Technology

Improving Precision With CBCT Imaging

Dentistry Today January 6, 201113 Mins read2.4k Views

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INTRODUCTION
I have actively utilized computed tomography (CT) technology for more than 20 years in implant and regeneration treatment planning, beginning with hospital-based axial tomography and, during the past several years, exclusively utilizing cone beam CT (CBCT). Before the use of in-office CBCT scans, patients needing reconstructions or implants were sent for medical CT. Unfortunately, the patient was exposed to the increased radiation of axial CTs, inconvenienced by an additional appointment, and subjected to the higher costs of that type of scan.1 Measurements obtained through a 3-dimensional (3-D) scan are very accurate; however, films from the medical CT were often cumbersome, difficult to cut and piece together to obtain necessary information, and incompatible with other imaging software. Sometimes, in the middle of a surgery where no 3-D image had been exposed preoperatively, the practitioner would discover that a CT scan would have been of great help. All that has changed since implementation of in-office CB imaging.
Before I invested in a CB scanner, I was referring my patients to a nearby orthodontist who utilized i-CAT CBCT scans. I realized how many cases I was referring out of my own office, so when the GXCB-500 (Gendex) became available, I was eager to make that investment. The medium field of view is perfect for my periodontal needs. I do not need a full-skull view for my implant and periodontal cases, and I can still do airway studies for those who practice “sleep dentistry.” For those rare occasions when I need full-skull images, I have the ability to stitch together 2 scans with the Anatomage software application. The scans are easy to capture; in fact, my staff and I feel that it is easier to take a CB volume study than a conventional panoramic image. In the GXCB-500, the patient is seated, facing forward; the marking lights on the face show up better (Figure 1), and the image preview feature lets you know that you will be capturing the right area. Actually, the image capture time of 8.9 seconds² is 2 seconds faster than a conventional 2-dimensional panoramic scan. As a result, I get more information with less effort, with greater benefit to the patient.
The successful results obtained in the following case example were facilitated by the ability to see the details discovered through CB imaging.

CASE REPORT
A female patient presented with bilateral edentulism distal to teeth Nos. 4 and 13. The patient was requesting implants on each side. In order to provide dental implants, lateral-wall sinus lifts were required because the bone height was inadequate to support implants either with bone in situ or with osteotome lifts. I ordered a standard i-CAT of the maxilla (before I had my own scanner) to determine the bone and sinus dimensions (Figures 2 to 3b). The scan was captured at 14 cm diameter, and then collimated down to 4.3 cm to gain the maxillary arch and sinus (Figure 4). (Collimation is a narrowing of the height at the radiation source, a feature that is also available with my medium field of view system.)


Figure 1. Simple and straightforward capture of scans.	Figure 2. Axial view with coronal slice taken in the No. 3 and No. 14 areas; note the inadequate bone height.

Figures 3a and 3b. (a) Consecutive cross sections in the No. 3 position. (b) Consecutive cross sections in the No. 14 position.


Figure 4. Initial 14 cm x 4.3 cm scan collimated 3-dimensional scan used for treatment planning.	Figure 5. Postoperative scan; note graft axillary right.

Figure 6. Postoperative scan show successful grafting and ideal bone height for implant placement.	Figure 7. Postoperative intraoral radiographs.

After imaging, we had a consultation to decide the course of treatment. One option would have been a removable, bilateral free-end appliance. Thankfully, she had no interest in that since the distal aspects of those appliances tend to fall down because of gravity, and the teeth that hold the clasps are subject to a tremendous amount of stress. It was decided that we would perform lateral wall sinus lifts, to be followed by implants; one side at a time.
An antibiotic (Augmentin, 875 mg twice a day) was prescribed, beginning the day before treatment, through the first 9 days of healing. She was also placed in a nightguard to protect the remaining dentition.
A sinus lift was performed on the upper left under local anesthesia. The precise location of the surgery was determined based upon measurements from the CBCT scans. A mid-crestal incision was designed in the edentulous area with anterior and posterior vertical releases. A piezosurgery device (the Mectron Piezosurgery Unit from Milan, Italy, which is distributed in the United States by Piezosurgery) was utilized to create a window, and the membrane was lifted with manual curettes through to the medial wall with sound bone inferiorly, mesially and distally. She was grafted with 2 ccs of Puros (Zimmer Dental) large particle cortical bone blended with 2 ccs of Bio-Oss (Osteohealth) cortical bone for a total of 4 ccs of bone using a syringe and standard sinus pluggers. A Bio-Gide (Osteohealth) membrane was trimmed and placed on the window, and the flap was closed using 4-0 Vicryl sutures (Ethicon). A small perforation at the mesial aspect was discovered on the postoperative scan and was determined to be of no clinical significance. Then, the next month, the right side was treated, using 100% Puros, and a Bio-Gide membrane (with the same volume of bone) and the same suture technique as on the previous side.
The postoperative period was uneventful. The patient experienced minimal discomfort and very little swelling. An 8-x-8-cm, low-dose scan was acquired (Figure 5) to verify the success of the grafts and to plan for the implants. Once ample time had elapsed for the grafted bone to mature, a single Biomet 3i Prevail implant was placed on each side (Figure 6). The Nos. 3 and 14 implants were placed simultaneously, using information taken solely from the CBCT scans for implant planning.
The patient is currently contemplating an additional implant on each side. Intraoral radiographs demonstrating complete osseointegration at 8 weeks post-implantation are shown (Figure 7).

Technical Implications of CBCT Technology

Lou Shuman, DMD
As children, many of us wished for the same x-ray vision powers that enabled Superman to be a legend. As a result of seeing beyond the surface, he could avoid possible dangers and perform heroic acts, unlike those of “mortal men.” If Superman’s powers wowed us on the 2-dimensional (2-D) screen, imagine how much better they would be in this age of 3-dimensional (3-D)!
Before 3-D imaging, or cone beam computed tomography (CBCT), was available in the dental office, patients needing certain procedures were sent to hospitals or other imaging centers for medical CT scans. Important differences between these scanning methods make cone beam a safer, more convenient, and less costly option for dental patients. In the diagnostic category, The Pride Institute has recognized the Gendex GXCB-500 HD for its “Best in Class” Technology Award for 2010. This is in part due to its i-CAT-powered system, flexibility in 3-D scan sizes, inclusion of a traditional 2-D pan, and integration with CAD/CAM applications.

How It Works
A dental CBCT scan is captured in one single rotation around the patient. The beam is cone-shaped, taking scans in as little as 8.9 seconds, and then reconstructing them in less than 20 seconds in some machines. Images are ready to be viewed nearly immediately. In comparison, the medical CT emits a fan-shaped beam that travels in several revolutions around the patient’s head, overlapping radiation in the process of gathering its data.
Another advantage is CB’s flexibility: Dr. Schwartz’s medium field of view has multiple scan sizes and also takes a 2-D pan. Due to adjustable collimation, the resulting various image sizes suit radiographic needs for many different procedures and the specific needs of individual patients. Scan sizes range from single-arch view, to medium field of view, to cephalometric.

Terminology That You Should Know
Collimation: The adjusting of the beam at the radiation source that creates varying sizes of images; the smaller the scan size, the less radiation for any given voxel size.
Voxel: The 3-D equivalent of a pixel; the smallest sub-unit of a CBCT volume. This relates to resolution and exposure.
Hounsfield units (HU): A quantitative measure of the radiolucency of different materials in a CAT scan. These units allow for differentiation of the relative densities of various biological structures so HUs are involved when assessing the bone density of the potential implant site.
Microsievert (Sv): An international unit used to measure effective dosages of radiation.

Observed Benefits
Observation of Vital Structures: A 3-D scan offers a view of bone structure and tooth orientation, nerve canals, and pathology. For implant procedures, having information such as precise width and depth of bone, exact tooth locations, and alveolar nerve identification can boost success rates and avoid possible surprises or complications during surgery. In some cases, a scan can eliminate the need for exploratory surgery, which makes both doctor and the patient happy.
Reduced Radiation Exposure: With the emphasis on as low as reasonably achievable levels of radiation protocols, CBCT can fulfill the quest for obtaining the most comprehensive data for proper diagnosis with minimal radiation for that type of radiography. With an in-office CBCT, radiation exposure to the patient is up 10 times less than a regular CT scanner. I encourage our readers to explore research data on radiation levels for CBCT machines. Significant research can be found in the Ludlow, et al study from 2008. Please refer to umn.edu/perio/dent8101/W3_Ludlow.pdf for more information, and pay special attention to Table VII, which provides an excellent comprehensive survey of different units. Radiation levels can be reduced or adjusted by either utilizing different fields of view—or collimating, depending upon the machine.
More affordable: For the patient, the average charge for an in-office CBCT scan could be up to 50% less than a medical CT scan.
More convenient: An in-office imaging method saves the patient travel time and gas money from trips to and from the hospital or imaging center and eliminates extra office visits.
Versatile: Scans are compatible with many kinds of treatment planning software, for applications such as virtual teeth placement visualization and implant proximity detection.
Facilitates communication: DICOM 3 compatible images are easily exported into a wide variety of 3-D imaging software programs, many allowing for CAD/CAM applications. Vivid 3-D renderings make it easy for patients to understand diagnosis and possible treatment plans. Scans also can be electronically sent to referring dentists, specialists or patients, efficiently and securely.

Potential Challenges and Other Observations
While some dentists prefer to have a radiologist review scan data, others prefer to read their own. As with any new technology, dentists should seek as much education as they need to comfortably practice with that technology. Opportunities for training abound, such as the 3-D Imaging Institute (i-cat3d.com); webinars; and local, regional, national, and international seminars.
While insurance companies are in the process of integrating scans into their coverage plans, many procedures can be applied to regular medical insurance codes. As CBCT grows to become the standard of care, as it already has for some procedures, dental insurance coverage is expected to expand to include more categories specifically related to 3-D imaging options.

DISCUSSION
When performing sinus augmentation, accurate radiography is the clinician’s best guide. We must know the exact location of the floor of the sinus to determine how high up to begin the window. We also want to know the mesial and distal extents of the sinus in order to plan how far forward and how far back to treat. In addition, knowing the thickness and density of the lateral wall of bone helps us avoid a perforation of the sinus membrane. It can be misleading if the lateral wall of bone is fairly dense; a 2- or 3-mm thick dense wall of bone over the sinus on the facial aspect can lead the dentist to believe that a certain area has been reached, when in fact it has not. The CBCT scan offers precision with a clearer understanding of the surgical site (where you should be, or not be), and what to expect as you remove lateral wall bone.³
The scan also clearly demonstrates any septa within the sinus. In cases where a septum completely divides the sinus, 2 windows must be created, essentially resulting in 2 separate procedures on the same antrum. Other times, with a partial septum, much care must be taken in elevating along the floor of the sinus to ensure that the schneiderian membrane does not get torn at that point.⁴
CB scans give a dentist confidence in implant placement, and the fact that these machines are readily available is a great step forward. In addition, piezosurgery, along with proper technique, gives us the ability to cut hard tissue without damaging soft tissue,⁵ reducing the serious perforation rate from 30% (found with rotary instrumentation) to 7%, or less.⁶

CLOSING COMMENTS
As a specialist using this technology for treatment planning, I have gained more confidence for my regenerative procedures, including sinus lifts and bone grafts. General dentists can also benefit from the additional data captured in a CB scan for diagnosis of issues such as root and periapical investigation, tooth relationships, and third molar positions. As more dentists adopt this imaging modality, patients and dentists alike will surely see the advantages of adding an additional diagnostic dimension to the practice. Since my office added the GXCB-500 in April 2009, hundreds of patients referred by my restorative and orthodontic colleagues have had the benefit of more precise diagnosis, treatment planning, and surgical therapy. Frankly, I don’t know how I practiced without it in all the previous years!

Practice Management Ramifications of CBCT Technology

Amy Morgan
All technology purchases and clinical upgrades can impact a practice either positively or negatively depending upon the plan for implementation and integration. An effective plan must include:

How the team will train and master the new innovation
What adaptations to existing systems are required
How to inspire patients to respond to the new upgrade.

In this article we are looking at implementing cone beam computed tomography (CBCT) technology.
If part of your practice’s vision is to implement the very latest in technology, the following areas deserve consideration:

Implant planning that results in excellent function and aesthetics
Temporomandibular analysis
Oral surgery
Orthodontic treatment
Periodontal treatment
Assessing endodontic anomalies.

In all of these, CBCT can allow for greater precision and predictability leading to more optimal outcomes.

Costs Involved
CBCT machines can range in cost from $150,000 to $300,000. The initial cost of the new CT scan technology may be perceived as very expensive, therefore prohibiting its widespread use in many dental practices. Potential solutions include utilizing this in “multispecialty” group practices or opening its use to other general dentists and specialists in your area for an agreed upon fee.
Considering that many practitioners believe that CT scans can transform the whole patient experience, the cost of the technology can become a nonissue. Even if it does not generate profit immediately, a CBCT scanner can help to generate a steady flow of new patients who value this modern tool. To begin to create an opportunity for return on investment, the fees charged for cone beam scans can range anywhere from $250 to $600, depending on the facial region scanned, subsequent assessments performed, and who performs and interprets the scan.

Educating the Dental Team
The entire team needs to learn new skills to integrate CBCT into the practice culture. Everyone needs to learn how to explain the new technology to patients since many patients will need to have a scan as part of their thorough exam in determining a diagnosis and treatment plan.
The dentist, dental assistants, and surgical assistants will also need to learn new clinical skills to support the taking and analyzing of the scans. The CBCT will come with training package options. The doctor should also plan on investing time and money in additional training seminars as there can be concerns about inadequate training of individuals making and interpreting CB images. Of course, there will be an increased level of stress while all the “key players” are getting up to speed (gaining competence and confidence) in fully utilizing this state-of-the-art technology. There is a definite learning curve, especially for the clinical staff who need to learn how to position the patient, how to export and break apart the scan, how to explain the procedure to patients, etc. Team members who are very comfortable with computers will master the skills needed for this technology much more quickly.
The implementation of CBCT will impact every area of the office:

Additional time has to be scheduled for taking a scan.
The cost of a scan has to be added to the financial arrangements.
“Guided Navigation” templates are now used for some surgeries.

So, extra time needs to be allowed between appointments while the information is sent to the lab, and the template is returned from the lab. Plus, the way that treatment is presented to patients is different.
With that said, this is a new technology that patients will appreciate and value if its benefits are presented properly. Most patients find it reassuring to have caregivers that strive to be on the cutting edge of technology and comprehensive in their clinical approach. Some of the readily understandable benefits include:

More efficient and effective plans for treatment and surgery
Better assessment of risk
Upgraded analysis of critical structures

CT scans are noninvasive and can eliminate the claustrophobia ofa medical CT scan, therefore increasing patient comfort

Enhanced outcomes and results
Decreased radiation.

The way to spread interest in this technology in your community is through education. Everyone needs to understand the power of this technology, and how and why it is used. CT scanning provides a better clinical experience and overall, a better result both functionally and aesthetically. It also allows the doctor to create a complete treatment, including all of the costs involved; whether the plan includes ridge augmentation, sinus lifts, etc. Regular use of CBCT technology turns a 2-dimensional thinker into a 3-D thinker.

References

Howerton B. Facing the facts—dental CBCT and medical CT scans. Dental Tribune. January 13, 2010. dental-tribune.com/articles/content/id/ 1311/scope/specialities/section/general_dentistry. Accessed on: September 20, 2010.
Gendex. gendex.com/img_cpm/200_GendexUSA/media/08bro_GXCB-500-web.pdf. Accessed on: September 20, 2010.
Neugebauer J, Ritter L, Mischkowski RA, et al. Evaluation of maxillary sinus anatomy by cone-beam CT prior to sinus floor elevation. Int J Oral Macillofac Implants. 2010; 25:258-265.
Maestre-Ferrín L, Galán-Gil S, Rubio-Serrano M. Maxillary sinus septa: a systematic review. Med Oral Patol Oral Cir Bucal. 2010;15:e383-386.
Schlee M, Steigmann M, Bratu E, Garg AK. Piezosurgery: basics and possibilities. Implant Dent. 2006;15:334-340. journals.lww.com/ implantdent/Abstract/2006/12000/Piezosurgery__Basics_and_Possibilities.5.aspx. Accessed on: September 20, 2010.
Wallace SS, Mazor Z, Froum SJ, et al. Schneiderian membrane perforation rate during sinus elevation using piezosurgery: clinical results of 100 consecutive cases. Int J Periodontics Restorative Dent. 2007;27:413-419.

Dr. Schwartz is a graduate of the Harvard School of Dental Medicine and completed his periodontal residency at the Boston University Goldman School of Graduate Dentistry. He has been in private practice since 1976, and has been placing dental implants and performing regenerative procedures since 1986. He is a former clinical instructor at both Harvard University and Boston University, past scientific chair and general chair of the Yankee Dental Congress, and has also served as chairperson of the Council on Ethics, Bylaws, and Judicial Affairs of the ADA, as well as serving on the Ethics Committee of the American Academy of Periodontology. He is currently the assistant editor of the Journal of the Massachusetts Dental Society. He can be reached via e-mail at aschwartz@gumsonline.com.

Disclosure: Dr. Schwartz reports no disclosures.

Dr. Shuman is president of Pride Institute and is well known in the dental community for his leadership and expertise in the areas of strategic relations, emerging technologies, Internet strategy, practice management, and marketing. The Pride Institute’s goal is to utilize its reputation of integrity and fairness as a foundation in educating the community within the field of emerging technologies. He previously served as vice president of clinical education and then vice president of strategic relations for Align Technology for 7 years. He is a member of Dentistry Today’s Dental Advisory Board and has been listed in Dentistry Today’s Leaders in Continuing Education from 2004 to 2008, and he is currently listed as a leader in dental consulting. He can be reached via e-mail at lshumani@msn.com. Follow Dr. Lou Shuman on Google+, on Twitter (@LouShuman) or subscribe to Lou Shuman’s posts on Facebook.

Disclosure: Dr. Shuman reports no disclosures.

Ms. Morgan serves as the CEO of Pride Institute. She is a dental consultant and international lecturer. Over the years, Ms. Morgan has facilitated the successful revitalization of thousands of dental practices using Pride Management Systems. She can be reached at via e-mail amym@prideinstitute.com.

Disclosure: Ms. Morgan reports no disclosures.