超声冲洗（PUI）能更好地去除主根管、根管侧支、根管峡部和管壁不规则处的微生物，牙本质碎屑和玷污层，减少冲洗剂渗出根尖孔的量，提高侧支根管的充填率和致密性；但超声冲洗的清洁效果受超声设备、使用方法和根管系统形态的影响。超声工作尖震动致冲洗剂产生微声流作用和空穴作用，所产生的剪切力可清除根管壁上的牙本质碎屑，分解声流区域内的生物物质。要增强微声流作用，可以增大超声频率或强度，或者减小工作尖半径。光滑或K锉形态工作尖超声冲洗清除牙本质碎屑的效果无明显差异，镍钛较不锈钢工作尖能更好地顺应弯曲根管形态。超声冲洗剂选用次氯酸钠溶液可取得良好效果，质量分数1%~5.25%的次氯酸钠溶液超声冲洗效果有逐渐增强的趋势，但无统计学差异，溶液温度和酸碱度的改变对超声冲洗效果无明显影响。间断冲洗可以提高冲洗效果。在一定的范围内，根管锥度越大，弯曲度越小，牙本质碎屑去除的效果越好。%Passive ultrasonic irrigation(PUI) is a favorable technique to remove bacteria, hard tissue debris, and smear layer in the root canals, such as lateral canals, isthmus and irregularities. PUI causes less extrusion and enhances the density of the obturation. Factors such as instruments, techniques, and shape of the root canal systems affect PUI efficiency. The oscillating ultrasonic tips induce powerful acoustic microstreaming and cavitation, which can produce shear stresses along the root canal wall and remove debris and bacteria. Enhancing the frequency and intensity of ultrasonic device or reducing the radius of the ultrasonic tips can enhance acoustic microstreaming. A smooth wire can be as effective as a cutting K-file as the ultrasonic tip. Nickel-titanium tips cause significantly less ledging compared with stainless steel files. Irrigation with sodium hypochlorite is effective. Cleaning efficiency ranging from 1% to 5.25% has a positive correlation with concentration, but does not exhibit statistical difference. Solution pH and temperature have no significant effect on cleaning efficacy. PUI with a pulsation pattern is more effective in removing dentin debris than a continuous oscillation. Bigger taper and smaller curvature can achieve better efficacy of dentine debris removal.
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