Powdering : basics
Powdering is one of the most important parts of CEREC technique. By using the redesigned Powder Meister®, reading the simple directions and understanding a few simple concepts, powdering can be easy, quick and predictable.
Basic principles of effective powdering
To understand why powdering is necessary, let's look at two simple illustrations:
The surface of the tooth must be covered with a non-reflective coating to make it easier for the infrared camera to see detail. Without the non-reflective coating the effect on the camera is similar to our looking into a very bright light. Because of the high translucency of enamel and variations in the translucency of dentin within the tooth, the infrared beam would be projected back to the camera from totally different depths within the tooth without an opaque reflective surface.
An opaque, reflective surface, as the illustration on the right shows, provides a definitive point from which the infrared beams can bounce back. The quality of this reflective and opaque powder coating affects the quality of the virtual model as the photos below show.
How much powder is necessary?
Notice the smooth, even coating on the lower optical image compared to the upper optical image and how the virtual models are affected by this difference. As you might expect, the quality of the virtual model will effect both the ease and speed of the design process as well as the accuracy of the proposed restoration.
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The importance of imaging liquid
Be sure to use imaging liquid on the teeth to be powdered. Apply this imaging liquid to the area to be powdered and dry thoroughly with air. This liquid is very helpful in causing powder to stick to the tooth.
If the imaging liquid is not completely dried, dark blotches will appear on the powdered teeth
or as dark spots on the optical image.
topAn alternative to using Vita imaging liquid is to use flat (with the carbonation gone) root beer. The dentinal bonding expert, Dr. John Kanca was kind enough to test root beer (non-diet) to make sure that it had no ill effects on bond strength. In fact Dr. Kanca was astounded to find that root beer actually increased bond strengths.
Note: Dr. Kanca has also found that Simplicity® dentinal bonding material can be placed on the tooth preparation before powdering. He noted no reduction in bond strength if the powder was cleaned off with alcohol.
Filtering the powder?
This is a magnified view of the lumps that are commonly found in CEREC imaging powder. It is helpful to filter the imaging powder with other powdering devices that are available on the market; however it is unnecessary with the redesigned Powder Meister®. The Powder Meister® nozzle is designed to remove virtually all of the lumps commonly associated with CEREC imaging powder.
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Microwaving the powder?
Due to the built-in air-line filter, it is completely unnecessary to microwave the imaging powder to remove any moisture contamination from the air-line. It is, however, very important to change, on a weekly basis, the cotton roll in the air-line filter.