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Dental caries

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Diagnosis, methods of detection, types, classification, etiology, progression of dental caries in enamel and dentin.

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Dental caries

  1. 1. DENTAL CARIES
  2. 2.  Dental caries and periodontal disease are probably the most common chronic disease in the world.  Although caries has affected humans since prehistoric times, the prevalence of this disease has gently increased in modern times on a world while basis, an increase strongly associated with dietary change.
  3. 3. DEFINITION SHAFER - “Microbial disease of the calcified tissues of the teeth, characterized by demineralization of the calcified tissues and destruction of the organic substance of the teeth”
  4. 4. STURDEVANT-“An infectious microbiological disease of the teeth that results in localized dissolution and destruction of calcified tissues”
  5. 5. CLASSIFICATION : -  STURDEVANT : - Based on - Location - Extent - Rate of progression
  6. 6.  ACCORDING TO LOCATION : - a. Primary caries b. Caries of pit and fissure origin c. Caries of enamel smooth surface origin d. Backward caries e. Forward caries f. Residual caries g. Root surface caries h. Secondary (recurrent) caries
  7. 7.  ACCORDING TO EXTENT : - a. Incipient (reversible) caries b. Cavitated (irreversible) caries  ACCORDING TO RATE OF PROGRESSION : - a. Acute (rampant) caries b. Chronic (slow or arrested) caries
  8. 8. ACCORDING TO TREATMANT & RESTORATION DESIGN- by G.V.BLACK  CLASS I  CLASS II
  9. 9.  CLASS III  CLASS IV
  10. 10.  CLASS V  CLASS VI
  11. 11. Mount’s Classification Site Size Minimal Moderate Enlarged Extensive 1 2 3 4 Pit/fissure 1 1.1 1.2 1.3 1.4 Contact area 2 2.1 2.2 2.3 2.4 Cervical 3 3.1 3.2 3.3 3.4
  12. 12.  Mount in 1998 classified the carious lesion according to site and size.  The explanation of size is :  “1” minimal involvement of dentin. Treatment by remineralization alone  “2” moderate involvement of dentin. Treatment by cavity preparation  “3” the cavity is enlarged beyond moderate size  “4” extensive caries with bulk loss of tooth structure
  13. 13.  Explanation of site:  Site 1 (pit and fissure)  Site 2 (contact areas)  Site 3 (cervical area)  Drawbacks  It becomes difficult to differentiate between different sizes  Treatment planning varies from operator to operator
  14. 14. ETIOLOGY OF DENTAL CARIES: Dental caries is a multi factorial disease.  Caries occurs in different individuals at different ages, at different sites and at different rates of progress, no single theory can explain the phenomenon of caries.
  15. 15. 1. THE WORM THEORY : - According to concept of that time, the cause of caries was thought to be invasion of ‘worms’ into teeth. Therefore the character of caries was shown as a worm over tooth surface.
  16. 16. 2. THE HUMORAL THEORY : - The four recognized humors of the body were blood, phlegm, black bile and yellow bile. The imbalance in these humors resulted in the disease process.
  17. 17. 3. VITAL THEORY : - Towards the end of the eighteenth century, it was postulated that tooth decay originated from within the tooth itself .
  18. 18. 4.CHEMICAL / PARASITIC THEORY : - In the early 19th century, a new concept was emerging, that teeth were destroyed by acids formed in the oral cavity.
  19. 19. ACIDOGENIC THEORY : - Miller (1889) propagated the concept of acid formation in the oral cavity and attributed the synthesis of acid to the action of micro – organisms. He was of the view that micro-organisms of the mouth, by secretion of enzymes or by their own metabolites degrade the carbohydrates into acids.
  20. 20. The food containing carbohydrate lodged onto the tooth surface is the source of acid production which demineralizes the enamel. Subsequently, demineralized enamel is mechanically removed by the forces of mastication. After the disintegration of enamel, the organisms and acids penetrate dentinal tubules and bring about the dissolution of dentin.
  21. 21. 6. PROTEOLYTIC THEORY : - Gottlieb (1944), the initial action is due to the proteolytic enzymes attacking the lamellae, rod sheaths, tufts and walls of tubules etc. i.e. all organic components.
  22. 22.  7. PROTEOLYSIS CHELATION THEORY : - Schatz et al (1955) describing a new theory observed that there is a simultaneous microbial degradation of organic component by proteolysis and the dissolution of inorganic part by the process of chelation.
  23. 23. The word ‘chelate’ refers to compounds that are able to bind metallic ions such as calcium, iron, copper, zinc etc. by valence bonds.
  24. 24. LEVINE’S THEORY : - Levine (1977) established the chemical relationship of enamel, plaque and the factors which determined the movement of minerals from saliva/plaque to enamel and vice-versa, which he termed as the ionic ‘see-saw’ mechanism.
  25. 25. The four factors contributing to the caries process
  26. 26. 1.THE HOST FACTOR : - A. Tooth factor a. Morphology and position in the arch b. Chemical nature B. Saliva a. Composition, pH and antibacterial activity b. Quantity and viscosity of flow
  27. 27. 2. THE MICROFLORA 3. THE SUBSTRATE OR DIET a. Physical nature b. Chemical nature 4. TIME
  28. 28. 1.The Host Factor A . TOOTH FACTOR 1) . MORPHOLOGYAND POSITION IN THE ARCH Tooth morphology is recognized as an important factor for initiation of caries.
  29. 29.  Deep pits and fissures in any tooth make then susceptible to caries because of food impaction and bacterial stagnation.  That is why the occlusal surfaces are more prone to caries.
  30. 30.  Irregularities in the arch form, crowding and overlapping of the teeth also favour the development of caries.  Partially impacted third molars are more prone to caries and so are the buccally or lingually placed teeth.
  31. 31. 2) . CHEMICAL NATURE:- It has been observed and proved scientifically, that surface enamel is more caries resistant than the subsurface enamel.
  32. 32. B . Saliva :- 1) Composition, pH and Antibacterial activity Caries prone individuals have low calcium and phosphorous levels.
  33. 33.  The pH at which any particular saliva ceases to be saturated with calcium and phosphorous is referred to as the ‘critical pH’.  Under normal conditions the critical pH is 5.5, below this value, the inorganic material of tooth may dissolve.
  34. 34. 2) Quantity and Viscosity of flow : - The quantity and viscosity of saliva has definite influence on caries incidence. Human beings suffering from decreased flow of saliva or lack of salivary secretions (xerostomia) usually experience increased rate of dental caries.
  35. 35.  The caries susceptibility has been observed to increase in numerous patients following radiation therapy  Certain drugs influence salivary flow, and in turn result in rampant caries.
  36. 36.  Since there is less or no saliva to buffer and wash away fermentation products of plaque during sleep.  The most important time for plaque removal is before sleeping to avoid caries.
  37. 37. PART - II
  38. 38. 2 . THE MICROFLORA : -  It was observed that for caries to occur, bacteria played a definite role.  Clarke (1924) discovered the species Streptococcus mutans .  Streptococcus mutans, it is considered to be the significant micro organism out of all the oral flora in occlusal and pit & fissure caries.
  39. 39.  Streptococcus mutans ferments manitol and sarbitol (synthesized insoluble polysaccharide from sucrose ) and lactic acid former which easily colonise on tooth surface .
  40. 40.  As the environment is different in deep dentinal lesion, it is certain that the flora of deep caries would be different .  The predominantly present micro – organism are lactobacilli which account for one third of the oral flora .
  41. 41.  The organisms involved in root caries are different from those in other smooth surface lesions.  Predominantly Actinomyces viscosus, A. Nocardia etc. have been isolated  Streptococcus mutans and Streptococcus salivarius have been shown to produce root caries.
  42. 42.  The following factor prove the role of bacteria in caries. Caries will not occur in complete absence of micro – organism . Caries can occure in animals even if kept on single type of bacterial growth . All micro – organism are not cariogenic .
  43. 43. 3. THE SUBSTRATE OR DIET : - a.PHYSICAL NATURE OF DIET : - Modern diet includes refined foods, soft drinks which lead to collection of debris predisposing to more caries.
  44. 44. B. CHEMICAL NATURE OF DIET : -  By chemical nature of diet we are mainly concered with the nutrient present in our meals, frequency of intake and also their cariogenic potential. The main ingredient is carbohydrate, which is accepted as one of the most important factor in dental caries process. Only refined carbohydrates are effective.
  45. 45.  For caries production following factors are responsible. Type of carbohydrate Frequency of intake Time of stagnation
  46. 46. 4 ) TIME : -  During the long intervals of undistrurbed plaque stagnation, the plaque PH is lowered favouring the production of organic acids that demineralize tooth structure.
  47. 47. DIAGNOSIS OF DENTAL CARIES
  48. 48. TRADITIONAL METHOD  Patient’s Complaint  Clinical Examination  Tactile Examination  Radiographic Examination
  49. 49. PATIENT’S COMPLAINT  Patient complaining of sensitivity to the thermal changes ,mild to moderate toothache, etc may provide a hint about the presence of dental caries.
  50. 50. CLINICAL VISUAL EXAMINATION  Careful examination of the patients teeth under clean and dry conditions using good illumination may reveal visual signs of caries like  Brownish discolouration of pit and fissure  Opacity beneath pit and fissures or marginal ridges  Frank cavitation of the tooth surface
  51. 51. A major short coming of this method is very limited for detecting noncavitated lesions in dentine on the posterior proximal and occlusal surfaces.
  52. 52. CLINICAL TACTILE METHOD  This method is based on a combination of light, mirror, and gentle probing and is used in most epidemiologic surveys  Caries is diagnosed if the tooth meets the American dental association criteria of softened enamel that catches the explorer and resists its removal or allow the explorer to penetrate proximal surfaces under moderate to firm probing pressure.
  53. 53. I. Probing has been criticized for several reasons a. It may allow transmission of cariogenic bacteria from infected sites to uninfected areas b. It can irreversibly traumatize potentially remineralizable noncavitated lesions of enamel and dentine.
  54. 54. C. And it may provide no more accuracy in diagnosis than visual inpection alone particularly in fissures and in posterior approximal surfaces
  55. 55. PART - III
  56. 56. DIGITAL RADIOGRAPHY The first dental radiograph is attributed to Dr. Otto Walkhoff of Braunschweig, Germany, who on January 14, 1896 made images of the crowns of teeth on both sides of his own jaw using silver halide emulsion on glass plates. The exposure time was 25 minutes.
  57. 57. Dr. C. Edmund Kells gave the first clinic in this country on the use of the X-ray for dental purposes. Three years later (1899), Kells was using the X-ray to determine tooth length during “root canal therapy“.
  58. 58. Digitization of ionizing radiation first became a realty in the late 1980s with the development of the RVG system by Dr. Francis Mouyen. Direct digital system have three components a) Radio component b) Visio component c) Graphy component
  59. 59. The Radio component consists of a high – resolution sensor with an active area that is similar in size to conventional film.
  60. 60.  The sensor is protected from x – ray degradation by a fiber optic shield.
  61. 61. The Vision component , consist of a video monitor and display processing unit. As the image is transmitted to the processing unit, it is digitized and stored by the computer. The unit magnifies the image for immediate display on the monitor, it also can produce colored image.
  62. 62.  The Graphy component consist, a high – resolution video printer that provides a hard copy of the screen image, using the same video singal.
  63. 63. The two major technologies presently used intraoral digital X-ray systems are as follows: 1. Solid-state detectors a. Charge-coupled device (CCD) b. Complimentary metal oxide semiconductor (CMOS) 2. Storage phosphor detectors a. Photo stimulable phosphor (PSP)
  64. 64. Working Principles of Digital Systems DigitaJ systems utilize computer technology in the capture, display, enhancement, and storage of radiographic images. Computers work on the binary number system consisting of two digits (0 and 1) to represent data.
  65. 65. These two characters are called bits (binary digits), and they form "words" of eight or more bits in length called bytes. The total number of possible bytes for 8-bit language is 2 8 = 256. The analog to digital converter (ADC) transforms analog data to digital data based on binary number system.
  66. 66.  The strength of the output signal is measured and assigned a number from 0 (black or white depending on designation) to 255 (white or black- opposite of“0") according to the intensity of the electric signal.  These numeric assignments translate into 256 shades of gray in an 8-bit system.
  67. 67.  A digital image consists of a number of pixels (picture elements), and each pixel is represented by a number corresponding to its gray level.  The pixel is the smallest picture element of the image, and the resolution of an image is directly related to the pixel size among other factors.
  68. 68. SOLID-STATE SYSTEMS
  69. 69.  Solid-state detectors (CCD and CMOS) can be indirect detectors using a scintillating screen such as Cesium Iodide or Gadolinium Oxysulfide, or (less commonly) can use direct conversion of X-ray photons to electrons (e.g., Cadmium-Telluride technology).
  70. 70. Charge-Coupled Device The CCD is composed of an electronic circuit embedded in several thin layers of silicon.
  71. 71.  The silicon chip usually is composed of an array of light sensitive pixels (picture elements), and each pixel consists of a small electron well into which the X-ray or light energy is deposited upon exposure.  Each silicon atom in the detector chip is covalent with another silicon atom.
  72. 72.  When light photons strike the silicon and the energy exceeds the strength of the covalent bond, an electron hole pair is formed.  an electric charge is established by release of electrons.  The electric charge in each "pixel" well is proportional to the incident X-ray or photon energy.
  73. 73.  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 compute monitor.
  74. 74. Complimentary Metal Oxide Semiconductor - Active Pixel Technology (CMOS-APS)
  75. 75.  CMOS chips are commonly used in digital cameras, video cameras, and computers.  CMOS detectors appear similar to CCDs, but the former use an active pixel technology, that has an active transistor built into each pixel.  This has permitted the introduction of wireless radio frequency (RF) transmission of the acquired image.
  76. 76.  The APS system eliminates the need for charge transfer between adjacent pixel wells extending the exposure latitude by suppressing "pixel blooming“.
  77. 77. STORAGE PHOSPHOR DETECTORS
  78. 78. Photo Stimulable Phosphor  The PSP imaging plate works on the principle of radiation-induced emission of photostimulated luminance.  PSPs generally contain Barium Fluorohalide crystals with small amounts of bivalent Europium atoms as an activator.
  79. 79.  When a storage phosphor imaging plate is exposed to X-radiation, the europium atoms in the phosphor crystalline lattice are ionized liberating a valence electron.  This results in the formation of electron vacancy.
  80. 80.  The valence electrons are exited to the level of conduction band where they travel freely until trapped by so-called Farbzentren Centers present in halide crystals to form metastable electrons with an energy level slightly lower than the conduction band but greater than that of the valence bond.
  81. 81.  These trapped metastable electrons constitute the latent image and their number is proportional to the number of incident X-rays.  When the latent image is exposed to the red light of solid state laser, the metastable electrons are again exited to reach high-energy conduction band where they recombine with Eu3+ atoms and return to low- energy valence bond (Eu3+ + e- = Eu2+ ).
  82. 82.  This results in the liberation of energy, emitted as blue light.  The light is registered by a photo multiplier tube and converted into an analog electric output signal that is digitized, resulting in a digital image.  Each pixel has a numeric value that is proportional to the amount to light emitted from the corresponding area of the PSP imaging plate.
  83. 83. Subtraction Radiology
  84. 84.  The basic premise of subtraction radiology is that two radiographs of the same object can be compared using their pixel values.  The value of the pixels from the first object are subtracted from the second image.  If there is no change, the resultant pixel will be scored 0; any value that is not 0 must be attributable to either the onset or progression of demineralisation, or regression.
  85. 85.  Subtraction images therefore emphasise this change and the sensitivity is increased.  However, uptake of this system has been low, presumably due to the need for well aligned images.  Recent advances in software have enabled two images with moderate alignment to be correctly aligned and then subtracted.
  86. 86. PART - IV
  87. 87. Electronic Caries Monitor (ECM)
  88. 88.  The ECM device employs a single, fixed-frequency alternating current which attempts to measure the ‘bulk resistance’ of tooth tissue.
  89. 89.  When measuring the electrical properties of a particular site on a tooth, the ECM probe is directly applied to the site, typically a fissure, and the site measured.
  90. 90.  There are also a number of physical factors that will affect ECM results.  These include such things as the temperature of the tooth, the thickness of the tissue, the hydration of the material (i.e. one should not dry the teeth prior to use) and the surface area.
  91. 91. Enhanced Visual Techniques
  92. 92. Fibre optic trans - illumination The basis of visual inspection of caries is based upon the phenomenon of Light Scattering.  FOTI is designed for the detection of proximal caries.
  93. 93.  When enamel is disrupted, for example in the presence of demineralisation, the penetrating photons of light are scattered, which results in an optical disruption.
  94. 94.  Fibre optic trans - illumination takes advantage of optical properties of enamel and enhances them by using a high intensity white light that is presented through a small aperture in the form of a dental handpiece.
  95. 95.  Light is shone through the tooth and the scattering effect can be seen as shadows in enamel and dentine, with the device’s strength the ability to help discriminate between early enamel and early dentine lesions
  96. 96. Quantitative Light-induced Fluorescence (QLF)
  97. 97.  Quantitative Light-induced Fluorescence (QLF) is a visible light system that offers the opportunity to detect early caries and then longitudinally monitor their progression or regression.
  98. 98.  The QLF equipment is comprised of a light box containing a xenon bulb and a handpiece, similar in appearance to an intraoral camera.  Light is passed to the handpiece via a liquid light guide and the handpiece contains the bandpass filter.  Live images are displayed via a computer
  99. 99.  Fluorescence is a phenomenon by which an object is excited by a particular wavelength of light and the fluorescent (reflected) light is of a larger wavelength.  When the excitation light is in the visible spectrum, the fluorescence will be of a different colour.
  100. 100.  In the case of the QLF the visible light has a Wavelength (l) of 370 nm, which is in the Blue region of the spectrum.  The resultant auto-fluorescence of human enamel is then detected by filtering out the excitation light using a bandpass filter at l > 540 nm by a small intra-oral camera.
  101. 101.  This produces an image that is comprised of only green and red channels (the blue having been filtered out) and the predominate colour of the enamel is green
  102. 102. Laser Fluorescence— Diagnodent
  103. 103.  The DIAGNODENT (DD) instrument (KaVo, Germany) is another device employing fluorescence to detect the presence of caries.  Using a small laser the system produces an excitation wavelength of 655 nm which produces a red light.  This is carried to one of two intra-oral tips; one designed for pits and fissures, and the other for smooth surfaces.
  104. 104.  The DD does not produce an image of the tooth; instead it displays a numerical value on two LED displays.  The first displays the current reading while the second displays the peak reading for that examination
  105. 105. PRIMARY CARIES
  106. 106. ACCORDING TO WHETHER THE LESION IS NEW OR AROUND MARGINS OF A RESTORATION  PRIMARY CARIES  SECONDARY CARIES
  107. 107. ACCORDING TO LOCATION  PIT & FISSURE CARIES  SMOOTH SURFACE CARIES
  108. 108. ACCORDING TO RAPIDITY OF THE PROCESS  ACUTE:  NURSING BOTTLE CARIES  CHRONIC:  RECURRENT CARIES  ARRESTED CARIES
  109. 109.  PIT AND FISSURE CARIES : - Deep pits and fissures are developmental defects found on the tooth. Pits and fissures with high steep walls and narrow bases are those most prone to develop caries.
  110. 110. They favour the retention of food debris and micro organisms and caries may result from fermentation of this food and the formation of acid. When caries occurs here, it follows the direction of enamel rods and forms a cone shaped lesion with its apex at the outer surface and its base towards the DEJ.
  111. 111. Thus, there may be a large carious lesion with only a tiny point of opening. Pits and fissures affected by early caries may appear brown or black and will feel slightly soft & “catch” a fine explorer point. The enamel bordering the pit or fissure may appear opaque bluish white, as it becomes undermined
  112. 112. SECONDARY CARIES: Secondary caries can be defined as caries around a restoration. It is also known as ‘recurrent caries’ The main etiological factor for secondary caries, is marginal leakage around the restorations.
  113. 113. Smooth Surface Caries  Develops on - proximal surfaces of the teeth - gingival third of the buccal and lingual surfaces (cervical caries)  Preceded by the formation of dental plaque  Usually initiate just below the contact point  Clinically- initially as faint white opacity or yellow brown pigmented area  Adjacent enamel appears bluish white
  114. 114. Forward Caries  Caries cone in enamel is larger or at least the same size as that in dentin
  115. 115. Backward Caries  Lateral spread of the lesion along the DEJ exceeds the caries in the contiguous enamel, caries extends into this enamel from the junction.
  116. 116. Residual Caries  Caries that remains in a completed cavity preparation  Not acceptable if- present at DEJ - prepared enamel wall
  117. 117. Incipient (reversible) caries:  First evidence of caries activity in enamel  Subsurface demineralization has occurred but no cavitation  Clinically as white opaque region  May take up extrinsic stains  May undergo remineralization- called as “caries reversibility” or “consolidation” of early enamel carious lesion
  118. 118. Cavitated (irreversible) caries:  Lesion that has advanced into dentin with broken surface  Remineralization is not possible
  119. 119. Xerostomia induced caries (radiation caries)  Complication of radiation therapy of oral cancer lesion  Radiation induced xerostomia produces caries conducive environment  Carious lesion develops as early as 3 months after onset of xerostomia  May be caused by other factors like salivary gland tumors, autoimmune diseases, prolong illness
  120. 120. ROOT CARIES Root Caries is defined as “a soft, progressive, lesion that is found anywhere on the root surface that has lost connective tissue attachment and is exposed to the oral environment”. Micro organisms invade the cementum, either along sharpey’s fibers or between bundles of fibers. Since cementum is formed in concentric layers and presents a lamellated appearance, the micro organisms tend to spread laterally between the various layers
  121. 121. ZONES OF ENAMEL CARIES
  122. 122. DIAGNOSIS OF DENTAL CARIES Diagnosis is the “ the art or act of identifying a disease from its signs and symptoms “ ( Webster’s Dictionary, 1967 )
  123. 123. TRADITIONAL METHOD  Patient’s Complaint  Clinical Visual Examination  Tactile Examination  Radiographic Examination
  124. 124. PATIENT’S COMPLAINT  Patient complaining of sensitivity to the thermal changes ,mild to moderate toothache, etc may provide a hint about the presence of dental caries.
  125. 125. CLINICAL VISUAL EXAMINATION  Careful examination of the patients teeth under clean and dry conditions using good illumination may reveal visual signs of caries like  Brownish discolouration of pit and fissure  Opacity beneath pit and fissures or marginal ridges  Frank cavitation of the tooth surface
  126. 126. A major short coming of this method is very limited for detecting noncavitated lesions in dentine on the posterior proximal and occlusal surfaces.
  127. 127. CLINICAL TACTILE METHOD  This method is based on a combination of light, mirror, and gentle probing and is used in most epidemiologic surveys  Caries is diagnosed if the tooth meets the American dental association criteria of softened enamel that catches the explorer and resists its removal or allow the explorer to penetrate proximal surfaces under moderate to firm probing pressure.
  128. 128. I. Probing has been criticized for several reasons a. It may allow transmission of cariogenic bacteria from infected sites to uninfected areas b. It can irreversibly traumatize potentially remineralizable noncavitated lesions of enamel and dentine.
  129. 129. C. And it may provide no more accuracy in diagnosis than visual inpection alone particularly in fissures and in posterior approximal surfaces
  130. 130. RADIOGRAPHIC EXAMINATION  Conventional, intraoral periapical and bitewing radiographs are employed for diagnosis of dental caries.
  131. 131. The conventional bitewing radiographic method  Conventional bitewing radiographs used for diagnosis of inter proximal carious lesion of posterior teeth.
  132. 132.  Recurrent caries at the cervical margins is best observed in bitewing radiographs since central ray is directed along the direction of cervical areas.
  133. 133.  Bitewing radiographs is useful in monitoring and evaluating the progress or arrest of caries.  Care should be taken to standardize positioning, exposure and processing conditions.
  134. 134. RADIOGRAPHY ADVANTAGES :  Discloses sites inaccessible to other methods  Detects at early , reversible stage  Depth of lesion can be evaluated and scored by index given by Grondahl et al (1977)  Permanent record  Non-invasive
  135. 135. DIGITAL RADIOGRAPHIC METHODS 1. Digital radiographic methods offer a more superior means of detecting caries than coventional methods  Digital radiographs can be obtained by two methods 1. Video recording and digitization of conventional radiograph 2. Direct digital radiograph
  136. 136.  The first direct digital radiography is Radiovisiography invented by FRANCIS MOUYEN in 1989  It uses a charged couple device which works like a miniature video camera
  137. 137.  This records the image produced by conventional x- rays and stores it in the computer memory for image processing and viewing.  ANN WENZAL journal of dental research 2002 pgs 590-593
  138. 138. DIGITAL RADIOGRAPHY ADVANTAGES OF DIGITAL RADIOGRAPHY: Less patient exposure Poor darkroom procedure- high doses, loss of diagnostic information Development is time consuming Solutions, lead foils are hazardous No new film position to learn Image can be transferred without loss of quality Image manipiulation
  139. 139. DIGITAL SUBTRACTION RADIOGRAPHY  RICHARD WEBBER was the first one to introduce the digital subtraction radiography  Here the digitization is achieved by taking a picture of the radiograph using high quality camera.  This is fed to a computer imaging device called digitizer .
  140. 140.  Two standardized radiographs produced with identical exposure geometry are used.  The first one is called the “reference image” and the subsequent images are taken for comparison.
  141. 141.  The reference image is displayed on the screen over which the subsequent images are superimposed  The difference between the original and subsequent images can be seen as dark areas
  142. 142. ADVANTAGES  Superior to conventional radiography for detecting recurrent caries  It is sensitive it can detect a 0.12mm change  Approximal caries can be visualized better  Assesses the progression of the carious lesion
  143. 143. DISADVANTAGE  EXPENSIVE  J.EBERHARD et al (caries research 2000, vol 34 pgs 219-224)
  144. 144. FIBRE OPTIC TRANSILLUMINATION Used in anteriors, premolars  ≥ bitewing radiography Mechanism Can detect En– crazing, cracks

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