Dental Radiograph appears as a
BLACK & WHITE image that includes shades of GREY
Radiolucent
- Portion of the radiograph that is DARK. BLACK
- LACKS Density
- PERMITS the Passage of the X-ray beam w/ little or No resistance
Ex. Air Space
Radiopaque
- Portion of the Radiograph that is WHITE/ LIGHT
- Structures are DENSE
- Absorb or RESIST the passage of the X-ray beam
Ex. Enamel, Dentin, Bone, Metal Restorations
Diagnostic Radiograph
- Provides a great deal of INFO
- The images exhibit proper DENSITY & CONTRAST
- SHARP Outlines
- SAME shape & size as the object radiographed
2 Visual Characteristics of Radio graphic image are
- Density & Contrast
-which directly influence the Diagnostic quality of a dental radiograph
Density
- Overall BLACKNESS/ DARKNESS of a dental Radiograph
- Darker areas in radiograph represent Heavier deposits of Black silver particles
- Degree of Silver Blackening
Exposure Factors
- Control the Density of a dental radiograph
- Milliamperage (mA)
- Operating Kilovoltage Peak (kVp)
- Exposure Time
Contrast
The DIFFERENCE in the DEGREES of BLACKNESS (densities) between adjacent areas on a dental radiograph
High Contrast
The radiograph that has very DARK areas & very LIGHTareas
Low Contrast
- The radiograph that does NOT have very dark or light areas
- Many shades of GREY
The prefered Dental radiograph image is
a radiograph between lOW contrast & HIGH contrast
Film Contrast
- Inherent qualities of FILM & film PROCESSING
- qualities of the SENSOR
Subject Contrast
- Characteristics of the SUBJECT that influence radiographic contrast
- Determined by the Thickness, Density, Composition
Increasing the Kilovoltage affects Contrast by
-INCREASING the average ENERGY of the X-rays & by producing Higher energy X-rays
- Higher KV produces an image w/ DECREASED or LOW contrast w/ many shades of GREY (very dark)
Scale of Contrast
The RANGE of useful DENSITIES seen on a dental radiograph
Short- Scale Contrast
- Radiograph that shows areas of BLACK & WHITE
- Has LOW Kilovoltage
Long- Scale Contrast
- Radiograph that exhibits many shades of GREY
- Has HIGH Kilovoltage
Stepwedge
- Can be used to demonstrate SHORT & LONG scale Contrast
- Constructed of ALUMINUM
3 Geometric Characteristics of Radiographic image are
- Sharpness
- Magnification
- Distortion
Influence the DIAGNOSTIC QUALITY of a radiograph
Sharpness
(Detail, Resolution, Definition)
- The capability of the Receptor to reproduce the DISTINCT OUTLINES of an object
Pneumbra
The LACK of image sharpness, BLURRING of edges
Sharpness of an image influenced by
- Focal spot size
- FIlm Composition
- Movement
Focal Spot Size
- Is the small area of the Tungesten Target of the ANODE
- The SMALLER he focal spot area the SHARPER the image appears
Film Composition
The COMPOSITION of the Film EMULSION influences the SHARPNESS
The emulsion of Faster film contains
LARGER crystals that produce LESS sharpness
Movement
Influences Image SHARPNESS
Image Magnification
image that appears LARGER than the actual size of the object it represents
Image magnification factors of a radiograph are
- Target- receptor distance
- Object- receptor distance
Target Receptor distance
The distance b/w the SOURCE of X-rays & image receptor
A longer PID & Target receptor distance result in
LESS image Magnification
A SHorter PID & target receptor distance result in
MORE image magnification
Object Receptor Distance
- Distance b/w the OBJECT being radiographed & the image receptor
- Tooth & receptor should always be placed as CLOSE together as possible
The Closer the Tooth is to the Receptor
The LESS the Enlargement of the Image
Dimensional Distortion of image
-Is a VARIATION in the true SIZE & SHAPE of the object being radiographed
- Results from IMPROPER RECEPTOR ALIGNMENT of beam angulation
Influencing factors of Dimensional Distortion
- Object receptor alignment
- X-ray beam angulation
Object Film alignment
- The object & receptor must be PARALLEL to eachother
- if the object (tooth) & receptor are not parallel an angular relationship results
X-ray beam Angulation
X-ray beam must be directed PERPENDICULAR to the tooth & receptor
Visual Characterisitcs
- Increase Ma = Increase Density
- Increase KVp = Increase Density
- Increase Time = Increase Density