Jafari Navimipour Elmira, Pournaghi Azar Fatemeh, Keshipour Sajjad, Nadervand Saba
Department of Operative Dentistry, Dental Faculty, Tabriz University of Medical Sciences, Tabriz, Iran.
Department of Nanotechnology, Nanoresearch Center, Urmia University, Urmia, Iran.
Front Dent. 2021 Apr 7;18:9. doi: 10.18502/fid.v18i9.6102. eCollection 2021.
This study aimed to evaluate the thermal stability and monomer elution of bulk fill composite resins cured at different irradiation distances. Forty cylindrical-shaped (3×4mm) specimens were fabricated from two composite resins (X-tra fil, X-tra base) and cured from 0 and 7mm distances. In 9 specimens, the degree of conversion was determined by the release of monomers. For this purpose, after curing of composites, they were immersed in 5 mL of 99.9% methanol and stored at 37°C for 24h. The eluted monomer was then analyzed by gas chromatography (GC). Also, thermal stability of one sample from each group was assessed by thermogravimetric analysis (TGA) at a rate of 10°C/min. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (P<0.05). X-tra fil had significantly higher degree of conversion than X-tra base (P=0.001). Specimens cured at 7mm distance had significantly lower degree of conversion compared with those cured at 0 mm distance (P=0.001). The interaction effect of composite type and distance of light curing unit from the surface of samples was statistically significant (P=0.001). Regarding the TGA results, the lowest and the highest percentages of weight loss were detected in X-tra fil cured at 0 mm distance and X-tra base cured at 7mm distance, respectively. X-tra fil composite cured at 0mm distance had the highest degree of conversion and thermal stability, and X-tra base composite cured at 7mm distance had the lowest values.
本研究旨在评估在不同照射距离下固化的大块充填复合树脂的热稳定性和单体洗脱情况。使用两种复合树脂（X-tra fil、X-tra base）制作了40个圆柱形（3×4mm）标本，并在0和7mm的距离下进行固化。在9个标本中，通过单体释放来测定转化率。为此，在复合材料固化后，将它们浸入5 mL 99.9%的甲醇中，并在37°C下储存24小时。然后通过气相色谱法（GC）分析洗脱的单体。此外，以10°C/分钟的速率通过热重分析（TGA）评估每组中一个样品的热稳定性。使用双向方差分析和Tukey事后检验（P<0.05）对数据进行分析。X-tra fil的转化率明显高于X-tra base（P=0.001）。与在0mm距离下固化的标本相比，在7mm距离下固化的标本转化率明显较低（P=0.001）。复合树脂类型和光固化单元与样品表面距离的交互作用具有统计学意义（P=0.001）。关于TGA结果，在0mm距离下固化的X-tra fil中检测到最低的失重百分比，在7mm距离下固化的X-tra base中检测到最高的失重百分比。在0mm距离下固化的X-tra fil复合树脂具有最高的转化率和热稳定性，而在7mm距离下固化的X-tra base复合树脂的值最低。
