The Laboratory Perspective

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.

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.