Effect Of Diode Laser Irradiation Research Articles

Effect of diode laser irradiation and application of nanoparticle herbal endodontic irrigation solutions on Candida albicans and Enterococcus faecalis bacteria

Effect of diode laser irradiation and application of nanoparticle herbal endodontic irrigation solutions on Candida albicans and Enterococcus faecalis bacteria

Effect of diode laser irradiation in combination with different re-mineralizing agents on enamel micro-hardness (in-vitro study)

Effect of diode laser irradiation in combination with different re-mineralizing agents on enamel micro-hardness (in-vitro study)

The Effect of Low-Level Laser Therapy on the Viability of Human Dental Pulp Stem Cells.

Introduction: This study assessed the effect of low-level laser (LLL) irradiation on the viability of dental pulp stem cells (DPSCs). Methods: In this in vitro experimental study, human DPSCs were purchased from the cell bank of Iranian Genetic Resources and cultured in flasks containing Dulbecco's modified Eagle's medium supplemented with 20% fetal bovine serum (FBS) at 37°C, 5% CO2, and 95% humidity. The cells were stored in semi-confluent form, and the culture medium was refreshed every two days. The cells in the control group were not laser-irradiated, but the cells in the experimental groups were irradiated with 660-nm and 808-nm diode lasers with 4.1 J/cm2 energy density. Cell viability was assessed at baseline and after 24, 48, and 72 hours using the methyl thiazolyl tetrazolium (MTT) assay. The effects of laser irradiation, laser wavelength, and time on the percentage of cell viability were analyzed by two-way ANOVA and Tukey's test. Results: The effects of laser irradiation and its wavelength (P=0.04), time of assessment (P<0.001), and the interaction effect of group and time (P=0.02) on cell viability were significant. Cell viability in 660-nm and 808-nm laser groups at 48 and 72 hours was higher than that of the control group; however, only the difference in cell viability between the 660-nm laser group and the control group at 72 hours was statistically significant (P=0.03). Conclusion: Considering the optimal effect of diode laser irradiation (particularly 660 nm) on the viability of DPSCs, we conclude that it may be suitable for relevant clinical applications.

Thermal Effects of Diode Laser-Irradiation on Titanium Implants in Different Room Temperatures In Vitro.

Objective: The aim of this study was to determine the thermal effects of diode laser irradiation on titanium implants. Methods: An implant (3.5 × 11 mm) was placed into a bovine bone block. A three-wall intrabony defect was created to simulate peri-implant defect. Two thermocouples were secured to the apical and coronal surfaces to measure temperature changes (ΔT) during irradiation. The block was placed in a 37°C water bath and at room temperature (21°C). The defect was irradiated with different diode lasers (fiber 300 μm), while the coronal part of the implant was slightly emerging from the water. While the laser tip was positioned parallel to the implant, the defect was irradiated for 30 sec at 2 W in continuous and pulsed mode. Twenty laser irradiations were performed for each laser wavelength for assessment of ΔT. The linear mixed model was used for comparative statistics. Results: The 980 nm pulsed laser resulted in the highest ΔT (°C) at the coronal (22.45 ± 2.1/14.15 ± 0.13) and apical level (5.4 ± 0.56/3.56 ± 0.35) when this laser was used in both room temperature and water bath conditions, respectively. Similarly, highest ΔT (p < 0.0001) for the 810 nm was 14.3 ± 1.6/12.51 ± 0.63 and apical 3.42 ± 0.52/2.58 ± 0.25, for the 970 nm was 13 ± 1.4/9.93 ± 0.47 and apical 2.89 ± 0.19/2.01 ± 0.19 compared to the 940 nm laser coronally 10.1 ± 0.6/9.19 ± 0.35 and apically 1.67 ± 0.34/1.80 ± 0.17. The coronal part of the implant surpassed the critical threshold of 10°C when irradiated with each of the lasers in the room temperature conditions. Conclusions: Within the limitations of the study, the 940 nm laser seems to control better the risks of overheating during implant irradiation.

Comparison of the Effect of Diode Laser Irradiation and Fluoride Varnish on Salivary Streptococcus mutans Bacterial Colonies Counts: A Randomized Controlled Clinical Trial.

AimThe aim of this study was to assess antibacterial effects of diode laser irradiation and fluoride varnish on Streptococcus (S) mutans bacterial colonies counts in saliva.Materials and MethodsThis was a randomized controlled clinical trial research, in which 36 healthy caries-free schoolchildren aged 7-10 years referred to Birjand University dental school were selected randomly. None of the subjects had used any fluoride products before sampling. They divided into three groups: Group A: Diode laser irradiation, Group B: Fluoride varnish (FV) + diode laser irradiation, and Group C: FV. From each child, the baseline unstimulated saliva samples were obtained, transferred to the mitis salivarius agar (MSA) culture media and assessed for S. mutans colonies counts. The follow-up unstimulated saliva samples were collected one day after the treatments. Then the number of colony-forming units per milliliter were counted and analyzed statistically using Wilcoxon, Mann Whitney U and Kruskal-Wallis tests (p ≤ 0.05).ResultsNo adverse events were reported. Salivary count of S. mutans significantly decreased in all groups. The highest and lowest number of the colonies of S. mutans in treated groups was observed in group I and group II, respectively. S. mutans was not completely eliminated by any of the treatments.ConclusionConsidering the limitations of this study, antimicrobial efficacy of fluoride varnish + diode laser was higher than that of FV or diode laser alone. So this laser in combination with fluoride varnish may be useful in prevention of dental caries and antimicrobial treatment protocols.Clinical trial registryIRCTID: IRCT 201,706 181,7756N20How to cite this articleDarmiani S, Yousefi M, Rad MS. Comparison of the Effect of Diode Laser Irradiation and Fluoride Varnish on Salivary Streptococcus mutans Bacterial Colonies Counts: A Randomized Controlled Clinical Trial. Int J Clin Pediatr Dent 2022;15(S-2):S239-S241.

Evaluating the Effect of Diode Laser Irradiation on Microhardness of Bleached Enamel: An in Vitro Study

Aims: To investigate the effect of in-office dental bleaching techniques on the microhardness of enamel and the influence of post bleaching diode laser irradiation on the surface microhardness of bleached enamel. Materials and methods: Forty bovine teeth were prepared and then randomly allocated into two equal groups (n=20) according to bleaching technique as follows: CB: Conventional in-office bleaching technique and LB: Laser–assisted in-office bleaching technique. Each group was subdivided into two subgroups (n=10) according to laser irradiation setting as follows: C2: Conventionally bleached followed by diode laser irradiation at 2-Watt laser, C4: Conventionally bleached followed by diode laser irradiation at 4-Watt laser, L2: laser –assisted bleached followed by diode laser irradiation at 2-Watt laser and L4: Laser–assisted bleached followed by diode laser irradiation at 4-Watt laser. Vickers microhardness was assessed three times for all the specimens: before bleaching, 24 hours after bleaching and finally 24 hours after post bleaching diode laser irradiation. Paired samples t- test and independent samples t- test were utilized for statistical analysis. Results: Both bleached groups exhibited a significant decrease in micro harness after bleaching with no statistically significant differences between them. Post bleaching diode laser irradiation at 2Watt and 4Watt resulted in significant increase in microhardness with no significant difference was evident between them. Conclusions: Diode laser irradiation on bleached enamel had a positive influence on surface microhardness of enamel and it may represent a promising post bleaching treatment modality.

Influence of diode laser and warm air drying on the shear bond strength of Lithium di-silicate to Dentin. An in-vitro study

Objective: The current study aimed to evaluate the effect of diode laser irradiation (980 nm) and warm air drying(50°C) on shear bond strength between Lithium di-silicate (IPS e.max; Ivoclar) and human dentin using both(Etch &amp; Rinse) adhesive, Adper™ Single Bond 2 (3M ESPE) and (Self-etch) adhesive, Single Bond UniversalTM(3M ESPE) before adhesive polymerization. Material and Methods: 54 sound lower molars were sectioned toobtain flat dentinal surfaces. Specimens were divided into 2 equal groups (n=27): Group 1 (ER) and Group 2(SE) according to bonding approach. Each subgroup was subdivided according to dentin surface treatment into3 equal subgroups (n=9): Control (Co), Diode laser irradiation (L) and Warm air drying (W). All specimenswere adhesively cemented to IPS e.max® CAD discs using RelyX™ Ultimate Clicker™(3M ESPE) resin cement.Samples were then subjected to pre-loading in a thermodynamic manner. All samples were tested for shearbond strength using computer-controlled material testing machine. Data analysis was performed using two-way(ANOVA) (p&lt; 0.05) followed by pair-wise Tukey’s post-hoc tests. Results: In (SE) group, the subgroup (W) hadthe highest shear bond strength values followed by (Co) subgroup and the least was (L) subgroup with statisticallysignificant difference. As for (ER) group, the subgroup (W) had the highest shear bond strength values followedby (Co) subgroup and the least was (L) subgroup with no statistically significant difference. Conclusion: Warmair drying for (SE) bonding approach increased shear bond strength of Lithium di-silicate to human dentin andcan be introduced as a new effective protocol.KEYWORDSAdhesives; Diode laser; IPS e.max; Shear bond strength; Warm air drying.

Effect of Diode Laser irradiation on the Bond Strength of Fiber Posts after Endodontic Retreatment Using Different Sealers.

Purpose: To investigate the effect of diode laser activated irrigation on bond strength between fiber post and radicular dentin after endodontic retreatment using two different sealers. Materials and Methods: Seventy-two extracted human maxillary central incisors were collected, decoronated, endodontically prepared then divided to three groups (n=24) according to sealer type: GP group: gutta-percha without sealer (control group); AD group: AD sealer; and BC group: Bioceramic sealer. Specimens were endodontically retreated after 30 days using the same sealers. 10 mm deep post spaces were prepared in each specimen. Each group was further sub-divided into three subgroups (n=8) according to post space treatment: irrigated with saline (Control), (EDTA) and (laser and EDTA). One tooth from each group was selected for SEM analysis. Posts were cemented, push out tests were performed. Failure modes were analyzed using a digital microscope. Results: With all dentin pretreatment protocols, AD group recorded the highest bond strength mean value followed by GP and BC group respectively, with significant difference (P 0.05). Predominant failure mode was the mixed type as detected by Chi square test. SEM revealed absence of smear layer and opened dentinal tubules after (laser and EDTA) treatment. Conclusions: laser activated irrigation of root dentin significantly improved the bond strength of fiber post after endodontic retreatment with both sealers.

The Effect of Diode Laser Irradiation on Surface Roughness of Bleached Enamel: An in Vitro Study

Aims: To evaluate the influence of post bleaching diode laser irradiation on the surface roughness of bleached enamel. Materials and methods: Forty bovine teeth were prepared and then randomly divided into two equal groups (n=20) according to the in–office bleaching technique as follows: CB: Conventional in–office bleaching technique LB: Laser–assisted in–office bleaching technique. Each group was then subdivided into two subgroups (n=10) according to laser irradiation setting as follows: C2: Conventionally bleached followed by 2-Watt laser irradiation, C4: Conventionally bleached followed by 4-Watt laser irradiation, L2: Laser–assisted bleached followed by 2Watt laser irradiation and L4: Laser–assisted bleached followed by 4Watt laser irradiation. Surface roughness was assessed three times for all the specimens: before bleaching, 24 hours after bleaching and finally 24 hours after post bleaching diode laser irradiation by utilizing profilometer. Paired samples t–test and independent samples t– test was utilized for statistical analysis at p≤0.05. Results: Both bleached groups exhibited a significant increase in the surface roughness of enamel with no statistically significant difference between them. Post bleaching diode laser irradiation at 4Watt resulted in a significant increase in surface roughness of enamel, while 2Watt diode laser irradiation resulted in non–significant increase in surface roughness of enamel. Conclusions: In–office bleaching techniques had a negative impact on enamel in terms of surface roughness. Post bleaching diode laser irradiation at 2Watt power parameter is more preferred than 4Watt power parameter.

Effect of using diode laser on Enterococcus faecalis and its lipoteichoic acid (LTA) in chronic apical periodontitis.

The purpose of this study was to evaluate the effect of diode laser irradiation on Enterococcus faecalis (E. faecalis) and its lipoteichoic acid (LTA). Ninety-six freshly extracted single-rooted teeth were divided into six groups, n = 8 per group. Groups 1, 2, 3, and 4 as laser group (810nm PILOT™ Diode Laser, 400μm fiber diameter, continuous mode, 30s time) with powers at 1.0W, 1.5W, 2.0W, and 2.5W respectively. Group 5 or positive control group (3ml of 1% sodium hypochlorite (NaOCl) irrigation) and group 6 or negative control group (3ml of normal saline (0.9% NaCl) irrigation). Root canal samples were collected before and after receiving laser irradiation and irrigation solution. Cultivable bacteria were determined by counting the colony (CFU/ml). Evaluation of temperature on the external root surface of teeth was done with K type thermocouple using laser at different powers. Enzyme-linked immunosorbant assay (ELISA) was performed to measure the LTA levels and the correlations between E. faecalis count, LTA levels, and rise in temperature were observed using Pearson's correlation test. E. faecalis LTA was subjected to laser irradiation and its structural damage was examined by thin layer chromatography (TLC). Compared with the control groups, all laser groups showed a decreased colony counts and decreased LTA levels with statistically significant difference (p˂0.05). The bactericidal effect and LTA reduction of laser was better at 2.5W power. Laser at 2.5W power had temperature rise of more than 7°C which is beyond the safe thermal threshold level. No statistically significant correlation was found between E. faecalis count, levels of LTA, and rise in external root surface temperature (p˃0.05). TLC results showed a structural damage in the glycolipid moiety of E. faecalis LTA. Diode laser can effectively reduce the E. faecalis count and its LTA levels.

Alterations in Surface Roughness and Chemical Characteristics of Sandblasted and Acid-Etched Titanium Implants after Irradiation with Different Diode Lasers

The purpose of this study was to evaluate the effects of diode laser irradiation with different wavelengths on the surface roughness (Ra) and chemical composition of sandblasted and acid-etched (SLA) titanium implants. Three types of diode lasers with different wavelengths were irradiated on the titanium implants at output powers of 1.0, 2.0, and 3.0 W. The mean Ra values for all spots were measured using a scanning probe microscope. Analysis of variance tests were performed to verify the differences in the Ra between groups according to the type of lasers or power out (α = 0.05). For analyzing chemical composition, atomic and weight percent ratios of titanium, oxygen, and carbon were measured using energy-dispersive spectrometry (EDS). The mean Ra of titanium disc was higher in the 3.0-W output than in 1.0-W or 2.0-W output, but there was no statistically significant difference (p &gt; 0.05). In EDS analysis, it was difficult to find a clear difference in the titanium, oxygen, and carbon element ratios between the laser-irradiated and nonirradiated groups. The irradiation of diode laser with 1.0, 2.0, and 3.0 W output for 15 s decontaminated the SLA titanium surface without damage. However, additional clinical trials will be needed to verify the results of the present study.

Effect of diode laser irradiation and 10% citric acid conditioning on the sealing ability of mineral trioxide aggregate as a retrograde filling material

Aim: The aim was to evaluate the effect of diode laser irradiation and 5% citric acid conditioning on microleakage of mineral trioxide aggregate (MTA) when used as root-end filling material. Materials and Methods: Forty-five human anterior teeth were decoronated and subjected to root canal instrumentation. Three millimeters of apical root portion was resected, and root-end cavities were prepared using ultrasonic tips. The teeth were then randomly divided into three groups (n = 15), In Group 1 – root-end cavity was prepared and treated with citric acid followed by MTA application; in Group 2 – root-end cavity was prepared and treated with diode laser followed by MTA application; and in Group 3 – root-end cavity was prepared and treated with citric acid and laser application followed by MTA application. The specimens were then subjected to glucose leakage analysis at 48 h, 7 days, and 14 days. One-way ANOVA test was used for raw data and Chi-square test for consolidated data to test the significance of difference between the variables. SPSS software version 20 was used for analyzing the data. Results: Group 1 showed significantly more leakage than Group 2 and Group 3 at all time intervals, whereas Group 3 showed the least microleakage at 48 h, 7 days, and 14 days. Conclusion: MTA had a better sealing ability when root-end cavities were conditioned with 5% citric acid followed by diode laser irradiation.

Effects of diode laser irradiation on dental pulps in rats.

To evaluate the effects of different power densities of diode laser on dental pulps in rats. In this study, we used the maxillary central incisors (n=80) of the 40 adult male Wistar albino rats. Rats were randomly divided into four groups according to power densities of diode laser (n=10). Histopathological changes in pulp and height of odontoblast layer were examined . All data were compared statistically using Mann‒Whitney U (Bonferroni) test, p<0.05. G2 displayed slight histolopathologic alterations such as odontoblast cell disorganization and irregularities in cell extensions. Alterations were more prominent in the G3 than G2. Although the lowest odontoblast layer was measured in the G4, the difference in height of odontoblast layer among the groups was not found to be statistically significant. It was concluded that the use of diode laser caused changes at the cellular level in histological examination and may induce the formation of tertiary dentin by influencing the secretory activity of odontoblasts. As long as used in accordance with the recommended procedure, the diode laser can be safely used in dental hard tissues (Tab. 1, Fig. 4, Ref. 15).

Effect of low power laser irradiation on bio-physical properties of wheat seeds

The production of quality food is indispensable and essential to overcome its global shortage. In order to exercise the facile route to acquire massive production, a laser irradiation treatment method was established. We have investigated the effects of diode laser irradiation on wheat seeds germination, its early growth and biochemical parameters. The variation in germination parameters, caused by laser treatment were monitored carefully. A comparison study was accomplished to examine the laser irradiation effects on treated and control seeds. The red laser indicated an enhancement of 25% in germination percentage, 4.68 cm in shoot length, and 0.64 cm in root length while green laser showed 6.25% less germination percentage than the untreated seeds. Further green laser showed 9.67 cm increase in shoot length, 5.39 cm in root length as compared to untreated seeds. It was found that the seeds which were irradiated with green laser showed an amount of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), of 11.9, 10, and 1.53 per mg of protein, respectively as compared to control seeds. Thus, these investigations are promising and suitable for upcoming research on a large scale.

Evaluation and comparison between the bactericidal effect of diode laser irradiation (970 nm) and silver nanoparticles on Enterococcus faecalis bacterial strain (an in vitro study)

Background/AimsToday, the using of diode lasers in dentistry has made a significant progress; it increased the speed of treatment, decreased the time of healing, and showed a bactericidal effect. The thermal effects should be considered in root canal treatment by laser, as the temperature rises to critical levels, causing tissues damage and any thermal change occurs after laser irradiation. The temperature can rise up to 10 °C above the body temperature for less than 2–3 min without damaging the periodontal tissue or burring the tooth structure by using cooling. Antibacterial properties of silver nanoparticles (Ag-NPs) were reducing Gram-positive and Gram-negative bacterial growth, due to a larger surface to volume ratio of nanoparticles. The goal of this study is to evaluate the bactericidal effect of diode laser irradiation (970 nm), the silver nanoparticles in root canals infected by Enterococcus faecalis bacteria, and the thermal change that occurs after laser application.Materials and methodsForty-five extracted single-rooted human maxillary anterior teeth were collected and used as a container for the test. The samples are inoculated by Enterococcus faecalis bacterial strain and randomly divided into three groups: group I (control) (n = 15), group II (Enterococcus faecalis bacteria and silver nanoparticles) (n = 15), and group III (Enterococcus faecalis bacteria and diode laser) (n = 15). The laser group was divided into subgroups according to the time of laser irradiation (20 s, 30 s, and 40 s).ResultsThere was a significant difference between the treated groups, in which the laser group showed a high bactericidal effect than the other groups at the time of radiation 40 s, without damaging the tooth structure or periodontal ligament.ConclusionDiode laser with proper parameters is used as an adjunctive endodontic disinfection modality due to its antibacterial effect with a temperature tolerated by periodontal tissues with safety limit.

Effect of Diode Laser Irradiation of Bonding Agents Before Curing Versus Standard Bonding Protocol on the Shear Bond Strength Between Resin Cement and Dentin

Objective: This study aimed to evaluate the effect of diode laser irradiation (970 nm) of a one-step self-etch adhesive (Clearfil S3Bond/CS3B) and of the bonding agent of a two-step self-etch adhesive (Clearfil Liner Bond F/CLBF) placed on dentin before polymerization on the shear bond strength.Material and methods: Forty sound premolars were sectioned buccally to obtain flat dentin surfaces. The specimens were divided into 4 groups (n=10): Group (OS) – CS3B + polymerization. Group (OS-L) – CS3B + laser + polymerization. Group (TS) – CLBF (bonding agent only) + polymerization. Group (TS-L) – CLBF (bonding agent only) + laser + polymerization. The diode laser was irradiated through an 8 mm bleaching tip for 10 seconds, (0.4 W, 10 Hz, 4 J). All samples were cemented to composite blocks submitted to 4000 thermal cycles. The samples were tested for shear bond strength in a universal testing machine. Data obtained was analyzed using Two-way (ANOVA) (P ? 0.05) and the Bonferroni post-hoc test. Representative samples from each group were analyzed using scanning electron microscopy (SEM). Results: GroupTS-L– (7.43 MPa) displayed statistically significant higher shear bond strength in comparison to that of group TS – (5.13 MPa). No statistically significant difference was found between group OS-L – (6.49 MPa) and group OS – (7.28 MPa). Group TS-L exhibited the highest resin penetration beyond the hybrid layer under SEM. Conclusions: Diode laser irradiation of a bonding agent placed on dentin without prior priming increased the bond strength to dentin and is promising as a new dentin adhesion protocol.

Effects of Laser and Fluoride on the Prevention of Enamel Demineralization: An In Vitro Study.

Introduction: Investigations have demonstrated that fluoride is an essential element in preventive dentistry. However, there are still controversies about the preventive effects of various kinds of laser. The aim of this study was to examine the effect of diode laser irradiation (810 nm) with or without fluoride therapy in the prevention of deciduous enamel demineralization. Methods: Sixty deciduous molar crowns were randomly assigned to 6 groups: C: received no treatment; F: fluoride varnish application; 2L: 2 times diode laser irradiation; 4L: 4 times diode laser irradiation; F2L: 2 times laser irradiation over fluoride varnish; F4L: 4 times laser irradiation over fluoride varnish. Teeth in all groups were subjected to a pH-cycling process to produce artificial caries-like lesions. Results: The analysis of variance (ANOVA) of microhardness values indicated a significant great effect for laser, fluoride, and the interaction of laser- fluoride on reducing the final microhardness value (P<0.001). However, the 2L group was an exception. Despite the 4L group, it did not show a significant prevention of enamel microhardness loss (P=0.125). These 2 groups exhibited different effects in the absence of fluoride (P 2L-4L=0.05) while in the presence of the fluoride varnish, no statistically significant difference was observed between them (P F2L-F4L=0.257). Moreover, no statistically significant difference was observed between the laser-fluoride combination group and the fluoride group (P F2L-F=0.133, P F4L-F=0.926). Conclusion: Our results suggest that fluoride varnish, diode laser, and their combination decrease the loss of the enamel microhardness value and potentially prevent deciduous enamel demineralization. However, the combination of laser and fluoride was not more effective than fluoride.

Effect of Diode Laser-assisted Flap Surgery on Postoperative Healing and Clinical Parameters: A Randomized Controlled Clinical Trial.

Background and Objectives:Lasers have been widely used because of several potential benefits such as antibacterial effect and stimulation of wound healing. In addition, lasers help in hemostasis and delaying epithelial migration which may facilitate the outcome of flap surgery. Hence, this study is aimed to investigate the adjunctive effect of diode laser irradiation on conventional access flap surgery in the treatment of periodontal disease.Materials and Methods:A total of 23 patients requiring periodontal flap surgery in two sextants with probing pocket depth ≥5 mm in at least three teeth post-phase I therapy were selected for a split-mouth study. Flap surgery with adjunctive diode laser irradiation was performed in the test quadrant while conventional access flap surgery was done in the control quadrant. Procedural pain and tissue response of the patients were evaluated at 3, 7, and 14 days postoperatively. Clinical parameters including probing depth, clinical attachment level, plaque index, and gingival index were recorded at baseline, 3 months, and 6 months following treatment.Results:There is no significant difference between the groups with respect to healing response of tissues; however, patients experienced more pain in test sites compared to control sites. Intragroup comparisons showed a statistically significant reduction of all clinical parameters from baseline to 6 months without any significant difference between the groups.Conclusion:Overall within the limitations of the study, diode lasers did not show any significant added benefits over conventional access flap surgery.

Efficacy of diode laser irradiation during dental bleaching in preventing enamel damage caused by bleaching

Evidence on the protecting effect of laser on bleached enamel is scarce and controversial. Therefore, we aimed to test for the first time whether different wavelengths of diode laser (810 and 980 nm) can prevent enamel surface corrosion. We also tested for the first time whether such therapeutic effects of laser are limited to specific "laser-activated" bleaching gels or both conventional and laser-activated gels. In this qualitative experimental study, ten intact human teeth were randomly assigned to five Groups. They were sectioned into twenty buccal/lingual pieces. The groups were: (1) laser-activated gel + 810 nm laser, (2) laser-activated gel + 980 nm laser, (3) conventional gel + 810 nm laser, (4) conventional gel + 980 nm laser, (5) conventional gel only, and (6) laser-activated gel - no irradiation. Buccal sections in each group were subjected to bleaching (according to the stated protocols), and later subjected to field-emission scanning electron microscopy (SEM) and X-ray diffraction (XRD). The lingual pieces were used as "before-treatment" negative controls for XRD. XRD showed an increase in the mineral phase and crystallinity of the enamel in all bleaching groups. This was stronger in the laser-irradiated groups with conventional bleaching agent. SEM showed a complete etched surface in the positive control groups (i.e., bleached using conventional agent). However, all four laser groups had almost intact surfaces. This study showed the positive effect of diode laser irradiation at 810 nm or 980 nm wavelengths on the prevention of bleaching damage, irrespective of the activation mechanism of the bleaching gel in use.

Effect of diode laser irradiation on compressive strength of dental amalgam.

IntroductionOne of the biggest disadvantages of dental amalgam is that gaining its ultimate strength is a slow process. The use of a rapid-setting amalgam with high early compressive strength could be a better option in preventing early fractures in pediatric dentistry. The aim of this study was to determine the effect of diode laser irradiation on compressive strength of dental amalgam.MethodsA case-control study was performed on 180 amalgam samples made at the Tehran Dental Material Research Center in 2014. Fifteen and thirty minute compressive strength of regular setting and fast setting amalgams were measured as control. In case groups, the samples were irradiated by 810nm diode laser with power of 1 and 2 watt and in pulsed and continuous mode, and compressive strength was measured after 15 and 30 minutes. Statistical analysis was performed with SPSS 18 using one and two way ANOVA and Scheffe multiple comparisons test and p<0.05 was considered significant.ResultsNumerous kinds of laser irradiation led to a significant increase in compressive strength compared to regular setting control groups. Fifteen minutes-compressive strength of regular-setting amalgam irradiated by 2 watt laser was significantly more than fast-setting control group (p<0.05).ConclusionIrradiation by 810nm diode laser can significantly increase the compressive strength of dental amalgam especially in the first 15 minutes.