Efficiency of polymerization with blue light emitting diode [LED] and halogen based light curing units on microhardness, depth of cure and flexural strength of nanofilled composite resin
EDJ-Egyptian Dental Journal. 2004; 50 (2 Part II): 1007-1018
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| ID: emr-203995
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EMRO
New light -activation units equipped with blue light emitting diodes [LEDs] have recently been proposed as a replacement for halogen units to polymerize composite resins. This study investigated the effectiveness of composite curing by Quartz tungsten halogen [QTH] and light emitting diode [LED] light curing units [LCUs] on the microhardness, depth of cure and flexural strength of nanofilled composite [Filtek Supreme]
Methods: A digital microhardness tester was used to evaluate the Vickers hardness number [NHN] of the top and bottom surfaces of the 1mm and 2mm thick composite disc specimens. All specimens were irradiated for 40 seconds exposure time with 1] QTH light in standard continuous mode and 2] in "soft start mode" as well as with 3] LED LCU. 10 specimens were evaluated for each of these conditions with two different thicknesses making a total of 60 specimens. Bottom to top B/T hardness ratio was calculated to determine the percentage of cure. Depth of cure was also evaluated for 6 specimens 4 mm diameter. 6mm depth for each condition using a penetrometer method. Flexural strength was determined for the same conditions according to the ISO specification 4049. Groups were compared using one way ANOVA and Fisher's LSD as well as student's test
Results: Significant differences in VHN in specimens cured with either LCUs at the top of the 1 and 2mm specimens, were observed with lower values when using the LED LCU. Higher hardness values were recorded on the top surfaces of all specimens compared to the bottom surfaces. The depth of cure of shade A3 composite cured using the conventional halogen LCU in both standard and soft start modes was significantly deeper [5.16, 5.06 mm] respectively [p<0.05] than the LED LCU [3.74 mm]. The flexural strength of specimens cured using the LED was significantly lower [p< 0.04] than that cured with the halogen LCU used with either modes. However the results obtained with both units exceeded the minimal requirements described in the ISO 4049
Conclusions: The differences in the irradiances of the two light curing units used in this study reflected significant differences in the microhardness, depth of cure and flexural strength properties of the composite resin
Methods: A digital microhardness tester was used to evaluate the Vickers hardness number [NHN] of the top and bottom surfaces of the 1mm and 2mm thick composite disc specimens. All specimens were irradiated for 40 seconds exposure time with 1] QTH light in standard continuous mode and 2] in "soft start mode" as well as with 3] LED LCU. 10 specimens were evaluated for each of these conditions with two different thicknesses making a total of 60 specimens. Bottom to top B/T hardness ratio was calculated to determine the percentage of cure. Depth of cure was also evaluated for 6 specimens 4 mm diameter. 6mm depth for each condition using a penetrometer method. Flexural strength was determined for the same conditions according to the ISO specification 4049. Groups were compared using one way ANOVA and Fisher's LSD as well as student's test
Results: Significant differences in VHN in specimens cured with either LCUs at the top of the 1 and 2mm specimens, were observed with lower values when using the LED LCU. Higher hardness values were recorded on the top surfaces of all specimens compared to the bottom surfaces. The depth of cure of shade A3 composite cured using the conventional halogen LCU in both standard and soft start modes was significantly deeper [5.16, 5.06 mm] respectively [p<0.05] than the LED LCU [3.74 mm]. The flexural strength of specimens cured using the LED was significantly lower [p< 0.04] than that cured with the halogen LCU used with either modes. However the results obtained with both units exceeded the minimal requirements described in the ISO 4049
Conclusions: The differences in the irradiances of the two light curing units used in this study reflected significant differences in the microhardness, depth of cure and flexural strength properties of the composite resin
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IMEMR
Idioma:
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Revista:
Egypt. Dent. J.
Ano de publicação:
2004