Diagnostic imaging./ cosmetic dentistry training

Diagnostic imaging
and techniques in
implant dentistry
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Introduction
Diagnostic imaging and techniques help to develop
and implement a cohesive and comprehensive
treatment plan for the implant team and the
patient. The decision of when to image along with
which imaging modality to use depends on the
integration of these factors and can be organized
into three phases

Phase one is termed pre-prosthetic implant imaging
and involves all past radiologic examinations along
with new radiologic examinations chosen to assist the
implant team in determining the patient’s final and
comprehensive treatment plan. The objectives of this
phase of imaging include all necessary surgical and
prosthetic information to determine the quantity,
quality, and angulation of bone; the relationship of
critical structures to the prospective implant sites;
and the presence or absence of disease at the
proposed surgery sites.

Phase two is termed surgical and interventional
implant imaging and is focused on assisting in the
surgical and prosthetic intervention of the patient.
The objectives of this phase of imaging are to evaluate
the surgery sites during and immediately after
surgery, assist in the optimal position and orientation
of dental implants, evaluate the healing and
integration phase of implant surgery, and ensure
abutment position and prosthesis fabrication are
correct.

Phase three is termed post-prosthetic implant
imaging. It commences just after the prosthesis
placement and continues as long as the implants
remain in the jaws. The objectives of this phase of
imaging are to evaluate the long-term maintenance
of implant rigid fixation and function, including
the crestal bone levels around each implant, and to
evaluate the implant complex.

Imaging modalities
Once a decision to image the patient has been
made, the imaging modality is employed that
yields the necessary diagnostic information
related to the patient’s clinical needs and results
in the least radiologic risk. Some of the imaging
modalities that have been reported as useful for
dental implant imaging include,

• Periapical radiography
• Panoramic radiography
• Occlusal radiography
• Cephalometric radiography
• Tomography
• Computed tomography
• Magnetic resonance imaging
• Interactive computed tomography

The imaging modalities listed above can be sub
divided into planar two dimensional, quasi three
dimensional, and three-dimensional imaging
modalities. Planar imaging modalities include
periapical bite wings, occlusal and cephalometric
imaging and are simply two dimensional projections
of the patient’s anatomy. Thus, it is not possible for
the clinician to develop a three-dimensional
perspective of the patient’s anatomy with a single
image.

Quasi three-dimensional imaging modalities include
x-ray tomography and some cross sectional
panoramic imaging techniques. With these
techniques, a number of closely spaced tomographic
images are produced and the three dimensional
perspective of the patient’s anatomy is developed by
viewing each image and mentally filling in the gaps.
Three-dimensional imaging techniques
include computed tomography and magnetic
resonance imaging and enable the clinician to view a
volume of the patient’s anatomy. These techniques
are quantitatively accurate and three-dimensional
models of the patient’s anatomy can be derived fromwww.indiandentalacademy.com

Most dentists are more familiar with analog, two-
dimensional imaging. Analog imaging modalities are
two-dimensional systems that employ x-ray film and/or
intensifying screens as the image receptors
Digital images can also be produced with each
imaging modality listed before. A digital two-
dimensional image is described by an image matrix that
has individual picture elements called pixels. A digital
image is described by its width and height and pixels
(i.e., 512 by 512). For larger digital image (i.e., 1.2M by
1.2M [M= megapixel]), the image is alternatively
described as a 1.5 megapixel image. Each picture
element or “pixel” has a discrete digital value that
describes the image intensity at that particular point.
The value of a pixel element is described by a scale,www.indiandentalacademy.com

which may be as low as 8 bits (256 values) or as high as
12 bits (4096 values) for black and white imaging
systems, or 36 bits (65 billion values) for color imaging
systems. Black and white digital images are optimally
displayed on a dedicated black and white monitor.
Generally, 8 bits or 256 levels can be effectively
displayed on a monitor
A digital three-dimensional image is described by
an image matrix that has individual image/picture
elements called voxels. A digital three-dimensional
image is described not only by its width and height and
pixels (i.e., 512 by 512), but additionally, by its
depth/thickness. An imaging volume or three-
dimensional characterization of the patient is produced
by contiguous images, which produces a threewww.indiandentalacademy.com

dimensional structure of volume elements (i.e.,
computed tomography, magnetic resonance imaging
and interactive computed tomography). Each volume
element has a value that describes its intensity level.
Typically, three-dimensional modalities have an
intensity scale of 12 bits or 4096 values. The three-
dimensional imaging modalities are as follows,
• Computed tomography
• Magnetic resonance imaging
• Interactive computed tomography

Preprosthetic imaging
This phase of implant imaging is intended to evaluate
the current status of the patient’s teeth and jaws and to
develop and refine the patient’s treatment plan.
The specific objectives of preprosthetic imaging are to,
1. Identify disease
2. Determine bone quantity
3. Determine bone density
4. Identify critical structures at the proposed implant
regions
5. Determine the optimum position of implant
placement relative to occlusal loads.

Periapical radiography
Periapical radiographs are images of a limited region
of the mandibular or maxillary alveolus. Periapical
radiographs are produced by placing the film
intraorally parallel to the body of the alveolus with the
central ray of the x-ray device perpendicular to the
alveolus at the region of interest, producing a lateral
view of the alveolus. Periapical radiographs provide a
lateral view of the jaws and no cross sectional
information.
Periapical radiographs may suffer from both distortion
and magnification. The long cone paralleling
technique will eliminate distortion and limit
magnification to less than 10%.www.indiandentalacademy.com

Burn out effects are common when standard kV and mA
are used, making crestal bone loss with digital intraoral
systems of benefit in these situations.
In terms of the objectives of pre-prosthetic imaging,
periapical radiography is
1. A useful high yield modality for ruling out local
bone or dental disease.
2. Of limited value in determining quantity because
the image is magnified, may be distorted, and does not
depict the third dimension of bone width,
3. Of limited value in determining bone density or
mineralization (the lateral cortical plates prevent accurate
interpretation and cannot differentiate subtle trabecularwww.indiandentalacademy.com

bone changes) .
4. Of value in identifying critical structures, but of
little use in depicting the spatial relationship between
the structures and the proposed implant site. In the
pre-prosthetic phase, these films are most often used for
single tooth implants in regions of abundant bone
width.

Occlusal radiography
Occlusal radiographs are planar radiographs
produced by placing the film intraorally parallel to the
occlusal plane with the central x-ray perpendicular to
the film for the mandibular image and oblique (usually
45 degrees) to the film for the maxillary image.
Occlusal radiography produces high-resolution planar
images of the body of the mandible or the maxilla.
Maxillary occlusal radiographs are inherently oblique
and so distorted they are of no quantitative use for
implant dentistry, for either determining the geometry
or the degree of mineralization of the implant site.
Additionally, critical structures such as the maxillary
sinus, nasal cavity and nasal palatine canal are
demonstrated but the cavity, and nasal palatine canalwww.indiandentalacademy.com

are demonstrated, but the spatial relationship to the
implant site is generally lost with this projection.
Because the mandibular occlusal radiograph is an
orthogonal projection, it is less distorted projection
than the maxillary occlusal radiograph. However, the
mandibular alveolus generally flares anteriorly and
demonstrates a lingual inclination posteriorly. It
produces an oblique and distorted image of the
mandibular alveolus, which is of little use in implant
dentistry. As a result, occlusal radiographs are rarely
indicated for diagnostic pre-prosthetic phases in
implant dentistry.

Cephalometric radiographs
Cephalometric radiographs are oriented planar
radiographs of the skull. A cross sectional image of the
alveolus of both the mandible and the maxilla in the
midsagittal plane is demonstrated by this radiograph.
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. The lateral cephalometric radiograph
is useful because it demonstrates the geometry of the
alveolus in the anterior region and the relationship of
the lingual plate to the patient’s skeletal anatomy. The
width of bone in the symphysis region and the
relationship between the buccal cortex and the roots ofwww.indiandentalacademy.com

the anterior teeth may also be determined before
harvesting this bone for ridge augmentation.
Together with regional periapical radiographs,
quantitative spatial information is available to
demonstrate the geometry of the implant site and
spatial relationship between the implant site and the
spatial relationship between the implant site and
critical structures such as the floor of the nasal palatine
canal. Additionally the lateral cephalometric view can
help evaluate a loss of vertical dimension, skeletal arch
interrelationship, anterior crown implant ratio,
anterior tooth position in the prosthesis and resultant
moment of forces.

If desired foil can be placed over the anterior teeth in
a set of dentures, which if worn during exposure of
the lateral cephalogram, can demonstrate clearly the
relationship of the teeth to the ridge and the ridge
relationship. This provides insight as to angulation of
the implants to place them in ideal locations for the
implant supported or tissue supported prosthesis.
However, this technique is not useful for
demonstrating bone quality.

Panoramic radiography
Panoramic radiography 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.
Panoramic images offer the following advantages,
1. Opposing landmarks are easily identified.
2. The vertical height of bone initially can be
assessed
3. The procedure is performed with convenience,
ease, and speed in most dental offices.
4. Gross anatomy of the jaws and any relatedwww.indiandentalacademy.com

Panoramic Magnification:
Panoramic radiography is characterized by an image
of the jaws that demonstrates both vertical and
horizontal magnification, along with a tomographic
section, thickness that varies according to the
anatomic position.
Nonuniform magnification of structures produces
images with distortion that cannot be compensated
for in treatment planning. The posterior maxillary
regions are generally the least distorted regions of a
panoramic radiograph.

Panoramic radiography
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
quantitation of the implant site.

Because panoramic radiography is such a popular
and widely available technique in dentistry, clinicians
have developed means to compensate for panoramic
radiography’s shortcomings.
It has been demonstrated recently that the use of
templates with incorporated metal spheres of known
diameter in situ when the radiograph is taken can
effectively eliminate the distortion problems. The
metal spheres appear radiopaque in the final film.
Because their diameter is known, it is easy to calculate
the true bone height.

Here is an example of the calculation for the posterior
region: The true diameter of the sphere (D-real) is 5
mm, but its diameter on the radiograph (D-PR) is
measured at 6 mm. The distance between the alveolar
crest and the mandibular canal is measured on the film
as 18mm (A-PR). To determine the real distance
between the alveolar crest and the mandibular canal
(A-real), simply solve the following equation.
A-real / A-PR = D-real / D-PR
A-real = 18 × 5 / 6
A-real = 15 mm

However, studies have demonstrated the mandibular
foramen cannot be identified 30% of the time on the x-ray
and when visible may not identified correctly.
Dimensions of inclined structures cannot be relied
upon in panoramic radiographs.
Recently a modification of the panoramic x-ray
machine has been developed that has the capability of
making a cross sectional image of the jaws. These devices
employ limited angle linear tomography (zonography) and
a means for positioning the patient. The tomographic
layer is approximately 5 mm. 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. This technique is not usefulwww.indiandentalacademy.com

for determining the differences in most bone densities
or identifying disease at the implant site.
Tomography
Tomography is a generic term, formed from the Greek
words tomo (slice) and graph (picture). Body section
radiography is a special x-ray technique that enables
visualization of a section of the patient’s anatomy by
blurring regions of the patient’s anatomy above and
below the section of interest.
There have been many ingenious tomographic
methods and devices. However, the basic principle of
tomography is that the x-ray tube and film are
connected by a rigid bar called the fulcrum bar, whichwww.indiandentalacademy.com

pivots on a point called the fulcrum. When the system
is energized, the x-ray tube moves in one direction with
the film plane moving in the opposite direction and
system pivoting about the fulcrum. The fulcrum
remains stationary and defines the section of interest,
or the tomographic layer. Factors that affect
tomographic quality are the amplitude and direction
of tube travel. The greater the amplitude of tube
travel, the thinner the tomographic section. Linear
tomography is the simplest form of tomography where
the x-ray tube and film move in a straight line.
Circular, spiral, and hypocycloidal are tube motions
employed in complex tomography. Magnification
varies from approximately 10% to 30% with higher

magnification generally producing higher quality
images.
For dental implant patients high quality complex
motion tomography demonstrates the alveolus, and
taking magnification into consideration, enables
quantification of the geometry of the alveolus. This
technique also enables determination of the spatial
relationship between the critical structures and the
implant site. Ideally, tomographic section spaced every
1 or 2 mm enable evaluation of the implant site region,
and with mental integration, enable appreciation of the
quasi three dimensional appearance of the alveolus.
The quantity of alveolar bone available for implant
placement can be determined by compensation for
magnification. Post imaging digitization of tomographicwww.indiandentalacademy.com

implant images enables use of a digital ruler to aid
in the determination of alveolar bone for implant
placement. Image enhancement can aid in
identifying critical structures such as the inferior
alveolar canal.

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.
Additionally, and probably most important,
computed tomography enables differentiation and
quantification of both soft and hard tissues.
CT was invented by sir Hounsfield and announced to
the imaging world in 1972. CT images are inherently
three dimensional digital images typically 512 by 512
pixels with a thickness described by the slice spacing
of the imaging technique.

The individual element of the CT image is called a
voxel, which has a value, referred to in Hounsfield
units, that describes the density of the CT image at
that point. Each voxel contains 12 bits of data and
ranges from –1000 (air) to +3000 (enamel/dental
materials) Hounsfield units. 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 density of structures within the image is
absolute and quantitative and can be used to
differentiate tissues and the region and characterize
bone quality. www.indiandentalacademy.com

CT enables identification of disease, determination
of bone quantity, identification of critical structures
at the proposed regions, and determination of the
position and orientation of the dental implants.
Thus CT is capable of determining all five of the
radiologic objectives of pre-prosthetic implant
imaging

Interactive computed tomography
This technique enables the radiologist to transfer the
imaging study to the clinician as a computer file and
enable the clinician to view and interact with the
imaging study on their own computer. The
clinician’s computer becomes a diagnostic radiologic
workstation with tools to measure the length and the
width of the alveolus, measure bone quality and
change the window and level of the gray scale of the
study to enhance the perception of critical structures.
An important feature of ICT is that the
clinician and radiologist can perform “electronic
surgery” (ES) by selecting and placing arbitrary size

cylinders that stimulate root form implants in the
images. With an appropriately designed diagnostic
template, ES can be performed to electronically
develop the patient’s treatment plan in three
dimensions.
With the number and size of implants accurately
determined along with the density bone at the
proposed implant sites, characteristics of implants can
be accurately determined before surgery. At this time,
ICT is the most accurate imaging technique for
implant imaging and surgery but suffers some
limitations. ES enables placement of electronic
implants in the imaging study but refinement and
exact relative orientation of the implant positions is

difficult and cumbersome. Transfer of the plan to the
patient at the time of surgery can be accomplished by
simple visualization and comprehension by a skilled
and experienced surgeon, using positions and
orientations obtained from ICT and ES to convert the
diagnostic template into a surgical template. It can
also be accomplished by the production of the
computer generated, three-dimensional stereotactic
surgical templates from the digital ICT and ES data.

Magnetic resonance imaging
Magnetic resonance (MR) imaging is a technique
developed in medical imaging that is probably the most
innovative and revolutionary other than computed
tomography. MR is an imaging technique used to image
the protons of the body by employing magnetic field,
radio frequencies, electromagnetic detectors, and
computers. The technique was first announced by
Lauterbur in 1972.
Digital MR images are characterized by voxels with
an in-plane resolution measured pixels (512 by 512) and
millimeters and section thickness measured in
millimeters (2 to 3 mm) for high resolution imaging
acquisitions.

MR is used in implant imaging as a secondary imaging
technique when primary imaging techniques such as
complex tomography, CT, or ICT fail. Complex
tomography fails to differentiate the inferior alveolar
canal in 60% of implant cases and CT fails to
differentiate the inferior alveolar canal in
approximately 2% of implant cases. Failure to
differentiate the inferior alveolar canal may be caused
by osteoporotic trabecular bone and poorly corticated
inferior alveolar canal. MR visualizes the fat in
trabecular bone and differentiates the inferior alveolar
canal and neurovascular bundle from the adjacent
trabecular bone.
MR is not useful in characterizing bone mineralization
or for identifying bone or dental disease.www.indiandentalacademy.com

Diagnostic templates
The purpose of diagnostic radiographic templates is
to incorporate the patient’s proposed treatment
plan into the radiographic examination. This
requires that a treatment plan be developed prior to
the imaging procedure.
The pre-prosthetic imaging procedure enables
evaluation of the proposed implant site at the ideal
position and orientation identified by radiographic
markers incorporated into the template.

Computed tomography
The precision of CT enables use of complex and
precise diagnostic template. The exact position and
orientation of the implant, which many times
determines the actual length and diameter of the
implant, is often dictated by the prosthesis. As such,
a diagnostic template used during imaging is most
beneficial. The surfaces of the proposed restorations
and the exact position and orientation of each dental
implant should be incorporated into the diagnostic
CT template.

There are two diagnostic templates, one
produced from the vacuform reproduction, and one
produced from a processed acrylic reproduction of the
diagnostic wax-up.
The processed acrylic template is modified by coating
the proposed restoration with a thin film of barium
sulfate and filling a hole drilled through the occlusal
surface of the restoration with gutta percha. The
surfaces of the proposed restoration then become
radiopaque in the CT examination and the position and
orientation of the proposed implant is identified by the
radiopaque plug of gutta percha within the proposed
restoration.

The vacuform template has a number of variations.
One design involves coating the proposed restorations
with a thin film of barium sulfate. Another design
involves filling the proposed restoration sites in the
vacuform of the diagnostic wax up with a blend of
10% barium sulfate and 90% cold cure acrylic. This
results in a radiopaque tooth appearance of the
proposed restorations in the CT examination. The last
design modifies the previous design by drilling a 2 mm
hole through the occlusal surface of the proposed
restoration at the ideal position and orientation of the
proposed restoration at the ideal position and
orientation of the proposed implant site with a twist
drill. This results in a natural tooth like appearance to
the proposed restoration in the CT examination where
all the surfaces for the restoration are evident along

with a 2-mm. radiolucent channel through the
restoration, which precisely identifies the position and
orientation of the proposed implant.

The circumference guide only traces the outline of the
planned prosthesis; it does not provide necessary
transposition of prosthetic and/ or bone angulation
information. The vertical lead strip and gutta-percha
guides serve primarily as imaging indicators and
allow for some surgical latitude in preparation of
osteotomy sites. The metal sleeve guide used in
conjunction with a set up disk appears to be the most
accurate imaging and surgical guide. It serves as an
imaging and a precision surgical osteotomy guide,
ensuring consistency between the planned prosthetic
angulation (confirmed by diagnostic imaging) and the
trajectory of osteotomy during the surgical phase.

Although intracoronal cylinders and barium sulfate
allowed one to evaluate the relationship of the final
restoration to available bone, problems still existed.
First, the adjacent cross-sections in the CT study
appeared similar, and identifying a specific area posed
problems. Second, because intracoronal markers were
removed before or during surgery, the ability to
maintain the proper orientation determined from the
CT scan was lost.
Maintaining proper orientation can be achieved by use
of a diagnostic/surgical template with an external guide
wire and precision milled cylinders, used initially
during the radiographic imaging phase and then
subsequently during the surgical phase. The locationwww.indiandentalacademy.com

and inclination of theintended implant placement can
be transferred accurately to the diagnostic/surgical
template by use of precision milled cylinders. These
cylinders are placed in the template at the proper
angulation and linear dimensions are extrapolated
from the CT. Incorporation of wires placed on the
buccal surface of the template allows identification of
the preferred implant site. Once the cylinder is
removed, the externally placed buccal wire remains a
constant and consistent reference point to be used
throughout the surgery. Kevin. C. Kopp etal in their
article illustrated a technique to allow precise implant
placement with customized barium-coated
diagnostic/surgical templates, internal precision

milled cylinders, external guide wires with a CT scan,
and interactive software to facilitate improved
presurgical implant diagnostics and prosthetically
directed implant placement.
Fig. 1. Acrylic resin teeth luted in place and occlusion
verified

Fig. 2. Buccal wire luted in place.

Fig. 3. Cross-sections in SIM/Plant of desired sections.
Frame 37 demonstrates buccal wire (arrow).www.indiandentalacademy.com

Fig. 4. Implant replica placed at ideal
angulation.

Fig. 5. A, Angulation to buccal wire is calculated.
B, Linear relationship to buccal wire is calculated.

Fig. 6. A, Modified surveyor table is adjusted to correct
buccal-lingual and mesiodistal angulation as
determined from SIM/Plant. Protractor is used to
determine angle on surveyor table. B, Finalized position
of surveyor table spatially.www.indiandentalacademy.com

Fig. 7. A, Cylinders fixed in proper position with guide
pins to verify alignment. B, Final implant placement.

Fig. 8. A, Prepared abutments.
B, Provisional restoration.

Tomography
Diagnostic templates for tomography examinations are
generally less precise than those required in CT
examinations. The diagnostic information available
from tomography examinations is not as detailed or as
a precise as that available from CT examinations. The
simplest tomography template is produced by
obtaining a vacuform of the patient’s diagnostic cast
with 3-mm. ball bearing placed at the proposed
implant positions. A number of tomograms of the
implant region are produced with the implant site
identified by the one in which the ball bearing is in
sharp focus. The ball bearing can additionally serve as
a measure of the magnification of the imaging system.www.indiandentalacademy.com

Templates that incorporate metal cylinder or tubes at
the proposed implant sites also enable evaluation of
tomograms for the orientation along with the
position of the proposed implant.
Surgical templates
Diagnostic templates can be modified and used as
surgical templates. If metamorphosis from
diagnostic template to surgical template is the
objective of the surgeon, the diagnostic template
should be selected and fabricated with that in mind.

CAD CAM stereotactic surgical templates
Anatomically accurate three-dimensional models of
the patient’s alveolar anatomy can be produced by a
number of cadcam and rapid prototyping procedures.
Cadcam surgical stereotactic templates can be
produced from CT examinations that have used
interactive CT to develop a three-dimensional
treatment plan for the patient of the position and
orientation of dental implants.
A stereotactic surgical template is derived from the
model by aligning guide cylinders at the implant sites,
which just accommodate a pilot drill, and producing a
vacuform using surgical template material of the model
and guide cylinders. This results in a plastic surgical

template that fits and conforms to patient’s bony
anatomy and supports the position and orientation of
the guide cylinders, which precisely reproduce the
position and orientation of the proposed implants.

Surgical and Interventional imaging
Surgical and interventional imaging involves
imaging the patient during and immediately after
surgery, and during the placement of the prosthesis.
The purpose of surgical imaging is to evaluate the
depth of implant placement, the position and
orientation of implants/osteotomies, and to evaluate
donor or graft sites.
The patient can be generally imaged at chair
side with periapical radiography to determine implant
osteotomy depth position, and orientation.
Corrections for magnification, similar to those
employed in endodontics, are necessary to quantify the
depth of the osteotomy. The disadvantage of

periapical radiography is that a darkroom and
approximately 5 minutes per radiograph for film
processing is generally required. Digital periapical
image receptors enable virtually instantaneous image
acquisition, produce image quality similar to that of
dental film, and enable the surgical procedure to
proceed without undue delay. For extensive implant
procedures that may involve the entire jaw, both jaws,
large donor graft sites, or sinus graft augmentation
panoramic radiography will provide a more global
view of the patient’s anatomy.
Periapical or digital periapical radiography are useful
modalities to determine if the implant components and
prosthesis are seated or fitted appropriately.www.indiandentalacademy.com

The anti-rotation devices of the implant body may
prevent the abutment form seating in the correct
position. This may be difficult to ascertain because
the implant crest module is often at the bone crest
and the tissue is several millimeters thick. An x-ray
examination is also performed to determine if the
metal framework and or final restoration is
completely seated, and the margins are acceptable
around the implants and/or teeth. The important
portion to image is the crestal aspect of the implant
not the apex.

Post-prosthetic imaging
The purpose of post prosthetic implant imaging
is to evaluate the status and prognosis of the dental
implant. The bone adjacent to the dental implant
should be evaluated on a routine basis for changes in
mineralization or bone volume. Loss of cylindrical
bone volume adjacent to the implant surface may
indicate excessive axial or shear loading, bone
damage during implant placement, integration failure
with an epithelial bone implant interface,
inflammation, and/or infection.

Periapical radiography
The implant bone interface is depicted only at the
mesial, or distal, inferior, and crestal aspects or, where
the central ray the x-ray source is tangent to the
implant surface. Other regions of the implant
interface are simply not depicted well by this modality.
Bite-wing radiographs
The short and long-term evaluation of crestal
bone loss around implants is best evaluated with
intraoral radiographs. Threaded implants make
qualification of marginal bone loss easier to read.
Most threaded implants have a smooth crestal region
that measures 0.8 to 2 mm, depending on thewww.indiandentalacademy.com

manufacturer, before the threads begin. Once the
threads begin, there is a consistent pitch (distance
between the threads). As a result, the amount of
crestal bone loss can be determined when compared to
the original implant insertion and initial radiograph of
the prosthesis.
The image is optimal when the implant body threads
can be seen clearly on both sides.

Temporal digital subtraction radiography
Temporal digital subtraction radiography (SR) is a
radiographic technique that enable 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
substraction image depicts changes in the patient’s
anatomy such as alveolar mineralization or volume
changes during the time between which the two
radiographs were made. In addition to identifying mesial
and distal changes in the alveolar bone, SR can also depict
buccal and lingual changes in alveolar bone.
SR has had limited utilization in clinical practice because
of the difficulty in obtaining reproducible periapical
radiographs.

Computed tomography
Although CT cannot match the resolution of SR or
periapical radiography, the quantitative gray scale
and three-dimensional characteristics of CT enable
evaluation of the bone implant interface in all
orientations. Failing implants characterized by
trabecular and crestal demineralization; resorption of
the bone implant interface; cortical plate fenestration;
and perforation of the inferior alveolar canal cortical
plates, and nasal cavity or maxillary sinus floor can be
identified with CT.
The three dimensional imaging capabilities of CT
enable precise evaluation of the position of dental
implants relative to critical structures such as thewww.indiandentalacademy.com

inferior alveolar canal, the mental foramen,
maxillary sinus, nasal cavity incisive foramen,
anterior loop, adjacent teeth, buccal or lingual
cortical plates, and so on.

Review of Literature
1. Siu AS, Li TK, Chu FC, Comfort MB, Chow TW
( 2003)
A new contrast medium, Lipiodol ethiodized oil
(Laboratoire Guerbet, Paris, France), can easily be
mixed with the monomer of autopolymerizing acrylic
resin. The resultant acrylic template has several
advantages. the radiopaque template is optically
transparent (with a slight yellow tint), which
facilitates good visibility of surgical sites when the
template is modified to become the surgical guide for
implant placement. Implant Dent. 2003;12(1):35-40.

2. Kopp KC, Koslow AH, Abdo OS.( 2003)
The technique described facilitates precise dental
implant placement. A barium-coated template with
external guide wires used in conjunction with a
computed tomography scan and interactive software
may provide superior presurgical diagnostics,
treatment planning, and prosthetically directed
implant placement. Measurements predetermined on
the computed tomography scan can be transferred
accurately to the diagnostic/surgical template by use of
a precision milled cylinder placed into the template at
the proper angulation and linear dimensions. The
diagnostic/surgical template shows the surgeon the
optimal position for implant placement, thus

establishing greater clinical confidence when placing
implants. (Predictable implant placement with a
diagnostic/surgical template and advanced
radiographic imaging.) J Prosthet Dent. 2003
Jun;89(6):611-5.

3. Dov Along et al (2001) described fabrication of
imaging and surgical guides for dental implants. They
concluded that the circumference guide only traces the
outline of the planned prosthesis; it does not provide
necessary transposition of prosthetic and/ or bone
angulation information. The vertical lead strip and
gutta-percha guides serve primarily as imaging
indicators and allow for some surgical latitude in
preparation of osteotomy sites. The metal sleeve guide
used in conjunction with a set up disk appears to be
the most accurate imaging and surgical guide. It
serves as an imaging and a precision surgical
osteotomy guide, ensuring consistency between the

planned prosthetic angulation (confirmed by
diagnostic imaging) and the trajectory of osteotomy
during the surgical phase. JPD 2001:85:504-508.
4. Aryatawong S, Aryatawong K. (2000). The aim of
their study was to evaluate the possibility of locating
the inferior alveolar canal (IAC) before mandibular
posterior osteotomy or implant surgery using a
computer-controlled hypocycloidal tomographic
system. The visibility of the IAC was graded as
excellent or good in 74% and fair in 11.7% of the
sites. In 14.3% of cases, the canal was graded as
invisible. Conventional hypocycloidal tomography
has been shown to be a useful radiographic technique
for preoperative assessment of the IAC in thewww.indiandentalacademy.com

posterior mandible. (Evaluation of the inferior
alveolar canal by cross-sectional hypocycloidal
tomography.). Implant Dent. 2000;9(4):339-45.
5. Cehreli MC, Aslan Y, Sahin S. (2000). In this
article, the fabrication of a bilaminar dual-purpose
stent that facilitates ease in implant placement with
improved verification of implant positioning is
described. The outer lamina is designed for use in
the computed tomography evaluation, using
radiopaque markers. The verification of implant
alignment and positioning, according to the
determined prosthesis, is also performed with this
template after modifying it for surgery. The inner
lamina is designed to accept 2 removable surgicalwww.indiandentalacademy.com

acrylic resin stents with different guide channels that
avoids the risk of surgical malpractice. J Prosthet Dent.
2000 Jul;84(1):55-8.
6. Dov M. Almog, Rodolfo Sanchez. (1999) evaluated
correlation between planned prosthetic and residual
bone trajectories in dental implants. They used
tomographic survey in conjunction with imaging
guides. They found that the discrepancies between the
planned prosthetic and the residual bone trajectories
were greater in the mandibular molar area. J Prosthet
Dent 1999: 81:5: 562.

7. Cem Devge et al (1997). Studied magnetic
resonance imaging in patients with dental implants.
They concluded that a patient with intra oral or extra
oral Branemark implants may be exposed to an MRI
examination without any risk. The resulting artifacts
are minor. If the patient has any fixation magnets or
magnet keepers attached to the implants or the
prosthesis for its retention, these should be
temporarily removed not only to avoid major
artifacts, but also to eliminate the risk of implant loss.
IJOMI 1997: 12:3:354-359

8. Gray CF, Redpath TW, Smith FW (1996). Unlike
computerized tomography (CT) and other x-
radiographic techniques, MRI uses no ionizing
radiation, and is capable of angulating and offsetting its
scan plane at will. Good bone detail is available because
cancellous bone yields a strong signal from the marrow
fat, while cortical bone and dental enamel are dark. The
excellent anatomic detail provided by thin-slice high-
resolution MRI allows for assessment of the suitability
of sites to receive an implant in terms of bone quality
and thickness, and the relative position of the site to
important structures such as the inferior dental nerve
and nasal sinuses. J Oral Implantol. 1996;22(2):147-53.

9. Takeshita F, Suetsugu T (1996). This article
describes a method of fabricating a template with a
stainless steel tube sprue for accurate radiographic
evaluation and implant placement. Stainless steel tube
sprues are inexpensive, indicate the eventual implant
inclination, and facilitate precise placement, from the
CT scan without any interference from scattered
radiation. J Prosthet Dent. 1996 Dec;76(6):590-1.

10. Lam E.W Reprecht and Yang (1995).
Panoramic radiography and 2-D orthoradially
reformatted CT images were used to measure bone
height in the mandible and maxillae of patients
undergoing preoperative assessments for dental
implant placement. The greatest differences
between the two techniques occurred in instances in
which the use of dental implants would be
particularly advantageous, that is in regions with
less than 15 mm of remaining bone. JPD
1995:74:42-46.

11. Basten CH. ( 1995)
The computer tomogram prepared with the aid of
the radiopaque template allows the evaluation of the
implant sites in relation to the outline of the planned
restoration. The radiographic template is converted
into the surgical template, which contains
information regarding the optimal position and
angulation of implants. Because the surgical template
is a modification of the radiographic template, which
rests rigidly on the teeth during all procedures,
implant placement is more predictable. Quintessence
Int. 1995 Sep;26(9):609-12.

12.TanKB.(1995). Besides the basic clinical examination
and the use of mounted study models, radiographic
imaging is an essential adjunctive aid in treatment
planning. The latest imaging modality, multiplanar
reformatted CT (MPR-CT) is the most comprehensive
and accurate presently available. It allows precise
assessment of the three-dimensional architecture and
internal anatomy of the jaws. This enables accurate
preoperative evaluation for planning implant fixture
placement with maximal use of bone. The use of
radiographic stents (with radiographic markers
incorporated) derived from diagnostic wax-ups or set-
ups is essential. This provides reference points to
determine the available bone at the exact spatial
location and orientation of the planned implant fixturewww.indiandentalacademy.com

at all primary and alternate sites. The same
radiographic stent is then converted to a surgical guide
stent for precise location of surgical implant sites. Ann
Acad Med Singapore. 1995 Jan;24(1):68-75.
13. Ludlow JB, Nason RH Jr, Hutchens LH Jr,
Moriarty J. (1995). This study evaluated the diagnostic
accuracy of periapical, tomographic, and cross-
sectional occlusal radiographic techniques in the
assessment of facial and lingual bone loss at implant
obscured sites. Cross-sectional occlusal views provided
significantly greater mean observer confidence scores
than either periapical images or tomograms (P < .01).
However, tomograms may provide greater utility in
actual clinicalpractice. Implant Dent. 1995
Spring;4(1):13-8.

14. Siddiqui AA, Caudill R, Beatty K. (1995)
A technique for the measurement of bone loss around
endosseous implants using an optical comparator was
investigated. The bone loss around the implant was
calculated by taking the average of the mesial and
distal measurements. Statistical analysis at the 95
percent confidence level demonstrated that there was
no significant difference among the measurements.
Although the initial results are encouraging, additional
research is necessary with a larger sample size to
validate theaccuracy of optical comparator readings
and compare the efficacy of this technique with other
currently used methods for determining bone loss
around root form implants. Implant Dent. 1995
Summer;4(2):85-8. www.indiandentalacademy.com

15. Lawrence A Weinberg (1993). In his article, “CT
scan as a radiologic data base for optimum implant
orientation” concluded that optimum orientation is
aided by the three-dimensional radiologic database
provided by a CT scan. JPD 1993: 69: 381-385
16. Modica, et al (1991) described an original prosthetic
planning involving CT scan. They summarized that the
use of the CT scan as a diagnostic aid provides a three
dimensional study of the bone and a specially developed
positioner device estimates the position, angulation and
depth of the fixtures to be implanted. J Prosthet dent.
1991:65:541-546

17. Michael J. Engelman et al (1988). The average
surface dose of a tomographic exposure is 1 to 6 m
rad or 50 m rads per tomographic examination. This
is less than the exposure of a normal full mouth
radiographic survey. A CT scan has a radiation
exposure of two rads per slice or many times the dose
of a conventional tomographic examination. The
tomogram provides a more accurate image of the
quantity and quality of the osseous structures.
Through careful planning and systematic control, the
predictable placement of osseointegrated implants
can be achieved. J Prosthet dent 1988:59:4:467-473.

18. Ramuald J. Fernadez et al (1987) evaluated a
cephalometric tomographic technique to visualize
the buccolingual and vertical dimensions of the
mandible. The results of this study demonstrate
the following,
a. A uniquely designed cephalostat in conjunction
with an intra oral section indicating jig may be
used to visualize and measure true buccolingual
and vertical dimensions of an edentulous mandible.
b. Images of similar bone regions or sections were
proved to be reproducible with accuracy not
obtainable by other radiographic techniques. JPD
1987:58:466-470

19. Harold P. Truitt et al (1986). Studied the
feasibility of the use of computerized tomographic
scanner data in solid modeling of a specimen of
dry human skull. They concluded that it is highly
accurate and usable three-dimensional database
for use in solid modeling. J. Prosthet Dent.
1986:44:494-7.

References
1. Contemporary implant dentistry. Carl E Misch.
Second edition.
2. Atlas of dental and maxillofacial radiology and
imaging. Roger M Brown, Hugh D Edmondson, P
G John Rout. 1995.
3. Current oral and maxillofacial imaging. Razmus,
Williamson. 1996.
4. Essentials of dental radiography and radiology.
Eric Whaites. Third edition. 2002. Michael J.
Engelman et al. Optimum placement of
osseointegrated implants. J Prosthet dent
1988:59:4:467-473.www.indiandentalacademy.com

5. Harold P. Truitt et al. Non invasive technique for
mandibular subperiosteal implant. A preliminary
report. J Prosthet Dent. 1986:44:494-7.
6. Ramuald J. Fernadez et al. A cephalometric
tomographic technique to visualize the
buccolingual and vertical dimensions of the
mandible. J Prosthet Dent 1987:58:466-470
7. Cem Devge et al. Magnetic resonance imaging in
patients with dental implants. A clinical report.
IJOMI 1997: 12:3:354-359

8. Lam E.W Reprecht and Yang. Comparison of two
dimensional orthoradially reformatted computed
tomography and panoramic radiography for dental
implant treatment planning. J Prosthet Dent
1995:74:42-46.
9. Lawrence A Weinberg. CT scan as a radiologic data
base for optimum implant orientation. J Prosthet
Dent 1993: 69: 381-385 Dov M
10. Almog, Rodolfo Sanchez. Correlation between
planned prosthetic andresidual bone trajectories in
dental implants. J Prosthet Dent 1999: 81:5: 562.

11. Modica, et al. Radiologic prosthetic planning
of the surgical phase of the treatment of
edentulism by osseointegrated implants. An
invitro study. J Prosthet Dent 1991:65:541-546
12. Dov Along et al. Fabrication of imaging and
surgical guides for dental implants. J Prosthet
Dent 2001:85:504-508.
13. Kopp KC, Koslow AH, Abdo OS. Predictable
implant placement with a diagnostic/surgical
template and advanced radiographic imaging.)
J Prosthet Dent. 2003 Jun;89(6):611-5.

14. Siu AS, Li TK, Chu FC, Comfort MB, Chow TW.
The use of lipiodol in spiral tomography for dental
implant imaging. Implant Dent. 2003;12(1):35-40.
15. Basten CH. The use of radiopaque templates for
predictable implant placement. Quintessence Int. 1995
Sep;26(9):609-12
16. Aryatawong S, Aryatawong K. Evaluation of the
inferior alveolar canal by cross-sectional hypocycloidal
tomography. Implant Dent. 2000;9(4):339-45.
17. Tan KB. The use of multiplanar reformatted
computerised tomography in the surgical-
prosthodontic planning of implant placement.) Ann
Acad Med Singapore. 1995 Jan;24(1):68-75.www.indiandentalacademy.com

18. Siddiqui AA, Caudill R, Beatty K. Use of an
optical comparator for radiographic measurement
of bone loss around endosseous implants: a pilot
study. Implant Dent. 1995 Summer;4(2):85-8.
19. Ludlow JB, Nason RH Jr, Hutchens LH Jr,
Moriarty J. Radiographic evaluation of alveolar
crest obscured by dental implants. Implant Dent.
1995 Spring;4(1):13-8.
20. Gray CF, Redpath TW, Smith FW. Pre-surgical
dental implant assessment by magnetic resonance
imaging. J Oral Implantol. 1996;22(2):147-53.

21. Takeshita F, Suetsugu T. Accurate presurgical
determination for implant placement by using
computerized tomography scan. J Prosthet Dent.
1996 Dec;76(6):590-1.
22. Cehreli MC, Aslan Y, Sahin S. Bilaminar dual-
purpose stent for placement of dental implants. J
Prosthet Dent. 2000 Jul;84(1):55-8.

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