Shirazinia Mahdieh, Mehmandoost-Khajeh-Dad Ali Akbar, Dehghani Vahid, Mehmandoost-Khajeh-Dad Jamshid, Khaghani Morteza
University of Sistan and Baluchestan, Zahedan, Iran.
Faculty of Dentistry, Zahedan University of Medical Sciences, Zahedan, Iran.
Polim Med. 2016 Jul-Dec;46(2):129-133. doi: 10.17219/pim/68647.
Dental composite resins - reinforced polymers - are types of synthetic resins that are used in dentistry as restorative material or adhesives. The effect of curing-light intensity on free volume sizes of 4 commercial dental composites has been studied by means of the well-known positron annihilation lifetime spectroscopy technique.
The aim of the study was to compare the photosensitivity of 4 commercial dimethacrylate-based dental composites.
Positron lifetime spectra were collected using a slow-fast coincidence lifetime spectrometer with a time resolution of 365 ps. The positron source was a ~20 μCi 22Na beta emitter between two 7 μm thick stainless steel foils. The positron source was sandwiched between two identical samples under investigation. The 1st group of samples was polymerized by a 20-second photo-exposure, and the 2nd group of samples was irradiated by the blue curing light for 40 s. The positron annihilation lifetime spectrums were separated into components using the PAScual Positron Annihilation Spectroscopy data analysis program.
The results showed that the lifetime component associated with free volumes differed in the different composites and depended on the irradiation time. The results indicated that the Coltene composite has higher photosensitivity than the other samples; the Denfil composite exhibited the lowest photosensitivity of the 4.
The appropriate light-curing intensity depends on the thickness of the composite, which in turn is proportional to the depth of the hole in the tooth undergoing repair.
牙科复合树脂——增强聚合物——是一类合成树脂，在牙科中用作修复材料或粘合剂。已通过著名的正电子湮没寿命谱技术研究了固化光强度对4种商用牙科复合材料自由体积尺寸的影响。
本研究旨在比较4种商用双甲基丙烯酸酯基牙科复合材料的光敏性。
使用时间分辨率为365皮秒的快慢符合寿命谱仪收集正电子寿命谱。正电子源是夹在两个7微米厚不锈钢箔之间的约20微居里的22Naβ发射体。正电子源夹在两个相同的待测样品之间。第一组样品通过20秒的光曝光进行聚合，第二组样品用蓝色固化光照射40秒。使用PAScual正电子湮没光谱数据分析程序将正电子湮没寿命谱分离成组分。
结果表明，与自由体积相关的寿命组分在不同的复合材料中有所不同，并且取决于照射时间。结果表明，科尔tene复合材料比其他样品具有更高的光敏性；Denfil复合材料在这4种材料中光敏性最低。
合适的光固化强度取决于复合材料的厚度，而复合材料的厚度又与正在修复的牙齿洞的深度成正比。
