Objective

The aim of the study was to identify experimental limits of the general reciprocity hypothesis that the same photo-cure outcomes will result from applying essentially constant energy densities, despite reciprocal variations in the irradiance and irradiation time-period, for a representative set of bulk fill (BF) and non-BF resin composites.

Methods

Six BF and two non-BF resin-composites were selected. The unset pastes were inserted into white acetal molds (5 mm id) with (n = 6) depths (1, 2, 3, 4, 5 and 6 mm). Three light curing units (LCUs) of increasing radiant emittance capability: 1200, 2000 and 3200 mW/cm² were used. Composite specimen groups (n = 3, per depth, per LCU) were irradiated on the upper surface only. For each specific composite, the irradiation times for each LCU were reduced reciprocally, as the LCU irradiance increased, to deliver a constant energy density (J/cm²) to that composite. However, the required energy density for a given composite differed in accordance with each composite manufacturer recommendations. After storing for 24 h at 37 °C, light transmission measurements were made through each specimen and re-expressed as Apparent Absorbance (A′). Vickers hardness (H_V) measurements (n = 10) were made on both top and bottom surfaces, for each specimen, and H_V versus “depth” profile plots created. From the top-surface data, a Depth-of-Cure parameter could be derived. Data were statistically evaluated for differences between top and bottom H_V values and for other predefined variables of interest.

Results

Irradiation with the LCU of 1200 mW/cm² generally gave the highest H_V/depth for most materials tested compared to the other curing lights with higher power output, regardless of top and bottom measurements (p < 0.001). However, this difference was material-dependent. With one BF composite, 1200 and 2000 mW/cm² irradiance did not show a significant difference between top and bottom H_V. Composites with higher translucency showed reduced differences in top/bottom H_V than more opaque composites.

Significance

Reciprocity was found to be limited with most materials examined, such that irradiance periods of 10 s, gave generally better H_V outcomes than by using LCUs of superior radiant emittance while reciprocally reducing irradiance time to maintain constant dose of energy density.

中文翻译：

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填充树脂复合材料固化效率的互易性有限。

目的

该研究的目的是确定一般互易性假设的实验极限，即对于一组代表性的散装填充物，尽管辐照度和辐照时间周期互不相同，但通过施加基本恒定的能量密度将产生相同的光固化结果（BF）和非BF树脂复合材料。

方法

选择了六种高炉树脂和两种非高炉树脂复合材料。将未凝固的糊状物插入 深度为（1、2、3、4、5和6毫米）的白色乙缩醛模具（内径5毫米）中（n = 6）。使用三个增加辐射发射能力的光固化单元（LCU）：1200、2000和3200 mW / cm ²。仅在上表面辐照复合标本组（每深度每LCU n  = 3 ）。对于每种特定的复合材料，随着LCU辐照度的增加，每个LCU的辐照时间会相应减少，以提供恒定的能量密度（J / cm ²）到该复合材料。但是，给定复合材料所需的能量密度根据每个复合材料制造商的建议而有所不同。在37°C下保存24小时后，通过每个样品进行透光率测量，并重新表示为表观吸光度（A '）。 在每个样品的顶部和底部表面均进行了维氏硬度（H _V）测量（n = 10），并创建了H _V 与“深度”轮廓图。从顶表面数据可以得出固化深度参数。对数据的最高和最低H _V值之间的差异以及其他感兴趣的预定义变量进行统计评估。

结果

与其他具有较高功率输出的固化灯相比，无论顶部和底部的尺寸如何，LCU 1200 mW / cm ^2的辐照通常能使大多数被测材料产生最高的H _V /深度（p  <0.001）。但是，这种差异取决于材料。对于一种高炉复合材料，顶部和底部H _V之间的1200和2000 mW / cm ²辐照度没有显着差异。与不透明的复合材料相比，具有较高半透明性的复合材料在顶部/底部H _V上的差异减小。

意义

发现对大多数被检查的材料来说，互易性受到限制，因此，与使用具有较高辐射发射的LCU相比，辐照时间10 s通常会产生更好的H _V结果，同时相互降低辐照时间以保持恒定剂量的能量密度。