Effect of Er,Cr:YSGG laser on the surface of composite restoratives during in-office tooth bleaching

The aim of this in vitro study was to investigate the effect of Er,Cr:YSGG laser on the surface roughness and microhardness of various composite restoratives during in-office tooth bleaching. Five highly viscous composite restoratives and three flowable composite restoratives were investigated. Thirty cylindrical specimens of each material were made using Teflon molds. The specimens of each composite were randomly divided into three groups (n?=?10). Group 1 specimens did not receive bleaching treatment, group 2 received a conventional in-office bleaching treatment, and group 3 received a laser-assisted in-office bleaching treatment using an Er,Cr:YSGG laser. Two-way ANOVA was used to determine significant interactions between materials and bleaching methods. One-way ANOVA and Tukey’s post hoc test were used to compare the mean surface microhardness and roughness between materials for each treatment group (a?=?0.05). Τhere were no significant differences in surface microhardness between the two bleached experimental groups for all the tested composites (p?>?0.05). The reduction of surface microhardness after bleaching procedures ranged from 0.72 to 16.93 % for the specimens received conventional treatment and from 1.30 to 11.51 % for those received laser-assisted treatment. Moreover, there were no significant differences in Ra values between the experimental groups (p?>?0.05) in all cases. The increase of surface roughness after the bleaching treatments was negligible and was between 0.43 and 4.78 %. The use of Er,Cr:YSGG laser during in-office tooth bleaching treatment did not affect the surface microhardness and roughness of the tested composite restorative materials.     

In vitro comparison of an Er:YAG laser-activated bleaching system with different light-activated bleaching systems for color change,surface roughness,and enamel bond strength

To compare an Er:YAG laser-activated bleaching system with different light-activated in-office bleaching systems for color change, surface roughness, and post-bleaching enamel bond strength. 51 enamel slabs were prepared from the sound buccal enamel of extracted bovine teeth. The teeth were randomly divided into three groups according to different light-activated office bleaching systems (n?=?17): diode laser (Epic, Biolase) (940 nm, 7 W, continuous mode), Er:YAG laser (LightWalker, Fotona) (2940 nm, 50 mJ, 10 Hz, 1000 μs), and LED (Radii Plus) (440–480 nm, 1500 mW/cm²). All systems were used with their compatible bleaching agents according to manufacturers’ recommendations. The tooth color and surface roughness (Ra) were assessed at baseline and after bleaching using a spectrophotometer and a surface profilometer, respectively. The color change was determined by the CIE L*a*b* system (ΔE, ΔL*, Δa*, Δb*). Kruskal-Wallis test was used for color change whereas Kruskal-Wallis and Wilcoxon tests were used to analyze the roughness data. For shear bond strength test (SBS), composite cylinders were bonded on bleached enamel samples 14 days after bleaching procedures and stored in water (37 °C). Specimens were then debonded with a universal testing machine at 1 mm/min and data were analyzed by using Kruskal-Wallis test. All the tested bleaching systems were effective on color change (ΔE?>?3.3) and produced similar color change (p?>?0.05). There were no significant differences among the Ra values of the groups neither at baseline nor after bleaching (p?>?0.05). However, comparing the baseline and after bleaching Ra values, a significant increase was observed for all tested groups (p?<?0.05). Significant differences were also found among all systems for SBS (p?<?0.05). The highest values were obtained in Er:YAG group, whereas the LED group revealed the lowest values (p?<?0.05). All tested bleaching systems were effective on tooth whitening, whereas they all led to an increase on surface roughness. Although the current Er:YAG laser-activated bleaching system did not differ from other tested bleaching systems according to color change and surface roughness, it appears to provide better results in terms of SBS.     

Evaluation of acquired acid resistance of enamel surrounding orthodontic brackets irradiated by laser and fluoride application

Demineralization of enamel around orthodontic brackets is a clinical problem which can lead to some esthetic concerns like white spot lesions. The aim of this in vitro study was to evaluate the effect of the Er, Cr:YSGG laser and fluoride application on the acid resistance of enamel adjacent to orthodontic brackets. A total of 60 healthy, permanent, human premolars were selected and bonded with brackets, then they were randomly assigned to four groups (n?=?15): topical APF gel (1.23 % F, pH 3.5, for 4 min); Er,Cr:YSGG laser (P:0.25 W, E:12.5 mJ, RR:20 Hz, PD:140 μs, 11 % air, without water, for 10 s); fluoride + laser group (F + L), and control group (C). All specimens were demineralized for 10 days in a 0.2 M acetate buffer solution, and the calcium content were subsequently determined with atomic absorption spectrometry. There were significant differences between the calcium content of F + L and F group in comparison to control group. The least concentration of calcium was seen in F + L group, and the most value was observed in C group. Combination of Er, Cr:YSGG laser with fluoride and fluoride alone decreased enamel solubility significantly more than laser alone. In addition, combination of laser and fluoride leads to less consumption of fluoride amount. And patients can use it at the beginning of treatment instead of daily use of fluoride. So we suggest using it in preventing enamel demineralization around orthodontic brackets.     

The effect of erbium family laser on tensile bond strength of composite to dentin in comparison with conventional method

The purpose of this study was to evaluate the effect of Er:YAG and Er,Cr:YSGG laser on tensile bond strength of composite resin to dentine in comparison with bur-prepared cavities. Fifteen extracted caries-free human third molars were selected. The teeth were cut at a level below the occlusal pit and fissure plan and randomly divided into three groups. Five cavities were prepared by diamond bur, five cavities prepared by Er:YAG laser, and the other group prepared by Er,Cr:YSGG laser. Then, all the cavities were restored by composite resin. The teeth were sectioned longitudinally with Isomet and the specimens prepared in dumbbelled shape (n?=?36). The samples were attached to special jigs, and the tensile bond strength of the three groups was measured by universal testing machine at a speed of 0.5 mm/min. The results of the three groups were analyzed with one-way ANOVA and Tamhane test. The means and standard deviations of tensile bond strength of bur-cut, Er:YAG laser-ablated, and Er,Cr:YSGG laser-ablated dentine were 5.04?±?0.93, 13.37?±?3.87, and 4.85?±?0.93 MPa, respectively. There is little difference in tensile bond strength of composite resin in Er,Cr:YSGG lased-prepared cavities in comparison with bur-prepared cavities, but the Er:YAG laser group showed higher bond strength than the other groups.     

Er,Cr:YSGG laser influence on microleakage of class V composite resin restorations

One of the most challenging issues following restoration is microleakage. The aim of this study was to investigate the effects of Er,Cr:YSGG laser with and without acid etching on microleakage of class V composite restorations. A total of 68 human intact premolars were selected, disinfected, and randomly allocated to four experimental groups (n?=?16) as well as positive and negative controls (n?=?2 each). Dimensionally, similar class V cavities were prepared on buccal surface of each tooth under the following conditions: group 1, bur cavity preparation and chemical etching (BE); group 2, bur cavity preparation and Er,Cr:YSGG laser conditioning (BLc); group 3, Er,Cr:YSGG laser cavity preparation and chemical etching (LE); and group 4, Er,Cr:YSGG laser cavity preparation and Er,Cr:YSGG laser conditioning (LLc). All samples were restored with composite. The teeth were sealed and immersed in 1 % methylene blue for 48 h before being sectioned. The microleakage evaluation was done under a stereomicroscope (×20). The leakage scores were recorded and Kruskal–Wallis and Mann–Whitney tests were used for statistical evaluations. The highest microleakage score was seen in gingival margins of group 4 (LLc) and the lowest in occlusal margins of group 3 (LE). The overall difference in leakage scores among the groups was statistically significant (p?<?0.001) with gingival margins showing a significantly higher score than its occlusal counterparts (p?<?0.001). It was noted that less microleakage could be achieved when cavities were prepared by laser compared to bur. In addition, less microleakage was seen in acid-etched cavities than laser-conditioned counterparts.     

Laser-assisted in-office bleaching using a neodymium:yttrium–aluminum–garnet laser: an in vivo study

The desire for perfect and white teeth can be accomplished in aesthetical dentistry by modern tooth bleaching methods. Within the scope of a clinical study, laser assisted in-office bleaching was applied to the teeth of 20 individual patients with a neodymium:yttrium–aluminum–garnet (Nd:YAG) laser (λ?=?1.064 µm, average power 4 W, pulse repetition rate 10 Hz, pulse duration 320 µs). The treatment was carried out in a split-mouth design, each patient having two appointments with 1 week in between. Laser activation of the bleaching agent was performed on teeth 14–11 and 34–31 per session, with a total irradiation time of 30 s per tooth. The initial and the final color of the teeth were ascertained by VITA Colorsticks and the dental chromatometer ShadeEye NCC®. Whitening was detected in the laser-activated and in the non-activated quadrants. Statistical evaluation showed that the additional activation of the bleaching agent by the Nd:YAG laser had produced no significant influence on the whitening (P?>?0.05). The results achieved in this study should be scrutinized critically. They give cause for one to reconsider the treatment conditions or the laser parameters used, or even to query the application of the Nd:YAG laser in general during in-office bleaching.     

Efficacy of Er,Cr:YSGG laser with endodontical radial firing tips on the outcome of endodontic treatment: blind randomized controlled clinical trial with six-month evaluation

Clinical reports stating the efficacy of novel root canal disinfection protocols are an important focus in endodontic research. This blind randomized clinical trial assessed the clinical efficacy of the erbium, chromium:yttrium–scandium–gallium–garnet (Er,Cr:YSGG) laser radial firing tips (RFT) versus the concomitant use of 3 % sodium hypochlorite and interim calcium hydroxide paste in necrotic teeth with chronic apical periodontitis. We hypothesized to find similar or improved bone healing in the laser-assisted endodontic treatment. Thirty-six anterior and premolar teeth were randomly assigned. In group 1, teeth were prepared with 3 % sodium hypochlorite for irrigation and calcium hydroxide as inter-appointment dressing; in group 2, teeth were prepared with saline solution and irradiated with Er,Cr:YSGG laser using RFT2 (140 μs, 37.5 mJ, 20 Hz) and RFT3 (140 μs, 62.5 mJ, 20 Hz) in the first and second appointment, respectively, four times each, moving at 2 mm s^?1 from apical to coronal. The primary outcome measure was changed in apical bone density at 6 months, using the periapical index (PAI) for blind radiographic evaluation. Twenty-nine patients were examined and subjected to statistical analysis, 12 in group 1 and 17 in group 2. There was one treatment failure in group 1. Both groups gave similar outcomes exhibiting statistically significant decreases in PAI scores.     

Influence of etching time on bond strength in dentin irradiated with erbium lasers

The purpose of this in vitro study was to evaluate the effect of etching time on the tensile bond strength (TBS) of a conventional adhesive bonded to dentin previously irradiated with erbium:yttrium–aluminum–garnet (Er:YAG) and erbium, chromium:yttrium–scandium–gallium–garnet (Er,Cr:YSGG) lasers. Buccal and lingual surfaces of 45 third molars were flattened until the dentin was exposed and randomly assigned to three groups (n?=?30) according to the dentin treatment: control (not irradiated), irradiated with Er:YAG (1 W; 250 mJ; 4 Hz; 80.6 J/cm²) laser or Er,Cr:YSGG (4 W; 200 mJ; 20 Hz; 71.4 J/cm²) laser, and into three subgroups (n?=?10) according to acid etching time (15 s, 30 s or 60 s) for each experimental group. After acid etching, the adhesive was applied, followed by the construction of an inverted cone of composite resin. The samples were immersed in distilled water (37°C for 24 h) and subjected to TBS test [50 kilogram-force (kgf), 0.5 mm/min]. Data were analyzed by analysis of variance (ANOVA) and Tukey statistical tests (P?≤?0.05). Control group samples presented significant higher TBS values than those of all lased groups. Both irradiated groups exhibited similar TBS values. Samples subjected to the different etching times in each experimental group presented similar TBS. Based on the conditions of this in vitro study we concluded that Er:YAG and Er,Cr:YSGG laser irradiation of the dentin weakens the bond strength of the adhesive. Moreover, increased etching time is not able to modify the bonding strength of the adhesive to irradiated dentin.     

Effect of low-level laser therapy on tooth sensitivity induced by in-office bleaching

This study aimed to investigate the effect of low-level laser therapy (LLLT) on tooth sensitivity induced by in-office bleaching. Sixty-six patients enrolled in this randomized clinical trial. Following the in-office procedure with 40 % hydrogen peroxide, the participants were randomly divided into three groups. The patients in group 1 received irradiation from a low-level red laser (LLRL; 660 nm, 200 mW, 15 s, 12 J/cm²), whereas participants in group 2 were subjected to a low-level infrared laser (LLIL; 810 nm) under similar conditions as in group 1. In group 3 (placebo), the laser treatment was the same as that in groups 1 and 2, but without energy output. The degree of tooth sensitivity was recorded at 1, 24, and 48 h after bleaching using a visual analog scale (VAS). The change in tooth shade was measured 30 days after tooth whitening. The intensity of tooth sensitivity was not significantly different between groups at 1 h after bleaching (p?>?0.05). At 24 h after therapy, pain level was significantly lower in the LLIL group compared to the LLRL and placebo groups (p?<?0.05). At 48 h after bleaching, VAS scores in the LLIL and LLRL groups were comparable to each other (p?>?0.05) and both were significantly lower than that of the placebo group (p?<?0.05). There was no significant difference in the efficacy of tooth whitening among groups (p?>?0.05). LLLT with an infrared diode laser could be recommended as a suitable strategy to reduce the intensity of tooth sensitivity after in-office bleaching.     

Microtensile bond strength analysis of adhesive systems to Er:YAG and Er,Cr:YSGG laser-treated dentin

The aim of this in vitro study was to evaluate the effect of different surface treatments (control, diamond bur, erbium-doped yttrium aluminum garnet (Er:YAG) laser, and erbium, chromium:yttrium–scandium–gallium–garnet (Er,Cr:YSGG) laser) on sound dentin surface morphology and on microtensile bond strength (μTBS). Sixteen dentin fragments were randomly divided into four groups (n?=?4), and different surface treatments were analyzed by scanning electron microscopy. Ninety-six third molars were randomly divided into eight groups (n?=?12) according to type of surface treatment and adhesive system: G1 = Control + Clearfil SE Bond (SE); G2 = Control + Single Bond (SB); G3 = diamond bur (DB) + SE; G4 = DB + SB, G5 = Er:YAG laser (2.94 μm, 60 mJ, 2 Hz, 0.12 W, 19.3 J/cm²) + SE; G6 = Er:YAG + SB, G7 = Er,Cr:YSGG laser (2.78 μm, 50 mJ, 30 Hz, 1.5 W, 4.5 J/cm²) + SE; and G8 = Er,Cr:YSGG + SB. Composite blocks were bonded to the samples, and after 24-h storage in distilled/deionized water (37 °C), stick-shaped samples were obtained and submitted to μTBS test. Bond strength values (in megapascal) were analyzed by two-way ANOVA and Tukey tests (α?=?0.05). G1 (54.69?±?7.8 MPa) showed the highest mean, which was statistically significantly higher than all the other groups (p?<?0.05). For all treatments, SE showed higher bond strength than SB, except only for Er,Cr:YSGG treatment, in which the systems did not differ statistically from each other. Based on the irradiation parameters considered in this study, it can be concluded that Er:YAG and Er,Cr:YSGG irradiation presented lower values than the control group; however, their association with self-etching adhesive does not have a significantly negative effect on sound dentin (μTBS values of >20 MPa).     

Comparative efficacy of Er,Cr:YSGG and Er:YAG lasers for etching of composite for orthodontic bracket bonding

Several techniques have been proposed to obtain a durable bond, and the efficacy of these techniques is assessed by measuring parameters such as bond strength. Laser has provided a bond strength as high as that of acid etching in vitro and has simpler use with shorter clinical time compared to acid etching. This study aimed to compare the efficacy of Er:YAG and Er,Cr:YSGG lasers for etching and bonding of composite to orthodontic brackets. No previous study has evaluated the effect of these particular types of laser. A total of 70 composite blocks were randomly divided into five groups (n?=?14): group 1, etching with phosphoric acid for 20 s; group 2, Er:YAG laser irradiation with 2 W power for 10 s; group 3, Er:YAG laser with 3 W power for 10 s; group 4, Er,Cr:YSGG laser with 2 W power for 10 s; group 5, Er,Cr:YSGG laser with 3 W power for 10 s. Metal brackets were then bonded to composites, and after 5000 thermal cycles, they were subjected to shear bond strength test in a universal testing machine after 24 h of water storage. One sample of each group was evaluated under a scanning electron microscope (SEM) to assess changes in composite surface after etching. The adhesive remnant index (ARI) was calculated under a stereomicroscope. Data were statistically analyzed. The mean and standard deviation of shear bond strength were 18.65?±?3.36, 19.68?±?5.34, 21.31?±?4.03, 17.38?±?6.94, and 16.45?±?4.26 MPa in groups 1–5, respectively. The ARI scores showed that the bond failure mode in all groups was mainly mixed. The groups were not significantly different in terms of shear bond strength. Er:YAG and Er,Cr:YSGG lasers with the mentioned parameters yield optimal shear bond strength and can be used as an alternative to acid etching for bracket bond to composite.     

Reconditioning of ceramic orthodontic brackets with an Er,Cr:YSGG laser

It is now known that erbium lasers are effective in composite removal, but there is minimal information about their efficacy on recycling of ceramic brackets. This study, therefore, aimed to determine the percentage of remaining adhesive on the base and the shear bond strength of debonded ceramic brackets after being reconditioned by an Er,Cr:YSGG (erbium, chromium: yttrium–scandium–gallium–garnet) laser. Thirty premolars were divided into three groups, then bonded with mechanical retention ceramic brackets according to the bracket base conditions: (1) new brackets; (2) debonded brackets cleaned of adhesive with the Er,Cr:YSGG laser at 3.5 W; and (3) debonded brackets cleaned of adhesive with the Er,Cr:YSGG laser at 4 W. Before bonding, the percentage of remaining adhesive on the bases of reconditioned brackets was calculated by using stereomicroscopic images through an image processing software. The brackets were then tested in shear mode in a universal testing machine and the adhesive remnant index scores were determined. The percentage of remaining adhesive on the bases of brackets that were cleaned by the Er,Cr:YSGG laser at 4 W (3.1 %) was significantly lower than that of the 3.5-W laser group (5.9 %) (p?=?0.03). No significant difference was found in bond strengths between the new and the reconditioned brackets (p?=?0.19). The frequency of bond failure at the enamel-adhesive interface was lower in the laser-reconditioned brackets when compared to the new brackets. The application of Er,Cr:YSGG laser was efficient in removing adhesive from bases of debonded ceramic brackets because it produced comparable bond strengths to new brackets while reducing the risk of enamel damage during debonding.     

Effect of acid and laser etching on shear bond strength of conventional and resin-modified glass-ionomer cements to composite resin

Success in sandwich technique procedures can be achieved through an acceptable bond between the materials. The aim of this study was to compare the effect of 35% phosphoric acid and Er,Cr:YSGG laser on shear bond strength of conventional glass-ionomer cement (GIC) and resin-modified glass-ionomer cement (RMGIC) to composite resin in sandwich technique. Sixty-six specimens were prepared from each type of glass-ionomer cements and divided into three treatment groups as follows: without pretreatment, acid etching by 35% phosphoric acid for 15 s, and 1-W Er,Cr:YSGG laser treatment for 15 s with a 600-μm-diameter tip aligned perpendicular to the target area at a distance of 1 mm from the surface. Energy density of laser irradiation was 17.7 J/cm². Two specimens in each group were prepared for evaluation under a scanning electron microscope (SEM) after surface treatment and the remainder underwent bonding procedure with a bonding agent and composite resin. Then the shear bond strength was measured at a crosshead speed of 0.5 mm/min. Two-factor analysis of variance and post-hoc Tukey test showed that the cement type, surface treatment method, and the interaction of these two factors significantly affect the shear bond strength between glass-ionomer cements and composite resin (p < 0.05). Surface treatment with phosphoric acid or Er,Cr:YSGG laser increased the shear bond strength of GIC to composite resin; however, in RMGIC only laser etching resulted in significantly higher bond strength. These findings were supported by SEM results. The fracture mode was evaluated under a stereomicroscope at ×20.     

Influence of Er,Cr:YSGG laser irradiation on enamel caries prevention

The objective of this study was to evaluate the effects of chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation on the acid resistance of dental enamel. Forty human enamel samples were divided into four groups. They were manually irradiated with an Er,Cr:YSGG laser device (λ?=?2.78 µm, 20 Hz, 20 s), in a scanning mode, with and without water cooling, according to the following parameters: Group 1: 0.25 W, 62.5 J/cm², no water cooling; group 2: 0.25 W, 62.5 J/cm², 5.0 ml/min; group 3: 0.5 W, 125 J/cm², no water cooling; group 4: 0.5 W, 125 J/cm², 5.0 ml/min. No airflow was used. Afterwards, the samples were submitted to an acid challenge and assessed by cross-sectional Knoop microhardness at different depths (20, 40, 60, 80, and 100 µm) from the outer enamel surface. Average values were obtained for both irradiated and control areas in each sample and they were compared to obtain a percentage of microhardness increase. Data were analyzed by analysis of variance and Fisher’s exact test (α?=?5%). The percentage of microhardness increase observed in group 1 (+23.58%) was similar to group 3 (+19.12%), but higher than groups 2 (+3.61%) and 4 (10.9%) (p?<?0.05). The comparison of the depths showed that the Er,Cr:YSGG laser acted in the superficial layers of the dental enamel. The findings of the present study suggest that the energy densities of 62.5 and 125 J/cm² were capable of increasing the acid resistance of human enamel. The presence of water during irradiation makes it difficult to obtain an enamel surface more resistant to acids.     

Different light-activated in-office bleaching systems: a clinical evaluation

The aim of this clinical study was to evaluate the efficiency of in-office bleaching systems with different light sources for color change and possible side effects such as tooth sensitivity and gingival irritations. Forty healthy volunteers aged 18 years and older (average age 27.3 years), having all their natural healthy teeth in shade A3 or darker on the Vita shade guide, with no restorations on the buccal surfaces and no tooth sensitivity, participated in this study. Participants were randomly assigned to four groups of ten volunteers. Group 1 received bleaching without light activation (Opalescence Xtra Boost, Ultradent); group 2 received bleaching (Laser White 10, Biolase) with a diode laser (810 nm, 10 W/ Laser Smile, Biolase) activation; group 3 received bleaching treatment (Remewhite, Remedent) with a plasma arc lamp (400–490 nm, 2800 mV/cm², Remecure CL15), and group 4 received bleaching with a light emitting diode (LED) lamp (By White accelerator, Ensodent) according to the manufacturers’ recommendations. The shade was assessed with a classical Vita shade guide (Vita Zahnfabrik) and a digital spectrophotometer (Vita Easy Shade, Vident). The color of teeth was scored at baseline and 1 week after bleaching. Any side effects on teeth or gingiva was recorded by visual analog scale. Results were analyzed statistically, by one-way analysis of variance (ANOVA), Kruskal–Wallis, and Mann–Whitney U tests with Bonferroni correction. All the bleaching techniques resulted in shade change. No significant differences were found in the color change among the four groups with shade guide assessment (P > 0.05), but spectrophotometer readings exhibited significant differences among the groups (P < 0.05). The overall shade change values expressed as ΔL, Δa, Δb, ΔE for group 2 was significantly higher than those for the other groups (P < 0.05). Group 2 also showed lower tooth and gingival sensitivity scores than those of the other groups (P < 0.05). All techniques resulted in shade change. Although the shade guide evaluation did not exhibit any differences among the bleaching treatment groups, spectrophotometer readings showed different findings. The results obtained by the two methods of evaluation of shade change used in this study were different from each other. Bleaching with diode laser resulted in less tooth and gingival sensitivity than the other bleaching systems. Clinical relevance: in-office bleaching systems used with or without light, lead to a shade change. As bleaching with diode laser resulted in less tooth and gingival sensitivity, it might be preferred among in-office bleaching systems.     

Effects of different lasers on organic/inorganic ratio of radicular dentin

The aim of this study was to evaluate the chemical stability of endodontic-treated root dentin after different laser irradiations through Raman spectroscopy. Fifty maxillary canines were selected and prepared with K3 system. Roots were randomly distributed into five groups (n?=?10) according to the surface treatment: GI (water), GII (NaOCl?+?EDTA), GIII (NaOCl?+?EDTA?+?980 nm Diode laser), GIV (NaOCl?+?EDTA+ 1064 nm Nd: YAG laser) and GV (NaOCl?+?EDTA+ 2780 nm Er,Cr: YSGG laser). Lasers were applied for 20 s. Samples were bisected, and the organic and inorganic content of dentin was analyzed by Raman spectroscopy. Data were submitted to ANOVA and Tukey tests (p?<?0.05). None of the surface treatments alter the inorganic content (cts) (p?=?0.183). Roots irradiated with Er,Cr: YSGG laser had a reduced collagen content (GV-290.7?±?41.7) compared with the water-treated roots (GI-328.3?±?63.5) and those treated with NaOCl?+?EDTA (GII-333.9?±?55.8). Roots irradiated with Er,Cr: YSGG laser also showed a higher inorganic/organic ratio (GV-9.5?±?1.1) than roots treated with water (GI-7.7?±?1.5), NaOCl?+?EDTA (GII-8.0?±?1.4) and diode laser (GIII-8.2?±?1.6). Both organic and inorganic contents increased from cervical to apical thirds in all groups. None of the surface treatments were able to promote changes in the inorganic content of the root dentin; treatment with NaOCl?+?EDTA combined with Er,Cr: YSGG altered collagen.     

Effect of Er,Cr:YSGG laser on human dentin fluid flow

The aim of the current investigation was to assess the rate and magnitude of dentin fluid flow of dentinal surfaces irradiated with Er,Cr:YSGG laser. Twenty extracted third molars were sectioned, mounted, and irradiated with Er,Cr:YSGG laser at 3.5 and 4.5 W power settings. Specimens were connected to an automated fluid flow measurement apparatus (Flodec). The rate, magnitude, and direction of dentin fluid flow were recorded at baseline and after irradiation. Nonparametric Wilcoxon signed ranks repeated measure t test revealed a statistically significant reduction in fluid flow for all the power settings. The 4.5-W power output reduced the flow significantly more than the 3.5 W. The samples showed a baseline outward flow followed by inward flow due to irradiation then followed by decreased outward flow. It was concluded that Er,Cr:YSGG laser irradiation at 3.5 and 4.5 W significantly reduced dentinal fluid flow rate. The reduction was directly proportional to power output.     

Sealing ability of retrofilling materials following various root-end cavity preparation techniques

The aim of this study is to compare the sealing efficacy of the retrograde cavity preparations prepared and filled with different equipment and materials. In the study, low speed burs, ultrasonic or Er, Cr:YSGG laser devices were used for cavity preparations and ProRoot MTA and MTA-Angelus as filling materials. Seventy-eight single-rooted teeth were instrumented, root filled, and grouped. Root-end cavities were prepared and filled by using the following: Group 1: Low-speed carbide bur + ProRoot MTA; Group 2: Low-speed bur + MTA-Angelus; Group 3: Ultrasonic retrotips + ProRoot MTA; Group 4: Ultrasonic retrotips + MTA-Angelus; Group 5: Er, Cr:YSGG laser tips + ProRoot MTA; Group 6: Er, Cr:YSGG laser tips + MTA-Angelus. Microleakage was measured using a fluid filtration technique. Differences in the fluid movement among groups were analyzed with a two-way analysis of variance (ANOVA) and LSD test. The results showed a significant difference between the groups prepared with laser and carbide bur (p < 0.05). No difference was found between root-end filling materials (p > 0.05). According to the results of the study, the cavities prepared with Er, Cr:YSGG laser demonstrated significantly lower microleakage in all the filling materials considered.     

In vitro evaluation of erbium, chromium:yttrium-scandium-gallium-garnet laser-treated enamel demineralization

This study evaluated the effect of different parameters of erbium, chromium:yttrium–scandium–gallium–garnet (Er,Cr:YSGG) laser irradiation on enamel mineral loss in a simulated caries model. Forty-five enamel samples obtained from third molar teeth (3 mm× 3 mm) were randomly divided into five groups (n = 9): G1—Er,Cr:YSGG laser at 0.25 W, 20 Hz, 2.8 J/cm²; G2—Er,Cr:YSGG laser at 0.50 W, 20 Hz, 5.7 J/cm²; G3—Er,Cr:YSGG laser at 0.75 W, 20 Hz, 8.5 J/cm²; G4—sodium fluoride (NaF) dentifrice (positive control); G5—no treatment (negative control). After irradiation, the samples were submitted to 2 weeks of pH cycling. After the acid challenge, the samples were assessed by cross-sectional microhardness at different depths from the enamel surface. Analysis of variance (ANOVA) and Student–Newman–Keuls tests were performed (α = 5%). The percentage of lesion inhibition for each group was: G1 37%; G2 38%; G3 64%, and G4 50.5%. Regarding the relative mineral loss values (micrometers × volume percent), groups G1 (1,392 ± 522) and G2 (1,292 ± 657) did not differ significantly from each other, but both had higher values than group G3 (753 ± 287); the groups irradiated with Er,Cr:YSGG laser did not differ from group G4. Although the findings of the study revealed that Er,Cr:YSGG laser irradiation at 8.5 J/cm² can be an alternative for the enhancement of the enamel’s resistance to acid, lower energy densities also produced a cariostatic potential comparable to the use of fluoride dentifrice.     

The effect of Nd:YAG and Er,Cr:YSGG lasers on the microhardness of human dentin

The current investigation determined the microhardness of dentin tissue irradiated with erbium, chromium-doped yttrium scandium gallium garnet (Er,Cr:YSGG) and neodymium-doped yttrium–aluminum garnet (Nd:YAG) lasers. Thirty non-carious human molars were used in this study. Dentin disks were prepared by horizontal sectioning of one third of the occlusal surface. Halves of dentin specimens were irradiated with 3.5- and 4.5-W Er,Cr:YSGG lasers and with a 2-W Nd:YAG laser. The remaining halves served as controls. The microhardness measurements were recorded with a Vickers surface microhardness tester. The results were statistically evaluated by paired t test and one-way ANOVA (p?=?0.05). Laser irradiation has significantly reduced the microhardness of dentin within each group compared to its control. Moreover, statistically significant differences were observed among the different groups (p?<?0.05). The 3.5-W Er,Cr:YSGG laser produced the greatest reduction in microhardness of dentin followed by 4.5 W and Nd:YAG laser. The differences between all the groups were statistically significant. It was concluded that both laser devices used in this study have resulted in significant thermal damage and subsequent reduction in dentin microhardness values.