The dimensional stability of impression materials and its effect on in vitro tooth wear studies

Abstract

Objectives To assess the dimensional stability of 8 impression materials over 12 weeks relevant to in vitro tribology studies. Methods Ten impressions from eight impression materials were taken of a metal block (ADA block) conforming to the American Dental Association specification for impression materials and of another metal block (custom block) which allowed measurements over a larger surface area. The impressions and blocks were scanned on a non-contacting laser profilometer (Taicaan ® – Southampton, UK) and using surface metrology software Boddies ® (Taicaan ® – Southampton, UK) measurements were made at 24 h, 2, 4, 8 and 12 weeks. The impression materials tested were [1] Aquasil ®, [2] Aquasil ® DECA, [3] Affinis ®, [4] Express ®, [5] Extrude ®, [6] Impregum ®, [7] President ® and [8] Take 1 ®. Results Seven addition silicones and one polyether [6] were tested. [2] and [6] were monophasic, the rest were putty-wash. The results from impressions of the ADA block showed that all materials contracted compared to measurements obtained directly from the block [1] expanded over time (+31.5 μm) ( p < 0.05). The results from the custom block showed that all materials contracted compared to direct measurements of the block. [4] and [7] expanded over time (+62 μm and +63.8 μm respectively). [8] contracted over time (−54.7 μm) ( p < 0.05). Significance No material showed linear changes >1.5% and were stable for 12 weeks. Nevertheless, the range of changes would affect tribology studies were cut-offs lesser than the reported changes are selected. All impressions should be processed after similar time delays to reduce the errors introduced by dimensional changes.