Bouschlicher M R, Cobb D S, Boyer D B
University of Iowa, Department of Operative Dentistry, Iowa City 52242-1001, USA.
Oper Dent. 1999 Jan-Feb;24(1):20-5.
The objective of this study was to densitometrically determine the relative radiopacity (aluminum [Al]-equivalent values) of dentin, enamel, and 20 resin composite materials currently used for posterior restorations. Specimens 5 mm in diameter and 2 mm thick were fabricated from 20 materials (n = 7) for a total of 140 specimens. Human molars were longitudinally sectioned 2.0 mm thick to include both enamel and dentin. The optical densities of enamel, dentin, restorative materials, lead, and aluminum step wedge were obtained from radiographic images, using a transmission photodensitometer. The Al equivalent (mm) for each material was calculated from the linear regression equation of the log of normalized optical density and Al mm thickness obtained from the step wedge. A linear regression of the logarithm of normalized optical density and Al mm thickness was plotted (r2 = 0.9953), and the relative radiopacities, expressed as equivalent thickness of Al, were ranked ordinally. All materials tested, with the exception of an unfilled resin adhesive, complied with ISO Standard 4049, being at least as radiopaque as a 2.0 mm thickness of 99.6% pure Al. Four of six flowable composites had radiopacity values that fell between that of dentin and enamel, while two materials were more radiopaque than enamel. The three compomers tested had radiopacities greater than enamel. In addition, all traditional light- and chemical-cure resin composite materials tested were more radiopaque than enamel. All materials tested, with the exception of one adhesive resin, were at least as radiopaque as dentin and complied with ISO Standard 4049. Clinicians should be able to distinguish these restorative materials radiographically from recurrent decay, voids, gaps, or other defects that lead to clinical failure. Utilization of materials ranked more radiopaque than enamel would enable clinicians to distinguish the restorative material from tooth structure.
本研究的目的是通过密度测定法确定牙本质、牙釉质以及目前用于后牙修复的20种树脂复合材料的相对射线不透性（铝[Al]当量值）。用20种材料制作直径5 mm、厚2 mm的样本（n = 7），共140个样本。将人类磨牙纵向切成2.0 mm厚，使其包含牙釉质和牙本质。使用透射式光密度计从射线照片图像中获取牙釉质、牙本质、修复材料、铅和铝阶梯楔形块的光密度。根据从阶梯楔形块获得的归一化光密度的对数与Al mm厚度的线性回归方程，计算每种材料的Al当量（mm）。绘制归一化光密度的对数与Al mm厚度的线性回归图（r2 = 0.9953），并按顺序排列以Al当量厚度表示的相对射线不透性。除未填充的树脂粘合剂外，所有测试材料均符合ISO标准4049，其射线不透性至少与2.0 mm厚的99.6%纯铝相同。六种可流动复合材料中的四种，其射线不透性值介于牙本质和牙釉质之间，而两种材料的射线不透性比牙釉质更高。测试的三种复合体的射线不透性大于牙釉质。此外，所有测试的传统光固化和化学固化树脂复合材料射线不透性均高于牙釉质。除一种粘合树脂外，所有测试材料的射线不透性至少与牙本质相同，并符合ISO标准4049。临床医生应能够通过射线照相将这些修复材料与复发性龋齿、空洞、间隙或其他导致临床失败的缺陷区分开来。使用射线不透性高于牙釉质的材料将使临床医生能够将修复材料与牙齿结构区分开来。
