Effect of different modes of light modulation on the bond strength and knoop hardness of a dental composite.
This study evaluated the bond strength and Knoop hardness of Z250 composite resin, light activated with XL2500 curing unit, using different protocols: continuous mode - high intensity (CH) (700 mW/cm(2)) for 20 s; continuous mode - low intensity (CL) (150 mW/cm(2)) for 20 s; and pulse-delay with 150 mW/cm(2) for 2(P2), 3(P3), 5(P5), 10(P10) or 15 s (P15), with a 1-min delay, followed by 700 mW/cm(2) for 20 s. For the push-out test (n=10), the bond strength values were obtained using a universal test machine at a crosshead speed of 0.5 mm/min. For Knoop hardness (n=5), the specimens were made using the same light-activation protocols. The hardness measurements were made with a hardness tester at six depths (top, 1, 2, 3, 4, and 5 mm). The data were subjected to ANOVA and Tukey's test at 5% significance level. For bond strength, CL and P5 presented significantly higher mean values (p<0.05) than the other groups. There was no statistically significant difference (p>0.05) between P2, P3, P10, P15 and CH. For Knoop hardness, CH and P15 presented the highest mean values from top surface up to 4 mm depth , while CL presented the lowest hardness mean values (p<0.05). From the depth of 3 mm to 5 mm, the mean values of all groups were significantly lower (p<0.05) than those recorded on top surface. In conclusion, for the pulse-delay method, the initial exposure time can influence bond strength and Knoop hardness of composites.
Dalli'Magro
Eduardo
E
Dental Materials Area, Department of Restorative Dentistry, Dental School of Piracicaba, State University of Campinas, Piracicaba, SP, Brazil.
Sinhoreti
Mário Alexandre Coelho
MA
Correr
Américo Bortolazzo
AB
Consani
Rafael Leonardo Xediek
RL
Sicoli
Eliseu Augusto
EA
Mendoça
Marcio José
MJ
Correr-Sobrinho
Lourenço
L
D003188:Composite Resins / Q000528:radiation effects*; D003793:Dental Restoration, Permanent / Q000379:methods; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents / Q000528:radiation effects*; D006244:Hardness; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects*; D013997:Time Factors
D003188:Composite Resins; D017220:Dentin-Bonding Agents; C444701:Filtek Z250; D019279:Resin Cements