Unexpected artefacts and occult pathologies under CBCT

SUMMARY

Purpose

To present the most frequent occult pathologies unexpectedly encountered via cone-beam computed tomography (CBCT), with particular reference to the diagnostic role of the dentist and that of the radiographer, with a view to clarifying where the diagnostic responsibility lies.

Material and methods

A narrative literature review on the most diffused occult pathologies under CBCT was conducted, with iconographical guide as an example for each category.

Results

The most frequent forms of unexpected pathologies encountered are: the presence of foreign bodies, airway anomaly, and the presence of radio-opacity or -transparency in the maxillofacial district.

Conclusions

The orthodontists must know that they are responsible to recognize these frequent, and potentially serious, pathologies of the head and neck. If the dentist feels unable to take on this responsibility, he or she should, however, be sure to have the scans read by a specialist radiologist.

Introduction

The superiority of cone-beam computed tomography (CBCT) with respect to traditional two-dimensional radiographic techniques is well known throughout the scientific community (1–3). In addition to being more precise and reliable, the information provided by this technique is also greater in quantity. In fact, whereas orthopantomograms and teleradiograms can be viewed by an experienced clinician in relatively little time, CBCT can involve the analysis of over 500 axial, sagittal and coronal sections (4).

Furthermore, CBCT scans the entire head and neck district, including anatomical structures of little orthodontic interest. However, this means that dentists are in a very good position to encounter occult pathologies, which, despite being outside their direct sphere of expertise, cannot remain undiagnosed.

Thus, the increasingly diffuse use of CBCT, very often in young patients, forces the clinician to undertake serious ethical and medicolegal reflection (5–10). Among the most evident issues to be addressed is whether the training a dentist has undergone makes him or her able to recognize these frequent, and potentially serious, pathologies of the head and neck, or whether referral to a radiographic specialist would be more opportune. In fact, to date, the respective responsibilities of the person who commissions and the person who performs a volumetric scan still remain to be clarified. In addition, CBCT should be careful evaluated in syndromic patients (11–34).

Hence, the aim of this study was to present the most frequent occult pathologies unexpectedly encountered via CBCT, with particular reference to the diagnostic role of the dentist and that of the radiographer, with a view to clarifying where the diagnostic responsibility lies.

Occult pathologies evidence by CBCT

The occasional discovery of occult pathologies upon commissioning orthodontic X-rays is a widespread and well-known occurrence. Indeed, a study conducted by Bondemark in 2006 showed that the OPTs of 8.7% of 496 orthodontic patients displayed anomalies other than those for which the X-ray was commissioned (35). According to Tetradis (1999), on the other hand, careful evaluation of laterolateral teleradiograms can reveal cranial calcifications, sinus problems or hypertrophic adenoids or tonsils in 8–18% of patients (36).

More recently, however, the diffusion of CBCT has broadened the investigative field, and therefore multiplied the range of pathologies that can be diagnosed. The potential for encountering unexpected pathologies has therefore tripled, from 8 to 24% of patients (37).

The pathologies encountered unexpectedly by CBCT are usually asymptomatic, and can be divided into two categories: those considered to be variations in normal anatomy with no consequences for the patient, and those requiring specialist referral before dental treatment can be commenced. An example of the latter could be sinusitis in patients scheduled for miniscrew implantation in the upper jaw; in this case the sinusitis needs to be resolved in order to improve the chances of successful implantation or orthodontic treatment.

In the worst case scenario, serious pathologies that put the life of the patient at risk, such as plaques in the carotid arteries or tumours, can be encountered, necessitating the postponement or suspension of the planned treatment and immediate referral to a specialist (38).

The most frequent forms of unexpected pathologies encountered are: the presence of foreign bodies, dental abnormalities, airway anomaly, TMD, cervical vertebrae anomaly, and the presence of radio-opacity or -transparency in the maxillofacial district (39).

Performing CBCT (Figures 1, 2) permits the identification of foreign bodies in maxillary sinus and also to be defined in relation to the surrounding structures.

Figure 1.

Foreign body visible under CBCT.

Figure 2.

Foreign body visible under CBCT.

Airway disorders (sinusitis, nasal polyps, deviated septa, hypertrophic adenoids or tonsils, mucosal retention cysts) are also frequently observed, especially in adolescent patients between 12 and 16 years of age. For instance, Figures 3–5 show a case of severe asymmetry between the left and right maxillary sinuses.

Figure 3.

Polypoid formation and asymmetry.

Figure 4.

Polypoid formation and asymmetry.

Figure 5.

Polypoid formation and asymmetry.

In addition (Figures 3–5) CBCT can evidence in-vagination of the maxillary sinus between the roots of the first molars, a strong contraindication for treatments such as molar distalization (40).

Cervical vertebrae anomalies uncovered by volumetric scans, on the other hand, are more common, and could be indicators of various disorders, for example Klippel-Feil syndrome, a congenital disease causing the fusion of at least two cervical vertebrae. Abnormalities of the odontoid process of the epistropheus could also be the result of a congenital condition, or of a traumatic event. Despite the potential severity of these conditions, which may compromise the stability of the spine, their incidence is difficult to evaluate in that these alterations are almost always asymptomatic (41).

Asymptomatic areas of radio-transparency, usually without risk to the patient’s health, include Stafne cysts and ossification defects of the parietal bone. These do, however, require referral for more in-depth diagnostic analysis (42, 43).

A far more frequent, and potentially very serious, occult pathology is the presence of calcifications in the carotid arteries. Carotid stenosis and consequent arterial plaque fragmentation are the cause of almost one half of all cardiac infarctions. As calcification at the carotid sinus can be seen under OPT, it should be unfailingly evident to the expert eye under CBCT. Due to its aetiology, this is a condition that affects adult patients (2% of all dentistry patients and 5% of over-55-year olds). However, it must be borne in mind whenever a scan for implantation purposes is performed as early diagnosis, and consequent referral to a specialist, greatly influences the survival prospects of the patient (38).

Discussion

CBCT is becoming increasingly common as a diagnostic aid in dental and orthodontic patients and oral surgery especially in cases requiring dental implant positioning (44–85).

The most advanced models of this type of scanner permit definition of the field-of-view (FOV), which is generally between 6 and 12 inches, but it tends to be greater in dental investigations, as the jaws, paranasal (and frontal) sinuses, upper airways and condyles may all be of interest. This means that the dentist is in an excellent position, and therefore has the ethical obligation, to evaluate all sections taken in search of occult pathologies, which are by no means rare (86).

What the dentist should do with this information, however, does require further clarification. Naturally, orthodontists will not be expected to provide an accurate diagnosis of conditions falling outside their sphere of expertise. Nevertheless, familiarity with the normal anatomy of the head and neck is their obligation, and they should be duty bound to recognize any abnormality and consequently refer the patient to the appropriate specialist (87).

In such matters, the guidelines set out by the European Academy of DentoMaxilloFacial Radiology are explicit: points 17 and 18 stress the importance of suitable and continuous training for all dentists involved in the use of CBCT, not only as regards the use of the machines themselves, but also, and especially, concerning the interpretation of the resulting images (18). Moreover, points 19 and 20 of these guidelines clarify the current trend in the division of responsibilities: restricted FOVs, involving only the jaws, are within the field of expertise of both the expert dentist and the radiologist specialized in the maxillofacial district. It is suggested, on the other hand, that scans with larger FOVs be analysed by a radiology specialist (88).

From a legal perspective, dentists as well as radiologists may own a CBCT scanner (87). If a dentist does not, however, possess one, patients can be sent either to a better-equipped colleague or to a radiological institute, armed with a specific request.

However, in order to circumvent potential legal issues, some radiological centres issue radiographic images for dental use specifying that they have not been examined by a radiologist, making them merely an aid to implantation, extraction or other orthodontic treatment. In these cases, if a patient desires a specialist reading, they are forced to expressly request the services of a radiologist and pay the corresponding fee. However, this ‘solution’ is indefensible from a medicolegal standpoint as the clinician who has commissioned the scan is considered responsible for analysing all the data provided (89). Furthermore, the specialist who performs the scan has the same degree of responsibility as the dentist who commissioned it as regards verification of the reasons behind the examination and in ensuring complete reading of the slices, thereby effectively providing the patient with a double guarantee (90).

Thus, the international trend is to safeguard the patient as much as possible, ensuring that the scans are examined by the most competent professional, expert in the body district in question, and sharing the responsibility between all the clinicians involved in requesting and performing the diagnostic investigation.

Conclusions

Although widespread dissemination of CBCT scanning within the field of dentistry, particularly in orthodontics, has considerably increased the diagnostic potential, several ethical and medical-legal issues have consequently come to the fore.

In fact, professionals exploiting such a technique can often encounter occult pathologies, which cannot be left undiagnosed.

According to legal guidelines, the responsibility for diagnosing such pathologies is shared by all the specialists involved in the investigation.

In particular, when using large field-of-views, dentists must be able to recognize such occult pathologies, even if they fall outside their direct sphere of expertise. Even if the dentist feels unable to take on this responsibility, he or she should, however, be responsible for having the scans read by a specialist radiologist.

Indeed, although no universal international law yet governs these matters, the current trend is to safeguard the patient, entrusting the correct reading of three-dimensional scans to appropriately trained specialists.