Implant radiology uses imaging techniques

Implant radiology
Dr Akshay Sujith
JR II OMR

Contents
Introduction
Ideal requirements
Periapical Imaging
Occlusal Radiographs
Panoramic Radiographs
CT Imaging
CBCT and Reformatted Images
Pre Treatment Evaluation
Post Treatment Evaluation
Parts of an implant
Implant Systems
Radiographic signs associated with failing endosseous implant

INTRODUCTION
• The success of implant surgery and restoration relies mostly on diagnostic
imaging. This technology contributes to all stages of implant treatment, from
presurgical site evaluation to postoperative assessment of integration, and long-
term periodic evaluation of implant status.
• Various imaging modalities have been used for dental implant assessment in the
different stages of implant treatment. These include intraoral radiography ( film-
based and digital), panoramic radiography, computed tomography (CT), cone-
beam computed tomography (CBCT), and others. Selection of the specific
imaging technique should be based on its suitability for providing the diagnostic
information required by the implant team (dentist, surgeon, radiologist) at
different stages of treatment.

Ideal imaging requirements of dental
implants
• Ability to visualise the implant site in mesiodistal,faciolingual,and
superoinferior dimensions.
• Ability to allow reliable and accurate measurements
• Ability to evaluate trabecular bone density and cortical bone thickness
• Ability to correlalate the image site with the clinical site
• Reasonable access and cost
• Minimum Radiation risk.

INTRA ORAL IMAGING
Periapical radiographs
Occlusal Radiographs
conventional
Digital
Techniques
Bisecting angle
Paralleling

Periapical radiography -Uses
• Periapical radiography produces a high-
resolution planar image of a limited region
of the jaws.
• Periapical Radiographs are commonly used
to evaluate the status of adjacent tooth and
remaining alveolar bone in the mesiodistal
dimension
• They also helps to determine the vertical
bone height, bone quality by determining the
amount of the trabecular bone pattern

Limitations
• periapical radiography to be of limited value in determining bone quantity
because of the magnification.
• The imaging field with periapical radiography is restricted and its
reproducibility is limited.
• Moreover, this modality is of no value in depicting the buccolingual width
of the edentulous ridge.

• Periapical radiography is more often used for single-tooth implants in
areas of abundant bone height and width.
• The use of periapical radiographs in the edentulous patients is limited
• Because of the variation in morphology of the residual edentulous
ridge ,the ridge may not have same long axis as tooth. The position of
image receptor may not display the accurate bone height as a result of
image foreshortening or elongation.

Occlusal Radiographs
• Intra oral mandibular occlusal radiographs depicts the maximal
buccolingual width but not the residual alveolar ridge

Panoramic Imaging
• The panoramic radiographic image is a curved slice of the maxilla and
mandible of variable thickness, generated by a rotating x-ray source.
• Because of the specific image production principles, panoramic
radiographs suffer from variable magnification, which is not the same in
the vertical and horizontal planes.
• Equalization of the vertical and horizontal magnification is achieved only
for a limited zone that lies within a curved plane called the central plain of
the image layer or the focal trough.

Uses
• Panoramic radiography is a useful technique to evaluate the alveolar bone,
the remaining teeth, and the location of neighbouring anatomic structures
(mandibular canal, maxillary sinus, nasal fossa) and to rule out the presence
of other osseous pathology.
• Panoramic radiographs are useful for the preliminary evaluation of the
crestal bone height, bone quality and density, and cortical boundaries of the
mandibular canal, maxillary sinus, and nasal fossa, provided that no
positioning errors have occurred.
• Panoramic radiography is, however, a fast, convenient, and readily
available imaging modality.

Limitations
• The panoramic radiograph is a 2-dimensional (2-D) image of 3-
dimensional (3-D) structures. Consequently, it does not demonstrate the
buccal-lingual dimension of the maxillofacial structures, and therefore, it
is inadequate for estimation of bone width. Moreover, it is a flattened,
spread-out image of curved structures, resulting in considerable distortion
of the structures and their relationship in space.
• Panoramic radiography has a variable magnification that ranges from 10%
to 30 %. Sometimes, this varies in different areas within the same
panoramic image. Also, image magnification is more variable when
positioning errors are encountered.

• Because of its popularity, clinicians have developed a means to
compensate for recognized shortcomings and to correct for errors.
Diagnostic splints incorporating metal markers with known dimensions
enable the clinician to determine the magnification in the area of interest

CT SCAN
• The CT scanner consists of a radiographic tube emitting a finely
collimated beam directed to a series of scintillation detectors or ionizing
chambers. The information collected by the detectors represents a
composite of the absorption characteristics of all tissues and structures in
the path of the x-rays.
• This information is transferred to the CT machine in which the data of the
multiple projections are transformed into an image. The CT image is
displayed as a matrix of individual blocks called voxels (volume
elements), whereas the square of the image that represents each block on
the screen is called a pixel (picture element).

• Each voxel and consequently the pixel by which it is displayed are
characterized by a numerical value that reflects its x-ray attenuation
features, which is mainly affected by the density of the tissue and its
thickness (dimensions of the voxel). This is called the CT number. The
computer assigns a specific shade of gray or density value to each CT
number using a matrix of gray shades, which comprise the image

Uses
• The primary advantage of CT is complete elimination of shadows of
structures lying deep or superficial to the structures of interest. Moreover,
because of its high-contrast resolution, CT can distinguish between tissues
that differ by less than 1% in physical density.
• The density values of structures in the CT image are absolute and
quantitative and can be used to differentiate tissues and characterize bone
quality

• The stored data can be realigned to create images based on the diagnostic
needs of the operator. This is called multiplanar imaging and allows the
structures of interest to be viewed in different planes, depending on the
specific diagnostic needs.
• CT can provide images with a 3-D perspective by using information
derived from axial images of the structures of interest.

Limitations
• Although CT has the potential to provide the required information with
remarkable accuracy; however, it was only rarely used in dental medicine.
Moreover, radiation exposure is fairly high, especially with older CT
technology. The gap between traditional dental imaging modalities and CT
was bridged with the introduction of CBCT.

CONE BEAM CT & REFORMATTED IMAGES
• CBCT uses a rotating x-ray source that generates a conically shaped beam,
the width of which can be modified to fit variable-sized imaging volumes
ranging from one-half of a dental arch to the entire head.
• The attenuated x-ray energy is acquired by a single detector with only one
revolution around the patient’s head (in most CBCT systems).
• The primary difference between CT and CBCT in terms of the acquisition
process is that the imaging data are acquired from the entire volume at
once (one revolution) in CBCT, instead of stacks of slices (multiple
revolutions) as occurs in CT.

CONE BEAM CT & REFORMATTED IMAGES
• CBCT images are acquired with initial scout images followed by single
revolution imaging sequence. The vertical height of the imaging can be
adjusted to include only one jaw or both jaw or a larger area if TM joints
need to be included.
• Some author suggest a higher field of view if the maxillary sinus should be
included.
• The minimum voxel size required for the implant planning purpose is 0.3-
0.4 mm.

The reformatted image will result in three
basic image type:
• Axial image with computer generated super imposed curve of alveolar
bone
• Associated reformatted alveolar cross sectional image
• Panoramic like (pseudo panoramic or curved linear) images.
An axial image that includes the full contour of the jaw at level
corresponding to the dental root is typically considered as the reference
point of reformatting process

Uses
• CBCT allows for the reconstruction of various images in any plane, flat or
curved, by selectively realigning the imaging data ( voxels ). This property
is linked directly to the fundamentals of CBCT data acquisition, which can
be considered volumetric.
• The standard display mode is planar imaging (sequences of slices in
different planes, axial, coronal, and sagittal, throughout the volume). If the
user desires a panoramic image from the volumetric data, this can be
accomplished by carefully selecting (with a cursor) an uninterrupted
sequence of voxels along a curved plane in the maxilla or mandible

• CBCT technology allowed interactive diagnosis, because the operator
could now control the retrieval of diagnostic information. This has
promoted interactive diagnosis, whereby the user can access much more
information about each patient.
• CBCT images helps to locate the undercuts trace the nerve canals and
foraminas and relationship with the maxillary sinus and other anatomical
structures

Pre-treatment evaluation
• CBCT images will allow parallel orientation of adjacent several implants
• It can also give the angulation at which the implant is placed.
hence it also helps in the proper abutment selection.
• Three dimensional representation of image will shows the distance from
existing natural teeth and the relationship of implant site with respect to
the both jaws and hence preventing any trauma to the adjacent teeth
• The clinicians can construct radiopaque radiographic guides which can be
placed at desired position to the final restoration

• The anatomical complexity of the maxillofacial structure makes
visualisation more complex due to their spatial orientation in such cases
diagnosis and planning may be benefited from segmentation.
• With segmentation, data representing certain structures in an imaging
volume may be isolated or removed from the volume, and this may
simplify anatomic relationships and reveal diagnostic information that was
obscured before removal.

• The segmented data can later be added back to the initial 3-D volume. In
this way, the mandibular bone, if segmented, can be removed from its
articulation with the temporal bone, to provide visualization of the glenoid
fossa.
• Similarly, certain teeth, if segmented, can be removed from the jaw and
illustrated with a different color or rendered transparent to assess the
relationship with neighboring structures. Segmentation is labor-intensive
and time consuming, requiring an advanced level of knowledge of the
application

• The data from planned implant cases can be used for the construction of
CAD-CAM surgical guides.
• This guide can be used during surgery to replicate the computer-planned
procedure, avoiding anatomic structures and allowing for precise implant
placement.
• Some of these proprietary software programs have advanced to the next
step, in which provisional and final restorations are fabricated from the
implant positions planned during presurgical workup

A surgical guide applied on a maxillary biomodel The metallic rings
accommodate the implant drills during implant surgery and orient them into
the exact location for the dental implants that were planned earlier during the
simulated placement. These guides could be either soft tissue-supported or
bone-supported.

• The accuracy of dental implant planning may be further increased with
currently experimental technologies, such as surface laser scanning data,
which would be combined with the CBCT data. This would provide
accurate information about the oral soft tissue (gingiva) in comparison to
CBCT data alone, which provides only hard-tissue information. This may
significantly increase the predictability of aesthetic implant-based
restorations.

POSTOPERATIVE DENTAL IMPLANT ASSESSMENT
• The factors that are primary determinants of implant surgery and the
clinical outcome of implant-retained restorations are associated with the
alveolar bone around the dental implant.
• The dental implant/bone interface (the contact of the dental implant to the
bone) and the alveolar bone height in relation to the neck of the dental
implant are crucial. A tight interface without the appearance of a thin
radiolucent rim surrounding the implant and fairly distinct alveolar bone
margins around the dental implant are signs of a successfully integrated
implant

• However, bone loss around existing dental implants does occur, and
literature has provided information regarding an acceptable rate of bone
loss over time.
• Although the bone loss on the proximal aspect of the dental implant can be
fairly assessed using peri apical radiographs , the bone loss in the
buccolingual aspect can only be measured in a three dimensional imaging.

Cropped panoramic radiograph, which was made for periodic evaluation of the maxillary
dental implants. Note the tight interface between the maxillary dental implants and the
alveolar bone that indicates a successful osseointegration

Implant Components
• Main Components
Fixture
Abutments
Superstructure
• Accessories
a) Surgical
cover screw
gingival Former
b) Prosthetic
Implant Analogue
Impression Srew

Implant Systems
• The ADA Council in 2004 provides a list of products available to the
profession that have received the ADA seal of acceptance. All ADA-
Accepted endosseous implants have demonstrated safety and efficacy
when used as indicated in fully and/or partiallyendentulous patients and/or
as single tooth implants. The type of prosthesis and anatomical location
used in evaluating Accepted Implants is identified in the Seal Statement

The Branemark implant system
• The implant consists of six components
1) The fixture
2) Cover screw
3) Abutment
4) Abutment screw
5) Gold cylinder and
6) Gold screw

• The fixture is the component which is surgically placed in to the jawbone
• The cover screw is screwed in to the top of the fixture to prevent down
growth of soft and hard tissue in to the internal, threaded area.
• The abutment is the Trans mucosal component which is connected using
an abutment screw in to the fixture.
• The gold cylinder, an integral part of the final prosthesis, is connected to
the abutment with the gold screw. The various components become a
single unit using the screws to connect them together.

David Gelb, 1 Bradley McAllister, Clinical and Radiographic Evaluation of Brånemark Implants with an Anodized Surface following Seven-to-
Eight Years of Functional Loading Int J Dent. 2013; 2013: 583567.

The Frialit– 2 System
• Developed by Prof. W. Schulte in 1974 at the University of Tuebingen. It
was the Frialit-1 or the Tuebingen implant. The basic concept of this was
the immediate replacement of a tooth after extraction with an implant. Dr.
Schulte believed this would prevent atrophy of the alveolar ridge.
• This system represents a further development of the Tuebingen immediate
implant which was originally designed to be used as a single tooth
replacement. However, Frialit -2 is made of pure titanium and is a two –
stage system in that it remains covered by the mucosal integument during
the healing in phase

• Frialit -2 system is available as a press-fit-cylinder or as a
selftapping step-screw with diameters of 3.8, 4.5, 5.5 and 6.5
mm, and in five different lengths (8, 11, 13 and 15 mm).
Design
Exterior Design It consists of 2 types of implants:
1. Stepped cylinder
2. Stepped screw.

Stepped Cylinder
• The implant body is shaped as a stepped cylinder. This shape
allows force transfer to be spread at various levels of the bone-
implant interface in horizontal as well as vertical direction. Axial
loads acting on the implant are distributed to the step plateaus
whereas lateral forces are dissipated to the enveloping surfaces

Stepped screw
• This was developed primarily for situation where greater demands
are placed on the initial stability due to poor bone quality or
insufficient congruency between the implant sites and the implant
as in immediate extraction cases. This is designed to be inserted
to the lower edge of the non-threaded section with finger
pressure. Only 3 full turns are then required to screw the full
length of the implant into the bone

The IMZ System
• The intramobile cylinder implant (IMZ) has been used clinically since
1974. The major difference between the IMZ system and all other relevant
implant systems is that an elastic compensating component is inserted
between the Osseointegrated implant and the prosthetic superstructure

• The IMZ implant consists of two parts
 The implant body
 Intramobile connector (IMC).
 The latter consists of titanium inserts and the intramobile element.

• The elastic intra mobile element assume the role of periodontal ligament
and helps in the distribution of the forces.
• The purpose of titanium insert is to lengthen the implant beyond the
gingiva after uncovering. Titanium inserts of 2 and 4 mm length are
available for use with mucosa of varying thickness. Thus, the position of
the intramobile element is always supragingival.

• The implant is a cylinder with a half-spherical apex, rounded shape is
intended to avoid stress peaks and overloading of the osseous bed in the
apical region. Perforations through the base of the implant permit the in
growth of bone in the apical region.
• IMZ implants are available in two different diameters (3.3 and 4.0mm) and
four different lengths (8, 10, 13,15mm).
• The elastic intramobile elements consist of a titanium core coated with
polyoxymethylene.

• The elastic component of the IMC is positioned in the conical orifice of
the titanium insert. The cone angle of the IMC is 15o
and permits up to 30°
of correction for implant that is not perfectly parallel. The centre of
rotation.

The TPS implant System
• The TPS screws are indicated solely for placement in the mandibular
symplysis, anterior to the region of mental foramina. The maximal bone
space required to house the TPS implant is 6.0mm horizontally and 9-10
mm vertically. It is not indicated in cases where there are insufficient bone
dimensions and where concomitant vestibuloplasty procedure is
performed. It was developed by institute Straumann, Waldenberg, a Swiss
International team for Implantology

• The use of 4 screws is indicated in this system so that distribution of the
functional load is performed in a physiological manner.
• The guidelines for this system indicate that the screws should engage the
inferior mandibular cortex without perforation of the inferior border. The 4
TPS screws are splinted together by means of a mesostructure.

ITI Dental Implant System
• The international team of implantologists (ITI) was established to develop
endosseous implant systems to satisfy a variety of needs and application
for the partially or totally edentulous patient.
• The ITI was developed as hollow system implant.The first hollow cylinder
implants in 1974, already features fenestrations in deliberately chosen
patterns. Bone grows through these perforations in the cylinder wall and
within a short time bridges the gap between the bone stub in the cylinder
lumen and the surrounding bone.

The Various ITI implant types
• Type HC (Hollow Cylinder)
The outer diameter of the Type HC implant is 3.5 mm. The anchorage surface is
coated according to ITI principles with plasma sprayed Ti. The perforations in the
cylinder stop about 4mm below the bone surface when the cylinder is implanted.
Primary stability, achieved by a slight positive press fit, promotes bony
incorporation, which leads to an excellence and permanent secondary stability.
The implant has a cylindric post, which is highly polished in order to reduce the
danger of plaque accumulation and to provide the most advantageous conditions
for epithelial attachment. The edges of the Type HC implant are rounded to
prevent local peak load induced bone resorption.

Type HS (Hollow Screw)
• This is a variant of the Type HC implant. It has the same form with
the addition of a spiral screws thread.

PME (Precision Margin Esthetics) Abutment
• It is used to elevate the abutment/ prosthesis interface from extremely
subgingival to minimally subgingival or even supragingival, depending on
the heights of the abutments used.
• The abutment is screwed directly into the implant body. The fit of the
abutment to the implant is checked with a periapical radiograph. The PME
abutment is internally threaded to receive an implant coping, a temporary
healing cap, or a coping series used to secure the prosthesis to the
abutment.ME abutments are available in 4 heights: 3, 4, 5, and 6 mm

• The PME abutment is designed to be used for full arch
restorations, screw-retained fixed bridgework and the tissue borne
for overdenture retention. This abutment accommodates up to 40
degrees of nonparallelism.

Post treatment prognostic criterias
• Earlier Concepts
Schnitman and schulman, 1979:
1.Mobility less than 1 mm in any direction.
2.Radiologically observed radiolucency graded but no success criterion defined.
3.Bone loss no greater than one third of the vertical height of the bone.
4.Gingival inflammation amenable to treatment, absence of symptoms and infection,
absence of damage to adjacent teeth, absence of parasthesia and anesthesia or
violation of the mandibular canal, maxillary sinus or floor of the nasal passage.
5.Functional service for 5 years in 75% of patients.

Cranin et al 1982:
• In place 60 months or more.
• Lack of significant evidence of cervical saucerisation on radiographs.
• Freedom from hemorrhage according to Muhleman′s index.
• Lack of mobility.
• Absence of pain or percussive tenderness.
• No pericervical granulomatosis or gingival hyperplasia.
• No evidence of a widening peri-implant space on radiograph.

• McKinney et al 1984:
Subjective criteria
• Adequate function
• Absence of discomfort
• Patient belief that esthetics and emotional and psychological attitudes
are improved.

Objective criteria
• Good occlusal balance and vertical dimension.
• Bone loss no greater than one third of the vertical height of the implant, absence of symptoms, and
functionally stable after 5 years.
• Gingival inflammation vulnerable to treatment.
• Mobility of less than 1 mm buccolingually, mesiodistally, and vertically.
• Absence of symptoms and infection associated with the dental implant.
• Absence of damage to adjacent tooth or teeth and their supporting structures.
• Absence of parasthesia or violation of mandibular canal, maxillary sinus, or floor of nasal passage.
• Healthy collagenous tissue without polymorphonuclear infiltration.

Radiographic signs associated with failing
endosseous implant
Sl.No Imaging appearence Clinical Impicatons
1 Radiolucent area that follows the entire implant Failure of Implant to integrate
with adjacent bone
2 Crestal bone loss around the coronal portion Ostitis resulting from poor
plaque control or adverse
loading
3 Apical migration of alveolar bone on one the side of
Implant
Non Axial Loading resulting
from improper angulation of
Implant
4 Widening of periodontal ligament space of nearest natural
tooth abutment
Poor stress distribution resulting
from biomechanically
inadequate prosthesis implant
system
5 Fracture of implant fixture Unfavourable stress distribution
during function

References
• White and pharaoh Text book of Oral Radiology 12th
edition.
• Christos Angelpoulous Imaging Technology in Implant
RadiologyDent Clin N Am 55 (2011) 141–158
• Dr. Unjum Bashir, Dr. Manas Gupta, Dr. Ravish Ahuja Implant
systems International Journal of Applied Dental Sciences 2016;
2(2): 35-41.
•

Implant radiology uses imaging techniques

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