Objective

The aim of this in vitro study was to analyze the failure of occlusal veneers made of three different restorative CAD/CAM materials under lateral static loading.

Materials and methods

Sixty standardized semi-anatomical occlusal veneers were fabricated on natural lower molars from three different CAD/CAM materials: hybrid ceramic (Vita Enamic), lithium disilicate (IPS e. max CAD) and translucent zirconia (Bruxzir). The specimens were mechanically loaded by a custom-made device attached to a universal testing machine (MTS 858 Mini Bionix II, MN, USA). Static lateral loading was applied on the buccal cusp of the occlusal veneer until failure. Failure loads were recorded, and the types of failure noted for each group. 3D finite element (FE) models simulating the actual test set-up were further employed to evaluate the stresses within the tooth-restoration complex to help interpret the experimental results.

Results

Occlusal veneers made from zirconia recorded a significantly higher mean failure load (843.1 ± 141.5 N) than specimens of the other two materials (p < 0.05). There was no statistically significant difference between the lithium disilicate (493.21 ± 102.24 N) and the hybrid ceramic (499.6 ± 123.1 N) groups (p = 0.863). 74% of the hybrid ceramic and 84% of the lithium disilicate specimens showed veneer fracture, whereas 78% of the zirconia veneers showed debonding. Comparison of the FE-predicted stresses with the different failure strengths corroborated with the experimental results.

Conclusion

Lateral loading caused failure of occlusal veneers at loads significantly lower than those reported for axial loading. Among the materials tested, zirconia veneers showed the highest resistance to failure, with the main failure mode being debonding under lateral loading. The other two material groups failed mainly by veneer fracture at lower loads.

Highlights

- A novel device was used for testing occlusal veneers under lateral static loading. - 3D-FE analysis explained and corroborated the experimental results. - The relationship between vertical and horizontal forces acting on teeth has been described. - The study highlights the harm of excursive contacts on ceramic restorations.

中文翻译：

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侧向静载荷作用下不同修复性CAD / CAM材料的咬合面承载能力

目的

这项体外研究的目的是分析由三种不同的修复性CAD / CAM材料制成的牙合板在侧向静态载荷下的破坏。

材料和方法

用三种不同的CAD / CAM材料在天然下臼齿上制作了60个标准化的半解剖牙合贴面：混合陶瓷（Vita Enamic），二硅酸锂（IPS e。max CAD）和半透明氧化锆（Bruxzir）。通过连接到通用测试机（MTS 858 Mini Bionix II，美国明尼苏达州）的定制设备对样品进行机械加载。将静态侧向载荷施加到咬合板的颊尖上，直到失败。记录失败负荷，并记录每组的失败类型。进一步采用了模拟实际测试设置的3D有限元（FE）模型来评估牙齿修复复合体内的应力，以帮助解释实验结果。

结果

与其他两种材料的样品相比，由氧化锆制成的牙合板的平均破坏载荷（843.1±141.5 N）明显更高（p <0.05）。二硅酸锂（493.21±102.24 N）和杂化陶瓷（499.6±123.1 N）组之间没有统计学上的显着差异（p = 0.863）。74％的混合陶瓷和84％的二硅酸锂样品显示出单板断裂，而78％的氧化锆单板显示出脱胶现象。用不同的破坏强度对有限元预测的应力进行比较，证实了实验结果。

结论

横向载荷导致咬合面的破坏，其载荷明显低于轴向载荷。在测试的材料中，氧化锆贴面显示出最高的抗破坏能力，主要的破坏模式是在横向载荷下脱粘。其他两个材料组主要由于单板在较低载荷下断裂而失败。

强调

-一种新型装置用于在横向静态载荷下测试咬合板。-3D-FE分析说明并证实了实验结果。-已经描述了作用在牙齿上的垂直和水平力之间的关系。-这项研究强调了陶瓷修复体上偏移接触的危害。