The effect of thermocycling on the fatigue behavior of dental composites

The effect of thermocycling on the fatigue behaviour of 2 microfilled composites; Silux Plus3 and Heliomolar2 and 3 hybrid composites; P502, Cleafil Photo Posterior3 (both light-activated) and Cleafil Posterior3 (chemically-activated) was investigated using a ball mill. Ninety specimens (2 x 2 x 25mm) of each material were used. The specimes were divided into 3 groups of 30 and were stored for 24 h in water at 37oC (Group A), subjected to 104 thermal cycle over 45 days (Group B) and stored in water at 37oC for 45 days (Group C). Ten specimens of each material were tested in a 0.5 litre capacity ceramic ball mill4 which was rotated at 100 rev/min. This procedure was repeated 3 times. The mill was charged with 470g steatite balls and 250m1 distilled water. At 30 minute intervals the number of fractured specimens was noted. All fractured and intact specimens were returned to the ball mill and the process repeated up to 5 hours. T'he mean survival time (mins) for P50 were >300(A), 85(B) and 130(C); Silux >300(A), 76(B) and 110(C); Heliomolar >300(A), 240(B) and >300(A); Clearfi Photo >300(A), >300(B), >300(C) and Cleafil Posterior >300(A), 165(B) and 160(C). Group A is significantly different (P< .05) from Groups B and C for all materials except Cearfil1 Photo Posterior. Howver, significant differences (P<.05) between Group B and C wan only observed in P50 and Silux. The fatigue behaviour of P50 and Silux is affected by thermocycling. 13M, St Paul,USA; 2Vivadent, Liechtenstein; 3Kuraray, Japan; 4Pascal Engineering, UK