Effect on Superficial Hardness of Different Curing Intensities

Objectives: To compare the superficial hardness of different composite resins using three different curing intensities and methods.

Methods: 60 disks 6 mm diameter and 3 m thick were made using composite resins, Filtek Supreme XT, Filtek Valux and Heliomolar, all shades were A2 (n=20). Groups were divided into three each to be cured for 20 seconds with different light curing units: Heraeus Kulzer's Translux Power Blue, Hilux's LEDmax using the Ramp curing and the high intensity curing settings and 3M's Elipar 2500, only on one side of the specimens. All samples were stored covered in brown paper to prevent any light reaching the composite resin. Twenty four hours later, they were tested for Vickers Superficial hardness (Micromed2001, Buehler) with 0.2 kg. of pressure for 10 seconds on both sides, the upper side hit by the curing light, and the opposite side. Data were store in VHN and analyzed using a two-way analysis of variance calculated at 0.05 significance level.

Results: Fisher's PLSD intervals for comparisons among composites and among curing methods and between cured surfaces were 3.2, 3.6 and 2.6 respectively. Composite Heliomolar did not cured at 3 mm depth, light side showed no difference among curing units. VHN of opposite side of composites XT and Valux were 75% and 87% of the VHN on the light curing side. XT was affected significantly by all curing systems evaluated, LEDmax using the high intensity curing cycle produced the highest VHN in both the light side and the opposite side. Valux had the highest VHN when cured with XXX and Elipar produced the lowest of the opposite side.

Conclusions: Curing units produced different amounts of polimerization for composites evaluated. The ability to cure at higher depths is more determined by the composite and not by the curing unit or its light intensity.