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© Turkish Society of Radiology 2011
During the past four decades, dentistry has seen a dramatic expan-
sion and refinement of the technology used to identify dental
and intraosseous disorders. Intra-oral radiographs, including
periapical, bitewing and occlusal projections, are the basic (and often
the only) imaging technique required for most dental pathologies. Plain
film and panoramic radiography supply information about the teeth,
upper and lower jawbone, sinuses, and other hard tissues of the head
and neck. However, these techniques suffer from superimposition of all
of the structures that lie in the path between the X-ray source and the
film or detector.
Three-dimensional diagnostic imaging is certain to be the preferred
imaging method in future dentistry. Computed tomography (CT), origi-
nally designed for cranial imaging, has been used for evaluating orofa-
cial structures since its development. However, CT machines have limi-
tations for dentistry, including their high cost, large footprint and high
radiation exposure. Cone beam CT (CBCT) addresses these issues and
provides many dental advantages (1). Over the last decade, CBCT has
become available for maxillofacial radiographic imaging, and numerous
systems are now in use (2).
CBCT radiation doses vary substantially depending on the device,
field of view (FOV) and selected technique. The effective radiation
dose is many times higher than that of conventional panoramic radi-
ography, although it is less than the reported doses for conventional
CT. In a large-FOV CBCT scan, for example, patients are exposed to
a radiation dose equivalent to that of up to seven panoramic radiog-
raphy images, and they are exposed to the equivalent of up to 336
panoramic radiography images in a conventional maxillomandibular
CT scan (3).
CBCT technology allows a dental practitioner to evaluate patients for
a wide variety of maladies, including dental and jaw trauma and infec-
tions, edentulism (quantitative and qualitative osseous evaluation for
dental implants), temporomandibular joint (TMJ) osseous pathology,
impacted and supernumerary teeth, developmental and congenital jaw
deformities, dental endodontic lesions, and oral and maxillofacial pa-
thology (4). The main limitations of CBCT compared to conventional
CT are the lack of a soft tissue window, the lack of precise Hounsfield
units, and higher image noise (1). The flat panel detectors used in the
present study offered high spatial resolution and higher signal-to-noise
ratios than the image intensifiers in cone beam machines (5).
An incidental finding is one that is unrelated to the present illness and
is discovered unintentionally. The purpose of the present study was to
retrospectively determine the location, nature, and occurrence of inci-
dental findings in maxillofacial CBCT scans performed for maxillofacial
diagnostic purposes.
HEAD AND NECK IMAGING
ORIGINAL ARTICLE
Diagn Interv Radiol DOI 10.4261/1305-3825.DIR.4341-11.2
Incidental findings in the maxillofacial region detected by cone
beam CT
Fatma Çağlayan, Ümmühan Tozoğlu
From the Department of Oral Diagnosis and Radiology (F.Ç.
facagla@gmail.com), Atatürk University Faculty of Dentistry,
Erzurum, Turkey.
Received 28 February 2011; revision requested 30 May 2011; revision
received 29 June 2011; accepted 29 June 2011.
Published online 29 September 2011
DOI 10.4261/1305-3825.DIR.4341-11.2
PURPOSE
The purpose of this study was to determine the location, na-
ture, and occurrence of incidental maxillofacial findings on
cone beam computed tomography (CBCT) scans performed
for maxillofacial diagnostic purposes.
MATERIALS AND METHODS
CBCT images of 207 consecutive patients (129 females and
78 males) were examined. The sample consisted of 85 tem-
poromandibular joint (TMJ) disorder patients, 45 paranasal
sinusitis patients, 30 obstructive sleep apnea syndrome pa-
tients, 15 implant patients, and 32 others.
RESULTS
The overall rate of incidental findings was 92.8%. The high-
est rate of incidental findings was in the airway area (51.8%),
followed by impacted teeth (21.7%), TMJ findings (11.1%),
endodontic lesions (4.3%), condensing osteitis (1%), and oth-
ers (2.9%). The airway incidental findings included mucosal
thickening (21.3%), deviation of the nasal septum (12.6%),
conchal hypertrophy (11.1%), bullous concha (3.9%), and
retention cysts (2.9%). The impacted teeth consisted of third
molars (18.8%) and canines (2.9%). The incidental findings
for the TMJ patients were erosion of the condyle (4.8%), os-
teophytes (3.4%), and bifid condyle (2.9%).
CONCLUSION
Oral radiologists should be aware of possible incidental find-
ings and should be vigilant about comprehensively evaluating
possible underlying diseases.
Key words: • maxilla • cone beam computed tomography
• diagnosis
Çağlayan and Tozoğluii • Diagnostic and Interventional Radiology
(21.7%) (Fig. 2), TMJ findings (11.1%)
(Fig. 3), endodontic lesions (4.3%) (Fig.
4), condensing osteitis and idiopathic
osteosclerosis (1%), and others (2.9%).
The incidental findings in the air-
way area included mucosal thickness
(21.3%), deviation of the nasal septum
(12.6%), conchal hypertrophy (11.1%),
bullous concha (3.9%), and retention
cysts (2.9%). The impacted teeth con-
sisted of third molars (18.8%) and ca-
nines (2.9%). The incidental TMJ find-
ings consisted of erosion of the condyle
(4.8%), osteophytes (3.4%), and bifid
condyle (2.9%).
The most frequent incidental find-
ing in the TMJ patients was impacted
third molars (31.8% of the TMJ pa-
tients) (Table 3). In the paranasal si-
nusitis patients, the most frequent
incidental finding was erosion of the
condyles (17.8% of sinusitis patients)
(Table 4).
Materials and methods
The cone beam images were acquired
using a Newtom 3G (Quantitative
Radiology, Verona, Italy) Flat Panel-
based CBCT machine. To establish a
consistent orientation in the images,
the patient was placed in a horizontal
position such that the Frankfort hori-
zontal plane (the plane between the
highest point of the opening of the
external auditory canal and the low-
est point of the orbit) was perpendicu-
lar to the table, with the head within
the circular gantry housing the X-ray
tube. The X-ray tube detector system
performed a 360° rotation around the
head of the patient, with a scanning
time of 36 s. The scanner operated with
a maximum output of 110 KV and 15
mAs, a 0.16-mm voxel size and a typi-
cal exposure time of 5.4 s. The QR-NNT
software version 2.21 (Quantitative
Radiology) was used to analyze the im-
ages. After the raw data was acquired,
the patient left the examination room,
and the clinician performed the prima-
ry reconstruction to obtain axial slices
with a 0.5 mm thickness. A second-
ary reconstruction was subsequently
performed, and panoramic, sagittal,
coronal, and cross-sectional slices with
the required thickness and width were
obtained.
The CBCT images for 207 consecu-
tive patients (129 females and 78
males) were retrospectively examined.
The sample consisted of 85 TMJ disor-
der patients, 45 paranasal sinusitis pa-
tients, 30 obstructive sleep apnea syn-
drome patients, 15 implant patients,
and 32 others. The incidental findings
were classified as airway findings, im-
pacted teeth, TMJ findings, endodon-
tic lesions, condensing osteitis, and
idiopathic osteosclerosis. All of the in-
cidental findings were noted on forms
originally designed for this study. All
of the scans were independently re-
viewed by two oral and maxillofacial
radiologists with experience analyzing
>1000 CBCT scans. Any conflicts in the
reviews were resolved by consensus.
Results
A description of the subjects and their
indications for CBCT are reported in
Table 1, and the percentages of inciden-
tal findings are shown in Table 2. The
overall rate of incidental findings was
92.8%. The highest rate of incidental
findings was in the airway area (51.8%)
(Fig. 1), followed by impacted teeth
Table 1.
Description of the subjects and
their indications for cone beam CT (CBCT)
referral
Age (years) 30.29±13.80
(range, 9–74)
Gender (n)
Male 78
Female 129
Indication for CBCT (n)
Temporomandibular
joint disorders
85
Paranasal sinusitis 45
Obstructive sleep
apnea syndrome
30
Implant 15
Others 32
Total 207
Table 2.
The incidental findings in the
study population
%
Airway area 51.8
Mucosal thickness 31.3
Deviation of the nasal septum 12.6
Conchal hypertrophy 11.1
Bullous concha 3.9
Retention cysts 2.9
Impacted teeth 21.7
Third molars 18.8
Canines 2.9
Temporomandibular joint 11.1
Erosion of the condyle 4.8
Osteophytes 3.4
Bifid condyle 2.9
Endodontic lesions 4.3
Condensing osteitis 1
Other 2.9
Total 92.8
Table 3.
The incidental findings in the 85
temporomandibular joint patients
n (%)
Airway area
Mucosal thickness 22 (25.9)
Deviation of the nasal septum 12 (14.1)
Conchal hypertrophy 9 (10.6)
Bullous concha 7 (8.2)
Retention cyst 5 (5.9)
Impacted teeth
Third molars 27 (31.8)
Canines 2 (2.3)
Endodontic lesions 5 (5.9)
Condensing osteitis 0 (0)
Table 4.
The incidental findings in the 45
paranasal sinusitis patients
n (%)
Temporomandibular joint
Erosion of the condyle 8 (17.8)
Osteophytes 4 (8.8)
Bifid condyle 2 (4.4)
Impacted teeth
Third molars 4 (8.8)
Canines 0 (0)
Endodontic lesions 1 (2.2)
Condensing osteitis 0 (0)
Cone beam CT of maxillofacial region • iii
Figure 1. a–c. The airway findings in CBCT. Deviation of the nasal septum
and conchal hypertrophy from the coronal view (arrow, a). Mucosal
thickness and bullous concha from the coronal view (b). A retention cyst
from the axial view (arrow, c).
Figure 2. a, b. Impacted teeth from panoramic views in CBCT. The
arrows show an impacted canine (a) and a third molar (b).
b
b
a
a
c
Discussion
In this study, 192 patients (92%)
had incidental findings. The incidental
findings were most frequently seen in
the airway area, with mucosal thicken-
ing being the most common (31.3%).
The high frequency of airway find-
ings demonstrates that CBCT can be
an efficient tool for detecting airway
changes, such as mucosal thickness,
deviation of the nasal septum, conchal
hypertrophy, bullous concha and re-
tention cysts.
Many of the incidental findings in
the airway area have been previously
studied using 3D images (6–8). It has
been reported that the joint incidence
of nasal septal deviation and bullous
concha is high (44.6%) (8). In a re-
cent volumetric CT study, Smith et al.
(7) found that 19.4% of their patients
had a deviated septum, and 50.0% and
67.5% had mucosal thickening and
bullous concha, respectively, which
was consistent with maxillary sinusi-
tis. They also noted that 49.3% of
the patients with bullous concha also
displayed evidence of maxillary sinusi-
tis. Our mucosal thickness, deviated
septum, and bullous concha findings
were relatively lower than those in the
above-mentioned studies. However,
we only considered the incidental
findings. For example, we did not clas-
sify an airway finding as an incidental
finding in a CBCT scan of a paranasal
sinusitis patient.
In an another CBCT study, Cha et al.
(6) found an 18.8% incidence of air-
way findings. They found the follow-
ing distribution of airway findings in
orthodontic patients: sinusitis (7.5%),
retention cysts (3.5%), polyps (2.3%),
Çağlayan and Tozoğluiv • Diagnostic and Interventional Radiology
deviation of the nasal septum (0.4%),
and conchal hypertrophy (0.4%). Their
results are different from those of our
study, and this difference may have
resulted from differences in the study
populations. A mucous retention cyst
is a type of secretory cyst that it is rare-
ly seen in radiographs (9). The frequen-
cy of mucosal thickening and reten-
tion cysts can vary with odontogenic
factors (for the maxillary sinus), age,
gender, and allergies. In our study, we
found the frequency of incidental mu-
cous retention cysts to be 2.9%.
The presence of mucosal thickening
in the maxillary sinus always presup-
poses an irritation (9). Such irritation
can result from odontogenic factors,
trauma to the maxilla or the oral cavity
that penetrates the antrum and infec-
tions of the nasal conchae (10). Vallo et
al. (9) found the prevalence of mucosal
thickness in the maxillary sinuses to
be 12% in panoramic radiography. In
our study, however, the incidental fre-
quency of mucosal thickness in CBCT
was 31.3%. Thus, panoramic radiogra-
phy may not be as reliable a method for
diagnosing pathological dental or sinus
findings as 3D imaging techniques (11).
CBCT and CT provide 3D visualization
and prevent the superimposition of
anatomic structures and pathological
changes. Further, the quality of flat-
panel CBCT images of the paranasal
sinuses is related to the radiation dose
and scanning time (12).
Incidental findings in the TMJ re-
gion were equally prevalent and in-
cluded erosion of the condyles (4.8%),
osteophytes (3.4%), and bifid condyle
(2.9%). Crow et al. (13) found that in
panoramic radiography, there are no
differences in condylar morphology
between patients with and without TMJ
disorders. The prevalence of condylar
bone changes in orthognathic surgery
patients has been reported to be 55%
by transpharyngeal radiographs (14)
and 35.7% by CT (15). Our results were
comparatively lower, but our study had
a broader population and only includ-
ed incidental findings. Miloglu et al.
(16) found the frequency of bifid man-
dibular condyle in a Turkish patient
population to be 0.3% by panoramic
radiography. By contrast, we found the
frequency of bifid mandibular condyle
to be higher (2.9%). This difference
may have been due to the superiority of
CBCT for analyzing the TMJ region be-
cause of the absence of superimposition
of anatomical structures. In particular,
panoramic imaging and conventional
tomography may yield disappointing
results.
Figure 3. a–c. The
temporomandibular joint findings
in CBCT. The arrows show erosion
(a), osteophytes (b), and bifid
condyle (c).
Figure 4. a, b. The arrows show
endodontic lesions in CBCT.
Panoramic view (a) and cross-
section (b).
b
b
a
a
c
Cone beam CT of maxillofacial region • v
Failure of the eruption of permanent
teeth is a common dental anomaly.
CBCT allows a practitioner to view
teeth in three spatial planes (17).
Impacted teeth and their relation-
ships with other anatomical structures
can also be satisfactorily examined
in three dimensions by CBCT. Jena
et al. (18) investigated the distribu-
tion of individual tooth impaction in
Northern India general dental patients
by conventional radiography. They
noted that the frequency of at least
one impacted tooth (excluding third
molars) was 0.49% and that the most
frequently impacted teeth were the
maxillary canines (52.27%). Fardi et al.
(19) reported the incidence of impact-
ed teeth by panoramic radiography to
be 13.7%, with impacted maxillary ca-
nines being the most common, simi-
lar to Jena et al. (18). In our study, we
found a higher frequency of impacted
teeth than was found in the above-
mentioned studies. We included third
molars, however, and the frequency of
impacted third molars was quite high.
Imaging is an important clinical
aid for diagnosing endodontic bone
lesions. Cotti (20) has reported that
among the newest imaging modalities,
digital cone beam volumetric tomog-
raphy is becoming the new standard
and that real-time echo tomography
is attracting interest in diagnostic en-
dodontics. We found incidental endo-
dontic lesions by CBCT in 4.3% of the
subjects in our study, as compared to
1.8% in another study (6).
Condensing osteitis lesions (also
known as focal sclerosing osteomyeli-
tis) are radio-opaque formations that
are related to teeth with severe caries,
restoration or pulpitis. We found the
incidental frequency of condensing os-
teitis to be 1%. The frequency of con-
densing osteitis lesions in a Turkish pa-
tient population was previously found
to be 0.81% by panoramic radiography
(21), which is a similar result.
There have been only sporadic case
reports of lesions discovered inciden-
tally in adults or children. Asaumi et al.
(22) found incidental lesions by pano-
ramic radiography in 6.05% of pedi-
atric patients. In a 2007 study of 500
people who underwent a CBCT exami-
nation, the authors noted unexpected
incidental findings in 25% of the sam-
ple (6). Our incidental findings were
considerably higher because we in-
cluded all of the different types of inci-
dental maxillofacial findings (e.g., air-
way findings, TMJ findings, impacted
teeth, endodontic lesions, condensing
osteitis and other findings).
It should be noted that a dentist or
oral radiologist is not expected to treat
conditions outside of his or her profes-
sional expertise. However, he or she is
not absolved of the moral responsibili-
ty of identifying deviations in the com-
plete image. If an oral radiologist has
concerns, then he or she should refer
the patient to the relevant specialist.
In conclusion, oral radiologists
should be aware of these incidental
findings and comprehensively evaluate
the possibility of underlying diseases.
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