Li Y, Lin H, Zhang T J
Department of Dental Materials & Dental Medical Devices Testing Center, Peking University School and Hospital of Stomatology & National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & NMPA Key Laboratory for Dental Materials, Beijing 100081, China.
Beijing Da Xue Xue Bao Yi Xue Ban. 2021 Oct 18;53(5):995-1001. doi: 10.19723/j.issn.1671-167X.2021.05.031.
To compare the effects of different imaging methods on radio-opacity. Digital imaging and traditional film imaging were used to determine the radio-opacity of dental composite resin materials.
Fourteen dental composite resins commonly used in clinic were prepared for disc samples with thickness of 1 mm and diameter of 15 mm respectively. The aluminum step wedge was used as the reference and the disc samples were irradiated with X-rays by the traditional film imaging, phosphor imaging plate and charge-coupled device(CCD) intra-oral X-ray sensor respectively. Exposure was set at 65 kV and 7 mA, with 300 mm focus to film distance and the exposure time was 0.25 s. After developing and fixing the film, the optical density of the image of the sample and that of each step of the aluminum step wedge were measured using the densitometer. The digital image file was exported to grey scale analysis software of Adobe Photoshop to measure the average grey value in the sample image and aluminum step wedge image. The curves were drawn corresponding to the optical density/gray value of each step of the aluminum step wedge and its thickness, and the equivalent thickness of the aluminum plate was calculated according to the optical density/gray value of the actual measured thickness of the sample, so as to evaluate the radio-opacity of dental composite resin material.
For the same sample, the aluminum equivalent measured by traditional film imaging and two other digital imagings had significant differences among the 14 composite resins ( < 0.05), and the aluminum equivalent measured by the two digital imagings were greater than that of the traditional film. Moreover the aluminum equivalent measured by the two digital imagings was also different, and the aluminum equivalent measured by the CCD intra-oral X-ray sensor in most composite resins was larger than that measured by phosphor imaging plate. The same sample was photographed with the same imaging method, and the aluminum equivalent was different after three exposures. The standard deviation of aluminum equivalent measured by phosphor imaging plate was the largest, while that measured by CCD intra-oral X-ray sensor was the smallest. Among the 14 dental composite resin materials, the aluminum equivalent of Tetric N-Ceram and Te-Econom Plus measured by traditional film imaging and phosphor imaging plate was significantly higher than other composite resins.
Based on clinical significance, three kinds of sensors designed to measure the radio-opacity of dental composite resin, the value of aluminum equivalent will change according to different types of sensors. The aluminum equivalent measured by CCD intra-oral X-ray sensor was higher than that measured by phosphor imaging plate, and the aluminum equivalent measured by phosphor imaging plate was higher than that measured by traditional film imaging. Moreover, even though the same sensor was used, the aluminum equivalent measured by multiple exposures was different. The standard deviation of the aluminum equivalent measured by phosphor imaging plate was greater than that measured by traditional film imaging and CCD intra-oral X-ray sensor. The three sensors in this study could be used for evaluating the radio-opacity of dental composite resin materials. But no matter what kind of sensor was used to measure the radio-opacity of dental composite resin, it complied to ISO 4049: 2019 standard, the materials were suitable for clinical use.
比较不同成像方法对射线不透性的影响。采用数字成像和传统胶片成像来测定牙科复合树脂材料的射线不透性。
制备14种临床常用的牙科复合树脂，分别制成厚度为1mm、直径为15mm的圆盘样本。以铝梯楔形块作为参照，分别通过传统胶片成像、磷光成像板和电荷耦合器件（CCD）口腔内X射线传感器对圆盘样本进行X射线照射。曝光条件设定为65kV、7mA，焦片距为300mm，曝光时间为0.25s。胶片显影定影后，使用密度计测量样本图像以及铝梯楔形块各阶梯的光学密度。将数字图像文件导出至Adobe Photoshop灰度分析软件，测量样本图像和铝梯楔形块图像中的平均灰度值。绘制铝梯楔形块各阶梯的光学密度/灰度值与其厚度对应的曲线，并根据样本实际测量厚度的光学密度/灰度值计算铝板的等效厚度，以评估牙科复合树脂材料的射线不透性。
对于同一样本，在14种复合树脂中，传统胶片成像和另外两种数字成像测量得到的铝当量存在显著差异（P<0.05），且两种数字成像测量得到的铝当量均大于传统胶片成像的测量值。此外，两种数字成像测量得到的铝当量也有所不同，在大多数复合树脂中，CCD口腔内X射线传感器测量得到的铝当量大于磷光成像板测量得到的铝当量。同一成像方法对同一样本进行三次曝光后，测量得到的铝当量不同。磷光成像板测量得到的铝当量标准差最大，而CCD口腔内X射线传感器测量得到的铝当量标准差最小。在14种牙科复合树脂材料中，传统胶片成像和磷光成像板测量得到的Tetric N-Ceram和Te-Econom Plus的铝当量显著高于其他复合树脂。
从临床意义来看，三种用于测量牙科复合树脂射线不透性的传感器，铝当量会因传感器类型不同而变化。CCD口腔内X射线传感器测量得到的铝当量高于磷光成像板测量得到的铝当量，磷光成像板测量得到的铝当量高于传统胶片成像测量得到的铝当量。而且，即便使用相同的传感器，多次曝光测量得到的铝当量也不同。磷光成像板测量得到的铝当量标准差大于传统胶片成像和CCD口腔内X射线传感器测量得到的铝当量标准差。本研究中的三种传感器均可用于评估牙科复合树脂材料的射线不透性。但无论使用何种传感器测量牙科复合树脂的射线不透性，均符合ISO 4049:2019标准，这些材料适用于临床。
