CBCT Imaging for your Practice: Is Now the Time?

By Dr. Kenneth R  Webb

As I walked the exhibit floor at the AAO Annual Session in San Diego this past April, I stopped and talked to several of the company reps displaying the latest generation of CBCT scanners. Competition is good – what struck me is how far this technology has come in such a short period of time. Effective dose, image quality, and versatility are three areas where the advances are most impressive. I have witnessed these advancements first hand in my practice where we have been using CBCT since 2012 and recently upgraded a satellite office from a 2D digital Pan / Ceph to an “Ultra Low Dose” current generation CBCT scanner. I’d like to share some of my thoughts about the 2D to 3D transition.

Effective Dose
I encourage anyone interested in CBCT technology to search for studies authored by Dr. John Ludlow and his team. Dosimetry data and image quality for many CBCT scanners (both older and current generations) have been researched in great detail. Comparative data for 2D dental radiographic imaging (both intra and extra oral) is also available. By replacing our 2D Digital Pan / Ceph with a current generation CBCT scanner we have reduced the effective dose of our diagnostic records imaging by approximately 60%. (Ludlow JB, Walker C. AJO-DO, 2013;144 (6): 802-817) This is accomplished with one, approximately 5 second, ultra-low dose CBCT scan compared to the two longer duration exposures (pan then ceph) required with 2D imaging. Certainly a win-win for our patients.

What else can we use the 3D data for? Digital models: used to assess the inter-arch and intra-arch relationship as well as aiding the determination of arch length and arch width requirements and assessing arch symmetry. Modelling labs can produce articulated 3D study models from the CBCT data (DICOM) files.

STL files of the patient’s dentition and occlusion can be uploaded into whatever software you may be using in your office for 3D model storage and viewing. Additionally, these models can be used (with appropriate software) to produce treatment simulations by “moving” individual teeth or the arches as a whole. Imagine completing your diagnostic records with Intra / Extra Oral photos and one 5-second CBCT scan!

Viewing the Diagnostic Data
The software that comes with a CBCT scanner can easily produce the customary 2D diagnostic images that we are used to evaluating (panoramic, lateral and A-P ceph). In addition – you see everything! The data can be viewed in sagittal, axial or coronal sections (slices) or as a 3D “volume rendering” which can be rotated and sliced (“clipped”) at will. So why is this additional information gained from CBCT imaging important?

You will see pathology in the 3D data that isn’t visible with standard 2D imaging. When pathology is visible in 2D, the 3D data can more accurately ascertain location, extent, and character of the area of concern. This is beneficial to our patients.

Developmental Anomalies
One of my first revelations when we began imaging in 3D was the prevalence and extent of “individual anatomic variation”. But how much is too much? We have made referrals to medical specialists for significant developmental anomalies in the cervical spine, nasal cavity and paranasal sinuses. Patients / parents are appreciative of the thoroughness of our diagnostic process that includes 3D imaging.

They get their own paragraph! Your patient smiles at you and you notice a vertical asymmetry and occlusal plane “smile” cant. Is it caused by hemimandibular hyperplasia, condylar hyperplasia, a unilateral expansive lesion in the maxilla, a growth response to unilateral progressive condylar resorption (to name a few) or a growth response to a foreign object lodged in the nasal cavity? I’ve seen them all. Similar clinical presentations – different treatment plans.

Condylar position in centric occlusion, condylar size and shape, glenoid fossa morphology, condylar osseous morphology, joint space, findings suggestive of degenerative joint disease – both active and stable. It is hard to argue that these are not important considerations in our diagnostic process.

The value of volumetric and cross-sectional analysis of the naso – pharyngeal airway and its relationship to orthodontic diagnosis and treatment planning has, and continues to be, studied in great detail. Is the growth and development of a patient who presents with narrow arches, an anterior open bite or anterior crossbite, tongue thrust and a strong mouth breathing pattern secondary to adenoid / tonsillar hyperplasia, a deviated nasal septum, environmental allergies or restrictive airway dimensions in general? Should your imaging modality include an assessment of these areas?

And there is more…
Orthognathic surgical treatment planning, TAD placement guidance, precise localization of ectopic and supernumary teeth, and assessment of treatment progress – including evaluation of root torque. All are possible or enhanced with 3D imaging. And by managing scan parameters (field of view, scan time and voxel size) at an effective dose equal to or less than 2D imaging modalities.

So, if you haven’t brought this technology into your practice – is now the time?

At the 2017 AAO Winter Conference in Ft. Lauderdale, Mr. Chris Bentson reported on a survey of recent (2016) U.S. Orthodontic Residency graduates: 88% responded that they had used CBCT imaging for diagnosis and treatment planning during their residencies including 21% that used it on all patients.

For the 2013 graduates, the responses were 76% and 9% for the same questions.

Based on these statistics, are we that far away from 3D imaging being included in the “standard of care” discussion? Embracing new technology is not easy but the value added for the practitioner and our patients is significant. The orthodontic educators who expertly taught my generation faced a similar situation during their careers with a then relatively new technology: panoramic radiographic imaging. My generation faced the challenges of transitioning from analog imaging (film) to digital.

Change is not easy. The transition from 2D to 3D imaging in your practice will require a financial and educational commitment. The whole staff will be a part of this paradigm shift. A positive – 3D imaging will be a differentiator for your practice. If you are seeking an associate, partner or complete transition, 3D imaging will make your practice more attractive to the next generation of orthodontists.

3D imaging will benefit you and your patients. Is now the time?

3D Printing and Orthodontics

By Dr. Christian Groth

As we move towards the 2015 AAO Annual Session in San Francisco many of us will be making check lists for items to investigate at the exhibition hall and lectures. Anybody who has attended recent meetings has seen that intraoral scanners are a hot topic. Every year new products are being released, or updates to current systems are offered. Intraoral scanning has opened the door for additional technologies within (and outside of) the orthodontic office. Dr. John White wrote a very informative blog post in February talking about the use of intraoral scanning for same day consultations (click here to read it). As more people are offering clear aligner therapy (including general dentists and the mail order aligner system that we all know about) it is time that we differentiate ourselves as orthodontic specialists. One way in which we can do this is to incorporate 3D printing into our daily practices.

3D printing, also known as additive manufacturing, is a process by which a physical object is created from a digital file (check out a video of 3D printed models here). There are several different types of 3D printers available that range in price from a few hundred dollars to almost one hundred thousand dollars. They all have one thing in common: they build models layer-by-layer with a build platform that moves vertically. The smaller the layer thickness the better looking the model will be. The four most popular types of printers are: Fused Deposition Modeling (FDM), Stereolithography (SLA), Digital Light Projector (DLP), and Polyjet Photopolymer (PP). Without getting too technical here is how each basically works. FDM involved heating up a thin strand of plastic resin that comes off of a spool and is deposited in layers as thin as 100 microns. SLA and DLP technologies are similar in that they utilize a vat of liquid, photosensitive resin. When the light hits the resin it is cured and platform moves to enable the next layer to be cured. The different between SLA and DLP is that SLA uses a single laser point to draw an image whereas DLP uses a projected image to cure a whole layer simultaneously, which allows the printing process to move faster (think of this as the difference between drawing a picture and stamping a picture). PP printers are probably the most popular in dentistry and use inkjet technology (yes, just like your desktop printer). Liquid resin is jetted out of nozzles in an extremely accurate fashion and cured by a UV. Layer thickness of SLA, DLP, and PP printers can be as low as 16 microns (for your reference the average piece of paper is 100 microns thick).

While the technologies differ between printers what truly sets them apart is the quality of the parts. Cheap printers are made from cheap parts that can degrade over time and result in inaccurate models. It is truly a case of you get what you pay for. So if you are in the market for a 3D printer to be used in your practice, buy the best one that you can afford.

3D printed models can be used for anything in the orthodontic office.   The most practical use is for retention and relapse treatment. A major downside to stone models is that they are often destroyed during the retainer fabrication process. 3D printed models do not get ruined and can be used as many times as necessary for retainer fabrication. Imagine being able to print a model, make a clear retainer, and mail it off to a patient who is away at college. What a service you have just provided to your patient and they never stepped foot in your office! Pairing 3D printing with one of several software programs available allows us to create sequential setups/models for minor tooth movement. By controlling the process we control the overhead and thus have the ability to pass these savings on to the patient. Another great service that we can offer our patients if they have a lapse in retainer wear.

Whatever your practice is like there is a place for 3D printed models in it. While you will pay a little bit more for the physical model, the longevity, versatility, patient excitement, and ability to virtually eliminate alginate impressions from your practice will pay off in the end!