Home

Periapical x ray vs panoramic x ray

Panoramic x-rays give your dentist a general comprehensive view of your entire mouth on a single film, while bitewing or periapical x-rays show a detailed image of a smaller area, revealing decay or cavities between teeth. If your dentist needs both these vantage points to assess a problem, he or she will likely conduct multiple x-rays Panoramic x-rays are used in orthodontic treatment planning, such as braces, and when planning extractions, including wisdom teeth removal. Periapical X-Rays. Periapical x-rays take a close look at just a few teeth at a time. Unlike bitewing x-rays, periapical x-rays look at the entire tooth, from crown to root Patients have a panoramic X-ray taken for an initial evaluation, followed by a series of close-up views of all sections of the teeth, called periapical X-rays. A periapical X-ray gives a close and in-depth look at a particular tooth. A full-mouth series consists of a group of periapical X-rays taken of all the patient's teeth Panoramic x-rays are like panoramic photos. They show the entire mouth instead of just a snapshot of a few teeth. Unlike other dental x-rays, these images are taken from outside the mouth instead of inside. The patient stays still while an x-ray machine moves in an arc from one side of their head all the way around to the other Chest X-ray 0.100000 Full mouth series f-speed film* 0.171000 Full mouth series digital 0.090000 Cross-country flight (New York to Los Angeles) 0.040000 4 bitewings f-speed film* 0.038000 4 bitewings digital 0.020000 Panoramic film 0.0142-0.0243 Panoramic digital 0.0047-0.0149 1 periapical f-speed film* 0.00950

All about x-rays - Delta Denta

Preoperative panoramic radiograph with radiopacity

Taking the X-Factor Out of Dental X-Rays Greensboro NC

  1. Periapical X-rays show the whole tooth — from the crown, to beyond the root where the tooth attaches into the jaw. Each periapical X-ray shows all teeth in one portion of either the upper or lower jaw. Periapical X-rays detect any unusual changes in the root and surrounding bone structures
  2. The total amount of radiation for this set is 0.008 mSv. If a child has one or more adult teeth then a panoramic x-ray is indicated in addition to the bitewing and periapical x-rays. The amount of radiation exposure in a single panoramic x-ray is 0.007 mSV
  3. A panoramic bitewing study may cut radiation dose by 40% in comparison with intraoral, bitewing X-ray studies. A digital pan bitewing may create as little as three to five microsieverts vs. eight to 20 or more for intraoral bitewings, depending on cone length, machine, and sensor type
  4. When panoramic radiographs are used to replace full-mouth radiographic series for the pediatric patient, certain advantages and disadvantages of this technique should be understood. The panoramic exposure offers ease of operation, shorter working time, and greater coverage than does the intraoral fu

Routine Dental Panoramic X-Rays Not Necessary, Study Shows

Types of Dental X-Rays and Why You Need Them - Dental

Most periapical and bitewing X-rays cover only 2 to 3 teeth, therefore you need about a dozen X-rays to capture the whole mouth. Typically, most dentists take 10 to 20 periapical and bitewing X-rays on your initial visit, followed by 4 to 8 X-rays on future recall appointments. Panoramic radiograph (Panorex Periapical x-rays are more commonly known as PA's. These dental x-rays focus on 1-2 teeth up close. If you are experiencing a toothache or if there is a suspicious looking area on one of your teeth, we would take a PA to get a better idea of what is going on. With these x-rays we are also able to see the root structure of the tooth as well Periapical x-rays are the ones that are usually done, but the panoramic type reveals the condition of all teeth so it is also an option. Other uses include looking at the position of third molars, the presence of dental cysts, the position od of the maxillary sinus, bone abnormalities, fractures, and a number of other conditions

The most prescribed dental x-rays are: Bite-wing x-rays which focus on the upper and lower back teeth and check for decay between teeth, Periapical x-rays which show the entire length of a tooth from crown to root and is used to look at the health of the bone that supports the teeth and to detect abscesses, cysts, tumors and impacted teeth Panoramic x-ray » Periapical x-ray is a type of x-ray that shows one to two teeth from their crown to their root and the surrounding bone. It is a very commonly used diagnostic measure. This type of x-ray can be used for any tooth in the mouth and it is mostly used to determine the depth of the decay and if the tooth needs endodontic therapy. A panoramic radiograph resulted in an effective dose of 4.1 µSv, while a periapical radiograph resulted in an effective dose of 0.6 µSv and 0.7 µSv using a maxillary lateral projection and central maxillary incisor projection respectively Two hundred panoramic radiographs were exposed with the rotational technique and 200 with the intraoral X-ray tube technique. Periapical osteolytic and sclerotic lesions as well as approximal caries were recorded independently by two observes

Periapical X-ray showing the whole tooth structure . Periapical x-rays show the whole tooth, but only a few teeth are captured here. The panoramic x-ray shows all of the teeth in one x-ray. The detail in a panoramic x-ray is not as clear as a bitewing or periapical but is great for showing development, lesions and as an overall health screen This is a minimum of 10 total x-rays, including both bitewings and periapical dental x-rays. Panoramic Dental X-rays. The dental x-rays you see below are called panoramic x-rays. This kind is usually taken ever 3-5 years to screen for possible bone cysts, tumors, sinus abnormalities, etc

Disadvantages Of The Panorami

  1. The X-ray will also reveal deep cavities and gum disease, but it is not as precise as bitewing or periapical X-rays. The panoramic X-ray has many other applications, including evaluating patients with past or present TMJ or jaw joint problems; those who require full or partial removable dentures, dental implants, or braces; those who are at.
  2. > Panoramic/ Periapical X-rays. Panoramic/ Periapical X-rays. Panoramic X-Ray. Peri-apical Xrays. Any questions? Let us know. Your name. Your email. Subject. Your message (optional) Recent News. A few tips on how to keep your teeth and smile as healthy as possible; The history of dental implants - and where they are heading
  3. Periapical X-rays also show the entire tooth to the end of the root and the supporting bone, which is invaluable for detecting problems below the gum line or in the jaw. The report states that routine panoramic x-rays may be completely unnecessary and should be done on an individual basis. Based on our study, the panoramic X-ray has limited value
  4. (5) periapical x-rays; (6) panoramic x-rays, limited to one every five years except (1) when medically necessary for the diagnosis and follow-up of oral and maxillofacial pathology and trauma or (2) once every two years for patients who cannot cooperate for intraoral film due to a developmental disability or medical condition that does no

The results showed that patients received 82% less radiation with the panoramic survey than with the periapical type. 1. D.C. Hudson, J.W. Kumpula, G. Dickson, A panoramic x-ray dental machine US Armed Forces Med J 8: (Jan 1957) 46- 2. T.M. Graber, Panoramic radiography in dentistry J Can Dent Assoc 31: (March 1965) 158- 3 A panoramic X-ray will focus primarily on the jaw, capturing images of the full upper and lower dental arches including the jawbones and surrounding facial structures. A cephalometric X-ray uses a specially adapted film holder mounted on a mechanical arm to capture images of your entire oral structure, including the nasal and sinus passageways. Panoramic X-Rays: Panoramic X-Rays are the machines that rotate around the head and shows the complete tooth structure of the upper and lower arch of teeth . They are mostly used before the implant is done or sometimes may be used to diagnose the bony tumor or the cysts inside the mouth or teeth

Intra-oral x-rays are small x-rays sometimes called pericipal x-rays. It is commonly taken during root canal treatment or when your dentist requires a zoom in view of a specific area. The X-mind intraoral x-ray machines from Aceton is famous for being bullet proof. It is an intraoral unit that provides simple and fast slide x-rays What You Can Expect: The Radiograph Dental X-ray Process. The radiography process is relatively simple for both periapical and bitewing radiographs. Below is a list of steps taken to ensure comfort and safety. Patients will sit upright in a dental chair Enhance: Periapical X-Rays And Bitewing X-Rays. In photography, wide shots show a lot, but they aren't as useful for details as a closeup. The same is true in X-rays, which is why we don't rely only on the panoramic image. The next level of dental X-rays are the bitewing X-rays. These intraoral (inside the mouth) X-rays focus on a specific.

A 2D x-ray is an x-ray examination that captures images of the mouth. This includes the teeth, upper and lower jaws, and surrounding structures and tissues. These types of x-rays can range from simple intraoral to extraoral full mouth x-rays. Intraoral x-ray; Intraoral x-rays require preparation by placing a film inside your mouth Panoramic x-rays in Edmonton are digital images of your teeth, soft tissues, and bones. This type of x-ray technology helps your dentist assess your oral health overall. Periapical or bitewing x-rays are close-up pictures. Panoramic images display a broader view. They allow you and your dentist to see your teeth, jaws, sinuses, nasal area, and. Dent Ally, best dental clinic in Delhi, is one of the very few clinics in Delhi which has a panoramic X-ray machine (OPG). o Periapical This type of X-ray is done to primarily focus on two full teeth right from their root to the crown Among medical uses, dental x-rays expose the patient to less radiation than almost any x-ray that can be taken. According to the American Dental Association, a bitewing and periapical x-ray both deliver .005 millisieverts of radiation, whereas a panoramic x-ray delivers .01 millisieverts. For comparison, an x-ray of the upper G.I. tract.

What Is A Panoramic Dental X-Ray? - Colgat

A periapical X-ray is similar to a bite wing X-ray but it shows the entire length of one or two teeth, from the crown to the root. Your dentist may also take a panoramic X-ray every few years (or when a problem presents itself) to give him/her a view of all the teeth on both the upper and lower jaws Outside of a comprehensive examination, periapical images are used if you are suffering from acute pain that has yet to be diagnosed, or in cases where prior surgery or other dental work needs to be re-evaluated for success or failure. Yet another X-ray option is a panoramic X-ray, which captures a 360° view of the entire skull Radiation from Panoramic Dental X-Rays. A panoramic or panorex dental x-ray exposes the patient to anywhere from 9 to 26 micro sieverts of radiation. If you went in to your dentist for a visit and they took four routine dental x-rays along with a panoramic x-ray, you would end up getting about 50-60 micro sieverts of radiation, or the.

Booking treatment Rontgen Panoramic X-ray 1x di Primera Dental online. Dapatkan harga & diskon terbaru 2021 dari klinik gigi rekanan HDmall! ️ Harga Terbaik ️ Cicilan ️ GRATIS konsultasi. Cek di sini Types of X-ray images: (a) Bitewing X-ray; (b) Periapical X-ray; (c) Panoramic X-ray. rays. Figure 1 illustrates examples of these X-ray image types. Particularly, panoramic X-ray is a useful exam to complement the clinical examination in the diagnosis of dental diseases (caries or endodontic diseases). This type of examination al Panoramic X-rays are often associated with diagnosing wisdom tooth issues, orthodontic consultations, implant and oral surgery consultations, or may be recommended by the dentist if there is an issue preventing a standard bitewing or periapical x-ray. Our x-ray equipment is fully digital at all 1st Family Dental locations, which means that any. PAX-PeriApical X-ray (same with A) Panoramic X-ray Cephalometric X-ray. What is Shorting the instrument? An incorrect technique where you always pass the instrument holding it by the end. Polishing Agents (there are 4) 1. Prophy Paste 2. Fine Pumice 3.Commercial premixed 4. Fluoride Paste Periapical X-rays. Periapical x-rays are one of the most recommended and used x-rays in the field of dentistry. They are the basics in the field of dental radiographs and are used to a great extent in several branches of dentistry in order to ensure that the procedures are done well and the teeth are not harmed in any form

Radiation doses in dental radiology - FAQs for health

  1. Panoramic x-ray equipment, on the other hand, produces high-resolution 2D images of the entire tooth without the use of an intraoral sensor or equivalent. Like periapical x-ray images, panoramic x-ray images include the apex or tip of the root of the tooth as well as the area of the surrounding bone tissue
  2. Periapical x-rays. Each Periapical X-ray shows this full tooth dimension and includes all the tooth structure (including crown, roots and surrounding bone structures) in either the upper or lower jaw. Periapical X-rays are used to detect any abnormalities of the root structure and surrounding bone structure. They are also typically used.
  3. Dental X-rays are recommended every one to two years for children and every 1.5 to three years for teens. Children often require more X-rays than adults because of their developing teeth and jaws.
  4. What is periapical radiograph? Periapical X-rays show the whole tooth — from the crown, to beyond the root where the tooth attaches into the jaw. Each periapical X-ray shows all teeth in one portion of either the upper or lower jaw. Periapical X-rays detect any unusual changes in the root and surrounding bone structures
  5. a. Bitewing X-ray, showing the back of the upper and lower teeth and how the teeth contact to each other in a single view. b. Periapical X-Ray, showing the whole picture of the tooth (covering several teeth from crown to root tip) to the surrounding jaw bone. c. Panoramic X-Ray, shows a view of the entire teeth, upper and lower jaw and the sinuses
  6. A periapical x-ray is one that captures the whole tooth. It shows everything from the crown (chewing surface) to the root (below the gum line). Each periapical x-ray shows a small section of your upper or lower teeth. These x-rays are often used to detect any unusual changes in the root and surrounding bone structures
  7. A periapical x-ray or PA film will show one or two teeth in their entirety in one single image, right from the crown of the tooth which is the part exposed in the mouth to the very tips of the tooth roots located in the jawbone, as well as the surrounding bone supporting this tooth

What is a periapical xray

Possibly: A panoramic x-ray is a good screening tool for tmd and is usually the first x-ray taken. However, a panoramic x-ray will only reveal tmd if there is bony involvement of the tmj, such as various forms of arthritis, like rheumatoid, psoriatic or osteoarthritis (also known as degenerative joint disease). A panoramic x-ray will not show any soft tissue problems, such as a displaced disc. Panoramic dental X-rays differ somewhat from the types of X-rays patients are most familiar. First off, there's the technology; when you receive a panoramic X-ray, your head will be steadied with the use of a chin rest. Depending on the type of panoramic X-ray being performed, a bitewing or bite plate (bite blocker) may be used

X-Ray Type: Panoramic Radiography. Panoramic radiography, also called panoramic radiograph, is a two-dimensional dental x-ray examination that captures the entire mouth in a single image, including the teeth, upper and lower jaws, surrounding structures, and tissue. Frequency needed: Every three to five years or dependent upon patient need Dental x-rays. Dental x-rays are a type of image of the teeth and mouth. X-rays are a form of high energy electromagnetic radiation. The x-rays penetrate the body to form an image on film or screen. X-rays can be either digital or developed on a film. Structures that are dense (such as silver fillings or metal restoration) will block most of. Products. Gendex Expert DC Periapical X-ray. Gendex, with its legacy of providing quality radiographic systems, offers the expert DC. This direct current powerhouse, in contrast to AC units, delivers strong benefits for your practice: shorter exposures, reduced radiation, and truly consistent image quality. Its industry-leading focal spot of 0.

Dental abscess - Investigations | BMJ Best Practice

The Extraoral X-rays was further studied across CBCT and Panoramic. The Intraoral X-rays was further studied across Bitewing, Occlusal, and Periapical. GLOBAL DENTAL X-RAY MARKET SIZE, BY PERIAPICAL, BY GEOGRAPHY, 2020 VS 2026 (USD MILLION) FIGURE 35. GLOBAL DENTAL X-RAY MARKET SIZE, BY PRODUCT , 2020 VS 2026 (% Periapical X-ray. A periapical X-ray typically shows the complete tooth structure, including crown and complete root of one to two teeth. We will often abbreviate this X-ray as a PA. It is common to have this X-ray taken if you are having a toothache or if dental infection is suspected. Panoramic X-ray A periapical X-Ray is also very good for detecting any problems associated with the tooth root. This X-Rays are not taken on a yearly basis and are only taken to address specific problems. Once children have the eruption of their permanent molars (usually around 6 years of age) we will take a Panorex, or panoramic x-ray 1. Panoramic X-rays. Panoramic helps the doctor in locating the fully emerged as well as emerging teeth, identifying the impacted teeth, and useful for tumors diagnose. On a single X-ray, the panoramic X-rays will help the doctor to see the entire patient's mouth area, the entire teeth in both the upper and lower jaws. 2

The amount of radiation needed to expose a panoramic x-ray film is about the same as the radiation needed to expose two intraoral films (periapical or bitewing). The reason for this is that the film cassette contains an intensifying screen which fluoresces upon exposure to x-rays and exposes the film with visible light as well as x-rays Extraoral X-Rays. Panoramic X-rays. The Panoramic X-rays help the dentist have a good look at all of the patient's teeth in one single x-ray. Panoramic x-rays are used to spot the position of fully developed teeth as well as developing teeth, can help detect impacted teeth, and aids in diagnosis of tumors 4 Periapical X-ray. This technique focuses on two complete teeth, from root to crown. This type of X-ray takes a full tooth picture from the very top of the tooth crown to the very tip of the root. Periapical X-rays are taken when you have symptoms with a specific tooth or a follow-up to a procedure

Dental X-rays - Cleveland Clini

  1. Panoramic X-Rays. Panoramic X-rays are important if dentists need to be provided with a 2D radiograph of the entire mouth including the upper and lower jaws, surrounding structures and mouth tissues. A panoramic x-ray provides a single and flat image of the entire jaw
  2. Periapical (PA) A periapical (PA)X-ray refers to a single X-ray that is taken to show a specific area of concern. If you have a tooth ache, your dentist is likely to recommend a PA film to see that whole tooth including the root. Cone Beam Computed Tomography or 3-dimensional X-rays Advances in technology continue to provide new ways to se
  3. The most common intraoral x-rays include periapical, bitewing, and occlusal x-rays. Extraoral x-rays, on the other hand, are your panoramic and cephalometric x-rays. As mentioned in the previous article ( A Patient's Guide to Dental X-rays ), different conditions and procedures require different types of dental x-ray's
  4. e that the tooth is in a palatal position when a panoramic radiograph is used
  5. Panoramic X-rays, which require a special machine that rotates around the head to provide a detailed image of all the teeth and the underlying bones in a single X-ray. Periapical X-rays, which.
  6. By Lee Ann Brady on 10.03.11 Category: Practice of Dentistry, Preventive Dentistry. Life seems to go in trends, like the day that you work on tooth #19 on every patient. Last week the trend was to discuss why I recommend a full mouth series of radiographs or a Panorex. The first time I got this question was during a presentation on the.
  7. Bite-wing x-rays: A bite-wing x-ray highlights the crowns of the back teeth. They're taken on either one or two sides of the mouth. These x-rays show the upper and lower premolars and molars. Patients are asked to bite down on a wing shaped x-ray holder during the x-ray. Periapical X-ray: A periapical x-ray looks similar to a bite-wing x-ray.
Full mouth x ray series : Hazrat musa movie in hindiOsteoradionecrosis of mandible Images - Frompo

Safety of dental X-rays Coast Pediatric

Anatomy xrays (View these term first, definition 2nd

6 reasons why you should use a panoramic X-ray for

X-Ray Fact Sheet - Ray Tonks, DDS - Dentist in Ann Arbor, MI

Intraoral or panoramic radiography

The panoramic X-ray is the wide shot that lets us see the entire dental arch in one image. It shows not only erupted teeth but also incoming adult teeth and wisdom teeth, which is great for being able to see if there will be enough room for them or if they need some extra help or extraction. Panoramic X-rays also help to identify dental cysts, tumors, and abscesses that develop below the. A periapical x-ray shows the entire length of a tooth from crown to root tip and allows the dentist to diagnose problems associated with the root of the tooth or bone levels around the tooth. Panoramic x-rays can be used to treatment plan for the following: Orthodontics Panoramic Xray Mountain ViewDental X-rays, also called radiographs, are an important tool for the dentist. The three most common types of dental X-rays are the bitewing, periapical and panoramic X-rays. Bitewing X-rays are those that are taken during most routine dental check-ups and are useful for revealing dental cavities between the teeth Periapical X-Rays. At Adelmann Dentistry, we use periapical x-rays (called PAs in dental jargon) to look at the tip of the roots of your teeth and the surrounding bone structure. These x-rays are very useful in cases of trauma or for patients who are experiencing dental pain. Panoramic x-rays give us the big picture image of your.

Panoramic imaging is a curvilinear variant of conventional tomography and is based on the principle of the reciprocal movement of the X-ray source and an image receptor around a central point or plane, called as the image layer. Indications . Orthopantomograph (OPG) proves useful in evaluation and treatment planning of various dental diseases Periapical X-rays are used to determine the structure of the root of the tooth and the abnormality of the surrounding bone structure. Featuring osteoporosis around each tooth, periapical X-Rays are aimed at such conditions as periodontitis, abscesses and the definition of endodontic metastases. Panoramic X-Rays Bitewing X-Rays. Bitewing X-rays show the upper and lower back teeth and how the teeth touch each other in a single view. These X-rays are used to check for decay between the teeth and to show how well the upper and lower teeth line up. They also show bone loss when there is severe gum disease or if a dental infection is present Panoramic X-rays can be better for dentists and patients Panoramic X-rays taken at a young age, especially if done yearly or more often before age 10, also raised the risk of meningiomas by up to five times. fine for the dentist to take X-rays. And X-rays cannot only find cancerous tumors, but can often destroy them Panoramic X-rays are often associated with diagnosing wisdom tooth issues, orthodontic consultations, implant and oral surgery consultations, or may be recommended by the dentist if there is an issue preventing a standard bitewing or periapical x-ray. Our x-ray equipment is fully digital at all 1st Family Dental locations, which means that any.

What is the different purpose between periapical x-ray and

Periapical x-rays can also help catch cysts and abscesses. Panoramic X-rays. Panoramic x-rays are used for the most complete view of your entire mouth. The images don't only show all your teeth, but also your sinuses, jaw joints, and jaw bones. These photos can help determine if wisdom teeth are impacted and can even help diagnose a tumor The periapical X-rays capture image from the crown to the tip of the roots, including the surrounding bony structure of the roots. This radiograph is useful in assessing the ligaments surrounding the roots and also in detecting prolonged infection that has infected the bone surrounding the tooth

What Do Dentists Charge for X-Rays? Is It the Same

A panoramic x-ray or panoramic radiography is a type of dental x-ray that shows a broad view of the mouth, including teeth, jaws, nasal area and surrounding tissues and structures. It is one of the most commonly used dental x-rays along with the bitewing x-ray (used mainly in detecting cavities) and the periapical x-ray (shows entire tooth. Types of x-rays. When the dental assistant places the heavy x-ray shield over your body, you probably don't think about what type of x-ray will be taken. It could be one of three types of x-rays - periapical, bitewing and panoramic - which serve different purposes Bitewing x-rays show the crowns of the upper and lower teeth including the height of the bone surrounding them. Periapical x-rays show the crown, the roots, and the bone around the specific tooth we are concerned about. Panoramic x-rays let us visualize the entire dentition, the jaw bones, the temporomandibular joint (TMJ), and more

Oral Pathology - Radiology (UBSDM) Flashcards Example for Freeradiology-paralleling-technique

Video: Periapical radiograph - SlideShar

impacted teeth

Are Dental X-Rays Safe? Types, Purpose, and Risk

Periapical X-rays show the entire tooth, from the exposed crown to the end of the root and the bones that support the tooth. These X-rays are used to find dental problems below the gum line or in the jaw, such as impacted teeth, abscesses, cysts, tumors, and bone changes linked to some diseases Initial Oral Examinations, Diagnosis, and Full Mouth Series of X-rays or Panoramic X-ray with or without Bitewings - Anthem BCBS will provide benefits once per Member in any three consecutive Calendar Years.Panoramic X-ray with or without Bitewings - Anthem BCBS will provide benefits once per Member in any three consecutive Calendar Years It's Time For Your Close-Up: Periapical X-Rays This intraoral X-ray is the close-up of the dental world. If a specific tooth or area in your mouth is bothering you, we'll probably take a periapical X-ray to get a clear idea of what's going on there, but they can also be taken alongside bitewing X-rays even if you aren't aware of an. Periapical X-Rays. When visual inspection of the teeth raises some concerns, the periapical X-rays will provide answers and result in proper diagnosis. This type of radiograph will disclose the entire structure of the tooth including the apex and any surrounding tissue and bone. Panoramic X-ray radiation exposure is the same radiation you. Periapical X-Rays Pediatric Dentistry NJ . What Are Periapical X-Rays? A periapical x-ray or PA film will show one or two teeth in their entirety in one single image, right from the crown of the tooth which is the part exposed in the mouth to the very tips of the tooth roots located in the jawbone, as well as the surrounding bone supporting this tooth

The Dental CBCT: Why You Need More Than a Standard X-Ray

According to Authority Dental, X-rays for your teeth cost $25-$750. The average cost of a bitewing X-ray is usually $35. The average cost of a periapical X-ray is around the same. Meanwhile, panoramic X-rays capture your entire mouth and jaw in one image. How many dental xrays are safe In panoramic imaging, the X-ray tube rotates around the patient's head in one direction while the receptor rotates _____ direction. Horizontally in the opposite In panoramic imaging, the movement of the receptor and the tubehead produces an image through the process known a