Flexural properties, microleakage, and degree of conversion of a resin polymerized with conventional light and argon laser.
OBJECTIVE
To evaluate the flexural strength, microleakage, and degree of conversion of a microhybrid resin polymerized with argon laser and halogen lamp.


METHODS
For both flexural test and degree of conversion analysis, 5 bar samples of composite resin were prepared and polymerized according to ISO 4049. The halogen light-curing unit was used with 500 mW/cm(2) for 20 seconds and the argon laser with 250 mW for 10 and 20 seconds. Samples were stored in distilled water in a dark environment at 37 degrees C for 24 hours. The flexural property was quantified by a 3-point loading test. For the microleakage evaluation, 60 bovine incisors were used to prepare standardized Class 5 cavities, which were restored and polished. Specimens were stored in distilled water for 24 hours at 37 degrees C and thermocycled 500 times (6 degrees C to 60 degrees C). Specimens were then immersed in an aqueous solution of basic fuchsin for 24 hours. Longitudinal sections of each restoration were obtained and examined with a stereomicroscope for qualitative evaluation of microleakage. Fourier transform (FT)-Raman RFS 100/S spectrometer (Bruker) was used to analyze the degree of conversion.


RESULTS
ANOVA showed no statistically significant differences of flexural strength between the photoactivation types evaluated in the flexural study. Microleakage data were statistically analyzed by Mann-Whitney and Kruskal-Wallis tests. Enamel margins resulted in a statistically lower degree of leakage than dentin margins. No statistically significant difference was found among the 3 types of photocuring studied. ANOVA also showed no statistically significant difference in the degree of conversion among the studied groups.


CONCLUSIONS
According to the methodology used in this research, the argon laser is a possible alternative for photocuring, providing the same quality of polymerization as the halogen lamp. None of the photocured units tested in this study completely eliminated microleakage.
Ramos Lloret
Patricia
P
Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, Brazil. prlloret@usp.br
Lacalle Turbino
Miriam
M
Kawano
Yoshio
Y
Sanchez Aguilera
Fatima
F
Osorio
Raquel
R
Toledano
Manuel
M
D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000528:radiation effects*; D055117:Curing Lights, Dental; D003763:Dental Leakage / Q000517:prevention & control*; D018772:Dental Marginal Adaptation; D003799:Dental Stress Analysis; D006219:Halogens; D006244:Hardness; D054025:Lasers, Dye; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D044367:Phase Transition; D018583:Pliability
D003188:Composite Resins; C444701:Filtek Z250; D006219:Halogens