Conservative Dentistry and Endodontic Imaging

This is very important topic for postgraduate students of Conservative dentistry and endodontic branch. This seminar will help them learn and understand the topic better. Thank you

1. 1 Endodontic Imaging Presented by- Dr Anuja Dhumal

2. contents Introduction History Application of radiography to endodontics Limitations of radiographs Technology systems Traditional Digital technology

3. Cone positioning- 1. Vertical Angulation 2. Horizontal Angulation Extraoral Film Placement- Digital Radiography- Working Principles of Digital Intraoral Systems- CMOS CCD Storage Phosphor Detectors- 3

4. Xeroradiography Uses Advantages Disadvantages Subtraction radiography Working principle Disadvantages Computed tomography Working principles Advantages over conventional film Uses

5. Cone beam computed tomography – Field of view and Spatial resolution Applications in endodontics Advantages Magnetic Resonance Imaging Operating Principles of MRI Use of MRI in endodontics Advantages and Disadvantages of MRI use Conclusion References 5

6. Endodontic treatment relies on a series of images made at different stages of the treatment. These images provide important clues about hard and soft tissues of the teeth, including the pulp chamber and root canals. Radiographs are the ‘eyes’ of the dentists when performing many procedures. However, conventional radiographic techniques have certain limitations. Digital radiography is the latest advancement in dental imaging and is slowly being adopted by the dental profession. 6 Introduction

7. Digital image incorporates computer technology in capture, display enhncement , and storage of direct radiographic images. It offers some distinct advantages over film, but like any emerging technology, it presents new and different challenges for the practitioners to overcome. 7

8. 1895- German professor Wilhelm Roentgen first developed the cathode rays. Dr. Otto Walkoff took the first dental radiograph for himself. 1899 - Dr. C. Edmund kells gave the first clinic in the U.S.A on the use of X-ray for dental purpose. 1901 – Radiographs were used to check the adequacy of root canal filings. Dr. Price is credited with developing the bisecting angle technique, whereas kells described what today is called the Paralleling technique . 8 History

9. 9 Left: X-ray of Anna Bertrand Rontgen’s hand (1895-12-22). Right: X-ray of Albert von Kolliker’s hand (1896-01-23). In those days knowledge about the dangers Of exposing living tissues to x-rays was very less. Rontgen convinced his wife as a test subject. Anna rontgen , has gone down in history as the first person that underwent x-ray radiography . One can see drastic improvements in image quality between the two hand radiographs, taken only one month apart.

10. Two weeks after the publication of Rontgen’s discovery, the German dentist Otto Walkhoff acquired a radiograph of his own teeth with the help of Fritz Giesel . An exposure time - 25 min was used . ( diagnostic quality) 10 Left: Otto Walkhoff . Right: Walkhoff’s dental radiographs.

11. In March 1896 at the Physical Society of Frankfort, Konig published an overview of his work, containing radiographs of the anterior teeth of upper and lower jaw. 11 Konig’s dental radiographs The radiographs, in his words: “ are not only able to prove the position and the form of the fillings in the teeth but we are also able to examine parts of the teeth which are sticking into the jaw bones ...’. (W. König , as quoted by Forrai )

12. 12 Skiagraph showing upper and lower jaw teeth. William J. Morton presented intraoral radiographs acquired of a dry skull at a lecture for the New York Odontological Society on 24 April 1896.

13. 13 Early X-ray tubes had to be recalibrated before each exposure. Recalibration was done by placing the operator’s hand in front of a fluoroscope and adjusting the tube current until a clear radiograph was shown . Furthermore , it occurred that dentists held the intra-oral plate or film in place using their own fingers during the minutes-long exposure. It is to no surprise that many of the early adopters of X-ray imaging had to pay a heavy toll for their groundbreaking work.

14. The first lesion started appearing on his left hand -1908 Multiple lesions not responsive to the treatment- series of amputation.- Continued his work - custom made instruments that could be attached to the left hand- hand amputation 1926. Inventions- Suction apparatus, He suggested conservative root canal therapy using radiographs. published - reports on the effects of radiation, distinguishing between early and late effects 14

15. It is made up of three components- Control Panel Extension Arm Tube head 15 Dental X-ray Machine

16. X-ray Tube Head Metal Housing- It surrounds the x- ray tube and transformer. It protects the x- ray tube. Insulating oil- It prevents overheating by absorbing the heat created by the production of x-rays. X-ray tube- main X-ray generating system. Aluminium Disks- They filter out non- penetrating longer wavelength x-rays. 16

17. Total filtration is regulated by the state and federal law ( U.S.A) At or below 70 kvp - 1.5mm of A luminium thickness. Above 70 kvp - 2.5mm of Aluminium thickness . 5. Lead Collimator- It is a lead plate with a central hole that fits directly over the opening of the metal housing where the x- rays exit. It restricts the size and shape of the x-ray beam and thus reduce the exposure to the patient. Types- 1. Round 2. Rectangular. 17

18. 6. Position indicating device (PID) – -It is an extension of the tube-head and it shapes the x-ray beam. Types- Conical Rectangular Round Conical PID appears as closed, pointed plastic cone- It produces scattered radiation. Long and rectangular PID is preferred because of less divergence of x-ray beam and reduces patient exposure. 18

19. Short Cone 8 Inches X- ray machines (PID) Long Cone 16 Inches

20. It consists of- A leaded glass housing A negative Cathode A Positive Anode 20 X-ray Tube

21. Leaded glass housing- It is a leaded glass vaccum tube that prevents x- rays from escaping in all directions. It has a central window that permits the x-ray beam to exit and directs towards the aluminium disk, lead collimator and PID. 21

22. A Negative Cathode- It is composed of two parts- Filament. 2. Focusing Cup. 1. It is made up of coil of tungsten wire. It is mounted on two strong stiff wires that carries the electric current. The hot filament emits electrons that are separated from outer orbit of tungsten – “Thermionic emission”. 2. It is a reflector cup of molybdenum and houses the filament. 22

23. Positive anode- It consists of wafer thin tungsten plate ( target) embedded in a solid copper stem. Its purpose is to convert the kinetic energy of electrons generated from the filament into x-ray photons. 23

24. Tungsten is usually selected as a target material because of- High atomic number High melting point ( 3380 degree celcius ) Low v apour pressure Methods of heat dissipation- Conduction- Copper stem Convention- Oil surrounding the tube. Rotating Anode. 24

25. Target Size- Sharpness of the radiographic image increases as the size of the radiographic source decreases. As the focal spot becomes smaller, heat generated per unit target area becomes greater. In order to derive a benefit from small focal spot and distribute the bombarding electrons over greater surface area of large target, the target is placed at an angle to an electron beam. Effective focal spot will be smaller than the actual focal spot.( Sharper image and effective heat dissipation Target inclination- 20 degrees- “Line focus principle”– angle of truncation 25

26. Paralleling Technique- The x-ray film is supported parallel to the long axis of the teeth and the central x ray beam is directed at right angles to teeth and film. To achieve this, the film must be placed away from the tooth and towards the middle of the oral cavity. Because the film is placed away from the tooth, image magnification and loss of definition results. To compensate for image magnification the target film distance must also be increased. 26 Techniques used in periapical radiography

27. It requires the use of film holders to stabilize the film . Examples of commercially available film holders are- Rinn XCP Precision film holders Stable bite blocks- disposable film holders EEZEE- Grip film holders Hemostat with bite block 27 Rinn XCP

28. It is also known as short cone technique. It is based on- “ the rule of isometry ”. ( which states that the two triangles are equal if they have two equal angles and share a common side.) 28 Angle bisecting technique

29. Horizontal angulations- it is obtained by directing the central ray perpendicular to the curvature of the arch and through the contact areas of the teeth. 29 Horizontal angulations for: Maxillary anterior teeth – straight facial Maxillary premolars and molars – mesial angle Mandibular incisors – distal angle Mandibular premolars – mesial Mandibular molars - distal

30. Mandibular Molars Horizontal cone angulations A, Central ray directed at right angle to film positioned parallel to arch. B, Limited information is gleaned from the radiograph because of superimposition of structures and canals.

31. A, Central ray directed at 20 mesially to film positioned parallel to arch. B, Two canals are now visible in both roots of the first molar

32. Disclosing canals by radiography. Figure Right angle horizontal projection reveals four files in separate canals superimposed. Horizontal angulation varied 30 mesially reveals all four canals and file short of working length in mesiolingual canal .

33. A, Central ray directed at right angle to film positioned parallel to arch. B, Radiograph reveals one canal in each premolar , although abrupt change in density may indicate bifurcation. Mandibular premolars

34. Central ray directed at 20 mesially to film, parallel to arch. B, In first premolar, two canals that are clearly visible (arrow ) probably reunite,

35. A, Central ray is directed through maxillary molar at right angle to inferior border of film. M alar process will superimpose over first molar. B, Superimposition of first molar roots, sinus floor, and malar process confuse the diagnosis. Maxillary molars

36. A, Central ray directed at 20 mesially skirts malar process, projecting it distally. B, Distobuccal root is cleared of palatal root and malar process is projected far distal, all three roots are clearly seen .

37. A, Central beam projected 20 from the distal. B, Mesiobuccal root of the first molar is isolated and second and third molars are cleared of malar process, which is projected forward . Sinus floor may be ‘‘lowered’’ or ‘‘raised’’ by changing vertical angulation .

38. A, Horizontal right-angle projection produces illusion that maxillary first premolar has only one canal. B, Varying horizontal projection by 20 from the mesial separates two canals. Buccal canal is distal (MBD ). Maxillary premolar

39. A, Film placement for modified parallel technique. Horizontal central beam projection at right angle to film. B, Single canals seen in central incisors with only suggestion of two canals in lateral incisor. Mandibular anterior teeth

40. A, Film is positioned for canine radiograph. Horizontally, central beam is projected at right angle to film. B, Canine image is single straight canal, but incisor image reveals bifurcated canals that reunite in narrow tapered root.

41. 41 Vertical angulations-

42. BISECTING ANGLE TEBCHNIQUE PARALLELING TECHNIQUE Diffusion and distortion of image Sharp details are obtained Increased chances of elongation or shortening Image is of same shape and size Distorted images of teeth due film bending Image of the teeth anatomically accurate Shadows of alveolar bone tend to fill the interproximal spaces Alveolar crest seen in true relationship to the teeth More vertical angulation Less Superimposition of shadow of zygomatic arch on teeth Appears above the apices of the molar teeth Unnecessary exposure to the patient’s finger (if film is held) Use of film holding devices minimizes such error Can be used in cases with shallow palate Apices of the teeth may be cut off Buccal roots of premolars and molars are foreshortened No such errors Coning off of the image Aiming rings minimizes such error Cannot be reproducible Reproducible 42

43. Aid in Diagnosis- Hard tissue alterations in the teeth and periapical structures. Determine the number, location, shape, size and direction of roots and root canals. Assess anatomy, size and alteration of pulp chamber. Detect procedural errors- perforations, ledges, transportation and instrument separation. Locate root tips prior to surgery . 43 Application of radiography to endodontics

44. Aid in the evaluation of obturation . Presence of any tooth fragment and other foreign bodies following traumatic injuries. Evaluate , in follow up films the outcome of treatment. Confirm, following root end surgery and before suturing, that all tooth fragments and excess filing material have been removed from the apical region and the surgical flap. 44

45. Dimensions of radiographs are easily distorted through improper technique, anatomic limitations or processing error. Bucco -lingual dimension is absent on single film. Various states of pulpal pathosis are indistinguishable on x-ray shadows. Periapical soft tissue lesions cannot be accurately diagnosed by radiographs. For proper diagnosis radiographic interpretation should always be integrated with detailed medical and dental history, clinical examination and pulp testing procedures. 45 Limitations of radiographs

46. Useful for patients  cannot accommodate or tolerate intra oral films Gagging or trismus Special positioning of cone and film Extra oral film placement

47. Maxillary molar, cone is positioned a negative 45 degree to the occlusal plane Mandibular molar, cone is positioned a negative 35 degree to the occlusal plane

48. The advent of digital imaging has revolutionized radiology. A number of forces are driving the shift from film to digital systems. The detrimental effects of inadequate film processing on diagnostic quality and the difficulty of maintaining high quality chemical processing are well documented problems in dental radiography. Digital Imaging

49. 49 Demonstration of the diversity of available intraoral X-ray sensors.

50. RVG system (radio visuography ) Four main components An X-ray set with special timer An intra oral sensor A display processing unit A printer

51. Components of the RadioVisioGraphy (RVG )-showing the solid-state electronics board with charge-coupled device (CCD) chip, the scintillator , and the fiber optic plate used to reduce the size of the image to the size of the CCD. Primary tooth of Mouyen’s daughter ., The first ‘‘clinical’’ RVG image achieved by Dr . Mouyen . , Commercial version of the RVG with Mouyen himself in the blue gown. 51

52. Two types Direct digital imaging Indirect digital imaging Types of digital imaging

53. D igital imaging Components  An X-ray source, an electronic sensor, a digital interface cord, a computer with an analog to- digital converter (ADC), a screen monitor, software and a printer.

54. Sensor placed in the mouth and exposed to x-rays Sensor captures image and transmits to computer Analog information is converted into digital by ADC (analog digital converter) Within seconds the image appears on computer screen. Software used to enhance and store image

55. Indirect digital sensors are either  A charge-coupled device (CCD)  C omplementary metal oxide semiconductor active pixel sensor (CMOS-APS).

56. It is so named because this technique still uses a scintillator to convert x-rays to light. Charge C ouple Device (CCD) Most common image receptor First developed in 1960 Introduced to dentistry in 1987 Used in  fax machines, home video cameras, microscopes and telescopes 56 Indirect Conversion

57. x-ray photons Light Photons Scintillator Electric charge Fiber optic plate Electrical charge is read out digitally before finally being sent to an image processor

58. Each silicon atom in the detector chip is covalent with another silicon atom . When light photon strikes the silicon and the energy exceeds the strength of the covalent bond, an electron hole pair is formed Silicon chip  usually composed of an array of light sensitive pixels  consists of a small electron well into which the x ray or light energy is deposited upon exposure . Charge coupling is a process by which the electrons from one well are transferred to another in a sequential manner ( bucket brigade)

59. The charge of each pixel is converted from an analog electric signal representing the energy absorbed by the solid state chip to a digital signal representing the discrete numeric pixel values for image display on a computer screen.

60. 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. Complementary metal oxide semiconductor/active pixel sensor CMOS/APS

61. In a CMOS chip, more of the electronic components controlling the conversion of photon energy into the electronic signal are incorporated into the chip itself. This simplifies the manufacturing process and thus, reduces the costs of production. However, most digital cameras on the consumer market are based on CCD technology.

62. 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.

63. T he 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. Photostimulable phosphor plates

64. 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. As imaging systems became more sophisticated, other techniques for capturing the digital image from an analog were developed.

65. The image is captured on a phosphor plate as analog information and is converted into a digital format when the plate is processed. Indirect Photostimuable Phosphor Plates

66. First introduced in 1981 by the Fuji Corporation (Tokyo, Japan). 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 fluorohalide compound. The sequence involved in the formation of a photostimulable phosphor (PSP) image.

67. 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.

68. 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. Finally, the receptors must be erased by exposure to white light before reuse.

69. A major advantage of the PSP image receptor is that it is cordless. This significantly impacts the ease of receptor placement. The receptor is approximately the same size as conventional film and is somewhat flexible.

70. These sensors must also be kept in an infection control barrier because the imaging plate cannot be sterilized. PSP technology is used for intraoral as well as extraoral imaging. Most studies report comparable utility when evaluating conventional film images with PSP images.

71. Reduced time between exposure and image formation. Reduced radiation dose per image. Multiple exposures, from various angles. Elimination of chemical processing and disposal of spent chemicals . Images can be duplicated any number of time without any loss of image quality. Images can be stored and retrieved electronically and can be transmitted electronically for referrals and other purposes . Dynamic nature of the image with the ready option of post-imaging enhancements . 72 Advantages of Digital X-Ray Imaging

72. Digital systems also have measurement tools. (e.g ., an endodontic instrument of known length placed in a root canal) can accurately measure, for example, the root canal working length . Reusable detector reduces expenditure on consumables . With DICOM image file usage, digital images can provide greater security regarding radiographic image integrity and tags include such information as patient name, date of exposure. Wired detectors have an advantage when working on special need patients as the wire makes swallowing or ingesting the detector unlikely. 73

73. Relatively high initial investment cost . Issues related to infection control as the detectors cannot be autoclaved . Solid-state detectors are somewhat thicker and more rigid (however, this can also be an advantage in preventing disproportionate distortion from film bending ). Packaged PSP imaging plates (IPs) are thinner than prepackaged analog intraoral X-ray films and may not be held firmly in position in film holders . 74 Potential Disadvantages of Digital Imaging over Films

74. As most current versions of CCD and CMOS detectors are wired, this could create patient psychological discomfort . Competency using software may take time to master . With PSPs, the intraoral imaging plates have been prone to mechanical degradation necessitating replacement of plates to sustain image quality. Mishandling can cause mechanical damage with high replacement costs for CCD and CMOS detectors . 75

75. Digital subtraction radiography is a technique that allows us to determine quantitative changes in radiographs. A radiographic image is generated before a particular treatment is performed. At some time after the treatment, another image is generated. The two images are digitized and compared on a pixel-by-pixel basis . Digital Subtraction Radiography

76. The resultant image shows only the changes that have occurred and “subtracts“ those components of the image that are unchanged. Image comparing baseline to follow-up images made at 3, 6, and 12 months following endodontic therapy . Column 3 indicates subtraction of respective follow-up images from the baseline radiograph. Progressive remineralization of the radiolucency at the apex of the distal root of the first molar .

77. Areas with mineral loss  displayed in darker shades of gray, while areas of gain appear lighter than the background A subtraction image is a two dimensional display of 3-D structures. In order for DSR to be diagnostically useful, it is imperative that the baseline projection geometry and image intensities be reproduced.

78. If the exact projection geometry and receptor placement are not recreated, the changes in the subtracted image will demonstrate the effects of mis -registration rather than the effects of therapeutic intervention.

79. Xeroradiography It is made up of 9.5 by 14 inch sheet of aluminium . A thin layer of amorphous selenium photoconductor. An interface layer- Aluminium oxide. An overcoating -cellulose acetate. It uses Photoelectric process instead of photochemical process.

80. 81 Working Principle The XC plate Is charged to a high positive potential by corotron . It is then placed in a cassette and used in manner similar to a conventional film. When x rays strike the selenium , photoconduction occurs and this produces a charge image Of the part to be examined. The image is made visible in a processor by using a liquid toner. The resultant powder image is subsequently transferred to a special paper And fixed there to form a permanent image.

81. soft tissues on xeroradiographic films have well defined outlines that may permit confident evaluation of the soft tissue height and contour. Xeroradiographs provide greater overall soft tissue detail making possible evaluation of its density, texture, and contents. T he technique reveals soft tissues calcifications which are not easily discerned in conventional radiographs. This property may be employed in endodontics to visualize early pulpal calcifications. It gives detailed visualization of lamina dura , bony trabeculae , fine metal instruments like files, broaches etc , root apices, PDL spaces. 83

82. Wide applications -Management of neoplasm of laryngopharyngeal area, joint region, as well as an aid in cephalometric analysis. Reduced exposure to radiation hazards - Because there is no need to make multiple exposures as tissues of different densities and thicknesses can be recorded in one exposure, patient is at a very low risk of radiation hazards . Economic benefit - An eight fold increase in cost is saved over conventional radiography . 84 Advantages

83. Better ease and speed of production -So far as no special skills are required for office copying machine. High resolution- The strengths of the fields are smaller at the centre of charged ones than at the edge, resulting in a greater number of powder particles collections peripherally than in central charged areas. This greatly enhances local contrast which, in turn, improves resolution and image quality. 85

84. Fragile selenium coat- the layer is quite easily scratched . Slower speed -Comparatively , xeroradiography has a lower speed than halide radiographs . Technical limitations- -> High radiation dose is needed for extraoral techniques -> Positioning difficulties especially in the most posterior areas of the mouth -> Image artifacts are more. 86 Disadvantages

85. In 1972 Godfrey hounsfield invented Computerized axial transverse scanning. A CT scan makes use of computer processed combinations of many x-ray images taken from different angles to produce cross sectional (tomographic) images. Computerized tomography

86. Claimed to be 100 times more sensitive than conventional x-ray system. CT scanner consists of a radiographic tube that emits a finely collimated, fan shaped x-ray beam directed to a series of scintillation detectors or ionization chambers. Depending on the scanner's mechanical geometry, both the radiographic tube and detectors may rotate synchronously about the patient

87. The detectors forms a continuous ring about the patient and the x-ray tube may move in a circle within the detector ring. More recently CT scanners have been developed that acquire image data in a spiral or helical fashion. lt is reported that, compared with incremental CT scanners, spiral scanners provide improved multiplanar image reconstructions, reduced examination time (12 seconds versus 5 minutes) and a reduced radiation dose (up to 75%).

88. Many scans are progressively taken as the object is gradually passed through the gantry. They are combined together by a mathematical procedure known as tomographic reconstruction. 90 Image Reconstrruction

89. Completely eliminates the superimposition of images of structures outside the area on interest. Because of the inherent high contrast resolution of CT, differences between tissues that differ in physical density by less than 1% can be distinguished; conventional radiography requires 10% difference in physical density to distinguish between tissues. Advantages over conventional film

90. Time consuming Expensive for routine clinical use. High radiation exposure. Expensive equipment hence not always accessible. 92 Disadvantages

91. Evaluation of extent of any suspected pathology in the head and neck, including tumors, cysts and infection. Presence and absence of root canal filling materials and metal posts. Extension of the maxillary sinus and its proximity to root apices. Determination of location and extent of facial fractures. Radiographic presurgical evaluation for implant placement. Uses in Dentistry Axial CT and coronal CT of the mandible showing the brown tumour as a mass of the left hemimandible .

92. It uses a round or rectangular cone shaped x-ray beam where an x-ray source and a reciprocating array of detectors simultaneously moves around the patients head. Single projection image – “Basis image”. Series of such basis images – projection data software converts this data into 3D volumetric data. Final image. 94 Cone Beam Computed Tomography

93. 95

94. CT vs CBCT Fan shaped x-ray Beam Cone shaped x-ray Beam 96

95. Traditional CT uses high output, rotating anode x-ray tube. CBCT utilizes a low power, medical fluoroscopy tube that provides continuous imaging throughout the scan. 97

96. Produces a single slice image per scan. E ach slice must overlap slightly in order to properly reconstruct the images. Produces the complete volume image in a single rotation. 98

97. CT is slower due to spiral motion. Scan time is longer. CBCT-The single turn motion image- quicker than traditional CT. 99

98. CT has high radiation dose. The average medical CT can reach levels of 1,200-3300 Microsiv . CBCT has lower radiation dose as a result of no overlap of slices. Radiation exposure- 36 microsieverts . 100

99. CT- To collect adequate information there is overlapping of radiation. No overlap of slices. 101

100. CT- only one jaw can be visualized at one time. - High contrast resolution. - Cost is high. -Can cause claustophobia . CBCT- Both jaws can be imaged at the same time. - Poor contrast resolution, thus soft tissues cannot be viewed . - Cost is less. Open design of CBCT eliminates claustophobia and greatly enhances patient comfort and acceptance. 102

101. Uses non ionizing radiation- to produce high quality cross sectional images of the body. Patient  placed inside large magnet  induces strong external magnetic field Nuclei of many atoms in the body  align with the magnetic field- to transverse plane. This produces a rotating magnetic field from the body, detectable by the scanner and used to construct image by a computer. Magnetic resonance imaging

102. Loosely bound hydrogen atoms- soft tissues and liquids- can align with external magnetic field and produce a detectable signal.-Bright color Hard dental tissues fail to produce a usable signal as they cannot align themselves.-dark color 104 MRI IMAGE CBCT IMAGE

103. Advantages of MRI It offers the best resolution of soft tissues. No ionizing radiation is involved with MRI. Direct multiplanar image is possible without reorienting the patient

104. Disadvantages Long imaging times, reducing patient comfort. Requires high financial resources for setup. Different types of hard tissues such as enamel,dentine cannot be differentiated from each other and from metallic restorations.-radiolucent. A strong magnetic field has the capability to pull heavy objects towards the scanner at very high velocity- “projectile effect”.

105. Differential diagnosis between a granuloma and a cyst may be important in the management and predicting the outcome of the endodontic treatment. Traditional radiographs, CT, CBCT are not good guides. In recent years ultrasound real time echotomography , safer method used to supplement traditional radiology, in the study of apical periodontitis. 107 Ultrasound

106. 108 Basic principle When quartz or a synthetic ceramic crystal is exposed to AC current. Electrons cause a change In the structure of its grid. This change emits mechanical Energy in the form of US waves. As the US waves passes through or interacts with tissues It is attenuated by a combination of absorption, Reflection, refraction and diffusion. Sonic waves that are reflected back(echoed) towards the transducer cause a change in the thickness of piezoelectric crystal, which in turn produces an electrical Signal, that is amplified , processed and finally displayed as an image on a monitor.

107. 109 The production of ultrasound images is based on the generation and reflection of ultrasound waves.

108. 1 . Alveolar bone, if healthy, is hyperechoic because it exhibits a total reflecting surface that appears white in the image. 2. The roots of the teeth are also hyperechoic and appear as an even whiter shade than bone . 3. Solid lesions in the bone are echogenic or hypoechoic presenting various intensities of echoes and appear as different shades of gray . 4. A bone cavity filled with clear fluids (i.e., serous) is anechoic (or transonic) because it has no reflection and it appears dark . 110

109. 5. A bone cavity filled with fluids - degrees of darkness, depending on the contents of the fluid. 6. The irregular bone (resorbed) around a lesion shows a dishomogeneous echo . 7. The reinforced bony contour of a lesion is usually very bright ( hyperechoic ) . 8. By applying the CPD to the examination procedure, the presence and direction of blood vessels around and within the lesion can be detected. 9. The mandibular canal, the mental foramen, and the maxillary sinus can often be distinguished and appear mostly transonic. 111

110. 112 Ultrasound real-time imaging of two different lesions in the jaws. A1, Periapical lesion (granuloma) as seen in the ultrasound image it is an ‘‘echogenic’’ area where echoes are reflected at different intensities. A2, The same lesion after the application of color power Doppler. The colored spots represent the vascularization within the lesion. B , Ultrasound image of a cystic lesion , it shows an ‘‘anechoic’’/’’transonic’’ cavity; the reinforced lower bone contour of this lesion is hyperechoic ’’ .

111. Advantages Ultasound imaging showed enough potential sensitivity to allow the disctinction between a cyst and a granuloma, to define a mixed type of lesion. Immediate and long term response to the treatment-The application of CPD has the sensitivity to detect the presence of newly formed vessels. Non-invasive painless method and has lower biological adverse effects. 113

112. Drawback- Images interpretation is very critical and needs an expert eye, and there are not landmarks to help distinguish the position of a lesion within a given area of mouth. 114

113. Recent advances in imaging technologies have revolutionized dental diagnostics and treatment planning. Correct use of technology and their correct interpretation following ALARA principle and cause effectiveness, newer radiographic techniques can help to detect pathologies in very early stages, which ultimately help to reduce morbidiy and mortality and improve the quality of life of the patient. Digital radiography is a reliable and versatile technology that expands the diagnostic and image sharing possibilities of radiography in dentistry. CONCLUSION

114. Endodontics –Ingle 5 th and 6 th edition Pathways of pulp—Cohen , 10 th edition A guide to dental radiography—Rita and Bourne Oral radiology—White and Pharoah , 5 th edition REFERENCES

115. Digital Radiography:An Overview. The Journal of Contemporary Dental Practice, Volume 3, No. 4, November 15, 2002 Dental Imaging - advances in conventional and digital radiography. Clinical Update, 2003, Vol. 25, No. 4 Filmless imaging: The uses of digital radiography in dental practice. PAUL F. VAN DER STELT, J Am Dent Assoc 2005;136;1379-1387

116. 118 THANK YOU