Radiographic review of anatomy and pathology of the masticator space: what the emergency radiologist needs to know.

The differential diagnosis of a masticator space (MS) lesion is broad, owing in part to the multiple structures contained within such a small region. It is also because the MS is adjacent to many of the other deep spaces within the head and neck, which can act as gateways for disease spread. Therefore, emergency radiologists must be familiar with anatomy of the MS, as well as adjacent spaces in order to provide an accurate diagnosis to the referring clinician. This article illustrates the anatomy and common pathologies within the MS using a case-based multimodality approach. Common masticator space pathologies can be categorized into inflammatory/infectious, neoplastic, and vasoformative lesions. Important imaging features of MS lesions and patterns of disease spread will be discussed, with the aim of making this complex deep space more approachable in the emergent setting.

Anatomical, functional, physiological and behavioural aspects of the development of mastication in early childhood.

Mastication efficiency is defined as the efficiency of crushing food between the teeth and manipulating the resulting particles to form a swallowable food bolus. It is dependent on the orofacial anatomical features of the subject, the coordination of these anatomical features and the consistency of the food used during testing. Different measures have been used to indirectly quantify mastication efficiency as a function of children's age such as observations, food bolus characterisation, muscle activity measurement and jaw movement tracking. In the present review, we aim to describe the changes in the oral physiology (e.g. bone and muscle structure, teeth and soft tissues) of children and how these changes are associated with mastication abilities. We also review previous work on the effect of food consistency on children's mastication abilities and on their level of texture acceptance. The lack of reference foods and differences in testing methodologies across different studies do not allow us to draw conclusions about (1) the age at which mastication efficiency reaches maturity and (2) the effect of food consistency on the establishment of mature mastication efficiency. The effect of food consistency on the development of children's mastication efficiency has not been tested widely. However, both human and animal studies have reported the effect of food consistency on orofacial development, suggesting that a diet with harder textures enhances bone and muscle growth, which could indirectly lead to better mastication efficiency. Finally, it was also reported that (1) children are more likely to accept textures that they are able to manipulate and (2) early exposure to a range of textures facilitates the acceptance of foods of various textures later on. Recommending products well adapted to children's mastication during weaning could facilitate their acceptance of new textures and support the development of healthy eating habits.

Global human mandibular variation reflects differences in agricultural and hunter-gatherer subsistence strategies.

Variation in the masticatory behavior of hunter-gatherer and agricultural populations is hypothesized to be one of the major forces affecting the form of the human mandible. However, this has yet to be analyzed at a global level. Here, the relationship between global mandibular shape variation and subsistence economy is tested, while controlling for the potentially confounding effects of shared population history, geography, and climate. The results demonstrate that the mandible, in contrast to the cranium, significantly reflects subsistence strategy rather than neutral genetic patterns, with hunter-gatherers having consistently longer and narrower mandibles than agriculturalists. These results support notions that a decrease in masticatory stress among agriculturalists causes the mandible to grow and develop differently. This developmental argument also explains why there is often a mismatch between the size of the lower face and the dentition, which, in turn, leads to increased prevalence of dental crowding and malocclusions in modern postindustrial populations. Therefore, these results have important implications for our understanding of human masticatory adaptation.

Dental anatomy and pathology encountered on routine CT of the head and neck.

OBJECTIVE: Although dental CT is not routinely performed at hospital imaging centers, dental and periodontal disease can be recognized on standard high-resolution CT of the neck and face. These findings can have significant implications with regard to not only dental disease, but also diseases of the sinuses, jaw, and surrounding soft tissues. This article serves to review dental and periodontal anatomy and pathology as well as other regional entities with dental involvement and to discuss the imaging findings. CONCLUSION: Recognition of dental and periodontal disease has the potential to affect management and preclude further complications, thereby preserving the smile, one of the most recognizable and attractive features of the human face and, unfortunately, often disease ridden. Although practicing good oral hygiene and visiting the dentist for regular examinations and cleanings are the most effective ways to prevent disease, some patients do not take these preventative measures. Thus, radiologists play a role in diagnosing dental disease and complications such as chronic periodontitis and abscesses, nonhealing fractures and osteomyelitis, oroantral fistulas, tumoral diseases, osteonecrosis of the jaw, and other conditions.

Coordination of the stomatognathic and postural system activities and their functional status.

Analysis of correlations of the functional parameters of the stomatognathic and postural systems with sub-, decompensated, and compensated status was carried out. Disorders in the masticatory muscle activity and interactions between the postural and stomatognathic systems were detected in patients with sub- and decompensated functional status. A significant correlation between the studied functional parameters was detected in the patients with the compensated functional status.

Larval morphology of Metaphycus flavus and its role in host attachment and larval cannibalism.

Metaphycus flavus (Howard) (Hymenoptera: Encyrtidae) is a facultatively gregarious endoparasitoid of soft scales (Hemiptera: Coccidae). When it develops in superparasitised hosts, the larvae often attack and consume brood mates six or more days post oviposition. Under our laboratory conditions (25±1°C and 14 hours of light followed by 18±1°C and ten hours of darkness in 50-70% R.H.), M. flavus eggs hatched three days after oviposition. Measurements of the mandibles and tentorium indicate there are four larval instars, and M. flavus reaches the fourth instar by day six post oviposition, and pupates on day eight. Thus, cannibalism among M. flavus larvae occurs during the fourth instar. During this instar, M. flavus larvae separate from their attachment to the scale cuticle, to which they were tethered by a respiratory structure during the previous three larval instars. Once detached, they are free to move within the scale, which increases the probability of larval encounters and aggressive behaviours. Moreover, the mandibles of the fourth instar are better adapted for fighting than are those of the first three larval instars, since they are larger and more sclerotized. The cranium and mouthparts of M. flavus have four different types of sensory organs, some of which are almost certainly olfactory, an unexpected function for a larva that presumably is surrounded by an aqueous medium where gustatory sensilla would seem to be more appropriate. The cranium also bears two pairs of what appear to be secretory pores.

Plate-like permanent dental laminae of upper jaw dentition in adult gobiid fish, Sicyopterus japonicus.

Sicyopterus japonicus (Teleostei, Gobiidae) possesses a unique upper jaw dentition different from that known for any other teleosts. In the adults, many (up to 30) replacement teeth, from initiation to attachment, are arranged orderly in a semicircular-like strand within a capsule of connective tissue on the labial side of each premaxillary bone. We have applied histological, ultrastructural, and three-dimensional imaging from serial sections to obtain insights into the distribution and morphological features of the dental lamina in the upper jaw dentition of adult S. japonicus. The adult fish has numerous permanent dental laminae, each of which is an infolding of the oral epithelium at the labial side of the functional tooth and forms a thin plate-like structure with a wavy contour. All replacement teeth of a semicircular-like strand are connected to the plate-like dental lamina by the outer dental epithelium and form a tooth family; neighboring tooth families are completely separated from each other. The new tooth germ directly buds off from the ventro-labial margin of the dental lamina, whereas no distinct free end of the dental lamina is present, even adjacent to this region. Cell proliferation concentrated at the ventro-labial margin of the dental lamina suggests that this region is the site for repeated tooth initiation. During tooth development, the replacement tooth migrates along a semicircular-like strand and eventually erupts through the dental lamina into the oral epithelium at the labial side of the functional tooth. This unique thin plate-like permanent dental lamina and the semicircular-like strand of replacement teeth in the upper jaw dentition of adult S. japonicus probably evolved as a dental adaptation related to the rapid replacement of teeth dictated by the specialized feeding habit of this algae-scraping fish.

Masticatory biomechanics and masseter fiber-type plasticity.

Compared to force-resisting elements of the mammalian feeding apparatus, data on jaw-muscle plasticity are less common. This hinders our understanding of the role of force-producing structures in craniofacial development and integration. Thus, we investigated fiber-type abundance and cross-sectional area in the masseter muscle of growing rabbits subjected to diet-induced variation in masticatory stresses. Three loading cohorts were obtained as weanlings and raised until adult on different diets. Immediately following euthanasia, left-sided masseters were dissected away, weighed, and then divided into anterior, intermediate and posterior sections for fiber-type immunohistochemistry. These data were compared to mandibular proportions and biomineralization from the same subjects. Results indicate that growing mammals fed a tougher, fracture-resistant diet develop: absolutely and relatively lower numbers of Type I jaw-muscle fibers; absolutely larger fiber cross-sectional areas; and relative increases in the amount of Type II fibers. These analyses indicate that an early postweaning dietary shift can induce significant variation in muscle fiber types. Such norms of reaction are comparable to those observed in bony elements. Functionally, the processing of fracture-resistant foods results in jaw adductors potentially characterized by faster contraction times and higher force production capabilities, which may influence the frequency and amplitude of forces experienced by oral tissues.

Morphological and masticatory performance variation of mouth behavior groups.

Food texture preference and product acceptance are hypothesized to be influenced by mouth behavior. Recent work identified four mouth behavior (MB) groups that describe most consumers in the United States: Chewers, Crunchers, Smooshers, and Suckers. While these behavioral preferences are thought to play a significant role in food selection and purchasing decisions, it is unknown how closely they relate to body and oral cavity measures as well as masticatory apparatus performance. Our objectives were twofold: to determine whether MB groups are related to (a) morphological variation in body, head, and oral cavity size and (b) masticatory apparatus performance (i.e., maximum jaw gape, maximum bite forces at the incisors and first molar). Measurements were collected following an online MB assessment (JBMB Mouth Behavior Typing Tool) where participants self-identified as one of the four types of consumers. As expected, univariate associations were observed between masticatory performance and overall body as well as oral cavity size. These relationships did not persist when assessed with multivariate methods. MB groups did not differ by body, head, or oral cavity measurements; maximum gape; or maximum bite force. Because of small sample sizes for Smooshers and Suckers-a reflection of their limited prevalence in the U.S. population-we interpret the results for these groups with caution. We can more confidently conclude based on our sample that Chewers and Crunchers do not differ in size, bite force, or maximum gape, suggesting other factors primarily drive food texture choice and preference in these individuals.

The morphology of the masticatory apparatus facilitates muscle force production at wide jaw gapes in tree-gouging common marmosets (Callithrix jacchus).

Common marmosets (Callithrix jacchus) generate wide jaw gapes when gouging trees with their anterior teeth to elicit tree exudate flow. Closely related cotton-top tamarins (Saguinus oedipus) do not gouge trees but share similar diets including exudates. Maximizing jaw opening theoretically compromises the bite forces that marmosets can generate during gouging. To investigate how jaw-muscle architecture and craniofacial position impact muscle performance during gouging, we combine skull and jaw-muscle architectural features to model muscle force production across a range of jaw gapes in these two species. We incorporate joint mechanics, resting sarcomere length and muscle architecture estimates from the masseter and temporalis to model muscle excursion, sarcomere length and relative tension as a function of joint angle. Muscle excursion from occlusion to an estimated maximum functional gape of 55 deg. was smaller in all regions of the masseter and temporalis of C. jacchus compared with S. oedipus except the posterior temporalis. As a consequence of reduced muscle excursion distributed over more sarcomeres in series (i.e. longer fibers), sarcomere length operating ranges are smaller in C. jacchus jaw muscles across this range of gapes. This configuration allows C. jacchus to act on a more favorable portion of the length-tension curve at larger gapes and thereby generate relatively greater tension in these muscles compared with S. oedipus. Our results suggest that biting performance during tree gouging in common marmosets is improved by a musculoskeletal configuration that reduces muscle stretch at wide gapes while simultaneously facilitating comparatively large muscle forces at the extremes of jaw opening.

Morphometric evaluation of the temporomandibular joint and the masticatory spaces: the role of high-definition MRI.

AIM: The aim of this work was to describe the anatomy of the temporomandibular joint (TMJ), the masticator spaces and their possible variance by means of magnetic resonance imaging MRI. METHODS: We evaluated one TMJ in each of 28 volunteers (14 males and 14 females) without temporomandibular disorders. The TMJ with mouth closed was evaluated on axial, coronal and sagittal planes obtained with a 1.5 Tesla magnetic resonance scanner. MRI scans of the anatomic patterns of the temporomandibular region were analyzed and compared with the classical anatomy notions reported in the literature. Morphometric evaluation of the temporomandibular region and the medial and lateral pterygoid muscles was carried out. RESULTS: MRI anatomy of the TMJ, the masticator spaces and their possible variance were accurately described. In addition, morphometric evaluation of the TMJ and the masticator spaces was performed. Statistical analysis of the measurements showed that the length of the structures related to the glenoid fossa were usually longer in the female than in the males, whereas the condyle and masticator muscles were usually greater in the males than in the females. T-tests showed no significant differences (P > 0.05) between the measurements of the right and left TMJ. CONCLUSIONS: In preoperative maxillofacial surgery assessment, MRI is a useful tool to reduce operating time, avert surgical complications and improve patient outcome.

General morphology and ultrastructure of the radula of Testudinalia testudinalis (O. F. Müller, 1776) (Patellogastropoda, Gastropoda).

The radular morphology of the patellid species Testudinalia testudinalis (O. F. Müller, 1776) from the White Sea was studied using light, electron, and confocal microscopy. The radula is of the docoglossan type with four teeth per row and consisting of six zones. We characterize teeth formation in T. testidinalis as follows: one tooth is formed by numerous and extremely narrow odontoblasts through apocrine secretion; this initially formed tooth consists of numerous vesicles; the synthetic apparatus of the odontoblasts is localized in the apical and central parts of the cells throughout the cytoplasm and is penetrated by microtubules which are involved in the transport of the synthesized products to the apical part of the odontoblast; the newly formed teeth consist of unpolymerized chitin. Mitotic activity is located in the lateral parts of the formation zone. The first four rows contain an irregular arrangement of teeth, but the radular teeth are regularly arranged after the fifth row. The irregularly arranged teeth early on could be a consequence of the asynchronous formation of teeth and the distance between the odontoblasts and the membranoblasts. The morphological data obtained significantly expands our knowledge of the morphological diversity of the radula formation in Gastropoda.

Four-dimensional analysis of stomatognathic function.

Many researchers have attempted to clarify the complex relationships between stomatognathic function and craniofacial morphology. Most studies investigated the trajectories of incisal or condylar points and measured temporomandibular morphology projected onto 2-dimensional radiographic films. Although these methods provided valuable information, their diagnostic capabilities were limited. We introduce a new 4-dimensional (4D) analysis of stomatognathic function that combines the 3-dimensional (3D) computed tomography of the cranium and mandible, dental surface imaging with a noncontact 3D laser scanner, and mandibular movement data recorded with a 6 degrees of freedom jaw-movement analyzer. This method performs dynamic and precise simulations that can analyze and display condyle to fossa distances and occlusal contacts during mandibular function. These comprehensive relationships can be analyzed and displayed not only at intercuspal position, but also at any mandibular position during functional movements. We believe that our 4D analyzing system will be useful for diagnosing temporomandibular disorders of patients with jaw deformities and other malocclusions.

Changes in hyoid position following treatment of Class II division1 malocclusions with a functional appliance.

OBJECTIVE: The aim of this study was to determine change of hyoid bone position following treatment with functional appliance in patients with class II division 1 malocclusion. DESIGN: This study performed on pre and post treatment lateral cephalograms of 28 patients with class II div I malocclusion treated with Farmand functional appliance on average of 11 months. The range of age of girls was 10-13 years and boys 11-14 years. To study the results, t test and Pearsons correlation coefficient were used. RESULTS: Hyoid bone shifted significantly (P value < 0.01) forward in horizontal dimension and non significantly upward in vertical dimension. There was no significant difference between three groups in facial growth patterns with respect to hyoid bone position alterations in horizontal dimension but was significant between horizontal and vertical growth pattern in vertical dimension. (P value < 0.05). There was significant correlation between decrease ofANB angle with forward movement of hyoid bone. CONCLUSION: Following treatment with Farmand functional appliance, significant changes occur in the position and anterior displacement of the hyoid bone.

Is the buccal compartment a masticatory space extension or an anatomic space in itself? Evidence based on medical images and human cadaver dissection.

OBJECTIVES: According to some authors, the buccal space is incompletely closed with no real anatomical separation from the masticator space, and also has no fascial limit toward the cranial and caudal regions. However, several other authors consider this anatomic area to be a separated space. The goal of this study was to provide a detailed description of the normal anatomy using medical images and human cadaveric head material dissection of this facial anatomic region, to precisely clarify its condition as an extension of the masticator space or an independent space. METHODS: The buccomasseteric area in 25 male and female patients aged 14-68 years, who were referred for various head and neck disorders that did not compromise the masticatory and buccal area, was analyzed by magnetic resonance imaging on the axial and coronal planes. The region was further examined by dissection of the buccomasseteric area in four heads of fresh adult male and female human cadavers aged 30-65 years. RESULTS: The findings demonstrated that the buccal compartment should be considered part of the masticator space, rather than a space in itself. This was mainly because a corridor was positioned medially to the tendon of the masseter muscle that communicated the infratemporal region of the masticator space with the buccal region, with no fascial barrier at this level that could separate it from the masticator space. CONCLUSIONS: The present study suggests that the buccal compartment is part of the masticator space, rather than a space in itself.

Three-dimensional CT examination of the mastication system in the giant anteater.

The gross anatomy of the mastication system of the giant anteater (Myrmecophaga tridactyla) was examined by means of three-dimensional image analysis. The anteater rotates the mandibles medially and laterally to control its tongue when it is elongated and to house it when it is relaxed. Three-dimensional CT image analysis demonstrated that the shape and size of the oral cavity changes drastically when the mandibles are rotated. The oral cavity expands bilaterally when the dorsal part of the mandibles bend medially. Macroscopic observations and muscle-weight data supported the observation that the superficial temporal and medial pterygoid muscles act as the main medial and lateral rotators of the mandible, respectively. The low height of the mandibular ramus and the incomplete zygomatic arch in this species represent adaptations for the rotational movement of the mandibles, since they both contribute to the medially oriented transmission of force from the temporal muscles and to preventing collision between the mandibles and the cranium during the rotational movement.

A three-dimensional model of the human masticatory system, including the mandible, the dentition and the temporomandibular joints.

The objective of this study was to create a three-dimensional mathematical model of a human masticatory system, including the mandible, the dentition and the temporomandibular joints. Object of research was one 20 year old dead man. The research was approved by Committee of bioethics (Kaunas University of Medicine). Required extent of computed tomography scanning and required high amount and high resolution of images increased X-ray radiation for the object and made this research impossible to perform on alive human. Spiral computed tomography scanning was performed to achieve two-dimensional images, necessary for creating three-dimensional model. The 3D modeling was done using the "Image pro plus" and "Imageware"software. A three-dimensional physiological (normal) model of a human masticatory system, simulating the mandible, the dentition and the temporomandibular joints was generated. This model system will be used subsequently in stress analysis comparison for the physiological and pathological systems after improvement of its physical properties. We suggest that computer simulation is a promising way to study musculoskeletal biomechanics of masticatory system.

Clase metodológica instructiva de la asignatura Sistema Masticatorio, orientada a la relación básico-clínica / Instructive methodological class of the Masticatory System subject, oriented towards the basic-clinical relationship

RESUMEN La preparación del personal docente en las universidades exige un alto nivel científico y de maestría pedagógica. Todo esto requiere un esmerado trabajo metodológico que garantice una planificación organización, regulación y control del proceso docente educativo. Para esto se diseñó una clase metodológica instructiva sobre mucosa oral, de la asignatura Sistema Masticatorio, en la disciplina Histología, con el objetivo de instruir al profesor en la utilización de la vinculación básico-clínica. Se indicó a los profesores cómo relacionar el contenido de la clase con la clínica, desde el punto de vista de las lesiones precancerosas y sus factores de riesgo. Se logró la instrucción de los docentes en la utilización del contenido de las asignaturas y disciplinas de las Ciencias Básicas con la relación básico-clínica, y así se contribuyó a ampliar el espectro científico metodológico de los docentes en la Universidad de Ciencias Médicas de Matanzas (AU).

ABSTRACT Training the teaching staff in the universities demands a high scientific level and pedagogical expertise. All of these requires a careful methodological work guaranteeing the teaching-learning process planning, organization, regulation and control. For that the authors designed an instructive methodological lesson aimed to train the teaching staff in the use of the basic-clinical link during a lesson of the subject Masticatory System about Oral Mucosa, in the subject Histology. They indicate to professors how to relate the lesson content to clinic from the point of view of pre-cancer lesions and its risk factors. Training the teaching staff in the use of subjects and disciplines of the Basic Sciences with the basic-clinical relation, the authors contribute to widening the scientific methodological spectrum of the teaching staff of the Matanzas University of Medical Sciences (AU).

Drug-Induced Sleep Endoscopy.

Drug-induced sleep endoscopy (DISE) is an upper airway evaluation technique in which fiberoptic examination is performed under conditions of unconscious sedation. Unique information obtained from this 3-dimensional examination of the airway potentially provides additive benefits to other evaluation methods to guide treatment selection. This article presents recommendations regarding DISE technique and the VOTE Classification system for reporting DISE findings and reviews the evidence concerning DISE test characteristics and the association between DISE findings and treatment outcomes.

Zygomatic Arch Cortical Area and Diet in Haplorhines.

The influence that various types of ingested foods have on the form (size and shape) of specific features of the masticatory system is an area in which many questions remain unanswered. The bony zygomatic arch, the focus of this study, is directly linked to the masticatory system because it serves as the anchor for the masseter muscle, a primary muscle of chewing and source of masticatory force. However, the influence of diet and the forces associated with different diet types on the arch's internal bone architecture is not well understood. Despite the breadth of work centered around the craniofacial complex and biomechanics of mastication, there is a need for further investigations into the functional relationships between specific bony features that experience high strains, (e.g., the zygomatic arch), and the masticatory forces generated by different diets (e.g., mechanically resistant versus non- mechanically resistant) across non-human primates. A hypothesis and series of predictions assessing diet in relation to variability in cortical area distributions and values of section moduli (measures of bone strength) throughout the zygomatic arch were tested in a sample of haplorhine primates. Cortical area and measures of section moduli appear to track with the known masticatory strain distribution along the zygomatic arch. Pairwise comparisons between closely related taxa of different diets reveal significant differences in anterior cortical area and section moduli values. These results imply that differences in masticatory loading due to diet manifest in the zygomatic arch's internal bone structure. Anat Rec, 299:1789-1800, 2016. © 2016 Wiley Periodicals, Inc.