Indirect Restoration With Modern Materials and Digital Protocols

Q&A with Sameer Puri, DDS

Inside Dentistry interviews Sameer Puri, DDS, director of CAD/CAM at Spear Education and the vice president of CEREC Doctors

Inside Dentistry (ID): What are the cementation challenges when using modern materials?

Sameer Puri, DDS (SP): Everybody is looking to do bonding today. Back in the day, we had zinc phosphate and cements that were a little bit easier to handle and less moisture sensitive. Now, with the new materials that we have, clinicians are getting more into bonding, and bonding is challenging. You need better isolation, better control of your environment, and less moisture. The biggest problem is that clinicians are using isolation techniques that are more appropriate for a non-resin-based cement when they are bonding, and they're not getting a successful end result.

ID: On the flip side, what are the challenges associated with removing modern materials from teeth?

SP: Although the bonding process is more challenging, we get very high bond strengths when the technique is performed properly. Trying to remove a restoration that's properly bonded can, at times, become an exercise in futility. In addition, the more modern materials have higher strength, so you get a higher strength bonded restoration. For example, zirconia is much stronger than anything else that we have, and cutting through zirconia is extremely difficult. We might run into problems when more clinicians can predictably and accurately bond zirconia, which will lead to stronger bonds to a material that is virtually impossible to cut through. We're not quite there yet because most clinicians, when they use zirconia, use a traditional cementation technique. There are some cases showing success with bonding zirconia, but removing a bonded zirconia restoration is extremely difficult.

ID: Do you think hybrid ceramics are as high strength and durable as they're touted to be, or are we sacrificing longevity for esthetics?

SP: I think the term "hybrid ceramic" is a misnomer. I tend to classify these more as reinforced composites, but many people disagree with me on that. I do use them where appropriate though. Most of them are reinforced with zirconia for inlays and onlays where there is a large amount of tooth structure remaining. If I'm replacing a significant amount of tooth structure, I tendto use a lithium disilicate, zirconia, or glass ceramic restoration.

ID: Why has the adoption of digital dentistry been so slow, and do you see this trend changing in the near future?

SP: That's a fantastic question because I've been preaching the benefits of digital dentistry for 15 years now. Having been a CEREC user since late 2003, I understand the benefits of it. I wish I had a succinct answer to that question, but I don't. I understand that in the past, the technology was a little bit more challenging to use and that the materials available were limited. However, today we have digital scanners that are accurate and easy to use, and we have no shortage of materials that we can mill chairside. In today's world, clinicians have the ability to scan instead of taking an impression as well as virtually mill and fabricate any material chairside. The advancements that have been made in the technology have changed the marketplace, and I hope people realize that it's not such a big deal to make the switch to digital dentistry.

ID: Are there benefits to scanning rather than taking conventional impressions when you're working with a laboratory on more complex cases?

SP: Absolutely. I have never met a patient who preferred a conventional impression to a digital impression. Nobody wants to be sitting in the chair for any period of time with goop in their mouth, to use a colloquial term. I can scan an upper arch in 30 seconds, so I have trouble finding a reason to use traditional impression material. It's a shame, but I think it is the cost and learning curve that keep clinicians from jumping in.

ID: Do you see the trend picking up as the costs come down and as it becomes more obvious that the technology is great?

SP: Sure. However, I'm not convinced that the trend is related to cost because many of the systems have increased in price with the addition of new features, and the number of people who are buying systems now versus previously hasn't changed much. I think that many dentists tend to be set in their ways. What they're doing works for them, and it is familiar, so they have a hard time changing. Eventually, even if it takes a while, they're going to have to change because that is where the industry is headed.

ID: What impact do you foresee 3D printing having on chairside milling?

SP: The ability to 3D print quickly and accurately is going to be a massive revolution for dentistry. Of course, digital processes are always a benefit because they are more accurate and easier than conventional ones, but eliminating the laboratory will be a huge change. If I need a model, then all I have to do is hit print instead of sitting there and pouring up the stone, and you avoid the possibility of the impression material getting damaged when removing the model. In the future, we won't just be printing models, we'll be printing appliances, restorations, and all sorts of things. I'm optimistic that people will view the technology differently than they did in the past, but I remain baffled that there hasn't been quadruple the number of clinicians adopting the technology.

ID: You mentioned 3D printing restorations. What specific advantages does 3D printing offer over milling?

SP: With milling, you're limited by the bur size. For example, if I wanted to create very detailed anatomy, I'd have to use a smaller bur for that part of the process, which means that it's going to take longer. That bur might need to be replaced, and there are certainly, for lack of a better word, vibrations in the bur that can lead to inaccuracy in milling. We can minimize or even eliminate that with 3D printing because we can print with finer detail. I believe that we're still a long way away from printing permanent restorations, but I think we've taken the first step in printing provisional restorations, long-term provisional restorations, and mock-ups.

ID: On the subject of veneers: prep or no prep?

SP: It depends on the case. I want to remove as little tooth structure as possible but as much as is necessary.

ID: So, no prep is possible?

SP: Of course. I can't do no prep on every case, and I don't have to reduce on every case. But, it's not an "either or" thing. We just need to be as conservative as possible while giving ceramics the proper room for contours, esthetics, strength, and function.

ID: What are you particularly excited to see as the dental industry evolves?

SP: I've been teaching CAD/CAM dentistry for about 15 years now, and I'm very excited when I see new systems come out. I'm also thrilled when clinicians come to a workshop, and then I see them months or years later, and they tell me that the technology has changed their lives or outlook on dentistry because they're having fun and producing more accurate restorations. As a long-term advocate for the technology, interactions like that make me feel really good about the direction in which it is heading.