For more on this topic, go to www.dentaleconomics.com and search using the following key words: CBCT, cone beam, Dr. Steven Guttenberg, American College of Oral and Maxillofacial Surgeons, Dr. Jeff Dalin.
Dr. Dalin: It is time to talk 3–D cone beam scans with Dr. Steve Guttenberg. When I think 3–D cone beam scans, I think high–resolution, high–definition, in–office CT scans that use less radiation than traditional CT scans and are designed for the dental profession and our needs. Describe for our readers exactly what we are talking about here. Many are still confused about the differences between this and a traditional panoramic unit.
Dr. Guttenburg: One of the major differences between a panoramic unit and a cone beam computed tomogram (CBCT) is that the cone beam has the ability to reconstruct the images in three dimensions, whereas the panoramic can only give us a flat plane result. The CBCT allows us to receive a volume of information that can be formatted in an infinite number of ways depending on the requirements of the practitioner and the patient. It differs from the medical spiral CTs in that the radiation dose is far less, the cost is far less, and you can't beat the convenience factor.
Dr Dalin: Let's now look at the different uses of this technology. First, let's look at third molars. I know that I recently sent a teenage patient to a nearby periodontist who has an I–Cat unit for a scan of his third molars. I was concerned about the proximity to the mandibular nerve and his parents were very hesitant to go through with any surgery until they could understand paresthesia risks better. After the scan, it was determined that the risk was very low, unlike how it appeared in the panoramic image. Third molar removal went on as planned with no aftereffects. I guess there are countless examples of this.
Dr. Guttenburg: We frequently see patients similar to what you just described. Visualization of the inferior alveolar nerve canal is very relative when viewing it in two dimensional films such as periapical and panoramic radiographs. It is of tremendous benefit to be able to make cross–sectional X–ray cuts of the jaw and determine the true anatomic position of the nerve canal in relation to the roots of teeth and other structures.
Dr. Dalin: I can easily see the use of this technology for third molars. Let's look at a second important use: implant placement. Let me tell you another patient story. I had a patient who lost tooth No. 29. We wanted to place an implant, but the surgeon could not guarantee no postoperative paresthesia issues due to the mental foramen being in the area. He told her he was about 95% sure everything would be OK. She does public speaking and this small risk was still too high for her. She was going to go with a fixed bridge until I had a scan done. It showed that there was no reason for any worry whatsoever, and she went through with the implant.
Dr. Guttenburg: My original impetus for purchasing a CBCT was to assist in the complete evaluation of a site to accept a dental implant. It allowed me not only to appreciate the true location of the inferior alveolar nerve canal and the mental foramen, but also the maxillary sinus and the true proximity to the incisive canal, adjacent teeth, and nasal floor. Plain films allow only the ability to judge the height of the alveolus, but with CBCT I was able to get complete information to a hundredth of a millimeter of not only the alveolar ridge height but also of its width. The CBCT also allows us to appreciate the morphology of that ridge. These are all extremely important factors to have in one's command prior to implant placement.
Dr. Dalin: Would you like to talk about how useful 3–D cone beam images are when dealing with patients with temporomandibular dysfunction problems?
Dr. Guttenburg: CBCT allows us to completely evaluate the osseous component of the temporomandibular joint. We can appreciate whether there are surface or deep bony abnormalities, and we can clearly visualize the complete range of mandibular movement. It helps us to determine if the patient's problem is due to bone pathology, or whether their dysfunction is seated in the soft tissues or dental component of the system.
Dr. Dalin: Steve, I would now like to discuss the dilemmas many dentists experience when struggling with whether or not to purchase one of these units. We can all see the advantages of these scans as far as avoiding postoperative paresthesias and placing implants in poor locations or poor positions. We would all love to have this information in advance to avoid liability problems. This makes us all want to go out and purchase one of these machines. But now we are hearing about liability insurance carriers worried about dentists not interpreting all of the data that is available on these scans; i.e., missing some sort of medical problem. We are being told that we would need to have all of these images read by a radiologist or we might not be covered for liability in this manner. This idea frightens off those who are considering purchasing one of these units. I know that the manufacturers are now designing the software in a way that limits the field that we are examining. Can you discuss these issues to help move readers through this predicament?
Dr. Guttenburg: Your question is a good one and it raises some controversial points. There are a couple of dental–savvy attorneys, well known to our profession, who point out that dentists cannot be held responsible for not identifying diseases that are outside the scope of our licensure and training. For example, dentists cannot diagnose intra–cranial carotid calcifications by virtue of their dental licensure.
On the other hand, there is a small group of dental radiologists who feel that every film must be evaluated completely to identify all possible abnormalities. A question that I raise regarding this issue is: “Does every dentist who takes panoramic radiographs evaluate every iota of it, looking beyond the teeth to evaluate for orbital, sinus, or spine and neck pathology, and has it led to an increase in litigation?” I don't think so.
Obviously, all practitioners should become familiar with the normal anatomy of the region that they are examining and should feel free to refer radiographs they are not comfortable with to a qualified oral and maxillofacial radiologist for consultation. I know some CBCT owners who have all of their studies so evaluated. The same attorneys that I referenced at the beginning of this response also point out that, in this day and age, not utilizing CBCT to place dental implants borders on malpractice.
Dr. Dalin: I know there are a number of different units out there. To name just a few: I–Cat, Iluma, Promax 3D, Kodak 9000, Gendex GXCB–500, Galileos, Scanora, Suni 3D, and Picasso. If I am ready to look at the large number of choices available, what features, characteristics, and questions should I consider when I talk with the different manufacturers?
Dr. Guttenburg: I would critically evaluate the quality of images produced by each machine and see which you prefer. Are these images made from living patients or from skulls in a laboratory?
If you are merely interested in the dentition and surrounding structures, evaluating CBCTs with a small or medium field of view makes sense. However, for oral and maxillofacial surgeons, orthodontists, some medical specialists, or others who might want to evaluate the full facial skeleton, the large field of view is a must. Also, those who treat facial trauma, TMD, airway issues like sleep apnea or snoring, or oral and maxillofacial pathology will benefit from large field of view machines.
Different manufacturers have machines which can take longer to reconstruct images, and that should be taken into account if you have an active practice.
Radiation dose is another factor to take into consideration. Generally, the lower the dose, the better.
I think it is important to check out the history of the company that is selling the machine. Does the company and the machine have a good track record? How long has the company been in business? How will the product be serviced, etc.?
And finally, the cost must be evaluated. However, even though having a CBCT in one's practice generally produces a positive cash flow, the important thing to consider is that the benefits to the practitioner and patient care are the real issues, and having a cone beam is another way that we can better treat our patients.
Dr. Dalin: Thank you for taking the time to talk with me today. I am sure that our readers will now have a much better understanding of this technology and how to use it. Is there anything else you want to talk about?
Dr. Guttenburg: I am honored to have been asked to comment on cone beam CT. It has had a significant positive impact on my ability to properly care for patients. I cannot imagine practicing without this technology.
Steven A. Guttenberg, DDS, MD, is a board certified oral and maxillofacial surgeon who practices in Washington, D.C. He is director of the Washington Institute for Mouth, Face, and Jaw Surgery. Dr. Guttenberg teaches at the Washington Hospital Center and is a sought–after lecturer. He has written numerous scientific articles and book chapters. Contact Dr. Guttenberg at [email protected].
Jeffrey B. Dalin, DDS, FACD, FAGD, FICD, practices general dentistry in St. Louis. He is a cofounder of the Give Kids A Smile program. Contact Dr. Dalin at [email protected].
