CAD/CAM Dentistry: A New Forum For Dentist

The laboratory technician’s primary role in restorative dentistry is to perfectly copy all of the functional and esthetic parameters that have been defined by the dentist into a restorative solution. It is an architect/builder relationship. Throughout the entire restorative process, from the initial consultation through treatment planning, provisionalization, and final placement, the communication routes between the dentist and the laboratory technician require a complete transfer of information pertaining to existing, desired, and realistic situations and expectations to and from the clinical environment. Functional components, occlusal parameters, phonetics, and esthetic requirements are just some of the essential types of information that are necessary for the technician to complete the fabrication of successful, functional, and esthetic restorations.

Today, as in the past, the communication tools between the dentist and the technician are photography, written documentation, and impressions of the patient’s existing dentition. The clinical prep-arations and the opposing dentition from these impressions/models are created and mounted on an articulator, which simulates the jaw movements of the mandible.

As restorative dentistry evolves into the digital world of image capture, computer design, and the creation of dental restorations through robotics, the dental laboratory must evolve as well. To fully understand this concept, a laboratory must be clearly defined. At first thought, it may seem that a laboratory is the place where a dentist sends his or her patient’s impressions to be processed into restorations, which are sent back to the dentist for adjustment and delivery (Figure 1). This definition fits well with the traditional concept of a laboratory–dentist workflow. However, the possibility to transfer computer-aided design/computer-aided manufacturing (CAD/CAM) restoration files electronically has provided the catalyst for a significant change in the dentist–laboratory relationship .

The Virtual Laboratory

Imagine that the laboratory is not a physical place, but exists only in the talents of those performing the restorative process: the dentist, auxiliaries, and technician(s). The equipment used to create the restoration may be located centrally, remotely, or both. The laboratory is essentially a workflow, which is as flexible as the abilities of the dentist, the technician, and the equipment will allow. The primary decision becomes where the hand off from one partner to another should occur. The dentist who has the ability to optically scan teeth for impression-making and who often chooses CAD/CAM restorations as the best treatment option for their patients has enhanced freedom as to where the hand off to the technician should occur. The laboratory is no longer a place, it is instead to a large degree, virtual.

In some instances, it may make sense for the dentist to work independently and finish the restoration chairside in a single visit with the obvious advantages a clinical CAD/CAM system has to offer . These cases might include less complex restorations or fewer numbers of restorations for the same patient that do not require any special characterization other than perhaps stain and glaze or polish. Other times, it may be advantageous to engage the services of a technician because he or she possesses the skill and, perhaps more importantly, the time to create restorations that either demand more complex characterization or can be more efficiently created in an indirect manner.

Computer-aided Dentistry

The first successful introduction of CAD/CAM into dentistry was the chairside CEREC® 1 system (Sirona Dental Systems, Charlotte, NC) in 1982. The fundamental principle of this concept was to electronically capture a preparation’s image and then use software to interpolate the information and create a digital model. A virtual restoration design was then suggested and, after user-defined parameters were set, the restoration design was milled from a ceramic block and seated, all in one appointment. With the introduction of the CEREC 2 and CEREC 3 systems (Sirona Dental Systems), subsequent software and hardware upgrades primarily focused on improvements in user-friendliness, accuracy, and material milling options. The current generation, CEREC 3D (Sirona Dental Systems), is still the only chairside CAD/CAM system available to dentists, although other systems are in development for future release.

The introduction of CEREC® inLab (Sirona Dental Systems) in 2004, along with its accompanying software upgrades and libraries, became one of the first computerization model to accurately present a virtual model and take into consideration the occlusal affect of the opposing (antagonistic) dentition. It essentially takes a complex occulsal scheme and its parameters, condenses the information, displays it in an intuitive format (which allows anyone with basic knowledge of dental anatomy and occlusion to make modifications to the design), and then sends it through to the automated milling unit. For dental laboratories, the introduction of the inLab system effectively automated some of the more mechanical and labor-intensive procedures (eg, waxing, investing, burnout, casting, and/or pressing) involved in the conventional fabrication of a dental restoration, allowing the laboratory technician to create functional dental restorations with a consistent, precise method .

As with any conventional laboratory-prescribed restorative process, the CAD/CAM procedure begins with the usual steps: the clinician prepares the case according to the appropriate preparation guidelines, takes impressions of the case, and sends these and other critical communication aspects to the laboratory. After the laboratory receives all of the materials from the dentist, the impression is poured, the models mounted, and the dies are trimmed. A bite registration is taken using the mounted models and will be used in a subsequent step. At this time, the procedure moves into the realm of computerized technology for scanning and fabrication .

Although this application offers many advantages to the dentist–technician team, it still requires the making of an intraoral impression using conventional techniques and sending these impressions to the laboratory for the creation of a preparation and the opposing models.