Skull and facial bones

8 cranial bones

frontal bones, 2 parietal bones, 2 temporal bones, Occipital bone, Sphenoid bone, Ethmoid bones

Joints between cranial bones and immovable joints called sutures

coronal suture, Squamosal suture, Lambdoidal suture, Sagittarius suture

Petrous ridge

Part of temporal bone - helps from the skull base between the sphenoid and occitpital bones.

Forms the cavities for the inner ear

14 Facial bones

2 nasal bones, 2 maxillae, 2 zygomatic bones, The mandible, 2 lacrimal bones, 2 palatine bones, 2 inferior nasal conchae, The vomer

Mandible

Facial bones that forms lower jaw it has a body and 2 rami.

Consists of 2 halves that fuse in early life.

Zygomatic and lacrimal bone

2 facial bones that form cheeks and lateral walls of the orbits - cheek bones. Articulates with the temporal bone front bone.

Lacrimal bone

Smallest bone in face. Form part of the medial wall or each orbit. Each lacrimal bone contains lacrimal fossa. Articulates with maxilla and ethmoid bone

Vomer bone

Thin bone runs vertically along midline of the nasal cavity. Vertical plate of the vomer bone articulates with the perpendicular plate of the ethmoid bone .

Paranasal sinses

Are cavities in the bones of the fave and cranium

The oribitomeatal line (OML)

Runs from the nation through the outer can thus of the eye to the centre of the external auditory meatus (EAM)

The infraorbitomeatal line (IOML)

The anthropological baseline runs from the inferior orbital margin to the upper border of the eam

The interorbital line (IOL)

The IOL or interpupillary line connects the centers of the orbits and is perpendicular to the median sagittal plane.

PA skull positioning

patient is erect

Forehead and nose contact with the IR

EAM equidistant from IR

MSP and OML perpendicular to the IR

PA skull centering point

Along the MSP with the beam exiting at the nation

Collimation of PA skull

superior to the skin margins

Inferior to include the inferior of the skull

Lateral to include the skin margin

PA skull of 15 degree

Centering point - along the MSP with 15 degree caudal angulation to exit at the nasion

AP skull - FO

Positioning:

• patient erect or supine

• Back of patients head in contact with the IR (patient facing x-ray tube)

• EAM equidistant from IR

• MSP and OML perpendicular to the IR.

AP skull - FO centering point

along the MSP with the beam centred at the nasion

AP skull - FO collimation

superior to the skin margins

Inferior to include the most inferior aspects of the skull

Lateral to include the skin margin

AP axial skull - positioning

patient erect or supine

Back of patients head in contact with the IR

EAM equidistant from IR

MSP and OML perpendicular to the IR

AP axial skull - centering point

along the MSP with 30degree caudal angulation centered about 7cm above the glabella

Lateral skull - positioning

patient erect or supine

TMJs superimposed

MSP parallel to IR

Inter orbital line perpendicular to the IR

Lateral skull - centering point

4/5cm above EAM

Lateral skull - collimation

superior to include skin margins

Inferior to include base of skull

Anterior to include frontal bone

Posterior to the skin margins

Occipital mental (OM). Positioning

patient is erect facing up right

Chin raid with the RBL at 90degree angle from receptor

EAM equidistant to the IR

MSP perpendicular to the IR

Occipito - mental (OM) - centering point

Along the MSP with the beam exiting at the acanthion

Occiptio - mental (OM) - collimation

superior to the skin margins

Inferior to include the most inferior aspects of the skull

Lateral to include the skin margins

Occipito mental - mental 30 degree - positing

patient erect facing upright detector with the chin

Chin raid with RBL 45 degrees from receptor

EAM equidistant from IR

MSP perpendicular to the IR

Occiptio - mental 30 degree - centering point

30 degree caudal angulation along the MSP with beam exiting at the symphysis menti

PA mandible - positing

patient erect

Patients for head and nose in contact with IR

EAM equidistant from IR

MSP and OML perpendicular to the IR

PA mandible - centering point

Along the MSP at level of the angle of mandibles

Crown

Visible part of the tooth above the level of the gum

Neck of tooth

The junction of the crown and the root

Root of tooth

Between 1 or 3 roots per tooth, sit below th gum line and are embedded into the socket

Lateral oblique mandible positioning

patient erect with head in a lateral position with side of interest against IR.

Extend neck to clear the mandible of the cervical spine.

Rotate the head in an oblique direction (the degree of obliquity depend upon the section of interest)

Lateral oblique mandible centering

Central ray 25-30 degree cephalon, beam to exit at mandibular region of interest

Exposure factor OM/OM30/sinuses/OF/ Townes

70kv and 25mAs (use grid and AEC )

Lateral skull exposure factor

70kv and 20mAs (use grid and AEC)

Mandible PA exposure factor

70kv and 16mAs (use grid and AEC )

Mandible lateral/oblique exposure factors

60kv and 5mAs (no grid)

Palmers notation

Method used to designate individual teeth

Periapical

image the whole tooth and surrounding bone

Usually allow for the assessment of 2-4 teeth

Provide detail around the surround alveolar bone

Indications for periapical

apical infection/cyst

Impacted tooth

Root morphology to surgery

Evaluate implants

Periodical - parellel technique

Film Parnell to the long axis of the teeth so x-ray beam is at right angle

Periodical Parnell technique

film placed in mouth Parnell to the long axis of tooth being examined

Central ray of the x-ray beam is directed perpendicular to the film and long axis

Advantages of periapical parellel technique

reduces distortion

True anatomical relation

Reduced magnification

Disadvanatges of periapical parellel technique.

requires film holder which is hard to place in children, adults with small mouths.

Uncomfortable for the patient

Periapical - bisecting technique

Done when operator can not perform the parellel technique, sometimes called he short cone technique

Periapical - bisecting technique positioning

Film is placed close to the tooth

Angle is formed between the tooth and film bisected

Patient holds back of the film

Advantages of bisecting technique

no need for film holder

Comfortable for patient

Quicker

Bisecting technique Disadvanatges

higher chance of magnification and superimposition

Not reproducible

Bite wing

Patient bites on a tab to hold film in place. Include both maxilla and the mandible teeth. Interproximal area and bone one film

Indications for bite wing

detection of caries

Periodical review

Evaluate alveolar bone level

Evaluate pulp chamber

Occlusal

Expose all the maxilla or mandible

Indications for an occlusal

detect presence of unerupted teeth, supernumeraries and odontomes.

Orthopantomogram (OPG)

Panoramic single image radiograph of the mandible, maxilla and teeth.

Indications for OPG

general dental health evaluation caries for pulp origin

Trauma assessment for tooth or jaw fractures

Infection evaluation of periodontitis or periapical abscesses.

Advantages of OPG

Broad anatomical region

Less radiation than intro orals

View both sides of the jaw- uselful in assessment of fractures

Comparison of both condylar heads

Natural floor is seen

Disadvanatges of OPG

Does not have fine antomical detail that is seen on intra oral radiographs

soft tissue and air shadows can superimpose

Lateral cephalogram

Are acquired to evaluate the relationships between structures of the facial skeleton, primarily for orthodontic assessment

Indications for lateral cephalogram

dental/skeltal development, particularly in paediatrics

Analysis of dental/skeletal relationships

Treatment planning/ monitoring