DENTAL XRAY IMAGE CHARACTERISTICS DEPARTMENT OF ORAL MEDICINE

DENTAL X-RAY IMAGE CHARACTERISTICS DEPARTMENT OF ORAL MEDICINE & RADIOLOGY Dentistry Explorer

Dental X-ray image characteristic include both visual & geomatric characteristics. Visual characteristic: • Density. • Contrast. Geometric characteristics: • Sharpness. • Magnification. • Distortion. Dentistry Explorer

RADIOLUCENT Dark Gray to Black A structure that lack density appear radiolucent e. g. soft tissue & spaces Dentistry Explorer

RADIOPAQUE White to Light Gray Radiobaque structures are dense & absorb X-ray, e. g. enamel, dentine, & bone. Dentistry Explorer

I) Density Represents the degree of darkening of an exposed x-ray film (white to black) Dentistry Explorer

The overall density of the film affects the diagnostic value of the film (ideal density, too light, too dark) Dentistry Explorer

Density influenced by: 1. Exposure factors: • m. A • k. V • Exposure time 2. Object thickness 3. Object density 4. Film fog Dentistry Explorer

Exposure factors (m. A, k. Vp, exposure time). An unnecessary increase in any of these factors results in an increase in film density. Object thickness: the larger the patient’s head, the more x-rays that are needed to produce an ideal film density Object density: determined by type of material (metal, tooth structure, composite, etc. ) and by amount of material Dentistry Explorer

Film Fog Increased film density from causes other than exposure to the primary x-ray beam (scatter, improper safelighting, improper film storage, expired film) fog Dentistry Explorer

II) Contrast The difference in densities (blackness) between various regions on a radiograph Dentistry Explorer

High Contrast Short Scale Black and White (Few shades of gray) Best for caries detection Dentistry Explorer

Low Contrast Long Scale Many shades of gray Best for periapical or periodontal evaluation Dentistry Explorer

Contrast influenced by: 1. Subject contrast 2. k. Vp 3. Film contrast Dentistry Explorer

Subject contrast Results from varying object densities within patient, this is determined by: thickness, density & composition of the subject Dentistry Explorer

k. Vp Affects energy (penetrating ability) of x-rays. 40 Dentistry Explorer 50 60 70 80 90 100

Film contrast: It refers to the characteristics of the film that influence the radiographic contrast, it is incorporated into film by manufacturer. Dentistry Explorer

Film Fog Film fog makes the whole film darker, making it harder to see the density differences (contrast) fog Dentistry Explorer

I) Sharpness Measures how well the details (boundaries/edges) of an object are reproduced on a radiograph. The fuzzy unclear area that surround the image is termed penumbra. Dentistry Explorer

Penumbra (pene=almost + umbra= shadow) Def. : Zone of unsharpness along the edge of images in a radiograph The larger the penumbra, the less sharp the image will be Dentistry Explorer

Target (focal spot) Penumbra Umbra (complete shadow) Dentistry Explorer

Sharpness influenced by: 1. Focal spot size 2. 3. 4. 5. 6. Source–object (teeth) distance Object (teeth)-film distance Intensifying screens Film crystal size Motion Dentistry Explorer

Decrease focal spot size, increase sharpness Target Object Umbra Dentistry Explorer Penumbra

Increase source-object distance, increase sharpness Target Teeth Umbra Penumbra film Dentistry Explorer

Decrease object-film distance, increase sharpness Target Teeth Umbra Penumbra film Dentistry Explorer

Intensifying screens decrease sharpness Dentistry Explorer

Film crystal size The faster film contain larger crystal size that produce less image sharpness, and vice versa. Unsharpness occur because the large crystals don’t produce object outline as well as smaller. Dentistry Explorer

Patient motion decreases sharpness Dentistry Explorer

II)Magnification Increase in size Magnification affected by: Source-object distance Object-film distance Dentistry Explorer

Magnification Increase source-object distance, decrease magnification Target 16” Target 8” Decrease object-film distance, decrease magnification Target 16” Dentistry Explorer

III) Distortion Change in the true shape or size of the object Distortion affected by: 1. Film-teeth relationship 2. Beam alignment Dentistry Explorer

Paralleling Dentistry Explorer

Bisecting angle Dentistry Explorer

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Ideal Radiograph 1. Image same size as object 2. Image same shape as object 3. Image has good detail 4. Image has good density and contrast Dentistry Explorer

Mandibular molar periapical film comes closest to satisfying properties of an ideal radiograph (either paralleling or bisecting) Dentistry Explorer

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. Dentistry Explorer

Interpretation Vs. Diagnosis: Interpretation refers to an explanation of what is viewed on a radiograph while diagnosis refers to the identification of disease by examination or analysis. In other words the interpretation is a step in the diagnosis. Dentistry Explorer

Rules of radiographic interpretation 1. The area to be examined must be completely shown at optimal angulations 2. All the boundaries of the area of interest must be shown with normal structures around it. 3. Knowing and familiarity with all normal anatomical landmarks as well as all various pathological conditions that may affect the area of interest. 4. Optimum viewing condition. Dentistry Explorer

Viewing condition: Ideally, should include the following: ü Ambient light in the room should be reduced. ü Intraoral radiographs should be mounted. ü Light from the view-box should be of equal intensity across the viewing surface. ü The size of the view-box should accommodate the size of the film. ü A magnifying lens allows detailed examination of small regions of the film. Dentistry Explorer

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Image Analysis: The first step in image analysis is to use a systemic approach to identify all the normal anatomy present in an image. Avoid limiting your attention to one particular region of the film. Dentistry Explorer

Steps of interpretation • • • Localization. Observation. General consideration. Interpretation. Correlation. Dentistry Explorer

Localization I. III. IV. Localized or generalized Position in the jaw Single or multiple Size Dentistry Explorer

How to identify the position of the periapical film? Embossed dot identify right from left and the anatomical land mark to identify the jaw and the area. Dentistry Explorer

Upper left Lower left Dentistry Explorer

Upper right premolar Lower anterior Dentistry Explorer

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Observation • All shadows, other than the localized shadows of the normal landmarks must be observed. • 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 ………… Dentistry Explorer

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

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) Dentistry Explorer

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 Dentistry Explorer

Correlation Ø The final step is to correlate all of the radiographic features to reach a radiographic differential diagnosis. Ø 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. Dentistry Explorer

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