Occlusal Radiography

Question 1

What type of sensors are used in occlusal radiography?

Answer 1

Film or digital sensors.

Question 2

What type of plates for occlusal radiographs are used in the dental hospital?

Answer 2

Phosphor plates.

Question 3

What is the image receptor size for an occlusal radiograph?

Answer 3

7x5cm.

Question 4

What are the indications for an oblique occlusal?

Answer 4

Periapical type assessment where periapicals are not possible
Pathology too large to be seen on a single periapical
Trauma- fractures to teeth and alveolus
Localisation using paralax (plus panoramic, other occlusal or periapical).

Question 5

*remember you cant take an oblique occlusal if the patient has trismus or is a bad gagger.

Answer 5

.

Question 6

What type of occlusal would you take for an unerupted supernumerary tooth?

Answer 6

Upper anterior oblique occlusal.

Question 7

What could a circular radiolucency with a radiopaque line around it be?

Answer 7

A cyst.

Question 8

What is the ideal projection geometry for an occlusal radiograph?

Answer 8

Image receptor and object in contact and paralell
Parallel beam of X-rays
X-ray beam perpendicular to object plane and image receptor
Image size identical to object size.

Question 9

What are the problems of projection geometry?

Answer 9

Image receptor and object not in contact
Beams of x-ray not parallel
Xray beam central ray may or may not be perpendicular to object plane and image receptor
Image size not identical to object size due to magnification (divergent beam).

Question 10

Describe the bisecting angle technique (vertical angle selection)?

Answer 10

Image receptor and tooth touch at crown but apart at apex
(image receptor placed 2-3mm beyond incisal edge)

IF the xray beam is at 90 degrees to the long axis of the tooth= elongated image
IF the image beam is at 90 degrees to plane of image receptor= short image (foreshortened)
*x-ray beam at 90 degrees to line bisecting angle formed by long axis of tooth and plane of image receptor- correct due to identical triangles.

Question 11

How do you adjust the angle to adapt to incisal angulation during the bisecting angle technique?

Answer 11

Proclined= increase

Retroclined- decrease.

Question 12

What are the head positions for an oblique occlusal?

Answer 12

Maxilla: ala-tragus line horizontal (parallel to the floor)

Mandible: corner of mouth-tragus line horizontal (parallel to the floor)

(FOR SEATED UPRIGHT PATIENTS).

Question 13

What is important about the head positioning during a maxillary occlusal?

Answer 13

Upper teeth are stable

Ala-tragus line (lateral border nose opening- anterior to external auditory meatus).

Question 14

What is important about the head positioning during a mandibular occlusal?

Answer 14

Teeth apart due to image receptor
Mandibular occlusal plane not same as maxillary
Head tilted back
Corner of mouth to tragus of ear.

Question 15

What are storage plate phosphor sensors?

Answer 15

Multi use sensors
Protected by plastic covers
Protected from tooth marks by cardboard (single use) or plastic (multi-use)
Insert into plastic so writing can be seen through clear side then seal
Black side of cover must face x-ray source.

Question 16

How do you ensure that the phosphor plate is protected?

Answer 16

Check correctly positioned in plastic cover
Place inside hinged card protector
Check dark surface of cover facing up for maxillary teeth, down for mandibular teeth
Position in mouth, hinged end first

Question 17

How do you get the sensor to keep still in the correct position?

Answer 17

Patient to bite gently to hold protected sensor still
Remind them to keep biting gently
Watch them to ensure there is no chewing action
Plastic protectors can be used as an alternative to card.

Question 18

What are the centering points for periapicals?

Answer 18

Maxilla: on ala-tragus line
Mandible: 1cm above lower border of mandible.

Question 19

What are the centering points of oblique occlusals?

Answer 19

Maxilla: 1cm above ala-tragus line
Mandible: through lower border of the mandible.

Question 20

What are the guide line vertical angles for oblique occlusals?

Answer 20

Upper anterior- 60 (degrees)
Upper occlusal centred on canine- 55
Upper occlusal centred on premolar- 50
Upper occlusal centred on molar- 45
Lower anterior occlusal- 40 degrees to occlusal plane
Lower occlusal centred laterally- 35 d to occlusal plane.

Question 21

Does white or black in the film packet go to the teeth of interest?

Answer 21

White.

Question 22

What are the indications for a mandibular true occlusal?

Answer 22

Detection of submandibular duct calculi
Assessment of bucco-lingual position of unerupted (unless advanced imaging indicated)
Evaluation of pathological bucco-lingual expansion **
Horizontal displacement of fractures

**cone beam CT may be used nowadays if available.

Question 23

What are the two types of growth you can see on an occlusal radiograph of a submandibular duct calculi?

Answer 23

Concentric growth

Conforms to duct.

Question 24

What are the key points to consider when doing a mandibular true occlusal radiograph?

Answer 24

Image receptor transverse in occlusal plane or lengthwise over region of interest
Head tipped as far back as is comfortable
X-ray beam directed at 90 degrees to image receptor in midline OR through region of interest.