Dief S, Veitz-Keenan A, Amintavakoli N, McGowan R. A systematic review on incidental findings in cone beam computed tomography (CBCT) scans. Dentomaxillofac Radiol. 2019; 48 https://doi.org/10.1259/dmfr.20180396
Barghan S, Tahmasbi Arashlow M, Nair MK. Incidental findings on cone beam computed tomography studies outside of the maxillofacial skeleton. Int J Dent. 2016; 2016 https://doi.org/10.1155/2016/9196503
Togan B, Gander T, Lanzer M Incidence and frequency of nondental incidental findings on cone-beam computed tomography. J Craniomaxillofac Surg. 2016; 44:1373-1380 https://doi.org/10.1016/j.jcms.2016.06.026
Edwards R, Alsufyani N, Heo G, Flores-Mir C. The frequency and nature of incidental findings in large-field cone beam computed tomography scans of an orthodontic sample. Prog Orthod. 2014; 15 https://doi.org/10.1186/s40510-014-0037-x
Allareddy V, Vincent SD, Hellstein JW Incidental findings on cone beam computed tomography images. Int J Dent. 2012; 2012 https://doi.org/10.1155/2012/871532
Longoni S, Sartori M, Braun M Lingual vascular canals of the mandible: the risk of bleeding complications during implant procedures. Implant Dent. 2007; 16:131-138 https://doi.org/10.1097/ID.0b013e31805009d5
do Carmo Oliveira M, Tedesco TK Analysis of the frequency of visualization of morphological variations in anatomical bone features in the mandibular interforaminal region through cone-beam computed tomography. Surg Radiol Anat. 2018; 40:1119-1131 https://doi.org/10.1007/s00276-018-2040-2
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Do something or do nothing? anatomical variants and incidental findings on cone beam CT. part 1 Jimmy Makdissi Amanda Loughlin Mohammed M Dungarwalla Dental Update 2024 49:2, 707-709.
Authors
JimmyMakdissi
DDS, MMedSc, FDS RCS(Eng), DDRRCR, FHEA
Clinical Senior Lecturer and Honorary Consultant, Dental and Maxillofacial Radiology, Institute of Dentistry, Queen Mary University of London and Barts and The London School of Medicine and Dentistry, The Royal London Dental Hospital; Clinical Director, JM Radiology CBCT Training
Specialist in Oral Surgery, Institute of Dentistry, Barts and The London School of Medicine and Dentistry, Queen Mary University of London; Department of Oral and Maxillofacial Surgery, The Royal London Hospital
Cone beam computed tomography (CBCT) is a popular and often indispensable imaging modality used for the dento-alveolar tissues and immediate surrounding structures. It can be used across several dental disciplines including endodontics, implant planning, oral surgery and orthodontics. Furthermore, it is also commonly used in the medical specialities of oral and maxillofacial surgery (OMFS) and ear, nose and throat (ENT) surgery. In many of the images taken, there will often be findings/presentations that may not be expected, or familiar, to the reporting clinician.
CPD/Clinical Relevance: Many incidental findings are innocuous, yet their recognition and documentation are essential because some will warrant medical or surgical intervention.
Article
Jimmy Makdissi Amanda Loughlin Mohammed M Dungarwalla
Cone beam computed tomography (CBCT) is an indispensable imaging modality in dentistry and oral and maxillofacial surgery (OMFS) because of its ability to visualize the hard tissues of the maxillofacial skeleton in three dimensions (3D). It is also readily available in general dental practice, which has advanced the diagnostic and treatment capacity of the primary care practitioner. Further advantages include the fast scanning time and the ability to merge scans with implant planning and diagnostic software.
The main uses of dental CBCT can be divided into the planning of dental procedures (for example, where vital anatomical structures may be compromised in a surgical intervention), in planning complex endodontic treatment, or in the investigation of complications (for example, when a root has been displaced into the sinus or there is a persistent peri-apical radiolucency following endodontic treatment).
Although CBCT technology has been in use in Europe since 1996, its widespread use in dentistry is a more recent advancement. The introduction of a new imaging modality carries with it many concerns that must be addressed. Personnel who wish to use CBCT in their practice must be adequately trained to ensure the safety of patients and staff, and there must also be appropriate selection of cases, and maximum diagnostic yield from each study. Studies must be adequately interpreted to ensure any information acquired can be acted upon or taken into account in treatment planning.
Dental CBCT is not sufficiently covered in most undergraduate dentistry curricula at present, therefore, further training is required before the introduction of CBCT into a dentist's armamentarium.1
CBCT scans are categorized by their field of view (FOV) size: namely, small, medium and large. The Sedentex-CT guidance divides scans into small and medium (dentoalveolar) FOV that are smaller than 10 cm in height, and large (craniofacial) FOV that are greater than 10 cm in height.2 While dentists may undergo training in the interpretation of dento-alveolar FOV CBCT scans, it is important to recognize that even dentoalveolar volumes may cover tissues beyond the expertise of the dentist, such as the airway, maxillary sinuses and cervical spine.
Incidental findings (IFs) are any occult findings that are discovered upon assessing a radiographic image taken for other purposes.3 The larger the volume of tissue imaged, the higher the rate of IFs found on the volume. A systematic review of IFs on dental CBCT showed a frequency between 24.6 and 94.3%.4 Similarly, another study examining CBCT scans outside the maxillofacial skeleton found 653 incidental findings in 309 scans, over 31% of which required onward referral.5 Common extragnathic incidental findings were related to the paranasal sinuses,6 the airway,7 and calcifications within the pineal gland, carotid artery and tonsils.8
This pictorial series outlines and illustrates some of the anatomical variants and incidental findings found on CBCT scans. This is to help clinicians appreciate the need for appropriate volume size, correct patient positioning and access to a suitable reporting network should the need arise for a second opinion on CBCT imaging. The authors advise, whether discovery of the anatomical variants and incidental findings warrant intervention. The series is divided into two parts, one covering the dento-alveolar volumes and the immediate surrounding structures and the second part, in the following issue of Dental Update, illustrating the structures beyond the dentoalveolar volume. The findings and anatomical variants will be presented alphabetically.
Figure 1. Coronal view showing the left mental nerve emerging from two foramina (arrowed).Figure 2. 3D reconstruction showing superior and postero-inferior right mental foramina.
Category: anatomical variant.
Frequency: common.
Symptoms: none.
Appearance: radiolucent, rounded approximately 2–3 mm in diameter. They may be associated with expected/known foramina. A bony canal will be contiguous with the foramen.
Management: none. However, special attention must be noted in implant planning, particularly in the anterior mandible and lower premolar region because they may carry significant neurovascular supply to these regions.9,10
Additional root canals/variation in root canal morphology (Figures 3–5)
Figure 3. Axial views demonstrating two canals in the LR2, 1 and LL1 (each arrowed).Figure 4. Sagittal imaging demonstrating the division of a common canal into two canals to join once more (isthmus) at the apex.Figure 5. Axial view of the maxilla demonstrating two root canals in the mesiobuccal root of the UL6, UL7, UR6 and UR7. The second mesio-buccal canal (MB2) in the UL6 remains unfilled (arrowed). Both upper second premolars (UL5 and UR5) possess a buccal and palatal canal.
Category: anatomical variant.
Frequency: common, in one study of three-rooted maxillary molars, an additional canal was found in over 80% of teeth on CBCT.11
Symptoms: none unless associated with dens invaginatus, in which case symptoms of pulpitis and apical periodontitis may rapidly ensue.
Appearance: often found adjacent to anticipated root canal (eg MB2 in upper first permanent maxillary molar teeth).
Management: none. Of relevance in endodontic treatment of tooth.
Additional roots and unanticipated root morphology (Figures 6–9)
Figure 6.
(a) Panoramic imaging of the LR8 demonstrates seemingly ‘straight-forward’ root morphology, with partial loss of definition of the inferior dental canal. (b) Cone beam CT axial views demonstrating at least four roots on the LR8. (c) Sagittal imaging of the same tooth demonstrating extreme curvature of one of the buccal roots in an intimate relationship with the lingually placed and narrowed inferior dental canal.Figure 7. Sagittal view of the UR5 demonstrating extreme mesial curvature of the root in the apical third.Figure 8. Dens in dente (dens invaginatus) affecting the upper right canine (UR3) (arrowed). There is also an associated peri-apical radiolucency associated with the UR3 suggestive of periapical pathology.Figure 9. Concrescence affecting the upper left second molar (UR7) and upper right third molar (UR8) (arrowed). There is also significant thickening of the maxillary antrum.
Category: anatomical variant.
Frequency: common.
Symptoms: none.
Appearance: an addition to the expected number of roots and variation in their morphology.
Management: none. Of relevance to endodontic treatment and implant placement if the additional root is near the placement site. If the tooth is due for extraction, unanticipated root morphology should be assessed to allow treatment planning, then additional root apices must be accounted for on removal. In cases of concrescence (Figure 9), the patient should be warned of the loss of the other attached tooth and accompanying periodontium.
Figure 10. Bilateral mucous retention cysts in maxillary antra (each arrowed).
Category: incidental finding.
Frequency: common. Reported in one study to occur in 1.4–9.6% of the population.12
Symptoms: few or none.
Appearance: classic, dome-shaped appearance with no underlying mucosal thickening. A dome-shaped appearance on a background of mucosal thickening suggests polyposis (see later).
Management: leave if not implicated in surgery (usually collapse and regress). If considering sinus lift for implant placement then may require removal. ENT referral warranted if symptomatic.
Always consider: other causes for occupancy in the sinus (eg mucosal polyp, sinusitis, recent trauma and malignancy). A unilateral opacified sinus is a clinical concern and warrants referral to ENT.
Figure 11. A smaller superior canal running parallel to the main neurovascular inferior dental canal. A branch from the superior canal is given off directly beneath the mesial root of the lower right second molar (LR7). There are clear periapical changes also affecting the lower right first molar (LR6). There is radiolucency apparent beneath the restorations of all the molar teeth (LR6, 7, 8), which is suggestive of caries; however, the artefact does not make CBCT a suitable modality to aid in caries detection.
Category: anatomical variant.
Frequency: uncommon; however, one study of 225 patients showed that over 36% demonstrated a bifid inferior dental canal.13
Appearance: a well-defined, corticated radiolucent tract arising from the mandibular canal and usually courses in symphony with the neighbouring canal.
Symptoms: none.
Management: none, relevant to dentoalveolar surgery and implant surgery in the posterior mandible.
Figure 12. A prominent canalis sinuosis seen emerging in the left anterior palate (arrowed). Note the opacification of the right maxillary sinus indicative of mucosal thickening/polyposis.
Category: anatomical variant.
Frequency: a well-described neurovascular bundle that passes through the wall of the maxillary sinus and can exhibit significant variation in its path and emergence.
Appearance: a nerve that starts in the region of the infra-orbital foramen and travels within its own bony canal to emerge on the anterior palate.
Symptoms: none.
Management: Relevant for placement of dental implants and dento-alveolar surgery in this region. Evidence to suggest that implant placement in this region can result in hindered osseo-integration and paraesthesia.14,15
Symptoms: none. May present with symptoms of pulpitis or apical periodontitis.
Appearance: coronal or radicular radiolucency. It is important to mention that CBCT should NOT be used for caries detection due to artefact degradation, which can affect the image in this region.
Management: non-operative management (eg fluoride and oral hygiene instruction), restoration or extraction of the tooth.
Figure 13. A dense bone island in the left maxilla. Note how the bone does not have a radiolucent rim and is contiguous with the palatal cortex suggesting the diagnosis.
Category: anatomical variant.
Frequency: extremely common and a common cause for referral to secondary care.
Symptoms: none.
Appearance: increased localized radiopacity in the jaws usually 2–3 mm in diameter but can be up to 2 cm.16 It is commonly contiguous with the cortex.
Management: no indication for removal. Some evidence is available to demonstrate that dense bone islands should be considered in orthodontic planning as they can affect the length of treatment and be implicated in root resorption of teeth in direct contact.17
Always consider: sclerosing osteitis in response to peri-apical infection on a non-vital tooth. Occasionally, metastasis to the jaw bones can present as an area of localized radiopacity. It is unlikely that this will be the first presenting feature of the condition. Multiple dense bone islands (usually more than five), should also raise suspicion for Gardner's syndrome.
Figure 14. Coronal section of the mandibular left third molar (LL8) exhibiting gemination.Figure 15. The left image shows the axial view of tooth fusion affecting the lower right central and lateral incisor (LR1 and LR2). The right image is a parasagittal slice of the same fused teeth. There is one less tooth in the arch because of the fusion (each arrowed).
Category: anatomical variant.
Frequency: uncommon (0.1–0.2% in the permanent dentition).18 This is the value given for ‘double-teeth,’ which includes gemination and fusion.
Symptoms: none, unless traumatic to soft tissues or aesthetically displeasing.
Appearance: a double crown with a separating cleft. The same root system is shared in gemination. In gemination, there are a normal number of teeth in the arch, and in fusion there is a reduced number of teeth in the arch.
Management: leave if asymptomatic, but intervention is required if aesthetically concerning for the patient.
Figure 16. Mucosal thickening of the right maxillary antrum (arrowed).
Category: incidental finding.
Frequency: common. In one study, over 20% of 762 CT scans of the facial bones demonstrated mucosal thickening in the maxillary antra.19
Symptoms: either none or a history of sinusitis.
Appearance: increased radiodensity of the lining of any of the sinuses. The lining is most frequently thickened in the alveolar recess. In health, the sinus lining should be <3 mm in thickness. Irritation may come from exogenous sources (eg hayfever) or inflammation secondary to odontogenic infection. Increased thickness of the bony wall of the sinus suggests chronic disease or fungal infection.
Management: none unless the patient has active complaint of sinusitis-type symptoms, in which case, GP or ENT referral is advised.
Figure 17. A peri-apical radiolucency is noted on sagittal slices of the upper left central incisor.Figure 18. Profound sclerosing osteitis around the LL8 which had undergone resorption. The inferior dental canal is clearly preserved centrally within the area of osteitis.
Category: incidental finding.
Frequency: extremely common, one study determined CBCT demonstrated significantly more peri-apical lesions than conventional peri-apical films, particularly in maxillary molar teeth.20
Symptoms: asymptomatic or symptoms of chronic peri-apical periodontitis.
Appearance: radiolucent change of the peri-apical bone and occasional associated sclerosing osteitis. Loss of continuity of the lamina dura.
Management: endodontic treatment or extraction as necessary.
Figure 19. Two pulp stones seen in the erupting maxillary permanent canines (arrowed).
Category: anatomical variant.
Frequency: extremely common. One study showed that from a cohort of 144 patients, over 83% had a pulp stone demonstrable on CBCT.21
Symptoms: none.
Appearance: radiopacity within the pulp complex of the tooth.
Management: none required. Only of clinical significance if tooth is to undergo endodontic treatment. Occasionally associated with Ehlers–Danlos syndrome.
Figure 20. A retromolar canal seen emerging from the inferior dental canal and coursing anteriorly through the ramus (arrowed). The contents of the canal can be neural, vascular or both in origin.
Category: anatomical variant.
Frequency: common. In one study of 272 CBCT scans, retromolar canals were found in 28% of cases.22
Symptoms: none
Appearance: a branch of the inferior dental neurovascular bundle that travels postero-superiorly in the posterior mandible to supply the retromolar trigone.
Management: none, but relevant to mandibular third molar surgery and surgery involving the mandibular ramus. Contents of the canal will be neurovascular, therefore, there may be an associated bleeding risk.
Sinus and nasal polyps (sino-nasal polyposis) (Figure 21)
Figure 21. Bilateral nasal polyposis (arrowed). Note incidental mucosal thickening in the right maxillary antrum.
Category: incidental finding.
Frequency: common. One study reported that over 5% of patients from a cohort of 703 had polyps in the maxillary antra.23
Symptoms: usually few, occasionally symptoms of sinusitis or may be associated with a foreign body in the maxillary antrum (eg displaced tooth root).
Appearance: domed soft tissue densities on a background of mucosal thickening. Will not regress without intervention.
Management: none unless symptomatic or implicated in the field of implant surgery.
Figure 22. A well-defined concavity in the right posterior mandible beneath the inferior dental canal (arrowed), which is almost diagnostic of Stafne's idiopathic bone cavity.
Category: anatomical variant.
Frequency: uncommon.
Appearance: a well-demarcated lingual concavity of the mandible with its epicentre beneath the inferior dental canal.
Symptoms: none.
Management: none, except reassurance.
Tooth resorption (including external, replacement and internal) (Figures 22–25)
Figure 23. Resorption of the distal root of the lower left second molar (LL7) distal root only became apparent on CBCT imaging (arrowed).Figure 24. CBCT imaging ordered to plan for exposure and bonding of the lower left canine (LL3) revealed significant resorption of the coronal tissue (arrowed). This was not apparent on plain film imaging.Figure 25. Replacement resorption affecting the distal root (arrowed) of the lower left first molar (LL6).
Category: incidental finding.
Frequency: common.
Symptoms: very few symptoms, may occasionally present with pulpitis or apical periodontitis.
Appearance: internal resorption may manifest as increased size or ballooning of the pulp canal. External resorption may present as irregular radiolucency within the tooth representing loss of tooth substance, this irregular radiolucency is contiguous with the external surface of the tooth. In replacement resorption, the dental tissues unperceivably merge with the surrounding alveolar bone.
Management: surveillance, restorative/endodontic treatment or extraction.
Conclusion
There are numerous incidental findings that can appear on dento-alveolar-sized CBCT volumes. It must be borne in mind that this is not an exhaustive list, nor will all incidental findings manifest in the same way shown as above. Part 2 of the series looks at structures beyond the field of the dento-alveolar hard tissues and the immediate surrounding vicinity.
Figure 26. Internal resorption affecting the upper left first premolar (arrowed). There is also a peri-apical radiolucency associated with this tooth suggestive of peri-apical pathology.
