Radiographic Interpretation

RADIOGRAPHIC INTERPRETATION DR. ZINNIA PATEL

What is dental radiograph ? Dental radiography : It is the art of producing an image or picture for intra-oral or extra-oral structures on a dental film using X-rays.

Objectives: 

The students should know the normal anatomy of the tooth under dental radiograph.

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The students should interpret the pathology of the tooth under dental radiograph.

It is the traditional method to asses the destruction of alveolar bone associated with periodontitis. CONVENTIONAL RADIOGRAPH CAN BE USED TO EVALUATE         

Bone levels Bone loss – even or angular patterns Intra(infra) – bony defects Root morphologies ⁄ topographies Furcation radiolucencies Endodontic lesions Endodontic mishaps Developmental anomalies Root length and shape(s) remaining in bone

CONVENTIONAL AND DIGITAL

RADIOGRAPHS

INTRA ORAL

EXTRA ORAL

IOPA,BITEWINGS &OCCLUSAL

OPGS

CONVENTIONAL RADIOGRAPHS INTRA ORAL RADIOGRAPHS

Intra oral periapical radiographs

Paralleling technique

Also called as “right angle” or “long cone technique”. X-ray film is placed parallel to long axis of tooth and central ray of x-ray beam is directed at right angle to teeth & film. Preferable technique for periodontal use.

Bisecting angle technique Central ray is directed at right angles to a plane bisecting the angle between long axis of teeth & film.

Projection Maxilla Mandible Projection Maxilla Mandible Incisors +40 degrees -15 Incisors +40 degrees -15 degrees degrees Canine +45 degrees -20 degrees Canine +45 degrees -10 -20degrees degrees Premolar +30 degrees Premolar +30 degrees 2-5 -10degrees degrees Molar +20 degrees Molar +20 degrees 2-5 degrees

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Periapical radiograph:

It is the most frequently used intra-oral view radiograph, which shows the entire tooth and surrounding structures on the film.

Need for prescribing peri-apical dental radiograph 

Extent of carious involvement in the tooth

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Interproximal decay under the contact point

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Periapical pathological changes

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Traumatic injuries to dento-alveolar process

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Periodontal diseases

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Dental anomalies

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Occult diseases

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Prognostic assessment during treatment planning

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Post obturation assessment of endodontic therapy

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Working length measurement during root canal therapy

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Implants

Normal Radiographic Anatomy (Peri-apical)

Normal radiographic anatomy

ENAMEL Most radiopaque structure 

DENTINE Slightly lighter than enamel 

PULP CAVITY Radiolucent lines within the tooth 

ALVEOLAR CREST Gingival margin of the alveolar process appear as a radiopaque line 

PDL SPACE Narrow radiolucent line around tooth surface 

LAMINA DURA Radiopaque line representing tooth socket 

Radiographic interpretation:

Interpretation : 

Step by step analytical process that provides an exact idea of the clinical problem and helps to achieve the final diagnosis of any particular lesion.

The importance of interpretation: 

Radiographic interpretation is an essential part of the diagnostic process. The ability to evaluate & recognize what is revealed by a radiograph enable us to detect diseases, lesions & conditions which can’t be identified clinically.

Steps of interpretation     

Localization. Observation. General consideration. Interpretation. Correlation.

Localization:    

Localized or generalized Position in the jaw Single or multiple Size

Observation: 

All shadows, other than the localized shadows of the normal landmarks must be observed.

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For example: shadows in crowns, cervical area, roots, restorations, size of root canals, periodontal membrane space, periapical area, alveolar crest, foreign bodies, integrity of bone

General consideration: 

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A radiograph shows only 2 dimensions of a 3 dimensional object (width and height but not the depth) Cervical burnout: usually appears as cervical Radiolucency and misinterpreted by caries; this occurs due to less density and more penetration of rays. Pulp exposure: never to be determined from radiograph but only the proximity to the pulp.

Interpretation: 

Studying the features of teeth and bone:

Teeth Study the whole tooth,(crown, root, enamel, pulp), number of teeth and finally supporting structures, (Periodontal membrane space, lamina dura , alveolar crest)

Bone: Changes in bone may include: 1- Changes in density. 2- Changes in the margin 3- Changes inside the lesion. 4- Effect on surrounding tissues. 5- Changes in structure

Correlation: 

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The final step is to correlate all of the radiographic features to reach a radiographic differential diagnosis. Then to draw a final diagnosis, we have to correlate other data as case history, clinical examination, and other diagnostic aids with the radiographic differential diagnosis

Metallic restoration

enamel

Dentine Pulp chamber Root canal

P/d ligament alveolar bone

Lamina dura

PERIAPICAL RADIOGRAPH INTERPRETATION:

Enamel 

Caries of the enamel : appears as radiolucent area

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Enamel hypoplasia: appears as radiolucent area surrounded with radiopaque margins

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Amelogenesis imperfecta: all the enamel appear as radiolucent area

Dentin: 

Caries of the dentin: appears as radiolucent area

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Dentinogenesis imperfecta: dentin appear as radiolucent area surrounded by faint radiopaque margins

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Dense in dente: appears as radiopaque structure within the tooth surrounded by radiolucent margin

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Internal resorption: radiolucent lines on the apex or lateral side of the root dentin

Pulp: 

Calcification of the pulp: appears as a localized area of radiopacity, if the calcification is generalized it appears as a generalized area of radiopacity

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Shell tooth: appear as wide pulp chamber

Cementum: 

Hypercementosis: appear as radiopaque area covers the cementum line

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Cementoma: appears at the apex of the tooth as a radiolucent area in its early stages and converted into radiopaque at the terminal stages

PDL space: 

Normally appear as radiolucent line surround the root surface

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Widening of the space as a result of osteolytic process e.g, osteolytic osteoma

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Narrowing of the space as a result of osteoblastic process e.g, scleroderma

Pdl space

Widened pdl space

Narrow PDL space

Lamina dura: 

Normally appear as radiopaque clear continuous band covers the alveolar bone i.e, lining the socket and covers the crest of the alveolar bone

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Discontinuity of the lamina dura indicate pathological changes

Lamina dura pathology

Normal lamina dura

Loss of lamina dura

Alveolar bone: Bone resorption either horizontal or vertical  Bone loss: Alveolar bone height Alveolar bone health Generalized v/s localized alveolar bone loss 

Horizontal bone loss

Vertical bone loss

Metallic restoration : 

Restoration done on tooth showing radioopacity.

Status of root filling (RCT) :

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Radio-opacity on the whole pulp chamber can be seen.

Dental Implant : 

Dental implant shows obvious shape and radio-opacity on radiographs

Extraoral Periapical Radiograph (Newman And Friedman 2003) Limitations with intraoral periapical radiographic imaging: Advancing age Anatomical difficulties like large tongue, shallow palate, restricted mouth opening, Neurological difficulties, and size of radiographic sensor Chen et al in 2007 developed a sensor beam alignment aiming device for performing radiographs using this technique

aiming device with placement of the sensor

BITEWING RADIOGRAPHS Records the coronal part of upper & lower dentition along with periodontium. USES 1)To study height & contour of interdental alveolar bone. (2)To detect interproximal calculus. (3)To detect periodontal changes Horizontal bitewing radiographs  useful for proximal caries detection  limited use in periodontal treatment and treatment planning if bone loss is advanced

Vertical bitewing radiographs film is placed with its long axis at 90º to the placement for horizontal bitewing radiography, can be helpful in evaluating periodontium POSITIONING DEVICES FOR BITEWING

Hawe Paro-Bite Centering Device a positioning aid is advised to reduce the need for repeat radiographs and hence the unnecessary x-ray exposure is reduced

Occlusal Radiographs – Intraoral occlusal radiographs enable viewing of a relatively large segment of dental arch.

They are useful in patients who are unable to open mouth wide enough for periapical radiographs

LIMITATIONS OF RADIOGRAPHS Conventional radiographs are specific but lack sensitivity  More than 30% of bone mass at alveolar crest must be lost to be recognized on radiographs  Radiographs provide a 2-dimensional view of a 3-dimensional situation,  provides only information about inter proximal bone level.  Radiographs do not demonstrate soft tissue - to hard tissue relationship hence no information about depth of soft tissue pocket

STANDARDIZATION OF RADIOGRAPHS

• Constant film position – film holders, stents • Constant tube geometry - Positioning devices , Cephalostat • Using paralleling techniques • Using vertical bitewings • Using superimposed mm grid

Extraoral radiographs Extraoral radiographs are taken  when large areas of the skull or jaw must be examined or  when patients are unable to open their mouths for film placement. Useful for evaluating large areas of the skull and jaws but are not adequate for detection of subtle changes such as the early stages of dental caries or periodontal disease.

Conventional panoramic imaging/Pantamography

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OPG radiographs:

An Extra-oral technique which produces a radiograph with wide view of the maxilla and mandible. It's also known “pantomography” “Rotational panoramic radiography”

Indications for OPG radiographs: 

Gross caries

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Pain related to a whole quadrant

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Orthodontic assessment

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Pre-operative assessment

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Mandibular fractures

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Cysts, tumors , developmental anomalies

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Assessment of TMJ

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Periodontal disease

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Impacted tooth

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Implants

LIMITATIONS OF OPG  Image distortion  Lingual structures would be projected higher than buccal surfaces  Use of screen film combination results in less details than intral oral images  Production of ghost images It can be used as a alternative for intra oral full mouth series when combined with bite wing radiographs

Normal Radiographic Anatomy (OPG)

OPG Radiographic interpretation :

Describing the Lesion       

1. 2. 3. 4. 5. 6. 7.

Size Shape Location Density Borders Internal Architecture Effect on adjacent structures

Nolla stages (dentitional status) : 

Panoramic radiographs shows unerupted tooth and help to diagnose nolla stage and dentitional status.

Impacted tooth : 

Impacted tooth are identified on OPG radiographs easily as the teeth are displacement and tilted.

Fractures : 

Bone displacement, broken mandible gives the diagnosis of fracture.

Tumors/lesions: 

Ill-defined borders with sclerosis and ground glass appearance gives the diagnosis of lesion.

Cyst: 

Presence of radiolucency , corticated borders , locularity and displacement of tooth shows the diagnosis of a cyst.

Restoration material : 

Restoration can be diagnosed by radiopacity on tooth structures.

Digital radiography Digital radiography is a superior alternative for film based imaging Digital in digital radiography means numeric format of image content as well as its discreteness Images are numeric and discrete in two ways – • Spatial distribution of picture elements (pixels) and • •

In terms of different shades of gray of each of pixels Digital image

and columns

Collections of individual pixels organized in a matrix of rows

DIGITAL RADIOGRAPHY

Direct Method  Uses a Charge Couple Device (CCD) or CMOS sensor linked with fiberoptic or other wires to computer system  CCD receptor is placed intraorally as traditional films , images appear on a computer screen which can be printed or stored

Indirect Method  This method uses a phosphor luminescence plate, which is a flexible film like sensor placed intraorally & exposed to conventional x-ray tube.  A laser scanner reads the exposed plates & reveals digital image data.

Direct Digital Imaging

Direct digital sensorscomplementary

Components • X-ray source • an electronic sensor, • A digital interface card, • a computer with an analog todigital converter (ADC), • a screen monitor, software, and a printer.

charge-coupled device (CCD) or metal oxide semiconductor active

pixel sensor (CMOS-APS). array of X-ray or light sensitive pixels on a pure silicon chip.

Indirect imaging

Photostimulable phosphor radiographic systems

PSP is scanned with a helium-neon laser beam. The emitted light is captured and intensifi ed by a photomultiplier tube and then converted into digital data.

ADVANTAGES 

image can be instantly viewed by patient & dentist.

 Reduction in radiation received by patient by as much 50% to 80%  Images can be altered to achieve task specific image characteristics for eg. density & contrast can be lowered for evaluation of marginal bone and increased for evaluation of implant components.  enables the dental team to conduct remote consultations.  Computerized images can be stored, manipulated

DISADVANTAGES  Familarity with digital nature of images and understanding of principles of image manipulation is required  Lack of infection control.  Patient discomfort during placement.  As image can be easily manipulated, it can be misused in legal proceedings  Grossly overexposed or underexposed images cannot be corrected

Radiovisiography (RVG) Duret F et al (1988) Based on use of CCD Radio – X-ray generator connected to sensor Visio – storage of incoming signals during exposure and convertion to gray levels Graphy – digital mass storage unit – connected to various video printout devices latest version Trophy has released a wireless version of their RVG intraoral sensor named the RVG 6500.

Mechanism of image display Radiographic digital detector

Conventional radiographic source used to expose sensor

Detector converts X-rays to visible image

Image display on monitor

Specialized techniques

Introduction of digital radiography meaningful in dentistry utility

applications with

 Early detection  Quantitative assessment  3 D imaging

diagnostic

Digital subtraction radiography Zeidses des Plantes (1935) : 1st demonstrated use of subtraction imaging  Depends up on conversion of serial radiographs into digital images.  The serially obtained digital images are superimposed & image intensities of corresponding pixels are subtracted If change has occurred The brighter area represents gain

This technique facilitates both qualitative & quantitative visualization of even minor density changes in bone by removing the unchanged anatomic structures from image

Base line gain

after one year

bone

COMPUTER ASISTED DENSITROMETRIC IMAGE ANALYSIS SYSTEM Introduced by Urs Brägger et al 1988  A video camera mesaures the light transmitted through the a radiograph  Signal are converted to grey scale images  Camera is interfaced with computer and image processor for storage and mathematic manipulation of image  Offers an objective method for studying alveolar bone changes quantitatively  High degree of sensitivity ,accuracy and reproducablity

Urs Brägger et al in 1988  CADIA was more sensitive than subtraction radiography  CADIA was capable of assessing differences in remodeling activity over 4–6 weeks after periodontal surgery  Objective method to quantify alveolar bone density Deas et al 1991 on monitoring the relationship of CALs and CADIA, found that prevelance of progressive lesions as detected by radiograph is higher than previous accepted data CADIA is still used in research purposes for detecting quantitatively the alveolar bone density

Radiographic Changes in Periodontitis

1. Fuzziness and a break in the continuity of the lamina dura at the mesial or distal aspect of the crest of the interdental septum have been considered as the earliest radiographic changes in periodontitis.

The presence of an intact crestal lamina dura may be an indicator of periodontal health, whereas its absence lacks diagnostic relevance.

2. A wedge-shaped radiolucent area is formed at the mesial or distal aspect of the crest of the septal bone . The apex of the area is pointed in the direction of the root. This is produced by resorption of the bone of the lateral aspect of the interdental septum, with an associated widening of the periodontal space.

3. Fingerlike radiolucent projections extend from the crest into the Septum. The radiolucent projections into the interdental septum are the result of the deeper extension of the inflammation into the bone.

4. The height of the interdental septum is progressively reduced by the extension of inflammation and the resorption of bone.

Radiographic Appearance of Interdental Craters •Interdental craters are seen as irregular areas of reduced radiopacity on the alveolar bone crests. •They are generally not sharply demarcated from the rest of the bone, with which they blend gradually. •Radiographs do not accurately depict the morphology or depth of interdental craters, which sometimes appear as vertical defects. •The real morphology and topography of interdental craters can only be seen by surgical exposure.

Radiographic Appearance of Furcation Involvements Definitive diagnosis of furcation involvement is made by clinical examination, which includes careful probing with a specially designed probe (Nabers probe). Radiographs are helpful but show artifacts that make it possible for furcation involvement to be present without detectable radiographic changes. As a general rule, bone loss is always greater than it appears in the radiograph.

To assist in the radiographic detection of furcation involvement the following diagnostic criteria are suggested: 1. The slightest radiographic change in the furcation area should be investigated clinically, especially if there is bone loss on adjacent roots. 2. Diminished radiodensity in the furcation area in which outlines of bony trabeculae are visible suggests furcation involvement. 3. Whenever there is marked bone loss in relation to a single molar root, it may be assumed that the furcation is also involved.

Radiographic Appearance of the Periodontal Abscess

The typical radiographic appearance of the periodontal abscess is that of a discrete area of radiolucency along the lateral aspect of the root. However, the radiographic picture is often not typical because of many variables such as the following: 1. The stage of the lesion. In the early stages the acute periodontal abscess is extremely painful but presents no radiographic changes. 2. The extent of bone destruction and the morphologic changes of the bone. 3. The location of the abscess. Lesions in the soft tissue wall of a periodontal pocket can not be seen in radiographs. Similar to abscesses on the facial or lingual surface. Therefore the radiograph alone cannot be relied on for the diagnosis of a periodontal abscess.

Radiographs and clinical probing Regenerative and resective flap designs and incisions require prior knowledge of the underlying osseous topography. Careful probing of these pocket areas after scaling and root planing often require local anesthesia and definitive radiographic evaluation of the osseous lesions. Radiographs taken with periodontal probes or other indicators (e.g., Hirschfeld pointers) placed into the anesthetized pocket show the true extent of the bone lesion.

Radiographic Changes in Localized Aggressive Periodontitis

Localized aggressive periodontitis is characterized by a combination of the following radiographic features: 1. Bone loss may occur initially in the maxillary and mandibular incisor and/or first molar areas, usually bilaterally, and results in vertical, arclike destructive Patterns. 2. Loss of alveolar bone may become generalized as the disease progresses but remains less pronounced in the premolar areas.

Radiographic Changes in Trauma from Occlusion

Trauma from occlusion can produce: • Radiographically detectable changes in the lamina dura, morphology of the alveolar crest, width of the periodontal space, and density of the surrounding cancellous bone. •Traumatic lesions manifest themselves more clearly in faciolingual aspects, because mesiodistally, the tooth has the added stability provided by the contact areas with adjacent teeth. • Therefore slight variations in the proximal surfaces may indicate greater changes in the facial and lingual aspects.

The injury phase of trauma from occlusion: produces a loss of the lamina dura that may be noted in apices, furcations, and/or marginal areas. This loss of lamina dura results in widening of the periodontal ligament space. This change, particularly when incipient or may be confused with technical variations due to x-ray angulation or malposition of the tooth it can be diagnosed with certainty only in radiographs of the highest quality. The repair phase of trauma from occlusion Radiographically, this is manifested by a widening of the periodontal ligament space, which may be generalized or localized. Variations in width between the marginal area and midroot or between the midroot and apex are detected, it means that the tooth is being subjected to increased forces.

More advanced traumatic lesions : May result in deep angular bone loss, which, when combined with marginal inflammation, may lead to intrabony pocket formation. In terminal stages these lesions extend around the root apex, producing a wide radiolucent periapical image (cavernous lesions).

Root resorption may also occur as a result of excessive forces on the periodontium, particularly those caused by orthodontic appliances. Although trauma from occlusion produces many root resorption areas, they are usually of small and difficult to be detected radiographically.

Additional Radiographic Criteria in the Diagnosis of Periodontal Disease

Radiopaque horizontal line across the roots. This line demarcates the portion of the root where the labial and/or lingual bony plate has been partially or completely destroyed from the remaining bone-supported portion

Vessel canals in the alveolar bone. linear and circular radiolucent areas produced by interdental canals and their foramina. These canals indicate the course of the vascular supply of the bone and are normal radiographic findings. This is often so prominent, particularly in the anterior region of the mandible, that they might be confused with radiolucency resulting from periodontal disease.

Differentiation between treated and untreated periodontal disease. •It is sometimes necessary to determine whether the reduced bone level is the result of periodontal disease. or if destructive periodontal disease is present. •Clinical examination is the basic determinant. However, radiographically detectable alterations in the normal peripheral outline of the septa are corroborating evidence of destructive periodontal disease.

bibliography  

Text book of radiology-white and pharow Text book of periodontology-carranza

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