研究目的
To evaluate the degree of conversion (DC) and hardness of composite resins photoactivated in different power densities and curing times.
研究成果
Higher power densities of the curing unit lead to increased degree of conversion and hardness of composite resins. A power density of 100 mW/cm2 is insufficient for satisfactory polymerization, regardless of curing time, compromising clinical performance. Optimal results were achieved with power densities of 400 mW/cm2 or higher.
研究不足
The study is limited to in vitro conditions and may not fully replicate clinical scenarios. Only one type of composite resin was tested, and results might not generalize to other materials. The power densities and times used are specific and may not cover all possible variations in clinical practice.
1：Experimental Design and Method Selection:
The study used a factorial design with two factors (power density and curing time) to evaluate the degree of conversion and hardness of composite resins. Specimens were prepared and photoactivated under controlled conditions, followed by storage and testing using FT-IR spectroscopy for degree of conversion and a digital durometer for hardness. Statistical analysis included ANOVA and Tukey's post-hoc test.
2：Sample Selection and Data Sources:
Eighty specimens of composite resin (FiltekTM Z350 XT, color A2B) were fabricated with dimensions of 4 mm diameter and 2 mm thickness, divided into groups based on power density (1000, 700, 400, 100 mW/cm2) and curing time (20 and 40 seconds).
3：List of Experimental Equipment and Materials:
Composite resin (FiltekTM Z350 XT), metal matrix (4 mm diameter, 2 mm thickness), glass plate, polyester strip, 1 kg metal weight, LED curing unit (Optilight LD MAX), radiometer (RD-7), FT-IR spectrophotometer (Spectrum 65), digital durometer (MV 2000A).
4：Experimental Procedures and Operational Workflow:
Specimens were prepared by placing resin in a metal matrix, covering with a polyester strip and weight, and photoactivating with the LED unit. Power density was verified with a radiometer before curing. Specimens were stored in dark containers at 37°C for 7 days. Degree of conversion was measured using FT-IR spectroscopy, and hardness was measured with a digital durometer using a 50 gf load for 15 seconds.
5：Data Analysis Methods:
Data were analyzed using two-way ANOVA and Tukey's post-hoc test at a 5% significance level to compare means across groups.
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