2466 Impression Accuracy when Recording Impressions of Moist Surfaces
J. MCCABE, and T. CARRICK, University of Newcastle upon Tyne, England, Uk

Objectives: To determine the ability of impression materials to record impressions of moist surfaces.

Methods: One polyether material (Impregum (I) Penta Soft, 3M ESPE) and three polyvinylsiloxane (silicone) materials: Flexitime Monophase (FM), Heraeus Kulzer; Aquasil Monophase (AqM) Ultra Fast Set, Dentsply; Affinis Monobody (AfM), Coltene Whaledent were used. Gypsum (Fujirock, GC) test blocks were produced by replicating a stainless steel block. Impressions of the moist gypsum blocks were made in one of the test materials and 3 dimensional laser profiles were recorded (five replications were made for each test material). Direct comparisons of the dimensions of individual grooves in the moist models and in the impressions were made (paired t-test).

Results: The mean depth (micometers) of the deepest groove (sd) in each case was:

material

Depth of groove on moist gypsum

Depth of groove on impression

P value t-test

Polyether, I

171.6 (3.1)

171.7 (5.4)

0.99

Silicone, FM

167.0 (8.3)

161.2 (17.6)

0.41

Silicone, AqM

175.5 (3.8)

174.1 (12.3)

0.75

Silicone, AfM

169.7 (3.1)

148.1 (10.1)

0.005

The mean depth (micrometers) of the shallowest groove (sd) in each case was:

material

Depth of groove on moist gypsum

Depth of groove on impression

P value t-test

Polyether, I

16.1 (2.1)

19.9 (3.4)

0.70

Silicone, FM

16.8 (1.7)

26.3 (13.2)

0.20

Silicone, AqM

16.3 (1.3)

32.5 (7.3)

0.03

Silicone, AfM

14.00 (2.2)

28.1 (8.3)

0.01

The results showed that the polyether was the most accurate and reliable material for recording grooves on moist surfaces.

Conclusion: The dimensions in the polyether impressions were not significantly different from those in the moist cast for both deep and shallow grooves and the reliability was confirmed by the low values of sd. For the other materials impression/model differences greater than 10 micrometers were recorded for the shallow grooves.

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