Objective. The purpose of this study was to establish a new method for
the determination of working time and gelation time of temporary soft
lining materials using a displacement rheometer. Method. A displaceme
nt rheometer (The Dental School, University of Newcastle, Newcastle up
on Tyne, UK) was used to apply a rapid displacement of 0.25 mm held fo
r 1 s at intervals of 60 s to samples of four temporary soft lining ma
terials. Material displacement and elastic recovery at each test time
was recorded. The test procedure was repeated three times at 23 degree
s C and at 37 degrees C for each material. For one material, the displ
acement time was varied (1, 5, 10 s). The working time was defined as
the time corresponding to the initial observation of elastic recovery
at 23 degrees C. Gelation time was the time when a material achieved 9
5% of its maximum elastic recovery at 37 degrees C. Values were compar
ed between materials using one-way analysis of variance and Student-Ne
wman-Keuls test at the 5% level of significance. Results. The gelation
rate of all materials increased with increasing temperature although
the extent of this influence varied between materials. The development
of elastic recovery in the materials during gelation accurately fitte
d asymmetric sigmoids. The correlation coefficient (r) ranged from 0.9
82 to 0.999. Statistically significant variations in both the working
and gelation times of the test materials were established. The time of
displacement affected both the rate of development of elasticity and
the value of elastic recovery but this effect was only statistically s
ignificant when the displacement time was increased to 10 s. Significa
nce. The displacement rheometer may be suited for use as a standard te
st method for the determination of the working time, gelation lime and
elastic behavior of temporary soft lining materials.