Thermal Effects on Dental Pulp during Laser-Assisted Bleaching Procedures with Diode Lasers in a Clinical Study.

Background In the current cosmetics industry, bleaching is often associated with lasers. However, such treatment also harbors risks. Tooth death is observed at pulpal temperature increases ≥5.6 °C. Therefore, it seems important to investigate the effects of using different lasers. The aim of this study was to determine pulpal temperature increases at different laser parameters during bleaching by modeling a realistic environment and to compare the temperature recording using a thermocouple and thermal camera. The authors assumed that there are laser settings for the lasers used at which the pulpal temperature increases are <5.6 °C and that the temperature recordings with thermocouples and thermal cameras differ only minimally. Methods Human teeth were used, which were extracted for dental reasons. During experiment, teeth were bleached conventionally and by laser activation at 940 nm, 445 nm, and 970 nm. The temperature in the pulp was recorded using thermocouples. In a second setup, longitudinally halved teeth were bleached, while the temperature in the pulp was recorded with a thermocouple and thermal camera. Descriptive statistics were used. The significance level is 0.05. Results In addition to conventional bleaching, temperature increases <5.6 °C were observed for bleaching at 940 nm 1.5 W, at 445 nm 0.3 W, and at 970 nm 0.5 W. For bleaching procedures using 940 nm 7 W, 940 nm 2 W, 445 nm 0.5 W, and 970 nm 1 W, the temperature increase was ≥5.6 °C. Significant differences (p < 0.05) were found in the maximum temperature increases (°C) between all groups. Temperature recordings using a thermocouple and thermal camera differed by about 2.3 °C. The working hypotheses were confirmed. Conclusion With laser bleaching, attention must be paid to the type of laser, its power, and the time in order to avoid excessive overheating of the dental pulp.

Evaluation of tooth color change after a bleaching process with different lasers.

The aim of this in vitro study was to evaluate the efficiency of diode laser-activated bleaching systems for color change of teeth. 75 extracted teeth were studied in five different bleaching protocols. Group 1: diode laser 445 nm, 320 µm fiber, 0.5W, continuous wave mode, dose 53 J/cm2. Group 2: diode laser 970 nm, 320 µm fiber, 1W, continuous wave mode, dose 106.10 J/cm2. Group 3: diode laser 940 nm, bleaching handpiece, 7W, continuous wave mode, dose 105 J/cm2. Group 4: diode laser 940 nm, 300 µm fiber, 2W, continuous wave mode, dose 47.16 J/cm2. Group 5: bleaching process without laser activation. In groups 1, 2 and 5, teeth were bleached with Perfect Bleach Office + and in groups 3 and 4, LaserWhite20 bleaching gel was used. Tooth color was determined immediately after the bleaching process using a spectrophotometer. Color change data on the CIE L * a * b* system was analyzed statistically by the one-way ANOVA and Tukey's HSD test. All bleaching procedures resulted in a change of color. All laser groups (∆E * ab > 3) have statistically larger ∆E * ab values than the control group (∆E * ab = 0.73) (p < 0.05). The diode laser 445 nm has the largest ∆E * ab value (∆E * ab = 4.65) and results in a significantly higher color difference than all other groups. In terms of color score difference in VITA Shades, all laser-activated groups lead to a lightening effect while the control group leads to only a slight lightening effect. The diode laser 445 nm produced the greatest color difference. Laser-activated bleaching is more effective than conventional bleaching without light activation. The diode laser 445 nm performs best in this in vitro study.

Effectiveness of laser-assisted gingival troughing and conventional gingival displacement methods in fixed prosthodontics: A systematic review.

STATEMENT OF PROBLEM: High-level evidence that gingival troughing using dental lasers has better outcomes for the management of gingival tissue surrounding prepared teeth compared with conventional gingival displacement methods is lacking. PURPOSE: The purpose of this systematic review was to review in vivo studies on gingival troughing using dental lasers to compare achieved gingival displacement, influence on periodontal health, and other relevant clinical parameters with different existing gingival displacement methods. MATERIAL AND METHODS: The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and identified studies through January 2022. An electronic search was conducted on the digital databases PubMed/MEDLINE, Web of Science, Scopus, and Embase to identify relevant studies with no limit on publication year. RESULTS: Nine studies were included in this systematic review. Five studies measured achieved horizontal gingival displacement, where lasers show the highest pooled mean of 0.53 mm, among all other displacement methods. Six of the 9 included studies measured periodontal health parameters, with a follow-up time up to 1 year, and other clinically relevant parameters: hemorrhagic control, time needed, ease of use, tooth mobility, pain, and tooth hypersensitivity. CONCLUSIONS: Gingival displacement and bleeding control appeared to be better achieved using lasers. The time needed to achieve gingival displacement was shortest and easiest with lasers. Lasers resulted in either less or comparable gingival recession, lower impact on tooth hypersensitivity, and less pain during the procedure than other methods.

Effect of Er,Cr:YSGG laser with a side-firing tip on decontamination of titanium disc surface: an in vitro and in vivo study.

PURPOSE: To evaluate the effectiveness of an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser with side-firing tip in decontamination of titanium (Ti) disc. METHODS: In the first test series, 29 Ti-discs were contaminated with Staphylococcus aureus and treated as follows: positive control (no treatment); Perioflow; Laser A (0.75 W, 100 Hz), Laser B (1.5 W, 30 Hz); Laser C (no radiation, 60% water); and Laser D (no radiation, 50% water). For bacterial quantification, colony forming units (CFU, vital cells only) and quantitative PCR (qPCR, vital and devital cells) were performed. In a second test series, 92 Ti-discs were used, contaminated with in vivo-grown biofilm and treated as follows: positive control (no treatment); Perioflow; Laser E (1.5 W, 30 Hz), and Laser F (no radiation, 50% water). Considering the different and unknown culture conditions, quantification of bacteria was performed by broad-spectrum bacterial qPCR only. Based on the assumption that all cells of an organism contain an equivalent complement of genetic information, genome equivalent (GE) determination ensured the detection of the different intact and semi-intact genomes, regardless of type of bacterial species and vitality, circumvent the inherent bias of cultures. RESULTS: The GE values were significantly reduced by all interventions in both test series, compared to the positive control group (p < 0.001). In the first test series with S. aureus as model organism, Perioflow yielded a lower GE than the Laser groups A-D (all p < 0.025). The number of CFUs was significantly reduced in the intervention groups compared to the positive control (p < 0.001), except for Laser A (p = 0.157) and Laser D (p = 0.393). In the second test series, none of the pairwise comparisons of the intervention conditions showed a significant difference (Perioflow vs. Laser E: p = 0.732; Perioflow vs. Laser F: p = 0.590; Laser E vs. Laser F: p = 0.379). CONCLUSION: The Er,Cr:YSGG laser with side-firing tip and Perioflow were equally capable of effectively decontaminating a Ti-disc surface. It is assumed that the bacterial reduction was largely due to the mechanical effect of the air and water stream.

Er,Cr:YSGG Laser Surface Modification Effect on Dentin Bonding to Zirconia: An In Vitro Study.

Objective: This study investigated the effect of dentin surface treatment with the erbium, chromium-doped yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser on the bond strength of zirconia to dentin. Background data: Although it is well-known that resin cement (RC) provides adequate bond strength of zirconia restorations to the tooth structure, many clinicians were not convinced in bonding reliability to zirconia materials. So, they preferred cementing their crowns with glass-ionomer cement (GIC). Pretreating the dentin surface is recommended to improve the adhesion of crowns cemented with GIC or RC. Recently, the Er,Cr:YSGG laser has been widely used for a cavity preparation, conditioning the tooth structure. However, there is not enough research on the bond strength of zirconia crowns cemented on a Er,Cr:YSGG laser-treated dentin. Methods: Forty-eight molars were cut horizontally at the crest of curvature. The flat dentin surface of 24 molars was left untreated, whereas the dentin surface of the other half was treated using an Er,Cr:YSGG laser 2.78 µm (4.5 W, 8.18 J/cm2, 90 mJ, 60 µs, 50 Hz, 60% air and 80% water). In addition, 48 plates of zirconia were prepared to be cemented with GIC or RC on the dentin surface. So, the molars were divided into four groups as follows: GIC+untreated dentin; GIC+treated dentin; RC+untreated dentin; and RC+treated dentin. All the specimens were subjected to shear bond strength test. The mode of failure was determined and additional samples were prepared to evaluate the cement-dentin interface using a scanning electron microscope. Data were analyzed with two-way analysis of variance accompanied by univariate analyses. Results: The bond strength of zirconia cemented with GIC or bonded with RC significantly increased on a Er,Cr:YSGG laser-treated dentin surface (p < 0.05). Conclusions: Dentin preconditioning with an Er,Cr:YSGG laser significantly improved the bond strength of zirconia plates to dentin as compared with untreated dentin.

Effect of Low-Level Er: YAG (2940 nm) laser irradiation on the photobiomodulation of mitogen-activated protein kinase cellular signaling pathway of rodent cementoblasts.

BACKGROUNDS: Dental avulsion due to trauma, especially in young patients, is a worldwide problem, requiring tooth replacement. Delayed replantation could cause tooth loss when the cementum is severely damaged. A small number of studies has reported that photobiomodulation (PBM) therapy using Er: YAG laser irradiation activates cellular signaling responses in different cell types, resulting in a variety of favorable biological effects. The aim of this in vitro study was to evaluate the potential biostimulatory effect of low-level Er: YAG laser irradiation on the biological responses of cultured mouse cementoblasts (OCCM-30), including the mitogen-activated protein kinases (MAPKs). METHODS: OCCM-30 cells were exposed to 2940 nm Er: YAG laser irradiation for 15 s at 0.34 W (pulse duration of 100 or 1000 µs, 17 mJ/pulse) at energy densities of 1 or 2 J/cm2. Irradiated and non-irradiated OCCM-30 cells were tested for migration (Scratch assay), proliferation (MTS assay) and functional differentiation (Alizarin Red S assay). Lumican (Lum) and Fibromodulin (Fmod) gene expression, and activation of MAPKs, were assessed by RT-PCR and Western blotting, respectively. RESULTS: Low-level Er: YAG laser irradiation at 2 J/cm2 and pulse duration of 1000 µs resulted in the highest migration rate and proliferation. Moreover, the pulse duration irradiation of 100 µs increased Lum expression. Fmod expression was increased after 1000 µs pulse duration laser stimulation. Low-level Er: YAG laser irradiation increased the mineralization of OCCM-30 cells after 7 days and activated ERK1/2, P38 and JNK signaling. CONCLUSIONS: Low-level Er: YAG laser irradiation induces OCCM-30 cell migration, proliferation and differentiation, and activates the MAPK signaling pathway.

Laterally closed tunnel technique with and without adjunctive photobiomodulation therapy for the management of isolated gingival recession-a randomized controlled assessor-blinded clinical trial.

The objective of this prospective randomized controlled single-center clinical trial was to prove the efficacy of adjunctive photobiomodulation in improving selected outcomes following the use of laterally closed tunnel technique for the management of isolated gingival recession. Nineteen participants (with isolated gingival recession) each treated by laterally closed tunnel technique were randomized to either add on treatment with control (sham laser application) or test group (photobiomodulation with 660 nm diode, 3.5 J/cm2 per point of application). The primary outcome variable was change in recession depth and secondary variables included recession width, width of keratinized gingiva, periodontal biotype, and VAS score for pain assessment and EHS index for early wound healing assessment. Analysis was performed using a linear mixed effects model. There were no significant differences in the gingival recession depth (p = 0.8324) and recession width (p-0.969) at 3-month follow-up. The VAS scores were significantly lower for the test (laterally closed tunnel technique + photobiomodulation) group as compared to control (laterally closed tunnel technique + sham laser) over time (p = < 0.0001) as well as per site (p = 0.0006) The Early Wound Healing Index scores were significantly higher in the test (laterally closed tunnel technique + photobiomodulation) group as compared to control (laterally closed tunnel technique + sham laser) group (p < 0.0001). The adjunctive use of photobiomodulation did not show a better outcome concerning recession depth but appears to provide faster healing of the surgical wounds and better patient comfort. The result needs further evaluation in particular with respect to long-term effect and due to limitation in sample size. Clinical Trial Registry of India: CTRI/2019/11/022012.

Two-year outcomes following the adjunctive use of InGaAsP and Er,Cr:YSGG lasers in nonsurgical periodontal therapy in patients with stages III and IV periodontitis.

OBJECTIVE: To evaluate the clinical outcomes 2 years after the adjunctive use of an InGaAsP diode and Er,Cr:YSGG laser for nonsurgical treatment of severe periodontitis. METHOD AND MATERIALS: Forty-two patients (45.31 ± 9.78 years old, n = 22 females, n = 23 smokers) with stage III or IV grade B periodontitis were randomly treated either with laser (InGaAsP + Er,Cr:YSGG) adjunctive to subgingival debridement (test group, n = 21) or with subgingival debridement alone (control group, n = 21). Subjects in the test group received a second laser treatment in residual sites 2 months after the initial laser therapy. At baseline, and at 12 and 24 months after therapy, periodontal clinical parameters were evaluated. The primary outcome variable was the number of residual deep sites at 12 months (probing depth [PD] ≥ 6 mm). RESULTS: One and two years after nonsurgical periodontal treatment, both groups yielded statistically significant clinical improvements. The adjunctive use of InGaAsP and Er,Cr:YSGG laser to mechanical debridement resulted in statistically significantly higher clinical (PD, clinical attachment level, bleeding on probing, number of sites with PD ≥ 5 mm, PD ≥ 6 mm, PD ≥ 7 mm) improvements (P < .05) compared to subgingival debridement alone both at 12 and 24 months after therapy. CONCLUSION: In patients with stage III or IV grade B periodontitis, InGaAsP and Er,Cr:YSGG used adjunctively to subgingival debridement may additionally improve the clinical outcomes compared to mechanical debridement alone over a period of 24 months.

First Investigation of Dual-Wavelength Lasers (2780 nm Er,Cr:YSGG and 940 nm Diode) on Implants in a Simulating Peri-Implantitis Situation Regarding Temperature Changes in an In Vitro Pocket Model.

Objective: This study aimed to investigate the temperature changes and question the safe laser settings and protocols for laser-assisted peri-implantitis treatment in an in vitro environment. Materials and methods: Three types of implants (Neoss, Dentegris, and Camlog) were implanted in an artificial bone model (n = 15). The model was placed into a 37°C water bath to simulate the in vivo oral condition. Throughout the laser irradiation, K-type thermocouples were used to record the real-time temperature measurements at different anatomically important locations in the artificial bone. Results: In all of the temperature measurements, no temperature rise above the critical safe limit, that is, >47°C, was observed. Conclusions: Within the limitations of this in vitro study, the use of the dual-wavelength protocol [Er,Cr:YSGG (1 and 1.5 W, 25, 50, 75 Hz)] and the 940 nm diode (peak power 2 W, duty cycle 50%) can be considered a safe method in the treatment of peri-implantitis, regarding its thermal safety.

Adjunctive use of InGaAsP and Er,Cr:YSGG lasers in nonsurgical periodontal therapy: a randomized controlled clinical study.

OBJECTIVE: To evaluate clinically and microbiologically the outcomes following the combined application of InGaAsP diode laser and Er,Cr:YSGG laser for nonsurgical treatment of chronic periodontitis (ChP). METHOD AND MATERIALS: Forty-two patients (age 45.31 ± 9.78 years, 22 female, 23 smokers) with ChP were randomly treated with subgingival debridement (SD) by means of ultrasonic and hand instruments (control group, n = 21) or with InGaAsP followed 1 week later by InGaAsP + SD + Er,Cr:YSGG (test group, n = 21). In the test group, a second laser treatment was performed for all residual sites (bleeding sites with probing depth [PD] ≥ 4 mm) 2 months after the first laser therapy. At baseline and 6 months after therapy, periodontal clinical and microbiologic parameters were evaluated. RESULTS: Six months after therapy, statistically significant clinical and microbiologic improvements (PD reduction, clinical attachment level [CAL] gain, quantitative reduction of periopathogens) were observed in both groups compared to baseline. However, the use of InGaAsP followed by SD and the adjunctive use of an Er,Cr:YSGG laser, yielded statistically significantly higher clinical (PD, CAL, bleeding on probing, number of sites with PD ≥ 5 mm, PD ≥ 6 mm, PD ≥ 7 mm) and microbiologic (Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, Prevotella intermedia, Peptostreptococcus micros, Fusobacterium nucleatum) improvements (P < .05) compared to SD alone. CONCLUSIONS: In patients with ChP, the adjunctive use of InGaAsP and Er,Cr:YSGG to SD may additionally improve the clinical and microbiologic parameters obtained with SD alone, thus representing a valuable approach in nonsurgical periodontal therapy.

The Impact of a 940 nm Diode Laser with Radial Firing Tip and Bare End Fiber Tip on Enterococcus faecalis in the Root Canal Wall Dentin of Bovine Teeth: An In Vitro Study.

OBJECTIVE: This in vitro study aimed to compare the bactericidal effect of two different laser delivery systems, a radial firing tip (RFT) and bare end fiber tip (BFT) used with the 940 nm diode laser on Enterococcus faecalis inoculated onto bovine radicular dentin. MATERIALS AND METHODS: A total of 100 bovine dentin slices with a defined thickness of 500 and 1000 µm were prepared. They were assigned into four test groups together with untreated samples served as control for each slice thickness. The slices were inoculated on one side with 1 µL E. faecalis suspension and laser irradiation was performed indirectly on the opposite side with the 940 nm diode laser delivered with a 200 µm RFT and a BFT at 1 and 1.5 W in continuous wave mode for 8 sec per cycle and repeated four times. After irradiation, the remaining bacteria were detached and the produced suspension was diluted and plated onto blood agar plates with 5% sheep blood and incubated overnight at 37°C in a CO2-rich atmosphere. The colony-forming units of E. faecalis were counted and the bacterial reduction was analyzed. RESULTS: The diode laser equipped with RFT fiber design further reduced the number of vital E. faecalis cells significantly compared with BFT design, regardless of the used power and dentin thickness (p < 0.0001). The highest average value of 4 log kills was observed in 500 µm slice thickness irradiated with RFT at 1.5 W. Temperature measurements on the external root surface at 1 mm from the apex did not elicit a harmful temperature elevation in both power settings and fiber designs. CONCLUSIONS: Within the studied parameters, 940 nm diode laser in conjugation with RFT showed a satisfactory bactericidal effect without any thermal side effect to the tooth-supporting tissues.

Creating a Regional Model to Coordinate and Prioritize Access to Permanent Supportive Housing.

Demand for supportive housing outstrips availability in metropolitan regions around the country. Individuals who are homeless with serious mental illnesses, substance abuse, and other debilitating health conditions are often heavy users of publicly financed services and institutions, such as jails, emergency departments, psychiatric and medical hospitals, and sobering and detoxification services. King County, in collaboration with community partners, has developed a regional system for coordinating and prioritizing access to this limited resource based on utilization of publicly financed services/institutions and/or vulnerability. In this paper, the model, key implementation steps, preliminary results, and lessons learned are described.

The effectiveness of the Erbium:Yttrium aluminum garnet PIPS technique in comparison to different chemical solutions in removing the endodontic smear layer-an in vitro profilometric study.

This study evaluated the degree of endodontic smear layer removal using the Er:YAG PIPS technique (2.94 µm) in comparison with different irrigants. Sixty-four single-rooted teeth were endodontically prepared up to size #40 and were divided into 8 groups (a-h) (n = 8). Groups a, b, c, and d were irrigated with (3 % NaOCl + 20 % EDTA), (0.9 % NaCl), (3 % NaOCl), and (20 % EDTA), respectively. Groups e, f, g, and h were treated with (3 % NaOCl + 20 % EDTA + PIPS), (0.9 % NaCl + PIPS), (3 % NaOCl + PIPS), and (20 % EDTA + PIPS), respectively. The settings of the Er:YAG PIPS technique were (0.3 W, 20 mJ, 15 Hz, 50 µs, no water and air). The root canals were examined under a profilometer to evaluate the degree of smear layer removal using Hülsmann scores. The smear layer was present in the coronal, middle, and apical thirds of groups b, c, f, and g. Groups a, d, e, and h exhibited open dentinal tubules in the coronal and middle thirds. However, none of the apical thirds showed open dentinal tubules. No significant difference was observed between the groups treated only with irrigants and those treated with Er:YAG PIPS and the same irrigants (p ≥ 0.0018). The Er:YAG PIPS technique did not show any improved results in removing the smear layer when compared to the irrigants alone. Moreover, the open dentinal tubules in some groups were a result of the chelating action of 20 % EDTA.

Root Surface Temperature Changes During Root Canal Laser Irradiation with Dual Wavelength Laser (940 and 2780 nm): A Preliminary Study.

OBJECTIVE: This study aimed to evaluate the temperature changes on the root surface during root canal irradiation using 2780 nm erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) and 940 nm diode lasers in an alternating sequence. MATERIALS AND METHODS: Eighteen single-rooted human teeth were randomly divided into three groups (n = 6). Teeth were embedded in a resin block, and six thermocouples were introduced at different positions on the tooth surfaces, while immersed in a 37°C thermal bath during laser irradiation. The laser radial firing tip (RFT)2 was operated in helicoidal movements and withdrawn from the root canal in a coronal direction at a speed of 2 mm/sec. Group A was irradiated with the Er,Cr:YSGG laser (1.25 W, 25 mJ, 50 Hz, 50 µs pulse duration, 50% water, and 30% air spray); Group B was irradiated with the Er,Cr:YSGG laser (same settings) and a 940 nm diode (2 W, with 20% duty cycle), and Group C was irradiated with the Er,Cr:YSGG laser (same settings) and a 940 nm diode (2 W, 50% duty cycle). RESULTS: The maximum temperature recorded was in the apical thirds of Groups A-C, resulting in increments of 8.35°C, 7.33°C, and 3.82°C, respectively. All measured temperatures were considerably below the critical value of 10°C. CONCLUSIONS: The alternate use of Er,Cr:YSGG and 940 nm diode lasers can be considered biologically safe to be used in endodontics.

Fracture Forces of Dentin after Surface Treatment with High Speed Drill Compared to Er:YAG and Er,Cr:YSGG Laser Irradiation.

Dental tooth restorative procedures may weaken the structural integrity of the tooth, with the possibility of leading to fracture. In this study we present findings of coronal dentin strength after different techniques of surface modification. The fracture strength of dentin beams after superficial material removal with a fine diamond bur high speed drill hand piece, Er:YAG (2.94 µm, 8 J/cm(2)), and Er,Cr:YSGG (2.78 µm, 7.8 J/cm(2)) laser irradiation slightly above the ablation threshold was measured by a four-point bending apparatus. Untreated dentin beams served as a control. A total of 58 dentin beams were manufactured from sterilized human extracted molars using the coronal part of the available dentin. Mean values of fracture strength were calculated as 82.0 ± 27.3 MPa for the control group (n = 10), 104.5 ± 26.3 MPa for high speed drill treatment (n = 10), 96.1 ± 28.1 MPa for Er,Cr:YSGG laser irradiation (n = 20), and 89.1 ± 36.3 MPa for Er:YAG laser irradiation (n = 18). Independent Student's t-tests showed no significant difference between each two groups (p > 0.05). Within the parameter settings and the limits of the experimental setup used in this study, both lasers systems as well as the high speed drill do not significantly weaken coronal dentin after surface treatment.

Removal of Dental Implants Using the Erbium,Chromium:Yttrium-Scandium-Gallium-Garnet Laser and the Conventional Trephine Bur: An in Vitro Comparative Study.

OBJECTIVE: The purpose of this study was to compare the conventional trephine bur and the Erbium,chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser in removing implants in terms of the volume of removed bone, duration of the procedure, and morphological changes on the bone surface. MATERIALS AND METHODS: Three human mandibles were utilized, and four implants were inserted in each mandible using a drilling handpiece and burs. The implants were divided into two groups (n = 6) in which two implants from each mandible were removed using a trephine bur running at 1200 rounds per minute (rpm) with water irrigation. The remaining implants (n = 6) were removed with Er,Cr:YSGG laser (power 6 W, frequency 20 Hz, pulse duration 50 µs, water 60, air 30). The volume of bone loss was calculated by filling the holes with mercury and measuring its volume. The preparation time was measured with a digital stopwatch and the postoperative bone surfaces were examined under a scanning electron microscope (SEM). RESULTS: The laser group exhibited a smaller amount of bone loss than the trephine bur group, whereas the latter required a shorter time of preparation. SEM revealed empty trabecular spaces with no signs of carbonization and well-defined edges in the laser group, whereas the trephine group displayed a surface covered with a smear layer and microcracks. CONCLUSIONS: The Er,Cr:YSGG laser provides superior results over the trephine bur in terms of bone preservation, thermal damage, and cutting efficiency.

The Bactericidal Effect of 2780 and 940 nm Laser Irradiation on Enterococcus faecalis in Bovine Root Dentin Slices of Different Thicknesses.

OBJECTIVE: The aim of this in vitro study was to investigate the antibacterial effect of the dual wavelength (2780 nm Er,Cr:YSGG and 940 nm diode) laser in elimination of Enterococcus faecalis in comparison with a 2780 nm Er,Cr:YSGG laser alone. BACKGROUND DATA: Various laser wavelengths have been introduced as an adjunct in root canal treatment because of laser's bactericidal effect. MATERIALS AND METHODS: Seventy- five slices of dentin with thicknesses of 300, 500, and 1000 µm (n = 25 each) obtained from caries-free bovine teeth were inoculated with 1 µL of E. faecalis suspension [1.67 × 10(7) colony-forming units (CFU)] and divided randomly into three groups: (A) samples indirectly irradiated with power settings of 1.06 W, 50 Hz, and 50 µs for Er,Cr:YSGG laser; (B) samples indirectly irradiated with Er,Cr:YSGG laser with the same power settings as group A and simultaneously with a 940 nm diode laser of 0.51 W in pulsed mode; and five samples from each thickness that were chosen as an unirradiated control group (Co). After irradiation, the CFU of E. faecalis were counted and the bacterial reduction was analyzed using Kruskal-Wallis nonparametric and post-hoc Dunnett tests. RESULTS: There were statistical differences between groups A and B compared with the control group over all the three dentin slice thicknesses (p < 0.001). However, there was no statistical difference between groups A and B in killing of E. faecalis on 500 µm dentin slices. There were significantly more viable bacteria in group A than in group B in 300 and 1000 µm dentin slices (p < 0.01). CONCLUSIONS: The results of this in vitro study showed that the dual wavelength laser system obtained a significantly higher bactericidal effect on E. faecalis than Er,Cr:YSGG laser, reaching a depth of 1000 µm of dentin.

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.

Intrapulpal temperature changes during root surface irradiation with dual-wavelength laser (2780 and 940 nm): in vitro study.

This work reports that the ablation volume and rate of porcine skin changed significantly with the change of skin water content. Under the same laser irradiation conditions (532 nm Nd:YAG laser, pulse width = 11.5 ns, pulse energy = 1.54 J, beam radius = 0.54 mm), the ablation volume dropped by a factor of 4 as the skin water content decreased from 40 wt. % (native) to 19 wt. % with a change in the ablation rate below and above around 25 wt. %. Based on the ablation characteristics observed by in situ shadowgraph images and the calculated tissue temperatures, it is considered that an explosive rupture by rapid volumetric vaporization of water is responsible for the ablation of the high water content of skin, whereas thermal disintegration of directly irradiated surface layer is responsible for the low water content of skin.