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Dentomaxillofacial Radiology
Cone Beam Computed Tomography –
3D Imaging in Oral and Maxillofacial Surgery
a report by
B a s s a m H a s s a n 1 and R e i n h i l d e J a c o b s 2
1. Research Fellow, Department of Oral Radiology, Academic Centre for Dentistry, Amsterdam; 2. Head, Oral Imaging Centre, Catholic University of Leuven
Imaging plays an important role in oral and maxillofacial surgery diagnosis
reduction, lesser cost and increased availability. However, CBCT images
and treatment planning. A thorough history and clinical examination are
suffer from several artefacts due to inferior detector efficiency and beam
vital in establishing diagnosis; however, the value of radiographic imaging
inhomogeneity.13,14 The influence these artefacts have on image quality and
cannot be overstated. 2D projection radiography has been in use for more
diagnostic accuracy is variable among the different manufacturers with
than half a century for diagnosing congenital and developmental
respect to the different scanning and reconstruction settings. The objective
deformities in the maxillofacial region. Still, over the last few decades, the
of this article is to discuss some of the stated applications of CBCT compared
introduction of 3D imaging characterised by computed tomography (CT)
with conventional projection imaging and MDCT in oral and maxillofacial
and magnetic resonance imaging (MRI) technologies has had a tremendous
surgery, as reported in the literature.
impact on the practice and teaching of maxillofacial surgery. The
tomographic nature of CT and MRI provides thin slices at much higher
Tooth Impaction
inherent contrast than achievable with 2D projection radiography, which in
Surgical removal of impacted teeth demands precise knowledge of the
turn allows for a better delineation of the bone and soft-tissue boundaries
tooth location in the jaw and its relation to other teeth and surrounding
and a deeper appreciation of the intricate interrelations of the complex
anatomical structures. For instance, in the mandible the relationship of the
anatomy of the maxillofacial region.
roots of impacted third molars to the mandibular dental canal must be
accurately assessed since the canal is frequently very closely associated with
CT is used extensively in maxillofacial surgery for diagnosing osseous lesions
an impacted molar, and post-operative complications due to nerve
and deformities, pre-operative planning of surgical interventions, intra-
impingement are reported.15,16 It is necessary to assess whether a physical
operative surgical navigation and fabrication of surgical stents and
contact between the root and the border of the canal is present or not. In
implants.1–4 CT systems are largely accessible to surgeons residing in public
the maxilla, localisation of impacted canines relative to the lateral and central
and private hospitals in medical radiology departments, but for small private
incisors is central to their management. Information regarding the palatal
surgery clinics, dental hospitals and clinics, the installation, operating and
orientation of an impacted canine and its proximity to the root of the lateral
maintenance costs and labour of a conventional CT machine are prohibitive
incisor is vital to allow for an effective and timely surgical intervention.17,18
in most cases.5,6 In the last decade, a CT system specifically dedicated to the
Conventional panoramic radiographs are routinely obtained to evaluate
maxillofacial region has been developed and has become increasingly
tooth impaction pre-operatively. However, compared with CT, the 2D
popular. These so-called cone beam CT (CBCT) scanners capture the entire
nature of the image and the superimposition of adjacent anatomical
maxillofacial region by a single rotation of the X-ray tube and detector
structures impede precise assessment of the tooth relative to adjacent
around the patient’s head while providing sub-millimetre resolution.7–10
anatomical structures.19–21 CBCT orthographic tomographic slices and
There are several characteristic differences between CBCT and medical
panoramic reconstructions are superior to conventional panoramic
multidetector CT (MDCT) with respect to data acquisition and reconstruction
radiographs in determining the location and orientation of an impacted
method, image spatial resolution, contrast, artefacts and patient radiation
tooth and its relationship to adjacent vital structures in the maxilla and the
dose.11,12 CBCT is advantageous over MDCT in terms of radiation dose
mandible (see Figure 1).22–29
Bassam Hassan is a PhD candidate in the Department of Oral
Radiology of the Academic Centre for Dentistry (ACTA) in
Amsterdam. He has been involved in several projects related to
cone beam computed tomography 3D imaging in dental
radiology. He is also a part-time developer for the EU Simodont
project. Dr Hassan completed a Masters in medical imaging at
the Catholic University of Leuven.
Pathological Conditions
CBCT diagnostic applications in the maxillofacial region include evaluating
the presence of osseous defects in the jaws, cysts, lesions, calcifications,
teeth and bone traumas and fractures. CBCT is also playing an increasingly
important role in the detection of ‘incidental’ pathology in patients referred
for dental treatment. Since most currently available CBCT systems acquire
volumes that extend beyond the dentition and the surrounding alveolus,
Reinhilde Jacobs is Head of the Oral Imaging Centre at the
Catholic University of Leuven, a Full Professor at the School of
Dentistry, Oral Pathology and Maxillofacial Surgery of the
Catholic University of Leuven and a Visiting Professor at the
Dalian Medical University. She is European Director of the
International Association of DentoMaxilloFacial Radiology and
President-elect of the European Academy of DentoMaxilloFacial
Radiology (EADMFR).
E: [email protected]
unsuspected lesions in the paranasal sinuses, parotic region, masticatory
space, floor of the mouth and the hyoid region are frequently detected and
reported.30–36 Evidently, the 3D nature of CBCT allows determination of the
exact extension of the lesion in the affected region (see Figure 2).
Orthognathic Surgery
Several applications of CBCT in orthognathic surgery treatment simulation,
guidance and outcome assessment have been developed. CBCT 3D surface
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Cone Beam Computed Tomography – 3D Imaging in Oral and Maxillofacial Surgery
Figure 1: Third Molar Impaction
Figure 2: Lesion Detection with CBCT
Figure 3: Skeletal Visualisation
Visualisation of the intimate relation of the mandibular canal
and an impacted wisdom tooth, imaged with the Scanora 3D
(Soredex, Tuusula, Finland) and presented in the On-Demand
3D software (CyberMed, Seoul, South Korea). Courtesy of
R Jacobs and P Couto, Oral Imaging Centre, KU Leuven.
Folicular dentigerous cyst in the right mandible associated
with an impacted tooth, imaged with the Scanora 3D
(Soredex, Tuusula, Finland) and presented in the On-Demand
3D software (CyberMed, Seoul, South Korea). Courtesy of
R Jacobs and P Couto, Oral Imaging Centre, KU Leuven.
A patient with deviation in the face in the right side, imaged
with the NewTom 3G (QR SLR, Verona, Italy), presented with
Amira software (Visage Imaging, Carlsbad, California).
reconstructions of the jawbones are used for pre-operative surgical planning
amount and quality of available bone cannot be accurately assessed on a
and simulation in patients with traumas and skeletal malformations (see
panoramic radiograph. Therefore, medical CT is typically used to quantify
Figure 3).37–39 Coupled with dedicated software tools, simulations of virtual
the amount of bone present, but the young age of cleft patients makes the
re-positioning of the jaws, osteotomies, distraction osteogenesis and other
routine use of medical CT problematic due to the relatively high radiation
interventions can now be successfully implemented. Pre- and post-operative
dose involved. CBCT is rapidly replacing medical CT for this task since it
3D CBCT skull models can also be registered (i.e. superimposed on each
provides excellent 3D visualisation of the palate at the pre-maxilla region at
other) to assess the amount and position of alterations in the mandibular
a lower patient dose (see Figure 5).61 CBCT is used to determine dental age,
rami and condylar head following orthognathic surgery of the maxilla and
and when a large scan field of view (FoV) selection is present, 3D
the mandible.40,41 3D reconstructions of the jawbones from CBCT are of
reconstructions of the cervical vertebra can be made and employed to
sufficient quality for clinical work. However, 3D models of the dentition still
determine skeletal age.62 Additionally, CBCT has been used to show any
suffer from deformations due to streak artefacts caused by metal fillings,
deformities in the piriform margin in the nasal platform and the antero-
crowns and bridges, orthodontic brackets and other metallic dental
posterior depression of the nasal alar base.63 3D CBCT reconstructions of the
appliances.42 Therefore, virtual 3D models of the dentition are obtained by
skin surface of the face and nose for cleft lip assessment are also possible.
scanning the dental cast using a high-resolution surface laser scanner.
Custom-made inter-occlusal wafers can also be scanned separately and
Dental Implants and Bone Grafts
then combined with CBCT 3D reconstructions of the jaws to create
Imaging plays a crucial role in the pre-operative assessment of oral implant
composite skull models.43–46 These ‘double scanning’ techniques have been
placement. After a thorough clinical examination, imaging should be used
successfully applied to patients with jaw asymmetry and in severe
to evaluate bone quality and quantity, its morphology and relation to vital
malocclusion cases.47–49
anatomical structures such as the mandibular canal. Panoramic and intraoral radiographs are widely used in implant evaluation, yet the inherent 2D
Temporomandibular Joint Imaging
nature of those techniques hamper detailed pre-operative planning that
The temporomandibular joint (TMJ) is a complex entity with hard- and soft-
would allow to integrate all necessary parameters with respect to the
tissue components. TMJ disorders (TMDs) are common but widely variable.
anatomical restrictions, the required implant position and axis in relation
MRI has sustained its position as the gold standard imaging modality for
to anatomy, neurovascularisation, biomechanics and aesthetics.64,65
diagnosing TMDs since it provides excellent visibility of the disk and the
Moreover, the inherent distortion of panoramic radiographs makes those
associated joint muscles. Nonetheless, most TMJ examinations start with a
images less suited for reliable implant planning. The introduction of CBCT,
panoramic radiograph to visualise any gross changes in the condylar head
offering 3D imaging at relatively low dose and costs, has increased the
and temporal components. However, panoramic radiography has a low
applicability and strengthened the justification of cross-sectional pre-
diagnostic accuracy in detecting TMDs so a negative indicator on a
operative imaging. In addition, the convenience and easy access to CBCT
50–52
panoramic radiograph does not exclude the presence of osseous defect.
has drastically expanded its use.66 The benefits of 3D imaging in a virtual
CBCT parasagittal and coronal slices show crisp, clear images of the condylar
planning environment include improved integration of all information on
head and the glenoid fossa. CBCT is more accurate than panoramic
aesthetics, biomechanics and anatomy.64,65 In fact, the rapid escalation in
radiography and conventional tomography for detecting TMDs (see
the number of CBCT units installation is deemed to go hand in hand with
Figure 4).53–57 A CBCT exam was also recommended before image-guided
the steep increase in implant therapy. The latter holds especially true for
puncture operation of the superior compartment of the joint space.58
computer-aided implant planning applications, where implant placement
is first simulated then transferred to the operation site using either
Cleft Lip and Palate
navigation or surgical templates or so-called drill-guides (see Figure 6).67,68
In cleft lip and palate patients, information regarding the number and
This technique surely has advantages for more complicated surgery, such
orientation of teeth, dental and skeletal age and the amount and quality of
as planning grafting procedures.69,70 Indeed, the graft can currently be
available bone in the cleft region are considered vital for the clinical
virtually modelled such that the receptor bed is well prepared to precisely
management of such cases. Panoramic radiographs are often used to
fit to an a priori optimally shaped graft (see Figure 7). From the statements
investigate the incidence and number of missing teeth and to determine
above, it is obvious that CBCT is striving to become the method of choice
dental and skeletal age in cleft lip and palate patients.59,60 However, the
for pre-operative implant planning procedures.
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Dentomaxillofacial Radiology
Figure 4: Temporary Joint
Defects Imaging
Figure 5: Imaging of Cleft Palate with
Tooth Impaction
Figure 6: Pre-operative Virtual Implant
Planning
Patient with unilateral cleft palate with tooth impaction
imaged with the Scanora 3D (Soredex, Tuusula, Finland) and
presented in the On-Demand 3D software (CyberMed, Seoul,
South Korea). Courtesy of R Jacobs and P Couto, Oral Imaging
Centre, KU Leuven.
Example of preparing a radiographic template with gutta
percha cylinders to integrate the information on preferred
implant axis and implant position, biomechanics and aesthetics
with consideration for anatomical restrictions. The mandibular
nerve has been visualised (On-Demand 3D screenshot of
Scanora 3D data set) to allow interactive planning of implant
placement without hitting this canal. Courtesy of Filip Van de
Velde, Antwerp, Belgium.
Cone beam CT scan TMJ
protocol
Patient with flattening in the temporomandibular joint imaged
with the NewTom 3G CBCT (QR SLR, Verona, Italy) with the
12-inch scan field presented with Amira software (Visage
Imaging, Carlsbad, California).
Figure 7: Bone Graft Simulation
maxillofacial applications. However, when CBCT is compared with MDCT
technology, the situation is slightly different. As the latest generation of
MDCT scanners are progressively advancing towards ‘volumetric scan’
acquisition modes with 32-, 64- and 256-detector array arrangements and
more coupled with rapid scan time, sub-millimetre isotropic voxel size,
A patient with simulated bone graft in the right maxillary sinus prior to implant placement.
Courtesy of Materialise NV, Haasrode, Belgium.
superb tissue contrast and steadily decreasing radiation doses, it has become
increasingly more difficult to cite the proclaimed advantages of CBCT over
Discussion
latest-generation MDCT as self-evident. The two technologies are
The use of CBCT is expanding in dental and maxillofacial imaging. The
developing concurrently at a rapid pace with new systems appearing on the
multitude of 2D and 3D reconstructions possible with this imaging technique
market each year. However, this does not necessarily indicate that one
supplements the clinical decision with novel insight with respect to the
technology will triumph over the other in all clinical indications; rather, the
formation of the anatomy and the extent of pathosis. CBCT is evidently more
concomitant accumulation of clinical experience and evidence-based
advantageous than 2D projection radiographs in several important
research will appropriate the use of each modality to specific applications. ■
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