Marginal adaptation and fracture resistance of milled and 3D-printed CAD/CAM hybrid materials of dental crowns with various occlusal thicknesses

Purpose To evaluate the marginal adaptation and fracture resistance of three computeraideddesign/computer-assisted manufacturing hybrid dental materials with different occlusal thicknesses.Methods Ninety single-molar crowns were digitally fabricated using a milled hybrid nanoceramic (Cerasmart, CE), polymer-infiltrated ceramic network (PICN, Vita Enamic, VE), and 3D-printed materials (Varseosmile, VS) with occlusal thicknesses of 0.8, 1, and 1.5 mm (10 specimens/group). Anatomical 3D-printed resin dies (Rigid 10K) were used as supporting materials. A CEREC MCX milling unit and a DLP-based 3D printer, Freeform Pro 2, were utilized to produce the crown samples. Before and After cementation with self-adhesive resin cement, the marginal adaptation, absolutemarginal discrepancy (AMD), and marginal gap (MG) were assessed using micro-CT scanning. Fracture resistance was evaluated using a universal testing machine. The number of fractured crowns and the maximum fracture values (N) were recorded. Datawere statistically analyzed using both one- and two-way ANOVA, followed by Tukey’s honestly significant difference (HSD) test. Results: For all occlusal thicknesses, the VS crowns demonstrated the lowest AMD and MG distances, significantly different from those of the other two milling groups(P<0.05), whereas CE and VE did not differ significantly (P>0.05). All VS crowns were fractured using the lowest loading forces (1480.3±226.1 to 1747.2±108.7 N). No CE and 1 and 1.5 mm VE crowns fractured under a 2000 N maximum load.Conclusions All hybrid-material crowns demonstrated favorable marginal adaptation withina clinically acceptable range, with 3D printing yielding superior results to milling. All materials could withstand normal occlusal force even with a 0.8 mm occlusal thickness.

研究目的：评估三种不同咬合厚度的计算机辅助设计/计算机辅助制造（computer-aided design/computer-aided manufacturing，CAD/CAM）混合牙科材料的边缘适合性与断裂抗力。方法：本研究共数字化制备90颗单磨牙冠修复体，分别采用铣削型混合纳米陶瓷（Cerasmart，CE）、聚合物渗透陶瓷网络（polymer-infiltrated ceramic network，PICN，Vita Enamic，VE）及3D打印材料（Varseosmile，VS），设置咬合厚度为0.8、1、1.5 mm，每组10个样本。采用解剖式3D打印树脂代型（Rigid 10K）作为支撑代型。使用CEREC MCX铣削设备与基于数字光处理（digital light processing，DLP）的3D打印机Freeform Pro 2制备冠修复样本。在采用自粘接树脂水门汀粘接前后，通过显微计算机断层扫描（micro-computed tomography，micro-CT）评估修复体的边缘适合性、绝对边缘间隙（absolute marginal discrepancy，AMD）与边缘间隙（marginal gap，MG）。采用万能试验机评估修复体的断裂抗力，记录断裂冠的数量与最大断裂载荷值（单位：N）。采用单因素方差分析（one-way ANOVA）与双因素方差分析（two-way ANOVA）对数据进行统计学分析，随后采用Tukey真实显著差异（honestly significant difference，HSD）检验进行多重比较。结果：在所有咬合厚度组别中，VS组冠修复体的AMD与MG值均为最低，与其余两组铣削组别相比差异具有统计学意义（P<0.05）；而CE组与VE组之间差异无统计学意义（P>0.05）。所有VS组冠修复体的断裂载荷最低，范围为1480.3±226.1 至 1747.2±108.7 N。在2000 N的最大加载载荷下，CE组及厚度为1 mm、1.5 mm的VE组冠修复体均未发生断裂。结论：所有混合材料冠修复体均表现出临床可接受范围内的优良边缘适合性，其中3D打印技术的修复效果优于铣削技术。即便咬合厚度为0.8 mm，所有受试材料均可承受正常咬合载荷。