XRAY 200 WEEK 3

Panoramic image

Shows a wide view of the upper and lower jaws

extraoral tech = outside mouth

Ghost Image

metal not removed

Problem

◦ If all metallic or radiodense objects are not removed before exposure, a ghost image results that obscure diagnostic information

Solution

◦ The dental radiographer must instruct the patient to remove all radiodense objects in the head and neck

region prior to positioning the patient

Lead apron artifacat

• Problem

◦ A radiopaque cone-shaped artifact that obscures diagnostic information results if the lead apron is incorrectly placed, or if a lead apron with a thyroid

collar is used (hoodies, spine straight stand tall)

Solution

◦ The dental radiographer must always use a lead

apron without a thyroid collar when exposing a

panoramic projection

Preperation errors

ghost image

lead apron artifact

Positioning of the lips and tongue

• Problem

◦ If the patient’s lips are not closed on the bite-block during the exposure of a panoramic projection, a dark radiolucent shadow results that obscures the

anterior teeth

◦ If the tongue is not in contact with the palate during exposure of a panoramic projection, a dark radiolucent shadow results that obscures the apices of the maxillary teeth

• Solution

◦ Instruct the patient to close the lips around the bite- block and swallow and raise the tongue up to the palate during the exposure of the receptor (tongue should be at the roof of your mouth)

Chin Tipped Up

• Problem

◦ If the patient’s chin is positioned too high a “reverse smile line” is apparent on the image

• Solution

◦ Position the patient so the Frankfort plane is parallel with the floor

Chin Tipped Down

• Problem

◦ If the patient’s chin is positioned too low or is tipped down an “exaggerated smile line” is apparent on the image

• Solution

◦ Position the patient so that the Frankfort plane is parallel with the floor

Teeth Anterior to the Focal Trough

• Problem

◦ If the patient’s teeth are positioned too far forward

on the bite-block or anterior to the focal trough, the

anterior teeth appear “skinny” and out of focus

• Solution

◦ Position the patient so that the anterior teeth are

placed in an end-to-end position in the groove on

the bite-block

Teeth Posterior to the Focal Trough

Problem

◦ If the patient’s teeth are positioned too far back on

the bite-block or posterior to the focal trough, the

anterior teeth appear “fat” and out of focus

• Solution

◦ Position the patient so that the anterior teeth are

placed in an end-to-end position in the groove on

the bite-block

Head Turned

Problem

◦ If the patient’s head is not centered, the ramus and

posterior teeth appear unequally magnified on the

panoramic image

▪ The side farthest from the receptor appears magnified

• Solution

◦ Position the patient’s head so that the midsagittal plane is

perpendicular to the floor while the midline is centered on

the bite-block

CBCT

Cone Beam Computed Tomography

Allows the viewing of the head and neck in 3 dimensions

How CBCT works

• rotates around patients head

• takes 200-600 images

• snips them together to create a 3d image

• 1CBCT = 3-4 FMS

• takes between 7-30 seconds to expose

CBCT Advantages

• doesn’t provide info about buccal or lingual width or locations

• cannot distinguish between types of soft tissues

Vital for

• Exact placement of implants

• buccal/lingual placement of impacted teeth

• determine location of mandibular nerve before surgery

Digital radiography

Digital imaging eliminates chemical processing and hazardous wastes (lead foil, chemicals)

• Requires LESS Radiation to expose

• Allows for digital enhancements, measurements and corrections

• Images can be electronically transferred to other health care providers

• Sensors are VERY expensive

Direct digital

Solid-state sensor that contains an x-ray sensitive silicon chip with an electronic circuit embedded in the silicon

Indirect Digital

PSP (phosphor storage imaging)

Thin, flexible plate that is covered in phosphor crystals

• Plates are the same size as conventional

x-ray film

• Phosphor layer stores energy of x-ray

photons

• After exposure plates are placed into a scanner

• Scanner laser reads the latent image and converts it to a digital

image

• Films are exposed to a bright light to ”erase” the image

Intraoral Radiography

There are three different types of intra-oral radiographs, that can be taken to asses the patients dentition (inside mouth)

Periapical (PA)

• shows entire tooth including root (entire tooth form occlusal surface or incisal edge)

• looks for disease in root

Biitewing (BW)

shows in between the teeth

shows top and bottom teeth, no roots

look for decay in between teeth

looking for bone height

Occlusal x ray

tooth development

Producing Diagnostically Acceptable Radiographs

Periapical Terminology

Long Axis of Tooth

An imaginary line that divides the tooth longitudinally into two equal halves.

cut in half

Central Ray

The central portion of the primary beam of radiation

The Paralleling Technique

• Receptor is parallel to long axis of tooth

• X-ray beam is perpendicular to the long axis of the

tooth

• Face of cone is parallel with the face of the film.

• Common errors:

incorrect placement and alignment.

Paralleling Technique Steps

Advantages and Disadvantages of the paralleling technique

x ray beams

Slumped Posture

Problem

◦ If the patient is not standing or sitting with a straight spine, the cervical spine appears as a radiopacity in the center of the receptor and obscures

diagnostic information

• Solution

Instruct the patient to stand or sit “as tall as possible” with a straight back