Cone Beam Computed Tomography in Periodontics And Implantology

Advances in imaging technology are increasing clinicians’ capabilities in terms of diagnosis, treatment planning, therapy and postoperative assessment — and no modality has had greater impact in recent years than cone beam computed tomography (CBCT). With applications ranging from the specialties to general practice, CBCT provides three-dimensional detail that is simply unavailable with conventional imaging technology.

For perspective on how scanning supports successful outcomes, we asked noted Dallas-based periodontist and implantologist Mark E. Glover, DDS, MSD, to share insights into the utility of CBCT in periodontal treatment and dental implant therapy.

What are the upsides of periodontal diagnosis with CBCT?

The CBCT can be used as an adjunct to a full-mouth series of radiographs when additional information is needed for periodontal diagnosis. Clinicians can gain more anatomical information, such as the extent of bone loss in furcations or the presence of grooves on the roots of teeth associated with vertical defects. These are easy to see on a CBCT, but extremely difficult to interpret on a periapical radiograph. Bone loss can be tricky to diagnose, but when using all available views, this imaging modality is generally quite helpful when determining the prognosis and treatment of individual teeth.    

When should CBCT be used in planning and executing extractions?

When the tooth is positioned near vital structures — such as the inferior alveolar nerve or maxillary sinus, or even an adjacent tooth in some instances — it is helpful to learn the three-dimensional anatomy. The use of CBCT helps clinicians avoid damaging these structures during extractions.

Does CBCT represent today’s standard of care when planning and placing dental implants? What are the potential ramifications of not using this imaging modality?

Without doubt, CBCT is becoming the standard of care when planning and placing implants. Three-dimensional anatomy cannot be adequately assessed with two-dimensional imaging. Many mistakes can be prevented through the knowledge gained from a CBCT image. In my  practice, we see mistakes that might have been avoided if the previous clinician had utilized three-dimensional imaging — either by itself or combined with surgical guides — to assist in implant placement. Examples include implants placed in the mandibular or lingual fossa, implants invading adjacent teeth, and implants placed in ridges that are too narrow for the implant.

Without CBCT imaging, the operator cannot accurately define the width of bone or fabricate a surgical guide relative to the anatomical challenges of implant placement. These avoidable mistakes can have such a negative impact on patients that not taking advantage of this technology would be a shame.

Which practice settings would most benefit from a regional versus full-scan machine?

Any procedure focusing on one tooth would benefit most from regional scans, such as endodontic therapy or single-tooth implant placement. Smaller scans yield higher accuracy and greater detail. ­Diagnosing split teeth has been simplified by using regional scans, which are useful in this capacity.

Both full scans and regional scans have helped us decide when to do soft tissue grafts by allowing us to see the facial bone over a tooth. If a bony dehiscence is diagnosed with the aid of CBCT, the tooth has a higher potential for recession in the future. This can help determine which teeth are at risk for future gingival recession so proper treatment can be rendered. This technology could also be used by orthodontists to determine if expansion of an arch was the proper treatment by assessing the presence, absence, or thickness of bone facial to the teeth being moved facially.

Please discuss the issue of scatter.

Scatter affects clinicians’ ability to accurately diagnose the scan. Some scatter is obvious and occurs when numerous metallic restorations are present. Other scatter creates radiopaque and radiolucent apparitions that are not actually there. This is especially true for radiolucent outlines around some implants, which can be misdiagnosed as peri-implantitis, or around restorations in teeth that can be misdiagnosed as recurrent caries. The trick is to cross-reference data from the clinical exam, the panorex, bitewings and periapicals to help determine when to suspect that scatter on the CBCT has distorted the view.

How do CBCT calibration issues (“stitching issues”) affect clinical practice for periodontists and implantologists?

The fabrication of surgical guides to help position implants is based on the accuracy of the scans and ability of the software to stitch together the information in a useful and accurate image. Most of the studies I have seen verify the accuracy of these programs. In my experience, surgical guides fabricated from a CBCT scan are accurate and help facilitate optimal implant placement.

Who reviews the CBCT scan? In periodontal and implantology settings, is this best done by a radiologist? What are the medicolegal issues involved in reading the scan?

If providers have a question about what they are seeing on a scan, they need the assistance of a radiologist. In most periodontal and implantology settings, the clinician has the skill set to interpret the radiograph. Experience is acquired over time and judgment is developed as operators gain confidence in their ability to diagnose from the CBCT. This occurs when treating a case that has been diagnosed and planned, and in which the radiographic findings coincide with the clinical findings.

Recognizing normal anatomy — and, conversely, abnormal or pathological conditions — is key to steering clear of medicolegal issues. If the scan shows the anatomy, the clinician is responsible for knowing what normal anatomy looks like. While providers do not have to know all of the pathological entities, they must know when to refer the scan to a radiologist. The prudent clinician will review the radiologist’s interpretation to learn which findings are significant and which are not. Examples include calcified carotid arteries or abnormalities in the sinus; while these can be easily seen on a CBCT, dentists are generally not trained to recognize and diagnose these conditions.

Referrals can be made to the appropriate medical specialist if the clinician is unsure of the diagnosis. It is indeed gratifying to be scanning to place an implant and find a life-threatening condition the patient had no idea was present.   

Please briefly address what’s involved in CBCT training costs and time.

The manufacturer of the unit purchased should provide training, and the cost should be incorporated into the purchase price. Beyond that, the practice’s only cost is the time needed for team members to become proficient in scanning. Online training is also available and will improve clinicians’ ability operate the software in the most efficient manner.

While scan quality is partly dependent on the specific machine, it is also a function of the operator’s skill. A great machine and software in the hands of an inexperienced team member will yield average to subpar results. Acquiring diagnostic-quality scans and properly interpreting them are skills that must be continually developed and refined. Each patient is different and presents challenges in correct positioning, which is critical to the final result.

Any final thoughts?

Our CBCT machine is the smartest purchase we have made in the last 10 years. It is more convenient for the patient, quicker for us, and the quality is better than previously experienced with commercial labs. Simply put — and within the spirit of the as low as reasonably achievable (or ALARA) exposure principle — we use it more because it is more accessible. For example, we use it immediately after many surgical procedures, such as sinus elevation and ridge augmentation, to document the immediate postoperative extent of augmentation. These scans are compared with a CBCT taken at the final appointment, after healing has taken place. This makes us better surgeons by allowing us to compare what we have done surgically to how the body reacts during healing.

Clinicians who are contemplating the purchase of a CBCT unit should seriously consider it. If the practice volume is not high enough to purchase one at this time, offices can utilize a commercial radiology lab in the area to realize the many advantages three-dimensional imaging brings to providers and patients.

The author has no commercial conflicts of interest to disclose.

Featured image by THELINKE/ISTOCK/GETTY IMAGES PLUS

From Decisions in Dentistry. May 2019;5(5):10–12.