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Objectives <p>This in vitro study aimed to evaluate the effects of fabrication methods (CAD/CAM milling, 3D gel deposition), crown thicknesses and their interaction on the fracture resistance of knife-edged monolithic zirconia crowns.</p> Materials and methods <p>Knife-edged monolithic crowns (<i>N</i> = 48) made of 3&#xa0;mol% yttria-stabilized zirconia (3Y-TZP) were fabricated with occlusal and axial thicknesses of 0.5–1.0&#xa0;mm using two techniques: self-glazed zirconia (SGZ) via additive 3D gel deposition and milled zirconia (MZ) via conventional milling. All crowns were subjected to static compressive load-to-fracture tests, followed by comprehensive fractographic analysis. Statistical analyses were conducted using the Shapiro-Wilk test, one-way and two-way ANOVA with post hoc Tukey HSD testing, and multiple linear regression (α = 0.05).</p> Results <p>The mean fracture resistance of knife-edged zirconia crowns ranged from 1277 to 3568&#xa0;N for SGZ and from 933 to 2753&#xa0;N for MZ. SGZ crowns exhibited significantly higher fracture resistance than MZ crowns of the same thickness (<i>P</i> &lt; 0.05). For both SGZ and MZ crowns, increasing occlusal or axial thickness significantly improved fracture resistance (<i>P</i> &lt; 0.05). The effect of occlusal thickness (β-SGZ = 3103.89&#xa0;N/mm, β-MZ = 2559.35&#xa0;N/mm) was more than twice that of axial thickness (β-SGZ = 1478.82&#xa0;N/mm, β-MZ = 1080.49&#xa0;N/mm). All fractures originated from the occlusal surface rather than the knife-edge margin. Fractures in MZ crowns initiated within the glaze layer, whereas SGZ crowns exhibited irregular fracture surfaces lacking distinct fracture origins.</p> Conclusions <p>Both crown thickness and fabrication method, as well as their interaction, are key factors in determining the fracture resistance of knife-edged monolithic zirconia crowns. Additive 3D gel deposition is more favorable for enhancing fracture resistance than conventional milling. Occlusal thickness has a greater impact on fracture resistance than axial thickness.</p> Clinical relevance <p>Compared with crowns fabricated by conventional milling, knife-edged zirconia crowns produced via 3D gel deposition demonstrated enhanced fracture resistance, indicating that this fabrication method is advantageous for minimally invasive restorations. Achieving sufficient occlusal reduction is mandatory during tooth preparation to fulfill the mechanical requirements of the knife-edged crowns.</p>

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Load-bearing capacity of knife-edged monolithic zirconia crowns: effect of thickness and fabrication method

  • 期刊论文

  • 发表日期：

    2026年1月14日

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  • Zhouchuan Cao,
  • Qianqian Ye,
  • Zhi Chen,
  • Zhe Sun,
  • Keying Shi,
  • Jing Zhao,
  • Yuanna Zheng

摘要

Objectives

This in vitro study aimed to evaluate the effects of fabrication methods (CAD/CAM milling, 3D gel deposition), crown thicknesses and their interaction on the fracture resistance of knife-edged monolithic zirconia crowns.

Materials and methods

Knife-edged monolithic crowns (N = 48) made of 3 mol% yttria-stabilized zirconia (3Y-TZP) were fabricated with occlusal and axial thicknesses of 0.5–1.0 mm using two techniques: self-glazed zirconia (SGZ) via additive 3D gel deposition and milled zirconia (MZ) via conventional milling. All crowns were subjected to static compressive load-to-fracture tests, followed by comprehensive fractographic analysis. Statistical analyses were conducted using the Shapiro-Wilk test, one-way and two-way ANOVA with post hoc Tukey HSD testing, and multiple linear regression (α = 0.05).

Results

The mean fracture resistance of knife-edged zirconia crowns ranged from 1277 to 3568 N for SGZ and from 933 to 2753 N for MZ. SGZ crowns exhibited significantly higher fracture resistance than MZ crowns of the same thickness (P < 0.05). For both SGZ and MZ crowns, increasing occlusal or axial thickness significantly improved fracture resistance (P < 0.05). The effect of occlusal thickness (β-SGZ = 3103.89 N/mm, β-MZ = 2559.35 N/mm) was more than twice that of axial thickness (β-SGZ = 1478.82 N/mm, β-MZ = 1080.49 N/mm). All fractures originated from the occlusal surface rather than the knife-edge margin. Fractures in MZ crowns initiated within the glaze layer, whereas SGZ crowns exhibited irregular fracture surfaces lacking distinct fracture origins.

Conclusions

Both crown thickness and fabrication method, as well as their interaction, are key factors in determining the fracture resistance of knife-edged monolithic zirconia crowns. Additive 3D gel deposition is more favorable for enhancing fracture resistance than conventional milling. Occlusal thickness has a greater impact on fracture resistance than axial thickness.

Clinical relevance

Compared with crowns fabricated by conventional milling, knife-edged zirconia crowns produced via 3D gel deposition demonstrated enhanced fracture resistance, indicating that this fabrication method is advantageous for minimally invasive restorations. Achieving sufficient occlusal reduction is mandatory during tooth preparation to fulfill the mechanical requirements of the knife-edged crowns.