Recent advances in radiographic technique /certified fixed orthodontic courses by Indian dental academy


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Recent advances in radiographic technique /certified fixed orthodontic courses by Indian dental academy

  1. 1. Recent Advances in Radiographic Technique in Orthodontics INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Introduction • In this seminar I would like to highlight on contemporary imaging techniques & innovations in imaging that in the future, are likely to greatly improve the depiction of craniofacial structures for use in diagnosis & treatment planning.It would be appropriate to first discuss the evolution of cranio facial imaging in orthodontics & review the limitations of current methods, including the two dimensional representation of three dimensional anatomy
  3. 3. Historical Perspective • In 1895 Roentgen discovered X-ray • In 1931 Broadbent introduced roentgenographic cephalometry • Cephalometrics was introduced in 1922 by Pacini &Carera.Others who contributed were Mac Gowen in 1923, Comet in 1927 &Reisner in 1929
  4. 4. Historical Perspective • Walker in 1972, Savara in 1972&Ricketts Et Al in 1972 made an attempt in the development of dentofacial imaging in 3-D individually & together with & without computerization
  5. 5. The X-ray machine • Apparatus consists of 1.Cathode-which serves as a source of electrons 2.Anode-at which the beam of high speed electrons are targeted both of these are encased with in an evacuated glass envelope or tube. X-ray are produced when electrons strike the target
  6. 6. contd • In order for the x-ray tube to function,an electrical power supply is necessary to establish high potentials across the tube for accelerating the electrons to very high speeds
  7. 7. X-ray film • Composed of two principal components, the emulsion & the base • Emulsion is sensitive to x-rays & visible light and records the radiographic image • Base is the supporting material onto which the emulsion is coated.
  8. 8. contd • The principal components of emulsion are the silver halide crystals,which are photosensitive,and a gelatin matrix that supports these crystals.An additional layer of gelatin act as a super coating to film emulsion which helps in protecting the film from damage by scratching or contamination
  9. 9. FILM BASE • Their function is to support the light sensitive silver halide grains & gelatin emulsion. They should have proper amount of flexibility to allow ease in handling the film. It should be evenly translucent • Dental x-ray film base is composed of poly ethylene terephthalate & is about 0.2mm thick
  10. 10. contd • To achieve good adhesion between the emulsion & the film base a thin layer of adhesive material is added to the base before application of the emulsion.
  11. 11. Goals & principles of Craniofacial Imaging • Assessment of pathology & any deviations from normal. • Comparison of out comes of different treatment methods at different maturational stages. • Assessment of preceeding growth or estimation of the direction or magnitude of expected growth.
  12. 12. contd • Distinguishing the effects of treatment from the expected effects of un altered growth . The ideal imaging modality maximizes the desired information & minimises the physiological risk & expense to the patient.
  13. 13. Xero Radiography • It is a specialised technique which does not make use of the wet processing technique of the image receptor after being exposed to X-rays • Image formation is achieved by photo electro static process & not by photo chemical process as in conventional radio graphy
  14. 14. contd • Found its application in the medical field in the early part of 1950’s • uses materials such as selenium that are photoconductors &conduct electric current when they interact with electro magnetic radiation such as light or x-rays
  15. 15. Advantages • No necessity of handling wet film • no requirement of dark room, processing solution & replenisher • dry & permanent image formed& cost effective • the image has a broader recording latitude • better resolution • image has granularity.
  16. 16. contd • Less radiation exposure • image have good detail &edge enhancement • visible image of air, fat,water,cartilage & bone can be seen
  17. 17. PANORAMIC RADIOGRAPHY • It is a specialized extra oral radiographic technique used to examine the upper & lower jaws in a single film. • Also called as rotational panoramic radiography or Pantomography. • In this technique, the film & the tube head rotate around the patient,who remains stationery & produce a series of individual images successively in a single film
  18. 18. Purpose & uses • For visualizing maxilla &mandible in one film • patient education • to evaluate impacted teeth & multiple unerupted super numerary teeth • detect any pathology involving jaws • to determine the extent of a large lesion • to evaluate traumatic injuries
  19. 19. contd • X’mination of patient with limited mouth opening • to identify diseases of the TMJ
  20. 20. Disadvantages • Images are not sharp • cannot be used in the diagnosis of caries • can not be used to evaluate bone loss due to periodontal disease • super imposition especially in the premolar region • structures in the anterior region not well defined
  21. 21. contd • Structures outside the image layer cannot be visualised
  22. 22. CEPHALOMETERY • Cephalograms have been widely used, both as a clinical tool & as a research technique for the study of cranio facial growth & orthodontic treatment • when a 3-D object is represented in 2-D, structures are displaced vertically & horizontally in proportion to their distance from the film or recording plane
  23. 23. contd • Ceph analysis are based on the assumption of a perfect super imposition of the RT& LT sides about the mid sagittal plane, but this is observed rare because of the facial asymmetry • Radiographic projection error causes size magnification & distortion,errors in patient positioning,& projective distortion inherent to the filmpatientfocus geometric
  24. 24. contd • Manual data collection & processing was low in accuracy & precision • Large errors are associated with ambiguity in locating anatomical land marks due to the lack of well defined out lines hard edges & shadows,as well as variation in patient position
  25. 25. contd • Hatcher in 1999 categorized sources of error related to traditional cephalometrics as those due to internal & external orientation & those related to geometry & association error • Internal orientation error refers to the 3-D relationship of the patient relative to the central X-ray beam
  26. 26. contd • External- This refers to the 3-D spatial relationship or alignment of the imaging device, patient stabilizing device & the image recording device • Geometric- this primarily refers to the differential magnification created by projection distance between the imaging device the image recording device& a 3-d object
  27. 27. contd • Association error- This refers to the difficulty in identifying a point in two or more projections acquired from different points of view
  28. 28. contd • When computers are used they may introduce errors related to pixel size, loss of color & contrast information & incomplete caliberation • In 1931 Broadbent introduced the roentgenographic cephalogram • efforts at minimizing errors & achieving accurate 3-D representation of the cranio facial complex have included computer
  29. 29. Conventional craniofacial imaging modalities • Classified as - techniques providing information on Hard tissue & those on soft tissue. In some instances, information on both hard &soft tissues may be obtained together to varying degrees
  30. 30. Hard tissue imaging techniques • Lateral & Postero anterior cephalograms • Panoramic radiography • Limited or full mouth series (FMX) consists of bite wings & periapical projections.this should be selected on a case by case basis, since the potential risks due to ionizing radiations are real
  31. 31. Indication • To assess the periodontal status and root morphology & length in adult patients From a strict orthodontic perspective these images provide several benefits including the ability to assess overall dental & periodontal health, root length shape & form ;presence of periodontal ligament space to help rule out the possiblity of ankylosis;positions of impacted or erupting
  32. 32. Hand wrist radiographs • They aid in providing an estimate of remaining growth, since a positive co relation between skeletal growth assessed by this method & facial growth has been reported. It should be used in conjunction with other indicators of overall body growth& development.
  33. 33. Tomography • General term used for technique that provides an image of alayer of tissue.The versatality of this technique makes tomography highly desirable for accurate imaging of maxillofacial structures, including the TMJ & for cross sectional imaging of the maxilla &mandible.Modern complex- motion tomographic units can be optimized to image any selected region of the facial skeleton
  34. 34. TMJ & SOFT TISSUE IMAGING • Methods may be either 2-D or 3-D • 2-D imaging includes conventional radiology (transcranial,transpharyngeal,transmaxillary submental-vertex)anthrography&fluroscopy • 3-D images include MRI, CT &most recent is stereometry
  35. 35. Corrected tomography of TMJ • Because of its ability to image the TMJ quickly &relatively inexpensively it is the most widely used technique for examining the hard tissues of jaw point • Axially corrected TMJ tomography refers to the allignment of the tomographic beam with the mediolateral long axis of the condyle to produce image layers that are parellel or perpendicular to the mediolateral
  36. 36. contd • The value of this technique is limited a priori by its two-dimensional nature, as well as by its inability to show the disc
  37. 37. Computed tomography • It uses a computer to aid in generating the image, & in allowing multiple CT slices to be stacked to give an idea of the 3-D form • CT is inefficient at producing suitable soft tissue contrast
  38. 38. MRI • It is preferred when information regarding the articular disc, or the presence of adhesions, perforations or joint effusion is desired • produces image with out ionizing radiation • expensive • para magnetic contrasting material is required in distinguishing between soft tissues of similar signal intensity
  39. 39. Arthrography • It relies on radiographic image acquisition following intra-articular administration of an iodinated contrast agent,which is placed under fluoroscopic guidance • it helps in understanding the disk position • it has an advantage over MRI in identifying the perforations between the superior & inferior joint compartments & adhesions
  40. 40. disadvantages • Increased patient risks related to radiation dosage • per cutaneous injection into the TMJ • potential for allergic reaction
  41. 41. Imaging & safety patterns • Rare earth screensfilm systemsrare earth filtrationthe use of grids ,and the use of pre patient filtered soft tissue enhancement methods • the radiation dose of panoramic films = to a single periapical or bite wing radiograph, these imaging methods may function in a screening capacity prior to deciding on the need for additional radiograph
  42. 42. Contemporary & evolving imaging technique • Images are points of information that can be produced either by the conventional analog process or by a more contemporary digital one.Intrest in digital imaging has grown for number of different reasons • In terms of necessity ,use of digital imaging allows the operator to manipulate data on a computer
  43. 43. contd • In terms of biology, this technique reduce patient radiation exposure by 30 to 98% • In terms of practicality, the elimination of hard copy X-ray film may decrease storage needs & enable teleradiology
  44. 44. DIGITAL CEPH • Considering time,tediousness&systamatic error associated with manual cephalometric data collection &processing automated Land mark identification & computerised cephalometric analysis have also recieved major attention. Human error associated with land mark location is reduced.It requires a scanner for image acquisition
  45. 45. Advantages • It allows for multiple cephalometric analyses to be performed simultaneously • It also facilitate the performance of repeated digitization of landmarks • since it is in digital form , it can be integrated with other digital information, such as intra oral & extra oral digital photographs & tomographs
  46. 46. Developments in craniofacial imaging • The future of craniofacial imaging lies in the generation of efficient ,inexpensive & detailed 3-D images for diagnosis & treatment planning .CT’s ,micro CT’s ,tuned aperature CT’s & MR spectroscopy aim to achieve many of these objectives
  47. 47. Computed tomography • Although CT scans are too x’pensive & have too high a radiation dose, they are useful in • treatment of cranio facial deformities • the outcome of surgical procedures may be visualised using sophisticated CT techniques
  48. 48. Micro computed tomography • It is principally the same as CT except that the reconstructed cross sections are confined to a much smaller area.The future of micro CT lies in its ability to sample data over a much smaller volume than full body , significantly reducing the radiation exposure.It is used to evaluate osteoblasticosteoclastic alveolar remodelling &root resorption
  49. 49. TACT • The national institute of dental research elected in 1990 to support the development of a system for generating 3D images from a machine consisting of a multitube X-ray and an X-ray CCD screen • TACT system is able to convert multiple 2D images created from multiple arbitrary projection source into a 3D image
  50. 50. MR spectroscopy • MRI works by obtaining a resonance signal from the hydrogen nucleus, & there fore is essentially an imaging of water in the tissue.MR spectroscopy works in a similar manner, but allows the imaging of any molecule or compound in the tissue.It is useful in the study of skeletal muscle physiology, tumors &healing of grafts
  51. 51. Structured light • Structured light scanning enables the topology of the face to be digitized simply & with out ionizing radiation. The result is a 3-D shell of a patients face,viewable on a computer monitor • the goal of this is to merge the facial shell & underlying X-ray data from other sources to complete the 3D structure for diagnosis &treatment planning
  52. 52. Stereo photogrammetry • It involves photographing a 3-d object from two different coplanar views in order to derive a 3D reconstruction of the images. • Modern stereo photogrammetry can be applied to solve accurate 3D skull mapping. • Using a bundle ,adjustment method,both the geometric calibration and 3D mapping functions can be elegant and accurate .
  53. 53. Laser-Doppler flowmetry • A 2mw Helium neon laser with in the flowmeter produced light with a wavelength of 632.8nm was sent along a flexible fiberoptic conductor inside the probe to the recording site.Light that contacted moving RBC was doppler shifted and some of this back scattered light was returned to the flowmeter .The flowmeter then processed the amount of light that was doppler shifted
  54. 54. Contd. returned and produced an output signal that was measured in volts .
  55. 55. Assessment of Skeletal Maturation • • • • • It can be assessed using 1)Hand-wrist X-rays 2)Frontal sinus 3)Canine calcification 4)Cervical vertebrae
  56. 56. Conclusion • The advances in imaging will substantially enhance our ability to identify conditions that are not detectable with currently available imaging techniques, and will help improve the accuracy & reliability of diagnosis & treatment
  57. 57.