July 2016
Volume 12, Issue 7

CAD/CAM Technology

Gisele F. Neiva, DDS, MS, MS

Digital technologies have become part of our daily lives. From enhancing communications to expediting workflows, many things are faster and better when done digitally. This is particularly true when applied to the dental profession.

Digital dentistry has gained undeniable momentum in the last decade. There are several ways that a general practitioner can take part in this digital evolution—from managing schedules and inventory to digital record keeping and actual patient treatment, often eliminating the need for a physical model.

Digitizing Impressions

Traditionally, the geometry of extracoronal preparations is recorded by means of a conventional PVS impression. Most clinicians may not be aware that numerous dental laboratories have been using bench top scanners for several years to digitize PVS impressions. This illustrates the first step in a digital process, which is to acquire the digital information. Restorations are then fabricated using a CAD/CAM system.

Alternatively, clinicians may choose to use intraoral scanners to generate a digital file of the dentition, eliminating the need for PVS impressions, as well as any possibilities for distortions. There are several intraoral scanners for dental applications, such as the True Definition scanner (3M, www.3m.com), TRIOS® (3shape, www.3shape.com), CS 3500 (Carestream Dental, www.carestreamdental.com), and iTero (Align Technologies, www.aligntech.com). These scanners electronically transmit the digital file to a commercial laboratory. The laboratory fabricates the restoration using CAD/CAM and may also send the data to a model fabricating facility where a digital stereolithography (SLA) model can be printed. Printed models come articulated from the processing center and are used exclusively for restoration fitting by the technician before sending the completed case back to the doctor for delivery.

Chairside CAD/CAM

Chairside CAD/CAM systems allow the doctors to have the ultimate level of control of the entire restoration fabrication process. Chairside systems like the CEREC AC Omnicam (Dentsply Sirona, www.sirona.com) and E4D (E4D Technologies, https://e4d.com) allow doctors to complete all three steps of digitally fabricated restorations in one appointment. This results in significant improvement in efficiency and opens an opportunity for doctor-assistant dental teams to work in collaboration. After the doctor anesthetizes the patient, the assistant can take the initial scans of the opposing arch as well as the digital bite registration. Once the preparation is completed and soft tissue is retracted, either the assistant or the doctor can obtain an image of the preparation, design the restoration, and send the file electronically to a chairside milling machine for subtractive CAM milling production. Next, the restoration is trial fitted and must undergo final polishing, which is easily achieved by using a series of diamond impregnated tips and wheels compatible with the material being used.

The chairside CAD/CAM workflow can also be applied to restore teeth in the esthetic zone. After the restoration is milled and fitted, it may alternatively be customized by in-office staining and glazing. Even though this requires a programmable porcelain oven, such as the Programat CS2 (Ivoclar Vivadent, www.ivoclarvivadent.com), the staining process is pretty straightforward and can be easily handled by an assistant. Firing times vary by the material selected but the average is 10 to 25 minutes. Most patients appreciate having a break during the treatment, as the vast majority prefers to have the entire process completed in a single visit.

There are several advantages for choosing CAD/CAM, including patient convenience and no need for temporization. The importance of no temporization reflects positively in patient compliance, as issues with faulty interim restorations tend to significantly distress patients. Also, adhesively bonding a final restoration on the same day of the preparation significantly reduces chances for postoperative sensitivity, as preparations are permanently sealed rather than being susceptible to microleakage in the temporary cement.

The process of fully incorporating digital dentistry for the fabrication of chairside inlays, onlays, veneers, and/or crowns may seem overwhelming at first, especially for new users. However, both CEREC AC and E4D can alternatively be used simply as intraoral scanners. Doctors can choose the cases they want to tackle and electronically send more complex cases to be fabricated in the dental laboratory. As users become more experienced, they may want to experiment with more complex cases. The CEREC AC system has capabilities that extend beyond single-unit restorations, including implant abutments and abutment crowns, 3-unit fixed partial dentures, orthodontic aligners, bite splints, sleep appliances, and recently introduced one-appointment zirconia crowns.

Digital dentistry and CAD/CAM technology are gradually being incorporated in the workflow of the general practitioner. Dental research in the field is expanding in parallel with these advances.

About the Author

Gisele F. Neiva, DDS, MS, MS
Clinical Associate Professor
Director of the Graduate Restorative Dentistry Program
Cariology, Restorative Sciences, and Endodontics
University of Michigan School of Dentistry
Ann Arbor, Michigan

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