عنوان انگلیسی مقاله:
Resin viscosity determines the condition for a valid exposure reciprocity law in dental composites
ترجمه فارسی عنوان مقاله:
ویسکوزیته رزین شرایط برای یک قانون قرار گرفتن در معرض متقابل معتبر در کامپوزیت دندان تعیین
Sciencedirect - Elsevier - Dental Materials, 36 (2020) 310-319: doi:10:1016/j:dental:2019:12:003
Sri Vikram Palagummia, Taeseung Honga,c, Zhengzhi Wangb,Chang Kwon Moonc, Martin Y.M. Chianga
tObjective. To provide conditions for the validity of the exposure reciprocity law as it pertainsto the photopolymerization of dimethacrylate-based dental composites.Methods. Composites made from different mass ratios of resin blends (Bis-GMA/TEGDMAand UDMA/TEGDMA) and silanized micro-sized glass fillers were used. All the compositesused camphorquinone and ethyl 4-dimethylaminobenzoate as the photo initiator system.A cantilever beam-based instrument (NIST SRI 6005) coupled with NIR spectroscopy and amicroprobe 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 lightcuring unit providing irradiances ranging from 0.01 W/cm2to 4 W/cm2at a peak wavelengthof 460 nm (blue light). Vickers hardness of the composites was also measured.Results. For every dental composite there exists a minimum radiant exposure required foran adequate polymerization (i.e., insignificant increase in polymerization with any furtherincrease in the radiant exposure). This minimum predominantly depends on the resin vis-cosity of composite and can be predicted using an empirical equation established based onthe test results. If the radiant exposure is above this minimum, the exposure reciprocitylaw is valid with respect to DC for high-fill composites (filler contents >50% by mass) whileinvalid for low-fill composites (that are clinically irrelevant).Significance. The study promotes better understanding on the applicability of the exposurereciprocity law for dental composites. It also provides a guidance for altering the radiantexposure, with the clinically available curing light unit, needed to adequately cure the dentalcomposite in question.
Keywords:Photopolymerization | Exposure reciprocity law | Radiant exposure | Irradiance | Autodeceleration | Polymerization exotherm