Lecturer, Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt.
Professor, Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams university, Cairo, Egypt.
J Prosthet Dent. 2024 Mar;131(3):477.e1-477.e8. doi: 10.1016/j.prosdent.2023.11.032. Epub 2023 Dec 20.
The accuracy of intraoral scanners (IOSs) in recording edentulous jaws has improved recently. However, improvement in accuracy does not necessarily imply the clinical validity of the scans, and limited information is available regarding the manufacture of passively fitting prostheses.
The purpose of this in vitro study was to analyze the passivity of complete arch screw-retained frameworks fabricated using different acquisition techniques.
A 3-dimensional maxillary edentulous model to receive all-on-4 screw-retained frameworks was prototyped. Eighteen polymethylmethacrylate (PMMA) frameworks were fabricated with a 5-axis milling machine and divided into 3 groups according to the acquisition technique (n=6): scanned by using an IOS (CEREC Primescan; Dentsply Sirona), scanned with the aid of an auxiliary device by using the same IOS, and by using a conventional impression and then scanning the stone cast with an extraoral scanner (EOS). The passivity of fit of the frameworks was tested with the 1-screw test, the terminal screw of the framework assembly was tightened on the multiunit abutment (MUA), and the vertical marginal gap (µm) was measured at the other 3 framework-to-abutment interfaces by using a digital microscope at ×40 magnification. A modification to the 1-screw test was analyzed by tightening all screws and then unscrewing all except 1 of the anterior abutments. Data were explored for normality by using the theoretical quantile-quantile (Q-Q) plots and the Shapiro-Wilk test of normality. The Friedman test compared data between the different acquisition techniques; the tightening methods and locations (buccal and palatal) were used as the block variable. The post hoc Dunn test was used when the Friedman test was significant. The Kruksal-Wallis test compared the data from the 2 groups of the tightening methods and the 2 location groups. The aligned rank transformation (ART) ANOVA test was used for the interaction effects among the 3 variables. A multiway ANOVA was applied to the ranked data. (α=.05 for all tests).
Significant differences were found among all groups (P<.001). Regarding the passivity of fit, the mean vertical marginal gap was 50 µm for frameworks fabricated from an intraoral scan with the aid of an auxiliary device, 62 µm for frameworks fabricated by using an IOS, and 140 µm for frameworks fabricated by using an EOS. No significant difference was found among all groups regarding the tightening method (P=.355) or location measured (P=.175).
Digital scanning with the aid of an auxiliary device resulted in the best fit; however, digital approaches with or without the auxiliary device resulted in a more accurate fit with a smaller marginal gap than with the conventional impression.
最近，口内扫描仪（IOS）在记录无牙颌方面的准确性有所提高。然而，准确性的提高并不一定意味着扫描的临床有效性，并且关于被动适配义齿制造的信息有限。
本体外研究的目的是分析使用不同采集技术制作的全弓螺丝固位框架的被动适配性。
制作了一个接收所有 4 颗螺丝固位框架的 3 维上颌无牙颌模型。使用 5 轴铣床制作了 18 个聚甲基丙烯酸甲酯（PMMA）框架，并根据采集技术分为 3 组（n=6）：使用 IOS（登士柏西诺德 CEREC Primescan）扫描、使用相同 IOS 辅助设备扫描和使用传统印模然后扫描外扫描仪（EOS）扫描的石铸模型。使用 1 颗螺丝测试测试框架的适配性，将框架组件的末端螺丝拧紧到多单位基台（MUA）上，然后使用数字显微镜在 ×40 放大倍数下测量其他 3 个框架-基台接口的垂直边缘间隙（µm）。通过拧紧所有螺丝然后松开除前基台外的所有螺丝，分析了 1 颗螺丝测试的改进。通过理论分位数-分位数（Q-Q）图和正态性的 Shapiro-Wilk 检验探索数据的正态性。使用Friedman 检验比较不同采集技术之间的数据；使用紧固方法和位置（颊侧和腭侧）作为块变量。当 Friedman 检验显著时，使用事后 Dunn 检验。Kruksal-Wallis 检验比较了 2 组紧固方法和 2 个位置组的数据。使用对齐秩变换（ART）ANOVA 检验处理 3 个变量之间的交互作用。对等级数据应用多因素方差分析。（所有检验的α值均为 0.05）。
所有组之间均存在显著差异（P<.001）。关于适配性，使用辅助设备进行口内扫描制作的框架的平均垂直边缘间隙为 50 µm，使用 IOS 制作的框架为 62 µm，使用 EOS 制作的框架为 140 µm。在紧固方法（P=.355）或测量位置（P=.175）方面，所有组之间均无显著差异。
使用辅助设备的数字扫描可获得最佳适配性；然而，使用或不使用辅助设备的数字方法可获得更准确的适配性，边缘间隙更小。
