Quality Assurance in the Dental Office, Occlusal Localization
when should dental x-ray machines be tested?
annually to test for malfunctions, inadequate collimation, tube head drift, timing errors, inaccurate kV or mA readings
anterior mandibular topographical occlusal projection
anterior: width-wise in front of mouth standard: length-wise to back of mouth lateral: length-wise off centered to one side
if you get a distorted image you should:
assess receptor bending during imaging and check scanner
spatial resolution
capacity for distinguishing fine detail in an image.
if you get a grainy image you should:
check exposure factors and protect PSPs from light
if you get no image you should:
check machine for on status and scanning technique
how to check the strength of the developer solution
compare film densities to a standard using tests such as reference radiograph, stepwedge radiograph, or normalizing device
vertical angulation for lateral
for maxillary teeth = +60 for mandibular teeth = -90 through floor of mouth
vertical angulation of topographical
for maxillary teeth = +65 through nose for mandibular teeth = -55 through chin
vertical angulation for cross sectional
for maxillary teeth = +90 for mandibular teeth = -90
how to check for tube head stability
free of drift and oscillation after 2 seconds
a written monitoring schedule should include:
-all quality control tests and frequency of testing -supplies -film processing -digital imaging
quality administration procedure examples
-description of plan -assignment of duties -monitoring/maintenance schedule -record keeping -evaluation/revision plans -in service training
milliamperes
-flow of electrons from cathode to anode -controls # of electrons produced -increased mA = increased photons = increased density
kilovoltage
-force of electrons accelerating from cathode to anode -increase kV = increased penetrating power of photons
localization techniques help to identify:
-foreign object -fractures -supernumerary impacted tooth in the mouth -eruption patterns -Salivary stones
SLOB rule
-must be a change in the horizontal or vertical angulation -objects on the lingual surface will move in SAME direction as tubehead -objects on the buccal surface will move in the OPPOSITE direction as the tubehead
spatial resolution is determined and affected by:
-pixel size (smaller = increase spatial) -receptor type -focal spot size (smaller = increased sharpness/resolution) -projection geometry of beam -motion blur
a record keeping log should include:
-test performed, date, and test results -processing solutions with dates of replacement, replenishment, and processor or tank cleaning
quality control tests examples
-x-ray machines -film -screens, cassettes for dirt or scratches -darkroom -processing equipment and solutions -digital imaging equipment
annual quality control tests for dental machine covers:
-x-ray output -Kv -timer -HVL -mA -collimation -beam alignment -tubehead stability
two types of localization
1. buccal object rule/clarks rule: 2 images exposed at different angulations 2. right angle: expose normal PA and occlusal image; examine 2 images projected at right angles to each other
primary components of quality assurance
1. equipment (operatory) 2. processing (scanning/darkroom) 3. operator skills (technique)
Occlusal projections identifies:
1. foreign objects 2. eruption pattern 3. retained roots of extracted teeth 4. located pathology in the palate or floor of mouth (salivary cysts, malignancies) 5. trismus 6. pediatric intraoral imaging
optimal temperature for processing solutions
1. manual processing: 68 F 2. automatic processing: 82 F
if a density difference from a coin test is visible, it may be due to:
1. wattage of safelight bulb is too high 2. safelight is too close to counter 3. safelight filter may be faded, damaged, incorrect 4. too many safelights 5. leakage of light *if one of these reasons, you should repeat the test with safelights OFF
localization
2D representation of a 3D area. can locate the object using right angle technique or SLOB
Reference radiograph
A radiograph that is processed under ideal conditions and then used to compare the film densities of radiographs that are processed daily
ALARA
As Low As Reasonably Achievable
Stepwedge Radiographs
Device constructed of layered aluminum steps, placed on film and exposed to x-rays, different densities are seen
slow clearing
If the film does not completely clear in 3 to 4 minutes, the fixer solution is depleted.
Fresh film test
Quality control test that shows a clear film with a slight blue tint, showing that the film is fresh and has been properly stored.
SLOB stands for:
Same Lingual Opposite Buccal
normalizing device
Used to monitor developer strength and film density
unmatched density on stepwedge radiograph
if density on the daily radiograph differs from that on the standard radiograph by more than two steps in the stepwedge the solution is depleted
reference radiograph that shows matched densities
if the densities on the reference radiograph match the densities on the daily radiographs, the developer solution is okay
periodic in service training should include:
training on upgrading and improving x-ray exposure techniques, film processing procedures, and digital imaging
matched density on stepwedge radiograph
use middle density seen on standard stepwedge radiograph for comparison. if density seen matches the density on the daily radiograph, the solution is okay
functioning processor
The unexposed film appears clear and dry and the exposed film appears black and dry
processing solutions must be replenished ___ and changed ___
daily; 3-4 weeks
reference radiograph that shows unmatched densities
darker: the solution is too concentrated or warm lighter: solution is weak or cold
if you get an image with white lines, scratches, or unusual patterns you should:
discard receptor and re-image
if you get a ghost or double image you should:
erase plate completely
darkroom lighting should be checked...
every 6 months; only after the light tightness of the darkroom has been established can the safelighting be checked
____ is one of the most critical areas in quality control and requires daily monitoring
film processing
higher penetrating x-rays produce:
lower contrast
Goal of quality assurance
maintain all systems at a consistently functioning optimal level and prevent detrimental effects on patient services.
anterior occlusal projections of primary teeth
maxillary = +60 with size 2 receptor mandibular = -55 with size 2 receptor
The most critical component in film processing quality control is:
monitoring of processing solutions
when should screens be cleaned?
monthly to check for worn closures, light leaks, warping; after cleaning apply an antistatic solution
checking of processing equipment
needs to be checked daily; check the timer, thermometer, temperature of water bath, developer and fixer solutions.
Fogged film
quality control test that shows an expired film, or a film that has been improperly stored or exposed to radiation. do not use
Fixer strength
removes the unexposed silver halide crystals on the film that results in clear areas on the processed dental image; when the fixer is at full strength a film should clean within 2 mins
developer solution that is weakend or concentrated must be:
replaced
safe lighting test that shows improper safelighting & how to avoid it
shows a fogged background; avoid it by unwrapping film 4 feet away from the safelight
Screen-film contact test showing an adequate contact
shows a wire mesh image on a film with uniform density
safe lighting test that shows proper safelighting
shows no visible image on the processed film
posterior bitewing and PA projections of primary teeth use what size receptor?
size 0
what size receptor does maxillary and mandibular occlusal projections use?
size 4 with active phosphor side facing toward beam
quality assurance
special procedures that are used to ensure the production of high-quality diagnostic images. includes quality control tests and quality administration procedures. dentist is responsible for this.
quality control tests
specific tests used to maintain and monitor dental x-ray units, supplies, film processing, and digital imaging equipment
developer solution that is too cold or warm must be:
temperate must be adjusted
what should be checked in automatic processing equipment?
water circulation system must be checked, and the solution level, the replenishment system and temperature.
the surface of a viewbox should be cleaned ___
weekly