Radiology - Lateral cephalometry

Question 1

describe the interpupillary reference line.

Answer 1

An imaginary line drawn from the centre of the left pupil to the centre of the right pupil

Question 2

describe the orbito-meatal reference line.

Answer 2

outer corner of the eye to the centre of the external acoustic meatus

Question 3

describe the frankfort plane.

Answer 3

superior border of EAM to the lower borer of the orbit

Question 4

what are the two types of lateral radiography.

Answer 4

true

oblique

Question 5

define true lateral radiography

Answer 5

Film/digital receptor and the mid sagittal plane are parallel and x-ray beam is perpendicular

Question 6

define oblique lateral radiography

Answer 6

Film/digital and MSP are not parallel (patients head is turned), beam is not perpendicular to either MSP or film but oblique to both. (A left and right side has to be taken)

Question 7

what are the indication for use of oblique lateral radiology? (1)

Answer 7

When panoramic are not available or possible e.g. handicapped patient, obese etc

Question 8

what is seen on lateral cephs? (5)

Answer 8

• Facial bones
• Base of skull
• Upper cervical spine
• Paranasal sinuses
• Nasopharyngeal soft tissues

Question 9

when are lateral cephs used in orthodontics? (4)

Answer 9

in Patients with skeletal vertical or antero-posterior discrepancy.

inPatients requiring fixed or functional appliances for labio-lingual movement of incisors

in Patients requiring orthognathic surgery alongside orthodontic therapy (can use CBCT instead)

in Implant planning (can use pre-op CBCT instead)