Taking precise impressions

Impression taking is the first step towards making an accurate master model of the clinical situation.

Renishaw's pioneering research into the accuracy of this process has highlighted optimum materials and techniques that result in a better fitting, longer lasting restoration.

How accurate do impressions need to be?

Literature states that the mean marginal gap should be no more than 100 µm (0.1 mm).

What is a micron?

A micron (µm) is 1/1000th of a millimeter.

The image (right) shows the size of some common structures in the body in terms of microns.

Problems with detecting marginal fit

Marginal gaps can be difficult to check using dental explorer probes. 

The image (right) shows a close-up view of a typical explorer tip, highlighting a 100 µm flat spot at the end, making probing of small marginal gaps impossible.

So, if the precision required in a finished restoration is such that unacceptable fit cannot be detected readily at the end of the process, then it is essential that accuracy is considered at each stage along the way.

Renishaw's recommended impression-taking technique

No CAD/CAM system can compensate for a bad impression.  The master model must represent the clinical situation accurately, to get a precision fitting and a long lasting restoration.

Renishaw's research into impression and model materials, and techniques has shown that the majority of the error seen in typical restorations comes from the impression stage.  Whilst the ideal marginal gap should be no more than 100 µm, a bad impression can result in errors several times this amount.

Renishaw's inciseTM clinical guidelines explain a unique two-phase impression process where the viscosities of the tray and wash materials are carefully matched.  Renishaw recommends the use of a metal perforated tray, the use of selected tray materials combined with a lower viscosity clinical wash material to capture the essential detail. 

Renishaw also recommends model materials for use by dental laboratories to make precise master models.

Recommended inciseTM materials and accessories

We recommend the following materials and accessories for use with the inciseTM process:

Material / accessory	Renishaw inciseTM recommendations
Impression trays	Perforated metal tray
Tray material	Coltene Whaledent® Affinis™ MonoBody tray material Kettenbach Monopren® transfer tray material
Wash material	Coltene Whaledent® Affinis™ Regular Body wash Kettenbach Panasil® initial contact light or extra light wash
Impression method	Simultaneous application of wash and tray material by dentist and nurse
Model stone	inciseTM model stone matched to the impression
Cement	Kururay Panavia® F Cement

Buy inciseTM-approved materials

Tested and recommended for the inciseTM process, Exact Dental Supplies provides all the products needed to take the most accurate impressions.

www.exactdentalsupplies.com