The effect of temperature on viscosity of root canal sealers.
OBJECTIVE
To test the hypothesis that there was no significant (alpha = 0.05) change in viscosity of commercially available root canal sealers with increase in temperature using a high-performance Advanced Rheometric Expansion System (ARES) rheometer.


METHODS
Materials tested were Apexit, Tubliseal EWT, Grossman's, AH Plus and Ketac-endo. Cone-and-plate geometry was used (25-mm diameter, 0.1 radian and gap 0.051 mm). Measurements were carried out for steady-state viscosity at 25 and 37 degrees C in the shear rate range of 0.001-50 s(-1) at standardized relative humidity and within 30 min from the start of mixing. Five samples were taken for each sealer at each temperature.


RESULTS
At 25 degrees C all sealers demonstrated shear thinning. At 37 degrees C Grossman's (powder : liquid ratio 2 : 1 and 3 : 1) and Ketac-endo had a rapid rise in viscosity and early set whereas the other sealers were shear thinning. On increasing temperature from 25 degrees C to 37 degrees C, Apexit, Tubliseal and AH Plus had reduced viscosity whereas Grossman's 2 : 1, Grossman's 3 : 1 and Ketac-endo had increased viscosity, which varied with the shear rate. The change in viscosity with change in temperature was significant (P < 0.05) for all sealers except AH Plus.


CONCLUSIONS
There was a variation in the effect of increasing temperature on each sealer depending on the shear rate. With the exception of AH Plus, a significant (P < 0.05) change in viscosity was found, and the null hypothesis was rejected.
Lacey
S
S
Department of Biomaterials and Conservative Dentistry, Dental Institute, King's College London, London, UK. susanna.lacey@kcl.ac.uk
Pitt Ford
T R
TR
Yuan
X-F
XF
Sherriff
M
M
Watson
T
T
D002126:Calcium Hydroxide / Q000737:chemistry; D004853:Epoxy Resins / Q000737:chemistry; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D006813:Humidity; D008422:Materials Testing; D012212:Rheology / Q000295:instrumentation; D012387:Root Canal Filling Materials / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D014783:Viscosity; D015035:Zinc Oxide-Eugenol Cement / Q000737:chemistry
C074418:Apexit; D004853:Epoxy Resins; D005899:Glass Ionomer Cements; C074934:Ketac Endo; D012387:Root Canal Filling Materials; D015035:Zinc Oxide-Eugenol Cement; C534916:epoxy resin-based root canal sealer; C045432:Grossman's sealer; C048769:tubliseal; D002126:Calcium Hydroxide