Purpose

Virtual surgery system can provide us a realistic and immersive training environment, in which haptic force-feedback gives operators ‘touching feeling.’ Appropriate deformation models of soft and hard tissues are required for the achievement of real-time haptic feedback. To improve accuracy of modeling and haptic feedback simulation for maxillofacial virtual surgery, mechanical characteristics of soft and hard tissues should be explored.

Methods

Craniofacial soft tissues from one male and female cadavers were divided into two layers: skin and muscle. Maxillofacial tissues were divided into frontal, chin, temporalis, masseter regions. Insertion and cutting process were conducted using VMX42 5-axis linkage system and recorded by piezoelectric dynamometer. Maximum stiffness values were analyzed, and insertion curves before puncture were fitted using a polynomial model. Elasticity modulus and hardness of maxillofacial hard tissues were measured and analyzed using Berkovich nanoindentation.

Results

Tissues in different maxillofacial regions, as well as from different layers (skin and muscle), displayed various mechanical performance. Maximum stiffness values and cutting force of soft tissues in male and female had significant difference. The third-order polynomial was demonstrated to fit the insertion curves well before puncture. Furthermore, elasticity modulus and hardness of enamel were significantly greater than that of zygoma, maxilla and mandible.

Conclusion

Mechanical properties of hard tissues are relatively stable, which can be applied in virtual surgery system for physical model construction. Insertion model and cutting force for soft tissues are meaningful and applicable and can be utilized to promote the accuracy of response for haptic feedback sensations.

中文翻译：

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虚拟手术的颌面软，硬组织力学特性的初步研究

目的

虚拟手术系统可以为我们提供逼真的身临其境的训练环境，在该环境中，触觉力反馈可以为操作员带来“触觉”。为了实现实时触觉反馈，需要适当的软组织和硬组织变形模型。为了提高颌面虚拟手术的建模和触觉反馈仿真的准确性，应该探索软组织和硬组织的机械特性。

方法

来自一只雄性和雌性尸体的颅面软组织分为两层：皮肤和肌肉。颌面组织分为额，下巴，颞，咬肌区域。使用VMX42 5轴联动系统进行插入和切割过程，并通过压电测功机记录。分析最大刚度值，并使用多项式模型拟合穿刺前的插入曲线。使用Berkovich纳米压痕技术测量并分析颌面部硬组织的弹性模量和硬度。

结果

不同上颌面区域以及不同层（皮肤和肌肉）的组织显示出各种机械性能。男性和女性软组织的最大刚度值和切削力有显着差异。证明三阶多项式在穿刺之前很适合插入曲线。此外，牙釉质的弹性模量和硬度显着高于骨，上颌骨和下颌骨。

结论

硬组织的机械性能相对稳定，可以在虚拟手术系统中用于物理模型构建。软组织的插入模型和切割力是有意义且适用的，可用于提高触觉反馈感觉的响应准确性。