THERMOCYCLING - THE EFFECTS UPON THE COMPRESSIVE STRENGTH AND ABRASION RESISTANCE OF 3 COMPOSITE RESINS

The purpose of this investigation was to examine the effects of thermocycling upon the compressive strength and abrasive wear resistance of three commercial composites Fulfil(R), P-50(R) and Herculite-XR(R). Specimens of each material were divided into five treatment groups comprising a control, and four different cycling and storage regimes. Tests for compressive strength and wear resistance were carried out. Prior to testing all specimens were stored in distilled water for 1 week. Three groups were stored at a temperature of 37-degrees-C and the remaining two at 60-degrees-C. Thereafter all groups that were thermocycled were subjected to 750 cycles of a thermocycling regime consisting of the cycle ACAB where A and B represent the fixed temperatures of 37-degrees-C and 5-degrees-C, and C, depending upon the treatment group, either 50-degrees-C or 60-degrees-C. One-way analyses of variance upon the compressive strength and wear factor data following the treatments highlighted significant differences in the mean compressive strength for all materials (Fulfil (P < 0.05), P-50 and Herculite-XR (P < 0.01)) and in the wear factor values for only Fulfil and P-50 (P < 0.001). Surprisingly, thermocycling P-50 with an upper temperature limit of 50-degrees-C had catastrophic consequences upon the measured properties. It is concluded that some of the observed behaviour may have potentially detrimental consequences upon the long-term clinical durability of the materials tested.