Diagnostic Imaging Flashcards
The majority of dental pathologies effecting companion
animals have?
radiographically detectable signs
Periodontitis, the most common oral disease, is typified by?
Progressive apical migration of
the gingival attachment and associated bone loss, detectable by radiography
The findings of two studies reveal that clinically significant disease, of apparently healthy teeth, is identified in approximately how many dogs and cats?
30% of dog and 40% of cat dental radiographs.
Performing
dental radiography of diseased teeth was found to demonstrate clinically useful information in over how many cases?
Three quarters of cases.
Perfection is not mandatory when performing dental radiographs. The operator should
strive for?
Clinically diagnostic images and not become so focused on identification of the “angles” involved that it inhibits the flow of the procedure.
There are 2 basic components to a dental radiographic system, what are they?
X-ray generation
and
Image capture
Dental X-ray generators are comparatively low power units and as such are considered very safe. The majority have?
Fixed kV, commonly 60-70kV, and mA with the ability to alter the
time of exposure.
Dental X-ray generators produce comparatively few X-rays and previously could be used in
non-specific treatment areas. A recent change in radiation protection regulations requires that?
Controlled areas extend at least 2 meters from the primary beam, usually considered to be the edge of
the table unless interrupted by a suitably attenuating barrier, such as a brick wall. All entrances to
the controlled area must have automatic warning lights. In order to minimise scatter it is advisable to use a lead-vinyl sheet placed under the head.
Image capture is performed via standard X-ray sensitive film, what two kinds?
Phosphorescent plates used in indirect digital systems or by a digital sensor for direct digital radiography.
Dental film sizes, including digital screens, have standardised dimensions, What are these?
0 to 4
with 0 the smallest
Dental film is
available in different speeds, what are they?
E and F being the fastest and as such they can reduce the radiation exposure to operator and patient.
Direct digital sensors are only available in what size?
2 and smaller due
to the cost of manufacture of larger sizes being too great
Direct digital (DR) and indirect digital (CR) systems have much in common. Image
acquisition is rapid, how fast for DR and CR?
3-5 seconds for DR and approximately 10 seconds for size 2 CR screens. The
larger the screen size the longer the acquisition time via CR
DR sensor size limitations can be compensated for by?
Taking multiple views of the same tooth, roots and crown separately.
There are 3 main dental radiographic positioning techniques:
Intra-oral parallel technique, (IOP) Bisecting Angle (BA) and Extra-Oral
To evaluate the periodontal tissues fully, it is advisable to include a minimum of how much of the radicular tissue?
three millimetres of the radicular tissues surrounding the tooth’s root.
The close association and specific orientation of the teeth mean that orthogonal views are
only possible for which teeth?
Canine teeth
The intra-oral parallel technique can be utilised to acquire what views?
Lateral view of the mandibular molar
teeth and 4th premolar teeth and the third premolar tooth in some individuals.
The mandibular incisor and canine teeth
as a rostra-caudal view. The curvature of the roots of these teeth result in a near parallel view without affecting the diagnostic value of the radiograph, although the crowns of the teeth will be fore shortened.
What is the bisecting angle (BA) technique used for?
The BA technique is used for imaging all of the maxillary teeth, the lateral view of the mandibular canine teeth and the lateral view of the rostral mandibular premolars.
The use of the extra-oral technique reduces what?
The impact of the zygomatic superimposition on the roots.
How is an extra-oral x-ray taken?
With the patient in lateral recumbency and the palate perpendicular to the table the screen
is placed, extra-orally, under the cheek of the dependent arcade. The cusps of the maxillary teeth
are level with the most ventral border of the screen. The mouth is briefly propped open, (it is important to limit the time of near maximal mouth opening in cats as this can result in circulatory compromise to the brain) (Barton-Lamb, Martin-Flores, Scrivani, Bezuidenhout, Loew, Erb, Ludders) (Martin-Flores, Scrivani, Loew,
Gleed, Ludders). The X-ray beam is angled from the dorsal aspect across the palette at approximately
20 degrees to the axis of the vertical. This results in a near dimensionally accurate image of the
dependant maxillary premolar teeth and molar tooth, although some elongation wile evident. It is
important that the beam is angled sufficiently to prevent the superimposition of the crowns of the
contralateral premolar teeth over the root apices of the target teeth.
Conventional radiography utilises an orthogonal view to examine the relative position of overlying structures but
this is not possible in dental radiography due to anatomical constraints. Dental radiography utilises
tube shift to mitigate this constraint. Tube shift describes?
A rostral or caudal movement of the X-ray
generator from a truly lateral or rostro-caudal direction.
Overlying structures are separated by this
movement
What is the SLOB rule?
The SLOB rule notes that the lingual structure will move in the same direction as the tube shift and the buccal structure will move in the opposite direction to the tube shift
(S.ame L.ingual O.pposite B.uccal).
When is the SLOB rule most helpful?
This is of benefit when evaluating individual overlying roots of three rooted teeth, such as the maxillary 4th premolar.
Similarly, pathology or artefact of anatomy can be distinguished, the middle mental foramen can appear as a
lucency of the mesial root of the 2nd mandibular premolar but these structures can be separated
with tube shift and this would not be possible in the presence of true pathology.
What is the first step in the evaluation paradigm?
The initial step in the evaluation paradigm is to assess whether the radiograph is truly diagnostic.
The primary evaluation process is similar to that performed for conventional radiographs.
How can a radiograph be assessed if it is diagnostic?
- Is the structure of interest centred in the field of view?
- In the case of a tooth or teeth, is sufficient peri-radicular tissue (at least 3mm around the
apex of the tooth root) evident? - Is the radiograph of appropriate exposure and is there sufficient contrast?
- Is there significant distortion of the target structures?
- What are the normal structures in the field of view and by elimination what are pathological? (Take care to appreciate marginal structures as peripheral pathology can be easily
missed.) - Are additional images required to fully evaluate the structure.
- Would comparison of the contralateral tissues provide benefit for comparison?
- Are follow up radiographs indicated and if so when?
When viewing a dental x-ray the convention for image orientation is referred to as?
lingual
mounting.
How do images appear when lingually mounted?
Radiographs should be orientated as if the observer were looking into an open mouth,
facing them with the crowns of all teeth pointing toward the tongue, hence the maxillary teeth are
orientated with the cusps pointed downwards and the mandibular cusps pointed up. Lingual
mounting will allow identification of left and right arcades.
Enamel can vary in thickness from?
0.1mm to 1mm (Crossley 1995).
The cervical region of the tooth (the narrowing between the crown and the root)
does not have enamel or bone overlying it and can therefore appear to be more radiolucent than
the crown or root. This lucency, referred to as the …………… should not be mistaken for pathology.
cervical burnout
The alveolus is separated radiographically from the root by a thin, radio-lucent line which
represents the?
periodontal ligament space (PLS).
The PLS should conform closely to the outline of
the root closely. Widening (the PLS being more than twice the width of comparator teeth/ regions
of the root), irregularity or loss of the PLS may represent?
the presence of pathology
A thin, radioopaque line may surround the periodontal ligament, the lamina dura. The lamina dura is?
The dense bone of the lining of the alveolus
Although the roots of the teeth are covered in cement, this layer is not radiographically
evident unless it is?
Grossly thickened as seen in cases of hypercementosis.
Loss of the PLS may
indicate ……. of the tooth and loss of the lamina dura may indicate apical ………
Ankylosis
Periodontitis
What are chevron lucencies?
The maxillary incisor and canine teeth, and in some instances the mandibular incisors, may
have apparent widening of the PLS at their apical limit. This widening does not have an irregular
outline and continually tapers following the axis of the PLS. These are referred to as chevron lucencies. These lucencies must be differentiated from pathology. They appear due to a contrast in
radio-density between the more dense alveolar and incisive bone and the less dense trabecular
bone around the apex of the roots (DuPont & DeBowes 2008).
Dramatic discrepancy of the alveolar margin’s
height along the arcade is likely to represent?
periodontal disease
Why can the pulp and dentine can be considered as a single anatomical complex?
As projections from
odontoblasts that line the pulp cavity penetrate into the dentine via dentinal tubules.
Focal enamel defects or pits most commonly on the occlusal surfaces of the molar teeth of
dogs and may represent the development of?
dental caries
How many radiographs in a canine full mouth series?
14
How many radiographs in a feline full mouth series?
10
What is the alveolar ridge?
Show some non-dental anatomy of the maxilla?
Show the palatine fissures?
Show are tooth with an accessory root?
Show a tooth with gemination?
Show intra-radicular grooves?
Show apical periodontitis?
Show a perio-endo lesion?
Show tooth impaction?
Show luxation?
Show oral neoplasia?
