Eradication of mature biofilm from the isthmus region using Er, Cr: YSGG Laser as an activator of 2% chlorhexidine gluconate.

Background: Challenges in the root canal system, such as isthmus, may limit the action of endodontic equipment and irrigation solutions, so using laser agitation is recommended to upgrade the removal of microbial biofilm. The objective of this study is to assess the effectiveness of the laser in photon-induced photoacoustic streaming protocol agitation of 2% chlorohexidine gluconate in removing mature biofilm in complex root canal systems. Material and Methods: Seventy-five mesial roots of the lower first and second molars were separated and cultivated with Enterococcus faecalis bacteria for 30 days (except for the negative control group samples). The samples were divided into four groups (n=15), one group acted as a positive control, other groups were irrigated with 2% chlorohexidine gluconate, some of them were agitated with a passive ultrasonic device, while the other samples were agitated by an Erbium, chromium-doped yttrium, scandium, gallium, and garnet laser in photon-induced photoacoustic streaming protocol. An atomic force microscope was used as a new method to get the results in the isthmus area; A scanning electron microscope was also used in the study to examine the samples before and after the treatment. Statistical Package for Social Sciences software was used to collect and analyze data, and two-way ANOVA was used to compare the means of the test groups. Results: According to the atomic force microscope and scanning electron microscope analyses, Erbium laser and passive ultrasonic activation groups showed higher antimicrobial efficacy than the syringe irrigation group (p<0.05). Conclusions: According to the study's results, the agitation of chlorohexidine gluconate fluid by Erbium laser in photon-induced photoacoustic streaming at 0.75 W offers better Enterococcus faecalis biofilm removal in the difficult-to-reach areas of lower first and second molars. Key words:Atomic force microscope, 2% chlorhexidine gluconate, Enterococcus faecalis, Erbium, chromium-doped yttrium, scandium, gallium, garnet laser, passive ultrasonic.

Debonding of LDSVs utilising Er,Cr:YSGG laser irradiation with fractional technique: an in vitro study.

BACKGROUND: The removal of porcelain laminate veneers with rotary instruments could be accompanied by microfractures because differentiation of the veneer from the dental structure and resin cement is not a highly selective procedure. This can lead to scratches and overheating of the enamel and patient discomfort. Therefore, this in vitro research aimed to examine the effectiveness of the 2790 nm Er,Cr:YSGG laser utilizing a fractional technique to debond lithium disilicate veneer. METHODS: Six groups of 30 extracted permanent bovine mandibular incisors were selected. Twenty-five samples, G1-5, (n = 5) laser-irradiated groups, and the last five samples (C) were considered the control group. The tested groups were irradiated with 3-5 W output power of Er,Cr:YSGG laser for time intervals of 50 s. During irradiation, the temperature in the pulp chamber was monitored using a thermocouple connected to a digital multilogger thermometer inside the sample's pulp chamber. Subsequently, the shear bond strength was measured for all groups. Furthermore, the remaining adhesive index was measured using a stereomicroscope, the area was analysed, and then transformed into scores. Finally, one untreated sample and two samples of the highest power value from laser-treated groups were examined using a scanning electron microscope (SEM) for their surface morphology. RESULTS: All debonding protocols were safe regarding intrapulpal temperature increment. The highest temperature elevation was recorded at 5 W, which increased by 1.7 °C. Considering the shear bond strength measurement, there was a significant reduction after laser irradiation for G1-5 compared with group C. CONCLUSIONS: Er,Cr:YSGG laser with a fractional technique can be used successfully for veneer removal. Besides safe temperature rising, veneers can be reused because there was neither a fractured specimen during the whole study nor major irregularities or cracks shown in SEM pictures analysis for the veneer surfaces; thus, they can be removed quickly, safely, and comfortably using Er,Cr:YSGG. © 2023 Australian Dental Association.

Evaluation of Temperature Elevation During Root Canal Treatment with Dual Wavelength Laser: 2780 nm Er,Cr:YSGG and 940 nm Diode.

OBJECTIVE: The purpose of this study was to evaluate the effects of dual wavelength (2780 nm Er,Cr:YSGG and 940 nm diode) laser with radial firing tip (RFT) on the external root surface and sub-surfaces, in terms of temperature changes during laser-assisted root canal treatment. BACKGROUND DATA: A significant factor that may limit the use of lasers in endodontics is the possible thermal injury to tooth supporting structures. MATERIALS AND METHODS: A total of 50 sound single-rooted extracted teeth were divided randomly into two groups (n = 25). Group A, irradiated with Er,Cr:YSGG laser at 1.06 W, 50 Hz, and 50 µs was a control group, and group B was irradiated with dual wavelength of Er,Cr:YSGG laser with the same settings as group A and a diode laser of 0.51 W at 4 ms and 10 ms pulse duration. K-type thermocouples were used to record temperature changes at the cervical, middle, and apical root thirds, on root surfaces and sub-surfaces, arising from delivery of laser energy through RFT. RESULTS: Temperature elevation in group B was significantly higher in the middle and apical thirds of the prepared samples than in group A (p < 0.0001). Group B presented a mean temperature elevation of 5.07°C on the apical surface region corresponding to a 1.48 mm dentin thickness, whereas a mean temperature increase of 7.72°C was recorded corresponding to dentin thickness of 0.95 mm. CONCLUSIONS: Within the studied parameters, the dual wavelength laser did not result in adverse thermal changes on the external root surface in vitro.

Investigations of radicular dentin permeability and ultrastructural changes after irradiation with Er,Cr:YSGG laser and dual wavelength (2780 and 940 nm) laser.

The aim of this study was to assess the effectiveness of dual wavelength (2780 nm Er,Cr:YSGG, 940 nm diode) laser in elimination of smear layer comparing it with Er,Cr:YSGG laser in terms of radicular dentin permeability and ultrastructural changes of root canal walls. Fifty-one sound single-rooted extracted teeth were instrumented up to size F4 and divided into three groups: group Co, non-irradiated samples; group A, irradiated with Er,Cr:YSGG laser; group B, irradiated with the dual wavelength laser. Afterward, the roots were made externally impermeable, filled with 2% methylene blue dye, divided horizontally into three segments reflecting the cervical, middle, and apical thirds then examined under microscope. Using analytical software, the root section area and dye penetration area were measured, and then, the percentage of net dye penetration area was calculated. Additionally, scanning electron microscope investigations were accomplished. Analysis of variance (ANOVA) showed significant differences between all groups over the three root thirds. Dye permeation in dual wavelength laser group was significantly higher over the whole root length: cervical, middle, and apical compared to Er,Cr:YSGG laser group and non-irradiated samples (p < 0.001). Scanning electron micrographs of dual wavelength irradiated samples showed a distinctive removal of smear layer with preservation of the annular structure of dentinal tubules. Er,Cr:YSGG laser root canal irradiation produced uneven removal of smear layer, in efficient cleanliness especially in the apical third. There was no sign of melting and carbonization. Within the studied parameters, root canal irradiation with dual wavelength laser increased dentin permeability.