Dental Equipment - OPG

Question 1

What are the main/basic principles of OPG imaging?

Answer 1

Simultaneous rotational movement of tubehead and image receptor around patients head

Moving x-ray tube blowers out shadow of overlying structure by placing dental arts in axis of tomographic movement

Some element of unsharpness when compare to radiographic images of other body parts using non-moving X-ray tube

Opens out – image of dental arch to appear in linear arrangement on final image

Question 2

What are the applications of OPG imaging?

Answer 2

Orthodontic assessment of present/absence of teeth

Detection and assessment of fractures of mandible

Assessment of large pathological legions – cyst, tumour

Assessment of third molars prior to surgical removal

Assessment of temporomandibular joint

When intraoral radiography is impossible

Question 3

What is the construction of the OPG machines?

Answer 3

Image receptor

Head clamps

X-ray tube

Bite Road/to rest

Handles

Question 4

 what is the radiographic technique of an OPG?

Answer 4

Patient has to remove bulky clothing e.g court, radiopaque objects from head/neck area – earings, hairclips et cetera – dentures too

Disposable bike rod inserted into tin rest – or disposable cover applied to permanent by blood

Procedure explained to patient

Patient stands or sits in machine with chin on rest, holding handles

Patient asked to step forward slightly to bring cervical spine vertical

Patient bites with their incisors in the groove on the back road

Stand behind patient and check position – make sure shoulders are relaxed

Close head restraint/camps

Use positioning lights on machine to: -check patient position – sagittal plane light down the middle face
-Anthropological baseline/electrical line horizontal – parallel to the floor
-Anteroposterior light to check head far enough forward

Remind patient that the exposure time is approximately 15 seconds and the importance of remaining still

Question 5

What is the criteria for assessing image quality of OPGs?

Answer 5

All of mandible demonstrated including symphysis menti infinity and condyle superiorly

Hard palate and maxillary Amtrak demonstrated

Dentition demonstrated in a horizontal line

Bike ride Sean between upper and lower central incisors – separation and of occlusal surfaces of teeth

All teeth seen relatively sharply

Slightly blurred shadow of anterior aspect of neck structures superimposed over images of incisors

Question 6

What are common errors seen in OPG imaging?

Answer 6

Usually calls by incorrect patient positioning:

Head too far forward – incisors appear very narrow, cervical vertebrae may be seen centrally

Head Too far back – broad, I’ll chop image of incisors

Chin too far down – curved occlusal plane, ill-defined lower incisors

Chin to far up – superimposition of maxillary antra on hard palate/upper teeth, ill-defined anterior teeth

Neck tilted – under exposed region in midline of image

Shoulders obstructing machine movement – dark band due to prolonged exposure in what region