Surprises are fun for birthday parties, gifts and even visits from loved ones. But unexpected events are never welcome in my orthodontic practice. Being aware of all the details about my patients before I decide on a treatment plan is crucial for appropriate tooth movement. Cone beam 3D imaging is a valuable tool to help me reach my goal of moving teeth in a decisive and precise manner, while reducing length, cost and risk of treatment. I need and appreciate the undistorted view of impacted supernumerary teeth, unusual anatomical variations, and tooth location in relation to roots and sinuses that a 3D scan provides.
A model solution
A beneficial aspect of my preferred cone beam system, the i-CAT, is its ability to provide me with virtual study models, or dynamic modeling, through a process called segmentation. The Anatomodel (by Anatomage Corp.) is a virtual study model that contains crowns, roots, developing teeth, impactions and alveolar bone—all created from CBCT data without taking traditional impressions. I obtained this type of model on the following patient who was referred by her dentist after his 2D panoramic X-ray revealed two impacted canines.
At our initial diagnostic session, I was presented with a 2D pan (Fig. 1). Knowing that this modality is limited in information, I planned treatment by capturing a 3D scan (Fig. 2) and sending for an Anatomodel (Fig. 3).
To my amazement, the scan showed the upper-right canine was actually positioned facial-buccally on top of the upper-right lateral incisor, and the contralateral impacted canine was positioned palatal or lingual to the maxillary left lateral incisor. This was not only a surprise but also an anomaly to me. In 16 years of practice, I had never encountered this.
Using the Anatomodel, I simulated premolar extractions as well as the intended placement of a temporary anchorage device (TAD) between the upper-right first molar and upper-right second premolar. I also performed a virtual tooth movement, indicating the need for segmented mechanics and staged vectors to avoid iatrogenic collisions of roots during forced eruption.
During the first phase of movement, the crown of the tooth had to be tipped distally away from the roots of the lateral
incisor to allow the tooth to straighten. The need for a TAD was obvious at this point.
Six months into treatment, with the help of a collimated (smaller) low-dose, 4.8-second progress scan, I was able to re-evaluate root and tooth position and see that the tooth had cleared the root of the lateral incisor, making it safe to force-erupt the tooth and change the vector of force to be straight vertical. I was pleased to see that the tooth had moved as predicted.
At that point I was able to redirect the retraction of the canine safely, avoiding iatrogenic collision and damage to adjacent teeth and structures.
An added dimension of safety
This case clearly demonstrated to me the importance of having a 3D view before starting treatment. Using only 2D imaging, I would have risked making the wrong decision regarding tooth movement on at least one side. Had I exposed the tooth and put a chain on it to bring it down against the arch wire, it would have moved slightly to the lingual and collided against the root of the lateral incisor, potentially resulting in root resorption on the lateral incisor, and potentially leading to the loss of this tooth later.
I am pleased to be able to tell my patients that I can take a low-dose i-CAT scan at a limited field of view, a full scan, or just the maxilla or mandible. With the i-CAT FLX, the QuickScan+ setting can be taken at a radiation dose lower than a panoramic X-ray.1 I can control exposure time and space, a useful feature since not all cases require the same parameters for the CBCT. In this patient’s case, having 3D scans averted a potentially serious outcome and led to more predictable, more efficient and safer treatment.
The more we see, the more we know—and the fewer mistakes we make.
Dr. Juan-Carlos Quintero received his dental degree from the University of Pittsburgh in Pennsylvania and his degree in orthodontics from the University of California at San Francisco (UCSF). During this time he also received a Master of Science degree in oral biology. Quintero has served as national president of the American Association for Dental Research-NSRG, won numerous national research competitions, and has published articles in peer-reviewed scientific journals. He lectures extensively, nationally and internationally. Quintero is immediate past-
president of the South Florida Academy of Orthodontists (SFAO). He is in private practice in South Miami, Florida.