Former graduate student, Department of Periodontics, Endodontics, and Prosthodontics, School of Dentistry, University of Maryland Baltimore, Baltimore, Md.
Associate Professor, Department of Periodontics, Endodontics, and Prosthodontics, School of Dentistry, University of Maryland Baltimore, Baltimore, Md.
J Prosthet Dent. 2018 May;119(5):777-782. doi: 10.1016/j.prosdent.2017.07.020. Epub 2017 Sep 29.
Radiographs aid in clinically determining crown fit, specifically interproximal margins where tactile and visual methods may be limited. However, investigations of the utility of digital radiographs as a tool for evaluating the marginal openings of ceramic crowns are lacking.
The purpose of this in vitro study was to assess whether marginal adaptation for ceramic crowns and for metal-ceramic crowns with a metal collar can be identified with digital radiographs.
One lithium disilicate crown, 1 fluorapatite crown, and 1 metal-ceramic crown were fabricated for a maxillary premolar. The crowns were attached to a custom-designed device that allowed the marginal discrepancy to be changed. A total of 10 increments were measured starting at 0 to 20 μm and increasing every 20 μm to a maximum opening of 180 to 200 μm. At each increment, 2 radiographs were made of the crowns, using a digital sensor, 1 perpendicular to and 1 at 80 degrees to the long axis of the tooth. To test whether digital radiographs could be used to accurately identify "acceptable" and "unacceptable" margins, 21 dentists were asked to rate the radiographs as "acceptable" or "unacceptable." The chi square test was used to analyze differences between the dentists' evaluations and the actual marginal opening (α=.05). For the purposes of this study, a marginal discrepancy greater than 80 μm was considered "unacceptable."
Of all marginal discrepancies exceeding 80 μm, 78.6% of the metal-ceramic crown radiographs were incorrectly scored as "acceptable" (P<.001). These radiographs were identified as false positives. Lithium disilicate (66.1%) and fluorapatite (45.8%) crowns were more likely to be incorrectly evaluated as "unacceptable" (P<.001) and identified as false negatives.
Using digital radiographs to evaluate marginal adaptation without clinical examination is not by itself an accurate method of evaluating the marginal fit of complete coverage crowns. The marginal fit of the tested metal-ceramic crowns tended to be evaluated incorrectly as acceptable. The marginal fit of the tested ceramic crowns tended to be evaluated incorrectly as unacceptable.
放射线照相术有助于临床确定牙冠拟合度，特别是在触觉和视觉方法可能受到限制的邻间边缘。然而，缺乏关于数字射线照相术作为评估陶瓷牙冠边缘开口的工具的效用的研究。
本体外研究的目的是评估数字射线照相术是否可用于识别陶瓷牙冠和带金属环的金属陶瓷牙冠的边缘适应性。
为上颌前磨牙制作了 1 个锂硅玻璃陶瓷冠、1 个氟磷灰石冠和 1 个金属陶瓷冠。将牙冠固定在一个定制的装置上，该装置允许改变边缘差异。从 0 到 20μm 开始测量了 10 个增量，每隔 20μm 增加到最大开口 180 到 200μm。在每个增量处，使用数字传感器对牙冠拍摄了 2 张射线照片，1 张与牙齿长轴垂直，1 张与牙齿长轴成 80 度角。为了测试数字射线照相术是否可以准确识别“可接受”和“不可接受”的边缘，要求 21 名牙医对射线照片进行“可接受”或“不可接受”的评估。卡方检验用于分析牙医评估与实际边缘开口之间的差异（α=.05）。在本研究中，大于 80μm 的边缘差异被认为是“不可接受的”。
所有超过 80μm 的边缘差异中，78.6%的金属陶瓷牙冠射线照片被错误地评为“可接受的”（P<.001）。这些射线照片被确定为假阳性。锂硅玻璃陶瓷（66.1%）和氟磷灰石（45.8%）牙冠更有可能被错误地评估为“不可接受的”（P<.001），并被确定为假阴性。
在没有临床检查的情况下使用数字射线照相术评估边缘适应性本身并不是评估全冠边缘拟合度的准确方法。测试的金属陶瓷牙冠的边缘拟合度倾向于被错误地评估为可接受。测试的陶瓷牙冠的边缘拟合度倾向于被错误地评估为不可接受。
