OBJECTIVE To provide conditions for the validity of the exposure reciprocity law as it pertains to the photopolymerization of dimethacrylate-based dental composites. METHODS Composites made from different mass ratios of resin blends (Bis-GMA/TEGDMA and UDMA/TEGDMA) and silanized micro-sized glass fillers were used. All the composites used camphorquinone and ethyl 4-dimethylaminobenzoate as the photo initiator system. A cantilever beam-based instrument (NIST SRI 6005) coupled with NIR spectroscopy and a microprobe thermocouple was used to simultaneously measure the degree of conversion (DC), the polymerization stress (PS) due to the shrinkage, and the temperature change (TC) in real time during the photocuring process. The instrument has an integrated LED light curing unit providing irradiances ranging from 0.01W/cm2 to 4W/cm2 at a peak wavelength of 460nm (blue light). Vickers hardness of the composites was also measured. RESULTS For every dental composite there exists a minimum radiant exposure required for an adequate polymerization (i.e., insignificant increase in polymerization with any further increase in the radiant exposure). This minimum predominantly depends on the resin viscosity of composite and can be predicted using an empirical equation established based on the test results. If the radiant exposure is above this minimum, the exposure reciprocity law is valid with respect to DC for high-fill composites (filler contents >50% by mass) while invalid for low-fill composites (that are clinically irrelevant). SIGNIFICANCE The study promotes better understanding on the applicability of the exposure reciprocity law for dental composites. It also provides a guidance for altering the radiant exposure, with the clinically available curing light unit, needed to adequately cure the dental composite in question.

中文翻译：

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树脂粘度决定了牙科复合材料中有效暴露互易定律的条件。

目的为曝光互易定律的有效性提供条件，因为该定律与基于二甲基丙烯酸酯的牙科复合材料的光聚合有关。方法使用由不同质量比的树脂共混物（Bis-GMA / TEGDMA和UDMA / TEGDMA）和硅烷化的微尺寸玻璃填料制成的复合材料。所有复合材料均使用樟脑醌和4-二甲基氨基苯甲酸乙酯作为光引发剂体系。基于悬臂梁的仪器（NIST SRI 6005）与NIR光谱仪和微探针热电偶相结合，可同时测量转化率（DC），收缩引起的聚合应力（PS）和温度变化（TC）在光固化过程中实时进行。该仪器具有集成的LED光固化单元，提供的辐射范围为0。峰值波长460nm（蓝光）为01W / cm2至4W / cm2。还测量了复合材料的维氏硬度。结果对于每种牙科复合材料，都有足够的聚合所需的最低辐射暴露（即聚合显着增加，而辐射暴露则进一步增加）。该最小值主要取决于复合材料的树脂粘度，可以使用基于测试结果建立的经验方程式进行预测。如果辐射暴露高于该最小值，则对于高填充复合材料（填充剂含量> 50质量％），对于DC而言，暴露互易定律是有效的，而对于低填充复合材料（在临床上是无关紧要的），暴露互易性法则无效。意义该研究促进了对牙科复合材料的暴露互易定律的适用性的更好理解。