Ct scan and its interpretation in omfs

CT SCAN
AND
ITS INTERPRETATION IN OMFS
GUIDED BY:
DR. S.RAVIRAJA KUMAR, M.D.S
PROF&HOD
DEPT OF OMFS
SJDC
PRESENTED BY
V.ANUSHA
IInd YEAR PG
DEPT OF OMFS

Introduction
• Definition / facts about CT
• Computer tomography (CT), originally known as computed axial
tomography (CAT or CT scan) and body section rentenography.
• It is a medical imaging method employing tomography where digital
geometry processing is used to generate a three-dimensional image of the
internals of an object from a large series of two-dimensional X-ray
images taken around a single axis of rotation.

• The word "tomography" is derived from the Greek
tomos (slice) and graphein (to write).
• CT produces a volume of data which can be manipulated,
through a process known as windowing, in order to
demonstrate various structures based on their ability to block
the X- ray beam.

HISTORY
• The first commercially viable CT scanner was invented by Godfrey Newbold Hounsfield in
Hayes, England at Thorn EMI Central Research Laboratories using X-rays.
Hounsfield conceived his idea in 1967, and it was publicly announced in 1972.
• It is claimed that the CT scanner was "the greatest legacy" of the Beatles; the massive profits from
their record sales enabled EMI to fund scientific research.
• Allan McLeod Cormack of Tufts University, Massachussetts,USA independently invented a similar
process and they shared a Nobel Prize in medicine in 1979.

• The original 1971 prototype took 160 parallel readings through 180
angles, each 1° apart, with each scan taking a little over five
minutes.
• The images from these scans took 2.5 hours to be processed by algebraic
reconstruction techniques on a large computer.
• The first production X-ray CT machine (called the EMI-Scanner)
was limited to making tomographic sections of the brain, but
acquired the image data in about 4 minutes (scanning two adjacent
slices)and the computation time (using a Data General Nova
minicomputer) was about 7 minutes per picture.
• This scanner required the use of a water-filled Perspex tank with a
pre-shaped rubber "head-cap"at the front, which enclosed the
patient's head. The water-tank was used to reduce the dynamic
range of the radiation reaching the detectors (between scanning
outside the head compared with scanning through the bone of the
skull).

GENERATIONS
generation configuration detector beam Min scan
time
first Translate-rotate 1-2 Pencil thin 2.5min
Second Translate-rotate 3-52 Narrow fan 10sec
Third Rotate-rotate 256-1000 Wide fan 0.5sec
Fourth Rotate- fixed 600-4800 Wide fan 1sec
fifth Electron beam 1284 Wide fan-
electron
beam
33ns

1st AND 2nd GENERATION
• In the first and second generation designs, the X-ray beam was not
wide enough to cover the entire width of the 'slice' of interest.
• A mechanical arrangement was required to move the X-ray source
and detector horizontally across the field of view.
• After a sweep, the source/detector assembly would be rotated a
few degrees, and another sweep performed.
• This process would be repeated until 360 degrees (or 180 degrees)
had been covered. The complex motion placed a limit on the
minimum scan time at approximately 20 seconds per image.

3rd AND 4th GENERATION
• In these generations the x-ray beam will cover the
entire field of view of the scanner.
• This avoids the need for any horizontal motion; an
entire 'line' can be captured an instant.
• This allowed simplification of the motion to rotation
of the x-ray source.

• Third and fourth generation designs differ in the
arrangement of the detectors.
• In 3rd generation, the detector array is as wide as
the beam, and must therefore rotate as the source
rotates.
• In 4th generation, an entire ring of stationary
detectors are used.

ELECTRON BEAM CT
• EBCT was introduced in the early 1980’s by
medical physcist Andrew castagnini
• It ia method of improving the temporal
resolution of ct scanners.
• Because the x-ray source has to rotate by over
180 degrees inorder to capture image the
technique is inherently unable to capture
dynamic movements or events that are quicker
than the rotation time.

• Instead of rotating a conventional X-ray tube around
the patient, the EBCT machine houses a huge vacuum
tube in which an electron beam is electro-magnetically
steered towards an array of tungsten X-ray anodes
arranged circularly around the patient.
• Each anode is hit in turn by the electron beam and emits X-
rays that are collimated and detected as in conventional CT.

•The lack of moving parts allows very quick
scanning, with single slice making the
technique ideal for capturing images of the
heart.
•EBCT has found particular use for assessment
of coronary artery calcium, a means of
predicting risk of coronary artery disease.

HELICAL OR SPIRAL CT
• Helical, also called spiral, CT was introduced in the early 1990s, with much of the
development led by Willi Kalender and Kazuhiro Katada.
• In older CT scanners, the X-ray source would move in a circular fashion to
acquire a single 'slice', once the slice had been completed, the scanner table
would move to position the patient for the next slice; meanwhile the X-ray
source/detectors would reverse direction to avoid tangling their cables.

• In helical CT the X-ray source are attached to a freely
rotating gantry.
• During a scan, the table moves the patient smoothly
through the scanner; the name derives from the helical
path traced out by the X-ray beam.
• It was the development of two technologies that made
helical CT practical: slip rings to transfer power and
data on and off the rotating gantry, and the switched
mode power supply powerful enough to supply the X-
ray tube, but small enough to be installed on the gantry.

MULTISLICE CT
• Multislice CT scanners are similar in concept to the helical or
spiral CT but there are more than one detector ring.
• It began with two rings in mid nineties, with a 2 solid state ring
model designed and built by Elscint (Haifa) called CT TWIN,
with one second rotation.
• Later, it was presented 4, 8, 16, 32, 40 and 64 detector rings, with
increasing rotation speeds.
• Current models (2007) have up to 3 rotations per second, and
isotropic resolution of 0.35mm voxels with z-axis scan speed of up
to 18 cm/s.
• This resolution exceeds that of high Resolution CT techniques
with single-slice scanners, yet it is practical to scan adjacent, or
overlapping, slices - however, image noise and radiation exposure
significantly limit the use of such resolutions.

• The major benefit of multi-slice CT is the increased
speed of volume coverage.
• This allows large volumes to be scanned at the
optimal time .
• The ability of multi-slice scanners to achieve
isotropic resolution even on routine studies means
that maximum image quality is not restricted to
images in the axial plane - and studies can be freely
viewed in any desired plane.

DUAL SOURCE CT
• Siemens introduced a CT model with dual X-ray tube and
dual array of 64 slice detectors, at the 2005 Radiological
Society of North America (RSNA) medical meeting.
• Dual sources increase the temporal resolution by
reducing the rotation angle required to acquire a
complete image, thus permitting cardiac studies
without the use of heart rate lowering medication,
as well as permitting imaging of the heart in systole.
• The use of two x-ray units makes possible the use of
dual energy imaging.

DIAGNOSTIC USE
• Since its introduction in the 1970s, CT has become an important tool in medical
imaging to supplement X-rays and medical ultrasonography.
• Althoughit is still quite expensive, it is the gold standard in the diagnosis of a
large number of different disease entities.
• It has more recently used for preventive medicine or screening for disease, for
example CT colonography for patients with a high risk of colon cancer.
• Although a number of institutions offer full-body scans for the general population,
this practice remains controversial due to its lack of proven benefit, cost, radiation
exposure.

ADVANTAGES
• First ,CT completely eliminates the superimposition
of images of structures outside the area of interest.
• Second, because of the inherent high-contrast resolution of
CT, differences between tissues that differ in physical
density by less than 1% can be distinguished.
• Third, data from a single CT imaging procedure
consisting of either multiple contiguous or one helical
scan can be viewed as images in the axial, coronal, or
sagittal planes, depending on the diagnostic task. This
is referred to as multiplanar reformatted imaging.

HAZARDS : ADVERSE REACTIONS TO
CONTRAST AGENTS
• Because CT scans rely on intravenously administered
contrast agents in order to provide superior image quality,
there a low but non-negligible level of risk associated with
contrast agents themselves.
• Certain patients may experience severe and potentially life-
threatening allergic reactions to contrast dye.
• The contrast agent may also induce kidney damage. The risk
of this is increased with patients who have preexisting renal
insufficiency, preexisting diabetes, or reduced intravascular
volume.

Process
CT scan illustration

• X-ray slice data is generated using an X-ray
source that rotates around the object.
• X-ray sensors are positioned on the opposite side of
the circle from the X-ray source.
• Many data scans are progressively taken as the
object is gradually passed through the gantry.
• They are combined together by the mathematical
procedure known as tomographic reconstruction.

• Contrast materials such as intravenous iodinated
contrast are used.
• This is useful to highlight structures such as
blood vessels that otherwise would be difficult
to delineate from their surroundings.
• Using contrast material can also help to obtain
functional information about tissues.

WINDOWING
• Windowing is the process of using the calculated Hounsfield units to make an
. image.
• The various radio density amplitudes are mapped to 256 shades of gray. These
shades of gray can be distributed over a wide range of HU values to get an
overview of structures.
• Alternatively, these shades of gray can be distributed over a narrow range of HU
values (called a "narrow window") centred over the average HU value of a
particular structure to be evaluated. In this way, variations in the internal makeup
of the structure can be discerned. This is a commonly used image processing
technique known as contrast compression.

• All the shades of gray for the image would be
distributed in this range of Hounsfield values.
• Any HU value below -15 would be pure black, and
any HU value above 155 HU would be pure white in
this example.
• Using this same logic, bone windows would use a
"wide window" (to evaluate everything from fat-
containing medullary bone that contains the
marrow, to the dense cortical bone) .

THE PRINCIPLE
• Because contemporary CT scanners offer isotropic,
or near isotropic resolution, display images does not
need to be restricted to the conventional axial images.
• Instead, it is possible for a software program to build a
volume by 'stacking'the individual slices one on top of
the other.
• The program may then display the volume in an
alternative manner.

MULTIPLANAR RECONSTRUCTION
• Multiplanar reconstruction (MPR) is the simplest method of
reconstruction.
• A volume is built by stacking the axial slices. The software then cuts
slices through the volume in a different plane (usually orthogonal).
• Optionally, a special projection method, such as maximum-intensity
projection (MIP) or minimum-intensity projection (mIP), can be used to
build the reconstructed slices.

3D RENDERING TECHNIQUES
Surface rendering
• A threshold value of radiodensity is chosen by the
operator (e.g.a level that corresponds to bone).
• A threshold level is set, using edge detection image
processing algorithms.
• From this, a 3-dimensional model can be constructed and
displayed on screen.
• Multiple models can be constructed from various different
thresholds, allowing different colors to represent each anatomical
component such as bone, muscle, and cartilage.

VOLUME RENDERING
• Surface rendering is limited in that it will
only display surfaces which meet a threshold
density, and will only display the surface that
is closest to the imaginary viewer.
• In volume rendering, transparency and colours
are used to allow a better representation of the
volume to be shown in a single image - e.g. the
bones of the pelvis could be displayed as semi-
transparent, so that even at an oblique angle,
one part of the image does not conceal another.

3D RENDERING SOFTWARE
• Some examples of CT 3D surface rendering
software include
Mimics, 3D doctor, Amira....etc
• Some examples of CT 3D
volume rendering software include doctor,
ScanDoc-3D....etc

Image segmentation
• Segmentation (image processing)
• Where different structures have similar
radiodensity, it can become impossible to
separate them simply by adjusting volume
rendering parameters. The solution is called
segmentation, a manual or automatic
procedure that can remove the unwanted
structures from the image.

CT IMAGING OF FACE
• Preferred modality for imaging of the face
• More sensitive for fracture detection –
Show significant soft tissue injury.
• Easier to perform, quicker than complete views of plain film
radiographs Presurgical planning for complex injuries
• Disadvantage of CT –
CT can miss subtle tooth fracture along the axial plane,
additional orthopanthogram may be helpful to
detect tooth fracture.

CT protocol
• Axial scanning from above the frontal sinus down to
below hard palate(face), and can be scanned further to
include the mandible, if there is a clinical suspicion for
fracture of mandible.
• For helical(spiral) scanner, axial images can be
reconstructed to coronal and saggital planes without the
need for direct coronal scanning- viewing in both bone
and soft tissue windows, in 3 planes(axial, coronal,
saggital)

Imaging of Facial Trauma
What Imaging to Do?

ROLE OF IMAGING
• Identify fractures, fragment displacement and rotation
stable for use in surgical repair.
• High accuracy for evaluation of both bony and soft
tissue injuries.
• It is cost saving when compared to multiple views of
plain film radiography.
• Radiation dose is far below the threshhold for cataract
formation.

When to Do Imaging of the Face
• When the patient is stabilized –
Clinically (Airway, Breathing, Circulation stable)
• Initial goal is to preserve life -
then later restore the form and function of the face
• Cervical spine clearance –
Radiographically for cervical spine clearance

• Head CT should be thoroughly evaluated in a patients
with multiple trauma.
• Search for critical, emergent finding: some facial inju
ries may compromise vision if not immediately recog
nized –
In stable patient, face CT can be performed with little
additional time when the patient is already in the sca
nner

Normal Anatomy
• Face –
Face (midface) is the region
from supraorbital rims to and
including maxillary alveolar
process.
• Mandible, including the
temporomandibular joints
(TMJ), considered
separate from the face .

3D CT ANTERIOR VIEW
Major structures are
labelled in the picture
Nasofrontal suture
Zygomatico-
frontal suture
Zygomaticotemporal
suture
SOF = Superior orbital
fissure
IOF = Inferior orbital f
issure
Orbital ‘rim’ is different
from the ‘wall’

3D CT LEFT LATERAL
VIEW
Nasofrontal suture
Zygomatico-
frontal suture
Zygomatico-
temporal suture

Posterior wall of
frontal sinus
fracture may co-
exist with brain
injury.
• Presence of
pneumocephalus
will signify
dural tear related
with the fracture .
• Inferior part of
frontal sinus
constitute the
medial orbital
wall.
Key structures
A = Frontal sinus, anterior wall B = Frontal sinus, posterior wall
*Note: The right frontal sinus is not pneumatized in this case.

Key structures
D = Orbit, medial wall
E = Orbit, lateral wall
F = Suture between
sphenoid and zygomatic
bones
= Nasomaxillary sutur
e
1 = Globe
2 = Ethmoid sinus
3 = Sphenoid sinus
4 = Nasal bone
5 = Maxilla, frontal proc
ess 6 = Orbit, lateral rim
7 = Sphenoid bone
8 = Optic foramen
Do not confuse the suture between nasal bone and frontal
process of maxilla for a fracture.
• Look for a piece of fracture in the optic foramen, it is the true
emergency of facial fracture.

Key structures
F = Groove for
infraorbital nerve
G = Maxillary sinus,
posterolateral wall
5 = Maxilla, frontal
process
9 = Maxillary sinus
10 = Zygomatic arch
11 = Pterygoid bone
12 = Nasolacrimal
duct
13 = Mandible,
condyle
Clear maxillary sinuses can almost rules out certain fractures such as ZMC, LeFort, blowout
fractures.

Key structures
H = Maxillary sinus,
anterior wall
I = Maxillary sinus,
medial wall
J = Medial pterygoid
plate
K = Lateral pterygoid
plate
9 = Maxillary sinus
14 = Mandible, ramus
Fracture of the pterygoid plates may represent LeFort fracture

Key structures
plate
plate
L = Maxilla, spine
15 = Maxilla bone/
hard palate
Lucency in midline of the maxilla is a normal finding seen occasionally

CORONAL REFORMATTED IMAGES
KEY STRUCTURES
L = Maxilla, spine
= Nasomaxillary suture
4 = Nasal bone
5 = Maxilla, frontal process
Do not confuse nasomaxillary suture for a fracture
• Remind yourself that CT can miss subtle tooth
fracture, although with the coronal and sagittal
reformation. Obtain orthopanthogram or dedicated tooth
film when in doubt

Key structures
D = Orbit, medial wall
M = Nasal septum
5 = Maxilla, frontal process
15 = Maxilla bone/ hard palate
16 = Frontal sinus
17 = Mandible, body

Key structures
M = Nasal septum
N = Ethmoid bone, perp
endicular plate
O = Orbit, roof
P = Orbit, floor
Q = Maxillary sinus, pos
terolateral wall = Zygo
maticofrontal suture
1 = Globe
2 = Ethmoid sinus
6 = Orbit, lateral rim
9 = Maxillary sinus

Key structures
pslate
plate
N = Ethmoid,
perpendicular plate
3 = Sphenoid sinus
10 = Zygomatic arch
18 = mandible, angle

Key structures
R = Temporomandibular
joint (TMJ)
13 = Mandible, condyle
19 = Mandible, coronoid
process
20 = Mastoid air cells
If patient opens his/her mouth
during the scan, there is a
normal gliding of the
mandibular condyle relative to
the glenoid fossa.
SAGGITAL REFORMATION

Key structures
P = Orbit, floor
7 = Pterygoid bone
9 = Maxillary sinus
15 = Maxilla bone /har
d palate
• Orbital blowout fracture
is best seen in sagittal and
coronal images
• Facial CT is not complete
d without image
reconstruction

Key structures
3 = Sphenoid sinus
4 = Nasal bone
15= Maxilla bone/
hard palate

BIOMECHANICS
LeFort described areas of relative
strength within the facial skeleton
1.Alveolar process of maxilla
2.Frontal process of maxilla
3.Body of zygoma or malar
eminence
Line of fracture tends to avoid
these areas.

Checklist for Facial Radiograph/CT
• Facial structures are quite symmetrical
• Do not stop searching when see one abnormality
• If suspect for more than simple nasal fracture, do CT
• Fracture involves the optic foramen which can cause permane
nt visual loss if not treated promptly
• Fracture of the posterior wall of frontal sinus requires
neurosurgical
evaluation and may require antibiotics prophylaxis
• Fracture/dislocation of the TMJ usually missed on initial
survey. It can cause significant disability if left untreated
• Look for significant soft tissue injuries -
Globe rupture, hemorrhage

NASAL FRACTURES
• Most common fracture of the facial bone
• Etiology: motor vehicle collisions (MVC) most
common, followed by assaults
• Relevant anatomy:
Nasal pyramid consists of Nasal bones
Inferior part of nasal bones is thinner than superior,
more prone to fracture (fracture)
Frontal processes of maxilla, Nasal septum (superior =
perpendicular plate of ethmoid, inferior = vomer,
anterior = quadrangular cartilage), Lateral cartilages
(upper and lower lateral cartilages

• Diagnosis:
Made based on physical examination findings Visible
bony deformity in displaced fracture, Laceration, ecchymosis,
hematoma, mucosal tear and epistaxis in the inner surface of the
nasal cavity strongly suggest fracture.
• Presence of epistaxis and septal hematoma requires prompt
diagnosis and treatment
• Epistaxis can be life threatening
• Septal hematoma may lead to cartilage necrosis and resultant
saddle nose deformity
• Telecanthus is an indication of more severe injury, further
workup including CT scan is required

• CT better depicts fracture,
especially frontal process of maxilla.
• Depressed fracture of frontal process of maxilla can lead to
facial deformity if left untreated
• Presence of telecanthus should prompt CT workup

Nasal Fractures, frontal blow
39-yo-man was punched
from the front
Comminuted bilateral nasal
bone fractures (red arrows)
with displaced fragments.
N = nasal bone
M = Frontal process of
maxilla
Black arrow = Intact
nasomaxillary suture

NASAL SEPTUM FRACTURES
33-yrs-man was punched by a
righthanded person
S = Bony nasal septum
E = Ethmoid sinus
Sp = Sphenoid sinus.
Fractures of the left frontal process of maxilla (red arrow) and the right nasal bone (green arrow)
are noted. A long arrow indicates a fracture of the bony nasal septum. The fractures are displaced
to the right, indicating the force of impact from the left. The right-handed person hit the left side
of the nose of the victim

NASAL SEPTUM FRACTURES
67-yo-man involved in a
motor vehicle collision
S = Bony nasal septum
E = Ethmoid sinus
Blue arrows = Frontal
process of maxilla.
Deformity of the nose pointing toward the left. There is angulation of the
cartilagenous portion of the nasal septum (red arrows) and blood in the nasal cavity.
The patient also had orbital floor fractures with orbital emphysema (star).

NASO-ORBITAL-ETHMOIDAL (NOE)
FRACTURES
• Etiology: Forceful frontal blow to the central aspect
of midface.
• Most common from motor vehicle collisions
(MVC), followed by assaults
• NOE fractures involve the central upper face,
disrupting the medial orbit, nose and ethmoid
sinuses.
• NOE fractures are distinguished from simple nasal
fractures by posterior disruption of medial canthal
region, ethmoids and medial orbital walls .

• NOE complex consists of nasal, frontal, maxillary,
ethmoid, lacrimal and sphenoid bones.
• Superior to NOE complex is anterior cranial fossa
• Lateral to NOE complex is globe
• Deep to NOE complex is optic canal and sphenoid bone
• Centre of NOE complex is interorbital space, consisting of
ethmoid sinuses, lacrimal drainage system, nasofrontal
ducts
• Therefore, NOE fractures can be related to many
significant surrounding structures .

Relevant anatomy of Medial canthal tendon:
• A crucial soft tissue component of NOE complex.
• Medial portion of orbicularis oculi, inserting to the
medial orbital wall.
• Acts as a suspensory sling for the globe and ensure
close apposition of the eyelid.
• In NOE fractures, medial canthal tendon pulls the
fragment laterally, or (rarely) torn, causing
telecanthus.

• Helpful clinical signs to detect traumatic telecanthus:
• Intercanthal distance > interpalpebral distance of the
eyes.
• Intercanthal distance more than one-half of
interpupillary distance.
• Clinically, the most obvious deformity is loss of
nasal projection in profile and apparent telecanthus.

• Pertinent radiologic information:
• Degree of comminution of medial orbital wall,
especially in the lacrimal fossa where medial
canthus attaches.
• Involvement of nasofrontal ducts require surgical
obliteration of frontal sinus to prevent frontal
mucoceles.
• Extension:
• Posterior extension to the optic canal.
• Superior extension to the frontal sinus, intracranial structures.
.

Complications:
• Persistent telecanthus.
• Injury to lacrimal system.
• Nasofrontal duct impingement.

NOE Fractures
21-yo-man was assaulted
E = Ethmoid M = Maxillary
sinus Sp = Sphenoid sinus
Orbital emphysema
Frontal blow to the nasion
results in a comminuted
fracture involving the medial
walls of both orbits (green
circle), nasal bones (green
arrow) and frontal processes of
maxillae (red arrows) as
shown in image A.
Blue arrows indicate the
attachment sites for medial
canthal tendons.
Posterior displacement
(depression) of the nasion is
noted in image B.

3D images better depict degree of displacement and depression of the NOE
fractures. The fractures also extend to frontal sinuses (F). Comminuted fractures
of bilateral nasal bones (N) and frontal processes of maxillae (M) are shown.
Small images on right lower corners represent normal anatomy in the same
projections. Radiologic description should comment on degree of comminution
of medial orbital wall especially in the region of lacrimal fossa, where the medial
canthus attaches and nasofrontal ducts are located.

FRONTAL SINUS FRACTURES
• Etiology: motor vehicle accidents (most common),
followed by high-impact sport related injuries
• Clinical : Gross depression or laceration over
supraorbital ridge, glabella or lower forehead (most
common finding on clinical exam)
• Ophthalmologic evaluation may be necessary because
up to half of patients have orbital trauma
• Classification of fractures :
• Location: anterior table, posterior table, or both.
• Appearance: linear, comminuted, depressed or
nondisplaced .
• Isolated anterior table fracture is most common

• Frontal sinus first appear 6-8yrs, fully pneumatized in
adolescence.
• It can be asymmetric and partially pneumatized in up to
20% of population.
• Frontal sinuses drain via either nasofrontal duct
located posteriomedially in the sinus or in conjunction with
anterior ethmoid air cells. The nasofrontal duct, if present
and fractured, can be obstructed - leading to chronic
drainage complication.
• Frontal sinus is closed to dura, frontal lobe, crista galli
and cribiform plate .

• Indication for surgery:
• Fracture potentially injures nasofrontal duct (fx involves
base of frontal sinus, medial to supraorbital notch)
• Depressed anterior table - cosmetic deformity
• Posterior table fx with gross CSF leak, more than one table
width displacement .
• Complication:
• Early complication: frontal sinusitis (retained FB in sinus)
leading to meningitis, osteomyelitis, orbital abscess or brain
abscess.
• Late complication: mucocele, mucopyocele, delayed CSF
leak

Frontal Sinus Fractures
Two examples. Young
patients who were
assaulted.
Above: Isolated anterior
table fractures (red
arrows) with hemosinus.
Intact posterior table
(blue arrow). This type of
depressed fracture causes
cosmetic deformity
Below: Both anterior and
posterior table fractures
(red and green arrows),
which are nondepressed.
Pneumocephalus (white
arrow)

Frontal Sinus Fractures
Scout CT: Asymmetrical haziness of the left frontal sinus (normal frontal sinus on
AP skull radiograph should have same density to the orbit) indicates hemosinus (red
arrow).
Axial CT: Fracture of the posterior wall of the left frontal sinus (green arrows) is
confirmed. There is displacement of the fracture fragments into the sinus. Small
pneumocephalus is noted deep to the fracture. Isolated posterior wall fracture is rare.

ORBITAL FRACTURES
• Plain radiography has a false negative rate of 7-30%.
• CT in axial, and coronal planes are essential to determine
presence of fractures and status of intraocular muscles.
• Axial: medial, lateral wall fracture, entrapment of medial
rectus muscle .
• Coronal: floor, roof fracture, entrapment of inferior rectus
muscle, fracture involving nasolacrimal duct, fx of optic
canal, retro-orbital hematoma .
• Two main types:
• Blow-out fractures
• Blow-in fractures

• Blowout fractures:
• Bone is displaced away from the orbit.
• May involve the roof, floor, and medial or lateral walls of the orbit.
• Most common = floor.
• If orbital rim is intact = ‘pure’ blow-out fracture (classic fx).
• Up to 30% have ocular injury.
• Two proposed mechanisms of injury:
• Hydraulic mechanism: pressure on eyeball increases intraorbital
pressure, then the orbit ruptures at its weakest point (thin floor).
• Buckling mechanism: blow to orbital rim results in fx of orbital
wall.
• Clinical: Enophthalmos, diplopia and hypoesthesia (infraorbital
nerve distribution) can be obscured due to swelling.

• Blowout fractures:
• Image interpretation special attention to
• Appearance of inferior rectus muscle on coronal images
• Normal = oval shape
• Abnormal = round shape
• Location of inferior rectus muscle
• Abnormal = located below the expected level of orbital floor
• Abnormal inferior rectus can be Entrapped: muscle lies
completely beneath or within the defect and appears round on
coronal images
• Hooked: portion of muscle lies within the defect
• Entrapment of inferior rectus in children can be easily
missed, since flexible bone springs back into place like a trap
door, looking normal at CT except for entrapped muscle
beneath it
• This requires urgent Rx within 24-72 hours to minimize
motility problem .

ORBITAL BLOW OUT FRACTURES
Middle age patient involved in
motor vehicle accident
Coronal images (in bone and
soft tissue windows) shows the
defect (red arrow) in the floor
of the right orbit with a small
hematoma in the right
maxillary sinus (green arrow).
Light blue arrows point to the
inferior rectus muscle, where
its inferior portion (blue arrow)
is hooked to the defect.
O = Optic nerve , Facial soft
tissue oedema
Clinical ophthalmologic exam
is required to confirm or rule
out evidence of intraocular
muscle entrapment.

ORBITAL BLOW OUT FRACTURES
81-year-old woman fell from stairs Intraorbital fat herniation
(green arrow) through the defect in the floor of the left orbit. The
inferior rectus (blue arrow) is far from the site of fracture. 3D
image shows intact orbital rim (red arrows) indicative of ‘pure’
blow-out fracture. O = Optic nerve, H = Hemosinus

• Blow-in fractures:
• Bone is displaced into the orbit, intraorbital volume
is decreased.
• May involve the roof, floor, and medial or lateral
walls of the orbit.
• Clinical: Exophthalmos (due to decreased orbital
volume)
• Decreased visual acuity (eyeball trauma, optic
neuropathy, fracture of optic canal).

ORBITAL BLOW IN FRACTURES
80-year-old man fell onto his face. Fractures of the floor of the left orbit (red
arrow) displace superiorly into the orbit. The medial rectus muscle (blue
arrows) is pushed upward by the fracture fragment. Intraorbital volume is
further decreased by retroorbital hematoma (blue star). H = Hemosinus

• Orbital floor fractures:
• Most common portion of orbit to sustain a fracture
• Usually associated with other complex midface fractures
(ZMC, LeFort II and LeFort III fractures).
• Can be linear, comminuted, or segmental.
• Herniation of intraorbital contents.
• Best seen in coronal projection.
• What determines chance of herniation, entrapment?
• Size of fragment, degree of depression .
• Inferior rectus muscle can be free, hooked, or entrapped
Indications for surgery .
• Involvement > 50% of the floor, combined floor and medial
wall fx with soft tissue herniation, significant enophthalmos (>
2mm), significant diplopia .

• Medial wall fractures:
• Usually associated with other complex midface fractures.
• Risk of medial rectus herniation (either hooked or entrapped)
- relatively rare.
• Orbital roof fractures:
• Risk of brain herniation into the orbit (better seen with coronal
reformatted CT or MRI)
• Orbital apex fractures:
• Emergent surgical cases if there is radiologic and clinical
evidence of optic nerve impingement .
• May be associated with blindness.
• May be associated with carotid artery injury (cavernous
portion)

• Soft tissue injuries of the orbit:
• Eyeball rupture:
• Usually there is extrusion of vitreous (normal intraocular
pressure is higher than intraorbital pressure) - leading to CT
signs ‘flat tire’ sign and ‘deepening’ of anterior chamber.
• Lens injury: subluxation, dislocation, traumatic cataract.
• Zonular fibers hold lens in place to ciliary muscle. If torn
(partial or complete), subluxation or dislocation occurs .
• Traumatic cataract (acute lens edema): affected lens has
density 30HU less than normal side.
• Intraorbital hemorrhage
• Intraorbital foreign body

GLOBE RUPTURE AND VITREOUS HEMORRHAGE
21-year-old man was assaulted. Right globe rupture is evident by flattening
of the posterior wall of the globe “flat tire sign” (red arrow) and narrowing
of the space between cornea and lens “deepening of anterior chamber” (red
line). = Vitreous hemorrhage

HEMORRHAGE: PRESEPTAL, VITREOUS AND CHOROIDAL
Preseptal hemorrhage = bleeding in the space anterior to the globe (green
arrows, line) Vitreous hemorrhage = bleeding in the posterior chamber of the
globe (red star), usually making ‘obtuse’ angle with the surrounding vitreous
Choroidal hemorrhage = bleeding in the choroid (white stars) along the wall of
the globe Blue arrows represent subcutaneous edema/hemorrhage.

TRAUMATIC LENS DISLOCATION
60-year-old man was found down. Traumatic left lens dislocation (red
arrow) is noted. Dislocation occurs due to tear of zonular fibers normally
surrounding the lens. Blue arrows point to normal lens with presumed
locations of zonular fiber attachment. The patient also has diffuse
subarachnoid hemorrhage (red stars) and multiple facial fractures. Traumatic
Lens Dislocation

ZYGOMATIC FRACTURES
Two types of zygomatic fractures:
• Zygomatic complex fracture
• Isolated zygomatic arch fracture
• Malar eminence = surface anatomy of
the body of zygoma.
• Zygomatic fractures can cause limitation
of mandibular motion, especially when
fractures are depressed.
• Masseter muscle arises from zygomatic
arch.
• Coronoid process is located underneath
the zygomatic arch .

• Zygomatic complex fractures:
• ZMC fracture, trimalar fracture, malar eminence fracture.
• Tripod fracture is a misnomer (zygoma actually has 2
attachments to cranium and 2 to maxilla)
• Principal lines involve 3 components:
• Orbital process of zygoma.
• Inferior rim of orbit.
• Zygomatic arch.
• Main fragment is zygoma, which is separated from its three
areas of attachment.

• Zygomatic complex fractures:
• Fractures almost invariably traverse the infraorbital nerve
foramen (located in the orbital floor), causing impaired
sensation of the cheek and a portion of the upper lip. However
in majority of cases, the nerve is usually intact .
• Image interpretation should pay additional attention to:
• Alignment of zygoma (depressed, rotated).
• Lateral orbital wall alignment (posterior relationship of
zygoma and sphenoid bones).
• Angulation of the wall results in increased orbital volume and
enophthalmos.

• Isolated zygomatic arch fracture:
• Etiology: direct blow by small object
• Commonly consists of 3 fracture lines:
• One at each end and the third in the center with
depression of fracture fragment
• Limited motion of mandible may occur if the fracture
impinges on coronoid process or simply because the
masseter muscle arises from zygomatic arch

ZYGOMATIC COMPLEX FRACTURES
60-year-old man fell onto the left cheek. Axial and coronal reformatted CT images
show typical left ZMC fractures: anterior/ posterior walls of maxillary sinus including
rim (red arrows), zygomatic arch (green arrow), and orbital process of zygoma (blue
arrow). Left orbital floor ‘blow-out’fracture with intraorbital fat herniation is seen in
coronal image. Orbital floor fracture is commonly associated with ZMC fractures.
H = Hemosinus, star= Soft tissue emphysema due to communication with fractured
sinus

ZYGOMATIC COMPLEX FRACTURES
Same patient as in
the previous page
3D image shows all
components of left
ZMC fractures
including the inferior
orbital rim (red
arrows),
zygomatico-frontal
separation (blue
arrow), zygomatic
arch (green arrow).

ISOLATED ZYGOMATIC ARCH FRACTURES
23-year-old man was punched by a left-handed. Classic zygomatic
arch fractures occur in three sites along the arch. The middle fracture
causes fracture fragment depression.

MAXILLARY FRACTURES
• Types of maxillary fractures:
• Maxillary sagittal fracture (maxillary sinus fracture).
• Palate fracture
• Alveolar process fracture
• LeFort fractures
• LeFort I fracture
• LeFort II fracture
• LeFort III fracture
• Combination (bilateral)

MAXILLARY SAGGITAL FRACTURE
• AKA maxillary sinus fracture:
• Fracture of a maxilla in sagittal plane, involving
anterior-lateral wall of a maxillary sinus (LeFort
fractures represent bilateral maxillary fractures).
• Due to direct blow to either right or left midface.
• Plain film shows opacified maxillary sinus, however
it is usually inadequate for diagnosis

MAXILLARY SAGITTAL SUTURE
68-year-old man was
found down.
There is a sagittal
plane fracture of the
left maxillary sinus
(red arrow) with
hemosinus (H)

ISOLATED ALVEOLAR PROCESS
FRACTURE
• Fracture of any portion of the alveolar process
• Clinically evident by malalignment and displacement
of teeth contained within fractured segment
• Even on CT, fracture may be subtle and easily
overlooked
• Further imaging may be needed when the diagnosis
is made
• X-ray of the teeth or a panoramic view (look for
dental injuries) Chest radiograph (look for
aspirated teeth)

MAXILLARY ALVEOLAR PROCESS FRACTURES
Middle age women fell onto her mouth. Red arrows show the
comminuted fractures of the maxillary alveolar process on the
right side. These fractures are considered ‘open’ as they are
connected to the oral cavity.

LEFORT FRACTURES
• Among the most severe fractures seen in face and associated with high-
energy trauma.
• Named after René LeFort, a French physician, who studied facial fractures
in cadavers. Result was published in 1901.
• Key facts:
• In each type, there is a partial or complete separation of maxilla
from the remainder of the facial skeleton.
• All LeFort fractures must extend through posterior face, transects
the pterygoid processes.
• Any combination of LeFort I, II, and III patterns can occur

LEFORT 1 FRACTURE
• Definition: Transmaxillary fracture
• Transverse (horizontal) fracture of inferior maxillae,
involving maxillary sinuses (all except superior walls), lateral
margin of nasal fossa, nasal septum and pterygoid plates
• Clinical: Free floating and movable hard palate with
maxillary teeth.
• Imaging findings:
• Opacified bilateral maxillary sinuses
• Transverse fracture through the inferior maxillae above hard
palate
• Best shown and confirmed by coronal and sagittal
reformatted CT images

LEFORT I FRACTURE
48-year-old man was kicked by a horse. LeFort I fracture line
along bilateral maxillary sinuses (red arrows). Pterygoid plate
fractures are not shown H = Hemosinus, Blue arrow = Mandibular
fracture

LEFORT II FRACTURES
• Pyramid-shaped maxillary fracture, involving maxillary
sinuses (anterior-lateral walls), inferior orbital rim,
orbital floor and nasofrontal suture.
• Clinical: free floating, movable midface including
maxillary teeth, hard palate and nose.
• Imaging findings:
Opacified bilateral maxillary sinuses and orbital
emphysema
Fractures of anterior/lateral walls of maxillary
sinuses, inferior orbital rims/floors and disruption
of nasofrontal suture
Best seen and confirmed by coronal reformatted
CT images

LEFORT II FRACTURE
Middle age man in motor vehicle accident.
Fracture lines are demonstrated in red arrows.
Fracture of pterygoid plates are present in all
type of LeFort fractures. H = Hemosinus

LEFORT III FRACTURE
• AKA craniofacial disjunction
• This fracture separates calvaria (skull) from the facial bones. Most
severe of all LeFort fractures
• Definition: separation of facial bones from the skull
• Zygomas separated from sphenoid at zygomatico-sphenoid sutures
• Nasal bones and medial orbital walls separated from frontal bone at
nasofrontal sutures
• Best seen in coronal images
• Clinical: movement of face relative to the skull
• Imaging findings: Plain film will underestimate degree of injury
due to severe soft tissue swelling obscuring the bony details. CT is
recommended

COMBINED LEFORT II AND
III FRACTURES
32-year-old man,
unrestrained driver in a
motor vehicle accident.
Blue arrows define LeFort
II fracture. Red arrows
define the LeFort III
fracture.

MANDIBULAR FRACTURES
• Motor vehicle collisions and assaults together account for
more than 80% of mandible fractures
• Incidence
• Ratio of mandibular to facial fractures = 2:1
• Co-existence of mandibular and facial fractures = 6-10%
• Rare in children, If occurs, condyle is the most common
location
• Condyle is the growth center of mandible.
• Trauma to this area can retard growth and cause facial
asymmetry
• Clinical : Laceration under chin (common), Pain,
malocclusion, deviation of mandible on opening mouth

• Mandible is divided into region for purpose of describing
location of fractures
• Symphysis (= within the boundaries of central incisors)
• Parasymphysis (within the boundaries of vertical lines distal
to canine teeth)
• Body (include the region of third molar)
• Angle (distal to the third molar)
• Ramus ,Condylar process (has separate classification system)
Coronoid process ,
• Alveolar process (region normally contains teeth)

RELEVANT ANATOMY
• Mandible is a ring or arc bone which is usually difficult to
break in one location.
• Approximately half of mandible fractures occur in multiple
locations.
• Search for a second fracture after initial fracture is identified!
(usually at contralateral side)

IMAGING RECOMMENDATION
• Plain film mandible series (PA, lateral, Towne’s and bilateral
obliques) show nearly all fractures BUT may be difficult to
obtain in multi-trauma patients.
• Panoramic radiography (orthopantography), Need patient in
upright position,Better to look for subtle tooth fracture .
• CT -Show all mandibular fractures AND other facial fractures
(co-existence 6-10%), as well as position and alignment of
fragments
• Display associated soft tissue injuries
• Easy to perform in multi-trauma patient

Bilateral Mandibular Fractures/Dislocations
CT shows left symphyseal/ parasymphyseal fracture
extending to the tooth (green arrows), and bilateral
mandibular condyle fractures (red arrows). The findings
represent ‘Flail mandible’. Limitation of plain films in
previous page is likely due to 1. Inadequate coverage (PA
projection does not include the inferior part of mandible) 2.
Suboptimal technique (Oblique views are not true oblique)
If plain film is to be
used, make sure to have
all projections, adequate
coverage and optimal
technique. If in doubt,
CT is the solution

MANDIBULAR FRACTURES
43-year-old man, fell from height, presented with
malocclusion Orthopantogram demonstrates a fracture of the
right ramus of mandible (red arrows). Subtle ‘second’ site of
fracture is at the left body (green arrows) which is confirmed
in CT scan
Search for second
site of fracture is
warranted when one
sees mandibular
fracture

Same patient as in previous page. CT confirms the fractures of the right angle
of mandible (red arrows) and left body (green arrows). Axial image shows
extension of fracture into the root of the left mandibular tooth, indicating an
open fracture

Mandibular Fractures
21-year-old man was punched at his left face by the right-handed person. Orthopantogram
shows a nondisplaced fracture of the left angle of mandible (red arrows), extending to the
root of unerupted ADA #18.
Where is the second site of fracture?

Same patient as previous page. CT Orthopantogram (post-processing
images from axial CT) shows an additional nondisplaced fracture of the left
parasymphysis (blue arrows).
Plain orthopantogram should not be used as a single imaging to look for
mandibular fractures. It is useful for tooth fracture, not for mandible.

MANDIBULAR FRACTURES WITH TMJ DISLOCATION
19-year-old woman in a rollover motor vehicle accident. Axial CT image (A)
shows ‘empty glenoid sign’ (red line) indicating right temporomandibular
joint dislocation. Image B in a more inferior slice reveals a fracture of the
right mandibular condyle (red arrow) with anterior medial displacement of
the condyle due to the pull of lateral pterygoid muscle. The left glenoid fossa
is normal.
C = Left condyle of mandible

MANDIBULAR
FRACTURES WITH TMJ
DISLOCATION
Same patient as in
previous page.
3D image on right
lateral view makes
it easier to
understand the
fracture site,
dislocation and
orientation of the
fragment.
Red arrows =
fracture of the base
of right condyle of
mandible

MANDIBULAR FRACTURES WITH TOOTH FRACTURE
Young man in a motor vehicle accident. Tooth fracture of ADA #29 is apparent
(blue arrow) in this orthopantogram. However, fracture of the right body of
mandible is very subtle (red arrow) and may be detected only retrospectively.
This confirms that orthopantogram is not an appropriate imaging technique to
rule out or characterize mandible fractures.

Same patient as in previous page. In this case, CT demonstrates comminuted fracture of
the right body of mandible (red arrow) and tooth fracture (blue arrow).

Imaging Approach - CT
• Clear sinus sign (= all sinuses and mastoid are clear of fluid),
there are three possible facial fractures: Nasal bone fractures,
Isolated zygomatic arch fractures, Mandible fractures
• Bloody sinuses - Pterygoid plate fracture present - probable
LeFort fracture , With fracture of lateral margin of nasal fossa
= LeFort I , With fracture of inferior orbital rim = LeFort II
With fracture of zygomatic arch = LeFort III , Maxillary wall
fractures, Orbital floors, NOE region fractures , ZMC
fractures.

Axial (a,b) and coronal (c,d) CT scans bone and soft tissue algorithm revealed a
multilocular expansile lytic lesion involving the left hemimandible and symphysis
menti till right premolar region. There is disruption of the inner and outer cortices
with invasion of muscles of the floor of the month.

Contraindications for the use of iodinated contrast media:
Allergy to iodine
Toxic goitre of the thyroid
Planned radioiodine treatment of thyroid cancer.
Contraindications against the use of ion-based contrast media in patients:
Children below 2 years of age
Pregnant women
Persons over 60 years of age
Persons with complications after the previous administration of a contrast
medium
Persons with acute and chronic circulatory and respiratory failure
Persons with hepatic and renal failure (also dialyzed patients)
Persons with asthma and pulmonary oedemas
Persons with allergies
Persons with insulin-dependent diabetes
Persons with hypertension
Persons with convulsions of cerebral aetiology
Persons with glaucoma
CONTRA INDICATIONS

The lamina papyracea (or orbital lamina) is a smooth, oblong bone plate which forms
the lateral surface of the labyrinth of the ethmoid bone in the skull. The plate covers
in the middle and posterior ethmoidal cells and forms a large part of the medial wall
of the orbit.
It articulates above with the orbital plate of the frontal bone, below with
the maxilla and the orbital process of palatine bone, in front with the lacrimal, and
behind with the sphenoid.
Its name lamina papyracea is an appropriate description, as this part of the ethmoid
bone is paper-thin and fractures easily. A fracture here could cause entrapment of
the medial rectus muscle.

CONE BEAM COMPUTED TOMOGRAPHY
(CBCT)

INTRODUCTION
• Most significant technology advancement in
maxillofacial imaging
• The introduction of cbct specifically dedicated to
imaging the maxillofacial region heralds a true
paradigm shift from 2d to 3d approach to data
acquisition and image reconstruction.
• It expanded the role of imaging from diagnosis to
image guidance of operative and surgical procedures
by way of third party applications software.

PRINCIPLES
• CBCT imaging is performed using a rotating
platform carrying
• an x-ray source and
• detector

• A divergent cone shaped or pyramidal source of
radiation is directed through region of interest (ROI)
• X-ray source and detector rotate around a rotation
center, fixed within center of the ROI

• During rotation, multiple sequential planer projection
images are obtained while the xray source and
detector move through an arc of 180 to 360 degree
• • Single projection image form raw primary data,
which is individually known as - basis, frame or raw
image
• • Ususally several hundred 2-D basic images from
which the image volume is calculated.
• • Complete series of images is called PROJECTION
DATA

COMPONENTS OF CBCT
• Image production
• Visualization
• Interpretation

COMPONENTS OF IMAGE
PRODUCTION
• X-ray generation
• X-ray detection
• Image reconstruction

X-RAY GENERATION
• Patient Stabilization.
• Sitting, Standing, Supine.
• With all system, immobilization of the patient’s head is more
important than position because any movement degrades the
final image
• • Immobilization of head by 1) Chin cup 2)bite fork 3)other
head –restraint mechanism

X-ray Generator
• When pulsed- exposure time is up to 50% less than scanning
time (this technique reduces patients radiation dose)
• • ALARA (As Low As Reasonable Achievable) principle of
dose optimization states that CBCT exposure factor should be
adjusted on the basis of patient’s size. X-ray generation
continuous or pulsed
X-ray generation

SCAN VOLUME/FIELD OF VIEW(FOV)
• Detector size
• Shape
• Beam projection geometry
• Ability to collimate the beam
• It is desirable to limit the field size to the smallest
volume that images the ROI.
• This procedure reduces unnecessary exposure to the
patient and produces the best image by minimum
scattered radiation, which degrade image quality

CLINICAL CONSIDERATION
1.Patient selection criteria
• It provides a radiation dose to the patient higher than
radiation dose of other dental radiograph.
• When periapical or paranomic cannot provide
the necessary information.
• Used as adjunctive diagnostic tool

2. Patient preparation Appropriate
personal radiation barrier protection
• Leaded apron - for pregnant patients and children
• Lead thyroid collar- to reduce thyroid exposure.
• Before scan, remove all the Metallic object,
Eyeglass,Jewelry,Metallic partial denture

• Patient motion can be minimized by head
stabilization.
• Chin cups to posterior or lateral head support
• Patient should be directed to remain still as possible
before exposure, to breathe slowly through nose, and
to close the eyes.

3. Imaging protocol
• Develop to produce image of optimal quality
with the least amount of radiation exposure to
the patient
• Exposure setting
• Spatial resolution

Pretreatment
Clinical Evaluation
Clinical
Assessment
General
Health
Chief
Complain
Facial
Profile
Periodontal
Tissues
Soft
Tissues
Residual
Alveolar
Ridge

1. Examine patient’s current and status
medical history to assess risk profile

2. Periodontal/tissue biotype
- Highly scalloped,
thin, nonkeratinzied and flabby
mucosa  more susceptible to
gingival recession and
mechanical trauma  soft
tissue grafting indicated
- Thick, keratinized and non-mobile
mucosa  Less susceptible to gingival
recession following implant treatment
- Esthetics: thick mucosa is able to mask
the implants’ color and their
submucosal metallic components,
reducing the risk of a nonesthetic
result.
Thin Gingival Tissue Thick Gingival Tissue

3) Lip line
• The lip line is associated with the amount of tooth
and supporting tissues visible when patient chews,
speaks, or smiles.
• High lip line: patient’s entire maxillary teeth and part
of his/her alveolar process is revealed.
• Presents highest esthetic risk in implant treatment
• Provide a diagnostic set up or a temporary prosthesis
for the patient to try on before implant treatment to
assess appearance regarding the lip line.
• Provisional prosthesis can also serve as a model for a
surgical guide or stent to aid placing implants

4) Occlusal status and functional exam
1. Parafunctional habits such as bruxism and clenching
must first be diagnosed and treated before implant
treatment to ensure occlusal stability
2. Parafunctional habits cause excessive loading on
implants causing technical complications such as
screw or framework fractures

5) Evaluate edentulous ridge
1. Visually assess the contour, height and width of the edentulous
ridge
2. Fibrous overlying tissue can be deceiving
3. Palpate to detect any concavities or depressions. This step is
essential to detemine if patient needs bone augmentation
4. Nevertheless, edentulous ridge must be radiographically
examined
5. Observe crown to bone relationship (distance between the ideal
position of the clinical crowns and the underlying bone)
6. measure the distance between the dentulous ridge and the opposing
dentition to ensure there’s enough space for the restoration
7. length of endentulous area can be measured to determine the
approximate number of implants needed only verified through
radiographs

Labially this ridge reveals
aslight loss in center, and
the presence of healthy
keratinised tissue
Occlusally ridge appears
wide enough to accomadate
implants
Verified throgh radiograph

Preoperative Radiographic Assessment
• a. Characteristics of Ideal Imaging Techniques in Implants:
1. Ability to visualize the site of implant site in the mesiodistal,
faciolingual, and superoinferior dimensions
2. Ability to determine axial orientation of implants
3. Ability to allow reliable, accurate measurements
4. Capacity to evaluate trabecular bone density and cortical
thickness
5. Capacity to correlate the imaged site with the clinical site
6. Reasonable access and cost to the patient
7. Minimal radiation risk

• b. Preoperative radiographs should reveal: (15)
1. Position and size of relevant normal anatomic structures, including the:
a. Inferior alveolar canals
b. Mental foramina
c. Incisive or nasopalatine foramen and canal
d. Nasal floor
2. Shape and size of the antra, including the position of the antral floorand its relation to
adjacent teeth
3. Presence of any underlying disease that could compromise the outcome of treatment
e.g. osteoscleorosis
4. Presence of any buried teeth or retainedroots
5. Quantity of alveolar crest/basal bone, allowing direct measuremtns ofthe height, width
and shape
6. Quality (density) of bone, noting:
a. Amount of cortical bone present
b. Density of the cancellous bone
c. the trabecular spaces size

CBCT Scans
The Standard of Care in
implants?

• Advantages of CBCT in implant dentistry:
1. Evaluates all possible sites and anotmical structures:
2. No superimposition
3. Uniform magnification
4. Measurements accurate widthing about 1 mm
5. Simulates implant placement with implant planning software
6. CBCT dose of radiation exposure is less than that produced by
CT scanning
7. Can limit radiation exposure according to Field of View chosen
(FOV): small, medium, or large
8. provides precise information about pathology
9. Less expensive than CT scanning
10.allows for the 3-D evaluation of an arch

• Limitations of CBCT in implants:
1. Moderate cost and radiation risk as compared
to other imaging techniques
2. Some metallic image artifacts
3. Special training for interpretation
4. Relative bone density measurements (HU) not
calibrated

PREOPERATIVE DIAGNOSTIC
PLANNING
• To decide the precise healing scope of a prosthetic
implant therapy to re-establish chewing function,
it’s imperative to assess Bone availability and the
existing anatomical landmarks.
• This is easier when using 3D diagnostics than
using illustration with traditional images

The most frequently reported
indication for the use of CBCT in
implant planning area are to measure
the alveolar ridge and map the bone
morphology of possible implant sites
for osseointegration of the implant.
A) BoneAvailability
1.Quantitative Evaluation of Bone Availability
Bone compactness is an significant factor for implant placement to expect the
ability to stabilize the implant when minimal bone height is otherwise available.
Precise estimation of the alveolar bone height and width are mandatory:
1. For selecting the suitable implant size
2. Establish the degree of angulation of the edentulous alveolar ridge.
0

Measured from the crest
of the alveolar ridge to
the opposing border of
the bone or an anatomical
structure.
According to the bone
height, implant length is
determined
It is the bucco-lingual
width of the alveolar
bone. Implant
diameter is selected
based on this
parameter.
Bone Height: Bone width

Width of the maxillary alveolar ridge
measured at a specific point prior to
implant placement
Height of the maxillary alveolar ridge
measured at a specific point at a specific
point prior to implant placement

After adequate height is available, the next most significant
criterion affecting long-term survival of implants is the width
of the available bone.
Axial cross-
section on the
root level
showing the
space around
the implant.

Note the little space
between the mesial
and distal surfaces
of the implant and
the adjacent teeth

2. Qualitative Evaluation of BoneAvailability

Hounsfield scale
• Referred to as HU, it is a scale used to measure the bone
density in the CBCT scans. It can measure accurately the
density of the selected point, whether it’s related to bone or
other tissues. HU gives a quantitative assessment of the bone
density where it’s measured by the ability of the tissue to
attenuate x-ray beam.
• HU scale range from -1000 (air) to +3000 (enamel). While
bone quality refers to both thickness and density of the cortical
plates as well as trabecular portion of the bone. This parameter
affects to high limit the success of the treatment.

Example of Trabecular bone
density in the anterior region
of maxilla. Example of
Trabecular bone density in
the anterior region of
maxilla.
Example of Trabecular bone
density in the anterior region
of mandible.Example of Cortical bone
density in the anterior
region of mandible.

Length of the Edentulous Area
Missing upper left
lateral incisor to be
restored with
implant. In 3D and
Axial Slice.

3- Ridge Orientation and morphology:
It is the inclination of the alveolar edentulous ridge. Virtual implantcan be positioned in a
cross sectional alveolar bone using special planning software.
CBCT Shows the type of alveolar bone present
- Cross-sectional CBCT revealing three types of mandibular ridge
morphology:
- line A represents a the line of reference 2 millimeter coronal to the
inferior alveolar nerve canal

Note the
angular
inclination of
the implant
Choosing
the suitable
length and
diameter of
the implant.

Anatomical factors assessed by CBCT imaging
• According to Tolstunov, a Diplomate of the American Board of Oral
Implantology/Implant Dentistry the alveolar jaw can be divided into four
regions or “functional implant zones” with each region posessing "unique
characteristics of anatomy, blood supply, pattern of bone resorption, bone
quality and quantity, need for bone grafting and other supplemental
surgical procedures, and a location related implant success rate.”

Functional Implant Zone 1
Also known as the “traumatic zone”
consists of alveolar ridge of pre-maxilla and the teeth from right to left premolar
exhibits the greatest loss of bone after tooth loss/extraction  occurs in the facio-palatal
or horizontal direction and mainly on the facial side of the alveolar ridge
Any bone loss in this area is crucial due to its esthetic risk with dental implants  if
severe bone loss occurs, implants are harder to place in an esthetically favorable position.
1) Nasopalatine canal
Nasopalatine canal contains:
a. nasopalatine nerve
b. descending branch of the nasopalatine
artery
c. fibrous connective tissue
if an implant contacts neural tissue in this
canal, it could lead to failure of
osseointegration or sensory dysfunction.
Thus, when one or both central incisors have been
lost for a while, limited CBCT imaging is
indicated to determine the dimensions and
morphology of the nasopalatine canal before
dental implant surgery.
Nasopalatine canal on a
CBCT Coronal section

Cross-sectional views showing location
of naso-palatine canal

•the sinus zone
•located at the base of the maxillary sinuses
CBCT imaging is indicated to evaluate:
a. bone height between the floor of the maxillary sinus and alveolar bone must be
evaluated through CBCT before placing dental implants in this zone
b. When tooth is lost or extracted pneumatization of Sinus into the area initially
occupied by the tooth vertical augmentation via a sinus lift procedure
c. presence of sinus septa which could complicate the sinus lift procedure if encountered
interoperatively
CBCT sagittal section showing septa
in left maxillary sinus

d) Detecting superior alveolar artery
A. CBCT shows the posterior alveolar artery before creating a
lateral windown into the maxillary sinus.
B. The artery is seen during the sinus lift procedure located at
15 mm from the alveolar crest diagnosed with CBCT

“Inter-foraminal zone”
This zone is comprised of the area of the mandibular alveolar ridge between mental
foramen and right and left premolar
associated with a thin alveolar ridge
a) Sublingual undercuts
If the alveolar ridge is not properly evaluatedd preoperatively  perforation of lingual
cortex  severe bleeding with the formation of expanding sublingual hematomas
Perforatedlingual
cortical plate
Severe hematoma on the anterior floor
of the mouth after implant placement in
the anterior mandible
Echymosis on the chin after
implant placement in the
anterior mandible

b) Position of mental foramen
Dental implants in the mandibular pre-molar region are dictated by the size and the
location of the mental foramen.
Its location can vary from the mandibular canine to the firstmolar.
Once a zone of safety is detected through CBCT, implants can be placed anterior
to, posterior to, or above the mental foramen.

d) Detection of Accessory Mental Foramens
(AMF) Detecting AMFs may decrease the risk
of haemorrhage, postoperative pain and
paralysis in implant surgeries.

This zone is located behind the mental foramen on each side
and extends from the 2nd premolar to retromolarpad.
a. Mandibular canal through which the InferiorAlveolar
Nerve (IAN) passes
• Any damage to this nerve can result in persistent
dysesthesia as it supplies the sensory innervation of the
lower lip.
• A minimum distance of 2 mm from is to be maintained
when placing implants in this zone.

Sinus FloorElevation
Procedure: The procedure of sinus floor lifting is an inner augmentation of the maxillary sinus sheath, with /without grafts
Purpose: Proliferation of the upright bony measurement of the sinus cavity in the side maxilla. This shaped space customarily allows the
possibility of a dental implant to be inserted from the alveolar ridge to this chamber, to thereafter wait for osseo-integration from the
renewing implanted bone.
Indication: When an implant must be located in the posterior area of the maxilla
Pre-operative valuation of the maxillary sinus is vital for the achievement of this surgery. It is significant for the surgeon to be conscious
of the sizes of the facial maxillary sinus wall earlier in the begining .
Existing 2 D radiological methods do not deliver any treasured data in this field.
Pre-operative cone-beam computed tomography scan (CBCT) prior open sinus lift surgery has been recommended: If
the quantity of bone, among the crest of the ridge and the maxillary sinus bottom is insufficient, (<5 mm) then open sinus lift
process is specified. The CBCT technology permits us to quantify the quantity of bone in this zone:
Post-operative assessment of this procedure using CBCT is also necessary:
The height is more than 5 so a
Sinus lift is not recommended

Existing 2 D radiological methods do not deliver any
treasured data in this field.
Pre-operative cone-beam computed tomography scan (CBCT) prior open sinus lift surgery has
been recommended:
If the quantity of bone, among the crest of the ridge and the maxillary sinus bottom is
insufficient, (<5 mm) then open sinus lift process is specified. The CBCT technology permits us
to quantify the quantity of bone in this zone:
Post-operative assessment of this procedure using CBCT is also necessary:
The height is more than 5 so a Sinus
lift is not recommended

Features (other than the height and the width of the residual alveolar ridge) that should be
assessed in pre-operative CBCT scan for sinus floor lifting include:
Medial wall of the
sinus
Lateral wall of the
sinus
Sinus membrane:
Schneiderian
membrane
a) Wideness of the lateral maxillary sinus wall.
- If the lateral maxillary wall is dense open sinus lift procedure turn
into a more difficult one and more time consuming
- Plummeting the width of bone is essential to diminish problems.
- Extreme convexity of this wall forces the doctor to select exact
methods for this process

b) Occurrence of alveolar antral artery and itsdistance.
- A large diameter artery in the sinus lifting procedure can provoke profuse
bleeding concealing the vision in the surgical field. This blood vessel is
accountable for intraoperative bleeding which is the additional recurrent
problem of sinus lift procedure after membrane puncture. Alveolar antral blood
vessel with a diameter more than 0.5 mm can be observed on CBCT images
and profuse bleeding should be predictable if the artery has a diameter > 3 mm.
- If the entire blood vessel is surrounded by the bone, organization by thermal
cautery is all that is wanted but when this blood vessel is in near contact with
sinus membrane, use of thermal  membrane perforation.
Alveolar antral artery in in close proximity
to the Schneiderian membrane

c) Maxillary sinus floor width.
- It’s the length between the lateral maxillary sinus partition and the medial maxillary sinus partition
(lateral nasal cavity border) and the formed viewpoint.
- In actual thin and very extensive sinuses and sharp angulation between these two constructions,
the open sinus lift surgery becomes hard.
Cone-beam computed tomography (CBCT) scans representing three types of maxillary sinuses with
different widths:
Narrow sinus Average sinus Wide Sinus
a) Indiscretion of sinus floor.
Wrongdoings of the maxillary sinus bottom make the surgery more
problematic in contrast with the flat-surface bone .These irregularities can
be effortlessly noticed using CBCT.
a) Close relative of Schneiderian membrane with roots of nearby teeth
If Schneiderian membrane contacts the adjacent the roots of the teeth head-
to-head to the non-dentate area, the probability of casing puncture during
sinus lift process upsurges.

Postoperative assessment
Postoperative ClinicalAssessment
The patient must be assessed every 6 months, starting from the first 4-6 monthsafter
initial healing of the implants.
Clinical Signs of Implant Failure:
1) Implants lack sensory feedback of occlusal forces. Thus, occlusion must be
monitored, to detect
a. Screw loosening
b. Fracture of the prosthesis
c. Redness, swelling, discomfort
d. Denture ulcers

2) Examine for signs of peri-implant mucositis: inflammation of the soft
tissues surrounding the implant  reversible
3)Examine for signs of peri-implantitis: an inflammatory process affecting
the tissues around an osseointegrated implant in function:
1. Diagnostic feature: crestal bone loss
2. Mobility is its terminal stage
3. Infectious disease  causes of inflammation must be excluded such
as retained cement or cementitis
4) Presence of signs of pain, infection, neuropathies, paresthesia
5)Signs of inflammation such as sinusitis indicating involvement of maxillary
sinus

Postoperative Radiographic
Assessment
Implants should be radiographically assessed on an annual or biannual basis. In the
implant’s first year of service, annual vertical bone loss be less than 0.2 mm is normal
Choice of radiographic technique:
1. For asymptomatic implants:
a. intraoral periapical
b. panoramic imaging in extensive cases
c. CBCT is not indicated for periodic review of asymptomatic implants
2. CBCT imaging
a. Implant mobility
b. altered sensation
c. implant retrievel
Radiographic signs of implant failure:
Peri-implant radiolouceny indicating bone loss: (2mm of loss is
acceptable in the first year, and 0.2mm each year after)
widening of the PDL space of adjacent natural teeth whichindicates
poor stress distribution
Evidence of saucerization indicating loss of crestal bone  apical
migration of the alveolar bone or indistinct osseous margins.

Examination of Implant Failures and Complications
Using CBCT
a. Altered sensation:
• Neurovascular disturbances following most often damage to
several canals is often easily detected by CBCT images allowing
the implantologist to indicate the reason of the patient’s constant
pain or numbness the implant should be removed from the nerve
canal, so that any additional compression of the nerve is eliminated
1. Disturbance to the mandibular canal :
Sagittal CBCT image Coronal CBCT image

2. Damage to the nasopalatine canal
b) Infection or postoperative integration failure
Maxillary sinus infection following sinus floor elevation procedures with simultaneous dental
implant placement may be one of the problems that lead to postoperative complications. This
infection cannot be examined on normal panoramic x-rays.

c) Implant displacement (malpostion)
Displacement of the dental implant into the maxillary sinus. CBCT allows us to examine the
position of the displaced implant in different aspects allowing the implantologist to locate it for
removal. An intraoral approach consisting is needed where an elevation of a mucoperiosteal
flap and creation of a bony window pedicled to the Schneiderian membrane must be adopted in
reference to the CBCT images because perforation of the membrane is highly relevant in such a
procedure.

d)Perforations the implant tip may be shortened until soft tissue
coverage is attained.
1)Perforation of the lingual bone plate in the anterior mandible and
resulting severe hemorrhages and life-threatening airway
obstructions.
2)Perforation of the floor of the nose during implant bed preparation
and/or placement difficulty in breathing and infection

CONCLUSION
Ct Ant Cbct Are Considered As Third Eye To
Maxillofacial Surgeons
These Radiographs Are Used To Dignose Various Types
Of Trauma, Pathologies, Tmds And Interpretation In
Case Of Implants
So Every Maxillofacial Surgeon Should Have A
Profound Idea Regarding The Interpretation Of Ct And
Cbct

REFERENCES
• Oral radiology- principles and interpretation,
white&pharoah
• www. Radiology in thai.com
• Cone beam tomographic imaging anatomy of
maxillofacial region, christos angelopoulos, the dental
clinics of north america

Ct scan and its interpretation in omfs

Ct scan and its interpretation in omfs

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