Hassan Rogina M, AboELHassan Rewaa G, Azer Amir Shoukry
Teaching Assistant of Fixed Prosthodontics, Conservative Dentistry Department, Alexandria University, Alexandria, Egypt.
Associate Professor of Fixed Prosthodontics, Conservative Dentistry Department, Alexandria University, Alexandria, Egypt.
J Prosthet Dent. 2025 Sep;134(3):758.e1-758.e7. doi: 10.1016/j.prosdent.2025.04.036. Epub 2025 May 22.
Zirconia restorations must achieve micrometer-level accuracy in both marginal and internal fit to ensure an adequate fit with the abutments and to reduce the likelihood of clinical failure. Limited research exists on the fit accuracy of 3-dimensionally (3D) printed zirconia crowns, hindering the confirmation of additive manufacturing's effectiveness in producing zirconia restorations.
The purpose of this in vitro study was to analyze the marginal gap and internal fit of zirconia crowns fabricated through 3D printing compared with those manufactured by traditional milling.
A mandibular typodont tooth was prepared to receive a monolithic zirconia crown, and 24 epoxy resin replicas were obtained and scanned with a dental laboratory scanner. Using a computer-aided design (CAD) software program (Dental CAD 3.0; evoked GmbH), 24 identical zirconia crowns were designed and sent for additive (LithaCon 210 3y; Lithoz GmbH) and subtractive (Nacera Zirconia; Dental Direkt) manufacturing. The triple scan protocol was used to evaluate the marginal gap and internal fit of all zirconia specimens. All scans were obtained using a laboratory optical scanner (Medit T710; Medit Corp). The resulting STL files of each specimen were superimposed and analyzed using a 3D analysis software program (Medit Design v.2.1.4; Medit Corp). Heat maps were generated to represent all deviations. An independent (nonpaired) t test was performed to compare the fit of crowns fabricated with both techniques (α=.05).
The 3D printed zirconia crowns exhibited a significantly higher marginal gap (87.7 ±7.4 µm) compared with the milled crowns (57.5 ±7.0 µm) (P<.05). Similarly, the internal gap was greater in the 3D printed group (107.4 ±4.9 µm) than in the milled group (86.6 ±7.6 µm) (P<.05).
While 3D printed zirconia crowns demonstrated higher marginal and internal gap values compared with the milled crowns, both types were within clinically acceptable limits.
氧化锆修复体必须在边缘和内部贴合度上达到微米级精度，以确保与基牙充分贴合，并降低临床失败的可能性。关于三维（3D）打印氧化锆牙冠贴合精度的研究有限，这阻碍了对增材制造在生产氧化锆修复体方面有效性的确认。
本体外研究的目的是分析通过3D打印制造的氧化锆牙冠与传统铣削制造的氧化锆牙冠的边缘间隙和内部贴合度。
制备一个下颌模型牙以容纳整体式氧化锆牙冠，获取24个环氧树脂复制品并用牙科实验室扫描仪进行扫描。使用计算机辅助设计（CAD）软件程序（Dental CAD 3.0；evoked GmbH）设计24个相同的氧化锆牙冠，并送去进行增材制造（LithaCon 210 3y；Lithoz GmbH）和减材制造（Nacera Zirconia；Dental Direkt）。采用三重扫描方案评估所有氧化锆标本的边缘间隙和内部贴合度。所有扫描均使用实验室光学扫描仪（Medit T710；Medit Corp）进行。使用3D分析软件程序（Medit Design v.2.1.4；Medit Corp）对每个标本生成的STL文件进行叠加和分析。生成热图以表示所有偏差。进行独立（非配对）t检验以比较两种技术制造的牙冠的贴合度（α = 0.05）。
与铣削牙冠（57.5±7.0 µm）相比，3D打印的氧化锆牙冠边缘间隙显著更高（87.7±7.4 µm）（P < 0.05）。同样，3D打印组的内部间隙（107.4±4.9 µm）大于铣削组（86.6±7.6 µm）（P < 0.05）。
虽然与铣削牙冠相比，3D打印的氧化锆牙冠显示出更高的边缘和内部间隙值，但两种类型均在临床可接受范围内。
