研究目的
To compare the hardness of a photoactivated composite resin using the pulse-delay, soft start and conventional techniques, in thicknesses of 1, 2 and 3 mm in the irradiated surface and in the opposite surface.
研究成果
The hardness was higher with photoactivation of 40 seconds (pulse-delay technique) and for the conventional and soft start techniques (20 seconds) there was no difference in terms of hardness. Therefore, hardness is not influenced by the technique, but rather, by the polymerization time.
研究不足
The study focused on the hardness of composite resins and did not explore other mechanical properties or the clinical performance of the restorations. The photoactivation techniques were compared based on hardness alone, without considering other factors such as polymerization contraction or degree of conversion.
1：Experimental Design and Method Selection:
The study compared the hardness of a photoactivated composite resin using three different photoactivation techniques (pulse-delay, soft start, and conventional) across three thicknesses (1, 2, and 3 mm).
2：Sample Selection and Data Sources:
Forty-five samples were prepared, distributed in 9 groups with 5 samples in each, according to the thickness of the matrix and the photoactivation technique.
3：List of Experimental Equipment and Materials:
Composite resin Filtek? Z350 (3M ESPE), halogen light (Degulux SoftStart?, Degussa-Hulls), and a microhardness tester (HMV-2000, Shimadzu Co.).
4：Experimental Procedures and Operational Workflow:
Photoactivation was performed with halogen light for 20 seconds in the conventional and soft start techniques. In the pulse-delay technique, each increment of 1 mm was photoactivated for 3 seconds with a final photoactivation of 40 seconds. The samples were stored in an oven at 37°C for one week and submitted to the Vickers microhardness test.
5：Data Analysis Methods:
The results were submitted to ANOVA and the Tukey’s test with a level of significance of 5%.
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