Diagnostic imaging in implants /certified fixed orthodontic courses by Indian dental academy

DIAGNOSTIC IMAGING IN IMPLANTS

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

HISTORY
CLINCAL

EXAMINATION

Diagnostic
imaging

Mounted study
casts.
Joint assessment
Surgeon/restortive dentist.

Psychological
assessment

Treatment plan
Informed consent

Medical
assessment

Imaging modalities.
1.
2.
3.
4.
5.
6.
7.
8.

•Can also be classified as
Periapical radiography
Analog and digital
Panoramic radiogrphy
2- dimensional and 3Occlusal radiography
dimensional.
Cephalometric radiography
Tomography
Computed tomography
Magnetic resonance imaging.
Interactive computed tomography.

• Imaging modlities can be divided into
– planar two dimensional
– Quasi three dimensional
– Three dimensional


Planar two dimensional.
• It includes
–
–
–
–

Periapical
bite wing
occlusal
cephalometric imaging

• These are simple two dimensional projection of the
patients anatomy.
• It is not possible for the clinician to develop a three
dimensional perspective of the patients anatomy with a
single image.
• With a number of cleverly oriented projections it is
possible to develop some useful three dimensional
information

Quasi three dimensional
• It includes
– X –ray tomography
– Cross sectional panoramic imaging techniques.

• With these techniques, a number of loosely
spaced tomographic images are produced.
• 3-dimensional perspective of the patient
anatomy is developed by viewing each
image and mentally filling in the gaps.

3 dimensional imaging.
• It includes
– Computed tomography.
– Magnetic resonance imaging.

• It enables the clinician to view a volume of
the patients anatomy.
• These techniques are quantitatively accurate
and 3-D models of the patients anatomy can
be derived from the image date and used to
produce stereotactic surgical guides and
prosthetic frameworks.

Implant imaging can be divided
into 3 phases.
• Phase I : Preprosthetic implant imaging.
• Phase II : Surgical and interventional
implant imaging.
• Phase III : Postprosthetic implant

imaging.


Preprosthetic Implant
Imaging.
• It involves
a. All past radiologic examinations.
b. New radiologic examinations to
assist in final and comprehensive
treatment plan.

Objectives
1. To rule out presence of disease at the
proposed surgery site.
2. to determine the bone quantity,
3. to determine the bone density
4. To evaluate the relationship of critical
structures to the prospective implant sites.
5. Determine the optimum position of implant
placement relative to occlusal loads.

Periapical radiography.
• Periapical radiographs provide a high resolution
planar image of a limited region of the jaws.
• No 2 size dental film provides a 25 by 40 mm
view of the jaw with each image.
• Periapical radiographs provide a lateral view of
the jaws and no cross sectional information.
• Adjacent periapical radiographs made with limited
oblique orientations , third dimensional
information is of little use for the implant imaging.

• Periapical radiographs suffer from both
distortion and magnification.
• Millimeter radio opaque grids like those
used in Endodontics can be used – but
usually provide misleading information.


How good are periapical in terms of objectives
of preprosthetic imaging?
• It is a useful high –yield modality for ruling out local
bone or dental disease.
• Is of limited value in determining quantity because the
image is magnified, may be distorted and does not depict
the third dimension of bone width.
• Of limited value in determining bone density or
mineralization (lateral cortical plates prevent accurate
interpretation and cannot differentiate subtle trabecular bone
changes).

• Of value in identifying critical structures. But poor in
depicting spatial relationship between the structures and
the proposed implant site.

• in preprosthetic phase periapical
radiographs are often used for single tooth
implants in regions of abundant bone width.


Occlusal Radiography.
• Occlusal radiographs produce high
resolution planar images of the body of the
mandible or the maxilla.
• Placement of film parallel to the occlusal
plane
• central X-ray
– Mandible: perpendicular to the film
– Maxilla: oblique (usually 45 degrees) to the
film.

•

Maxillary occlusal radiographs are
inherently oblique and so distorted they are
of no quantitative use for implant dentistry.
• Mandibular occlusal radiograph is less
distorted
1. BUT Mandibular alveolus generally flares
anteriorly and demonstrates a lingual
inclination posteriorly, producing an
oblique and distorted image of the
mandibular alveolus, which is of little use
in implant dentistry.

2. Shows widest width of the bone whereas
the width at the crest is of more
diagnostic value.
3. Degree of mineralization of trabecular
bone is not determined from this
projection.
4. Spatial relationship between critical
structures such as mandibular canal and
mental foramen and the proposed implant
site is lost.
• Occlusal radiographs are rarely indicated
for diagnostic preprosthetic phases in
implant dentistry

Cephalometric radiographs
• Cephalometric radiographs are oriented planar
radiographs of the skull.
• The skull is oriented with respect to the x-ray
device and the image receptor using a
Cephalometer.
• The geometry of cephalometric imaging devices
results in a 10% magnification of the image with a
60 inch focal object and a 6 inch object to film
distance.

• Lateral cephalometric radiograph:
– is produced with the patients mid sagittal
plane oriented parallel to the image
receptor.
• With a slight rotation of the Cephalometer,
a cross sectional image of the mandible or
maxilla can be demonstrated in the lateral
incisor or in the canine regions as well.


1. It demonstrates the geometry of the alveolus in
the anterior region and the relationship of the
lingual plate to the patients skeletal anatomy.
Useful in placing mandibular anterior implants.
2. Width of the bone in symphysis region- for
harvesting this bone for ridge augmentation.
3. Together with regional periapical radiographs
spatial relationships can be visualized.
4. Evaluating loss of vertical dimension
5. Skeletal arch interrelationship
6. Anterior implant crown ratio
7. Anterior tooth position in prosthesis
8. Resultant moment of force.

• This technique is not useful for
demonstrating bone quality.
• It is useful tool for the development of an
implant treatment plan especially for the
completely edentulous patient.


Panoramic radiography.
• It is a curved plane tomographic radiographic
technique used to depict the body of the
mandible, maxilla, and the lower one half of the
maxillary sinuses in a single image.
• It is probably the most utilized diagnostic
modality in implant dentistry Though it is not
the most diagnostic.
• It produces an image of a section of the jaws of
variable thickness and magnification.

• Tomographic section thickness is
approximately 20mm in the posterior region
and 6 mm in anterior region.
• Image receptor has traditionally been an Xray film but may be a digital storage
phosphor plate or a digital CCD receptor.


• Non uniform magnification of structures
produces images with distortion that cannot
be compensated for in treatment planning
• Vertical magnification is approximately
10%.
• Horizontal magnification is 20% and varies
according to
•
•
•
•

anatomic location.
Position of the patient
Focus object distance.
Location of the rotation center

•

Disadvantages
1. Does not demonstrate bone
quality/mineralization.
2. Is misleading quantitatively because of
magnification and because the third dimension,
cross sectional view is not demonstrated.
3. Is of some use in demonstrating critical structures
but of little use in depicting the spatial
relationship between the structures and
dimensional quantification of the implant site.
4. Dimensions of inclined structures cannot be
relied upon in panoramic radiographs.

• Advantages.
1.Opposing landmarks are easily identified
2.The vertical height of bone initially can be
assessed.
3.Te procedure is performed with convenience,
ease ,and speed inmost dental offices.
4.Gross anatomy of the jaws and any related
pathologic findings can be evaluated.


• Posterior maxillary regions are generally
the least distorted regions of the panoramic
radiographs.
• Maxillary edentulous anterior region is
often the most difficult area of a panoramic
radiograph to evaluate because of the
curvature of the alveolus and the inclination
of the bone.

Zonography
• This is a modification of the panoramic xray machine with the capability of making a
cross sectional image of the jaws.
• This technique enables the appreciation of
spatial relationship between the critical
structures and the implant site and
quantification of the geometry of the implant
site.

tomography
• It is a generic term,formed from the reek
words tome(slice ) and graph(picture).
• It was adopted in 1962 by the international
commission on radiologic units and
measurements(ICRU) to describe all forms
of body section radiography.


Components.
• Fulcrum bar
• Fulcrum : it remains stationary and defines the
section of interest or the tomographic layer.
• Different tomographic sections are produced by
adjusting the position of the fulcrum or the
position of the patient relative to the fulcrum in
fixed geometry systems.


• Linear tomography is the simplest form of
tomography where the X-ray tube and film
move in a straight line.

• Complex motion, high quality
tomography is described by two dimensional
motion of the tube and film.
– It results in relatively uniform blurring of the
regions of the patients anatomy adjacent to the
tomographic section.
– Hypocycloidal motion is generally accepted as the
most effective blurring motion.

• Large amplitude tube travel and 1 mm sections
are preferred for high contrast anatomic
objects whose geometry changes in a
relatively short distance,such as the alveolus of
the jaws
• Complex motion tomography helps in
– Quantification of the geometry of the alveolus.
– Determining spatial relationship between critical
structures.
– Quantity of alveolar bone available.

• Complex tomography is not particularly useful
in determining bone quality or identifying
dental and bone www.indiandentalacademy.com
diseases

Computed tomography.
• Computed tomography(CT) is a digital and
mathematical imaging technique that
creates tomographic sections where the
tomographic layer is not contaminated by
blurred structures from adjacent anatomy.


• It enables differentiation and quantification
of both soft and hard tissue.
• CT was invented by sir Hounsfield and
announced to the imaging world in1972.
• Ct produces axial images of a patients
anatomy .
• Axial images are produced perpendicular to
the long axis of the body.

• The X-ray source is attached rigidly to a fan-beam
geometry detector array,which rotates 360 degrees
around the patient and collects data.
• The image detector is either a a gaseous or solid state
producing electronic signals that serve as input data
for a dedicated computer.
• The computer processes the data using back projection
Fourier algorithm techniques.
• The individual element of the CT image is called a
voxel,which has a value,referred to in hounsfield units,
that describe the density of the CT image at that point

• Ct scanners are standardized at a hounsfield value
of 0 for water.
• The CT density scale is quantitative and
meaningful in identifying and differentiating
structures and tissues.
• The original imaging computer can create
secondary images from almost any perspective by
reprojecting or reformatting the original three
dimensional voxel data.

• The utility of CT for dental implant
treatment planning was obvious from the
beginning
• But the access to these imaging techniques
was limited.
• This led to development of specific
techniques generally referred to as
Dentascan imaging.

Tissue
Air
Water
Muscle
Fibrous tissue
Cartilage
Trabecular bone
Corticalbone
Dentine
Enamel.

Hounsfield units
-1000
0
35-70
60-90
80-130
150-900
900-1800
1600-2400
2500-3000

Density

Hounsfield units

D1

>1250

D2

850-1250

D3

350-850

D4

150-350

D5

<150


Dentascan
• The radiologist simply indicates the curvature of
the mandibular or maxillary arch.
• the computer is programmed to generate
referenced cross sectional and
tangential/panoramic images of the alveolus along
with 3-D images of the arch.
• The cross sectional and panoramic images are
spaced 1mm apart and enable accurate
preprosthetic treatment planning.

Limitations of dentascan.
1. Images may not be of true size and require
compensation for magnification.
2. Determination of bone quality requires use of the
imaging computer or workstation.
3. Hard copy dentascan images only include a
limited range of the diagnostic gray scale of the
study.
4. Tilt of the patients head during the examination
is critical because all the cross sectional images
are perpendicular to the axial imaging plane

• CT enables
–
–
–
–

Identification of disease
Determination of bone quality
Identification of critical structures
Determines orientation and position of implants

• Thus CT is capable of determining all five
of the radiologic objectives of the
preprosthetic implant imaging.
• Usually a diagnostic template is necessary
to take full advantage of the technique.

Interactive computed
tomography(ICT)
• It address many of the limitations of CT.
• ICT is a technique that was developed to
bridge the gap in information transfer
between the radiologist and the clinician.
• The radiologist transfers the imaging study
to the clinician as a computer file for
clinician to view and interact with the
image in their own computer.

• Clinicians computer becomes a diagnostic
radiologic workstation with tools to
measure the length and width of the
alveolus,measure bone quality ,and change
the window and level of gray scale of the
study to enhance the perception of critical
structures.
• An important feature of the ICT is that the
clinician and radiologist can perform
“electronic surgery “ (ES) by selecting and
placing arbitrary size cylinders that simulate
root form implants in the images.

Limitations of ICT.
• Refinement and exact orientation of the
implant positions is difficult and
cumbersome.
• Executing the plan maybe difficult for the
surgical team.


Magnetic resonance imaging.
• MR is a imaging technique used to image
the protons of the body by employing
magnetic fields, radio frequencies,electro
magnetic detectors,and computers.
• The technique was first announced by
lauterbur in 1972.
• It is a 3 dimensional imaging technique
with an electronic image acquisition process
and a resulting digital image.

• The image sequence employed to obtain MR
images can be varied to obtain fat,water, or
balanced imaging of the patients anatomy.
• MR images are the antithesis of CT images
with cortical bone appearing dark or black
and fat or water appearing bright or white.
• Like CT,MR is a quantitatively accurate
technique with exact tomographic sections
and no distortions.


• Complex tomography fails to differentiate the
inferior alveolar canal in 60% of the implant
cases
• CT fails to differentiate the inferior alveolar
canal in approximately 2% of implant cases.
• MR visualizes the fat in trabecular bone and
differentiates the inferior alveolar canal and
neurovascular bundle from the adjacent
trabecular bone.


• MR is used in implant imaging as a
secondary imaging technique when primary
imaging techniques such as complex
tomography,CT or ICT fail.
• MR is not useful in characterizing bone
mineralization or a high yield technique for
identifying bone of dental disease.


Surgical and interventional implant
imaging
•
•

It assists in the surgical and prosthetic
intervention of the patient.
Objectives
1) Evaluate the surgery sites during and immediately
after surgery.
2) Assist in the optimal position and orientation of the
dental implants
3) Evaluate the healing and integration phase of implant
surgery.
4) Ensure abutment position and prosthesis fabrication
are correct. www.indiandentalacademy.com

• As most implant surgeries are performed in
the doctors office rather than in hospital ,the
modalities are usually limited to periapical
and panoramic radiography.
• The patient can be generally imaged at
chair side with periapical radiography to
determine implant/osteotomy depth,position
and orientation.
• Disadv : approximately 5 minutes are
required in dark room procedure.

• An x –ray examination is also performed to
determine if the metal framework or final
restoration is completely seated,and the
margins are acceptable around the implant
or teeth.


Postprosthetic implant imaging.
•

•

It commences just after the prosthesis
placement and continues as long as the
implants remain in the jaws.
Objectives
1. Evaluate the long term maintenance of implant
rigid fixation and function.
2. Evaluate crestal bone levels
3. Evaluate the implant complex

Bite wing radiographs
• The short and long term evaluation of
crestal bone loss around implants is best
evaluated with Intraoral radiographs.
• In these images ,the superior one third of
the implant is the region of interest.threaded
implants make quantification of marginal
bone loss easier to read.

Temporal digital subtraction
radiography(SR).
• It is a radiographic technique that enables two
radiographs made at different points of time of the
same anatomic region to be subtracted resulting in
an image of the difference between the two
original radiographs.
• The resulting image shows changes inpatients
anatomy,such as alveolar mineralization or
volume changes.

• SR has been shown to be considerable
more accurate at depicting changes in bone
mineralization and bone volume than
simply viewing the original periapical
radiographs.
• SR has limited utilization in clinical
practice because of the difficulty in
obtaining reproducible periapical
radiographs.


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Diagnostic imaging in implants /certified fixed orthodontic courses by Indian dental academy

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