Digital dentistry from a prosthodontist's viewpoint

At the ADX14 Sydney dental exhibition, March 21-23, at the Sydney Exhibition Centre @ Glebe Island, specialist prosthodontist Tom Giblin will present a talk on Digital dentistry from a prosthodontist's viewpoint. Here's a preview of what to expect…

When we started setting up our new Prosthodontic practice nearly 18 months ago, we had to make some big decisions about the direction in which we were heading. As a new practice with our own in-house lab, we set up for "digital dentistry" from the outset, but in doing so we have discovered that changing from the "casting age" to the "digital age" is very straight forward and greatly improves efficiency.

Over the last 5 years, there has been a quiet revolution in dentistry, as we have seen a maturation of CAD/CAM technologies to the point where they are as accurate, more cost-effective and less labour intensive than traditional techniques. Combining this with new restorative materials such as e.max and the "maturing" of other materials such as zirconia and CoCr, we are now facing the prospect of needing to review what may be considered the "gold standard".

What we have discovered with newer materials such as e.max and zirconia is that their greatly increased strength makes them much harder to adjust, polish and, if there is a failure, to cut off. This means that increased accuracy and care is needed throughout the diagnosis, impression taking and fabrication process to eliminate the need for adjustment in the mouth. By ensuring quality throughout the process, consistent results can be achieved.

Digital diagnosis

As well as both 3D and 2D digital radiography that has been covered extensively in this magazine, we also employ T-Scan digital occlusal analysis in our practice. T-Scan allows us to assess a patient's occlusion and not just where the contact points are, rather it assesses the force at each contact point and also the timing of how the teeth come together and disclude. It provides a slow motion video replay of how the teeth come together and allows us to see and address any destructive interferences before we begin the reconstructive phase of treatment.

It also provides an objective pre-treatment record. The T-Scan is also invaluable in fine-tuning occlusion after the restorations are placed, especially in implant cases where the patient has greatly reduced proprioception and increased biting force, which can be a recipe for failure.

Digital impressions

After multiple trials and initial buyer resistance of something so different to trusted traditional impressions, we have added an iTero intraoral scanner to our practice. For a while we still took traditional impressions as well as the scans as backup and for verification, but we experience has shown us this is not necessary. As with anything, at first there is a learning curve, but eliminating the need for PVS impressions, opposing impression and bite registrations, the time taken is about the same as traditional impressions, and the patients seem to find it more pleasant. We have used iTero for everything from inlays to full arch implant bars and have found the accuracy to be as good, if not better than traditional impressions.

CAD/CAM, centralised milling

The main tool we have with digitizing our practice is the 3Shape benchtop scanner, which allows us to both scan our traditional casts into the computer, or import iTero scans for designing of the restorations. This system was chosen as it is the most versatile. It can be used to design inlays, onlays, crowns, bridges, implant abutments and bars, as well as CoCr partial denture frameworks.

A new addition to this system is a split cast mounting system for Denar articulators, which allows us to take a facebow record and then transfer that into 3Shape, where we can mount the case on a virtual Denar articulator. This then allows us to rapidly do virtual wax-ups. This can then be model-printed and tried-in to the patient's mouth as a mock-up before proceeding.

We decided against an in-house milling solution as these units cannot compete with the accuracy of the large units used by our milling partner (Core3d), whose DMG mill has been verified to around 5 micron accuracy. Core3d has 9 different mills and an EOS M270 CoCr laser 3D metal printer, allowing us to manufacture via multiple different technologies. The central milling model therefore is more cost effective, provides redundancy and eliminates the headaches created by owning and running the machines in-house. We are increasingly finding the margins from our CAD/CAM crowns are more accurate and less technique sensitive as those from traditional stacked porcelain and even from our pressed porcelain margins.

CAD/CAM allows for the manufacture of two types of models, reductive or milled models (iTero) and additive or "printed"models. We have helped with the Beta testing of the Core3d "printed" models and found them to accurate when compared to traditional casts. We have found the iTero milled models to be the more accurate for crown and bridge and Core3d are in the final stages of testing them for direct to fixture implant cases. Once these are available, it will mean a much easier workflow for our implant cases.

In summary, we have found the transition to a digital practice and lab, despite a few "teething problems", to be fairly straightforward and very rewarding. It has definitely enhanced our productivity, decreased our costs and improved our consistency and accuracy in the lab.

Hear Dr Giblin present "Digital dentistry from a prosthodontist's viewpoint" at the ADX14 Sydney dental exhibition, March 21-23, 2014 at the Sydney Exhibition Centre @ Glebe Island at 3pm on Saturday (March 22).

Dr Giblin graduated dentistry at the University of Sydney in 2004, before completing his Prosthodontic Residency at the University of Texas at San Antonio. He is currently in private practice in Mona Vale on Sydney's Northern Beaches.