Statement of problem

Interim dental prostheses can be fabricated by using subtractive or additive manufacturing technologies. However, the fracture resistance of implant-supported interim crowns fabricated by using vat-polymerization additive manufacturing methods remains unclear.

Purpose

The purpose of this in vitro study was to evaluate the fracture resistance of anterior and posterior screw-retained implant-supported interim crowns fabricated by using subtractive and vat-polymerization direct light processing (DLP) additive manufacturing procedures.

Material and methods

An implant (Zinic Implant RP ∅4.0×10 mm) was placed in a 15×15-mm polymethylmethacrylate block. An implant abutment (ZiaCam, nonrotatory RP) was positioned on each implant. The virtual implant abutment standard tessellation language (STL) file provided by the manufacturer was imported into a software program (exocad v2.2 Valletta) to design 2 anatomic contour crowns, a maxillary right central incisor (anterior group) and a maxillary right premolar (posterior group). Each group was subdivided into 2 subgroups depending on the manufacturing method: milled (milled subgroup) and additive manufacturing (additive manufacturing subgroup). For the milled subgroup, an interim material (Vivodent CAD Multi) and a milling machine were used to fabricate all the specimens (N=40, n=10). For the additive manufacturing subgroup, a polymer interim material (SHERAprint-cb) and a DLP printer (SHERAprint 30) were used to manufacture all the specimens at a 50-μm layer thickness and 45-degree build orientation as per the manufacturer’s instructions. Then, each specimen was cemented to an implant abutment by using composite resin cement (Multilink Hybrid Abutment HO) as per the manufacturer’s instructions. A universal testing machine was used for fracture resistance analysis, and the failure mode was recorded. The Shapiro-Wilk test revealed that data were normally distributed. One-way ANOVA and Tukey multiple comparison were selected (α=.05).

Results

One-way ANOVA revealed significant differences among the groups (P<.05). The anterior milled subgroup obtained a significantly higher fracture resistance mean ±standard deviation value of 988.4 ±54.8 N compared with the anterior additive manufacturing subgroup of 636.5 ±277.1 N (P<.001), and the posterior milled subgroup obtained significantly higher mean ±standard deviation of 423.8 ±68 N than the additive manufacturing subgroup of 321.3 ±128.6 N (P=.048). All groups presented crown fracture without abutment fracture.

Conclusions

Manufacturing procedures and tooth type influenced the fracture resistance of screw-retained implant-supported interim crowns. Milled specimens obtained higher fracture resistance compared with the DLP additive manufacturing groups. The anterior group was higher than the posterior group.

中文翻译：

---

增材制造和铣削种植体支持的临时冠的抗断裂性

问题陈述

可以使用减材或增材制造技术制造临时假牙。然而，使用还原聚合增材制造方法制造的种植体支撑的临时冠的抗断裂性仍不清楚。

目的

这项体外研究的目的是评估使用减材和还原聚合直接光处理 (DLP) 增材制造工艺制造的前牙和后牙螺钉固位种植体支持的临时牙冠的抗折性。

材料与方法

将植入物（Zinic Implant RP ∅4.0×10 mm）置于 15×15-mm 聚甲基丙烯酸甲酯块中。在每个种植体上放置一个种植体基台（ZiaCam，非旋转 RP）。将制造商提供的虚拟种植体基台标准镶嵌语言 (STL) 文件导入软件程序 (exocad v2.2 Valletta) 以设计 2 个解剖学轮廓牙冠，一个上颌右中切牙（前牙组）和一个上颌右前磨牙（后组）。根据制造方法，每组被细分为 2 个子组：铣削（铣削子组）和增材制造（增材制造子组）。对于铣削的亚组，使用中间材料（Vivodent CAD Multi）和铣床来制造所有样本（N=40，n=10）。对于增材制造子组，根据制造商的说明，使用聚合物中间材料 (SHERAprint-cb) 和 DLP 打印机 (SHERAprint 30) 以 50 微米的层厚和 45 度的构建方向制造所有样品。然后，按照制造商的说明，使用复合树脂水泥（Multilink Hybrid Abutment HO）将每个样本粘合到种植体基台上。使用万能试验机进行抗断裂分析，并记录失效模式。Shapiro-Wilk 检验显示数据呈正态分布。选择单向方差分析和 Tukey 多重比较 (α=.05)。根据制造商的说明，使用复合树脂粘固剂（Multilink Hybrid Abutment HO）将每个样本粘固到种植体基台上。使用万能试验机进行抗断裂分析，并记录失效模式。Shapiro-Wilk 检验显示数据呈正态分布。选择单向方差分析和 Tukey 多重比较 (α=.05)。根据制造商的说明，使用复合树脂粘固剂（Multilink Hybrid Abutment HO）将每个样本粘固到种植体基台上。使用万能试验机进行抗断裂分析，并记录失效模式。Shapiro-Wilk 检验显示数据呈正态分布。选择单向方差分析和 Tukey 多重比较 (α=.05)。

结果

单因素方差分析显示各组之间存在显着差异（P <.05）。与前部增材制造亚组 636.5 ±277.1 N ( P <.001)相比，前部铣削亚组获得显着更高的抗断裂平均值±标准差值 988.4 ±54.8 N ( P <.001)，后部铣削亚组获得显着更高的平均值±标准偏差 423.8 ±68 N 比增材制造子组 321.3 ±128.6 N ( P =.048)。各组均出现冠折，无基台折断。

结论

制造程序和牙齿类型影响螺钉固位种植体支持的临时冠的抗折性。与 DLP 增材制造组相比，铣削样品获得了更高的抗断裂性。前组高于后组。