Last month, our CEREC Worldcolumn focused on tooth preparationfor CEREC restorations. The next
steps involve accurately capturing theoptical impression from which dentistscan design the final restoration.
Prior to capturing the optical impression,the teeth need to be coated with a thin,opaque layer of white titanium dioxidepowder in order to achieve uniform scatterof the light that clearly defines the surfaceanatomy. Once the tooth has beenproperly prepared, a clear liquid adhesiveis generously applied with a small brush toall surfaces of the prepared tooth and theadjacent teeth that allows maximumadhesion of the powder.
After the liquid is blown thin with air, thepowder is then applied evenly throughoutthe area with an aerosol propellant spraycan apparatus. Uneven or blotchyapplication of the powder will result in aninaccurate optical impression.
Once powdered, the area is now ready forthe optical impression with the infraredcamera. The camera features a telecentricfixed focus lens with a 10mm depth offield. The sharpness of the image dependsupon the distance between the cameraface and the preparation. With thecamera held in place over the teeth, thedentist looks at the computer monitor andfirst rotates clockwise or counterclockwisein order to align the teeth along the longaxis of the video screen. Once aligned, thedentist must then tilt the lens so that italigns parallel to the occlusal surfaces. Iftilted excessively in a mesial or distalangle, the result will be a partially out offocus image. The image is captured via afoot pedal mounted on the underside ofthe CEREC unit.
Douglas Voiers is a reconstructive and aesthetic dentist who has won tophonors in the annual Dental Economics' Practice of the Year Awards. Hemaintains a full time practice in Avon Lake, OH and is currently a clinicalinstructor for restorative dentistry at the Great LakesEducational Center in Southfield MI. Douglas recentlyearned a fellowship in the World Congress of Microdentistry.He is the Director of clinical dentistry at the Great LakesRegional Educational Center in Southfield Michigan where heteaches CEREC and advanced technology dentistry, the ICOIand the AACD. Douglas can be reached at 440-933-3270 orby email at: [email protected].
Mark Morin, DDS, FWCM, graduated from the University of Detroit in 1985 andimmediately started his new practice in Southfield, MI. He became one ofthe first dentists in North America to begin using CEREC I technology. Hecurrently places 10-15 CEREC restorations daily and continues to studyCEREC technology extensively in Germany and Switzerland with inventor, Dr.Werner Mormann. Dr. Morin maintains a 6000 sq ft office and ExperDentcenter. He is one of 10 internationally certified CEREC trainers in North
America and has had the distinction of training some ofdentistry's most well-know clinicians such as Dr. RelaChristensen and Dr. Howard Farran. Mark can be reached byemail at: [email protected] or by calling 248-828-9989.Visit his website at www.drmorin.com.
Clinical Tips Part 2: CEREC Powder & Optical Impression
The importance of quality opticalimpression technique with CAD/CAMdentistry is equal to that of traditionalcrown and bridge impression methods inachieving a well fitting final restoration.With a little practice beforehand ontypodont models, most dentists get thehang of the CEREC powder andimpression technique intraorally veryquickly. Most take no more than 60-90seconds to achieve a good result beforemoving on to the design phase. DT
Powder/OpticalImpression Guidelines:
l Generous liquid application - blow thin
l Even titanium dioxide application without clumps or thin areas
l Close proximity of camera face to tooth surface
l Rotate camera to align teeth with vertical axis of screen
l Assure camera angulation is parallel to occlusal plane
l Be able to clearly read all pertinent preparation lines on screen
What are your concerns?
If you have a CEREC question,please send it by fax to 480-598-3450 or send by email to:[email protected] [email protected]
