Background and Objective

: This research aimed to present an improved side-vented needle and explore its availability as well as the corresponding irrigation strategy.

Methods

: A CFD model was used to simulate the irrigant flow in a simplified prepared round root canal with an apical delta respectively with different needles for irrigation. The needle types include flat end-tip needle, original side-vented needle, and improved side-vented needle. Different insertion depths and inlet velocities were contrastively studied, as well as the gap size between the bulb at the end tip of the improved side-vented needle and the root canal. The study includes a total of 13 schemes. Velocity, pressure, and shear stress in the root canal were measured to contrast the internal flow-field details and irrigation efficiencies between different schemes.

Results

: Poor irrigation replacement appeared in the schemes without enough needle insertion no matter which kind of needle has been used, though relatively lower pressure emerged at the apical foramen. On the contrary, deepening needle insertion not only brings better irrigant replacement but also higher apical foramen pressure. The original side-vented needle tends to make lower pressure at the apical foramen and simultaneously worse irrigant replacement as compared to the flat end-tip needle. The fluid entering the apical anatomy part deceases a lot as the original side-vented needle was replaced by the improved one. The scheme using the improved side-vented needle with gap size ratio and inlet velocity respectively equaling 5.0% and 5.50m/s can be considered the best one.

Conclusions

: The improved side-vented needle can ensure acceptable irrigant replacement performance without leading to a high-pressure level at the apical foramen. The gap between the bulb and the wall of the root canal is very crucial for the pressure at the apical. The ideal irrigation strategy is ensuring the gap equals zero. However, it is a little hard to realize during the whole procedure of the root canal preparation except the final step. Consequently, another strategy that keeping the value of gap size ratio as small as possible such as less than 15% and simultaneously ensuring lower-velocity coming fluid, is necessary in the non-final irrigation.

中文翻译：

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用CFD方法研究改良的侧静脉针及相应的根管治疗灌溉策略。

背景与目的

：这项研究的目的是提出一种改进的侧通风针，并探讨其实用性以及相应的灌溉策略。

方法

：使用CFD模型模拟简化的准备好的圆形根管中的灌溉水流量，该根管的根尖分别为不同的灌溉针头。针头类型包括平头针，原始的侧面通气针和改进的侧面通气针。对比研究了不同的插入深度和入口速度，以及改进的侧通气针末端尖端的球和根管之间的间隙大小。该研究总共包括13个方案。测量根管内的速度，压力和切应力，以对比内部流场细节和不同方案之间的灌溉效率。

结果

：无论使用哪种类型的针头，该方案在没有足够的针头插入的情况下都出现了较差的灌溉替换，尽管在根尖孔处出现了相对较低的压力。相反，加深针头插入不仅可以带来更好的冲洗液更换效果，还可以带来更高的根尖孔压力。与平端针头相比，原始的侧面通气针往往会降低根尖孔的压力，同时更不利于冲洗液的更换。进入根尖解剖部位的液体会大量减少，因为原来的侧面通气针已被改良的针代替。使用间隙尺寸比和入口速度分别等于5.0％和5.50m / s的改进的侧通气针的方案可以被认为是最佳方案。

结论

：改进的侧通气针可以确保可接受的冲洗液更换性能，而不会导致根尖孔的高压水平。球根与根管壁之间的间隙对于根尖处的压力至关重要。理想的灌溉策略是确保差距等于零。但是，除了最后一步，在根管准备的整个过程中很难实现。因此，在非最终灌溉中，还需要另一种策略，即保持间隙尺寸比的值尽可能小（例如小于15％）并同时确保较低速度的流入流体。