Exam 3 Review (Ch. 25-29)

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Purpose and use of Panoramic imaging

An overall image of the maxilla and mandible

-Often used to supplement bite-wing and selected periapical images

•Images seen on a panoramic projection are not as defined or sharp as the images seen on intraoral projections

What is Tomography

This is an imaging technique that allows the imaging of one layer or section of the body while blurring images from structures in other planes

The pivotal point, or axis, around which the cassette carrier and x-ray tubehead rotate is the?

rotational center

What is the Focal trough

three-dimensional curved zone in which structures are clearly demonstrated on a panoramic image

What do Modern panoramic x-ray units use rather than multiple fixed center locations

continuously moving center of rotation

Define Real Image

Results when a structure lies between the receptor and moving rotation center

Define double image

Results when an anatomic structure that is located behind the moving rotation center is penetrated twice by the x-ray beam

Define ghost image

Results when an anatomic structure or object is located outside of the focal plane and close to the x-ray source

How does the collimator differ in a panoramic x-ray unit?

-The collimator used in the panoramic x-ray machine is a lead plate with an opening in the shape of a narrow vertical slit

The x-ray beam emerges from the panoramic tubehead through the collimator as a narrow band

➢It passes through the patient and exposes the receptor through another vertical slit in the cassette carrier

➢The vertical angulation is fixed so that the x-ray beam is directed slightly upward

Used to align the patient's teeth as accurately as possible and includes:

-Chin rest

-Notched bite block

-Forehead rest

-Lateral head supports

In panoramic x-ray units, the image receptor may be:

direct digital sensor, a PSP plate, or film

Step-by-Step Procedures

•Equipment preparation

•Patient preparation

•Patient positioning

When should the Dental radiographer complete the panoramic imaging equipment preparations

before preparing patient for exposure

Patient Preparation requires what?

Explain the imaging procedures

•Place a lead apron without a thyroid collar

-A double-sided lead apron is recommended

•Remove all objects from the head and neck area that may interfere with the procedure

What to do for Patient positioning?

Instruct the patient to sit or stand "as tall as possible" with the back straight and erect

•Instruct the patient to bite on the plastic bite-block

•Position the midsagittal plane perpendicular to the floor

•Position the Frankfort plane parallel with the floor

Instruct the patient to position the tongue on the roof of the mouth and close lips around the bite block during exposure

•Instruct the patient to remain still while the machine is rotating during exposure

What is critical for a panoramic image

Proper contrast on a panoramic image is critical; should be able to identify enamel and dentin in the molar region

Common Patient preparation errors:

-Ghost images

-Lead apron artifact

Common Patient positioning errors:

-Positioning of the lips and tongue

➢Chin tipped up

➢Chin tipped down

➢Teeth anterior to the focal trough

➢Teeth posterior to the focal trough

➢Head turned

➢Slumped posture

Where is an object found on a ghost image?

➢It is found on the opposite side of the receptor

➢It appears indistinct, larger, and higher than its actual counterpart

What is the cause of a ghost image?

An imaging artifact seen on a panoramic image that is produced when a metallic or dense object is penetrated twice by the x-ray beam

What causes a Lead apron artifact?

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

What causes a dark radiolucent shadow results that obscures the anterior teeth?

If the patient's lips are not closed on the bite-block

What causes a dark radiolucent shadow results that obscures the apices of the maxillary teeth?

If the tongue is not in contact with the palate

What causes a reverse smile line?

chin tipped up

How to get rid of a reverse smile line?

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

What causes an exaggerated smile line?

Chin tipped down

How to fix an exaggerated smile line?

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

What causes the anterior teeth to be skinny and out of focus?

Teeth are positioned too far forward on the bite-block or anterior to the focal trough

What causes the anterior teeth to be fat and out of focus?

Teeth are positioned too far back on the bite-block or posterior to the focal trough

What causes the ramus and posterior teeth appear unequally magnified on the panoramic image

If the patient's head is not centered

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

What causes the cervical spine appears as a radiopacity in the center of the receptor

Not standing or sitting with a straight spine

Advantages of

Panoramic Radiography

•Field size

•Simplicity

•Patient cooperation

•Minimal exposure

Disadvantages of

Panoramic Radiography

-image quality

-focal trough limitations

-distortion

-equipment cost

Extraoral imaging

An image that is placed outside the mouth during x-ray exposure

➢Used to image large areas of the skull or jaws

Purpose and use of extraoral imaging

•To evaluate large areas of the skull or jaws

•To evaluate growth and development

•To evaluate impacted teeth

•To detect diseases, lesions, and conditions of the jaws

•To examine the extent of large lesions

•To evaluate trauma

•To evaluate the temporomandibular joint area

Equipment for extraoral imaging

•X-ray unit

•Image receptors

•Intensifying screens

•Cassette

•Grid

X-ray Unit for extraoral imaging

•A standard intraoral x-ray machine may be used for a variety of extraoral projections

➢Special head positioning and beam alignment devices can be added

➢Some panoramic x-ray units can be used for extraoral projections

•The panoramic tubehead is used in conjunction with a special extension arm and a device known as a cephalostat or craniostat

Image receptors for extraoral imaging

•Extraoral imaging may be digital or film-based

•Most extraoral exposures are made with screen film placed in a cassette with intensifying screens

➢Screen film is sensitive to the light emitted from intensifying screens

•An occlusal film is a nonscreen film that may be used for some extraoral images

➢Does not cover as large of an area as does a screen film

Diagnostic Extraoral Imaging

•Must demonstrate accurate anatomic features and proper density and contrast

•Anatomic features vary depending on the extraoral projection

•Proper density and contrast result from use of correct exposure factors as recommended by the x-ray unit manufacturer

Step-by-Step Procedures for extraoral imaging

•Essentially, same as panoramic procedure

•Equipment preparation

•Patient preparation

•Patient positioning

•Infection control procedures must be complete before exposing an extraoral receptor

➢If an extraoral unit with cephalostat is used, the ear rods must be wiped with disinfectant between patients

Extraoral Projection Techniques

•Lateral jaw imaging

•Skull imaging

•Extraoral bite-wing imaging

•Temporomandibular joint imaging

Lateral jaw imaging

•Used to examine the posterior region of the mandible, either the Body or Ramus

•Purpose

➢To evaluate impacted teeth, fractures, and lesions located in the body of the mandible

Skull imaging

•Used to examine the bones of the face and skull, most often with oral surgery or ortho

➢Lateral cephalometric projection

➢Posteroanterior projection

➢Waters projection

➢Submentovertex projection

➢Reverse Towne projection

➢Temporomandibular joint (TMJ)

Lateral Cephalometric Projection

Purpose

➢To evaluate facial growth and development, trauma, and disease and developmental abnormalities

Posteroanterior Projection

Purpose

➢To evaluate facial growth and development, trauma, and disease and developmental abnormalities

Waters projection

Purpose

➢To evaluate the maxillary sinus area

Submentovertex Projection

Purpose

➢To identify the position of the condyles, demonstrate the base of the skull, and evaluate fractures of the zygomatic arch

Reverse Towne Projection

Purpose

➢To identify fractures of the condylar neck and ramus area

Extraoral Bite-Wing Imaging

Purpose

➢To provide diagnostic information about the maxillary and mandibular teeth, interproximal regions, the periapical bone, and surrounding structures

➢Similar to traditional bite-wing image, but with larger view of anatomic structures

Temporomandibular Joint Imaging

The joint includes the temporal bone and the mandible

➢Transcranial projection

➢Temporomandibular joint tomography

Transcranial Projection

Purpose

➢To evaluate the superior surface of the condyle and the articular eminence

Temporomandibular Joint Tomography

Used to examine the temporomandibular joint

➢The location of the rotational point determines what plane of the head of the TM joint will be imaged

Three-Dimensional

Digital Imaging terminology

Cone beam computed tomography (CBCT) and Cone beam volume tomography (CBVT)

➢Terms used to describe 3-D digital imaging in dentistry, different from medical CT

•DICOM data - universal format for handling, storing and transmitting 3-D images

•Axial plane - horizontal - superior & inferior

•Coronal plane - vertical - anterior & posterior

•Sagittal plane - vertical - left & right

•Multiplanar reconstruction (MPR) - when all three planes are viewed together

•Field of view (FOV)- area captured

•Resolution, contrast - grey scale colors

•Resolution, spatial - pixel size

•Three-dimensional digital imaging - image that demonstrates anatomy in 3 dimesions

•Three-dimensional volume rendering - a 3 dimensional shape created by 2 dimensional images

•Voxel - smallest element of a 3 dimensional image

Three-dimensional digital imaging fundamentals

➢A method designed to evaluate the oral-maxillofacial complex

➢Named because it uses a cone-shaped x-ray beam to acquire three-dimensional information

➢Source of radiation rotates around the head of the patient

DICOM images fundamentals

➢These allow practitioner to see field of view in three dimensions

➢They are viewed in three planes: Axial plane, coronal plane, and sagittal plane

➢When viewed together images are referred to as "multiplanar reconstructed images"

➢They can be shared amongst dental professionals

Three-Dimensional

Digital Imaging equipment

Specialized equipment

•CBCT machine

➢Comparable in size to a panoramic machine

➢Patient sits, stands, or is placed in a supine position

➢In one rotation, radiation and receptor capture field of view

•Computer

➢Accepts raw data and converts them into stack of axial images

➢Technique is completed during the data reconstruction process

•Viewing software

➢Allows dental practitioner to view axial, coronal, and sagittal images

Common uses of three-dimensional imaging

•Greatly improve interpretation, diagnosis, and treatment planning of dental care

•Implant placement

•Extraction or exposure of impacted teeth

•Definition of anatomic structures

•Endodontic assessment

•Airway and sinus analysis

•Evaluation of temporomandibular joint disorders

•Orthodontic evaluation

•Evaluation of lesions and abnormalities

•Trauma evaluation

Patient Preparation for three-dimensional imaging

•Patients may be asked to sit or stand or be placed in the supine position during radiation exposure

•Instructions are given to the patient before exposure to remove jewelry, eyeglasses, and removable dental appliances

•A guide may be placed in the patient's mouth during the scanning process

•Some specialists may ask that the upper and lower teeth be kept apart

Patient Positioning three-dimensional imaging

•Patient is instructed to remain still

•Scan times vary from 7 to 30 seconds

•Ergonomic head and chin supports have been designed for improved patient comfort

•Laser beams may be installed to help with proper alignment of clinical structures and to ensure correct anatomic positioning

Advantages of Three-

Dimensional Digital Imaging

•Lower radiation dose

•Brief scanning time

•Anatomically accurate images

•Ability to save and easily transport images

Disadvantages of Three-

Dimensional Digital Imaging

•Patient movement and artifacts

•Size of the field of view

•Cost of equipment

•Lack of training in interpretation of image on data on areas outside the maxilla and the mandible

Normal Anatomy:

Intraoral Images; Definitions of General Terms

•Types of bone

➢Cortical bone

➢Cancellous bone

•Prominences of bone

•Spaces and depressions in bone

•Miscellaneous terms

Types of bone

•Cortical bone

➢The dense outer layer of bone

➢Appears radiopaque on an image

•Cancellous bone

➢The soft, spongy bone located between two layers of dense cortical bone

➢Appears primarily radiolucent

-Trabeculae appear radiopaque, marrow spaces appear radiolucent

Prominences of Bone

•Process: Marked prominence or projection

•Ridge: Linear prominence or projection

•Spine: Sharp, thornlike projection

•Tubercle: Small bump or nodule

•Tuberosity: Rounded prominence

Spaces and Depressions in Bone

•Canal: Tubelike passageway through bone that contains nerves and blood vessels

•Foramen: Opening or hole that permits the passage of nerves and blood vessels

•Fossa: Broad, shallow, scooped-out, or depressed area

•Sinus: Hollow space, cavity, or recess

Miscellaneous Terms

•Septum

➢Bony wall or partition that divides two spaces or cavities

➢Radiopaque

•Suture

➢Immovable joint representing a line of union between adjoining bones of the skull

➢Thin radiolucent line

Bony Landmarks of the Maxilla pt 1

•The upper jaw is composed of two paired bones, the maxillae

➢The paired maxillae meet at the midline of the face

•Forms the:

➢Floor of the orbit of the eye

➢Sides and floor of the nasal cavities

➢Hard palate

Bony Landmarks of the Maxilla pt2

•Incisive foramen

•Superior foramina of the incisive canal

•Median palatal suture

•Lateral fossa

•Nasal cavity

•Nasal septum

•Floor of the nasal cavity

Bony Landmarks of the Maxilla pt3

•Maxillary sinus

➢Septa within the maxillary sinus

➢Nutrient canals within the maxillary sinus

•Inverted Y

•Maxillary tuberosity

•Hamulus

•Zygomatic process of the maxilla

Incisive Foramen

(Nasopalatine Foramen)

•Description

➢Opening or hole in bone that is located at the midline of the anterior portion of the hard palate directly posterior to the maxillary central incisors

•Appearance

➢Small ovoid or round radiolucent area located between the roots of the maxillary central incisors

Superior Foramina

of the Incisive Canal

•Description

➢Two tiny openings or holes in bone that are located on the floor of the nasal cavity

➢Join together to form the incisive canal

•Appearance

➢Two small round radiolucencies located superior to the apices of the maxillary central incisors

Median Palatal Suture

•Description

➢Immovable joint between the two palatine processes of the maxilla

•Appearance

➢Thin radiolucent line between the maxillary central incisors

Lateral Fossa

•Description

➢Smooth, depressed area of the maxilla located just inferior and medial to the infraorbital foramen between the canine and lateral incisors

•Appearance

➢Radiolucent area between the maxillary canine and lateral incisors

Nasal cavity

•Description

➢Pear-shaped compartment of bone located superior to the maxilla

-The inferior portion is formed by the palatal processes of the maxilla and the horizontal portions of the palatine bones

•Appearance

➢Large radiolucent area above the maxillary incisors

Nasal Septum

•Description

➢Vertical bony wall or partition that divides the nasal cavity into the right and left nasal fossae

•Appearance

➢Vertical radiopaque partition that divides the nasal cavity

Floor of the Nasal Cavity

•Description

➢Bony wall formed by the palatal processes of the maxilla and the horizontal portions of the palatine bones

•Appearance

➢Dense radiopaque band of bone above the maxillary incisors

Maxillary Sinus

•Description

➢Paired cavities or compartments of bone located within the maxilla

➢Located above the maxillary premolar and molar teeth

•Appearance

➢Radiolucent area located above the apices of the maxillary premolars and molars

Septa within the Maxillary Sinus

•Description

➢Bony walls or partitions that appear to divide the maxillary sinus into compartments

•Appearance

➢Radiopaque lines within the maxillary sinus

➢Presence and number vary depending on the anatomy of the individual

Nutrient Canals within

the Maxillary Sinus

•Description

➢Tiny, tubelike passageways through bone that contain blood vessels and nerves

•Appearance

➢Narrow radiolucent band bounded by two thin radiopaque lines

The inverted Y

•Description

➢Intersection of the maxillary sinus and the nasal cavity

•Appearance

➢Radiopaque upside-down Y

➢Located above the maxillary canine

Maxillary Tuberosity

•Description

➢Rounded prominence of bone that extends posterior to the third molar region

•Appearance

➢Radiopaque bulge distal to the third molar region

Hamulus

•Description

➢Small hooklike projection of bone extending from the medial pterygoid plate of the sphenoid bone

•Appearance

➢Radiopaque hooklike projection posterior to the maxillary tuberosity area

Zygomatic Process of the Maxilla

•Description

➢Bony projection of the maxilla that articulates with the zygoma or malar (cheek) bone

•Appearance

➢J- or U-shaped radiopacity located superior to the maxillary first molar region

Bony Landmarks of the Mandible

•The largest and strongest bone of the face

•Divided into three main parts

➢Ramus

-Vertical portion found posterior to the third molar

➢Body

-Horizontal U-shaped portion from ramus to ramus

➢Alveolar process

-Encases and supports the teeth

Bony Landmarks of the Mandible pt2

•Genial tubercles

•Lingual foramen

•Nutrient canals

•Mental ridge

•Mental fossa

•Mental foramen

•Mandibular canal

•Mylohyoid ridge

•External oblique ridge

•Anterior border of the ramus

•Coronoid process

Genial Tubercles

•Description

➢Tiny bumps of bone on the lingual aspect of the mandible

•Appearance

➢Ring-shaped radiopacity below the apices of the mandibular incisors

Lingual Foramen

•Description

➢Tiny opening or hole in bone located on the internal surface of the mandible

•Appearance

➢Small radiolucent dot inferior to the apices of the mandibular incisors

Nutrient Canals

•Description

➢Tubelike passageways through bone containing nerves and blood vessels that supply the teeth

➢Most often seen in anterior mandible

•Appearance

➢Vertical radiolucent lines readily seen in areas of thin bone

Mental Ridge

•Description

➢Linear prominence of cortical bone located on the external surface of the anterior portion of the mandible

•Appearance

➢Thick radiopaque band that extends from the premolar region to the incisor region

Mental fossa

•Description

➢Scooped-out, depressed area of bone located on the external surface of the anterior mandible

•Appearance

➢Radiolucent area above the mental ridge

Mental foramen

•Description

➢Opening or hole in bone located on the external surface of the mandible in the region of the mandibular premolars

•Appearance

➢Small ovoid or round radiolucent area located in the apical region of the mandibular premolars

➢Frequently misdiagnosed as a periapical lesion

Mandibular canal

•Description

➢Tubelike passageway through bone that travels the length of the mandible

➢Houses the inferior alveolar nerve and blood vessels

•Appearance

➢Radiolucent band outlined by two thin radiopaque lines that represent the cortical walls of the canal

Mylohyoid ridge

•Description

➢Linear prominence of bone located on the internal surface of the mandible

•Appearance

➢Dense radiopaque band that extends downward and forward from the molar region

External Oblique Ridge

• Description > Linear prominence of bone located on the external

surface of the body of the mandible

• Appearance > Radiopaque band extending downward and forward from the anterior border of the ramus of

the mandible

Anterior Border of the Ramus

•Description

➢Anterior border of the ramus extends vertically downward from the coronoid process to the external oblique ridge

•Appearance

➢On a molar bite-wing image, the descending ramus of the mandible may be seen as a slightly radiopaque vertical band posterior to the maxillary and mandibular molars

Coronoid process

•Description

➢Marked prominence of bone on the anterior ramus of the mandible

•Radiographic appearance

➢Triangular radiopacity superimposed over, or inferior to, the maxillary tuberosity region

Tooth Structures:

•Enamel: Outermost radiopaque layer of the crown of a tooth

•Dentin: Comprises most of the tooth structure, not as radiopaque as enamel

•Dentino-enamel junction (DEJ): Junction between dentin and enamel

•Pulp cavity: A pulp chamber and pulp canals

Anatomy of Alveolar Bone

•Anatomic landmarks of the alveolar process include:

lamina dura

alveolar crest

periodontal ligament space

Lamina Dura

•Description

➢The wall of the tooth socket

➢Made of dense cortical bone

•Appearance

➢Dense radiopaque line that surrounds the root of a tooth

Alveolar Crest

•Description

➢The most coronal portion of the alveolar bone found between teeth

•Appearance

➢Appears radiopaque, typically 1.5 to 2.0 mm below the cementoenamel junction