Drs. Winter, Baradarian, Sivitz

Dental 3D Cone Beam CT Imaging: Part V Dental Incidentalomas

Using 3D CT imaging for diagnostic purposes in medicine has uncovered incidental tumors that had no clinical symptoms in various tissues when there was no previous suspicion that they were present. These incidental tumors have been dubbed "incidentalomas," and been discovered in adrenal glands, kidneys, pituitary glands, thyroid glands, liver, lungs, and the parathyroid glands (1-18). It has been estimated that approximately 7% of all patients over 60 may harbor a benign growth (often of the adrenal gland) and with the increase of "whole-body CT scanning" as part of health screening programs, the chance of finding incidentalomas is expected to increase to 37% (19). These chance findings will, in many cases, require further investigation.

A search of the dental literature did not reveal any studies that dealt with incidental findings on 3D CT studies taken on cone beam scanners. Nor has the term "incidentaloma" been applied to dentistry. In this 3D CT cone beam study, 500 consecutive patients sent to one of nine i-dontics, llc radiologic labs were analyzed for a variety of normal and abnormal findings. Part I studied why patients were referred for CT studies including their age, gender, and format of the requested study. Part II studied the lingual artery and its insertion into the mandible. Part III studied the frequency and location of bifid canals. Part IV studied the length and location of the anterior canal extending anterior to the mental foramen. And in this study, Part V, the frequency and type of incidental findings on patients ostensibly sent to a dental CT radiological lab for 3D scans for dental implants were analyzed.

Methods and Materials
Data from five hundred (500) consecutive patients sent for 3D CT cone beam studies to one of 9 centers located in 3 states were evaluated. Scans were taken on either i-CAT (8 centers) or on a NewTom 3G scanner, and uploaded to a central data center. All studies were converted to SimPlant™ (Materialise, Glen Burnie, MD.). When not specified, the data was converted to SimPlant™ version 10.

In this part of the 3D study, the following parameters were recorded for each patient: if the maxillary sinuses were free of pathology or to what extent pathology was present. In addition, the following were noted: the presence of radiolucencies at the apices of teeth; were the teeth noted with radiolucencies vital or non-vital; impacted teeth and supernumeraries, retained roots, cysts, the presence of dental implants, and the radiopaque presence of bone graft material. Other incidental findings noted on the 3D Ct images included the notation of severe periodontal bone loss, fourth molars, condensing osteitis, surgical tacks, etc.

Five hundred (500) patients were included in this study. Of the five hundred, two hundred and four (204) were referred exclusively for maxillary studies and an additional seventy-nine (79) (refer to Part I of this study), were referred for both maxillary and mandibular studies. A total of two hundred and eighty-three maxillas studied (Figure 1) for observations about the maxillary sinus. The CT scans for all 500 patients were analyzed for incidental findings.

Figure 1. Of the 500 patients in this study, 279 had maxillary scans evaluated.

Ninety-one (91) patients had both maxillary sinuses free of pathology while ninety (90) patients had pathology in both sinuses at the same time, as noted on the CT images. Pathology was defined as less than 1mm of a mucosal thickening measured at any part of the sinus visible in the CT scan. When pathology was present (1mm or greater of mucosal thickening), one maxillary sinus remained clear or free of pathology in 78 patients: 41 in the right and 37 in the left.

When present, the amount of mucosal thickening was measured in each sinus. The mucosal thickening in the right sinus averaged 5.3mm and it measured 5.6mm in the left sinus. In addition, 26 patients had polyps in the right maxillary sinus and 22 patients had polyps in the left maxillary sinus. Six maxillary sinuses were totally blocked both right and left (Figure 2). Polyps were observed in some patients with mucous thickenings, so that the total number of observations is greater than the 283 maxillary sinuses studied.

Figure 2. 91 of the 283 maxillary scans had no pathology in both the right and left maxillary sinuses. 90 patients had pathology noted in both maxillary sinuses and 78 patients had pathology in only one of the maxillary sinuses. 48 patients had a polyp noted in either the right or left maxillary sinus, or both.

Reasons for dental 3D CT scans. The predominant reason for referral for dental CT scans was for pre-surgical analysis for the insertion of dental implants. Four hundred and fifty-one patients (451) were referred for implants; 20 for impacted teeth; 10 for pathology; 7 for endodontics; 4 for orthodontics; 1 for TMJ disorder; 7 unknown (Figure 3).

Figure 3. A = 451 Patients referred for CTs for implants; B = 20 patients for impacted teeth; C = 10 patients for pathology; D = 7 patients for endodontics; E = 4 patients for orthodontics; F = 1patient for TMJ; G = 7 patients unknown reason for referral for CT.

Incidental findings. While 451 patients (out of 500) were referred for a 3D dental CT scan for the express purpose of pre-surgical planning for implant insertion, many incidental findings were noted. The most common incidental findings (Figure 4) were periapical radiolucencies (229), socket preservation bone grafts (46), impacted teeth (27), retained root tips (24), sinus grafts (12), cysts (8), and supernumerary teeth (2). In addition, 70 dental implants were previously inserted in these patients. Other observations (142) included cementomas, surgical screws and tacks, assorted opacities within the body of either arch, 4th molars, blunted apices (due to orthodontics), blocked ethmoid sinus, condensing osteitis, and advanced periodontal disease nearly to the apices of many teeth.

Figure 4 The most common incidental findings were: 229 periapical radiolucencies; 46 socket preservation bone grafts; 27 impacted teeth; 24 retained root tips; 12 sinus grafts; 8 cysts; 2 supernumerary teeth.

In the medical literature, the term "incidentaloma" refers to the discovery of a previously unsuspected tumor when taking a CT scan for another purpose. This term has not entered the dental literature. It is suggested that a dental "incidentaloma" be defined as the discovery of any unsuspected pathology, anomaly, dental structure (such as a retained root tip, impacted tooth, or supernumerary), or deviation from normal anatomy on a CT scan. The implications of these findings challenge the dentist and dental surgeon to be familiar with both normal and abnormal structures as they present on 3D cone scan imaging, which can appear different and unfamiliar compared to traditional 2D X-ray images such as periapical dental films or panoramic X-rays. Furthermore, it is incumbent for the dentist to interpret the entire field of view of each CT scan, and not just the area of concern, such as an implant site or a recalcitrant endodontic lesion or where the IAN is relative to an impacted third molar.

The most frequent incidental finding in this study was periapical radiolucencies. Many authors have acknowledged that 3D cone beam CT scans are extremely accurate and can be relied on for making a diagnosis of periapical pathology (20-23). For purposes of this study, periapical pathology was defined as a lesion expanding larger than 1mm from the apex. This was chosen to remove doubt that a pseudoperiapical lesion was not a thickened PDL due to trauma from occlusion. There was no attempt to obtain the previous history of teeth with root canal therapy to compare the size of the present lesion with past X-rays. No determination was made if a periapical lesion noted in this study was old, non-expanding, or a healing granuloma.

This 3D CT study noted trends in therapy. For instance, 46 extraction sockets were treated with graft material and the dental surgeon was interested in a 3D analysis of the healing lesion. Likewise, patients who had previously had maxillary sinus grafts (12) received 3D CT scans to determine the success of these surgeries.

Twenty-seven (27) teeth other than the ones patients who were originally referred for CT scans, were impacted, and two supernumeraries were noted. These "incidental" findings were sent in a report to each dentist for their review, final approval, and action when they deemed it necessary.

It is apparent that with the advent of dental cone beam scanners, more dentists will take advantage of 3D technology for better surgical planning, improved diagnostic preparation for orthodontic patients, all of which contribute to lower risk and more successful outcomes for the patients. While dentists embrace 3D technology, they need to become familiar with normal and abnormal landmarks. In addition, they need to be prepared to identify incidental findings and inform their patients as to the existence of these findings and their clinical relevance.

This study noted many incidental findings on 3D dental CT scans and suggests that these findings be described as "incidentalomas." These unexpected findings include sinus pathology, cysts, impacted teeth, supernumeraries, periapical radiolucencies, and more. It is suggested that dentists become more familiar with normal and abnormal landmarks in the increased field of view of CT studies, especially when these 3D images are taking in preparation for dental implant treatment planning..

Acknowledgements: Support for this study was generously given by Nobel Biocare AB Gothenberg, Sweden (Grant 2006-492) and Imaging Sciences Inc., Hatfield, PA.

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Tags: 3D cone imaging, sinus grafts, periodontics, dental implants, laser gum surgery, dentist, dental practice, gum treatment. LANAP, bleeding gums, periodontal disease

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