CEREC

CEREC is a dental restoration product that allows a dental practitioner to produce an indirect ceramic dental restoration using a variety of computer assisted technologies, including 3D photography and CAD/CAM. With CEREC, teeth can be restored in a single sitting with the patient, rather than the multiple sittings required with earlier techniques. Additionally, with the latest software and hardware updates, crowns, veneers, onlays and inlays can be prepared, using different types of ceramic material.

Technology

The cavity preparation is first photographed and stored as a three dimensional digital model and proprietary software is then used to approximate the restoration shape using biogeneric comparisons to surrounding teeth. The practitioner then refines that model using 3D CAD software. When the model is complete a milling machine carves the actual restoration out of a ceramic block using diamond head cutters under computer control. When complete, the restoration is bonded to the tooth using a resin.CEREC is an acronym for Chairside Economical Restoration of Esthetic Ceramics.

History

The system is manufactured by the Sirona dental technology company.

1980 Development of the CEREC method at the University of Zurich W. Mörmann, M. Brandestini).
1985 Treatment of the first patient with CEREC (University of Zurich, material: VITABLOCS Mark I).
1986 Siemens acquires the license to market and further develop the CEREC equipment.
1987 CEREC 1 is introduced (chief indication: single and dual-surface inlays; material: VITABLOCS Mark II).
1990 International CEREC Symposium at the University of Zurich.
1991 Hydraulic machining drive replaced by an electronically controlled motor.
1994 CEREC 2 is introduced (range of indications: inlays, onlays, veneers).
1996 CAD/CAM Symposium to mark a decade of CEREC (University of Zurich).
1997 Sirona was formed as the result of the sale of the Dental Division of Siemens AG.
1997 CROWN 1.0 program for producing full-ceramic posterior crowns.
1998 Second material manufacturer partnership is formed (lvoclar, ProCAD).
1998 CROWN 1.11 program for producing posterior and anterior restorations.
2000 CEREC 3 is introduced (compact Windows-based CAD/CAM system).
2000 Third material manufacturer partnership is formed (3M Paradigm MZ100).
2002 More than 2,500 CEREC users in the United States and over 5,000,000 CEREC restorations placed worldwide.
2003 3D software version is released, allowing users to see 3D views of teeth and models.
2006 CEREC Celebrates 20 Years.
2006 Sirona releases BIOGENERIC version of software. This software allows for the machine to accurately reconstruct the missing tooth shape and surface.
2007 More than 23,000 CEREC users world wide.
2008 Sirona release the MCXL milling unit, this milling unit can produce a crown in 4 mins.

Technique

The treating dentist prepares the tooth being restored either as a crown, inlay, onlay or veneer. The tooth is then coated with a white powder, imaged by a 3D imaging camera and uploaded to the CEREC computer. Using the proprietary CEREC software in various modes, a restoration can be designed to restore the tooth to its appropriate form and function. This data on this restoration is stored in a file and is sent via wireless serial transmission or direct wiring to a milling machine. The restoration can then be milled out of a solid ceramic or composite block. Milling time varies from as little as four minutes to as long as twenty depending on the complexity of the restoration and the age of the milling unit.

Design Methods

The design software for the CEREC system has undergone significant changes in the years since the technique was first introduced by Professor Mormann. Currently, a dentist can choose from four major design approaches.

Database:

This design mode uses a library of tooth shapes that is stored on the computer to suggest the shape of the proposed restoration. Most commonly a recording of the bite registration (the imprint of the opposing or antagonist tooth in a wax like or rubbery material) is also added to the data the software can use when deciding the proposal. This data together with a 3D optical imression of the prepared tooth establishes the approximate zone with which the new restoration can exist. The proposed restoration can then be morphed to fit into this zone in an anatomically and functionally correct position. The dentist can then make correction to this proposal as he sees fit and then send it to the milling unit for completion.

Materials

The ceramic material has some properties that make it very suitable for use in dental restorations. It expands and contracts in response to temperature changes at a rate approximately half-way between those of enamel and dentin. It also wears away at approximately the same rate as enamel. There is also a composite material available which has some advantages in restoring smaller inlay type restorations.

Advantages / Disadvantages

Avantages

1. The preparation of the tooth structure to receive the restoration is less invasive than the preparation needed for a conventional full coverage crown. Keeping more natural tooth helps the repair last longer.
2. Time saving. You usually only have to go one time, as opposed to two trips for a traditional crown. This also reduces the number of local anesthetic injections (shots) needed.

Disadvantages

1. The need to powder the teeth prior to taking the optical impression. It is somewhat time consuming and technique-sensitive as it requires an even application of the powder on the entire tooth surface to be scanned, but the powder washes off.
2. Although a bite record is taken of the opposing tooth, contacts from the opposing teeth may have to be adjusted for. CEREC restorations have to be adjusted in the mouth and therefore, occasionally can look "flat" or over-adjusted.
3. All-ceramic restorations cannot be used in every patients or on all teeth.
4. Expensive. Although less time consuming, the cost of a CEREC setup is very high and there would be an impetus on the dentist to retrieve this cost. Extra training and substantial experience is necessary to become proficient at this technique.

External links

* [http://www.sirona.com/ Sirona company on the WWW]
* [http://www.cereconline.com/ CEREC pages of the manufacturer]
* [http://www.cerec.net/ The largest CEREC community on the WWW]