Method for Evaluation of Slumping Resistance of Resin Composites

Slumping resistance is an important handling characteristic of resin composites that prevents the undesirable displacement of a material due to its own weight. Since creep is deformation under a constant stress over time, creep resistance might be predictive of slumping resistance. Objective: The objective of this study was to develop a method for evaluating slumping resistance based on a creep test. Materials and Methods: Six high-viscosity resin composites – Esthet-X HD (Dentsply Caulk) (EH), SonicFill (Kerr Dental) (SF), Herculite Ultra (Kerr Dental) (HU), Filtek Supreme Ultra (3M ESPE) (FS), Tetric EvoCeram (Ivoclar-Vivadent) (TE), and Grandio (Voco) (GR) were tested. A small amount of resin paste was dispensed on the lower plate of a rheometer (AR1000, TA instruments) maintained at 32۫C. Then, a 8mm diameter parallel plate geometry was positioned 2mm above the lower plate, and the excess paste was removed. Creep testing was performed at a constant shear stress of 400Pa for 2 minutes, and the percent strain was recorded (N=6). The log transformed data were analyzed using ANOVA and Tukey’s HSD method (α=0.05). Results: The mean and standard deviation of percent strains for each material are summarized in the table. EH exhibited significantly lower percent strain than other materials. TE and GR showed significantly higher percent strain than others, and hence the least slumping resistance. The subjective evaluation of materials for slumping resistance exhibited a similar order.

Material	% Strain (SD)1	Slump Observation2
EH	1.37(0.37)a	1
SF	3.19(0.51)b	2
HU	3.94(0.47)bc	1
FS	5.17(0.71)c	1
TE	46.2(5.64)d	3
GR	57.0(6.93)d	4
1. Different letter superscripts indicate a significant difference. 2. Score: 1 – least slump, 4 – most slump.

Conclusion: Creep testing is a useful method for evaluation of the slumping resistance of resin composites.