DENTAL RADIOLOGY

DR. NUHAD

-------------------------------------------------------- Extra-oral Radiographic Technique

Extra-oral radiograph is defined as examination made of the head and

facial region using film located outside the mouth.

• They allow the dentist to view large area of the jaw and skull on a

single radiograph not covered by intraoral film.

:soral radiograph-of extraMain indications

• Examine large areas of the jaws and Skull.

• Study growth and development of bone and teeth

• Detect fractures and evaluate trauma

• Detect pathological lesions and Diseases of the jaws

• Detect and evaluate impacted teeth.

• Evaluate TMJ Disorders.

Uses of extra-oral radiographs:

Orthodontists : Uses lateral cephalometric radiograph to:

Measure and compare changes in growth and development of bone and

teeth through pre & progress and post treatment records.

Prosthodontists: Use Facial profile radiographs (lateral cephalometric)

to record :

• The contour of the lips and the face

• The relationship of the teeth before removal, this will help them

construct prosthetic appliances that look natural.

Oral surgeons: use extra-oral radiographs extensively to:

• Evaluate trauma.

• Determine the location and extent of fractures.

• Locate impacted teeth & abnormalities.

• Malignancies.

• Injuries to TMJ

Extra-oral Radiographic techniques:

Lateral jaw projection

• Known also as lateral oblique projection

• It has been largely replaced by panoramic radiographs but still taken

when image details is needed.

Main indications:

• Examine the posterior region of the mandible.

• Valuable for use in children, and in patients who have difficulty in

stabilizing or tolerating intraoral film placement

• Patients with limited jaw opening due to a fracture or swelling .

• Evaluate the condition of the bone and to locate impacted teeth or large

lesions.

The film in this extraoral projection technique is positioned lateral to

the jaw during exposure.

• Body of mandible projection.

Purpose:The purpose of this film is to evaluate impacted teeth, fractures

and lesions located in the body of the mandible.This projection

demonstrates the mandibular premolar and molar regions as well as the

inferior border of the mandible.

• Ramus of mandible projection.

This gives a view of the ramus from the angle to the condyle. It is also

useful for examining the impacted maxillary and mandibular third

molar regions.

Technique:

• The film is kept first against the cheek of the required side and is

centered over the body for body projection or over ramus for ramus

projection of mandible . The patients head is titled 15 degree to the side

being imaged and the chin is elevated and extended upwards.

• The central x-ray beam is directed perpendicular to the horizontal

plane of the cassette with a vertical angulation of -15 to -20 degrees.

X-ray beam is directed posterio- anteriorly from the opposite side

A- Cassette and X-ray tubehead position for the RIGHT mandibular

molars. Note the upward angulation of the X-ray tubehead and its

position beneath the left body of the mandible.

LATERAL OBLIQUE RADIOGRAPH

Skull Radiography

Skull radiography is used to examine the bones of the face and skull and

is most often used in oral surgery and orthodontics. Although some skull

films can be exposed using a standard intraoral X-ray machine, most

require the use of an extraoral unit and cephalostat .

The most common skull radiographs used in dentistry are:

• Cephalometric projection.

• Posteroanterior projection.

• Occipitomental (Waters view) projection.

• Submentovertex projection.

• Reverse Towne’s projection

• TMJ Projections

Cephalometric Radiographs

• may be either frontal (posteroanterior) or lateral skull projections

• Device called cephalostats have ear rods that stabilizes the patient’s

head parallel to the film and at right angle to the direction of the beam

• The cephalometer allows the Exposure to be taken several times for the

same patient in the same head position.

Lateral skull (cephalometric ) projection:

• It shows the entire skull from the side and the X-ray passes from the

lateral side

Purposes:

• Orthodontic purpose :

1.Pre and post treatment records.

2.Evaluate the growth and development

3.Facial soft tissue profile of the face

• Surgeons also use it for pre and post treatment records

• Trauma • Pathology • Developmental Abnormalities

Technique

• In this projection, the head is positioned so that the midsagittal plane is

parallel to the film and a line connecting the external auditory meatus is

perpendicular to the film.

•The central ray is perpendicular to the midsagittal plane and

perpendicular to the plane of the film and is centered over the external

auditory meatus.

• If the facial soft tissue profile is desired , a wedge filter is placed over

the anterior side of the beam at the tube head so that filter will absorbs

some of the x-rays in the anterior region.

Posteroanterior (PA) skull projection:

• Shows the entire skull in a posteroanterior plane.

• The beam passes through the skull in a posterior to anterior direction.

Purpose: • Asymmetry . • Disease • Trauma • Developmental

abnormalities

The PA radiograph with the major anatomical features drawn in.

Water’s projection (occipitomental view) :

• Also known as sinus projection

• It’s similar to the posteroanterior projection Except that the center of

interest is focused on the middle third of the face.

Purpose. The purpose of the Waters projection is to evaluate the

maxillary sinus , the frontal and ethmoid sinuses.

The standard occipitomental radiograph with the major anatomical

features drawn in.

• Reverse Towne’s projection

Purpose. The purpose of the reverse Towne projection is to identify

fractures of the condylar neck .

Reverse Towne’s radiograph with the major anatomical features

drawn in.

Submentovertex projection

Purpose. The purpose of this projection is to:

•Identify the position of the condyles.

• Demonstrate the base of the skull.

• Evaluate fractures of the zygomatic arch.

This projection also demonstrates the sphenoid sinus.•

Submentovertex radiograph with the major anatomical features drawn in.

TMJ Projections

1- Transcranial view:

Transcranial view helps in visualization of superior surface of the

condyle and the articular eminence. The joint space is also visualized.

2- Transpharyngeal projection:

This projection demonstrates the angular process from the mid

mandibular ramus to the condyle. This technique helps in the diagnosis of

fractures of the condyle and the condyle neck and in detecting alterations

in condyle morphology .

3- Transorbital view :

Transorbital view helps in the visualization of the joint with relatively

less super imposition. This view demonstrates the entire latero-medial

articulating surface of both the condyle and the articular eminence and

the condylar neck. During the exposure, the patient is asked to open the

mouth as wide as possible.