When a tooth is broken or weak due to an extensive filling or decay, it is normally restored with a crown. That means removing the decay, existing filling and enamel from the entire circumference of the tooth, taking impressions, placing a temporary crown, and having the patient return to the office in a week or two to replace the permanent crown.

With the CEREC technique only the existing filling and damaged portion of the tooth is removed. The traditional impression is replaced with an "optical" impression, a kind of photograph using a special scanner. Special computer software designs a restoration and then transmits the design to a computer-controlled milling machine. The restoration is milled in 15 minutes from a solid block of porcelain which is the same color as the tooth. It is checked in the patient's mouth to be sure of a perfect fit, the bite is adjusted and it is bonded in place. The patient leaves the office in little more than an hour completely done.