Influence of prolonged setting time on permanent deformation of elastomeric impression materials.
BACKGROUND
Upon removal, tear forces occur in various areas of an impression. As a result, thin sulcus details may be permanently deformed, affecting the impression's accuracy.


OBJECTIVE
The purpose of this study was to investigate the effect of the chemistry and prolonged setting time on the permanent deformation of light-body impression materials after stretching.


METHODS
A dumbbell-shaped mold (2 mm x 4 mm x 75 mm) was used to prepare specimens (n=20) of 6 different impression materials (Affinis Light Body, Aquasil Ultra XLV, Express 2 Light Body Flow Quick, Flexitime Correct Flow, P2 Polyether Light, and Impregum Garant L DuoSoft). After water storage (35 degrees C), either for the manufacturer's suggested setting time or for 5 minutes, specimens were stretched by 80% using a universal testing machine at a crosshead speed of 200 mm/min. The permanent deformation (Deltal (%)) was determined after 2 hours of storage in ambient conditions. A 2-way ANOVA followed by a Games-Howell test was used to analyze the influence of material and storage time (alpha=.05).


RESULTS
Polyether materials showed a significantly higher permanent deformation (Deltal>4% to 5%) than vinyl polysiloxane materials (P<.05). Extending the manufacturer's suggested setting time resulted in clinically relevant improvements in elastic recovery for products with a polyether backbone only.


CONCLUSIONS
Increasing the setting time might be necessary for impression materials with a polyether backbone to improve elastic recovery.
Balkenhol
Markus
M
Department of Prosthodontics, Justus Liebig University, Giessen, Germany. markus.balkenhol@dentist.med.uni-giessen.de <markus.balkenhol@dentist.med.uni-giessen.de>
Haunschild
Sylvia
S
Erbe
Christina
C
Wöstmann
Bernd
B
D003760:Dental Impression Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D055119:Elastic Modulus; D004548:Elasticity; D020724:Elastomers / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D011145:Polyvinyls / Q000737:chemistry; D012117:Resins, Synthetic / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
D003760:Dental Impression Materials; D020724:Elastomers; C022821:Impregum; D011145:Polyvinyls; D012117:Resins, Synthetic; C510540:SENN polyvinylsiloxane-polyether hybrid; D012833:Siloxanes; C480691:aquasil; C034183:vinyl polysiloxane; D014867:Water