Influence of light curing source on microhardness of composite resins of different shades.
BACKGROUND
The evolution of light curing units can be noticed by the different systems recently introduced. The technology of LED units promises longer lifetime, without heating and with production of specific light for activation of camphorquinone. However, further studies are still required to check the real curing effectiveness of these units.


OBJECTIVE
This study evaluated the microhardness of 4 shades (B-0.5, B-1, B-2 and B-3) of composite resin Filtek Z-250 (3M ESPE) after light curing with 4 light sources, being one halogen (Ultralux - Dabi Atlante) and three LED (Ultraled - Dabi Atlante, Ultrablue - DMC and Elipar Freelight - 3M ESPE).


METHODS
192 specimens were distributed into 16 groups, and materials were inserted in a single increment in cylindrical templates measuring 4mm x 4mm and light cured as recommended by the manufacturer. Then, they were submitted to microhardness test on the top and bottom aspects of the cylinders.


RESULTS
The hardness values achieved were submitted to analysis of variance and to Tukey test at 5% confidence level. It was observed that microhardness of specimens varied according to the shade of the material and light sources employed. The LED appliance emitting greater light intensity provided the highest hardness values with shade B-0.5, allowing the best curing. On the other hand, appliances with low light intensity were the least effective. It was also observed that the bottom of specimens was more sensitive to changes in shade.


CONCLUSIONS
Light intensity of LED light curing units is fundamental for their good functioning, especially when applied in resins with darker shades.
Briso
André Luiz Fraga
AL
Department of Restorative Dentistry of Araçatuba Dental School - State University of São Paulo Paulo-UNESP - Araçatuba, São Paulo, Brazil. alfbriso@foa.unesp.br
Fedel
Tânia Maria
TM
Pereira
Sibéria de Morais
Sde M
Mauro
Sílvio José
SJ
Sundfeld
Renato Herman
RH
Sundefeld
Maria Lúcia Marçal Mazza
ML