Written by Jack S. Roth, DDS Monday, 07 February 2011 13:54
With this article, we begin a 2-part series highlighting the utilization of cone beam imaging into 3-dimensional (3-D) endodontics. As an endodontist, teacher, and lecturer for more than 25 years, never has the specialty been this exciting or rewarding. Diagnosis, treatment planning, and implementation of therapy has taken on a broader perspective. With this newer ability to image in the third dimension, endodontists can return to the multidisciplinary forum, offering an evidence-based approach to patient care. No longer will anecdotal information be an acceptable methodology in diagnosing the restorability on any abutment.
This evidence-based approach will be discussed and expanded upon, bridging the gap between endodontics and implantology. In previous generations of care, endodontics was enhanced by illumination, magnification, and, of course, nickel-titanium instrumentation. With the advent of cone beam computed tomography (CBCT) into the specialty, visualization and interpretation have taken on a new dimension. Endodontics has truly represented the specialty ingrained with an approach that could only be successful in the third dimension. The problem, of course, was that irrigation, instrumentation, and ultimately obturation was judged with 2-dimensional (2-D) radiography. Even digital radiography is 2-D. In my way of approaching this new arena, cone beam imaging is analogous to virtual flapless surgery in the third dimension and can be viewed over and over again well before treatment is ever rendered.
IMAGING IN THE NEXT DIMENSION
Let's be clear: CBCT is not a replacement for conventional radiography.1 My expectations are that traditional 2-D imaging will always be an acceptable first choice in the diagnosis and treatment of dental pathology. However, cone beam imaging is now becoming a complementary technology and in many instances a necessary part of the diagnostic armamentarium in endodontics as well as other areas of dentistry. This technology offers surprisingly low amounts of absorbed radiation2 while offering information never before available in clinical practice.
As we all know, accurate diagnosis is the key to quality treatment planning. With an ever-aging population, more complex dental issues are arising, affecting all dental specialties. Even ideas about the restorability of an individual tooth has led to controversies in treatment objectives. In the next part of this article, we will explore these issues in more depth and try to gain an appreciation of how CBCT has created a major paradigm shift. In effect, choosing endodontic therapy or implant placement will be driven by parameters that can be clearly verified and predicted.
For now, let's focus on the various roles of cone beam imaging in endodontics. The entire field of CBCT in dentistry is less than a decade old, with the US Food and Drug Administration approving the first CBCT unit in the United States in March 2001.3 Since then, there has been an explosion of companies coming to market as well as a learning curve for quality information to be utilized properly at the primary care level, namely in general practice. It is paramount at the primary care level that restorative dentists fully understand the implications and vast benefits that 3-D imaging brings to their practice. It is at this level that appropriate referrals and interdisciplinary dialogue can then take place. As an endodontist, utilizing the best technology to better analyze and predict success can only offer the restorative dentist the best data to then deliver optimum care. It is clear in endodontics that several factors are paramount in choosing cone beam imaging in their practice:2
- Incorporating quality new information not available by other modalities
- Reducing absorbed radiation to the patient
- Highest resolution possible
- Multiple fields of view (FOV).
All of these issues can be resolved by the latest generation of hybrid cone beam units which are multimodal in nature. They combine small and medium FOV with a digital panograph. Companies such as, but not limited to, Planmeca Promax, Vatech Picasso Duo, and Kodak 9000 manufacturer technology that fulfill these criteria. All have reduced radiation to the patient at the smallest FOV with extremely high resolution to differentiate structures at the smallest level. There is an inverse relationship between FOV and resolution. Therefore, resolution increases dramatically as FOV decreases. This higher resolution image becomes intimately involved in diagnosing pathology in and around and individual tooth. As the periodontal ligament is approximately 0.2 mm, resolutions that are now well below that level can help the clinician accurately access periodontal disruptions from apical periodontitis, periapical pathology, fractures, and other pathology.
In my own endodontic practice utilizing a Vatech Picasso Duo CBCT at a reduced 50 mm x 50 mm FOV, resolution can be as low as .08 mm (voxels) with an approximate effective dose as low as 25 µm Sv. In essence, focused small-FOV imaging allows for highly accurate, case specific information that cannot be achieved by any other noninvasive modality. In less than 2 to 3 minutes, a clinician can incorporate this information in an evidence-based approach to patient diagnosis and care.
There are multiple glaring examples of this utilization in endodontic practice. We were all taught in dental school that periapical pathology (PAP) could only be seen on standard radiographs if there was 35% bone loss and perforation of the cortex. Lesions in cancellous bone could not be detected by radiographs. These classic studies by Seltzer and Bender4,5 in the 1960s dramatize the shortcomings of 2-D radiography. Cone beam imaging has no such limitations and can easily see pathology that is totally encased in cancellous bone. Extrapolating this information into clinical practice allows general dentists and endodontists the ability to treat lesions earlier before bone deterioration has escalated. Studies have also shown that CBCT can detect periapical pathology more accurately than periapical films or panographic radiographs. Estrela, et al6 showed that in a population of > 1,500 teeth with endodontic disease, the prevalence of this pathology visible on radiographs was only 17%, panograph 35%, and on CBCT 63%. This clearly demonstrates the powerful impact cone beam imaging can have on endodontic diagnosis.
CLINICAL CASES MAKE THE POINT
|Figure 1a. Dexis: Tooth No. 19. No apparent radiolucency, evidence of intact periodontal ligament.||Figure 1b. CAT scan: Cone beam computed tomography (CBCT)/coronal view reveals large circumscribed lesion periapically.|
|Figure 2a. Dexis: Pre-op radiographs with inconclusive evidence of exact location of apical lesion adjacent to teeth Nos. 11 and 12.||Figure 2b. Dexis 2 (See Figure 2a).|
|Figure 2c. CAT scan: CBCT verifies no radiolucency apical to No. 11.||Figure 2d. CAT scan 2: CBCT/Sagital view differentiates lesion to apex No. 12.|
|Figure 2e. CAT scan 3: Axis rotation on CBCT illustrates second unfilled palatal root No. 12.|
The following case is an example of this. In Figures 1a and 1b a patient presents with pain lower left quadrant. Standard radiographs cannot differentiate any pathology. However, by using CBCT technology, we can observe a periapical radiolucency that is completely encased in cancellous bone.
CBCT also allows for better diagnosis of vague pain where multirooted teeth are involved. Cone beam imaging can isolate each root 3-dimensionally when exploring for pathology. It has no 2-D limitations (ie, overlapping roots of adjacent teeth, or bony obstructions).
In another case example (Figures 2a to 2e), a patient presented to the restorative dentist in severe pain with swelling directly over the canine (tooth No. 11). An incision and drainage was performed and, a week later, swelling still existed over tooth No. 11. That dentist was prepared to perform root canal therapy on this canine, but instead he referred the case for an evaluation. Figures 2a and 2b seem to show possible PAP around tooth No. 11, but a CBCT exam (Figures 2c to 2e) clearly show the source of infection from a missed second root on tooth No. 12 with a large radiolucency.
Internal and external resorptive defects have traditionally been perplexing to diagnose, especially in predicting prognosis. Two-dimensional radiographs even with multiple views lack enough information to determine an exact location of the lesion or even if a perforation exists. CBCT offers a unique opportunity to visualize these defects prior to initializing endodontic therapy or surgical interventions.
|Figure 3a. Dexis: Standard radiograph-evidence of internal/external resorption.||Figure 3b. CAT scan: CBCT-multiple axis views reveals advanced resorptive defects.|
|Figure 3c. CAT scan: CBCT/axial view verifies perforation.||Figure 3d. CAT scan: Further CBCT analysis determines tooth to be nonrestorable.|
|Figure 4a. Dexis: Tooth No. 8 H/o RCT-midroot radiolucency.||Figure 4b. CAT scan: CBCT pinpoints location exactly to a perforation on the direct palate at and below crest of bone.|
Figures 3a to 4b represent 2 such cases where CBCT played an integral part in diagnosis and treatment planning. In Figures 3a to 3d, a routine radiograph of tooth No. 30 clearly shows internal resorption but does not reveal its extent. A CBCT dramatically verifies this tooth to be perforated and nonrestorable. In Figures 4a and 4b, vague pain on the palate near this central incisor clearly demonstrated a midroot radiolucency. However, cone beam imaging determined its exact location on the direct palate at, or below, the crest of the bone.
Prior to the proliferation of implant dentistry approximately 25 years ago, diagnosing root fractures (vertical, horizontal, oblique) took on immense importance. Verifying a clear fracture would ultimately lead to an extraction and a 3-unit bridge or removable denture. However, standard protocol for craze lines seen internally under an old restoration never lead to an abutment being deemed nonrestorable and extracted. Traditionally, if indicated, endodontic therapy leads to a high percentage of success in these cases. In recent years, some practitioners have "lumped" crack and craze lines together and labeled them both not worthy of effort to save. Anecdotal evidence was used as a reason for extractions and implant placement as the treatment of choice. Clearly CBCT offers all dentists the opportunity to visualize this dilemma and then differentiate and categorize between true cracks or craze lines properly. A multidisciplinary approach can then be utilized to manage that particular patient's treatment alternatives.
|Figure 5a. Dexis: Standard radiograph suggestive of horizontal root fracture.||Figure 5b. CAT scan: CBCT exam fails to verify root fracture.|
|Figure 5c. CAT scan: CBCT evaluation does reveal periapical pathology apical to No. 12.||Figure 5d. Dexis: with correct diagnosis endodontic therapy was performed.|
|Figure 6a. Dexis: Standard radiograph, evidence of apical radiolucency, but also suggestive of "shadow" under crown—no clear diagnosis.||Figure 6b. CAT scan: CBCT axial view illuminates vertical fracture.|
|Figure 6c. CAT scan: CBCT-sagital view confirms vertical fracture.|
Figures 5a to 5d represent a case in which a patient presents with severe pain and mobility and was told that tooth No. 12 had a horizontal fracture and should be extracted. CBCT imaging from 360° verified no horizontal fracture, but clearly shows PAP in cancellous bone not visible on standard radiography. Endodontic therapy was performed.
Figures 6a to 6c represent a case where a patient presented with pain on tooth No. 18. A standard radiograph showed evidence of apical radiolucency and a "shadow" under the crown. Cone beam imaging clearly demonstrated a vertical fracture from several views, prior to initiating any treatment.
|Figure 7a. Dexis: Pre-op radiographs Tooth No. 3 had no evidence of endodontic involvement or clinical evidence of palatal swelling.||Figure 7b. Dexis: (See Figure 7a).|
|Figure 7c. CAT scan: CBCT multiple views verifies no endodontic pathology.||Figure 7d. CAT scan: CBCT axial views demonstrates site of palatal swelling to be nonodontogenic and separate from No. 3.|
CBCT is also extremely valuable in differentiating odontogenic from nonodontogenic lesions. Figures 7a to 7d represent a case referred for endodontic therapy due to palatal swelling around a maxillary first molar. This tooth was found to be vital, and CBCT revealed the lesion was completely nonodontogenic and the patient was referred for biopsy and further treatment.
It is clear, as with all new technologies, growing pains are imminent. CBCT is not a replacement for sound diagnostic and ethical standards of care. However, used prudently and in a case-specific manner, cone beam imaging has proven to be an indispensible tool in a multidisciplinary approach to patient care in endodontics. In part 2 of this series, we will further explore how CBCT is elevating care to a higher level.
- The SEDENTEXCT project. Radiation Protection: Cone Beam CT for Dental and Maxillofacial Radiology. Provisional Guidelines (v1.1 May 2009). sedentexct.eu/system/files/sedentexct_project_provisional_guidelines.pdf. Accessed on October 26, 2010.
- Ludlow JB, Ivanovic M. Comparative dosimetry of dental CBCT devices and 64-slice CT for oral and maxillofacial radiology. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008:106:106-114.
- Scarfe WC, Levin MD, Gane D, Farman AG. Use of cone beam computed tomography in endodontics. Int J Dent. 2009;2009:634567. hindawi.com/ journals/ijd/2009/634567.html. Accessed October 26, 2010.
- Bender IB, Seltzer S. Roentgenographic and direct observation of experimental lesions in bone: I. J Am Dent Assoc. 1961;62:152-160.
- Bender IB, Seltzer S. Roentgenographic and direct observation of experimental lesions in bone: II. J Am Dent Assoc. 1961;62:152-160.
- Estrela C, Bueno MR, Leles CR, et al. Accuracy of cone beam computed tomography and panoramic and periapical radiography for detection of apical periodontitis. J Endod. 2008;34:273-279.
Disclosure: Dr. Roth reports no disclosures.
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