- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Characteristics of Bubble Oscillations During Lasera??Activated Irrigation of Root Canals and Method of Improvement
摘要： Background and Objectives: Laser‐activated irrigation of dental root canals is being increasingly used as its efficacy has been shown to be superior compared with conventional techniques. The method is based on laser‐initiated localized fluid evaporation and subsequent rapid bubble expansions and collapses, inducing microfluid flow throughout the entire volume of the cavity. The irrigation efficacy can be further improved if optimally delayed “SWEEPS” double laser pulses are delivered into the canal. This study aims to show that the irrigation efficacy, as measured by the induced pressure within the canal, is related to the double pulse delay, with the maximal pressure generated at an optimal delay. The second aim is to find a method of determining the optimal delay for different cavity dimensions and/or laser parameters. Study Design/Materials and Methods: Experiments were made in transparent models of root canals where Er:YAG laser (λ = 2.94 μm, pulse duration tp = 25 or 50 microseconds, and pulse energies up to EL = 40 mJ) was used with a combination of cylindrical and conical fiber‐tip geometries (diameters 400 and 600 μm). High‐speed photography (60,000 fps) and average pressure measurements inside the canal were used for process characterization. Results: The results show that a pressure amplification of more than 1.5 times occurs if the laser pulse delay approximately coincides with the bubble oscillation time. Correlations between normalized oscillation time and canal diameter for a wide range of laser pulse energies (R2 = 0.96) and between the average pressure within the canal and the bubble oscillation periods (R2 = 0.90) were found. A relationship between the bubble oscillation time and the diameter of the treated cavity was found depending on the bubble oscillation time in an infinite fluid reservoir. Conclusions: The bubble oscillation time within a constrained volume can be determined based on the known oscillation time in infinite space, which offers a fast and simple solution for optimization of the laser parameters. These findings enable determination of optimal conditions for shock wave generation, and improvement of root canal irrigation at the same dose of laser energy input, leading to improved treatment efficacy and safety.
关键词： constrained environments,cavitation bubble,irrigation,Er:YAG laser,root canals,laser‐activated,laser‐induced cavitation
更新于2025-09-23 15:19:57
-
Soft material perforation via double-bubble laser-induced cavitation microjets
摘要： The resulting jet of two interacting laser-induced cavitation bubbles is optimized and studied as a technique for micro-scale targeting of soft materials. High controllability of double-bubble microjets can make such configurations favorable over single bubbles for applications where risk of ablation or thermal damage should be minimized such as in soft biological structures. In this study, double-bubble jets are directed toward an agar gel-based skin phantom to explore the application of micro-scale injection and toward a soft paraffin to quantify the targeting effectiveness of double-bubble over single-bubble jetting. The sharp elongation during the double-bubble process leads to fast, focused jets reaching average magnitudes of Ujet = 87.6 ± 9.9 m/s. When directed to agar, the penetration length and injected volume increase at ～250 μm and 5 nl per subsequent jets. Such values are achieved without the use of fabricated micro-nozzles seen in existing needle-free laser injection systems. In soft paraffin, double-bubble jetting produces the same penetration length as single-bubble jetting, but with ～45% reduction in damage area at a 3× greater target distance. Thus, double-bubble jetting can achieve smaller impact areas and greater target distances, potentially reducing collateral thermal damage and effects of strong shockwave pressures.
关键词： microjets,double-bubble jetting,soft materials,laser-induced cavitation,needle-free injection
更新于2025-09-23 15:19:57
-
Laser induced cavitation: Plasma generation and breakdown shockwave
摘要： Laser induced cavitation is one of the effective techniques to generate controlled cavitation bubbles, both for basic study and for applications in different fields of engineering and medicine. Unfortunately, control of bubble formation and symmetry is hardly achieved due to a series of concurrent causes. In particular, the need to focus the laser beam at the bubble formation spot leads, in general, to a conical region proximal to the light source where conditions are met for plasma breakdown. A finite sized region then exists where the electric field may fluctuate depending on several disturbing agents, leading to possible plasma fragmentation and plasma intensity variation. Such irregularities may induce asymmetry in the successive bubble dynamics, a mostly undesired effect if reproducible conditions are sought for. In the present paper, the structure of the breakdown plasma and the ensuing bubble dynamics are analyzed by means of high speed imaging and intensity measurements of the shockwave system launched at breakdown. It is found that the parameters of the system can be tuned to optimize repeatability and sphericity. In particular, symmetric rebound dynamics is achieved almost deterministically when a pointlike plasma is generated at the breakdown threshold energy. Spherical symmetry is also favored by a large focusing angle combined with a relatively large pulse energy, a process which, however, retains a significant level of stochasticity. Outside these special conditions, the elongated and often fragmented conical plasma shape is found to be correlated with anisotropic and multiple breakdown shockwave emission.
关键词： high speed imaging,Laser induced cavitation,bubble dynamics,breakdown shockwave,plasma generation
更新于2025-09-12 10:27:22