CEREC Technology gives you a beautiful smile

CEREC Technology gives you a beautiful smile

Esthetics and Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) Systems

In the mid-1980s, the earliest generation of computer-aided design/computer-aided manufacturing (CAD/CAM) technology was designed to fabricate immediate chairside inlay and onlay ceramic restorations. This initial technology required an excessive amount of fabrication time. The first generation of computer software and hardware that accompanied this technology offered only a limited, two-dimensional view of the scanned images because the system’s hard drive was incapable of storing the volume of data required for a three-dimensional view.

CAD/CAM technology

CAD/CAM technology has evolved to become a practical and useful resource for dental professionals to perform chairside restorations. In CAD/CAM technology, a digital impression is substituted for the traditional elastomeric impression using an intraoral digital scanner.

Alternatively a digital scan of a cast made from a traditional elastomeric impression also can be performed. An intraoral digital impression « captures » the data of the teeth and their supporting soft-tissue structures is recorded by a scanning wand using an optic laser, digital imaging, and/or video technology.

A specialized three-dimensional (3D) rendering program allows the images of the intraorally scanned impressions to be actualized in three dimensions and in real time on a computer monitor. The software allows the dental professional to mark margins, digitally design wax-up proposals of the restoration, place accurate occlusal contacts, and refine the proximal contact areas with adjacent teeth.

The clinician can preform any or all of these procedures at the chairside « design center » before sending the definitive data to the computer-controlled milling unit.

The workflow is summarized by the following steps:

  1. Tooth preparation
  2. Intraoral scan
  3. Restoration design
  4. Milling of the restoration (coloring, glaze, polish) and adhesive luting.

The CEREC 4.0

 

The Cerec system (made by Sirona Germany and distributed by Paterson Dental Co., Sr Paul, MN) was first introduced in the United States in 1996. It requires the use of a white, glare-free powder containing titanium oxide to enhance the contrast of the tooth.

A CCD sensor wand makes a 3D infrared scan of the preparation in roughly 0.1 seconds at a resolution of 25 micrometers. The digital image is displayed on the self-contained microprocessor display where the dentist designs the restoration.

The Cerec is capable of fabricating porcelain inlays, onlays, crowns, and veneers, and allows immediate, single visit esthetic restorations. Version 4 can mill a single-unit definitive or provisional restoration and a provisional three-unit fixed partial denture from an acrylic block.

The system also contains a block that functions as a wax casting (burnout block) for a cast metal crown. The system also contains a portable, air-axis micromilling machine that can be used in the dental office. The clinician can electronically send a design and the digital impression with Cerec Connect to the off-site laboratory for fabrication of casts, multiple units, fixed partial dentures, implant abutments, and zirconium or metal crowns.

Cerec can also be integrated with the Galileos System to construct surgical guides for implant placement. The Cerec’s Biogenetic software can analyze individual patient occlusion and the anatomy of adjacent teeth so that the restoration is patient-specific. Preparation evaluation software (prepCheck) is included. This is a learning tool that provides an analysis of either a computer-simulated tooth preparation or a scan of an actual tooth preparation.

CAD/CAM Restoration Materials

Advances in CAD/CAM CAM technology occurred simultaneously with innovations in esthetic restorative materials. Modern monoblock ceramic materials have been engineered to resist masticatory stress and milling induced damage.

Feldspathic ceramic materials have been mostly replaced by reinforced ceramic with silica (feldspar, Ieucite, and lithium disilicate), nonsilica (alumina and zirconia), and combination of resin-ceramic based materials, resulting in a three- to 11-fold increase in flexural strength.

Computer modelling simulation shows that a single, thick, monolithic all-ceramic crown materials performed better under stress when compared with ceramic core material with veneering porcelain. Furthermore the coefficient of thermal expansion mismatch between core and veneer materials may initiate the internal stress that causes delaminating or internal cracking of porcelain.

Advantages of CEREC crowns

  • Immediate crown fabrication: The crowns are able to be immediately fabricated eliminating traditional laboratory fabrication procedures.
  • Monolithic crown: Single layer ceramic materials exhibit better strength than dual layer core and veneer porcelain.
  • Marginal integrity: CAD/CAM milling crowns exhibit the same marginal integrity as those made with conventional laboratory-made crown restorations.

Reference:

Esthetic Dentistry: A Clinical Approach to Techniques and Materials, 3 rd edition, Kenneth W.

Aschheim

Contempory Esthetic Dentistry, George Freedman