Volatilization of components from and water absorption of polyether impressions.
OBJECTIVE
To evaluate the accuracy of stone dies produced from impressions with polyether impression materials and a vinyl polysiloxane reference material after prolonged storage at 0, 50, or 100% relative humidity.


METHODS
Impressions were taken with light and heavy-bodied types of the polyethers P2 (P2L/H; Heraeus Kulzer) and Impregum (IML/H; 3M ESPE) and vinyl polysiloxane Flexitime (FLL/H; Heraeus Kulzer) from a truncated steel master cone in cylindrical trays giving 4 mm layer thickness at the prominence line. Impressions were taken at 23 degrees C, and stone dies were poured after 1, 2, 3, 4, or 5 days storage at 23 degrees C and 0, 50, or 100% RH. Accuracy was determined as discrepancy between a steel ring with accurate fit on the master cone and the stone die and expressed as base diameter deviation Deltad (microm). One-way ANOVA and Duncan's post-hoc test were used for statistical data analysis (p<0.05).


RESULTS
P2L/H showed significant Deltad increase (30-240 microm) depending on storage time and humidity (p<0.05). Dies from IML/H at 0% RH were 90 through 180 microm enlarged, at 50% RH the maximum diameter increase was 60 microm, and at storage in 100% RH all dies were 25-120 microm smaller (p<0.05). Dies from FLL/H showed maximum Deltad deviations (55 to -10 microm).


CONCLUSIONS
P2 impressions release volatile substances during storage and should preferably be poured within less than 24 h. Impregum absorbs water and should be stored at <50% humidity. The accuracy of Flexitime is scarcely affected by storage time or by ambient humidity.
Kanehira
M
M
Graduate School of Dentistry, Tohoku University, Sendai, Japan.
Finger
W J
WJ
Endo
T
T
D000042:Absorption; D003760:Dental Impression Materials / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry*; D008422:Materials Testing; D011145:Polyvinyls / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry*; D012833:Siloxanes / Q000737:chemistry*; D013997:Time Factors; D014835:Volatilization; D014867:Water
D003760:Dental Impression Materials; D004987:Ethers; C022821:Impregum; D011145:Polyvinyls; D012117:Resins, Synthetic; D012833:Siloxanes; C058420:polyether 82; C034183:vinyl polysiloxane; D014867:Water