thyroid cartilage ridge was measured with an accelerometer. The root mean square (RMS) of muscle EMG activity in the masseter and digastric muscles, the number of masseter EMG bursts, time to peak and total duration of each masseter EMG burst, swallowing duration and laryngeal elevation latency were analysed.
RESULTS: Restricting masticatory duration reduced the number of mastication cycles (p < .001), prolonged the time to peak (p < .001) and total duration of masseter EMG bursts (p < .001) and resulted in an overall increased RMS score of masseter muscle activity (p = .017). Furthermore, restricted masticatory duration led to a decrease in both swallowing duration (p = .001) and laryngeal elevation latency (p = .012), with a significant increase in the RMS score of digastric muscle activity (p < .001).
CONCLUSIONS: Under the experimental conditions of restricted mastication, several adaptation features were observed, including changes in masticatory cycle characteristics and swallowing duration. Thus, although the overall masticatory efficiency was reduced, these adaptations allowed healthy individuals to still swallow safely.

UNASSIGNED: This study aimed to compare the perceived masticatory ability (PrMA) in completely edentulous patients (EDPs) with thermoplastic conventional complete dentures (CDs) versus single implant-retained mandibular overdentures.
UNASSIGNED: The current study was conducted in the outpatient Prosthodontic Clinic, Faculty of Dental Medicine, Al-Azhar University, Cairo, Egypt. PrMA was evaluated in 45 completely edentulous patients (46% males, mean age 50.4 ± 4.7 years). Each patient received a thermoplastic PMMA complete denture (Polyan IC TM Bredent GmbH & Co.KG, Germany). The PrMA was evaluated at one-month and six-month intervals of denture use. An immediate loading single implant was placed into the mid-symphyseal for each patient, and the denture was adjusted. Subsequently, the PrMA was reevaluated after one month and six months. The data were collected and statistically analyzed using the SPSS@V25 to assess the changes in PrMA.
UNASSIGNED: The PrMA demonstrated improvement after six months of thermoplastic conventional denture use. However, this improvement was not statistically significant (p = 0.405). In addition, the PrMA showed a substantial increase following a single implant placement at one and six months (p < 0.001) of the overdenture use compared to the conventional denture. The PrMA insignificantly improved (p = 0.397) after six months of the single implant retained overdenture use.
UNASSIGNED: The study\'s findings indicate that using immediate loading single implant-retained mandibular overdentures significantly improved PrMA in completely edentulous patients.

BACKGROUND: Craniosynostosis (CS), premature fusion of one or more cranial sutures, leads to abnormal skull development, impacting both facial esthetics and oral function. This study aimed to evaluate the specific orofacial and oral health characteristics, including masticatory performance, in Thai patients with CS.
METHODS: A comparative study was conducted with Thai CS patients aged 6-17 years and a control group of healthy individuals with similar age distribution. Assessments included craniofacial morphology, oral health status, and masticatory performance. Intergroup comparisons utilized appropriate statistical tests.
RESULTS: The study included 24 CS patients with a mean age of 10.11 ± 2.98 years and 30 controls. CS patients exhibited a significantly higher prevalence of various oral conditions compared to controls: cleft palate (20.8%), anterior open bite (41.7%), anterior crossbite (54.2%), posterior crossbite (50%), combined anterior-posterior crossbite (45.8%), dental crowding in both maxilla and mandible (50% and 45.8% respectively), congenitally missing teeth (50%), supernumerary teeth (12.5%), and eruption failure (54.2%). Furthermore, CS patients exhibited significantly higher caries prevalence and susceptibility, alongside poorer oral hygiene, compared to controls. Regarding jaw relationships, CS patients exhibited a significantly higher proportion of Angle\'s Class III malocclusion (50%) compared to the control group, where Class I malocclusion was predominant (50%). Masticatory performance, assessed using the two-color gum mixing ability test, showed significantly higher hue variance in CS patients (0.12 ± 0.07) compared to the control group, indicating reduced chewing performance.
CONCLUSIONS: This study underscores the significant orofacial and oral health challenges faced by children with CS, including a high prevalence of malocclusions, dental anomalies, elevated caries experience, and compromised masticatory function. These findings emphasize the importance of tailored interventions and comprehensive oral healthcare strategies to address the unique needs of this population and improve their overall quality of life.

BACKGROUND Measurement of bite force plays a crucial role in assessment of the masticatory system. With a growing interest in detecting occlusal irregularities, bite force sensors have garnered attention in the biomedical field. This study aimed to introduce a hydrogel bite force sensor, based on hydroxyethyl-cellulose-fructose-water (HEC-F-water), for premolar and molar teeth, and to evaluate it using optical profilometry, infrared spectroscopy (FTIR), and Instron Tension testing system, with 2.5 cm (1 inch) margins at top, bottom, right, and left. MATERIAL AND METHODS We fabricated 20 HEC-F-water hydrogel samples sized with surface of 1×1 cm, with 2 different widths - 1 mm and 5 mm. The samples were characterized using optical profilometry and FTIR and their electrical characteristics were determined using an impedance analyzer. Aluminum (Al) electrodes, fabricated using Cutting Plotter, were used to form a HEC-F-water-based transducer, which was used for bite force sensing. The Instron tensile testing system was employed, utilizing 3D printed models of the upper and lower jaw, to simulate biting. Forces in the range between 40 N and 540 N were exerted upon the transducer, and the output change in the electrical signal was measured. RESULTS The study determined the transfer function between bite force and capacitance. The fabricated sensor exhibited a sensitivity of 3.98 pF/N, an input range of 500 N, output range of 2 nF, and accuracy of 95.9%. CONCLUSIONS This study introduces an edible bite force sensor employing an edible hydrogel as a dielectric, presenting a novel avenue in the development of edible sensorics in dentistry.

Consumer preferences for walnut products are largely determined by the flavors released during mastication. In this study, a peeled walnut kernel (PWK) model was established with oral parameters decoupled using a Hutchings 3D model. The model explored in vitro variations using head-space solid-phase microextraction-gas chromatography-mass spectrometry and intelligent sensory techniques. The fracture strength, hardness, particle size, adhesiveness, springiness, gumminess, and chewiness were significantly reduced during mastication. We identified 61 volatile compounds and found that 2,5-dimethyl-3-ethylpyrazine is a key component, releasing predominantly baking and milky notes. Glutamic acid, alanine, arginine, and sucrose were identified as the key compounds in taste perception. The method can help establish a mastication model for nuts and facilitate breakthroughs in the development of walnut products and processing methods.

Food bolus is the major outcome of oral processing of foods. Its structure and properties are crucial for safe swallowing and subsequent gastric digestion. However, collecting the ready-to-swallow bolus for further analysis in either normal or deficient human subjects is difficult, regulatorily or practically. Here, a novel in vitro bio-inspired oral mastication simulator (iBOMS-Ⅲ) was developed to be capable of replicating food boluses comparable to those in vivo. Cooked rice and roasted peanuts were used as the model foods (soft and hard) respectively. Particle size distribution, moisture content and rheology of the food boluses produced in the iBOMS-Ⅲ were assessed. A conventional food blender was also employed as a non-consequential comparation. Eighteen healthy young volunteers of the ages from 20-30 years (10 male and 8 female) were invited to provide the in vivo data. For cooked rice boluses produced by the iBOMS-Ⅲ with 10, 12, 14, and 20 chewing number of cycles, the moisture content exhibited minimal variation (68.3-68.8 wt%), aligning closely with values obtained from the average value of the human subjects (67.5 wt%). Similarly, the boluses from roasted peanut displayed similar moisture contents across masticatory number of cycles (36, 40, and 44 number of cycles), averaging at 35.3 %, mirroring the average in vivo results (33.8 wt%). Furthermore, the shear viscosity of both cooked rice and roasted peanut boluses exhibited minimal variations with iBOMS-Ⅲ chewing number of cycles. The particle size distributions of the boluses produced with 14 and 44 chewing number of cycles matched well with the in vivo data for cooked rice and roasted peanuts, with median particle size (d50) being 1.07 and 0.78 mm, respectively. The physical properties of the food boluses collected from the food blender, with varying grinding times, differed significantly. This study demonstrates the value of the iBOMS-Ⅲ in achieving realistic boluses with two very different food textures.

BACKGROUND: The use of clear aligners is becoming more common for aesthetic orthodontic treatment, but there are still concerns about how they affect mastication biomechanics in the short and long term. The clear aligners treatment (CAT) mechanism changes the position of the mandible and maxilla, especially impacting the masseter muscle. Surface electromyography (sEMG) proves to be a useful method to evaluate masticatory muscle activity (MMA).
OBJECTIVE: To analyze the effect of clear aligners treatment on alterations in masticatory muscles (masseter, temporalis) using surface electromyography.
METHODS: Five databases (PubMed, Web of Science, SCOPUS, Cochrane Library, and Google Scholar) were searched up to March 2024.
METHODS: Studies in which MMA was evaluated after the installation of orthodontic clear aligners.
METHODS: Screening, data extraction, and quality assessments were performed by four investigators independently. The data, which evaluated temporalis and masseter muscle characteristics during CAT using surface electromyography, was extracted, and the quality of the studies was evaluated. The risk of bias was assessed using the Newcastle-Ottawa Scale (NOS).
RESULTS: Six studies (two prospective cohort studies, three observational longitudinal studies, and one observational longitudinal case-control study) with low and moderate risk of bias were included in the qualitative synthesis. Six of these were also included in the meta-analysis. Our study investigated the dynamics of masseter and temporalis muscle activity during CAT. The results show that during maximal voluntary clenching, the masseter muscle demonstrated a significant initial increase (P < .05) followed by a subsequent non-significant decrease. It also showed that submaximal voluntary clenching consistently exhibited a significant reduction in muscle activity throughout the study period (P < .01). Assessment of muscle activity at the mandibular resting position revealed a variety of responses, with some participants showing a significant increase while others exhibited non-significant changes (P < .05, P > .05, respectively). However, the meta-analysis showed a non-significant difference in measuring masseter and temporalis muscles activity during CAT.
CONCLUSIONS: Based on existing evidence, it is reasonable to conclude that CAT affected MMA. During maximal voluntary clenching, masseter muscle activity initially increased but later decreased, while temporalis muscle activity showed mixed results. Submaximal voluntary clenching revealed a consistent decrease in muscle activity over time. Mandibular resting position assessments showed both increases and no significant changes in muscle activity. However, the existing literature is insufficient to draw concrete conclusions; therefore, well-conducted further research is needed to confirm this statement.
BACKGROUND: This systematic review and meta-analysis were registered in the International Prospective Register of Systematic Reviews (PROSPERO CRD42024522231).

BACKGROUND: Current anatomical knowledge of the origin of the bucinator muscle (BM), i.e., long thin attachments on the maxilla and mandible and the pterygomandibular raphe (PMR), is not supported by anatomical dissection of this muscle. The aim of this study was therefore to investigate the detailed morphology of the BM and associated structures and to discuss its function.
METHODS: The anatomy of the BM and related structures was investigated in 15 cadaveric heads using a surgical microscope and histological analysis.
RESULTS: The inferior fibers of the BM originated from a small retromolar area (internal oblique line), which shared a common tendon with the deep tendon of the temporalis. The superior fibers of the BM originated from the maxillary tuberosity. The middle fibers originated the pterygoid hamulus. No PMR was identified in any of the specimens, but the border between the BM and superior pharyngeal constrictor muscle (SC) was clear because the muscle fibers followed different directions. Some horizontal fibers were continuous between the BM and SC.
CONCLUSIONS: Our results suggest the need to revise established accounts of the origins of the bucinator (the maxillary tuberosity, conjoint tendon of the temporalis, and pterygoid hamulus without a pterygomandibular raphe. It also needs to be noted that some of its fibers merge directly with the SC.

It is presumed that the unusual central location of mesencephalic trigeminal neurons is a specialization that allows them to receive synaptic input. However, relatively few synaptic terminals were observed on the somata of mesencephalic trigeminal neurons in macaque monkeys via electron microscopy. This leaves the question of dendritic synaptic terminals open. Unlike the pseudounipolar neurons found in the trigeminal ganglion, some mesencephalic trigeminal neurons have been reported to be multipolar cells exhibiting a number of dendritic processes in non-primate species. To examine whether this morphological feature was also present in macaque monkeys, we retrogradely filled these cells with biotinylated dextran amine by injecting it into the trigeminal nerve entry zone. A portion of the mesencephalic trigeminal neurons exhibited short, poorly branched, dendritic processes. They also exhibited very fine, short processes believed to be somatic spines. Thus, primate trigeminal mesencephalic neurons appear to have specializations aimed at increasing the membrane surface area available for synaptic input.