Download Cone beam computed tomography - Its applications

Journal of Advanced Clinical & Research Insights (2016), 3, 200–204
REVIEW ARTICLE
The third dimension of dentistry: Cone beam computed
tomography - Its applications
S. Swetha Kamakshi, Sanjana Tarani, Vathsala Naik, Smriti Devi Veera
Department of Oral Medicine and Radiology, Bangalore Institute of Dental Sciences and Research Centre, Bengaluru, Karnataka, India
Keywords
Cone beam computed tomography, future
of cone beam computed tomography, recent
digital imaging
Correspondence
Dr. S. Swetha Kamakshi, Department of Oral
Medicine and Radiology, Bangalore Institute
of Dental Sciences and Research Centre,
Hosur Road, Bangalore - 560 029, Karnataka,
India. E-mail: [email protected]
Abstract
Rapidly evolving advances in oral healthcare in the last 10 years has increased the
need for various novel diagnostic imaging modalities that aid in formulating the early
accurate diagnosis, and therefore, plan the treatment with the best prognostic value that
is achievable. Cone beam computed tomography (CBCT) is a radiographic imaging
technique that yields precise three-dimensional images of the maxillofacial region. For
more than a decade now CBCT has been used for dental and maxillofacial imaging and
its availability and use are increasing continuously. This has necessitated a review of the
various application of CBCT in dentistry.
Received 29 September 2016;
Revised 25 October 2016
doi: 10.15713/ins.jcri.138
Introduction
Radiology has played revolutionary role in diagnosis, treatment
plan, and prognostic value of various dental diseases ever since
the invention of X-rays in 1895.
Two-dimensional radiographs are the most commonly
employed techniques in dentistry. These radiographic techniques
suffer from magnification, distortions, superimpositions, and
misrepresentation of structures limiting its diagnostic accuracy.
To overcome these diagnostic challenges three-dimensional
(3D) radiographic techniques were incorporated after the
discovery in the year 1972 by Sir Godfrey N. Hounsfield of the
foremost commercial computed tomography (CT) scanner.
Nevertheless due to its soaring radiation exposure and cost
the use of CT in dentistry is limited. To combat these a newer
generation of CT was developed in 1982 called cone beam CT
(CBCT). The introduction of CBCT specifically dedicated
to imaging the maxillofacial region heralds a true paradigm
shift from 2D to an alternative 3D which compensates for the
shortcomings of other 3D imaging options.[1,2]
CBCT imaging employs shaped source of ionizing radiation
in the form of a divergent pyramidal or cone shape which is
directed through the central point of the area of interest onto
an area X-ray detector present on the opposite side. There is a
stationary fulcrum inside the region of interest around which
200
there is a rotating source of the X-rays and detectors that capture
the image. Multiple sequential planar projection images of about
600 frames raw data is obtained within a solitary complete rotation
from the desired field of view (FOV). Limited or small FOV units
of <10 cm size are appropriate for dentoalveolar imaging and are
largely beneficial for endodontic applications, diagnosis of cysts
and tumors. FOV’s ranging between 10 and 15 cm are termed
as medium FOV and are useful for imaging preimplant planning
and pathological conditions in maxillomandibular region. FOV
units range from 15 to 23 cm are called as large FOV which
are useful in the diagnosis of maxillofacial trauma, orthodontic
analysis, temporomandibular joint (TMJ) analysis and various
pathologies of the jaws.[3-5]
These specific clinical applications are discussed ahead in
detail.
CBCT in Implantology
Initial proof authenticates the capability of CBCT images
to illustrate preoperatively the quantity and quality of bone
available for placement of implant as well as to envisage the
boundaries of vital structures significant in surgical preparation
for dental implant planning for instance such as incisive canal,
mandibular canal, maxillary sinus, and mental foramen.
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Kamakshi, et al.
Applications of CBCT
The uses of this imaging modality in implantology are as
follows:
1. Aids in locating and determining the distance of implant to
vital anatomic structures
2. Measurement of alveolar bone thickness and appreciate bone
contours to decide if a bone graft or sinus lift is desired
3. To conclude the most appropriate implant size and type for a
particular patient
4. Identifies the ideal implant location and angulations.
The dental surgeon can approach all cases with the assurance
of being aware that the best existing image information and
technology have been used.[6]
CBCT provides cross-sectional images in various planes of
the alveolar bone height, width, and angulations. The science
of CBCT in implantology has additional protection, precision
and minimized errors. Further radiographic markers are
used by inserting it as a tool at the time of scan which serves
as a precise reference of the location of proposed implants.[7]
With the assistance of DICOM data the computer-generated
surgical guides (stereolithographic models) are being
fabricated from the CBCT image data to remove the work and
potential inaccuracy of impressions, conventional guide stents.
Using technology minimally invasive surgery is performed
without the need to raise a flap, thereby minimizing surgery
time, post-operative pain and swelling, and recovery time. The
dental laboratory uses the information stored in the surgical
template to fabricate presurgically a master cast and shortterm restoration that can be positioned instantly after surgery
(teeth-in-an-hour).[7,8] The use of computer-guided implant
surgery has wholly enhanced the dental implant team’s ability
to plan, place, and restore implants accurately with a level of
precision.[6]
amalgamated either with the proprietary software accompanying
the imaging device or with third party diagnostic software.[5,11]
Impactions
Calcification in Sinus
Cone beam scans afford more accurate 3D assessments to
provide predictable management results along with dropping
the risks associated with removal of impacted tooth. The site
and root configuration of impacted and unerupted teeth can be
visualized with incomparable precision. The periapical lesions
extent, site, regions of bone destruction, and accurate assessment
of the involvement of maxillary sinus are all distinctly defined.
Even the “spots” seen on conventional radiography can be
pinpointed, eliminating the intricacy of artifact and allowing the
dentist to provide patients state-of-the-art diagnosis.[1,9,10] The
accurate assessment of the spot and the relation of the inferior
alveolar canal to the roots of mandibular third molar may reduce
the injuries to nerve in extraction of impacted third molar and
during implant placement which avoids the everlasting loss of
sensation to the lower lip. Although conventional panoramic
imaging is possibly sufficient when the third molar is clear of
the canal but it is advisable to employ 3D imaging approach in
cases of radiographic superimposition of the structures. This has
been achieved by CBCT at comparatively low radiation dose
CBCT may be appropriate for specific imaging tasks in the
circumstance of intraoperative and pre-operative low-dose
assessment of paranasal sinus anatomy, surgical outcomes.[16]
CBCT analysis provides us with volumetric data that can be
used to visualize the complete airway path from both the nasal
and oral entrances extending up to the laryngeal spaces for:[12,16,17]
1. Precise recognition of anatomical borders
2. Analysis of level of infection and existence of polyps
3. Assistance in airway studies for analysis and management of
obstructive sleep apnea
4. Airway space assessment along with determining the actual
volume
5. Bird’s eye view of the point of airway constriction.
Craniofacial Fractures
Imaging of craniofacial fractures is a coherent application for
CBCT. It is used to distinguish mandibular condylar fracture,
fractures of the root of the teeth and the displacement of
anterior maxillary teeth. Several additional reports have
adorned the low-dose high-resolution principle of CBCT
imaging in pre-operative depiction of mandibular and orbital
floor fractures.[10] In a study, the authors stated that although
CBCT can exhibit clearly the orbital content herniation, due
to its poorer contrast resolution it lacks the ability to build a
distinction among the tissue components of the herniated
materials.[12]
TMJ
Congenital/developmental malformations, malocclusion,
degenerative diseases, ankylosis, joint remodeling following
diskectomy can be assessed more precisely in CBCT. CBCT
in the recent past has been finding its place as a significant TMJ
imaging modality through various ongoing researches, although
introductory experiments have yet to transform into clinical
studies. In a study by Alexiou et al.,[13] the authors concluded that
CBCT accurately assess periarticular bony defects, flattenings,
osteophytes, and sclerotic changes.
Pathologic changes, such as osteophytes, condylar erosion,
fractures, ankylosis, dislocation, growth abnormalities (like
condylar hyperplasia), rheumatic disease, and degenerative joint
diseases are optimally viewed on CBCT.[13-15]
Cone Beam Computed Sialography of Sialoliths
The advantage of CBCT sialography over conventional
sialography is that 3D reconstruction can be performed and
then viewed from any direction and in any slice thickness,
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Kamakshi, et al.
and from which cross-sectional slices may be obtained in any
direction. In a study by Drage and Brown, the authors have
stated that CBCT has proven useful in demonstrating areas
of complex anatomy, such as the route of the submandibular
duct over the posterior free margin of the mylohyoid muscle,
the paths of the ducts to the deep pole of the parotid gland or
the route of the anterior parotid duct over the anterior margin
of masseter muscle.[18]
Orthodontics
CBCT offers a 3D image that can be used to aid in orthodontic
tooth movement in all three planes of space. CBCT provides
the display of position of impacted and supernumerary teeth
and their relationships to adjacent roots and other anatomic
structures facilitating planning of the subsequent movement.[12,17]
Structural and anatomic relationships can be visualized
accurately due to the cross-sectional imaging that omits image
overlay. The current criterion in orthodontics for imaging is still
conventional CT. CBCT imaging has in recent past been largely
explored in the field of orthodontics for evaluation of thickness
of bone on the palatal aspect, skeletal growth patterns, age
estimation by evaluating the dentition, upper airway assessment,
and visualization of impacted teeth.[5,12]
CBCT imaging allows a more widespread orthodontic
diagnosis and more correct treatment planning by:
1. Position and anatomy of impacted teeth precisely in 3D
2. One is to one imaging for treatment planning and growth
assessments in orthognathic surgery cases
3. Airway assessments
4. Detailed planning for placement of orthodontic anchorage
and temporary anchorage devices (TADs)
5. Assessment of level of skeletal asymmetry.[19,20]
Miniscule details about the root resorption, available
bone width for the buccolingual movement of teeth, tooth
inclination and torque can be obtained. There are numerous
potential benefits to 3D cephalometry including accuracy of
linear measurements, visual demonstration of dentoskeletal
relationships and facial esthetics, and the potential for assessment
of growth and development are perhaps the greatest potential
benefits of CBCT in orthodontics.[21,22]
Endodontics
Periradicular surgical preparation, evaluation of periapical
pathology, categorization of internal and external root
resorption, and dentoalveolar trauma evaluation has all been
proven to be more accurate to analyze using CBCT. CBCT has
been proven to be finer to periapical radiographs in the depiction
of periapical lesions, signifying lesion immediacy to the maxillary
sinus, sinus membrane connection, and lesion location relative
to the mandibular canal.[12] However, CBCT has not proven its
efficacy to assess’ caries accurately.[23] van Daatselaar et al. have
stated that sensitivity increases with CBCT in detection of caries
but does not alter the specificity.[24,25]
202
Applications of CBCT
Periodontics
CBCT allows added precise evaluation of bone craters and
furcation involvements than digital intraoral radiography.
Kasaj and Willershausen have stated that these findings offer
perspectives for further studies in balancing radiation dose and
gather information for assessment of periodontal bone loss.[26]
Mengel et al.[27] compared the method of monitoring bone
loss using the conventional periodontal probe and bitewing
radiographs method with CBCT images. The authors concluded
that CBCT promises to be superior to 2D imaging for the
revelation of bone topography and lesion architecture but of
similar efficiency as that of 2D for bone height investigation.
Most of the CBCT software includes tools for evaluating and
monitoring bone density, which aid to assess the efficiency,
predict the results of treatment, and identify the prognosis of the
condition.[12]
3D Virtual Models and Rapid Prototyping
The prospect of fabricating individual 3D models which
clearly demonstrate the underlying skeletal pathology must
certainly be ranked as representing significant progress in the
planning of corrective maxillofacial surgery. Ongoing technical
developments have contributed to the fact that contemporary
surgery is computer assisted surgery, and such development
is likely to continue. User-friendly interfaces which shorten
operational procedures certainly improve the acceptance and
distribution of this techniques.[10]
In 2007, Kim et al. used CBCT data to replicate dental
models to manufacture drilling guides for orthodontic screws.[28]
In 2008 Periago et al. concluded that CBCT datasets would be
sufficiently accurate for clinical craniofacial analyses.[21]
Radiotherapy by CBCT
Image guided radiation therapy is in the recent past has been
stated to use CBCT for patient positioning during radiation
therapy.
With CBCT, a clear-cut repositioning of the patient to the
isocenter of the radiotherapy machine is obtained with a single
rotation immediately before delivering radiotherapy and is
further reconstructed in <2 min for treatment planning. Other
methods such as megavoltage (MV) imaging-based methods
which comprises MV CBCT and helical tomography have also
been researched religiously for verifying patient position before
radiotherapy treatment in comparison to the regular CBCT
equipment.[12,17]
CBCT in Forensic Odontology
CBCT is recently gaining importance in forensic dentistry. It
provides a good, noninvasive alternative to view the physiological
as well as the pathological changes of the pulpo-dentinal
complex in antemortem and postmortem scans.[29] The usage of
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Applications of CBCT
CBCT in forensic dentistry mainly lies in age estimation, which
is an integral part of forensic examination. There is high scope
of CBCT for victim identification and age estimation. CBCT
has also displayed its importance in skeletal age assessment,
especially when analyzing the cervical vertebra morphology. It
provides a 3D approach to the biologic aging of ortho patients,
by providing images of the cervical spine for age assessment.
Future Trends in CBCT
The future of CBCT is the enhanced CT scanner called as “ultra
CBCT scanners” which has evolved into novel machines. Ultra
CBCT imaging provides significant information concerning the
3D structure of vascular channels, nerve supply of the region
imaged, soft tissue and bone.[12] Conventional cone CT imaging
renders an 8-bit grayscale which yields 256 shades or 12-bit
grayscale that provides 4,096 shades, whereas the recent IMTEC
Imaging’s new ILUMA Ultra CBCT Scanner yields images in
14-bit grayscale, resulting in the shades of 16,384.[9,30]
The contrast-enhanced territories depicted by CBCT with
selective intra-arterial contrast agent administration were
employed to forecast allotment of microspheres. Such further
studies are required in the future for maxillofacial region.[9]
These machines can also additionally provide information
about tumor and tissue perfusion presently undetectable by digital
subtraction angiography or 99mTc macro aggregated albumin
imaging, which should optimize 90Y (yttrium-90) microsphere
delivery and reduce nontarget embolization.[9,30] Captivating the
lead in the growth of this technology is quantitative radiology,
the pioneers in invention of CBCT for maxillofacial imaging is
further researching in the same field.[2,9,30]
Conclusion
Since the time of its inception, CBCT imaging for the
maxillofacial region has provided a new arena for the application
of 3D imaging in all disciplines of dentistry as a diagnostic and
treatment planning tool.
CBCT today is capable of imaging hard-tissues and most of
the soft-tissue structures.
The amalgamation of a third dimension into practical dental
and craniofacial imaging has made this imaging modality an
exciting and intrigue imaging of choice. The paradigm has
shifted from landmarks, lines, and angles to flashing a volumetric
narration of surfaces, areas, and volumes.
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How to cite this article: Kamakshi SS, Tarani S, Naik V,
Veera SD. The third dimension of dentistry: Cone beam
computed tomography - Its applications. J Adv Clin Res Insights
2016;3:200-204.
Journal of Advanced Clinical & Research Insights ● Vol. 3:6 ● Nov-Dec 2016