The Laboratory Perspective
Inside Dentistry (ID): As a laboratory technician, do you prefer that your restorations be bonded?
Peter Pizzi, MDT, CDT (PP): Adhesive dentistry is 100% our future. Twenty years from now, there will not even be a conversation about cementing restorations. Everything will be bonded—to both enamel and dentin. That is where we are going, especially as materials continue to evolve. The aspect of bonding that is most critical for the laboratory is the strength factor. I believe that we talk too much about how hard our materials are and not enough about the strength of bonding to natural tooth structure. Consider implant-supported restorations. When we extract a tooth that lives in the periodontal ligament and has movement, proprioceptive response, and everything that nature gives it, and we put a fixed implant post into the bone, we have lost the periodontal ligament, the proprioceptive response, and the touch and feel of how the restoration interacts. The adhesive process maintains all of those important clinical aspects. Moreover, it keeps the flexural rate of the tooth. If I am just removing the enamel and bonding a veneer to a tooth, the tooth still has a flexural rate and proprioception. Really, the advantage of bonding is that it gives us the ability to improve on nature rather than take away from it and cement something over what is left. The more minimally invasive that we can be, the better dentistry gets and the better our outcomes become.
ID: Why is the laboratory's involvement important if a restoration is to be bonded?
PP: Material selection is the key component. As a laboratory technician who is a partner to both the clinician and the patient, I want to make sure that we are always choosing the right material for the right environment. Across the board, the best option that we have is bonding because that is how we can achieve the greatest adhesion to the tooth. Nanohybrid ceramics, lithium disilicates, polyether ether ketone (PEEK) materials, and even some pure feldspathic porcelains bond extremely well to natural tooth structure. Laboratories can share their knowledge regarding when to choose each material, but their clinical partners need to communicate effectively in order to capitalize on that knowledge. On a cast, laboratory technicians cannot see enamel and dentin; they just see a stone replica of what the tooth looks like. The laboratory technician's understanding of whether a restoration will be bonded to enamel, dentin, or both is important, and his or her understanding of the space being filled in the bonding process-or even in the cementation process—is really critical to the success of a case.
ID: How important is deciding on a bonding or cementation protocol at the outset and communicating the choice clearly?
PP: Fortunately, I am very involved in choosing proper materials for each case with my clinical partners. However, in some situations, there are certainly many clinicians who do not even know, themselves, whether a restoration will be cemented or bonded when they submit a case to the laboratory. I would argue that this communication gap is an opportunity to strengthen our collaboration because the clinician and technician can discuss the direction that would be best for the case together. Laboratory technicians can provide input on materials and other aspects from their side, and clinicians can offer their own perspectives regarding their preferred techniques and their patients' preferences. For example, a clinician's philosophy regarding bonding to dentin should be made clear to the laboratory because, regardless of anyone else's opinion on that controversial topic, how the dentistry will be performed is up to each individual clinician.
ID: Is it better for restorations to be etched in the laboratory or chairside?
PP: It depends on what the clinician prefers; either option works. Traditionally, laboratories have usually etched restorations made from feldspathic ceramic or lithium disilicate. During the try-in process, however, when the clinician uses either a try-in paste or other medium to try in the restoration, that medium can contaminate or disparage the etch by filling it in. To avoid having this affect the bonding of the restoration, the clinician needs to clean the restoration after the try-in, via either ultrasonic instrumentation or microabrasion, and then re-etch it for a brief amount of time (typically 5 to 15 seconds). This is being done very effectively most of the time. I would estimate that 90% of the bond failures that we see occur from the tooth side of the interface, not the restoration. We can tell because the adhesive remains on the restoration. More recently, some of my clinicians have asked us to not etch at all in the laboratory. They want us to send the restoration directly to them so that they can try it in and then do the final etch afterward. There is nothing wrong with that process as long as the clinician follows the proper protocols.
About the Expert
Peter Pizzi, MDT, CDT, is the owner of Pizzi Dental Studio in Staten Island, New York. He is also the editor-in-chief of Inside Dental Technology and an adjunct instructor at the New York University College of Dentistry.
