Pre-heating effects on extrusion force, stickiness and packability of resin-based composite.

Objectives: To measure temperature effects on stickiness and packability of representative resin-based composites and the effect of pre-heating time on pre-cure properties of Viscalor, including extrusion force.

Methods: Five resin-based composites (RBC) and an additional RBC, Viscalor, used with a Caps Warmer (VOCO, Germany) were studied. The extrusion force (N) and extruded mass (g) were measured from Viscalor compules heated in T3 mode for 30s (T3-30s) and 3min (T3-3min). For stickiness and packability measurements, RBCs were packed into a brass cylindrical cavity controlled at 22 and 37°C. A flat-ended probe was lowered into the RBC pastes at constant speed. Stickiness: F (N) and W (N mm), and packability: F (N), were measured. Viscalor was LED photo-cured at 1200mW/cm for 40s. The degrees of conversion at 5min and 24h post cure (DC and DC) of Viscalor (no heat, T3-30s and T3-3min) were measured by ATR-FTIR. Data were analysed by one-way ANOVA, independent t-test and Tukey post-hoc tests (p<0.05).

Results: The maximum temperature of the Caps Warmer, in T3 mode, reached 68°C in 20min. Viscalor temperatures of 34.5°C and 60.6°C were recorded after 30s and 3min pre-heating, respectively. Pre-heating significantly reduced extrusion force and increased extruded mass, especially after 3min. RBCs varied in F, W and F (p<0.05). Temperature also affected F (p=0.000), W (p=0.002) and F (p=0.000). Pre-heating Viscalor for either 30s or 3min did not increase the post-cure DC at either 5min or 24h, relative to no pre-heating (p>0.05).

Significance: The composites varied to an extent in stickiness and packability but the overall magnitudes remained within a clinically acceptable range. Pre-heating was beneficial in placement of Viscalor and caused no adverse effects through premature polymerization.