Effect of Low-Level Diode Laser and Red Light-Emitting Diode on Survival and Osteogenic/Odontogenic Differentiation of Human Dental Pulp Stem Cells.

Background: This investigation set out to compare the impacts of low-level diode laser (LLDL) and red light-emitting diode (LED) on the survival of human dental pulp stem cells (hDPSCs) and osteogenic/odontogenic differentiation. Methods and materials: In this ex vivo experimental study, the experimental groups underwent the irradiation of LLDL (4 J/cm2 energy density) and red LED in the osteogenic medium. Survival of hDPSCs was assessed after 24 and 48 h (n = 9) using the methyl thiazolyl tetrazolium (MTT) assay. The assessment of osteogenic/odontogenic differentiation was conducted using alizarin red staining (ARS; three repetitions). The investigation of osteogenic and odontogenic gene expression was performed at two time points, specifically 24 and 48 h (n = 12). This analysis was performed utilizing real-time reverse-transcription polymerase chain reaction (RT-PCR). The groups were compared at each time point using SPSS version 24. To analyze the data, the Mann-Whitney U test, analysis of variance, Tukey's test, and t-test were utilized. Results: The MTT assay showed that LLDL significantly decreased the survival of hDPSCs after 48 h, compared with other groups (p < 0.05). The qualitative results of ARS revealed that LLDL and red LED increased the osteogenic differentiation of hDPSCs. LLDL and red LED both upregulated the expression of osteogenic/odontogenic genes, including bone sialoprotein (BSP), alkaline phosphatase (ALP), dentin matrix protein 1 (DMP1), and dentin sialophosphoprotein (DSPP), in hDPSCs. The LLDL group exhibited a higher level of gene upregulation (p < 0.0001). Conclusions: The cell survival of hDPSCs was reduced, despite an increase in osteogenic/odontogenic activity. Clinical relevance: Introduction of noninvasive methods in regenerative endodontic treatments.

Effect of magnesium oxide nanoparticles and LED irradiation on the viability and differentiation of human stem cells of the apical papilla.

PURPOSE: Currently, regenerative endodontic treatments are gaining more and more attention, and stem cells play a significant role in these treatments. In order to enhance stem cell proliferation and differentiation, a variety of methods and materials have been used. The purpose of this study was to determine the effects of magnesium oxide nanoparticles and LED irradiation on the survival and differentiation of human stem cells from apical papilla. METHODS: The MTT test was used to measure the cell survival of SCAPs that had been exposed to different concentrations of magnesium oxide nanoparticles after 24 and 48 h, and the concentration with the highest cell survival rate was picked for further studies. The cells were classified into four distinct groups based on their treatment: (1) control, which received no exposure, (2) exposure to magnesium oxide nanoparticles, (3) exposure to light emitting diode (LED) irradiation (635 nm, 200 mW/cm2) for 30 s, (4) exposure simultaneously with magnesium oxide nanoparticles and LED irradiation. A green approach was employed to synthesize magnesium oxide nanoparticles. Quantitative real time PCR was used to measure the gene expression of osteo/odontogenic markers such as BSP, DSPP, ALP and DMP1 in all four groups after treatment, and Alizarin red S staining (ARS) was used to determine the osteogenic differentiation of SCAPs by demonstrating the Matrix mineralization. RESULTS: The highest viability of SCAPs was observed after 24 h in concentration 1 and 10 µg/mL and after 48 h in concentration 1 µg/mL, which were not significantly different from the control group. In both times, the survival of SCAPs decreased with increasing concentration of magnesium oxide nanoparticles (MgONPs). According to the results of Real-time PCR, after 24 and 48 h, the highest differentiation of BSP, DMP1, ALP and DSPP genes was observed in the LED + MgONPs group, followed by MgONPs and then LED, and in all 3 experimental groups, it was significantly higher than control group (P < 0.05). Also, after 24 and 48 h, the density of ARS increased in all groups compared to the control group, and the highest density was observed in the MgONPs + LED and MgONPs groups. CONCLUSION: This research concluded that exposure to SCAPs, MgONPs, and LED irradiation has a significant effect on enhancing gene expression of odontogenic/osteogenic markers and increasing matrix mineralization.

Synthesis and characterization of hydroxyapatite nanoparticles and their effects on remineralization of demineralized enamel in the presence of Er,Cr: YSGG laser irradiation.

BACKGROUND: This study aims to synthesize and characterize hydroxyapatite nanoparticles (nano-HA) and evaluate their effects on the remineralization of demineralized enamel in the presence to Er,CR: YSGG laser irradiation. MATERIALS AND METHODS: Enamel specimens from 44 human molars were divided into four groups: control, demineralized enamel, demineralized enamel treated with nano-HA, and demineralized enamel treated with nano-HA followed by Er,Cr:YSGG laser irradiation (0.5, 20 Hz, 60 µs, 20 s). Vickers microhardness test was used to evaluate the enamel surface hardness. The morphology and chemistry of enamel surfaces were assessed using scanning electron microscopy (SEM) and Raman spectroscopy, respectively. RESULT: The result of this study showed that the application of Er,CR: YSGG laser irradiation to demineralized enamel treated with nano-HA had the highest impact on its microhardness. CONCLUSION: ER,CR: YSGG laser irradiation promotes enamel remineralization after treatment with nano HA.

Shear bond strength of orthodontic brackets to specimens fabricated from temporary restorative materials by 3D-printing, CAD/CAM technology, and the conventional technique after surface treatment by sandblasting and laser.

OBJECTIVES: This study assessed the shear bond strength (SBS) of stainless steel (SS) orthodontic brackets to specimens fabricated from polymethyl methacrylate (PMMA) temporary restorative material by 3D-printing, computer-aided design/computer-aided manufacturing (CAD/CAM) technology, and the conventional technique, after surface treatment by sandblasting and laser. MATERIAL AND METHODS: In this in vitro study, 60 disc-shaped specimens with 8mm diameter and 1mm height were fabricated from PMMA temporary restorative material by 3D-printing, CAD/CAM, and the conventional technique. In each group (n=20), half of the specimens were sandblasted while the other half underwent Er,Cr:YSGG laser irradiation. Brackets were bonded to the specimens and underwent thermocycling followed by SBS testing. Data were analysed by one-way ANOVA, independent t-test, and LSD test (alpha=0.05). RESULTS: A significant difference existed among the three fabrication methods in SBS in both laser (P<0.001) and sandblasting (P<0.001) surface treatment groups. In laser group, the mean SBS of CAD/CAM (P=0.000) and conventional (P=0.000) groups was significantly lower than that of 3D-printing group. In sandblasting group, the SBS of CAD/CAM group was significantly lower than 3D-printing (P=0.000) and conventional (P=0.000) groups. The mean SBS of laser-treated specimens was significantly higher than sandblasted specimens in 3D-printing group (P=0.000), and significantly lower than sandblasted specimens in the conventional group (P=0.000). A significantly higher SBS was obtained by laser treatment compared with sandblasting irrespective of the fabrication method (P=0.000). CONCLUSION: The highest SBS of SS orthodontic brackets to temporary restorative material was recorded for 3D-printed specimens treated by Er,Cr:YSGG laser irradiation.

Effect of copper oxide nanoparticles and light-emitting diode irradiation on the cell viability and osteogenic/odontogenic differentiation of human stem cells from the apical papilla.

OBJECTIVES: This experimental study aimed to assess the effect of copper oxide nanoparticles (CuONPs) and light-emitting diode (LED) irradiation on the cell viability and osteogenic/odontogenic differentiation of human SCAPs. METHODS: After the culture of SCAPs, the effects of different concentrations of CuONPs on cell viability were evaluated by the methyl thiazolyl tetrazolium (MTT) assay after 24 and 48 h, and the optimal concentration was determined (n = 12). SCAPs were then divided into four groups based on the type of treatment: (I) no-treatment control group, (II) exposure to CuONPs, (III) LED irradiation (635 nm, 200 mW/cm2) for 30 s, and (IV) exposure to CuONPs combined with LED irradiation. CuONPs were synthesized by a green technique, which was based on reduction and simultaneous stability of copper ions by using the pomegranate peel extract. After treatments, the expression of osteogenic/odontogenic markers including dentin sialophosphoprotein (DSPP), bone sialoprotein (BSP), alkaline phosphatase (ALP), and dentin matrix acidic phosphoprotein 1 (DMP1) was evaluated in all four groups using quantitative real-time polymerase chain reaction (PCR) (n = 16). Also, osteogenic differentiation of SCAPs was evaluated qualitatively by alizarin red staining (ARS) to assess the matrix mineralization (n = 4). SPSS version 18 was used for data evaluation. The Kruskal-Wallis and Mann-Whitney tests were used to compare the groups. RESULTS: Exposure to 1 µg/mL CuONPs resulted in maximum viability of SCAPs. Concentrations of CuONPs over 10 µg/mL significantly decreased the viability of SCAPs. Real-time PCR showed that the expression of DMP1, BSP, ALP, and DSPP in CuONPs + LED and LED groups was significantly higher than that in CuONPs and control groups at both 24 and 48 h (P < 0.05). The density of ARS increased in all experimental groups after 24 h, and in CuONPs + LED and CuONPs groups after 48 h, compared to the control group. CONCLUSION: Addition of CuONPs and LED irradiation of SCAPs in the culture medium significantly enhanced their osteogenic/odontogenic differentiation.

Effect of diode low level laser and red light emitting diode irradiation on cell proliferation and osteogenic/odontogenic differentiation of stem cells from the apical papilla.

BACKGROUND: This experimental study aimed to assess the effect of irradiation of red light-emitting diode (LED) and Diode low-level laser (LLL) on osteogenic/odontogenic differentiation of stem cells from the apical papilla (SCAPs). MATERIALS AND METHODS: SCAPs were isolated from the human tooth root. The experimental groups were subjected to 4 J/cm2 diode low level laser and red LED irradiation in osteogenic medium. The control group did not receive any irradiation. Cell viability/proliferation of SCAPs was assessed by the methyl thiazolyl tetrazolium (MTT) assay on days 1 and 2 (n = 9). Osteogenic differentiation was evaluated by alizarin red staining (ARS) (n = 3), and expression of osteogenic genes by real-time polymerase chain reaction (RT-PCR) (n = 12) on days 1 and 2. SPSS version 18 was used for data evaluation. The Kruskal-Wallis and Mann-Whitney tests were used to compare the groups at each time point. RESULTS: The MTT assay showed no significant difference in cell viability/proliferation of SCAPs in the low level laser, red LED, and control groups at 24 or 48 h (P < 0.001). The ARS assessment showed that low level laser and red LED irradiation enhanced osteogenic differentiation of SCAPs. low level laser and red LED irradiation both induced over-expression of osteogenic/dentinogenic genes including alkaline phosphatase (ALP), dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP-1), and bone sialoprotein (BSP) in SCAPs. Up-regulation of genes was significantly greater in low level laser irradiation group than red LED group (P < 0.001). CONCLUSION: Diode low level laser irradiation with 4 J/cm2 energy density and red LED irradiation enhanced osteogenic differentiation of SCAPs without adversely affecting cell viability.

Effect of sodium fluoride varnish, Gluma, and Er,Cr:YSGG laser in dentin hypersensitivity treatment: a 6-month clinical trial.

Dentinal hypersensitivity (DH) is a common clinical condition usually associated with exposed dentinal surfaces. The aim of this study was to study the effect of sodium fluoride varnish, Gluma, and Er,Cr:YSGG laser, in the dentin hypersensitivity treatment. One hundred sixty-five teeth with dentin hypersensitivity in 55 patients were involved in this study. Teeth are divided into five groups based on the received treatment (n = 33): G group: Gluma; F group: sodium fluoride varnish (5%); L group: Er,Cr:YSGG laser (wavelength 2780 nm, frequency 20 Hz, power 0.25 W, energy density 44.3 J/cm2, and pulse width of 150 µs at distance of 1 mm for 30 s) which was followed by Er,Cr:YSGG laser; GL group: Gluma + laser; VL group: both sodium fluoride varnish and Gluma, which are common treatments for hypersensitivity, were selected as control groups. The treatment was performed in one session, and the sensitivity to air spray conditioning was recorded after the treatment, at 15 min, 1 week, 1 month, and 6 months as the VAS. Statistical analysis was performed using SPSS Ver. 21 software. One-way ANOVA was used to compare the VAS between all treatment groups at each time-point. One-way repeated measurements ANOVA (RM-ANOVA) and two-way-repeated measurements ANOVA (RM-ANOVA) were used to compare the hypersensitivity of each group and sensitivity of all treatment groups, respectively. Tukey post hoc test was used to compare the groups pairwise. The hypersensitivity between different groups at before and 15 min after the treatment was not significantly different (P = 0.063). The hypersensitivity of all studied groups was decreased after the treatment. The Er,Cr:YSGG laser, alone or in combination with Gluma, in 1 week, 1 month, and 6 month follow-ups, had significantly reduced the hypersensitivity instead of sodium fluoride varnish. All treatments significantly reduced the dentin hypersensitivity up to 6 months. Er,Cr:YSGG laser alone or in combination with Gluma was more effective than sodium fluoride varnish; however, it was not significantly different from other treatments. In a 6-month follow-up of dentine hypersensitivity treatment, Gluma had a significantly higher effect than sodium fluoride. Trial registration: IRCT20190422043343N1. Registered 19 July 2019.

Comparative effects of Er:YAG laser, and EDTA, MTAD, and QMix irrigants on adhesion of stem cells from the apical papilla to dentin: A scanning electron microscopic study.

Background: Dentin conditioning can affect the adhesion of stem cells in endodontic regenerative treatments. This study aimed to assess the effects of the most commonly used endodontic irrigants, namely, ethylenediaminetetraacetic acid (EDTA), MTAD, and QMix in comparison with Er:YAG laser (as a novel modality for root canal disinfection) on the adhesion of stem cells from the apical papilla (SCAPs) to dentin. Material and Methods: Forty dentin specimens were prepared and subjected to different treatments in 5 groups (n=8) of control, irrigation with EDTA for 1 minute, irrigation with MTAD for 5 minutes, irrigation with QMix for 5 minutes, and Er:YAG laser irradiation. SCAPs were isolated from third molar tooth buds that two-thirds of their roots had formed. The cells were cultured on dentin specimens for 3 days and were counted using scanning electron microscopy (SEM). Results: MTAD resulted in significantly lower adhesion of cells to dentin compared with other groups (P<0.05). All other modalities induced cell adhesion with no significant difference with each other (P>0.05). Conclusions: Despite many favorable properties, MTAD cannot serve as an optimal irrigant in endodontic regenerative procedures since it inhibits the adhesion of SCAPs to dentin and impairs an important step in tissue engineering. Key words:Endodontic Regeneration, Er-YAG laser, MTAD, QMix, EDTA, SCAP, stem cell adhesion.

The effect of intra-oral LED device and low-level laser therapy on orthodontic tooth movement in young adults: A randomized controlled trial.

INTRODUCTION: This randomized controlled clinical trial aimed to assess the effect of LED5 and LLLT6 in a three-arm parallel setting. METHODS: Sixty patients who needed the maxillary first premolar extraction were allocated to three groups using the stratified block randomization method. In the LED group, a custom-made device with a wavelength of 640nm and a power density of 40 mW/cm2 was used 5min/day. In the laser group, Ga Al As7 laser with a wavelength of 810nm and a power of 100 mW was used on days 0, 3, 30, and 60 each time for 18seconds. Patients in the control group received placebo treatment as the laser group protocol, using a coated light cure device. Models were made at baseline and monthly until the end of the retraction. The rate of canine retraction was the primary outcome, while canine rotation and pain were secondary outcomes. The final data were anonymous for the outcome assessor and statistical consultant. Data were analyzed per protocol using a linear mixed model. RESULTS: The rate of canine retraction significantly increased by 60.8% in the laser group, while it increased not significantly by 26% in the LED group compared with the control group. There was no significant difference among the groups in terms of tooth rotation and pain. CONCLUSIONS: LLLT can accelerate orthodontic tooth movement (OTM). LED with the present setting couldn't increase the rate of OTM. LLLT and LED did not affect canine rotation or pain. TRIAL REGISTRATION: IRCT20120220009086N4. On 1 June 2019 was retrospectively registered.

Effect of 940 nm laser diode irradiation prior to bonding procedure on postoperative sensitivity following class II composite restorations: a split-mouth randomized clinical trial.

The aim of this study was to evaluate the effect of 940 nm laser diode on class II composite cavities prior to bonding and restoration process on the postoperative sensitivity (POS). Thirty patients with two bilateral premolars with mesio or disto-occlusal carious lesions were evaluated. In each patient, the teeth were randomly divided into the control and laser groups. After cavity preparation and isolation and before the bonding process, the laser group was subjected to 940 nm irradiation (Epic 10, Biolase, USA) by 400 µ tip continuously at 100 mW with 398 J/cm2 energy density of tip, which was applied for 5 s at a distance of 2 mm on the axial wall of the cavity. In the control group, irradiation was performed by using the aiming beam. Access cavity was then restored with a composite resin. Cold sensitivity was measured using a cold spray application on the middle third of teeth buccal surface at baseline (before the intervention), 1, 14, and 30 days after the restoration by visual analog scale (VAS) criteria. The mean Friedman and Wilcoxon signed-rank tests were used for data analysis. It was shown that in both laser and control groups, the VAS was significantly decreased at all times compared to the baseline (p ≤ 0.05). There was no statistically significant difference between the mean VAS of two groups at baseline and first day (p ≤ 0.05), but at 14 and 30 days after the intervention, it was significantly lower in the laser group (p ≤ 0.05). The results of this study demonstrated that the cavity pretreatment with laser diode (940 nm) effectively reduces the postoperative sensitivity in class II composite restorations.

Effect of different surface treatments on shear bond strength of ceramic brackets to old composite.

BACKGROUND: At present, the demand for orthodontic treatment is on the rise. On the other hand, evidence shows that the bond strength of composite resins to old composite restorations is often unreliable. Therefore, the aim of this in vitro study was to assess the effect of different surface treatments on shear bond strength (SBS) of ceramic brackets to old composite restorations. METHODS: In this in vitro experimental study, 60 nano-hybrid composite discs were fabricated. For aging, the discs were incubated in deionized water at 37 °C for 1 month. Next, they underwent 4 different surface treatments namely acid etching with 37% phosphoric acid, sandblasting, grinding, and Er,Cr:YSGG laser irradiation. Ceramic brackets were then bonded to the discs and underwent SBS testing. RESULTS: The maximum mean SBS value was obtained in the grinding group (9.16 ± 2.49 MPa), followed by the sandblasting (8.13 ± 2.58 MPa) and laser (6.57 ± 1.45 MPa) groups. The minimum mean SBS value was noted in the control group (5.07 ± 2.14 MPa). CONCLUSION: All groups except for the control group showed clinically acceptable SBS. Therefore, grinding, sandblasting, and Er,Cr:YSGG laser are suggested as effective surface treatments for bonding of ceramic orthodontic brackets to aged composite.

Potentiation effects of antimicrobial photodynamic therapy on quorum sensing genes expression: A promising treatment for multi-species bacterial biofilms in burn wound infections.

BACKGROUND: As the increase in the prevalence of antimicrobial resistant bacterial strains, development of adjuvant antimicrobial approach for the treatment of burn wound infection is important. Therefore, the aim of this study was to assess the effectiveness of antimicrobial photodynamic therapy (aPDT) using indocyanine green (ICG) in reducing the bacterial load and expression profiling of the quorum sensing (QS) system associated with the biofilm formation in multi-species bacterial biofilms. MATERIALS AND METHODS: Multi-species bacterial suspension including Acinetobacter baumannii, Pseudomonas aeruginosa, and Staphylococcus aureus were photosensitized with ICG, which was excited at a wavelength of 810 nm. After evaluating the dose of ICG-aPDT contributing to the sub-significant reduction of colony forming unit (CFU)/mL, the gene expression levels of abaI, agrA, and lasI were assessed using real-time quantitative reverse transcription polymerase chain reaction. As well as, lipid peroxidation, superoxide radicals and reactive oxygen species (ROS) were measured and the morphological changes of multi-species bacteria were evaluated by scanning electron microscopy (SEM). RESULTS: According to the results, maximal sub-significant reduction dose of aPDT against CFUs/mL of multi-species bacterial cells was found with a combination of 31.2 µg/mL of ICG and irradiation by the diode laser for 1 min, with an estimated average output light energy 31.2 J/cm2. The expression levels of abaI, agrA, and lasI in A. baumannii, P. aeruginosa, and S. aureus were down-regulated to approximately 1.9-, 3.7-, and 4.9-fold, respectively. The amount of lipid peroxidation, superoxide radical production, and ROS generation significantly increased (P < 0.05). Also, the cell morphology under SEM showed that ICG-aPDT is a stressful condition for multi-species bacterial cells. CONCLUSIONS: ICG-aPDT with antimicrobial, anti-biofilm, and gene expression inhibitor characteristics, as well as, ROS generation can be used for the treatment of burn wound infections in vivo.

Effects of motion direction and power of Er,Cr:YSGG laser on pull-out bond strength of fiber post to root dentin in endodontically-treated single-canal premolar teeth.

BACKGROUND: Inadequate retention and gradual debonding of intracanal post from root dentin is a major cause of failure of endodontically treated teeth restored with fiber post. MAIN BODY: This study aimed to assess the effect of surface treatment of quartz fiber posts with different powers and motion directions of Er,Cr:YSGG laser on their pull-out bond strength to root dentin in endodontically treated premolar teeth. In this study, 105 fiber posts were divided into 7 groups according to their surface treatment with different powers of Er,Cr:YSGG laser at 2780 nm wavelength, 20 Hz frequency and 150 µs pulse duration in circumferential (C) or longitudinal (L) motion directions: Control group (no treatment), 0.5 W laser in longitudinally (L0.5), 1.0 W laser in longitudinally (L1), 1.5 W laser in longitudinally (L1.5), 0.5 W laser in circumferentially (C0.5), 1.0 W laser in circumferentially (C1) and 1.5 W laser in circumferentially (C1.5). After cementation, pull-out bond strength was measured in Newton (N). Each sample was inspected under a stereomicroscope at × 25 magnification to determine the mode of failure. Two samples of each group were inspected under a scanning electron microscope (SEM). Data were analyzed using two-way ANOVA and Tukey's test with significant level of 0.05. The pull-out bond strength of 0.5 W groups had significant differences with the control group (P = 0.009). The bond strength of 1.0 W and 1.5 W groups were not significantly different (P = 0.630) but were higher than the control and 0.5 W groups (P < 0.001). Motion direction of laser irradiation had no significant effect on the bond strength (P = 0.384). The interaction effect of power and motion direction of laser irradiation had no significant effect on the bond strength (P = 0.092). CONCLUSION: Fiber posts treated with 0.5, 1.0 and 1.5 W Er,Cr:YSGG laser showed higher bond strength to dentin compared to posts with no surface treatment. However, the motion directions of laser irradiation had no significant effect on the bond strength. In order to minimize damage to post surface and achieving maximum bond strength, longitudinal surface treatment of posts with 1.0 W power of Er,Cr:YSGG laser is recommended.

Comparison of conventional and laser-aided fiberotomy in relapse tendency of rotated tooth: A randomized controlled clinical trial.

INTRODUCTION: The aim of the present study was to compare the tendency of mandibular incisor rotation relapse after conventional circumferential supracrestal fiberotomy (CSF) with Er,Cr:YSGG laser-aided CSF. METHODS: In this three-arm parallel study, the patients with one lower incisor rotation greater than 30 degrees before treatment were selected. The patients were randomly assigned to three groups in a 1:1:1 ratio. Rotational relapse tendency was measured on a digitized model one month after arch wire removal. Probing depth, clinical crown height and pain levels were also measured. RESULTS: A total of 46 patients were recruited. Relapse tendency in conventional CSF and laser-aided CSF groups were 5.09±1.59° and 4.87±2.08°, respectively, and significantly lower than 11.28±2.93° in the control group (P<0.001). Relapse tendency was not different between the conventional CSF and laser CSF groups. Probing depth, clinical crown height, and experienced pain levels exhibited negligible differences. CONCLUSIONS: Er,Cr:YSGG laser-aided CSF in one month was as effective in reducing rotational relapse tendency of mandibular incisor teeth as conventional CSF.

Effect of Erbium, Chromium-Doped: Yttrium, Scandium, Gallium, and Garnet and Erbium: Yttrium-Aluminum-Garnet Laser Etching on Enamel Demineralization and Shear Bond Strength of Orthodontic Brackets.

OBJECTIVE: The objective of this study was to compare the effect of two types of laser irradiation (erbium, chromium-doped: yttrium, scandium, gallium, and garnet [Er,Cr:YSGG] and erbium: yttrium-aluminum-garnet [Er:YAG]) and acid etching on enamel demineralization and shear bond strength (SBS) of orthodontic bracketsastry. MATERIALS AND METHODS: Ninety premolars were selected, scaled, and polished with no fluoridated pumice, and metal brackets were bonded to them. Then, they were randomly allocated to three groups based on the etching procedure: phosphoric acid etching, Er:YAG (100 mJ, 10 Hz) laser etching, and Er,Cr:YSGG (600 mJ, 20 Hz) laser etching. Teeth to be evaluated for demineralization and SBS were exposed to pH and thermal cycling, respectively. For SBS test, a universal testing machine was used, and adhesive remnant was index scored after debonding. Microhardness of enamel was evaluated with Vickers test. Data were analyzed statistically (α = 0.05). RESULTS: The acid-etched group exhibited significantly higher SBS values compared to the laser groups (P < 0.05); however, the difference between the Er:YAG and Er,Cr:YSGG laser groups was not significant. Microhardness mean values in descending order were as follows: Er,Cr:YSGG, Er:YAG, and acid etched. There were significant differences between the laser and control groups (P < 0.001); however, the difference between the two laser groups was not significant (P = 0.320). There were no significant differences between the three groups in adhesive remnant index scores. CONCLUSION: Er:YAG and Er,Cr:YSGG laser etching resulted in clinically acceptable SBS; therefore, apart from its other advantages over acid etching, it can be a good appropriate alternative for bonding of orthodontic brackets.

Effect of CO2 Laser and Fluoride Varnish Application on Microhardness of Enamel Surface Around Orthodontic Brackets.

Introduction: Orthodontic treatment has many advantages such as esthetic improvement and self-esteem enhancement; yet it has some disadvantages such as increasing the risk of formation of white spot lesions, because it makes oral hygiene more difficult. It is rational to implement procedures to prevent these lesions. The present study was aimed to assess the effect of CO2 laser and fluoride varnish on the surface of the enamel surface microhardness around the orthodontic braces. Methods: Eighty extracted premolar teeth were selected, scaled, polished with nonfluoridated pumic and metal brackets were bonded to them. Then, they were randomly allocated to 5 groups: control (neither fluoride nor laser is used on enamel surfaces), fluoride (4 minutes fluoride varnish treatment of the enamel surfaces), CO2 laser (10.6 µm CO2 laser irradiation of the teeth), laserfluoride (fluoride application after laser irradiation) and fluoride-laser (fluoride was applied and then teeth were irradiated with laser). After surface treatment around brackets on enamel, the samples were stored in 0.1% thymol for less than 5 days and then they were exposed to a 10-day microbiological caries model. Microhardness values of enamel were evaluated with Vickers test. One sample of each group (5 teeth from 80 samples) was prepared for SEM (scanning electron microscopy) and the data from 75 remaining teeth were analyzed with analysis of variance (ANOVA) and chi-square tests (α =0.05). Results: Microhardness mean values from high to low were as follow: fluoride-laser, laser-fluoride, laser, fluoride and control. Microhardness in fluoride-laser group was significantly higher compared with that of the control group. Distribution adhesive remnant index (ARI) scores were significantly different between groups and most of bond failures occurred at the enamel-adhesive interface in groups 2 to 5 and at the adhesive-bracket interface in the control group. Conclusion: Combination of fluoride varnish and CO2 laser irradiation can reduce enamel demineralization around orthodontic brackets.

Effect of CPP-ACP paste with and without CO2 laser irradiation on demineralized enamel microhardness and bracket shear bond strength.

INTRODUCTION:: Many patients seeking orthodontic treatment already have incipient enamel lesions and should be placed under preventive treatments. The aim of this in vitro study was to evaluate the effect of CPP-ACP paste and CO2 laser irradiation on demineralized enamel microhardness and shear bond strength of orthodontic brackets. METHODS:: Eighty caries-free human premolars were subjected to a demineralization challenge using Streptococcus mutans. After demineralization, the samples were randomly divided into five equal experimental groups: Group 1 (control), the brackets were bonded without any surface treatment; Group 2, the enamel surfaces were treated with CPP-ACP paste for 4 minutes before bonding; Group 3, the teeth were irradiated with CO2 laser beams at a wavelength of 10.6 µm for 20 seconds. The samples in Groups 4 and 5 were treated with CO2 laser either before or through CPP-ACP application. SEM photomicrographs of a tooth from each group were taken to observe the enamel surface. The brackets were bonded to the buccal enamel using a conventional method. Shear bond strength of brackets and ARI scores were measured. Vickers microhardness was measured on the non-bonded enamel surface. Data were analyzed with ANOVA and Tukey test at the p< 0.05 level. RESULTS:: The mean shear bond strength and microhardness of the laser group were higher than those in the control group and this difference was statistically significant (p< 0.05). All groups showed a higher percentage of ARI score 4. CONCLUSION:: CO2 laser at a wavelength of 10.6 µm significantly increased demineralized enamel microhardness and enhanced bonding to demineralized enamel.

Effect of CPP-ACP paste with and without CO2 laser irradiation on demineralized enamel microhardness and bracket shear bond strength

ABSTRACT Introduction: Many patients seeking orthodontic treatment already have incipient enamel lesions and should be placed under preventive treatments. The aim of this in vitro study was to evaluate the effect of CPP-ACP paste and CO2 laser irradiation on demineralized enamel microhardness and shear bond strength of orthodontic brackets. Methods: Eighty caries-free human premolars were subjected to a demineralization challenge using Streptococcus mutans. After demineralization, the samples were randomly divided into five equal experimental groups: Group 1 (control), the brackets were bonded without any surface treatment; Group 2, the enamel surfaces were treated with CPP-ACP paste for 4 minutes before bonding; Group 3, the teeth were irradiated with CO2 laser beams at a wavelength of 10.6 µm for 20 seconds. The samples in Groups 4 and 5 were treated with CO2 laser either before or through CPP-ACP application. SEM photomicrographs of a tooth from each group were taken to observe the enamel surface. The brackets were bonded to the buccal enamel using a conventional method. Shear bond strength of brackets and ARI scores were measured. Vickers microhardness was measured on the non-bonded enamel surface. Data were analyzed with ANOVA and Tukey test at the p< 0.05 level. Results: The mean shear bond strength and microhardness of the laser group were higher than those in the control group and this difference was statistically significant (p< 0.05). All groups showed a higher percentage of ARI score 4. Conclusion: CO2 laser at a wavelength of 10.6 µm significantly increased demineralized enamel microhardness and enhanced bonding to demineralized enamel.

RESUMO Introdução: muitos pacientes, ao buscar o tratamento ortodôntico, já apresentam lesões incipientes no esmalte e precisam ser submetidos a tratamentos preventivos. O objetivo do presente estudo in vitro foi avaliar o efeito da pasta CPP-ACP e da irradiação com laser de CO2 na microdureza do esmalte desmineralizado e na resistência ao cisalhamento de braquetes ortodônticos. Métodos: oitenta pré-molares humanos hígidos foram submetidos a desmineralização usando Streptococcus mutans. Após a desmineralização, as amostras foram divididas aleatoriamente em cinco grupos experimentais: Grupo 1 (controle), os braquetes foram colados sem qualquer tratamento de superfície; Grupo 2, a superfície do esmalte foi tratada com pasta CPP-ACP por 4 minutos antes da colagem; Grupo 3, os dentes foram irradiados com laser de CO2 no comprimento de onda de 10,6 µm, por 20 segundos; Grupos 4 e 5, as amostras foram tratadas com laser de CO2 antes ou durante a aplicação de CPP-ACP. Foram feitas fotomicrografias por Microscopia Eletrônica de Varredura (MEV) de um dente de cada grupo, para avaliação da superfície do esmalte. Os braquetes foram colados ao esmalte na face vestibular, usando-se o método convencional. Foram medidos a resistência ao cisalhamento dos braquetes e o escore do Índice de Adesivo Remanescente (ARI). A microdureza Vickers foi medida nas superfícies do esmalte onde não foi realizada colagem. Os dados foram analisados com ANOVA e teste Tukey ao nível de p< 0,05. Resultados: a média da força de resistência ao cisalhamento e da microdureza do grupo laser foi superior à do grupo controle, com diferença estatisticamente significativa (p < 0,05). Todos os grupos apresentaram maior porcentagem do escore ARI=4. Conclusões: o laser de CO2 no comprimento de onda de 10,6 µm aumentou significativamente a microdureza do esmalte desmineralizado e melhorou a adesão dos braquetes nele.

Effect of Accelerated Artificial Aging on Translucency of Methacrylate and Silorane-Based Composite Resins.

OBJECTIVES: Composite restorations must have tooth-like optical properties namely color and translucency and maintain them for a long time. This study aimed to compare the effect of accelerated artificial aging (AAA) on the translucency of three methacrylate-based composites (Filtek Z250, Filtek Z250XT and Filtek Z350XT) and one silorane-based composite resin (Filtek P90). MATERIALS AND METHODS: For this in vitro study, 56 composite discs were fabricated (n=14 for each group). Using scanning spectrophotometer, CIE L*a*b* parameters and translucency of each specimen were measured at 24 hours and after AAA for 384 hours. Data were analyzed using one-way ANOVA, Tukey's test and paired t-test at P=0.05 level of significance. RESULTS: The mean (±standard deviation) translucency parameter for Filtek Z250, Filtek Z250XT, Filtek Z350XT and Filtek P90 was 5.67±0.64, 4.59±0.77, 7.87±0.82 and 4.21±0.71 before AAA and 4.25±0.615, 3.53±0.73, 5.94±0.57 and 4.12±0.54 after AAA, respectively. After aging, the translucency of methacrylate-based composites decreased significantly (P<0.05). However, the translucency of Filtek P90 did not change significantly (P>0.05). CONCLUSIONS: The AAA significantly decreased the translucency of methacrylate-based composites (Filtek Z250, Filtek Z250XT and Filtek Z350XT) but no change occurred in the translucency of Filtek P90 silorane-based composite.

The Effect of Epigallocatechin Gallate on the Dentin Bond Durability of Two Self-etch Adhesives.

STATEMENT OF THE PROBLEM: Self-etch adhesives can activate matrix metalloproteinase (MMP) which hydrolyzes organic matrix of demineralized dentin. Epigallocatechin gallate (EGCG), especially found in green tea, could inhibit the activation of MMP. PURPOSE: The aim of this study was to evaluate the effect of adding Epigallocatechin gallate (EGCG) into two types of adhesives on dentin bond strength. MATERIALS AND METHOD: In this experimental study, 64 extracted third molars were randomly divided into 16 groups. Clearfil SE Bond and Filtek Silorane System with 0 µM, 25µM, 50µM, and 100µM concentration of 95% EGCG were used for bonding. Following the bonding and fabrication of beams (1±0.1 mm(2)) and storage in distilled water, the specimens were subjected to thermal cycles. Microtensile bond strengths of 8 groups were examined after 24 hours and others were tested after 6 months. The fracture modes of specimens were evaluated by stereomicroscope and SEM. Data were analyzed by three-way ANOVA and t-test (α = 0.05). RESULTS: The results of the three- way ANOVA test showed that types of bonding, storage time and interactive effect of EGCG concentration and bonding influenced the bond strength of specimens significantly (p<0.05). The results of the t-test indicated that storage time only had significant effect on bond strength of Clearfil SE Bond with no EGCG (p= 0.017). The most common failure modes in Filtek Silorane System groups and Clearfil SE Bond groups were adhesive and mixed/cohesive, respectively. The results of SEM at different magnifications showed that most fractures have occurred in the hybrid layer. CONCLUSION: Although adding 100 µM volume of EGCG to Clearfil SE Bond can preserve the dentin bond, incorporation of EGCG in the silorane system, especially in high concentrations, decreases the bond strength after 6 months.