Drs. Winter, Baradarian, Sivitz

Dental 3D Cone Beam CT Imaging: Part I Demographics

Alan A. Winter, DDS, et al

Dental 3D cone beam CT imaging has replaced traditional medical CT scans that first became commonplace after endosseous dental implants were first introduced by Dr. Per-Ingver Brånemark (1) in the early 1980s. With the advent of the DentaScan software, dentists viewed CT images in multiple planes: coronal (known as panoramic), axial, and sagittal (known as cross-sectional or transaxial) for better and safer implant placement. Applications for CT scans extended from implantology to other oral and maxillofacial uses (2-9). Until recently, CT scanners were situated in medical radiological offices where dentists referred their patient for 3D studies for implant treatment planning. With the introduction of cone beam volumetric tomographic (CBVT) scanners in April, 2001, a new era of dental radiology was launched (10).

These 3D cone beam dental (CBVT) scanners, approved by the FDA as dental devices and often referred to as “dental CT scanners,” offered improved diagnostic tools over existing medical CT scanners due to their low-dose radiation requirements and more accurate, diagnostic images for implant placement, removal of impacted wisdom teeth, and more. Dental radiological labs first gained recognition (1972) in California when oral and maxillofacial radiological technicians were permitted to own and operate X-rays centers. Upon their introduction, these radiological labs embraced cone beam scanners (NewTom 9000).

The first change to a 3D dental scanner was introduced by Imaging Sciences International - the i-CAT™ - in March, 2004. This dental CT cone beam scanner had a smaller footprint and was designed for dental offices. Rather than lie on a gurney, patients would sit in a chair while the scan was taken. This version of the CBVT scanner enabled busy dental practitioners to buy 3D CT scanners. In addition to using it for their own patients, dentists often solicited colleagues in their community to their send patients for dental 3D CT images. In effect, they created de facto radiological practices. And still others, both dentists and/or entrepreneurs, created freestanding radiological labs for the express purpose of taking and processing 3D CT images for other dentists.

To date, data concerning the type of patient referred to a dental cone beam radiological center and the reason for the prescribed 3D CT scan has been anecdotal. While it is assumed that the main reason most dental patients are referred for CT scans is for pre-surgical dental implant analyses, no article has studied the demographics of this relatively new phenomenon: the dental cone beam 3D CT radiological lab.

The purpose of this study was to determine how and for what reason dentists currently utilize a 3D cone beam CT imaging center. In addition to the types of patients and the reasons they were referred for CT scans, the following were recorded from each study when appropriate: the incidence and location of the lingual artery inserting into the mandible, measurements and observations about the extension of the inferior alveolar canal anterior to the mental foramen, the incidence and location of bifid canals, the incidence of sinus pathology, and the identification of incidental findings other than the reason for the CT referral including impacted teeth, periapical radiolucencies, pathologies, retained roots, etc. All of these anatomical structures impact on the success, failure, and risk of dental implants, removal of impacted third molars, and other dental surgical procedures.

Part I of this study consists of data of patients referred to a dental radiological lab for 3D CT scans including age, gender, purpose of the CT study, which arch was requested, if a radiographic guide was used, and in which format the study was requested to be processed.

Methods and Materials
Data from five hundred (500) consecutive patients sent to i-dontics center from 9 centers located in 3 states were evaluated. Scans were taken on either a cone beam 3D i-CAT (8 centers) CT scanners or on a NewTom 3G (Manhattan) 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. The following parameters were recorded for each patient: age, gender, reason for the scan (i.e. dental implants), dental arch studied, the format for the delivery of the data, and whether or not a radiographic guide was used.

One Hundred and ten (110) dentists referred 500 patients for 3D cone beam CT studies. Two hundred and twenty-eight (228) or 44.4 % of all patients referred for were male; two hundred and seventy-two (272) or 55.6% of the patients were females (Figure 1).

Figure 1. Gender of patients

Patient ages ranged from 15 – 102 years (Figure 2). The mean age was 56.7 years.

Figure 2. Number of patients in each age category.

Reasons for CT scans. The predominant reason for referral for dental CT cone beam scan was for pre-surgical analysis for dental implants. Four hundred and fifty-one patients (451) were referred for dental 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.

Each 3D CT study was categorized either as a mandibular scan or a maxillary scan, or both, regardless of the reason for the dental CT 3D scan (implants, impactions, endodontic problems, or pathology). In the single instance of a TMJ study, the patient also had an edentulous mandibular site evaluated for an implant, so this patient was counted as a mandibular study (Figure 4).

Figure 4. CT scans for the maxilla = 40.8%; CT scans for the mandible = 43.4%; CT scans for both arches = 15.8%.

Delivery format. CT dental cone beam studies were requested in a variety of formats: via Internet; transparencies; CD; Prints. In 12 instances, studies were requested in multiple formats by students in the implant program at New York University College of Dentistry. Consequently, 512 different formats were requested for the studies: transparencies = 42; glossy prints = 55; CDs = 239; and 176 via the Internet (Figure 5).

Figure 5. Formats for CT scans were received in four ways: Film, Prints, Internet, and CD.

Software. Four hundred and four (404) requests were made for specific 3D CT dental treatment planning software. The requests were as follows: SimPlant™ = 273; DICOM = 114; i-CAT/i-Vision = 14; NobelGuide = 3. All DICOM cases, except for the 3 requested for NobelGuide, were imported into VIP software by Implant Logic Systems. When no request was made for a specific software format, then prints or film were printed in SimPlant™ format, but these numbers are not counted as specific software requests. The total number of requests + prints + film exceeds 500 patients since some doctors requested studies in multiple formats (Figure 6).

Figure 6. CT studies for the most common 3D third party software requested was SimPlant™, followed closely by DICOM used specifically for VIP software by Implant Logic Systems.

Over the years, SimPlant has issued many different versions of its 3D dental implant software. As a SimPlant™ Master Site, it was noted that dentists did not install each new version as they were released. Most of this study was compiled just before version 11 was released. As a result, of the 273 studies in SimPlant™, the following versions were requested: version 8 = 19; version 9 = 130; version 10 = 105; version 11 = 12; SimPlant viewer = 7 (Figure 7).

Figure 7. Demonstrates the proportion of the different versions of SimPlant™ requested.

Radiographic Guides. One hundred and eight patients (108) had radiographic guides fabricated by their dentists that were inserted during the CT scan. These guides helped pinpoint” more accurate dental implant placement, while reducing surgical risks. Of these, 3 were for NobelGuides. Patients presenting with guides = 21.6%.

Sir Godfrey Newbold Hounsfield conceived of creating a radiological (CT) machine to create cross-sectional views in 1967. In 1972, Hounsfield introduced the first Computed Tomographic scanner; CT reconstruction software dedicated to dental diagnostics has been available since the 1980s. This software, known as the DentaScan, enabled multi-planar views of the CT data into axial or occlusal, panoramic-like or coronal, and sagittal or cross-sectional images of either arch (2-4), which aided dental surgeons in implant placement.

The next milestone for dentists in 3D CT imaging was the introduction of the NewTom 9000 cone beam volumetric scanner by QR Verona in the late 1990s (10). This scanner received FDA approval in the United States in April, 2001. Unlike a medical scanner, the NewTom 9000 was designed specifically to image the maxillofacial region. The patient exposure effective dose is 50 µSv which is significantly less than a high-resolution medical CT scan and similar to that of a dental periapical full-mouth series.13,14 Since then, there has been a proliferation of manufacturers (the most notable was Imaging Sciences Inc., Hatfield, PA) introducing similar 3D cone beam CBVT scanners to the marketplace that took the scan with the patient sitting in a chair rather than lying on a gurney. In time, a host of 3D software vendors (Materialise, Glen Burnie, MD) entered the marketplace that enabled DICOM files created by these scanners to be imported into their respective software. Software frequently used for dental implants include NobelGuide™ by NobelBiocare, VIP™ by Implant Logic Systems, SimPlant™ by Materialise, and In Vivo™ by Anatomage. In orthodontics, Dolphin Imaging™ by Dolphin, SureCef™ etc. are also available.

As with other clinical innovations, common usage lags behind its introduction to the profession. This is true of dental implants, where market penetration is estimated to be in the range of 4-8%. Likewise, the utilization of diagnostic 3D imaging lags behind the long-time accepted use of 2D imaging of dental periapical and panoramic films, in spite of the fact that these images can be distorted (11). As such, the increased utilization of 3D diagnostic imaging is arguably becoming the standard of care when it comes to pre-surgical analyses of complex dental implant treatment plans (12).

In the present study 500 consecutive patients, referred by 110 different dentists, were evaluated as to their age, gender, and reason for being referred to a dental 3D imaging center that utilizes a CBVT (cone beam) scanner. Forty-four (44%) percent of the patients referred were male; 56% were female. Patients ranged from 15-102 years of age, with an average age of 56.7 years. Younger patients were most often referred for orthodontic reasons, to evaluate impacted teeth, or were post-orthodontic and were being evaluated for sites of congenitally missing teeth for implant placement, most often for missing maxillary lateral incisors.

The single reason for the vast majority of patients, 451 or 90.2% referred was for dental implants. Other reasons for CT scans included: evaluating impacted teeth (4%); pathology (2%); endodontics (1.4%); orthodontics (0.8%); TMJ disorder (0.2%) and 7 patients were referred for unknown reasons (1.4%).

Referrals for single arches – maxilla (40.8%) versus mandible (43.4%) - were similar, while 15.8% or 79 patients were referred for 3D CT cone beam scans of both arches.

There was diversity in how dentists wanted to receive the CT 3D dental studies. 512 different formats were requested: transparencies, glossy prints, studies on a CD or to receive the study via the Internet. Twelve dentists required multiple formats. The format dentists most preferred was CD (47%), followed by the Internet (34%). Glossy prints (11%) and 8 x 10 transparency format (8%) were the least requested. It should be noted that most of the Internet requests were for DICOM studies and were made by dentists using VIP™ software by Implant Logic Systems or SimPlant™ by Materialise. Those dentists, or a member of their staff, who were comfortable using the Internet had web access in their offices and took advantage of the speed, efficiency, and benefits of Internet transmission.

The most common third party 3D dental software used by dentists in this study was SimPlant™ (54.6%). One hundred and fourteen (114) DICOM images (22.8%) were requested, which were converted into VIP™ or NobelGuide™ software; 14 studies (2.8%) were requested for either i-CAT or i-Vision™ (by Imaging Sciences, Inc) and 3 studies (0.6%) required 2 scans for NobelGuide™ by NobelBiocare. The more common usage of SimPlant is not surprising since there are many SimPlant Master™ sites in the New York tri-state area and dentists have been accustomed to using this software for many years. The relatively high request for DICOM images was a function of geography due to the popularity of VIP software in the Brooklyn/Long Island area. While the different 3D dental software usage has been consistent in this study over a long period of time, regional trends may dictate which studies are requested from different CBVT radiological labs.

SimPlant™, long the established leader in 3D dental software, issues new versions of their treatment planning software frequently. Yet, the experience at this SimPlant Master Site indicates that dentists do not install the latest version when it is first received. While some dentists do install it immediately, many wait when they are comfortable with the present version they are using or, perhaps, they choose to wait to make certain “bugs” are not discovered by other users before they install it in their systems. Consequently, 19 studies were processed in version 8, while versions 9, 10, and the recently issue v. 11 were more commonly used. Since the data was collected, SimPlant™ version 12.0 has been issued.

The most unexpected finding of this study was that 108 or 21.6% of all patients referred for 3D CT scans came with radiological guides to be worn during the scan. These guides used gutta-percha, barium sulfate, or medical ball bearings as markers to be seen on the CT scans to help guide the dentist in interpreting where dental implants should be inserted. There was no attempt to determine how many surgical guides were created from the data in this study.

The results of this study demonstrate that while dentists use 3D cone beam imaging predominantly for dental implants, patients are referred to help diagnose and treat other dental entities. Future articles compiled from this data will report on the incidence and location of the lingual artery inserting into the mandible, measurements and observations about the extension of the inferior alveolar canal anterior to the mental foramen, the incidence of bifid canals, the incidence of sinus pathology, and the identification of incidental findings other than the reason for the CT referral including impacted teeth, periapical radiolucencies, pathologies, retained roots, and more.

A study of 500 patients referred to i-dontics dental radiological centers for 3D cone beam (CBVT) studies indicated the majority of patients were referred for pre-surgical analyses for dental implant insertion. Other reasons include impacted teeth, orthodontic problems, and a variety of oral and dental pathologies, recalcitrant endodontic lesions, and TMJ disorders. A significant number of patients (21.6%) presented with and wore radiological guides during the CT scan.

Acknowledgements: Support for this study was generously given by NobelBiocare 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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