When considering dental impressions, traditional methods have long been the standard. Orthodontic expanders can create more space in the mouth for teeth Children's braces treatment deciduous teeth. These methods typically involve using impression materials like alginate, polyvinyl siloxane (PVS), or polyether to capture the shapes and structures within a patient's mouth. The process generally starts with the dentist selecting the appropriate tray and material based on the specific needs of the case. The material is then mixed and loaded into the tray, which is subsequently placed in the patient's mouth to capture the impression.
Alginate, one of the most commonly used materials, is favored for its ease of use and cost-effectiveness, especially for preliminary impressions. However, it is not without its drawbacks; alginate impressions can be distorted easily and are not as dimensionally stable as other materials. This means that they may not always provide the precision required for more complex dental work.
PVS and polyether materials offer greater accuracy and stability, making them suitable for final impressions. PVS is particularly popular due to its excellent detail reproduction and flexibility, allowing for more precise captures of the dental structures. Polyether, on the other hand, is known for its superior flow properties, which can be advantageous in capturing detailed impressions of hard-to-reach areas.
Despite their widespread use, traditional impression methods come with several limitations. One of the most significant challenges is the discomfort they can cause patients. The process of having a tray filled with impression material placed in their mouth can be unpleasant, leading to gagging or other forms of discomfort. This can make it difficult to obtain a clear and accurate impression, particularly in patients with a strong gag reflex.
Another limitation is the potential for errors and distortions. Even with careful technique, traditional impressions can be susceptible to bubbles, tears, or other imperfections that can compromise their accuracy. These imperfections can lead to ill-fitting restorations, which may require additional adjustments or even a retake of the impression.
Time is also a factor. The process of mixing, loading, and capturing an impression, followed by the time required for the material to set, can be time-consuming. This not only adds to the chair time for the patient but also increases the workload for the dental team.
Lastly, traditional impressions require physical storage, which can be cumbersome. Dental practices must allocate space for storing impression materials and the resulting physical models, which can become problematic as the practice grows.
In summary, while traditional impression methods have served the dental community well for many years, they are not without their limitations. The discomfort to patients, potential for errors, time consumption, and storage requirements all present challenges that have driven the exploration of more advanced technologies, such as digital scanners, to improve the accuracy and efficiency of dental impressions.
The integration of digital scanners in orthodontics has revolutionized the way dental professionals approach patient care, particularly for pediatric patients. These advanced devices offer numerous benefits that enhance both the patient experience and the accuracy of orthodontic treatments.
Firstly, digital scanners provide a non-invasive and comfortable alternative to traditional impression methods. For children, who may already feel anxious about dental visits, the use of digital scanners can significantly reduce discomfort. Unlike messy and sometimes gag-inducing impression materials, digital scanners use a gentle, wand-like device to capture detailed images of the teeth and oral structures. This process is quick, clean, and generally more pleasant for young patients.
Another significant advantage is the precision and accuracy of digital impressions. Digital scanners capture highly detailed images of the mouth, allowing orthodontists to create more accurate models of the teeth and jaw. This level of detail is crucial for developing effective treatment plans, especially for growing children whose dental structures are constantly changing. Accurate digital impressions ensure that orthodontic appliances, such as braces or aligners, fit perfectly, leading to better outcomes and more efficient treatment processes.
Digital scanners also facilitate better communication between orthodontists and their young patients. The visual nature of digital images allows orthodontists to explain treatment plans more clearly, making it easier for children and their parents to understand the process and expected results. This transparency can help alleviate fears and build trust, making the overall experience more positive for everyone involved.
Furthermore, the use of digital scanners streamlines the workflow in orthodontic practices. Digital impressions can be instantly shared with dental labs, reducing the wait time for custom-made appliances. This efficiency not only speeds up the treatment process but also minimizes the number of visits required, which is particularly beneficial for busy families.
In conclusion, the benefits of using digital scanners in orthodontics, especially for pediatric patients, are manifold. They offer a more comfortable and precise alternative to traditional impressions, enhance patient communication, and streamline the treatment process. As technology continues to advance, the use of digital scanners is likely to become even more integral to providing high-quality orthodontic care for children.
Exploring the various types of digital scanners available for orthodontic use reveals a fascinating landscape of technology designed to enhance the precision and efficiency of dental procedures. These digital scanners have revolutionized the way orthodontists capture impressions, offering a departure from traditional methods that relied on physical molds.
One prominent type is the intraoral scanner, a handheld device that orthodontists use directly inside the patient's mouth. These scanners utilize advanced imaging technology to create highly detailed 3D models of the teeth and surrounding structures. The real-time feedback and immediate visualization offered by intraoral scanners not only improve accuracy but also enhance patient comfort by eliminating the need for messy impression materials.
Another type is the desktop scanner, which involves taking a physical impression of the teeth using conventional materials and then scanning this impression on a specialized scanner. While this method still incorporates traditional impression-taking, the subsequent digital scanning process allows for the creation of precise 3D models. Desktop scanners are known for their high resolution and are often used in conjunction with CAD/CAM systems for designing and fabricating orthodontic appliances.
Extraoral scanners represent yet another category, focusing on scanning physical models or casts that have been created from traditional impressions. These scanners are typically used in laboratory settings and provide a bridge between traditional and digital workflows. They allow orthodontists to maintain some aspects of conventional practices while benefiting from the advantages of digital technology.
In addition to these primary types, there are hybrid systems that combine elements of both intraoral and desktop scanning. These systems aim to offer the best of both worlds, allowing orthodontists to choose the most suitable approach based on the specific needs of each case.
The evolution of digital scanners in orthodontics signifies a shift towards more patient-centric and efficient practices. As technology continues to advance, these scanners will likely become even more integral to the field, contributing to enhanced diagnostic capabilities, treatment planning, and overall patient satisfaction.
Exploring Digital Scanners for Accurate Impressions: A Step-by-Step Guide
Digital scanners have revolutionized the way professionals capture impressions, providing unparalleled accuracy and efficiency. Whether you're in dentistry, engineering, or any field requiring precise measurements, mastering the use of digital scanners can significantly enhance your workflow. Here's a straightforward guide to help you get started.
Understand the Basics
Before diving in, it's crucial to understand what digital scanners are and how they work. Digital scanners use light and sensors to capture detailed images of an object's surface. These images are then converted into a digital 3D model, which can be used for various applications.
Choose the Right Scanner
Selecting the appropriate scanner is vital. Consider the type of impressions you need to capture and the level of detail required. Intraoral scanners are popular in dentistry for capturing dental impressions, while handheld scanners are versatile for various applications.
Prepare the Object
Ensure the object you're scanning is clean and free from any debris. This step is crucial as any dirt or damage can affect the accuracy of the scan. For dental applications, make sure the patient's mouth is clean and dry.
Calibrate the Scanner
Most digital scanners require calibration before use. Follow the manufacturer's instructions to ensure the scanner is properly calibrated. This step ensures that the scanner provides accurate measurements.
Position the Scanner
Position the scanner correctly to capture the best possible image. For handheld scanners, hold the device steady and move it slowly over the object. For intraoral scanners, ensure the wand is positioned correctly inside the patient's mouth.
Capture the Scan
Begin the scanning process. For handheld scanners, move the device in a consistent motion to capture the entire surface. Intraoral scanners typically require you to move the wand systematically around the teeth. Ensure you cover all areas to get a complete impression.
Review the Scan
Once the scan is complete, review the digital model on your computer. Check for any gaps or errors in the scan. If necessary, retake the scan to ensure accuracy.
Post-Processing
Use software to refine the digital model. This may involve cleaning up the model, filling in any gaps, or making adjustments to ensure the model is accurate and ready for use.
Save and Share
Save the digital model in the appropriate format for your needs. Whether you're sending it to a lab for further processing or using it for design purposes, ensure the file is correctly formatted and shared securely.
Practice and Refine
Like any skill, using a digital scanner improves with practice. Take the time to refine your technique and explore the scanner's capabilities. The more familiar you become with the process, the more efficient and accurate your scans will be.
By following these steps, you can effectively use digital scanners to capture accurate impressions, enhancing your professional practice and ensuring precision in your work.
When exploring the realm of digital scanners versus traditional methods for obtaining accurate impressions, it's crucial to consider both efficiency and accuracy. Digital scanners have emerged as a game-changing technology in various fields, including dentistry, engineering, and quality control. They offer a range of advantages over traditional methods, making them increasingly popular.
First and foremost, digital scanners are renowned for their efficiency. Unlike traditional methods that often involve physical molds, plaster, or manual measurements, digital scanners can capture detailed 3D images in a fraction of the time. This not only speeds up the process but also reduces the margin for human error. In a clinical setting, for instance, a dentist can quickly scan a patient's teeth and gums, eliminating the discomfort associated with traditional impression materials.
Accuracy is another domain where digital scanners excel. These devices utilize advanced technologies like laser scanning, structured light, or even ultrasound to capture intricate details with exceptional precision. The resulting digital impressions are often more accurate than those obtained through traditional means. This heightened accuracy is particularly crucial in fields like prosthetics, where even minor discrepancies can lead to discomfort or malfunction.
Furthermore, digital scanners offer the advantage of easy data management and sharing. The digital impressions can be stored, analyzed, and shared electronically, facilitating collaboration among professionals and ensuring that critical data is readily accessible. This feature is invaluable in interdisciplinary projects where multiple experts need to review and contribute to the design process.
In conclusion, the comparison of digital scanners versus traditional methods in terms of efficiency and accuracy reveals a clear preference for digital technology. Digital scanners not only expedite the impression-taking process but also deliver highly accurate results, making them a valuable tool in various industries. As technology continues to advance, we can expect digital scanners to play an even more pivotal role in ensuring precision and efficiency in impression-taking and beyond.
When it comes to patient comfort and experience, digital scanners have revolutionized the way dental impressions are taken. Traditionally, taking impressions involved using messy and uncomfortable materials like alginate or silicone, which many patients found unpleasant. The process could be gag-inducing and time-consuming, often requiring multiple attempts to get right.
With digital scanners, the experience is entirely different. Patients appreciate the cleanliness and precision of the process. Digital scanners use a wand-like device that is moved over the teeth and gums to capture detailed images. This method is not only faster but also more comfortable for patients. There's no messy material to deal with, and the risk of gagging is significantly reduced.
Moreover, the real-time feedback provided by digital scanners allows dentists to ensure accuracy on the spot. Patients can see the digital images of their teeth, which helps them understand the treatment process better. This transparency fosters a sense of trust and collaboration between the patient and the dentist.
Another significant advantage is the reduced chair time. Digital scanning is quicker than traditional methods, meaning patients spend less time in the dental chair. This efficiency is particularly beneficial for those with busy schedules or anxiety about dental visits.
In summary, digital scanners enhance patient comfort and experience by offering a cleaner, faster, and more engaging way to take dental impressions. This technological advancement not only improves patient satisfaction but also contributes to more accurate and efficient dental care.
In the ever-evolving field of orthodontics, digital scanning technology has made significant strides, transforming the way dental professionals capture and analyze patient data. As we look to the future, several trends and advancements promise to enhance the precision, efficiency, and patient experience in orthodontic treatments.
One of the most exciting developments on the horizon is the integration of artificial intelligence (AI) with digital scanning technology. AI algorithms can analyze scans to predict treatment outcomes more accurately, suggesting optimal treatment plans tailored to each patient's unique dental anatomy. This not only improves the efficacy of orthodontic interventions but also reduces the time patients spend in treatment.
Another trend is the miniaturization and increased portability of digital scanners. As technology shrinks, so do the devices that house it. Future digital scanners are expected to become more compact, making them easier to use in various clinical settings and even in remote or underserved areas. This portability will enable more widespread access to high-quality orthodontic care.
Enhanced connectivity is also a key future trend. Digital scanners will increasingly be connected to cloud-based platforms, allowing for real-time data sharing among dental professionals. This connectivity facilitates collaborative care, enabling orthodontists, dentists, and even patients to access and review scans from anywhere, at any time. It fosters a more integrated approach to dental health management.
Moreover, the resolution and accuracy of digital scans are continuously improving. Future advancements will likely offer even more detailed imaging, allowing for the detection of subtle dental irregularities that might be missed by traditional methods. This heightened precision will lead to more effective and customized orthodontic solutions.
Lastly, patient-centric innovations are on the rise. Future digital scanners may incorporate features that make the scanning process more comfortable and less intimidating for patients. For instance, quicker scan times and the elimination of uncomfortable physical impressions will enhance the overall patient experience, making visits to the orthodontist less daunting.
In conclusion, the future of digital scanning technology in orthodontics is bright, with numerous advancements on the horizon that promise to make treatments more precise, efficient, and patient-friendly. As these technologies continue to evolve, they will undoubtedly play a crucial role in shaping the future of orthodontic care.
Thumb sucking is a behavior found in humans, chimpanzees, captive ring-tailed lemurs,[1] and other primates.[2] It usually involves placing the thumb into the mouth and rhythmically repeating sucking contact for a prolonged duration. It can also be accomplished with any organ within reach (such as other fingers and toes) and is considered to be soothing and therapeutic for the person. As a child develops the habit, it will usually develop a "favourite" finger to suck on.
At birth, a baby will reflexively suck any object placed in its mouth; this is the sucking reflex responsible for breastfeeding. From the first time they engage in nutritive feeding, infants learn that the habit can not only provide valuable nourishment, but also a great deal of pleasure, comfort, and warmth. Whether from a mother, bottle, or pacifier, this behavior, over time, begins to become associated with a very strong, self-soothing, and pleasurable oral sensation. As the child grows older, and is eventually weaned off the nutritional sucking, they can either develop alternative means for receiving those same feelings of physical and emotional fulfillment, or they can continue experiencing those pleasantly soothing experiences by beginning to suck their thumbs or fingers.[3] This reflex disappears at about 4 months of age; thumb sucking is not purely an instinctive behavior and therefore can last much longer.[4] Moreover, ultrasound scans have revealed that thumb sucking can start before birth, as early as 15 weeks from conception; whether this behavior is voluntary or due to random movements of the fetus in the womb is not conclusively known.
Thumb sucking generally stops by the age of 4 years. Some older children will retain the habit, which can cause severe dental problems.[5] While most dentists would recommend breaking the habit as early as possible, it has been shown that as long as the habit is broken before the onset of permanent teeth, at around 5 years old, the damage is reversible.[6] Thumb sucking is sometimes retained into adulthood and may be due to simply habit continuation. Using anatomical and neurophysiological data a study has found that sucking the thumb is said to stimulate receptors within the brain which cause the release of mental and physical tension.[7]
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Percentage of children who suck their thumbs (data from two researchers)
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Most children stop sucking on thumbs, pacifiers or other objects on their own between 2 and 4 years of age. No harm is done to their teeth or jaws until permanent teeth start to erupt. The only time it might cause concern is if it goes on beyond 6 to 8 years of age. At this time, it may affect the shape of the oral cavity or dentition.[9] During thumbsucking the tongue sits in a lowered position and so no longer balances the forces from the buccal group of musculature. This results in narrowing of the upper arch and a posterior crossbite. Thumbsucking can also cause the maxillary central incisors to tip labially and the mandibular incisors to tip lingually, resulting in an increased overjet and anterior open bite malocclusion, as the thumb rests on them during the course of sucking. In addition to proclination of the maxillary incisors, mandibular incisors retrusion will also happen. Transverse maxillary deficiency gives rise to posterior crossbite, ultimately leading to a Class II malocclusion.[10]
Children may experience difficulty in swallowing and speech patterns due to the adverse changes. Aside from the damaging physical aspects of thumb sucking, there are also additional risks, which unfortunately, are present at all ages. These include increased risk of infection from communicable diseases, due to the simple fact that non-sterile thumbs are covered with infectious agents, as well as many social implications. Some children experience social difficulties, as often children are taunted by their peers for engaging in what they can consider to be an “immature” habit. This taunting often results the child being rejected by the group or being subjected to ridicule by their peers, which can cause understandable psychological stress.[11]
Methods to stop sucking habits are divided into 2 categories: Preventive Therapy and Appliance Therapy.[10]
Examples to prevent their children from sucking their thumbs include the use of bitterants or piquant substances on their child's hands—although this is not a procedure encouraged by the American Dental Association[9] or the Association of Pediatric Dentists. Some suggest that positive reinforcements or calendar rewards be given to encourage the child to stop sucking their thumb.
The American Dental Association recommends:
The British Orthodontic Society recommends the same advice as ADA.[13]
A Cochrane review was conducted to review the effectiveness of a variety of clinical interventions for stopping thumb-sucking. The study showed that orthodontic appliances and psychological interventions (positive and negative reinforcement) were successful at preventing thumb sucking in both the short and long term, compared to no treatment.[14] Psychological interventions such as habit reversal training and decoupling have also proven useful in body focused repetitive behaviors.[15]
Clinical studies have shown that appliances such as TGuards can be 90% effective in breaking the thumb or finger sucking habit. Rather than use bitterants or piquants, which are not endorsed by the ADA due to their causing of discomfort or pain, TGuards break the habit simply by removing the suction responsible for generating the feelings of comfort and nurture.[16] Other appliances are available, such as fabric thumb guards, each having their own benefits and features depending on the child's age, willpower and motivation. Fixed intraoral appliances have been known to create problems during eating as children when removing their appliances may have a risk of breaking them. Children with mental illness may have reduced compliance.[10]
Some studies mention the use of extra-oral habit reminder appliance to treat thumb sucking. An alarm is triggered when the child tries to suck the thumb to stop the child from this habit.[10][17] However, more studies are required to prove the effectiveness of external devices on thumb sucking.
| Crossbite | |
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| Unilateral posterior crossbite | |
| Specialty | Orthodontics |
In dentistry, crossbite is a form of malocclusion where a tooth (or teeth) has a more buccal or lingual position (that is, the tooth is either closer to the cheek or to the tongue) than its corresponding antagonist tooth in the upper or lower dental arch. In other words, crossbite is a lateral misalignment of the dental arches.[1][2]
An anterior crossbite can be referred as negative overjet, and is typical of class III skeletal relations (prognathism).
An anterior crossbite in a child with baby teeth or mixed dentition may happen due to either dental misalignment or skeletal misalignment. Dental causes may be due to displacement of one or two teeth, where skeletal causes involve either mandibular hyperplasia, maxillary hypoplasia or combination of both.
An anterior crossbite due to dental component involves displacement of either maxillary central or lateral incisors lingual to their original erupting positions. This may happen due to delayed eruption of the primary teeth leading to permanent teeth moving lingual to their primary predecessors. This will lead to anterior crossbite where upon biting, upper teeth are behind the lower front teeth and may involve few or all frontal incisors. In this type of crossbite, the maxillary and mandibular proportions are normal to each other and to the cranial base. Another reason that may lead to a dental crossbite is crowding in the maxillary arch. Permanent teeth will tend to erupt lingual to the primary teeth in presence of crowding. Side-effects caused by dental crossbite can be increased recession on the buccal of lower incisors and higher chance of inflammation in the same area. Another term for an anterior crossbite due to dental interferences is Pseudo Class III Crossbite or Malocclusion.
Single tooth crossbites can occur due to uneruption of a primary teeth in a timely manner which causes permanent tooth to erupt in a different eruption pattern which is lingual to the primary tooth.[3] Single tooth crossbites are often fixed by using a finger-spring based appliances.[4][5] This type of spring can be attached to a removable appliance which is used by patient every day to correct the tooth position.
An anterior crossbite due to skeletal reasons will involve a deficient maxilla and a more hyperplastic or overgrown mandible. People with this type of crossbite will have dental compensation which involves proclined maxillary incisors and retroclined mandibular incisors. A proper diagnosis can be made by having a person bite into their centric relation will show mandibular incisors ahead of the maxillary incisors, which will show the skeletal discrepancy between the two jaws.[6]
Bjork defined posterior crossbite as a malocclusion where the buccal cusps of canine, premolar and molar of upper teeth occlude lingually to the buccal cusps of canine, premolar and molar of lower teeth.[7] Posterior crossbite is often correlated to a narrow maxilla and upper dental arch. A posterior crossbite can be unilateral, bilateral, single-tooth or entire segment crossbite. Posterior crossbite has been reported to occur between 7–23% of the population.[8][9] The most common type of posterior crossbite to occur is the unilateral crossbite which occurs in 80% to 97% of the posterior crossbite cases.[10][3] Posterior crossbites also occur most commonly in primary and mixed dentition. This type of crossbite usually presents with a functional shift of the mandible towards the side of the crossbite. Posterior crossbite can occur due to either skeletal, dental or functional abnormalities. One of the common reasons for development of posterior crossbite is the size difference between maxilla and mandible, where maxilla is smaller than mandible.[11] Posterior crossbite can result due to
Unilateral crossbite involves one side of the arch. The most common cause of unilateral crossbite is a narrow maxillary dental arch. This can happen due to habits such as digit sucking, prolonged use of pacifier or upper airway obstruction. Due to the discrepancy between the maxillary and mandibular arch, neuromuscular guidance of the mandible causes mandible to shift towards the side of the crossbite.[14] This is also known as Functional mandibular shift. This shift can become structural if left untreated for a long time during growth, leading to skeletal asymmetries. Unilateral crossbites can present with following features in a child
A child with posterior crossbite should be treated immediately if the child shifts their mandible on closing, which is often seen in a unilateral crossbite as mentioned above. The best age to treat a child with crossbite is in their mixed dentition when their palatal sutures have not fused to each other. Palatal expansion allows more space in an arch to relieve crowding and correct posterior crossbite. The correction can include any type of palatal expanders that will expand the palate which resolves the narrow constriction of the maxilla.[9] There are several therapies that can be used to correct a posterior crossbite: braces, 'Z' spring or cantilever spring, quad helix, removable plates, clear aligner therapy, or a Delaire mask. The correct therapy should be decided by the orthodontist depending on the type and severity of the crossbite.
One of the keys in diagnosing the anterior crossbite due to skeletal vs dental causes is diagnosing a CR-CO shift in a patient. An adolescent presenting with anterior crossbite may be positioning their mandible forward into centric occlusion (CO) due to the dental interferences. Thus finding their occlusion in centric relation (CR) is key in diagnosis. For anterior crossbite, if their CO matches their CR then the patient truly has a skeletal component to their crossbite. If the CR shows a less severe class 3 malocclusion or teeth not in anterior crossbite, this may mean that their anterior crossbite results due to dental interferences.[17]
Goal to treat unilateral crossbites should definitely include removal of occlusal interferences and elimination of the functional shift. Treating posterior crossbites early may help prevent the occurrence of Temporomandibular joint pathology.[18]
Unilateral crossbites can also be diagnosed and treated properly by using a Deprogramming splint. This splint has flat occlusal surface which causes the muscles to deprogram themselves and establish new sensory engrams. When the splint is removed, a proper centric relation bite can be diagnosed from the bite.[19]
Literature states that very few crossbites tend to self-correct which often justify the treatment approach of correcting these bites as early as possible.[9] Only 0–9% of crossbites self-correct. Lindner et al. reported that 50% of crossbites were corrected in 76 four-year-old children.[20]
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The jaws are a pair of opposable articulated structures at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of humans and most animals.
In arthropods, the jaws are chitinous and oppose laterally, and may consist of mandibles or chelicerae. These jaws are often composed of numerous mouthparts. Their function is fundamentally for food acquisition, conveyance to the mouth, and/or initial processing (mastication or chewing). Many mouthparts and associate structures (such as pedipalps) are modified legs.
In most vertebrates, the jaws are bony or cartilaginous and oppose vertically, comprising an upper jaw and a lower jaw. The vertebrate jaw is derived from the most anterior two pharyngeal arches supporting the gills, and usually bears numerous teeth.
The vertebrate jaw probably originally evolved in the Silurian period and appeared in the Placoderm fish which further diversified in the Devonian. The two most anterior pharyngeal arches are thought to have become the jaw itself and the hyoid arch, respectively. The hyoid system suspends the jaw from the braincase of the skull, permitting great mobility of the jaws. While there is no fossil evidence directly to support this theory, it makes sense in light of the numbers of pharyngeal arches that are visible in extant jawed vertebrates (the Gnathostomes), which have seven arches, and primitive jawless vertebrates (the Agnatha), which have nine.
The original selective advantage offered by the jaw may not be related to feeding, but rather to increased respiration efficiency.[1] The jaws were used in the buccal pump (observable in modern fish and amphibians) that pumps water across the gills of fish or air into the lungs in the case of amphibians. Over evolutionary time the more familiar use of jaws (to humans), in feeding, was selected for and became a very important function in vertebrates. Many teleost fish have substantially modified jaws for suction feeding and jaw protrusion, resulting in highly complex jaws with dozens of bones involved.[2]
The jaw in tetrapods is substantially simplified compared to fish. Most of the upper jaw bones (premaxilla, maxilla, jugal, quadratojugal, and quadrate) have been fused to the braincase, while the lower jaw bones (dentary, splenial, angular, surangular, and articular) have been fused together into a unit called the mandible. The jaw articulates via a hinge joint between the quadrate and articular. The jaws of tetrapods exhibit varying degrees of mobility between jaw bones. Some species have jaw bones completely fused, while others may have joints allowing for mobility of the dentary, quadrate, or maxilla. The snake skull shows the greatest degree of cranial kinesis, which allows the snake to swallow large prey items.
In mammals, the jaws are made up of the mandible (lower jaw) and the maxilla (upper jaw). In the ape, there is a reinforcement to the lower jaw bone called the simian shelf. In the evolution of the mammalian jaw, two of the bones of the jaw structure (the articular bone of the lower jaw, and quadrate) were reduced in size and incorporated into the ear, while many others have been fused together.[3] As a result, mammals show little or no cranial kinesis, and the mandible is attached to the temporal bone by the temporomandibular joints. Temporomandibular joint dysfunction is a common disorder of these joints, characterized by pain, clicking and limitation of mandibular movement.[4] Especially in the therian mammal, the premaxilla that constituted the anterior tip of the upper jaw in reptiles has reduced in size; and most of the mesenchyme at the ancestral upper jaw tip has become a protruded mammalian nose.[5]
Sea urchins possess unique jaws which display five-part symmetry, termed the Aristotle's lantern. Each unit of the jaw holds a single, perpetually growing tooth composed of crystalline calcium carbonate.
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Media related to Jaw bones at Wikimedia Commons
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