Your SlideShare is downloading. ×
Digital imaging /certified fixed orthodontic courses by Indian dental academy
Upcoming SlideShare
Loading in...5

Thanks for flagging this SlideShare!

Oops! An error has occurred.


Saving this for later?

Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime - even offline.

Text the download link to your phone

Standard text messaging rates apply

Digital imaging /certified fixed orthodontic courses by Indian dental academy


Published on

The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit ,or call

Published in: Art & Photos, Technology

1 Like
  • Be the first to comment

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

No notes for slide


  • 1. INDIAN DENTAL ACADEMY Leader in continuing dental education
  • 3. Cephalostat in 1931 Broadbent-Bolton (USA) Hofrath (Germany) De Nevreze’s (1936) profilometer  oriented to the FH
  • 4. Korkhaus, 1937  Waldo, 1938 Marcolis, 1940 
  • 5. Weingart, 1948  Thurow, 1951 Bjork, 1951
  • 6. Reboul (1954) described a simple way adjustment and simple  head-holder. User a cephalostat is well adjusted, it cannot be  expected to obtain accurate superimposition between left and  right slides.
  • 7. Laster model of the  Broadbent-Bolton  Roentgenographic  Cephalometer
  • 8. Elsasser 1951 - 1953 proposes the ORTHOMETER   which measures the departure of various points in the  facial midline form orthognathy
  • 9. After the Discovery of X-rays by Roentgen in 1895,traditional 2-D cephalographs also known as Roentgenographic cephalometry was introduced by Broadbent 36 years later. With the arrival of the cephalometric technique and its increasing popularity clarification of the anatomic basis for malocclusions became possible.
  • 10. Limitations of 2D’s Several reasons for limited validity of the 2D Cephalometry’s scientific method : 1. A conventional headfilm is a 2D representation of a 3D object. 2. Cephalometric analyses are based on the assumption of a perfect superimposition of the right and left sides about the mid sagittal plane.
  • 11. 3. a) b) c) d) e) A significant amount of external error, known as radiographic projection error, is associated with image acquisition. Size Magnification Distortion Patient positioning Projection distortion
  • 12. 4. 5. Manual data collection and processing in cephalometric analysis has been shown to have low accuracy and precision. Errors in location of landmarks due to the lack of well defined outlines, hard edges and shadows.
  • 13. What is a digital image?  A digital image is a matrix of square pieces, or picture elements (pixels), that form a mosaic pattern from which the original image can be reconstructed for visual display.
  • 14. What is an Analog image  An analog image, such as a radiographic film, has virtually an infinite number of elements, with each element represented by a continuous gray scale.
  • 15. Imaging and Image acquisition Images Conventional ANALOG PROCESS Contemporary DIGITAL PROCESS
  • 16. Characteristics of digital images    A digital image is composed of picture elements (pixels) that are arranged in a 2‑dimensional rectangular grid, with each pixel having a specific size, color, intensity value, and location within the image (ie, bitmapped or raster). A pixel is the smallest element of a digitized image. Radiographic images generally use gray color with an intensity value between 8 bits (28 or 256 shades of gray) and 12 bits (2 12 or 4096 shades of gray). Image resolution refers to the degree of sharpness of the image. Resolution is determined by the number of pixels per given length of an image (pixels/ mm), the number of gray levels per pixel (bits), and the management of the gray levels.
  • 17.   The pixels in a digital image are arranged in a matrix. If a large number of pixels are used to represent an image, their discrete nature becomes less apparent, i.e., the spatial resolution of the image improves as the number of pixels increases. Each pixel has a digital value that represents the intensity of the information recorded by the detector at that point. Each digital value is represented as a binary number; information is recorded in terms of a series of ones or zeros. Each one or zero is called a “bit.” In a 6-bit image each pixel will have 64 possible values, ranging from 0, which represents a black area on the image, to 63, which represents a white area; an 8-bit image each pixel will have 256 possible values. The quality of an image depends on both the number of pixels and the number of gray levels which make up the image.
  • 18.   A pixel has no size or shape. At the time it's born, it's simply an electrical charge. A pixel is only given size and shape by the device we use to display or print it. The size of a digital photo sensor is determined by the number of photo sites that it has on its surface. Even though the captured pixels have no physical dimensions, this size is usually specified in one of two ways--by the sensor's dimen-sion in pixels, or by its total number of pixels. For example, the same image can be said to have 1,800 X 1,600 pixels (expressed as "1,800 by 1,600"), or to contain 2.88 million pixels (1,800 multiplied by 1,600). When a digital image is displayed on the computer screen, its size is determined by three factors: the screen's resolution, the screen's size, and the number of pixels in the image.
  • 19. Image enhancement       There is potential for improving the diagnostic quality of digital images by enhancing the images using various algorithms. Digital images can be enhanced using algorithms that mathematically manipulate the gray-level values of the pixels. Using enhancement algorithms it may be possible to extract information from radiographs that previously required further additional radiographic exposure to the patient. However, image enhancement is actually the suppression of information that the operator deems unnecessary for a particular task, rather than the addition of further information. Image enhancement can be divided into three main areas: Contrast improvement, Smoothing and Edge enhancement
  • 20. Devices to store digital images    Magnetic tapes Laser or optical disks Optical tapes
  • 21. Film based imaging  Film-based imaging consists of X-ray interaction with electrons in the film emulsion, production of a latent image, and chemical processing that transforms the latent image into a visible one. As such, radiographic film provides a medium for recording, displaying, and storing diagnostic information. Film-based images are described as analog images. Analog images are characterized by continuous shades of gray from one area to the next between the extremes of black and white
  • 22. Each shade of gray has an optical density (darkness) related to the amount of light that can pass through the image at a specific site. Film displays higher resolution than digital receptors with a resolving power of about 16 lp/mm. However, film is a relatively in efficient radiation detector and, thus, requires relatively high radiation exposure. The use of rectangular collimation and the highest speed film are methods that reduce radiation exposure, but these techniques are not practiced commonly. Chemicals are needed to process the image and are often the source of errors and retakes. The final result is a fixed image that is difficult to manipulate once captured.
  • 24. Digital imaging Digital imaging is the result of X-ray interaction with electrons in electronic sensor pixels (picture elements), conversion of analog data to digital data, computer processing, and display of the visible image on a computer screen. Data acquired by the sensor is communicated to the computer in analog form. Computers operate on the binary number system in which two digits (0 and 1) are used to represent data. These two characters are called bits (binary digit), and they form words eight or more bits in length called bytes. The total number of possible bytes for 8-bit language is 2* = 256. The analog-to-digital converter transforms analog data into numerical data based on the binary number system. The voltage of the output signal is measured and assigned a number from 0 (black) to 255 (white) according to the intensity of the voltage. These numerical assignments translate into 256 shades of gray.
  • 25. The human eye is able to detect approximately 32 gray levels. Some digital systems sample the raw data at a resolution of more than 256 gray values such as 10 bit or 12 bit values. The large number of gray values is reduced to 256 shades of gray with the advantage of controlling under or overexposed images. Direct digital imaging systems produce a dynamic image that permits immediate display, image enhancement, storage, retrieval, and transmission. Digital sensors are more sensitive than film and require significantly lower radiation exposure. Dynamic range or latitude is the range of exposures that will produce images within the useful density range.
  • 26. Resolution   The quality of a digital image depends in part on the number of pixels used to create the image. This is referred to as Resolution. More pixels add detail and sharpen images. If any digital image is enlarged enough, the pixels will begin to show an effect called pixelization. The more pixels are there in the image, the more it can be enlarged before the pixelization occurs.
  • 27. DIGITAL PHOTOGRAPHY  Digital photography is essentially the same as conventional photography except that in the place of the photographic film the camera stores all of its images onto a computer chip or a similar storage medium in a digital format
  • 29. Resolution for orthodontic photography  To be useful for orthodontic photography the resolution has to be minimum of 800*600 and 1800 *1600 or to contain 2.88 million pixels (1800 multiplied by 1600) produce excellent pictures.
  • 30. HOW A DIGITAL CAMERA WORKS  The big difference between traditional film cameras and digital cameras is how they capture the images. Instead of the film, digital cameras use a solid state device called an image sensor, usually a charge couple device or complementary metal oxide semiconductor. On the surface of each of these finger nail sized silicon chips is a grid containing hundreds of thousand or millions of photo sensitive diodes called photo sites, photo elements, or pixels. Each photo site captures a single pixel in the photograph to be .
  • 31. THE EXPOSURE when shutter release button of a digital camera is pressed a metering cell measures the light coming through the lens and sets the aperture and shutter speed for the correct exposure. When the shutter opens briefly, each pixel on the image sensor records the brightness of the light that falls on it by accumulating an electric charge. The more the light that hits a pixel, the higher the charge it records. Pixels capturing light from highlights in the screen will have high charges. Those capturing from shadows will have low charges
  • 32. Evaluating Image Quality  When we look at a photograph, we make an overall appraisal on two levels of detail: content and quality. In orthodontic photography, there are many details we can examine to determine the quality of an image. As an example, we should look for the edges of the rectangular wire, the contour of the rubber ligatures, the ends of the plastic separators, and the sharpness of the premolar brackets in the background. Other details in this type of photograph can be saliva bubbles, mucous veins, the hairs around the lips, and the palatal creases.
  • 33. Optimal Image Sizes   There are two kinds of image sizes often termed as resolution -- optical and interpolated. The optical resolution of a camera or scanner is the actual number of the image sensor's photosites. This resolution can be improved to a limited extent by a process called interpolat-ed resolution, which adds pixels to the image using software. The program evaluates the pixels surrounding each new pixel to determine what its colors should be. For example, if all the pixels around a newly inserted pixel are red, the new pixel will be made red. What's important to keep in mind is that interpolated resolution doesn't add any new information to the image--it just adds pixels and makes the file larger..
  • 34. Understanding Image Files and Compression   JPEG (Joint Photographic Experts Group, is by far the most popular format for display of photographic images on the Internet. Although these files have traditionally used a ".jpg" extension, the actual file format is called JFIF (JPEG File Interchange Format). GIF, has been optimized for the display of type and line drawings, but supports only 8-bit color on the computer screen, whereas JPEG supports the more detailed 24-bit color. The JPEG format uses a "lossy" compression scheme that makes digital files smaller, but sacrifices image quality. Compression is performed on blocks of pixels, eight on a side. Every time we open one of these files and then save it again, the image is compressed. As the image go through a series of saves, it becomes more and more degraded. Therefore, one should not use the JPEG format to save original images and expect to modify later. All originals should be saved in a loss-free format such as TIFF (Tag Image File Format) or BMP (bitmap) at maximum color depth.
  • 35.  A new JPEG 2000 format, not yet available in digital cameras, uses wavelet technology to allow higher compression with fewer image flaws. With this type of compression, the image is "streamed," or gradually filled in with more detail. JPEG 2000 images can be saved in "loss-less" files and will have the same color scheme on any display system
  • 36.  Most digital cameras have a default resolution of JPEG 72dpi, which is good for displaying on computer screens or in presentations (although 90dpi would be ideal), but produces poor quality for publication . Images of this resolution become completely distorted when enlarged, and most printed orthodontic journals will not accept them. Some camera models allow higher resolutions to be used in TIFF or BMP formats, which are more suitable for publication. These non-compressed images take up much more space, however, making it possible to fill the camera's memory with only four to six high-resolution photographs. Furthermore, the TIFF 300-350dpi is the ideal format for interpo-lating without noticeably distorting the photograph, thus occupying less memory.
  • 37. VIDEO IMAGING    Video capture is used less frequently for facial and intra oral image acquisition. Video capture systems connect video camera to a computer through a frame grabber. A frame grabber is an interface board in a computer that converts the analog video signal from a video camera into a 24- bit RGB digital image. The frame grabber grabs an image frame from the continuous video signal. Frame grabbers in clinical use acquire images at 640 by 480 resolution for NTSC signals and 768 by 576 for SECAM or PAL signals.
  • 38.     Image quality greatly depends on the type of signal generated by the vide camera. The three common types are COMPOSITE SIGNALS, S – VIDEO SIGNALS, RED-GREEN-BLUE (RGB) SIGNALS
  • 39.  Composite signals combines luminance (brightness) and chrominance (color) information into one signal. S- video, also known as Y-C, uses separate signals for luminance (Y) and chrominance (C), resulting in higher over all image quality.  RGB component video separates the red, green, and blue information into separate signals and generates the highest quality image.  S-video or RGB video signals are the preferred for clinical imaging.
  • 40.  For facial and intra oral shots, video –captured image resolution is low compared with images acquired with mega pixel digital cameras. Video captures chief advantage over digital photography is immediacy; images need not to be transferred via a flash memory card from the camera to a computer. However, optimal video lighting is difficult to achieve, especially for intra oral views. Further more, video capture systems are tethered by a video cable to a computer, where as digital cameras are portable and easy to use in several locations
  • 41. Digital Radiograph (RVG) sensor head object x-ray source scintillator CCD fibre optic layer transmitter converter amplifier PC quantizer amplifier receiver
  • 42. Direct Digital Imaging         A number of components are required for direct digital image production. These components include X-ray source, Electronic sensor, a Digital interface card, Computer with an analog todigital converter (ADC), Screen monitor, Software, and Printer.
  • 44. Digital radiograph • Amorphous Selenium • CCDs • Amorphous Silicon • Phosphor plates
  • 45. Direct digital sensors      are either a CHARGE-COUPLED DEVICE (CCD)or COMPLEMENTARY METAL OXIDE SEMICONDUCTOR ACTIVE PIXEL SENSOR (CMOS-APS). The CCD is a solid-state detector composed of an array of X-ray or light sensitive pixels on a pure silicon chip. A pixel or picture element consists of a small electron well into which the X-ray or light energy is deposited upon exposure. The individual CCD pixel size is approximately 40µ with the latest versions in the 20µ range. The rows of pixels are arranged in a matrix of 512 x 512 pixels. Charge coupling is a process whereby the number of electrons deposited in each pixel are transferred from one wall to the next in a sequential manner to a read-out amplifier for image display on the monitor. There are two types of digital sensor array designs: AREA AND LINEAR. Area arrays are used for intra oral radiography, while linear arrays are used in extraoral imaging. Area arrays are available in sizes comparable to size 0, size 1, and size 2 film, but the sensors are rigid and area for image acquisition.
  • 46.     thicker than radiographic film and have a smaller sensitive area for image capture. The sensor communicates with the computer through an electrical cable. Area array CCDs have two primary formats: Fiber optically coupled sensors and direct sensors Fiber optically coupled sensors utilize a scintillation screen coupled to a CCD. When X-rays interact with the screen material, light photons are generated, detected, and stored by CCD. Direct sensor CCD arrays capture the image directly.
  • 47. X-RAY IMAGING WITH CCD SCINTILLATOR - converts x-radiation to photons (light) FIBRE OPTIC LAYER - conducts photons to CCD - stops x-radiation CCD - converts photons to electrons (charge) ELECTRONIC CIRCUIT - amplifies the signal - converts the analog signal to digital
  • 48.  The complementary metal oxide semiconductor active pixel sensor (CMOS-APS) is the latest development in direct digital sensor technology. Externally, CMOS sensors appear identical to CCD detectors but they use an active pixel technology and are less expensive to manufacture. The APS technology reduces by a factor of 100 the system power required to process the image compared with the CCD. In addition, the APS system eliminates the need for charge transfer and may improve the reliability and lifespan of the sensor. In summary, CMOS sensors have several advantages including design integration, low power requirements, manufacturability, and low cost. However, CMOS sensors have more fixed pattern noise and a smaller active area for image acquisition.
  • 49. Indirect or Scanned Digital Imaging  Indirect digital imaging implies the image is captured in an analog or continuous format and then converted into a digital format. As with any data conversion, this analog to digital conversion (ADC) results in the loss and alteration of information.
  • 50.  Instead of capturing the border that traverses a particular pixel, the pixel value is averaged. This is called partial volume averaging. Consequently, many edges are lost or distorted in an analog to digital conversion. The original indirect digital imaging technique was to optically scan a conventional film image (analog) and generate a digital image. Obviously, this technique required an optical scanner capable of processing transparent images as well as the appropriate software to produce the digital image.
  • 51. Indirect Photostimuable Phosphor Plates  Imaging using a photostimulable phosphor (PSP) can also be described as an indirect digital imaging technique. The image is captured on a phosphor plate as analog information and is converted into a digital format when the plate is processed. The PSP consists of a polyester base coated with a crystalline halide emulsion that converts X-radiation into stored energy. The crystalline emulsion is made up of a europium-activated barium fluoro halide compound (BaFBrEu 2+). The energy stored in these crystals is released as blue fluorescent light when the PSP is scanned with a helium-neon laser beam. The emitted light is captured and intensified by a photomultiplier tube and then converted into digital data. Not all of the energy stored in the PSP is released during scanning and consequently, the imaging plates must be treated to remove any residual energy. PSP technology is used for intra oral as well as extraoral
  • 52. Principle of phosphor plate imaging
  • 53. For CCD-based digital radiography, panoramic units and combination units (in which both panoramic images and cephalograms can be recorded) are available . Cross-sectional tomography, which is sometimes useful in the management of orthodontic patients, cannot be performed with the CCD-based digital units. Some companies offer to rebuild a conventional panoramic unit to work with a CCD sensor. If this is done, film can no longer be used in the system because the CCD receptor works in a very different manner than the film. Only the Digi Pan (Trophy Radiology, France) unit allows the CCD-based receptor to be exchanged with a conventional film cassette system.
  • 54.  CCD receptors are more sensitive to x- rays so the exposure can be lower with the film. Where as most of the SP systems recommend using the same dose as with film
  • 55. The SP imaging plate systems can, in principle, work with any available conventional radiographic equipment because the plates are installed in the same cassette type as film. The only difference between SP and film radiography is that the SP plate replaces the film and the intensifying screen in the cassette. After exposure the plate is read into the scanner. The plates are sensitive to light and highly sensitive to the infra red light.
  • 56.
  • 57. Advantages of digital radiography over conventional radiography are:      Working time from image exposure to image display is reduced . Chemical processing is avoided, so there are fewer hazards to the environment and no image errors because of processing. Exposure to radiation is reduced . Greater dynamic range is available compared with film; overexposure and underexposure are less apt to occur, contrast and density can be enhanced, size can be changed, and colors added. Cephalometric measurements and analyses can be more easily performed with the aid of task dependent software. Storage and communication are electronic, so copies of an image can be sent to others without losing the original.
  • 58. CEPHALOMETRIC APPLICATIONS  Cephalometric soft ware is routinely used for case diagnosis and treatment planning. These applications replace manual acetate tracings with computer generated tracings derived from digitized head films. During the process of digitization, the X-Y coordinates of cephalometric landmarks are recorded and stored in a dataset from which various cephalometric measurements are made. The datasets are also the starting point for formulation of VTO’S and STO’S . Cephalograms are two dimensional representations of three dimensional anatomy.
  • 60. DIGITIZATION     Digitization is a process by which analog information is converted into digital format Methods of digitization: POINT MODE DIGITIZATION, STREAM MODE DIGITIZATION.
  • 61. Point mode digitization  It refers to the discrete location of individual landmarks. The user sequentially locates landmarks in a predetermined order, recording one coordinate pair for each landmark. A visual representation of cephalogram is generated by connecting discretely digitized landmarks with lines or curves. If the digitizing landmarks have been suitably selected and are in reasonable proximity, the resulting vector tracing is an effective representation of the original radiographic contours.
  • 62. Stream mode digitization  It is a process in which a stream of coordinate pairs is recorded as the user traces a radiographic contour. The stream of points is controlled by programmable options; points may be recorded at a specified number of coordinate pairs per second or after the cursor has moved a minimal distance. A large number of adjacent points are transmitted, and these when joined in a simple point- to –point fashion, provide a credible representation of radiographic contours.
  • 63. With the advent of DIGIGRAPH, work station Sonic digitization provides a new measuring technique For registering linear distances. The original concept Was to eliminate or minimize the need for radiation Exposure in obtaining lateral cephalometric measurements for Patients diagnosis. It also includes a module for doing space analysis utilizing study casts. In this way comprehensive records for diagnosis and treatment planning were obtained SONIC DIGITIZATION
  • 64. Point mode digitization Stream mode digitization More time consuming Less time consuming More accurate landmark locations Less accuracy Less technique sensitive Highly technique sensitive needs a digitizing cursor or mouse Reliable and precision less reliable
  • 65. CRITERIA IN SELECTING A CEPHALOMETRIC SOFTWARE CONVERGENCE The software database should integrate cephalometric digital images both photographic and personal data of the patient ,dental chart etc. this will basically ensure that each patient has only one file, and all elements can be accessed there from . In the ideal scenario it must be possible to access other office management functions like scheduling , fee management , correspondence and the like also from the patient file .
  • 66. RELIABILITY Software programmes contain “bugs” causing the programmes to malfunction or to “crash”. It is typical to custom made software's, as big companies often have a β version and is field tested before marketing. It is good idea to first check with an user before actually buying the software to check out “run time error”
  • 67. RELEVENCE This is a major aspect in evaluating cephalometric software. Most commercial programmes offer most of the better-known cephalometric analysis for both lateral & PA views. Most programmes have a fixed no of cephalometric landmarks, typically between 50 to 200 and various permutation combinations of planes and angles based on these which can be user determined. Some programmes have the facility to define new landmarks and offer the maximum flexibility in this regard.
  • 68. ACCURACY It is another major aspect, given the error prone nature of cephalometrics. There are basically two type of inputs i.e. the digitizer & the scanner. The digitizer is definitely more accurate as it is a direct transfer, but the digitizer is a costly piece of equipment. Scanners are cheap but tend to have magnification problems, but can be easily over come by placing a calibrated ruler over the cephalogram. Accuracy of +0.25/ mm is to be ensured in the input device, whether it be a digitizer or scanner.
  • 69. ON-SCREN MEASUREMENTS Most programmes offer an electronic caliper to measure distances and or angles on the screen. INTEGRATION WITH DIGITAL PHOTOGRAPHS Most of the newer versions of the software permits superimposition of the digital photograph over the "ceph tracing" producing a photo cephalometric montage for clinical visualization. Most often the superimposition is accomplished by superimposing on the FHP registering at Po or Or.
  • 70. IMPORT/EXPORT FEATURE Most programmes will have an import/export feature permitting data to be imported and exported. Exporting of the data to statistical programmes are valuable when studies are being conducted and batch processing of data is necessary. Likewise export to graphic display like charts is also a desirable feature.
  • 71. WINDOWS BASED CONTROLS The programming language usually comes with an array of controls for image editing such as exposure, zoom, quality adjustment controls etc. Most of the current software's offer image enhancement features, for adjusting under/over exposure of the cephalogram. IMAGE SMOOTHENING The computer image many years ago when printed used to have a dotted appearance because of the pixel pattern of the display. Current programmes use, image smoothing technology called "anti aliasing" and Bezier curves, for print outs so that print outs produce outlines that are smooth and more like the manual tracing. A perusal of the print out will show the adequacy of the soft ware in this respect.
  • 72. COLOUR CODING Color coding is essential for designating cephalograms taken at different time points. ie; T, and T2 etc. This should be user determinable. UPGRADABILITY computer technology is fast advancing and hence the soft ware should be upgradeable and the company that offers it should be around, and capable of performing the upgrade. Most companies offer up gradation through internet connectivity, which is very useful for adding newer versions or downloading “patches” that are offered from tie to time
  • 73. COST Budgetary considerations are also important. A particular aspect is the licensing policy of the company for multiple copies/sites for those having satellite clinics. Over the year prices of most software’s has dropped and they have become affordable and is a real time saving tool
  • 74. DIGITAL PROCEDURE TO ASSESS FACIAL ASYMMETRY   screening facial skeleton asymmetries and distinguishing growth discrepancies from simple rotations of the mandible can be difficult. Conventional panoramic, frontal, and submental vertical radiographs, computed tomography (CT) scans, and magnetic resonance imaging have been used to determine facial harmony and skeletal deviation before dental treatment to avoid possible iatrogenic temporo-mandibular disorders.
  • 75.   A frontal view of the subject's face was recorded with a digital camera, when useful, the subject's frontal cephalogram was also photographed. The subject was positioned face forward with both ears clearly visible to the photographer. The mid sagittal reference plane for the frontal photograph is a vertical line that crossed the midpoint of a virtual line joining the pupils; it is located with a ruler on the screen. The vertical plane had to be perpendicular to the upper border of the computer screen and the bi pupilar line. If the lines diverged, the nose and pupils were examined; any deviation of the nose tip with or without an irregularity in the transverse or vertical location of the pupils was considered a sign of possible upper and midface asymmetry. In such cases, no correction of head tipping to obtain parallelism between the pupils and the screen border was attempted.
  • 76.  The reference plane for the frontal cephalogram was perpendicular to the midpoint of the intersection of a line joining the 2 lateroorbital points and the base of the crista galli . In cases of upper and midface asymmetry, a perpendicular line drawn from the base of the crista galli on the tangential projection of the planum sphenoidal defined the vertical and horizontal coordinates of the reference planes.
  • 77. Reference lines used to define midsagittal plane in photographic (PHP) and radiographic (RHP) images. PHIP is perpendicular at midpoint of line between pupils; RHIP is perpendicular from base of crista galli through line joining 2 lateroorbital points.
  • 78. In cases of severe upper face and midface asymmetry, sagittal reference plane should follow upper portion of nasal crest. Horizontal plane is perpendicular to nasal line through its midpoint.
  • 79.    Each cropped half face was then inverted to obtain an inverted right or left half face. Next, either the half faces were merged, or I inverted half face was superimposed on the original photograph. To merge, each half face was combined with its inverted half Both photographs were then compared with the original full photograph. For superimposition the original photograph was outlined and transformed as a negative to produce black contours on a white background. Each half‑face photograph was also outlined but kept positive with white contours on a black background
  • 80.   All outlined photographs were made 30% to 40% less opaque to achieve good superimposition. Inverted outlined half faces were superimposed separately on the inverted, contoured, and negatively transformed originals.. When necessary, cephalograms were examined by merging the half faces with or without inversion and with or without transformation from negative to positive.
  • 81. Superimposition of transparent original and inverted half faces helps to define growth deficit. Original outline is black, and inverted outline is white.
  • 82.
  • 83. right left
  • 84. Electronic digital study models: Advantages:      Production is easy, routine and predictable. relatively in expensive to produce Easy to examine and measure. Can be mounted /articulated in a variety of ways to simulate occlusal relationships True 3D medium that accurately represents normal/ malocclusions
  • 85. Disadvantages:     Storage a major problem- because of physical size and weight Labor intensive cataloging and retrieving Easily lost or damaged Bulky to transfer
  • 86.  Very accurate three-dimensional geometric crown models are now commercially available from different sources. Destructive scanning methods (Orthocad from Cadent) slice the dental impression of the patient as it is scanned producing a stack of images that are rendered to produce the final model. Laser systems are also used to directly image the stone model of patient’s dentition (e-Models from GeoDigm Corp.). A direct imaging method (OraScanner from OraMetrix) also exists wherein an intra-oral camera capable of generating highly accurate 3D crown models is used after applying an opaquing agent to the teeth. However all these methods provide data on the tooth crowns only and nothing on root form.
  • 87.  Even so, the only true 3D information routinely used today is plaster study models of the teeth, and the models are not accurately merged or calibrated with the other diagnostic information. Some techniques exist to create 3D digital study models that can be viewed on a computer screen. Although these might be accurate representations of the occlusal anatomy, they still have the limitation of showing only the crowns and occlusal surfaces of the teeth, and they cannot show the true size, location, or relationships of the roots of the teeth and other anatomy
  • 88.  Current methods to produce 3-dimensional tooth root models involve conversion from radiographic means (computed tomography) or creation using computer-assisted design (CAD) software. The CT lacks detail while the CAD is manually fabricated and can bear little resemblance to the original. Thinplate splines have been used in morphometrics to define changes of shape between subjects of the same species . Thin-plate splines are used to deform a 3D geometric prior model of a tooth to match 2D patient radiographs, producing a “best-fit” patient specific 3D geometric polygonal mesh of the tooth.
  • 89. Peri apical radiograph of the second bicuspid; View of the 3D prior geometric tooth; Both the radiograph and the 3D model overlaid
  • 90. Landmarks interactively selected by the user in the 3D prior model image (+) and the radiograph the overlaid image of the shell of the tooth 3D model (before fitting) and the shaded warped image of the fitted 3D model.
  • 91. Features of a scanner        When scanning photographs or other orthodontic records, we need resolution of 600 dots per inch (dpi),. When scanning slides with higher details we need 1200 dots per inch (dpi)., When scanning a cephalogram we need min of 150 -300 dpi. For printing of cephalogram we need to scan in 300 dpi. For placing pictures in slide shows the resolution of 150 dpi is enough The scanner should have a transparency adapter to scan slides and radiographs. The higher the optical density, the better will be the detail in the dark part of images, especially the radiographs, a value of 3.4 or above is ideal. This is measured on a logarithmic scale, so a difference of 1unit means 10 times better. A scanner with density 3.3 is 2 times better than a scanner with density 3.0.
  • 92. LASER SCAN  In a laser scan, a positive model is first created, and laser light is then reflected from the surface of the model. The resulting scatter pattern is captured by an optical sensor, and the original shape is reconstructed with mathematical algorithms. Laser scanning is relatively inexpensive, but the process is slow, and the resolution is limited to about 300 microns. Only 1object can be scanned at a time; this limits the number of models that can be processed per day. Laser scanning cannot be used to accurately scan impressions directly, because undercuts in the impression create hidden surfaces that are inaccessible by the laser beam
  • 93. DESTRUCTIVE SCAN  In a destructive scan, a positive model is created and encased in a contrasting urethane resin. Paper‑thin slices of the encased object are incrementally removed by a computer numerical‑controlled machine cutter. After each increment is removed, a digital picture of the exposed area is captured. The scanned layers are electronically combined to recreate the original geometry. Destructive scanning technology is accurate to about 50 microns, but the object is destroyed in the process (hence the name). The preprocessing step (encasing) can be messy, but many objects can be encased together and scanned at once for efficiency. Impressions and bite registrations are not typically scanned directly because (1) rubbery materials such as PVS are difficult to slice cleanly in the scanner, (2) the wide variety of PVS colors available makes calibration difficult, and (3) the destructive process allows only 1 chance to correctly acquire the scan.
  • 94. WHITE LIGHT SCAN  A white‑light scan is similar to a laser scan, but white‑light interference patterns (moir6 patterns) are reflected instead of laser light; this improves resolution and reduces scan time. Direct line‑of‑sight of all surfaces of the object is still required for accuracy, so a plaster model must first be made.
  • 95. CT SCAN  In a CT scan, a series of digital radiographs of the object is captured, and the images are electronically processed to generate an extremely detailed 3‑dimensional reproduction of the object. The scanner can scan both stone models and impressions (if the tray is not steel or other high‑density material), because any undercuts are completely visible to the scanner. Many objects can be scanned at once for maximum efficiency. PVS bite registrations can also be scanned.
  • 96.  CT impression scanning is the preferred method because of its speed and accuracy. To create a virtual dental model directly from the impression with CT scanning, the impression is mounted on a platform that rotates in front of an amorphous silicon x‑ray sensor. Hundreds of digital radiographs of the impression are captured as it rotates 360'. These radiographs are converted to images called sinograms , which represent the data from a horizontal line of the detector as the part rotates .
  • 97.  A 16 central‑processing‑unit fiber‑optically linked computing cluster uses the sinograms and a series of mathematical algorithms to create 116‑micron thick reconstruction slices of the object . These slices are stacked electronically and inverted, and the resulting surface is smoothed to yield a raw electronic study model
  • 98.  Upon the prescribing clinician's approval of the diagnostic setup and the treatment animation (staging), each stage of treatment is converted into a physical model with a machine called a stereolithography apparatus (SLA). These SLA resin models are loaded into an automated aligner‑forming system that heats, forms, and laser‑marks sheet plastic over each plastic model. These parts are transported on a conveyor belt to a robotic arm that loads each part into an automated cutting machine for trimming Automation enables aligner trimming to be completed in less than 30 seconds. Once trimmed, the part is ejected, and the aligner is separated, polished, disinfected, and packaged for shipment .
  • 99. Impressions are made using Polyvinyl Siloxane Impression and bite send along with a detailed treatment plan. Advanced imaging technology transforms plaster models into a highly accurate 3-D digital image. A computerized movie called ClinCheck® depicting the movement of teeth from the beginning to the final position is created. INVISALIGN Customized set of aligners are made from these models, sent to the doctor, and given to the patient. Pt to wear each aligner for about two weeks. From the approved file, laser scanning to build a set Invisalign® uses of actual models that reflect each stage of the treatment plan. Using the Internet, the doctor reviews the ClinCheck file - if necessary, adjustments to the depicted plan are made.
  • 101. OraScanner a light‑based imaging device Diagnosis and treatment planning Obtaining a Virtual model SURE SMILE TECHNOLOGY Wire bending robot Producing arch wires "virtual bracket placement" and selection of the sequence and progression archwire
  • 102. 3D IMAGING  Selected digital imaging devices can produce digital volumes or 3D images. The volume element (voxel) is the smallest element of a 3‑ dimensional image. A voxel volume can be thought of as a 3D array or stack of bitmapped images, with each voxel having height, width, and thickness.
  • 103. Why do we need a three dimensional record???  In clinical orthodontics it is not enough just to accurately image the facial shape but essential to be able to detect changes in the image. When evaluating the success of appliance therapy it is also important to be able to distinguish between changes in morphology due to treatment and changes due to other factors such as growth and normal variation.
  • 104.  In traditional cephalometry 3D craniofacial structures are projected onto 2D radiographic film. This process creates cephalometric landmarks that do not exist in patient. These structures are effectively optical illusions of craniofacial anatomy. Ex are mandibular symphysis, pterygoid fossa, and the key ridge. Although we refer to these structures are anatomical landmarks, they are in fact, artifacts of the cephalometric technique. Another problem arises when bilateral structures are averaged to create a unified anatomic outline. Averaging the structures results in a loss of parasagittal information and any true asymmetry of the patient is lost.
  • 105. BASIC PRINCIPLES TO MEASURE IN THREE DIMENSIONS  There are two geometric strategies for measuring in three dimensions. They are ORTHOGONAL MEASUREMENT MEASUREMENT BY TRIANGULATION
  • 106. ORTHOGONAL MEASUREMENT  The general characteristic of orthogonal systems is that they locate the third dimension (Z) by a technique separate from that used to measure the other two dimensions (X and Y). In most measurements the object to be measured is sliced into layers, either physically or optically. Ex: serial section of histology and pathology. Here the specimen is sliced into a number of layers of known thickness. The X and Y dimensions are measured on the slice surface and the Z Dimension is measured by tallying how many slices into the specimen lies. The common feature of all orthogonal measuring systems is that X and Y distances are captured by some method other than that used for capturing Z. Ex: CT scanner
  • 107. COMPUTED TOMOGRAPHY computed to-mography (CT) machines acquire image data by using either a single narrow x‑ ray beam or a thin, broad, fan‑ shaped x‑ ray beam. These beams rotate around the patient in a circular or spiral path as the patient moves through the scanning machine or as the rotating beam passes over the patient.
  • 108. CT SCAN  The advent of computerized transverse axial scanning, computed tomography, or CT greatly facilitated access to the internal morphology of soft tissue and skeletal structures. Conventional CT scanning is accomplished by acquiring a series of individual images. Typically, the images represent crosssections through the body. The image slices are from 1 to 10 millimeters thick and the distances between them are from 1 to 10 or 20 millimeters. Projection data are acquired and reconstructed into images as the patient is moved incrementally through the CT gantry (that is, an image is obtained; the patient is moved to the next scanning position, and the next image is obtained). CT scans possess no magnification errors caused by geometric distortions. Such errors are common in conventional radiographs.
  • 109. COMPUTED TOMOGRAPHY Parts of the Equipment; 1. Scanner ( movable x ray table + gantry) 2. Computer system 3. A display console
  • 110.  A limitation of conventional CT is that although it has a high degree of accuracy within individual slices, it has relatively low between-slice accuracy even with relatively narrow collimation (2 mm) and no interslice gaps. CT scans avoid the superimposition of structures and are, therefore, more desirable than conventional radiography as a morphometric tool. Since its inception, computed tomography has provided quantitative measurements for many different biological systems and has been used in pre- and post-surgical mapping procedures, the evaluation of developmental and regressive dental abnormalities, facial trauma, and temporo mandibular joint disorders.
  • 111. RADIATION DOSAGE FOR CT Radiation dosage 1.536 rad for a single section 1.8432 rad for multiple sections Estimated dose to the centre of the condyle with CT is 180mR
  • 112. NEW TOM SCANNER The NewTom 900 scanner uses a cone‑ shaped x‑ ray beam that is large enough to encompass the region of interest. This type of beam uses the x‑ ray emissions very efficiently, thus reducing the absorbed dose to the patient. This type of beam also allows for the acquisition of the image data in 1 revolution of the x‑ ray source and detector without the need for patient movement. These attributes make this system more efficient and mechanically simpler than others, and thus it can be designed for specific purposes, such as imaging the maxillofacial region.
  • 113. The NewTom 9000 volume imaging technique uses the principle of tomo synthesis or cone‑ beamed CT because of the shape of the x‑ ray beam In a single scan, the x‑ ray source and a reciprocating x‑ ray sensor rotate around the patient's head and acquire 360 pictures (1 image per degree of rotation) in 17 seconds of accumulated exposure time. The entire maxillofacial volume (13‑ cm‑ diameter field of view) is enraged, and the patient receives an absorbed dose similar to a peri apical survey of the dentition.
  • 114. The 360 acquired images undergo a primary reconstruction to mathematically replicate the patient's anatomy into a single 3D volume that comprises voxels similar to those of a Rubik's cube. Each voxel is small (0.29 mm for each of the cube faces), thus the image has a relatively high resolution.
  • 115.   The New Tom 9000 Volume scan has been extremely valuable for investigating impacted teeth, temporo mandibular joints, implant planning, and pathology. Three-dimensional scans can give valuable information about areas of the dentition, such as the position of the maxillary incisor roots relative to the lingual cortical border of the palate to plan retraction, the amount of bone in the posterior maxilla available for distalization, the amount of bone lateral to the maxillary buccal segments available for dental rather than skeletal expansion, airway information on the pharynx and nasal passages, maxillary root proximity to the maxillary sinus, and the position of the mandibular incisor roots in bone.
  • 116.   These scans also allow 3D visualization of bony defects and supernumerary teeth in patients with cleft lips or palates. axially corrected tomograms of the temporo mandibular joints can be obtained from the same scan.
  • 117. Magnetic Resonance Imaging Principles: Magnetism is a dynamic invisible phenomenon consisting of discrete fields of forces. Magnetic fields are caused by moving electrical charges or rotating electric charges. Images generated from protons of the hydrogen nuclei. Essentially imaging of the water in the tissue.
  • 118.    Magnetic Resonance Imaging The technique is based on the presence of specific magnetic properties found within atomic nuclei containing protons and neutrons, Inherent property of rotating about their axis Causes a small magnetic field to be generated around the electrically charged nuclei.     When dipoles exposed within a strong electric field Orientation in response to the field Depending on density and spatial relation Signal interpreted and image produced
  • 119. When images are displayed; intense signals show as white and weak ones as Black and Intermediate as shades of gray. Cortical bone and teeth with low presence of hydrogen are poorly imaged and appear black.
  • 120. Equipment; 1. The Gantry ;houses the patient. Patient is surrounded by magnetic coils 2. Operating console ; where the operator controls the computer and scanning procedure 3. Computer room network.
  • 121. The objectives of MRI imaging of the TMJ are;       Determine relationship between the disc and Temporal and mandibular components of the TMJ Detect inflammation, hematoma and effusion for the soft tissue components MRI clearly differentiates the soft tissue components . Short and long echo imaging of the TMJ enables identification of the positional relationships between the disc and the condyle The contrast and appearance of images can be varied by selecting the field strength and other factors. Special head holders have been designed which facilitates orientation of the patient and reduces patient movement during imaging
  • 122.  Complications; Magnetic forces and radio waves - not know to produce any biological side effects in man. Non invasive technique and can be used in most patients.  Contraindications;  Patients with cardiac pacemakers. Patients with cerebral metallic aneurysm clips. Slight movement of the clip could produce bleeding Stainless steel and other metals produce artifacts ; obliterate image details of the facial area.*  
  • 123.           Indications Assessing diseases of the TMJ Cleft lip and palate Tonsillitis and adenoiditis Cysts and infections Tumors Short comings; Inability to identify ligament tears or perforations Dynamics of tissue joint not possible Cannot be used in patients suffering from claustrophobia.
  • 124. The limiting factor in the use of MRI in Orthodontics  Apart from economic cost, the functional modality of MRI depends on the presence of large numbers of hydrogen nuclei in the tissues being imaged. Because hard tissues such as bone, enamel and dentin contain few if any free hydrogen nuclei, the use of this diagnostic tool is restricted in orthodontics to the visualization of the cartilaginous components of temporo mandibular joint
  • 125. SPIRAL CT  Recently, a new CT technique, spiral CT (SCT or volume acquisition CT), has been developed. This method has several advantages over standard CT imaging. By employing simultaneous patient translation through the x-ray source with continuous rotation of the source-detector assembly, SCT acquires raw projection data with a spiral sampling locus in a relatively short period. Without any additional scanning time, these data can be viewed as conventional trans axial images, as multiplanar reconstructions, or as three-dimensional (3D) reconstructions. Such images provide an opportunity to obtain accurate images at any arbitrary location within the volume data set.
  • 126.  The unique arrangement of the gantry and rotating x-ray source assembly radically reduces scan times. Partial body scans can be completed during a single breath hold. With standard incremental CT, small objects can be missed or their detection compromised if the patient's degree of inspiration and expiration varies from scan to scan. Moreover, multi planar and 3D image reconstructions of structures from standard incremental CT data are degraded by motion-induced misregistration artifacts
  • 127. MEASUREMENT BY TRIANGULATION  Systems that measure by triangulation analogize the geometry of mammalian stereoscopic vision. Typically such systems view the object to be measured from two positions in space and capture images from both positions on film or some digital medium either simultaneously or in rapid succession. Both biplanar and coplanar stereo systems are examples of triangulation geometry.
  • 128.  All the 3D measuring systems must be able to identify the same anatomical structure in all three dimensions. To meet this obvious requirement is frequently not as easy as it sounds, especially in stereoscopic X-ray systems. The greater the separation between the X-ray sources for two of the images of any stereo pair, the more difficult is to identify the same landmark in both images. When other factors are equal, the most powerful geometric solution for any stereoscopic measurement occurs when the angle between the two emitters and the object being imaged approximately 90 degrees.
  • 129.  However most skull structures of orthodontic interest look very different, when viewed from the lateral and frontal projections. Hence the trade off between coplanar and biplanar methods. In effect, the coplanar method sacrifices some of the mathematical power of the 90- degree ray intersection of the biplanar system to obtain a pair of images on which it is possible to locate the same physical point on both images with reduced error.
  • 130.
  • 131.  Stereophotogrammetry has evolved from old photogrammetric techniques to provide a more comprehensive and accurate evaluation of the captured subject. This technique uses one or more converging pairs of views to build up a 3D model that can be viewed from any perspective and measured from any direction. The earliest clinical use of stereophotogrammetry was reported by Thalmann - Degan in 1944 who recorded change in facial morphology produced by orthodontic treatment.
  • 132. Note that the film plane of the camera is parallel to the surface of the ground. The plane flies some desired distance and another photograph is taken, again with the camera pointing straight down figure precisely analogizes with each position of the aircraft being the equivalent of one eye. COPLANAR STEREO CEPHALOMETRY Schematic two-dimensional representation distance The region of terrain a perpendicular is dropped between the the blue lines captured by the camera along the central axis of meeting at the top is less in each of the two the camera from each of than the distance between www.indiandentalacademy.comlocations is shown.. the red lines meeting at the bottom . the two viewing positions
  • 133. FACIAL IMAGE ACQUISITION A standard stereo camera setup is used to capture the facial image pairs. The two cameras are attached to a specially designed stereo base which sits on a tripod. Each camera can translate and rotate along this base so that the convergence angle, baseline separation and height are adjustable. Digitally controlled slide projectors are used to flash separate random texture and structured light patterns onto the subject's face.
  • 134.  The CCD cameras used have a resolution of 768 x 576 pixels and these are digitized in a frame grabber able to store up to sixteen 8 bit grey level images in RAM. The cameras are pre-calibrated using precisely defined circular control point targets.  Random texture is used to aid the search for point correspondences in the matching phase. Without this large areas of the face are relatively featureless and stereo-correlation produces many false matches.
  • 135.   Image pairs acquired using texture (IL, IR) and structured light (SL, SR) projection are taken. Using digitally controlled switching between cameras and projectors, the time between capture is less than one second. Any slight subject movement is unimportant since the structured light pair is used only at the image partitioning stage. Clearly, it is not possible to capture the entire face with only one stereo pair. An additional stereo pair for the left and right sides of the face, is required followed by a step to register the three facial models. Image light projection SL projection
  • 136. How is 3D information about the surface of the face obtained? Ranging the location of two representative points on the face from a pair of cameras located a known distance apart.
  • 137. A known pattern is projected upon the subject from a light source (A) and photographed by a digital camera (B)
  • 138.  In a more recent development, a second digital camera (C), mounted between the fixed projector (A) and digital camera (B) captures a true-color image a few milliseconds after the primary image. The 3D information from the primary-camera-light-projector assembly is synchronized with the 2D pixel map from Camera C and is stored in a kind of look-up table. In this way, the location of each pixel on the monitordisplayed image from Camera C uniquely identifies the three dimensional coordinates of a particular point on the surface map generated by Camera B and its associated projector (A).
  • 139.   A dedicated computer chip built into the digital camera has the ability to distinguish different frequencies of light and hence can tell, from the color of each light ray, the direction in which that particular ray has traveled from the light projector. The projected pattern falling upon the subject is photographed by Camera 1 which is mounted a known distance from the Projector. When viewed from the perspective of the Projector, the shape of the projected pattern remains unaltered regardless of the shape of the object it falls upon
  • 140. The reconstructed representation of the face can be rotated on a standard computer monitor and the 3D coordinates of any visible point can be captured by pointing and clicking with a standard mouse or other similar device
  • 141.  The system is capable of generating dense 3-D surface maps by an image partitioning strategy and stereo matching phase, The accuracy of euclidean reconstruction has been established by analyzing images of a plaster cast model of a human face containing 13 simulated facial landmarks. This model was placed at nine different orientations and locations within the calibration space. Stereo image pairs were captured at each pose and the corresponding landmark features were detected using a centroid detection algorithm. These landmark points were then reconstructed to produce nine independent 3-D point sets. The point sets were then registered to a common coordinate frame using a standard approach, and the mean landmark positions determined.
  • 142. Stereo pairs of plaster cast model of human face bearing 13 simulated landmarks using for estimating reconstruction accuracy.
  • 143. AUTOMATIC 3-D LANDMARK EXTRACTION  The method developed for automatic facial shape change analysis is a combination of stereo-assisted feature detection and morphometric techniques. One advantage of using a stereo-based image acquisition system is that the surface texture is captured which facilitates robust 3D landmark extraction. Coupled with this, the use of morphometric techniques provides a geometrically and statistically meaningful way to characterize the shape change.
  • 144.  An active shape model (ASM) is a statistically-based technique for building geometric models of the shape and grey level appearance of a variable object in order to automatically locate new instances of the object in 2D images. It has been used successfully to locate the main facial features in images obtained under widely varying conditions . This technique is now extended to 3-D facial landmark extraction by using stereo correspondence search and surface map interpolation.
  • 145.  One-hundred and seven (107) landmark points in the stereo image were defined to represent the facial features. Some points corresponded to true landmarks, such as corners of eyes and mouth, and other points were generated automatically by sampling at equally spaced intervals along the hand digitized contour. They were manually digitized on 25 training images from the facial database and aligned to compute a mean shape and build a point distribution model (PDM). Principal component analysis on the covariance matrix of deviations from the mean shape was carried out to yield a set of basis vectors describing the main modes of shape variation. At the same time, the grey level appearance model at each shape point was constructed in the same way as for the PDM. This completes the ASM training procedure.
  • 148. Thank you For more details please visit m