Root canal therapy is one of the main treatment options for endodontic diseases in which an effective irrigation is key to a successful therapy. In the present paper, the irrigation flow inside an instrumented root canal is numerically investigated, and then the effect of inflow temperature on the irrigation is analyzed based on the computational fluid dynamics results. The magnitude of the shear stress and its corresponding coverage of the irrigation flow on the wall is adopted to characterize the clean efficiency. The axial velocity is used to represent the replacement of local flow field, which stands for the capability to carry away the cleaning residue. Results show that the effective area that the shear stress covers on the root canal wall behind the needle outlet is usually larger than that in front of the outlet, and both the effective coverage of the shear stress and the replacement of the irrigant are improved when the velocity increases. It is convinced that the critical shear stress, namely, the lowest shear stress required to peel off the smear layer on the root canal wall, decreases with the increase in the temperature. Although no apparent variation of the shear stress on the wall can be observed while improving the inflow temperature, the effective surface to be cleaned is improved to some extent because of the decrease in the critical shear stress. Meanwhile, the power consumption is reduced obviously. If the input power remains constant when the temperature increases, both the shear stress on the wall and the replacement are significantly improved besides the decrease in the critical shear stress. This means both the clean efficiency on the wall and the clearing capability (namely replacement) in local flow field are significantly promoted.

中文翻译：

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流入温度对根管冲洗的影响：计算流体动力学研究

根管治疗是牙髓疾病的主要治疗选择之一，其中有效的冲洗是成功治疗的关键。本文对插根管内的灌溉水流进行了数值研究，然后根据计算流体动力学结果分析了入水温度对灌溉水的影响。采用剪应力的大小及其在墙上的灌溉流量的相应覆盖范围来表征清洁效率。轴向速度用于表示局部流场的替换，代表了带走清洁残留物的能力。结果表明，剪应力在针头出口后面的根管壁上所覆盖的有效面积通常大于出口前面的有效面积，当速度增加时，剪切应力的有效覆盖率和冲洗液的替代率都会提高。可以确信，临界剪切应力，即剥离根管壁上的涂抹层所需的最低剪切应力，随着温度的升高而降低。尽管在改善流入温度时在壁上没有观察到剪切应力的明显变化，但是由于临界剪切应力的降低，有效清洁的表面有所改善。同时，功耗明显降低。如果温度升高时输入功率保持恒定，则壁上的剪切应力和替代应力都将得到显着改善，除了临界剪切应力的降低。