A Comparison of Er:YAG Laser with Photon-Initiated Photoacoustic Streaming, Nd:YAG Laser, and Conventional Irrigation on the Eradication of Root Dentinal Tubule Infection by Enterococcus faecalis Biofilms: A Scanning Electron Microscopy Study

Transient apical peak pressure measurement of Er:YAG laser-activated irrigation in different in vitro tooth models using a high-frequency sensor system

The transient apical pressure side effect is an important safety consideration for Er:YAG laser-activated irrigation (LAI). Therefore, this study aimed to measure the transient apical peak pressure (TAPP) of LAI under different laser settings in various tooth models using a high-frequency sensor system. Tooth models with different pulp chamber structures, apical diameters, and curvatures were prepared using transparent resin and filled with deionised water. The Er:YAG laser fibre was placed 3 mm from the root canal orifice. Irrigation was performed at 10-40 mJ and 20-50 Hz using the super short pulse mode. The TAPP was measured using a 50,000-sample/second pressure sensor connected to the models' apices. The TAPP of LAI was significantly higher than that of other chemical preparation methods. Among all investigated factors, pulp chamber anatomy and apical diameters had the greatest effects and were highly related to the apical peak pressure. Root canal curvature showed no direct correlation with TAPP. The larger the final prepared working width, the greater the TAPP. Furthermore, both pulse energy and frequency had positive correlations with TAPP. In conclusion, tooth anatomy factors and laser parameter settings influenced TAPP during Er:YAG LAI. Therefore, proper settings of laser parameters are important to improve the safety of Er:YAG LAI.

Effects of Physical Stimulation in the Field of Oral Health

Physical stimulation has been widely used in clinical medicine and healthcare due to its noninvasiveness. The main applications of physical stimulation in the oral cavity include laser, ultrasound, magnetic field, and vibration, which have photothermal, cavitation, magnetocaloric, and mechanical effects, respectively. In addition, the above four stimulations with their unique biological effects, which can play a role at the gene, protein, and cell levels, can provide new methods for the treatment and prevention of common oral diseases. These four physical stimulations have been used as important auxiliary treatment methods in the field of orthodontics, implants, periodontal, dental pulp, maxillofacial surgery, and oral mucosa. This paper systematically describes the application of physical stimulation as a therapeutic method in the field of stomatology to provide guidance for clinicians. In addition, some applications of physical stimulation in specific directions are still at the research stage, and the specific mechanism has not been fully elucidated. To encourage further research on the oral applications of physical stimulation, we elaborate the research results and development history of various physical stimuli in the field of oral health.

Photoacoustic removal of Enterococcus faecalis biofilms from titanium surface with an Er:YAG laser using super short pulses

Biofilms that grow on implant surfaces pose a great risk and challenge for the dental implant survival. In this work, we have applied Er:YAG photoacoustic irrigation using super short pulses (Er:YAG-SSP) to remove biofilms from the titanium surfaces in the non-contact mode. Mature Enterococcus faecalis biofilms were treated with saline solution, chlorhexidine, and hydrogen peroxide, or photoacoustically with Er:YAG-SSP for 10 or 60 s. The number of total and viable bacteria as well as biofilm surface coverage was determined prior and after different treatments. Er:YAG-SSP photoacoustic treatment significantly increases the biofilm removal rate compared to saline or chemically treated biofilms. Up to 92% of biofilm-covered surface can be cleaned in non-contact mode during 10 s without the use of abrasives or chemicals. In addition, Er:YAG-SSP photoacoustic irrigation significantly decreases the number of viable bacteria that remained on the titanium surface. Within the limitations of the present in vitro model, the ER:YAG-SSP seems to constitute an efficient therapeutic option for quick debridement and decontamination of titanium implants without using abrasives or chemicals.

The Efficiency of the Er: YAG Laser and PhotonInduced Photoacoustic Streaming (PIPS) as an Activation Method in Endodontic Irrigation: A Literature Review

In the field of endodontics, lasers have been used for a long time for the optimization of Endodontic irrigation in particular. The laser-activated irrigation (LAI) technique is based on the photomechanical effects of the lasers at low settings. They create specific cavitation phenomena and acoustic streaming in intracanal fluids. More recently, a new technique with a Er:YAG laser has been used with sub-ablative energy (20 mJ, 15 Hz) and ultra-short pulses (50 µs). This leads to intracanal cavitation and shockwaves as a result of photoacoustic and photomechanical effects. This phenomenon is called photon-induced photoacoustic streaming (PIPS). PIPS and Laser activated irrigation are described in the literature as a revolutionary and powerful method to activate the irrigant; however, systematic literature on this topic is missing. This review compares the literature on Er:YAG LAI and PIPS on endodontic irrigation with other irrigation methods. An article search was performed on the PubMed database using a series of keywords related to endodontic irrigation, including Er:YAG LAI and PIPS; 59 articles were selected for the review according to the inclusion and exclusion criteria. No in vivo study was found. The Er:YAG LAI and PIPS outperformed other methods in 33 of the 59 articles. There was a great variety in the study designs including bacterial incubation time, laser parameters, irrigation protocols, and irrigating solution used. The evidence suggests that the Er:YAG LAI and PIPS are promising in canal disinfection as well as debris and smear layer removal. However, the large variety in the study methods makes the results less significant. Further studies are needed to better evaluate the efficiency of these techniques, especially in vivo studies.