Radio unit 2 pt1

robbypowell's version from 2015-04-24 11:14


Question Answer
What is the most common detector type in panoramic radiographs?CCD (charge-coupled device)
Where do posterior midline structures appear on the image?at the far right and left of pan (duplicated)
What is the vertical angle of the x-ray beam?negative vertical angle, -7 deg,( in order to avoid occipital bone)
Describe the shape of the x-ray beam.beam is NARROW
Where are the two focal spots of the panoramic radiograph?EFFECTIVE (horizontal plane, center of rotation, point rotated around) TRUE focal spot (vertical plane, in x-ray tube anode)
Which plane of the panoramic image is subject to increased magnification? What technique compensates for this?HORIZONTAL plane is magnified (b/c closer to detector) however ROTATION corrects
What is the central plane of the image layer?layer where horizontal plane magnification is corrected for, so image is clear in this plane
What happens to objects facial and lingual to central plane of image layer?become BLURRY & DISTORTED
What happens to it when the rotation of the detector’s speed changes?SLOWER makes it closer to center of rotation (anteriors), FASTER makes it further from center of rotation (posteriors)
What is the shape of the non-stationary center of rotation’s path?upside down V shape, contemporary pan technique
What are the two causes of distortion on a panoramic x-ray?2 focal spots (and variable speeds to accommodate) negative vertical angulation (can make objects appear more superior than they are)(e.g. inferior alveolar nerve)
What are the three reference lines for guiding patient positioning?1. Mid sagittal plane, 2. Horizontal plane, 3. Image layer- usually in the canine area
What does the image look like if the patient is too far forward?pan is compressed inward, cervical spine takes up good portion of sides and teeth are narrow and thin
What does the image look like if the patient is Too far back?pan is stretched outward, condyles are not visible on radiograph
What does the image look like if the patient is Rotated?one side is thinned and one widened. widened side has horizontal overlap on teeth
What is the difference in the appearance of the occlusal plane when the patients chin is too low?teeth angled, big grin. APICES OF MAN INCISORS CUT OFF
What is the difference in the appearance of the occlusal plane when the patients chin is too high?teeth too flat. APICES OF MAC TEETH CUT OFF
What becomes hard to see if the patient’s tongue is not against the hard palate?Maxillary root apices
What is superimposed over the teeth when the patient slumps?spine superimposed when patient slumps. esp over mandibular teeth
What is the spatial resolution of film/PSP panoramic radiographs?3-4 line pairs / mm
What is the spatial resolution of Direct Digital panoramic radiographs?6-8 line pairs / mm

special techniques

Question Answer
What size imaging plate/film is used in occlusal radiography?LARGE (on the scale of 0-4 it is a solid 4)
What plane is visualized by occlusal radiography?the BUCCO-LINGUAL plane (or the horizontal plane) of an arch
What special technique is useful for patients unable to open widely and can determine the extent of pathologies like mandibular tumors?Occlusal radiograph technique
What are the four types of occlusal radiographs?1. Anterior 2. Cross-sectional 3. Mandibular 4. Maxillary
What is the position of a patient’s midsagittal plane during anterior maxillary and cross-sectional maxillary occlusal radiographs?parallel to floor
What is the difference between anterior maxillary and cross sectional occlusal radiographs in the vertical angulation of the x-ray beam? 45 deg for Anterior, 65 deg for Cross-sectional
What is the difference between anterior maxillary and cross sectional occlusal radiographs in the location the central beam passes through?Tip of the nose for anterior, Bridge of the nose for Cross-sectional
What has greater superimposition of other structures: cross sectional mandibular or maxillary occlusal radiographs?Maxillary goes through more things
Where is the occlusal plane positioned relative to the floor for cross-sectional mandibular and mandibular symphysis occlusal radiographs?perpendicular to floor for cross-sectional, 45 deg from floor angle for Symphisis
What are the five Extra-oral radiograph techniques? Which is not commonly used?Lateral Jaw (not common... intra-oral x-ray tube), Panoramic, Cephalometric (lateral view), PosterioAnterior Projection (PA), Water's view
Which extraoral imaging technique uses an intraoral x-ray tube and an extra-oral receptor?Lateral Jaw
What structures are used to assess the Canthomeatal plane?External Auditory Meatus & Angle of the eye (lateral)
What structures are used to assess the Frankfort horizontal plane?Lower eyelid --> tragus of the ear
Which extraoral technique requires the Frankfort horizontal plane to be parallel to the floor?Cephalometric view (lateral view)
Which of the extraoral techniques has low clarity anatomic landmarks due to the superimposition of much of the skull? Where is the x-ray cone and receptor located for this technique?PA; X-ray tube behind head, receptor in front
What is Water’s view useful for viewing? Where does the central beam pass through for this technique?useful for sinuses, central beam passes through center of head
Using the tube shift method, after shifting the tube toward the midline, the object appears to shift distally. Is the object buccal or lingual to the teeth?Buccal
What is the SLOB rule?Same Lingual Opposite Buccal
When are endodontic radiographs taken? How are they taken in each phase?before (Paralleling), during (modified paralleling), and after (paralleling) treatment
What is ALARA?As Low As Reasonably Achievable
How many images are associated with a full mouth series in children? Adults?12 for children, 20 for adults

normal mandible

Question Answer
What is the baseline of our radiographic analysis?normal anatomy
Why don’t radiographs reveal disease?because disease is a continuous process... and radiographs a fixed point (example... horizontal bone loss could have already been treated, but still present)
When is the best time to interpret radiographs?in the morning, when you're awake and alert
What type of bone makes up the L and B plates of the alveolar bone?Cortical bone
What are medullary spaces? What regions of the alveolar bone are they found in?the marrow-filled spaces of cancellous bone
What is Wolf’s law? What does it predict will happen to the alveolar bone of an extracted tooth site?states bone is related to function; extracted tooth site will have bone loss
Where is the interalveolar septum located?between teeth
What are the three trajectories of the trabeculae of the maxilla?Canine, Pterygoid, Zygomatic
What is the one trabecular trajectory in the mandible?Teeth Apices --> ramus of condyle
What is the difference in trabeculae arrangement and marrow space size in the mandible and maxilla?Maxilla, trabeculae are lace-like with small marrow spaces and run VERTICALLY; Mandible trabecular are larger and run horizontally
Why are trabeculae of the mandible denser near the crestal height?Cortical plate thinning near crystal height
What is senile bone?More radiolucent bone seen in old people
How do the medullary spaces of children and adults compare?Children have larger spaces, adults smaller spaces
What is subpontic hyperostosis?Bone growing up underneath pontic (of FPD) after filling in tooth socket
How far from the CDJ is the alveolar bone crest?1-1.5mm below CEJ
What are the two ways the alveolar boe crest recedes from the CEJ?parallel to CEJ (horizontal, normal), At an angle to CEJ (vertical, abnormal)
When/where is the lamina dura thicker?at the apices of an erupting tooth
When is lamina dura disrupted?caries can disrupt lamina dura
What does the PDL space sit between? How does it appear on a radiograph?Cementum & Cortical bone
Why might the PDL space appear disrupted on a radiograph?angulation error OR ankylose tooth OR pulpal/periapical infection
Triangular eminence in the inferior anterior aspect of the mandibleMental ridges

Caries Diagnosis

Question Answer
What make caries a dynamic process?can PROGRESS, REGRESS, or REMAIN STABLE
What percentage of the population is affected by caries?over 90%
Why are bitewings the gold standard of radiographic caries detection?lowest chance of vertical angulation error
What do we use PAs for in caries detection?class V or root caries (using paralleling technique)
Why does caries appear radiolucent?demineralized (30-50% loss)
How can we distinguish between active and arrested caries?Cannot distinguish
Why is angulation error bad when detecting caries on radiograph?can hide or misplace inter proximal caries
Why are caries always smaller on radiograph than in histological sections?because it passes through radiopaque tooth structure too
What amount of enamel lesions are detectable on radiograph?1/2 (HALF)
What developmental conditions mimic caries on radiograph?Amelogenesis Imperfecta, NCCL, Abrasion & Attrition
What is cervical burnout caused by? Why is it even worse below metallic restorationsdensity differences (worse w metal because exaggerated density difference)
How can you differentiate cervical burnout from proximal caries? Cervical caries?proximal caries just below contact, not at CEJ; cervical caries only when gingiva recessed to reveal cementum
Where do proximal caries start? What is their appearance radiographically? Clinically?just below inter proximal contacts; triangular point toward dentin
Why do occlusal caries begin at pits and fissures? Why are they triangular shaped with the apex toward the occlusal surfaceenamel rods converge at occlusal surface
What is the radiographic appearance of a facial/lingual surface lesion?smooth elliptical shape w/ sharp margins
What can a radiograph never tell us about a facial/lingual surface lesion?which it is, facial or lingual
What surface is most likely to have root caries?Facial surface, mandibular molar and premolar
Why are root caries more common on patients with periodontal problems?gingival recession

What is the depth of a lesion in the following categories of the old classification system? What percentage of each are caveated

Question Answer
D1outer half of enamel, never cavitated
D2inner half of enamel, 10 % cavitated
D3into outer half of dentin/DEJ, 40% cavitated
D4inner half of dentin, 100% cavitated

Describe the depth of the lesion in the following categories of the ADA classification system

Question Answer
a. InitialRadiolucency up to outer 1/3rd of dentin, visually NON cavitated
b. Moderate/establishedmiddle 3rd of dentin, MICROCAVITATION


Question Answer
Why do some older composites mimic recurrent decay?RADIO-LUCENT
Why do bases and liners mimic recurrent decay?radio-lucent
How can we differentiate old restorative materials and bases and liners from recurrent caries on radiograph?WELL-DEFINED BORDERS usually means old restorative (on an old patient)
How can we control radiographic density?kVp, mA, exposure time
What kind of contrast is ideal for detecting caries? What is the optimum kVp range?short-scale contrast, lower kVp (65-70)
Why are digital radiographs the best for caries interpretation?less exposure, digital tools for enhancement

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