Characteristics of the Irrigant Flow in a Simulated Lateral Canal Under Two Typical Laser-Activated Irrigation Regimens

Zheng Su; Zhibo Li; Ya Shen; Yuhao Bai; Ying Zheng; Chong Pan; Benxiang Hou

doi:10.1002/lsm.23317

Characteristics of the Irrigant Flow in a Simulated Lateral Canal Under Two Typical Laser-Activated Irrigation Regimens

Lasers Surg Med. 2020 Sep 10. doi: 10.1002/lsm.23317. Online ahead of print.

Authors

Zheng Su¹, Zhibo Li², Ya Shen³, Yuhao Bai⁴, Ying Zheng¹, Chong Pan², Benxiang Hou¹

Affiliations

¹ Department of Endodontics, Beijing Stomatological Hospital, Capital Medical University, Beijing, 100050, PR China.
² Institute of Fluid Mechanics, Beihang University, Beijing, 100191, PR China.
³ Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.
⁴ Department of Stomatology, Xuanwu Hospital, Capital Medical University, Beijing, 100053, PR China.

PMID: 32964491
DOI: 10.1002/lsm.23317

Abstract

Background and objectives: Photon-induced photoacoustic streaming (PIPS) and shockwave-enhanced emission photoacoustic streaming (SWEEPS) are two promising laser-activated irrigation (LAI) methods for root canal irrigation. Their performance in driving irrigant flush in a complex root canal system will be evaluated by microscale particle image velocimetry (μPIV) measurement and will be compared with that of ultrasonic-activated irrigation (UAI).

Study design/materials and methods: A μPIV system with 7 μm fluorescent tracer particles was adopted to measure two-dimensional (2D) velocity fields around the junction region, with a size of 1.8 mm × 1.5 mm, between one main canal and one lateral canal in an endodontic training block, which was driven by SWEEPS (Er:YAG laser) operating at 15 Hz and 20 mJ. The flow field driven by PIPS (Er:YAG laser) at the same frequency and energy, as well as by UAI (with non-cutting insert) operating at 40% unit power, was also measured for a direct comparison.

Results: It was found that both SWEEPS and PIPS can activate a so-called "breath mode" during the irrigation. Namely, the induced irrigant flush presented a back-and-forth oscillation along both the main canal and the lateral one. The maximum flow speed in the lateral canal was observed to be up to 10 m/s in the SWEEPS modality, while reduced to around 7 m/s in the PIPS modality. The penetration length in the lateral canal in both modalities was estimated to be larger than 1 mm. In comparison, the flow field induced by UAI was characterized as irregular vortical structures, the maximum flow speed in the lateral canal was 0.15 m/s and significantly lower than LAI (P < 0.01), and the penetration length was less than 300 μm and lower than LAI (P < 0.05).

Conclusion: Compared to UAI, PIPS, and SWEEPS are more capable of delivering the irrigant deeper into the lateral canal. Furthermore, the back-and-forth flush in the breath mode is ideal for removing debris during irrigation. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Keywords: lateral canal; microscale particle image velocimetry; photon‐induced photoacoustic streaming; shockwave‐enhanced emission photoacoustic streaming; ultrasonic‐activated irrigation.

Abstract

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