Dental Tribune USA

Straight talk on 3-D imaging from an orthodontist

By Dr Bradford Edgren, USA
October 01, 2009

Studies on learning have shown that visual images provide 80 to 90 per cent of the information that the brain receives. So it makes sense that in the dental office, details received from our radiological workups are imperative for precise diagnosis and communication with patients. Now, Cone Beam technology has brought 3-D imaging right into the dental office, expanding the scope of treatment for my patients as well as other dental practitioners.

The greatest benefit of 3-D imaging is the amount of information obtained from each scan. The 360-degree scan of the entire head shows the maxillofacial complex in a format that can be rotated or sliced to achieve the best view of these structures. For oral surgeons, periodontists, or general dentists placing implants, the opportunity to view the dentition from any and all of these angles is of great benefit during diagnosis and planning. My Cone Beam system has even revealed supernumeraries, cysts, and foreign objects hidden within standard radiographs.

When evaluating for implants, 3-D imaging allows the clinician to determine the height and width, as well as the quality of the bone in the implant area. Moreover, 3-D provides the ability to precisely evaluate the distance and angulation between roots of adjacent teeth to avoid damaging said teeth during implant placement.

Since implants are generally the preferred restoration for the missing single tooth, an orthodontist can scan a patient prior to debanding to determine exactly how the teeth are aligned within the bone, and make any necessary corrections. It would be very disappointing for a patient to anticipate receiving an implant and crown only to realize later that the orthodontist didn’t create enough space for the implant.

3-D imaging provides for more precise measurements than 2-D panoramic radiographs which can be unreliable because of distortion and superimposition. Cone Beam offers true 1:1 anatomical measurements, eliminating geometric errors of projection, and supporting accurate linear measurements. All of this improves surgical predictability for orthognathic surgery cases. With 3-D, I don’t have to calculate for magnification errors when determining the amount of surgical correction on these cases.


Fig. 1 Superimposed molars spotted on scan


Fig. 2 Scan saves the patient unnecessary surgery

Prior to 3-D imaging, my orthodontic diagnostic records always included panoramic x-ray, and lateral and frontal cephalograms. Now, with one scan I gain the panoramic, lateral, and frontal images, as well as everything in between. Skeletal asymmetries that may not be clearly visible on 2-D head films, are more evident with a Cone Beam scan. 3-D makes it easier to determine the buccal, lingual, and vertical position of impacted teeth.

Cone Beam imaging also helps with informed consent. 3-D scans reveal pathologies that may have become lost in 2-D images because of distortion, magnification and the superimposition of anatomical structures. I discovered a horizontal root fracture on a patient and subsequently referred him to an endodontist for evaluation. This patient needed to be aware of the likelihood that the tooth could be lost because of previous trauma. Without this insight, foreshortening of the root or even tooth loss may have been blamed on the orthodontic treatment.

For TMJ disorders, with one scan that takes just a couple of minutes, I get panoramic, frontal and lateral views as well as corrected tomographs that would have taken me an hour or more with 2-D methods.


Fig. 4 Patient educated on pathology


Fig. 5 Mysterious hearing issue

After implementing Cone Beam, I discovered some interesting cases that will be discussed in my webinar on October 17, 2009 at 11:35 am EST. In one case, we were waiting patiently for the 2nd permanent molars to erupt prior to initiating phase II treatment. After the other three 2nd molars had already erupted, as part of progress records, the i-CAT scan showed that an impacted 3rd molar was impeding the eruption of the maxillary right 2nd molar [Fig. 1]. On previous “standard” pans the fourth 3rd molar was perfectly superimposed with the 2nd molar, and was not evident. This 2nd molar may never have erupted, or worse yet presumed to be “ankylosed.”

In another example, a patient was referred from an oral surgeon for an i-CAT scan. The referring oral surgeon wanted to clarify diagnoses made at another office, based upon previous digital pans, including a supernumerary, odontoma, failure to erupt and/or ankylosed deciduous 2nd molar. On the scan [Fig. 2], it was evident that it was just an ankylosed deciduous 2nd molar, eliminating the need for a previously planned exploratory surgery. This patient also owes her future nice occlusion to 3-D imaging and diagnosis.

Our Cone Beam also gave us a great view of another patient’s horizontally impacted maxillary central incisor [Fig. 3]. When treatment started, the i-CAT machine aided the oral surgeon in exposing and placing a gold chain on the central for guided eruption. Her impacted canine, detected on the previous scan, has also since been brought into place.

Regarding patient education, an oral surgeon referred a patient for an i-CAT scan to verify the position of the mandibular canal in relationship to the impacted third and dentigerous cyst prior to extraction [Fig. 4]. This helped the patient visualize the extent of the third molar impaction and appreciate the size of the cyst. The patient was so impressed with the i-CAT scan, that he consequently set his daughter up for orthodontic treatment.

One of my most unusual cases involved a young patient who came in for braces, but after the i-CAT scan left with some clues that led to an ENT solving the mystery of her hearing loss [Fig. 5]. I’ll be discussing these cases and more in detail at my webinar. While some of these cases show hidden pathologies, it is no secret that 3-D imaging sheds light on our more difficult cases, and no matter what our specialty is, adds a new dimension to our practices.

Please register for Dr. Edgren’s live online broadcast on 17 October and earn CE credits. Register for free under www.OTStudyClub.com.

About the author

Dr Bradford Edgren earned a Doctorate of Dental Surgery from University of Iowa, College of Dentistry and a Master of Science in orthodontics. He is certified by the American Board of Orthodontics (ABO), is a Diplomate of the American Board of Orthodontics and a member of the College of Diplomates of the American Board of Orthodontics. He is also a member of the American Association of Orthodontists, Rocky Mountain Society of Orthodontists, Colorado Orthodontic Association, The Edward H. Angle Society of Orthodontists—Southwest Component, American Dental Association, Colorado Dental Association, and Weld County Dental Association.

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