Incidental Findings Determined on Patients’ Cone-Beam Computed Tomography Scans When Evaluating Bone Width and Depth for Potential Implant Placement

Cone-beam computed tomography (CBCT) was first developed in the 1980s and, over the years, has been integrated into the field of dentistry as it provides an unparalleled ability to view the maxillomandibular region in a 3-dimensional (3D), comprehensive manner.¹ Compared to a conventional CT scan with its fan-shaped x-ray beam, a CBCT scanner utilizes a cone-shaped beam.¹ This difference in the shape of the x-ray beam allows for a single rotation at a constant angle and the compiling of a volumetric data set by stacking cones that can then be converted into a 3D image.¹ As opposed to past 2-dimensional (2D) imaging with superimposed structures and distortions that produced an image that was difficult to interpret, CBCT scans correct for such faults.² Because of this ability, incidental findings have been identified and reported on many asymptomatic patient CBCT scans whose 2D imaging showed no pathology. As it relates to the current work, such incidental findings have been defined as dentoalveolar findings found by CBCT that were unrelated to what the patient was being seen for and, furthermore, was unaware of.

In previous studies incidental findings have been related to the sinus, cervical, temporomandibular joint, and impacted teeth, to name a few areas, with the percent of incidental findings reported ranging from 40% to about 90%.^3,4 In a retrospective study of 318 patients with CBCT scans taken for implant consultation, all incidental findings identified in the head and neck region were denoted as non-tooth-related pathologies or abnormalities.¹ Often the most common incidental finding was related to either the sinus or airway shown in another study with a large sample population of more than 800 patients where incidental findings in the airway were determined in 42.3% of patients followed by the paranasal sinuses in 30.9% of patients included in the report.³ In another study encompassing CBCTs from 500 patients, the most common incidental finding determined was soft-tissue calcification in 25.8% of the sample population.² Clinical significance has also been discussed where over 90% of patients presented with some form of incidental findings, yet only about 5% of sinonasal findings were denoted as severe and referred to another practitioner for further evaluation.⁵

As can be seen, none of these previous publications cited report dentoalveolar radiographic findings specifically or their clinical significance as it relates to further evaluation by another practitioner. However, from searching the literature on related articles previously published, one of the most common incidental findings has been in the dentoalveolar region, yet no article has been specifically dedicated to this area.⁴ In the authors' oral and maxillofacial surgery practice, many incidental findings have been recognized on patient CBCTs during implant consultations. Because of this, the authors decided to conduct a retrospective study in order to quantify the amount and classify the type of incidental findings found on a successive group of patient CBCT scans and determine the frequency within age groups in an effort to support and guide routine use of CBCT imaging in general practice offices.

From an in-house diagnostic CBCT scanner, 106 successive patients were retrospectively evaluated for possible incidental findings. Between two locations from January to August 2020, all patients received a single CBCT exposure. The field-of-view (FOV) size was also determined based on where the CBCT was taken given that the two x-ray machines differed by office location. The two CBCT scanners used in this study were the Orthophos^® XG 3D (Dentsply Sirona, dentsplysirona.com) with a smaller FOV of 8 cm x 8 cm and the Galileos^® (Dentsply Sirona) with a larger FOV of 15 cm x 15 cm. All patients included in this study were seen for an implant consultation or extraction consultation in preparation for the placement of a future implant. The 3D imaging in the form of a CBCT for these patients was consistent with American Academy of Oral and Maxillofacial Radiology guidelines for appropriate radiation dose when conducting these measures.⁶

Of the 106 patients included in this successive group of CBCTs analyzed, 56 were female (52.8%) and 50 were male (47.2%).The age of the patients ranged from 25 to 89 years, and the patients were separated into seven age groups (20-30, 31-40, 41-50, 51-60, 61-70, 71-80, and 81-90). The mean age was 61.7 years and the median age was 62.5 years.The distribution of patients within each age group is shown in Figure 1.

The incidental findings reported were divided into subcategories that included the presence of a periodontal bony defect, periapical radiolucency, residual root, gross caries, internal resorption, odontogenic cyst, radiopaque lesion, and impacted cuspid.The most frequent incidental findings were in the form of periapical radiolucencies (38 instances noted) (Figure 2). As can be seen in Figure 3, which shows the frequency of all incidental findings within each age group, 63 of the 69 incidental findings noted in this study were found in patients aged 41 years or older. Table 1 denotes both the category and number of incidental findings.

Although many patients (60) presented without any additional, unintended findings on their CBCT besides what was known and being treated, it cannot be discounted that there were still 69 incidental findings in patients who had other recent 2D imaging sent from their general dentists. The types of 2-dimensional imaging and the amount of 2D images received for patients being evaluated for the placement of future implants can be seen in Figure 4. In some instances (12), previous 2D imaging was not made available from the patient's general dentist. Even when referred with 2D imaging, some patients (17) presented with more than one incidental finding, such as a periapical radiolucency on one tooth and internal resorption on another, for example. Without the ability to visualize both arches included in the FOV when taking a CBCT, such asymptomatic incidental findings had gone unnoticed by both the practitioner and the patient.

For patients undergoing implant treatment, a CBCT scan is taken to determine the width and depth of the bone to guide implant planning for ideal placement. Such images comprise the patient population included in this retrospective, observational study. CBCT scan use not only allows for the visualization of bone dimensions but also the evaluation of the rest of the dentoalveolar complex. With CBCT use, the frequency of unintended, incidental findings has become a recognized pattern, with such findings ranging from gross caries, radiopaque lesions, and moderate-to-severe periodontal bony defects to, most commonly in this study, periapical radiolucencies seen in high resolution on the CBCT.

Although only 38 occurrences of periapical radiolucencies were noted out of the total 69 incidental findings determined, it should be emphasized that 63 of those 69 (91.3%) incidental findings were in patients aged 41 years or older. Within the group of patients that presented with incidental findings on their CBCTs, some (17) included more than one incidental finding. It should also be noted that 60 out of the 106 patients (56.6%) included in this study did not present with any incidental findings. Categories for this study were standardized by only counting the findings that were obvious on the CBCT. In some instances, it was unclear if something should be counted or not. Because it was a criterion of this study for someone to see that some abnormality was recognized on the 3D scan, whether that be a periapical radiolucency or moderate-to-severe periodontal bony defect, some minimal or possible findings were not included in this study. Examples of each incidental finding are shown in Figure 5 through Figure 12.

Recording a 3D CBCT scan to evaluate a patient's bone during an implant consultation led to the discovery of unintended, incidental findings of which the patient and referring dentist were unaware despite having recent 2D periapical and/or panoramic radiographs taken. That being said, this retrospective, observational study was not conducted to point out or blame the referrer for missing the incidental finding but to demonstrate the advantages of being able to see the entire dentition in three dimensions, which is only made possible through the use of a CBCT scanner. Because of the common occurrence of these unintended findings, the authors were led to the question of the exact amount and frequency of incidental findings found on CBCTs taken for implant consultations. To address this question, a retrospective, observational study evaluating a successive group of patient CBCTs was conducted. In this study, 38 instances of periapical radiolucencies were noted that were not related to, nor were they the reason for taking, the CBCT in preparation for the placement of a future implant. Even though 60 patients did not show any evidence of additional, unintended findings on their CBCT, the authors underscore that 63 of the 69 incidental findings noted were in patients aged 41 years or older. Some of those patients (17) even presented with more than one incidental finding upon analysis of their CBCT. This would suggest and further supports CBCT use for new patients to a general dentist's office when the patient is 41 years of age or older.

Despite the high resolution and specificity provided by a CBCT scan, in some instances it was still unclear whether an incidental finding should be counted or not, especially regarding periapical radiolucencies. This presents the common "Pandora's box" dilemma when analyzing CBCT scans and the ethical component of reporting every observation no matter the magnitude.⁷ For this particular study, the incidental findings counted were clear radiographic findings seen on the 3D image (Figure 5 through Figure 12).

Limitations of this study include the sample size as well as the composition of patients, which comprised a very select group treated in a private practice oral surgery office over a 7-month timeframe. Further investigation in a general practice setting could provide an interesting comparison given the narrow criteria for patients being referred for implant consultation to not only quantify the frequency of intraoral incidental findings over a longer period of time but also incorporate treatment planning and follow-up to determine clinical significance in a more diverse group of patients.

Chelsea Herr, BS
First-Year Dental Student, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Douglas Smail, DDS
Private Practice in Oral and Maxillofacial Surgery, Troy, New York

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