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Chewing

Chewing, also known as mastication, is a rhythmic, sensory-motor process that mechanically breaks down food in the oral cavity using the teeth, jaws, and associated muscles to form a cohesive bolus suitable for swallowing and subsequent digestion.^[1] This initial stage of digestion reduces food particle size, mixes it with saliva to initiate enzymatic breakdown, and enhances nutrient absorption by increasing surface area for gastric processing.^[2] In humans, chewing involves coordinated cycles of jaw opening and closing, typically occurring at a frequency of 0.8 to 1.2 Hz, which evolve from simple vertical movements in infancy to more complex rotary and lateral motions in adulthood.^[2] The anatomy of chewing centers on the mandible (lower jaw) articulating with the maxilla (upper jaw) at the temporomandibular joints, supported by four primary muscles: the masseter, temporalis, medial pterygoid, and lateral pterygoid, all innervated by the mandibular branch of the trigeminal nerve (cranial nerve V).^[1] These muscles enable elevation, depression, protrusion, retraction, and lateral deviation of the mandible, with the masseter providing powerful closing force and the pterygoids facilitating grinding motions.^[1] The teeth—incisors for cutting, canines for tearing, and molars for grinding—play a crucial role in fragmenting food, while accessory structures like the tongue and buccinator muscle position and contain the bolus within the oral cavity.^[2] Physiologically, chewing is centrally controlled by pattern generators in the brainstem, modulated by sensory feedback from periodontal ligaments, muscle spindles, and oral mucosa to adjust force and rhythm based on food texture and hardness.^[3] Salivary glands secrete enzymes like amylase during mastication, which begins carbohydrate digestion, while the process also promotes gut hormone release that influences appetite and satiety.^[4] Beyond digestion, efficient chewing supports oral health, prevents choking, and in early childhood, its development influences dietary habits and orofacial growth, maturing variably from 8 months to over 6 years.^[2]

Anatomy of Chewing

Oral Structures

Human adults possess 32 permanent teeth, arranged in two arches of 16 each, which are essential for the mechanical breakdown of food during mastication.^[5] These teeth are categorized into four types based on their shape, position, and function: incisors, canines, premolars, and molars.^[6] Incisors, numbering eight and located at the anterior of each arch, are chisel-shaped for cutting and incising food into manageable pieces.^[7] Canines, four in total and positioned laterally to the incisors, feature pointed cusps suited for tearing and piercing fibrous or tough materials.^[7] Premolars, also called bicuspids and totaling eight, possess broader surfaces with two cusps each to crush and grind semi-solid foods.^[7] Molars, the largest group with 12 teeth at the posterior arches, have multiple cusps for extensive grinding and pulverizing of food into a bolus suitable for swallowing.^[7] Collectively, these teeth enable the cutting, mixing, and grinding actions central to mastication.^[7] The temporomandibular joint (TMJ) functions as the pivotal synovial hinge linking the mandible to the cranium, facilitating the range of motions required for chewing.^[8] Anatomically, it consists of the mandibular condyle articulating with the temporal bone's mandibular fossa and articular eminence, enclosed by a fibrous capsule, an articular disc, and supported by ligaments, with synovial fluid enabling smooth gliding.^[8] This structure permits hinge-like rotation for jaw elevation and depression, as well as translational sliding for protrusion, retraction, and lateral excursions, allowing precise alignment of teeth during the grinding process.^[8] These movements position the occlusal surfaces of the teeth to effectively process food without excessive strain on surrounding tissues.^[8] Soft tissues within the oral cavity, including the tongue, lips, and cheeks, actively manage food during chewing to enhance efficiency and containment.^[9] The tongue, a muscular hydrostat, manipulates and repositions food boluses between the teeth for optimal occlusion, while also mixing it with saliva to form a cohesive mass.^[2] The lips seal the anterior oral opening to prevent food escape during initial bites, and the cheeks provide lateral containment, using their buccinator muscle tone to keep material centered for grinding.^[9] Together, these structures ensure food remains in the occlusal contact zone, maximizing mechanical breakdown and minimizing loss.^[2] Salivary glands support chewing by secreting saliva that lubricates the oral environment and begins chemical digestion.^[10] The three major pairs—parotid, submandibular, and sublingual—produce approximately 1-1.5 liters of saliva daily, which moistens food to reduce friction against teeth and mucosa during mastication.^[10] Notably, saliva contains alpha-amylase, an enzyme secreted primarily by the parotid glands, that hydrolyzes starches into maltose and dextrins, initiating carbohydrate breakdown even before swallowing.^[11] This dual lubrication and enzymatic action eases bolus formation and protects enamel from abrasive wear.^[10] These oral structures are mobilized by the muscles of mastication to coordinate the overall process of food comminution.^[1]

Muscles of Mastication

The muscles of mastication consist of four primary pairs of skeletal muscles responsible for the movements of the mandible during chewing in humans. These include the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles, which collectively enable elevation, depression, protrusion, retraction, and lateral excursions of the jaw.^[1] The masseter muscle, a powerful superficial quadrangular muscle, originates from the inferior border and medial surface of the zygomatic arch and inserts along the lateral surface of the mandibular ramus and the coronoid process of the mandible. Its primary action is to elevate the mandible to approximate the teeth, with superficial fibers contributing to protrusion and deeper fibers aiding retraction. The masseter is innervated by the masseteric nerve, a branch of the mandibular division of the trigeminal nerve (cranial nerve V3).^[1] The temporalis muscle, a fan-shaped muscle, arises from the temporal fossa and the inferior temporal line and inserts into the coronoid process and the anterior border of the mandibular ramus via its tendon. The anterior and middle fibers elevate the mandible, while the posterior fibers retract it. Innervation is provided by the deep temporal nerves, also from the mandibular division of the trigeminal nerve (V3).^[1] The medial pterygoid muscle, located medially in the infratemporal fossa, has a superficial head originating from the pyramidal process of the palatine bone and the tuberosity of the maxilla, and a deep head from the medial surface of the lateral pterygoid plate; it inserts into the medial surface of the mandibular ramus and angle of the mandible. It elevates and protrudes the mandible and assists in lateral movements toward the opposite side. Like the others, it is innervated by the medial pterygoid nerve from the mandibular division of the trigeminal nerve (V3).^[1] The lateral pterygoid muscle, the primary muscle for jaw depression, has an upper head originating from the infratemporal surface of the greater wing of the sphenoid bone and a lower head from the lateral surface of the lateral pterygoid plate; it inserts into the pterygoid fovea of the condylar process, the articular disc, and the temporomandibular joint capsule. It depresses and protrudes the mandible and facilitates side-to-side grinding movements. Innervation comes from the lateral pterygoid nerve, derived from the mandibular division of the trigeminal nerve (V3).^[1] All four pairs of muscles are innervated by branches of the mandibular nerve (V3), which exits the skull through the foramen ovale, ensuring coordinated activation for mastication.^[1] Biomechanically, these muscles generate significant forces during chewing; for instance, the masseter can produce up to 200-250 N of force, contributing to the overall average human maximum bite force of 500-700 N at the molars.^[12]^[13] Their coordinated contraction enables rhythmic cycles of jaw opening and closing, with synergistic actions balancing forces across the temporomandibular joint.^[1]

Physiology of Chewing

Motor Program

The motor program of chewing, or mastication, refers to the coordinated sequence of jaw movements that facilitate the breakdown and preparation of food for swallowing in humans. This program is executed through rhythmic cycles involving specific phases that ensure efficient trituration and bolus formation. The process is primarily driven by a central pattern generator (CPG) located in the brainstem, which produces the basic rhythmic output for jaw opening and closing without requiring continuous external input.^[14] The chewing cycle consists of three main stages: the opening phase, the closing phase, and the power stroke. During the opening phase, the jaw depresses to allow repositioning of the food bolus by the tongue, typically involving a downward and slightly posterior movement. The closing phase follows, where the jaw elevates to bring the teeth into initial contact with the food, initiating grinding and lateral shifts for shearing. The power stroke, embedded within the closing phase, applies maximum force to crush and fragment the food, primarily through occlusal contacts between molars and premolars.^[15]^[16] Chewing occurs at a rhythmic frequency of approximately 0.8-1.5 Hz, with each cycle lasting about 0.67-1.25 seconds, enabling efficient processing without fatigue. A typical sequence involves 20-40 cycles to form a swallowable bolus from a standard food portion, though this varies with bolus size and individual factors. The muscles of mastication, such as the masseter and temporalis, activate in a patterned manner across these phases to generate the necessary force and velocity. Central to bolus formation is the trituration process, where food particles are reduced in size through repeated crushing and grinding until they reach a median diameter of less than 2 mm, allowing cohesion with saliva for safe swallowing. This particle size reduction ensures the bolus is sufficiently fragmented and lubricated, typically achieved after the aforementioned cycles. The CPG coordinates this rhythm, but the program adapts to food properties; for instance, harder textures prolong cycle duration by 10-20% to accommodate increased resistance and enhance breakdown efficiency.^[17]^[18]

Neural and Sensory Control

The neural control of chewing is primarily orchestrated by structures in the brainstem, including the pons and medulla oblongata, which house the central pattern generator (CPG) responsible for generating the rhythmic motor patterns of mastication.^[3] The trigeminal motor nucleus, located in the pons, serves as the key output center, containing motoneurons that innervate the jaw-closing and jaw-opening muscles to coordinate the alternating phases of the chewing cycle.^[19] Voluntary initiation of chewing involves higher cortical areas, such as the primary motor cortex and supplementary motor area, which provide descending inputs to the brainstem CPG to modulate the onset and intensity of the movement.^[20] Sensory inputs play a crucial role in regulating and adapting the chewing process through feedback mechanisms. Mechanoreceptors in the periodontal ligaments detect bite forces and tooth positions, providing positive feedback that enhances jaw-closing muscle activity during the slow closing phase of mastication.^[21] Muscle spindles in the jaw-closing muscles, such as the masseter and temporalis, contribute proprioceptive information about muscle length and tension, helping to fine-tune jaw movements and maintain rhythm.^[3] Receptors in the temporomandibular joint (TMJ), including Ruffini-like endings and free nerve endings, sense joint position and loading, integrating with other orofacial afferents to modulate the CPG output and prevent excessive strain.^[22] Reflex pathways ensure protective and adaptive responses during chewing. The jaw-opening reflex, a disynaptic inhibitory response mediated by trigeminal sensory afferents, rapidly inhibits jaw-closing muscles in response to sudden noxious or mechanical stimuli, such as unexpectedly hard food, thereby protecting the oral structures from injury.^[23] The chewing rhythm adapts to food consistency via sensory feedback; for instance, harder textures elicit stronger periodontal and muscle spindle inputs, prolonging the jaw-closing phase and increasing cycle duration, while softer foods result in shorter, less forceful cycles.^[24] The trigeminal sensory nucleus, comprising the principal sensory nucleus and spinal trigeminal nucleus in the brainstem, processes these diverse sensory inputs from the orofacial region, relaying them to the CPG and higher centers for integration.^[25] Higher brain structures, including the basal ganglia, contribute to the learning and refinement of chewing patterns, facilitating the acquisition of efficient motor sequences through reinforcement of rhythmic behaviors.^[26] Disruptions in these pathways, as seen in Parkinson's disease, impair chewing rhythm, leading to slower mastication speeds and reduced coordination due to dopaminergic deficits in the basal ganglia.^[27]

Health and Nutrition

Nutritional Role

Chewing plays a crucial role in the initial stages of digestion by mechanically breaking down food into smaller particles, which increases the surface area available for enzymatic action and enhances the efficiency of subsequent gastric processing.^[28] This process, known as mastication, reduces particle size, allowing for better mixing with digestive juices and preventing large boluses that could impede stomach motility.^[29] Some studies suggest that increased chewing cycles can result in faster gastric emptying and smaller particle sizes, potentially improving nutrient absorption.^[30] During chewing, saliva integrates with the food bolus, where enzymes such as α-amylase initiate the hydrolysis of starches into simpler sugars like maltose, beginning carbohydrate digestion in the oral cavity.^[31] This enzymatic activity can achieve considerable starch breakdown within seconds of mastication, contributing up to 50% of total starch hydrolysis before the bolus reaches the stomach.^[32] Additionally, salivary mucins provide lubrication, facilitating safe swallowing and protecting the esophageal lining while aiding the formation of a cohesive bolus for efficient transit.^[33] Beyond basic digestion, chewing enhances nutrient bioavailability by disrupting plant cell walls, which releases compounds like carotenoids from vegetables such as carrots and mangoes, making them more accessible for absorption in the intestines.^[34] For instance, extended mastication increases the bioaccessibility of β-carotene from mango tissue by promoting greater cellular rupture during oral processing.^[35] Chewing also promotes satiety through prolonged oral exposure, which signals fullness via neural and hormonal pathways, linking it to weight management; randomized trials show that increasing chews per bite—such as from 15 to 40—can reduce subsequent energy intake by approximately 12%.^[36] Some health experts recommend chewing each bite 30-40 times for optimal nutrient release and digestive comfort, particularly for fibrous foods.^[37]

Disorders and Health Effects

Temporomandibular joint disorder (TMD) is a common condition affecting the jaw joint and surrounding muscles, characterized by pain, limited jaw movement, and clicking sounds during chewing. It impacts approximately 5-12% of the population, with symptoms including pain in the temporal muscle (prevalent in 92% of cases) and pain during mouth opening (89%).^[38] TMD is more prevalent in women, with a female-to-male ratio of about 2:1, potentially due to hormonal and biomechanical factors.^[39] Bruxism, involving involuntary teeth grinding or clenching, particularly nocturnal grinding, affects 5-8% of adults and leads to significant tooth wear, headaches, and muscle fatigue.^[40] Excessive chewing forces contribute to dental attrition, a mechanical wear of tooth surfaces from prolonged tooth-to-tooth contact, distinct from chemical erosion but often exacerbated by habits like gum chewing. Poor chewing efficiency can result in inadequate bolus formation, increasing risks of choking and aspiration, especially in individuals with neuromuscular impairments or the elderly. Inadequate mastication may also delay gastric emptying, promoting gastroesophageal reflux disease (GERD) by allowing undigested food to reflux into the esophagus. While chewing gum can reduce stress and anxiety by lowering cortisol levels and improving alertness, excessive use may worsen TMD symptoms through overuse of jaw muscles. Interventions for these disorders include occlusal splints, which protect teeth from grinding and reduce TMD pain in many cases. Orthodontic treatments address malocclusions contributing to TMD, while behavioral therapies like cognitive behavioral therapy help manage stress-related clenching. For elderly patients with chewing difficulties, nutritional recommendations emphasize soft diets, such as pureed foods and smoothies, to prevent malnutrition and choking risks while maintaining adequate intake.

Chewing in Animals

Variations by Species

Chewing mechanisms exhibit significant variations across animal species, reflecting adaptations to diverse diets and ecological niches. In mammals, dentition and jaw morphology are primary determinants of masticatory efficiency. Carnivorous mammals, such as dogs and wolves, possess specialized carnassial teeth—typically the fourth upper premolar and first lower molar—that function as shearing blades, slicing through flesh and connective tissue with scissor-like action during jaw closure.^[41] This adaptation allows for rapid processing of meat without extensive grinding, prioritizing penetration and tearing over pulverization.^[42] Herbivorous mammals, exemplified by horses, feature hypsodont molars with high crowns that continuously erupt to compensate for wear from abrasive plant material. These molars facilitate lateral grinding motions, where the occlusal surfaces with enamel ridges and infoldings triturate fibrous vegetation into smaller particles for digestion.^[43] In contrast, omnivorous mammals like pigs exhibit bunodont dentition with low, rounded cusps and thick enamel, enabling versatile chewing of both plant and animal matter through combined crushing and shearing actions. Non-mammalian species display even more divergent strategies, often compensating for the absence of true mastication with alternative anatomical features. Birds lack teeth entirely and rely on the muscular gizzard—a thickened portion of the stomach—to grind ingested food, aided by ingested grit that acts as an abrasive medium to break down seeds, insects, and other items.^[44] Reptiles such as alligators employ minimal chewing, using conical teeth and powerful jaws primarily for grasping and crushing prey through puncture and compression rather than cyclic mastication.^[45] This results in whole or partially fragmented swallowing, with gastric acids handling further breakdown.^[46] Certain adaptations further diversify chewing across species. Ruminants, including cattle and sheep, possess a four-chambered stomach that enables rumination, where partially digested boluses of cud are regurgitated for re-chewing to enhance microbial fermentation of cellulose-rich forage.^[47] Rodents, adapted for gnawing on hard seeds and wood, have continuously growing incisors with open roots and self-sharpening chisel edges, maintained by constant abrasion to prevent overgrowth.^[48] Specific examples highlight these variations' extremes. Elephants sequentially replace their molars up to six times over a lifetime, with each successive set larger to accommodate increasing volumes of abrasive browse, the final set emerging around age 30 and enduring for decades.^[49] Koalas, specialized folivores, have sharp, ridged molars optimized for shearing and grinding tough, fibrous eucalyptus leaves, which comprise their exclusive diet and require efficient comminution for nutrient extraction.^[50]

Evolutionary Aspects

Chewing, or mastication, first emerged as a defining feature in the evolution of jawed vertebrates, known as gnathostomes, approximately 420-400 million years ago during the Silurian-Devonian transition.^[51] Prior to this, early arthropods such as trilobites, which dominated marine ecosystems from the early Cambrian period onward (around 521 million years ago), lacked true jaws and relied on simple grinding mouthparts like the hypostome for processing food.^[52] The development of jaws in placoderms, the earliest gnathostomes, marked a pivotal innovation, enabling more efficient biting and initial forms of intraoral food processing through rudimentary dentitions structured in whorl-like patterns.^[53] This adaptation arose from the repurposing of pharyngeal gill arches into a hinged mandibular mechanism, allowing gnathostomes to dominate aquatic niches by facilitating predation and resource partitioning.^[54] The transition from aquatic to terrestrial environments during the Devonian period (about 375 million years ago) further complexified chewing mechanics as early tetrapods evolved. Stem tetrapods, such as those in the Ichthyostega lineage, exhibited cranial reorganizations that increased the complexity of bone-to-bone contacts and joint articulations, enhancing bite force and intraoral manipulation compared to their fish-like ancestors.^[55] These changes supported the processing of tougher, more abrasive terrestrial foods, laying the groundwork for advanced mastication. In mammalian evolution, a major development occurred with the refinement of heterodont dentition—characterized by differentiated incisors, canines, premolars, and molars—originating in synapsid reptiles during the late Paleozoic but achieving greater diversity post-Cretaceous extinction around 66 million years ago.^[56] This heterodonty enabled specialized chewing functions, from shearing to grinding, and proliferated in the Cenozoic era among ungulates adapting to herbivory. Cenozoic ungulates, such as horses and ruminants, evolved high-crowned (hypsodont) molars with complex occlusal surfaces to withstand abrasive grasses in expanding savannas, correlating with dietary shifts driven by climate-induced habitat changes.^[57]^[58] In primate and human evolution, chewing adaptations intertwined with cognitive advancements. Early hominins like Homo erectus (appearing around 1.9 million years ago) possessed enlarged molars and robust jaws suited for processing tough, unprocessed plant materials and gritty foods, reflecting a diet that demanded high masticatory forces.^[59] However, a key genetic mutation in the MYH16 gene, dated to approximately 2.4 million years ago, weakened jaw-closing muscles, reducing masticatory demands and allowing cranial space for accelerated brain expansion—a correlation observed across primates where diminished chewing efficiency freed metabolic resources for larger brains. This shift coincided with the control of fire and cooking around 1.8 million years ago, which softened foods and further contributed to reduced jaw size and tooth robusticity in modern Homo sapiens, enabling encephalization without compromising nutritional intake.^[60]

Chewing in Technology

Mechanical Models

Mechanical models of chewing encompass engineering simulations and physical devices engineered to replicate the biomechanical aspects of mastication for research purposes. These models include in vitro physical simulators, such as artificial mouths equipped with actuators that mimic jaw movements, and computational approaches like finite element analysis (FEA) used to predict stress distributions in teeth and the temporomandibular joint (TMJ).^[61]^[62] In vitro models typically feature robotic jaws driven by servomotors or stepper motors to simulate muscle forces and mandibular motion in three dimensions, often incorporating multi-station setups for parallel testing. Soft tissues, such as oral mucosa and gingiva, are represented using compliant materials like silicone rubber to approximate biomechanical properties and enable realistic interactions during simulated chewing cycles. These components allow for controlled replication of vertical, lateral, and protrusive movements, with early commercial examples like the Willytec simulator emerging in the late 1990s to standardize preclinical evaluations.^[63]^[64]^[65] Finite element analysis models treat the jaw system as a deformable structure, incorporating detailed geometries of bones, teeth, and TMJ derived from CT or MRI data to compute strain and stress under applied loads. These simulations often integrate muscle force vectors and contact mechanics between occlusal surfaces, providing insights into load transmission without physical prototypes. Seminal FEA applications have focused on dynamic biting scenarios, validating results against experimental data to refine model accuracy.^[62]^[66] In research, these models facilitate the evaluation of food texture breakdown under simulated mastication, quantifying particle size reduction and bolus formation to inform nutritional science. They also assess the durability of dental prosthetics, such as crowns and implants, by subjecting specimens to repeated loading that mimics long-term wear. Modern simulators replicate typical chewing forces of 150-200 N and cycle frequencies of 1-2 Hz, aligning with physiological parameters to enhance predictive reliability for clinical outcomes.^[61]^[67]^[68]

Industrial and Biomedical Applications

In the food industry, chewing simulators are employed to analyze food texture during product development, particularly for items like gums and snacks, by replicating human mastication to assess breakdown and sensory attributes.^[69] Robotic systems equipped with artificial teeth and tongues estimate texture parameters such as hardness and cohesiveness, enabling precise evaluation of how products like roasted peanuts or model foods change during simulated chewing cycles.^[70] These tools provide multimodal sensory feedback on appearance, sound, texture, smell, and taste, aiding manufacturers in optimizing formulations for consumer appeal.^[71] In biomedical applications, chewing simulators test the durability and performance of dental prosthetics, such as dentures and crowns, by subjecting them to repeated chew cycles that mimic oral forces.^[72] For instance, simulations of mastication on 5Y-TZP ceramic crowns demonstrate their structural stability under conditions replicating up to 1.2 million cycles, informing prosthetic design to withstand long-term use.^[73] Such devices ensure reliability in restorative dentistry by evaluating material wear and fracture resistance, with studies confirming their consistency across preclinical tests.^[74] Additionally, rehabilitation devices like the TheraBite Jaw Motion Rehabilitation System support temporomandibular disorder (TMD) therapy by facilitating controlled jaw exercises to restore motion and alleviate pain through passive stretching.^[75] Chewing gum manufacturing relies on a gum base composed of resins, waxes, and elastomers to provide chewiness and elasticity, which is melted and mixed with sweeteners, flavors, and softeners in a heated process to form the final product.^[76] Flavor release is engineered through timed diffusion during mastication, where hydrophobic components interact with the base to extend sensory duration, as detailed in formulations using menthol or mint particulates.^[77] The global chewing gum market reached approximately $29 billion annually as of 2025, driven by innovations in base ingredients and delivery systems.^[78] The U.S. Food and Drug Administration (FDA) incorporates chewing models in evaluating drug release from tablets, particularly for abuse-deterrent formulations of opioids, using in vitro simulations to predict release under mastication conditions.^[79] These methods involve mechanical chewing apparatuses to assess how crushing or chewing affects extended-release profiles, ensuring safety in pharmaceutical development.^[80] In animal feed processing, machinery such as extruders simulates chewing-like actions to produce chewable pet foods from raw ingredients, applying heat and pressure to create textured products that enhance palatability and digestion.^[81] Building on mechanical models of chewing, these systems optimize feed formulations for livestock and pets by controlling particle size and consistency.^[69]

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Birds swallow their food whole, and their gizzard (a muscular part of their stomach) grinds up the food so they can digest it. ... No. They look like teeth ...
[43]
Form and function of the feeding apparatus of Alligator ... - PubMed
Alligator grabs its prey with forward lunges or rapid lateral movements of the head. It does not engage in regular masticatory cycles.
[44]
The Crocodilian Body - iucncsg.org
Jaws and Teeth ... Crocodilian jaws are designed for grabbing and holding prey. The teeth are conical and designed to penetrate and hold, rather than cut and chew ...Missing: mastication | Show results with:mastication
[45]
The ruminant digestive system - University of Minnesota Extension
Ruminant stomachs have four compartments: the rumen, the reticulum, the omasum and the abomasum. Rumen microbes ferment feed and produce volatile fatty acids, ...
[46]
Oral disorders of exotic rodents - PMC - PubMed Central - NIH
Malocclusion is the most common oral disorder of rodents, whether it results from the abnormal growth of incisors only, as for most rodents, or is caused by the ...
[47]
The Koalas' Diet & Digestion - Australian Koala Foundation
Koalas primarily eat eucalyptus leaves, which are fibrous and low in nutrition. They have a special caecum with bacteria to digest fiber, and their teeth are ...
[48]
Evolution: How vertebrates got their bite - eLife
Nov 15, 2022 · Most vertebrates, including humans, evolved from jawless fish which roamed the oceans 420–390 million years ago (Forey and Janvier, 1993).
[49]
How trilobites conquered prehistoric oceans - Natural History Museum
Trilobites appeared in the Cambrian Period, which lasted from 538 million to 485 million years ago. At the beginning of the Cambrian Period, the rate of ...
[50]
A 400-million-year-old placoderm reveals how the first dentitions ...
Sep 17, 2025 · Placoderms are the first vertebrates to have developed jaws. It was long thought that placoderms had no teeth on their jaws, and that teeth had ...
[51]
Evolution and development of the fish jaw skeleton - PMC - NIH
The jaw evolved from repeating pharyngeal segments first present in chordate ancestors as respiratory structures, later giving rise to cartilaginous branchial ...
[52]
Early tetrapod cranial evolution is characterized by increased ...
Sep 9, 2022 · We find that bone loss across the origin of tetrapods is associated not only with increased complexity of bone-to-bone contacts but also with decreasing ...
[53]
On the earliest evolution of the mammaliaform teeth, jaw joint ... - NIH
Jul 19, 2024 · Mammals are characterized by having heterodont teeth, of which most of the check teeth are supported by divided roots and display diverse morphologies.
[54]
Cenozoic Mammalian Herbivores From the Americas
Nov 1, 2000 · Dental adaptations for specialized terrestrial browsing are first recognized during the early Cenozoic (Paleocene-Eocene). Mammalian herbivores ...
[55]
Molar Tooth Diversity, Disparity, and Ecology in Cenozoic Ungulate ...
Aug 10, 2025 · A classic example of adaptive radiation is the diversification of Cenozoic ungulates into herbivore adaptive zones.
[56]
Dental microwear and diets of African early Homo - PubMed
These results suggest that none of the early Homo groups specialized on very hard or tough foods, but that H. erectus and Swartkrans Member 1 individuals ate, ...Missing: enlarged | Show results with:enlarged
[57]
Food for Thought: Was Cooking a Pivotal Step in Human Evolution?
Feb 26, 2018 · Fossils show the teeth and digestive tract of Homo erectus decreased in size around the same time brain size increased. This evidence likely ...Missing: reduced | Show results with:reduced
[58]
Systematic review of chewing simulators: Reality and reproducibility ...
This review found that no chewing simulator fully reproduces human mastication, and no ideal simulator exists to standardize trials.
[59]
A Dynamic Jaw Model With a Finite-Element Temporomandibular Joint
Sep 12, 2019 · The model combines a muscle driven rigid body model of the jaw region with a detailed finite element model (FEM) disk and elastic foundation (EF) articular ...Introduction · Materials and Methods · Results · Discussion
[60]
In vitro evaluation of a mechanical testing chewing simulator
In this in vitro study, the force-profile of a commonly used chewing simulator (Williytec, Munich, Germany) utilizing fixed weights for loading was evaluated.
[61]
Architecture and design of a robotic mastication simulator for ...
Major features of the robot, including the motion control system, are presented. Experimental results for free chewing, soft-food chewing, and hard-food chewing ...<|control11|><|separator|>
[62]
[PDF] Wear of ceramics and enamel in a chewing simulator
Alumina Reinforced introduced in the 1970s as a result of McLean and Hughes, research, glass ceramics in 1968, and Leucite-reinforced glass ceramics with ...
[63]
Dynamic finite element modelling of the macaque mandible during a ...
Oct 16, 2023 · Finite element models (FEMs) combined with rigid-body analysis have been used to study the function of the temporomandibular joint (TMJ) in ...Abstract · Introduction · Methods · Discussion<|control11|><|separator|>
[64]
Using a chewing simulator for fatigue testing of metal ceramic crowns
The widespread SD Mechatronik Chewing Simulator (formerly Willytec) was used as a fatigue testing machine. This machine can be equipped with additional weights ...Missing: history | Show results with:history
[65]
Mean chewing frequencies for each individual investigated. Error ...
Human mastication frequencies generally vary from 0.94 Hz to 2.17 Hz [76] , which corresponds to the physiological chewing patterns investigated in this work.
[66]
Food Oral Processing—An Industry Perspective - Frontiers
Development of a chewing simulator for food breakdown and the analysis of in vitro flavor compound release in a mouth environment. J Food Eng. (2007) 82:189 ...<|separator|>
[67]
[PDF] Food Texture Estimation Using Robotic Mastication Simulator ...
In this paper, we propose a food texture estimation system using a robotic mastication simulator equipped with teeth and a tongue.
[68]
[PDF] Chewing Simulator Provides Sensory Information
The chewing simulator provides sensory information on appearance, sound, texture, smell, and taste, and feedback on the five major human senses.
[69]
The Role of Chewing Simulators | SpringerLink
Oct 16, 2025 · These devices replicate the complex movements and forces involved in mastication, enabling simulations of material wear and fatigue resistance.
[70]
Effect of Simulated Mastication on Structural Stability of Prosthetic ...
Jan 30, 2023 · This study aims at determining the durability of such 5Y-TZP crowns under lab conditions simulating the conditions in the oral cavity during mastication.
[71]
Do chewing simulators influence the test results of dental materials ...
Jun 25, 2023 · This equipment performs mechanical fatigue tests that closely simulate the conditions found in the human mouth and improves the in vitro study ...
[72]
[PDF] TheraBite® Jaw Motion Rehabilitation System™ - Atos Medical
The TheraBite® Jaw Motion Rehabilitation System™ is a portable system which provides anatomically correct motion of the jaw. It utilizes repetitive passive ...
[73]
Chewing Gum - an overview | ScienceDirect Topics
In making chewing gum, gum base is melted in a mixer with heating, and then the other ingredients are slowly added and kneaded until the mass reaches to the ...
[74]
Flavor Release and Application in Chewing Gum - ACS Publications
Dec 28, 2022 · This chapter describes the types, quantities, and release characteristics of flavors, their interaction with the gum base, and their use in chewing gum.
[75]
Chewing Gum Market Size, Share, and Innovations to 2034
Aug 26, 2025 · The global chewing gum market size was estimated at USD 28.88 billion in 2024 and is predicted to increase from USD 29.89 billion in 2025 to approximately USD ...Chewing Gum Market Size... · Chewing Gum Market Trends · Market Challenge
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[PDF] Abuse-deterrent Opioid Drug Products | FDA
We are developing a chewing in vitro-in vivo correlation (IVIVC) using the simulated mastication method and physiologically-based pharmacokinetic (PBPK) ...
[77]
An in vitro approach for evaluating the oral abuse deterrence of solid ...
Simulated chewing of Hysingla resulted in initially faster drug release during chewing while subsequent dissolution testing demonstrated that the masticated ...
[78]
Pet Chewing Food Processing Machinery (LT80)
Rating 5.0 · Review by MIC_BUYERUtilizing advanced extrusion technology, our system combines heat, pressure, and mechanical action to transform raw ingredients into premium pet food products.