Dental Advisor: CAD/CAM Dentistry - 2008

In order to succeed and thrive in the newly digitized world of dentistry, dentists will have to embrace this new technology. The possibilities are endless within the digitized world. Intraoral scans can transfer a digital impression from the operatory to the dental laboratory in seconds. Communication among all can be nearly instantaneous. Of course, there are challenges in adopting a new technology: new equipment to use, new procedures to follow, and new skills to learn. This technology is continually evolving and will be reported on in future issues.

This issue of THE DENTAL ADVISOR (November 2008, Vol. 25:9) introduces CAD/CAM dentistry, from basics to the complex, featuring relevant and timely information on chairside intraoral scanners, chairside CAD/CAM, digital workflow, outsourcing, tooth preparation guidelines, and more.

CAD/CAM is an acronym for computer-aided design/computer-aided manufacturing. The CAD portion of the process involves the use of a scanner to create a digital model of the preparation, and sometimes the adjacent and opposing dentition. Once the model has been generated on a computer workstation, the restoration can be designed by the doctor or a lab technician.

The CAM portion of the process involves the use of a mill or special printer to fabricate what was designed during the CAD process. This could be a coping, the final restoration or a working physical model.

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In-office CAD/CAM systems allow the dentist to take a digital impression and design the restoration, all in the doctor's office. Once the restoration has been milled, it is often polished or glazed before placement. Another approach is to send the scan or digital impression to the laboratory. A laboratory technician designs the restoration on the computer and communicates that to the milling machine. The milling machine can be in the lab or outsourced to a milling center. Once the milling machine has completed the restoration, it may require layering porcelain and staining and glazing.

Laboratory CAD/CAM systems can be standalone systems that allow dental laboratories to scan, design, and mill restorations; alternatively, restorations can be outsourced to a milling center where a coping is made. Laboratory CAD/CAM systems may also accept intraoral scans from dental practices and fabricate the final restoration.

An intraoral or chairside scanner captures digital images of the mouth to build a virtual 3D model of the preparation and adjacent teeth on the computer. These scanners use digital images to help design the restoration. Some scanners require the use of powder or scannable bite registration material.

Benefits

• Accuracy (no shrinkage or distortion)
• Ability to scrutinize preparation immediately
• Ability to modify preparation immediately
• Instant laboratory input (if applicable)
• Positive patient response

• Cost
• Learning curve
• Continually changing technology
• Size of intraoral scanner
• Lab participation
• Additional materials for scanning

Due to the capturing process, some scanners require the use of a contrast medium or scannable bite registration material. These materials treat the surface being scanned, preventing reflective voids and providing optimal anatomy and margin detail.

• Scannable Bite Registration Materials
  StoneBite Scan (EXACTA Dental)
  Virtual CADbite Registration (Ivoclar Vivadent)
  Futar Scan (Kettenbach GmbH & Co)
  Occlufast CAD Scan Bite (Zhermack, Inc.)

• Contrast Powder – Note: Not all intraoral scanners require the use of contrast powder.
  EXACTA Blue Spray (EXACTA Dental)
  CEREC Powder (Vident)
  Scan Spray (Vident)
  IPS Contrast Spray (Ivoclar Vivadent)

• Contrast Powder Delivery Systems
  Powder-Pro (Advanced Dental Instruments, LLC)
  PowderPerfekt (Ourglass, Inc.)
  Powder Meister (Powder Meister, Inc.)

In-office Complete CAD/CAM Systems - Chairside Intraoral Scan and Mill

These systems allow the dentist in one patient visit to:

• Do an intraoral scan.
• Design the restoration.
• Mill the restoration.
• Stain and glaze the restoration.
• Seat the restoration.

CEREC (Sirona)
E4D Dentist (D4D Technologies)

In-office Intraoral Scanners - Chairside Intraoral Scan and Outsource Milling

These systems allow the dentist to:

• Do an intraoral scan.
• View an interactive digital model.
• Design the restoration, in some cases.

Final steps to complete restoration:

• Virtual model trimming done by design center, lab, or SLA (stereolithography apparatus) facility.
• Stereolithographic model and dies are created by SLA facility.
• If zirconia restoration, coping can be made by milling center.
• If PFM restoration, wax coping can be made by milling center or SLA facility.
• Model and/or coping sent to laboratory to finalize restoration.

Lava Chairside Oral Scanner C.O.S. (3M ESPE)
iTero (Cadent)

Laboratory CAD/CAM Systems

Laboratory CAD and Laboratory CAD/CAM systems:

• Use traditional impression techniques, have the model scanned, and make the restoration using CAD/CAM technology.
• Use any intraoral scanner and send the file to a participating lab or milling center for design and finishing.

Cercon (DENTSPLY Ceramco)
Everest (KaVo)
Lava Precision Solutions (3M ESPE)
Sirona InLab (Sirona)
Zeno (Wieland)

Laboratory CAD

Some laboratories have made the investment in digital scanning and design technology. However, to complete the restoration, the lab will outsource the design to another company to mill. Send the restoration back to the design CAD lab for finishing, if applicable.

Authorized Lava Milling Center (3M ESPE)
Cercon (DENTSPLY Ceramco)
GC Advanced Technologies Milling Center (GC America)
Katana (Noritake)
Procera (Nobel Biocare)
Vericore (Whip Mix)
Zeno (Wieland)

CAD/CAM workflow is a series of steps that involve the dentist, dental laboratory, and at times, milling center. The diagram below provides the options on how information is transferred to create a complete restoration (click to enlarge).

See CAD/CAM Materials table at top of article.

These are the ceramics used in dentistry for the last 30 years and their respective flexural strengths. Zirconia is the strongest of these ceramics.

How to prepare a tooth

• Reduce the tooth as uniformly as possible.
• Reduce it by 1.0 – 1.5 mm circumferentially.
• Use a chamfer diamond.
• Reduce the occlusal by 1.5 – 2.0 mm.
• Do not leave any sharp line angles.

Preparation is critical

• Uniform reduction results in optimum ceramic strength.
• Adequate reduction leads to better aesthetics.
• Sharp edges result in high stresses.
• High stresses increase the potential for fracture.
• Scanners read smooth preparations more accurately.
• Ceramic restorations require a passive fit.

Tooth Preparation Illustration (Click on the image for a larger view.)

CAD/CAM dentistry is changing on a daily basis. Every part of the dental profession can get involved in some way. The future is promising in terms of the technological advances that CAD/CAM is providing to the dental industry. Future issues will focus on the integration of 3D imaging, laboratory involvement, the evolution of new materials and equipment, and exciting restorative options.

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