Methods: The composites investigated were: Filtek Z250 (FZ) and Filtek Supreme XT (SU) (3M ESPE), Esthet-X (EX) (Dentsply) and Point 4 (P4) (SDS-Kerr). They were light cured by: c and pd (20J/cm2) and submitted or not to heat treatment (HT) at 100 or 170ºC for 10min (Flii Manfredi, Italy). DC measurements (discs: 4mm x 1mm; n=3) were obtained by FT-Raman spectroscopy (Brüker Optics, USA): 4cm-1 resolution, 64 scans between 2000 and 100cm-1, ages: uncured, immediately, 1h, 6h and 24h after photoactivation, after HT at 100ºC/10min and 170ºC/10min. KHN measurements (5 x 2 x 2 mm; n=5) were obtained by indentations (Shimadzu HMV-2, Japan), with 50g load, dwell time of 15s, on the irradiated and opposite surfaces (3 indentations each), ages: immediately and 24h after photoactivation, after HT at 100ºC/10min and 170ºC/10min. Data were analyzed by ANOVA and Tukey's test (a=.05).
Results: DC: ANOVA pointed high significance for the factors: activation mode (p=.006) (c>pd), age (p=.000) (HT170=HT100>24h=6h>1h=immediately), material (p=.000) (P4>EX=FZ>SU) and for the interactions: material x age (p=.007) and material x age x activation mode (p=.013). KHN: ANOVA pointed high significance for the factors: activation-material (p=.000) (c-FZ>pd-FZ>c-SU=pd-SU>c-EX=c-P4=pd-P4=pd-EX), ages (p=.000) (HT170=24h>HT100>immediately) and for the interactions: face x activation-material (p=.000), face x age (p=.000) and face x activation-material x age (p=.000).
Conclusion: The post cure heat treatment is capable of increasing degree of conversion of the studied composites. 170ºC samples presented higher hardness in relation to 100ºC, although similar DC.