Abstract
To evaluate the shrinkage-strain, degree of conversion (DC) and percent filler of a range of flowable resin-composites.
Several commercially available flowable resin-composites were selected. The bonded-disk technique was used to measure shrinkage-strain kinetics. Measurements were obtained continuously for 60
min by irradiation for 40
s at 750
mW/cm
2 at two initial temperatures of 23 and 37
°C. Three repetitions (
n
=
3) were made at each temperature per material. The DC was measured by FTIR spectroscopy immediately post-cure. The percent filler was determined by combustion of specimens for 1
h at 400
°C.
The final values of shrinkage-strain ranged from 2.61 to 6.25% at 23
°C and from 3.88 to 6.56% at 37
°C. Statistically significant differences (
p
<
0.05) were found in shrinkage-strain between the flowable resin-composites at both temperatures 23 and 37
°C. Significantly higher values were obtained at 37
°C (
p
<
0.05). A strong inverse correlation was found between the percent filler and the shrinkage-strain at 37 and 23
°C (
r
2
=
0.94 and 0.87, respectively). No correlation was found between shrinkage-strain and DC (
p
>
0.05).
Flowable resin-composites vary widely in shrinkage-strain magnitude and the inverse relationship between filler percent and shrinkage-strain is explained by the corresponding decrease in volume fraction of monomers present to undergo polymerisation.