Written by Arthur I. Schwartz, DMD Thursday, 06 January 2011 14:33
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.
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
How It Works
Terminology That You Should Know
Potential Challenges and Other Observations
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
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
In this article we are looking at implementing cone beam computed tomography (CBCT) technology.
In all of these, CBCT can allow for greater precision and predictability leading to more optimal outcomes.
Educating the Dental Team
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.
CT scans are noninvasive and can eliminate the claustrophobia ofa medical CT scan, therefore increasing patient comfort
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.
- 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.
Disclosure: Dr. Schwartz reports no disclosures.
Disclosure: Dr. Shuman reports no disclosures.
Disclosure: Ms. Morgan reports no disclosures.
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