Liu Lei, Shen Chenlu, Ye Weijia, Yao Hua, Peng Qiao, Cui Yongdong, Khoo Boo Cheong
School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou, China; State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, China.
The First Affiliated Hospital, Zhejiang University, Hangzhou, China.
Comput Methods Programs Biomed. 2020 Oct;195:105547. doi: 10.1016/j.cmpb.2020.105547. Epub 2020 May 23.
This research aimed to present an improved side-vented needle and explore its availability as well as the corresponding irrigation strategy.
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.
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.
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.
本研究旨在介绍一种改进的侧孔针，并探讨其可用性以及相应的冲洗策略。
采用计算流体动力学（CFD）模型，分别用不同的冲洗针模拟在具有根尖分歧的简化预备圆形根管中的冲洗液流动。针的类型包括平头针、原始侧孔针和改进侧孔针。对比研究了不同的插入深度和入口速度，以及改进侧孔针尖端球部与根管之间的间隙大小。该研究共包括13种方案。测量根管内的速度、压力和剪切应力，以对比不同方案之间的内部流场细节和冲洗效率。
无论使用哪种针，在针插入深度不足的方案中冲洗液置换效果都较差，尽管根尖孔处的压力相对较低。相反，加深针的插入不仅能带来更好的冲洗液置换效果，还能使根尖孔压力更高。与平头针相比，原始侧孔针往往会使根尖孔处压力更低，同时冲洗液置换效果更差。当原始侧孔针被改进侧孔针取代时，进入根尖解剖部分的液体量大幅减少。使用间隙尺寸比和入口速度分别为5.0%和5.50m/s的改进侧孔针的方案可被认为是最佳方案。
改进的侧孔针可以确保可接受的冲洗液置换性能，而不会导致根尖孔处出现高压水平。球部与根管壁之间的间隙对根尖处的压力非常关键。理想的冲洗策略是确保间隙为零。然而，在根管预备的整个过程中，除了最后一步外，要实现这一点有点困难。因此，在非最终冲洗中，有必要采用另一种策略，即尽可能使间隙尺寸比值小，如小于15%，同时确保进入液体的速度较低。
