Combined effects of a topical fluoride treatment and 445 nm laser irradiation of enamel against a demineralization challenge: A light and electron microscopic ex vivo study.

This study investigated the caries-preventive effect of 445 nm laser radiation in combination with fluoride on the prevention of white spot lesions. Previously, several studies have indicated the ability of 488 nm argon ion laser irradiation to reduce early enamel demineralization. A diode laser (445 nm) could be an alternative technology for possible caries-preventive potential. Each sample of a group of seventeen caries-free bovine teeth was treated in four different ways on four different zones of the labial surface: control/no treatment (C), laser irradiation only (L) (0.3 W, 60 s and applied dose of 90 J/cm2), amine fluoride application only (10,000 ppm and pH 3.9) (F), and amine fluoride application followed by laser irradiation (FL). After treatment, the teeth were subjected to a demineralization solution (pH 4.3 for 48 h at 37 °C) to induce subsurface lesions. After sectioning, the teeth were examined by light microscopy. Three teeth were analyzed by scanning electron microscopy (SEM). The depths of the subsurface lesions in the C, L, F, and FL groups were 103.01 (± 13.04), 96.99 (± 14.51), 42.59 (± 17.13), and 24.35 (± 11.38) µm, respectively. The pairwise group comparison showed the following results: p < 0.001 for FL versus C, FL versus L, F versus C, and F versus L, p = 0.019 for FL versus F and p = 0.930 for L versus C. The SEM micrographs support the light-microscopic examination. The results of the current study have shown that using relatively low irradiation settings of 445 nm laser on fluoridated enamel may be effective for prevention of white spot lesions.

Effect of violet LED light on in-office bleaching protocols: a randomized controlled clinical trial.

Objective This study evaluated the clinical effect of violet LED light on in-office bleaching used alone or combined with 37% carbamide peroxide (CP) or 35% hydrogen peroxide (HP). Methodology A total of 100 patients were divided into five groups (n=20): LED, LED/CP, CP, LED/HP and HP. Colorimetric evaluation was performed using a spectrophotometer (ΔE, ΔL, Δa, Δb) and a visual shade guide (ΔSGU). Calcium (Ca)/phosphorous (P) ratio was quantified in the enamel microbiopsies. Measurements were performed at baseline (T 0 ), after bleaching (T B ) and in the 14-day follow-up (T 14 ). At each bleaching session, a visual scale determined the absolute risk (AR) and intensity of tooth sensitivity (TS). Data were evaluated by one-way (ΔE, Δa, ΔL, Δb), two-way repeated measures ANOVA (Ca/P ratio), and Tukey post-hoc tests. ΔSGU and TS were evaluated by Kruskal-Wallis and Mann-Whitney, and AR by Chi-Squared tests (a=5%). Results LED produced the lowest ΔE (p<0.05), but LED/HP promoted greater ΔE, ΔSGU and Δb (T 14 ) than HP (p<0.05). No differences were observed in ΔE and ΔSGU for LED/CP and HP groups (p>0.05). ΔL and Δa were not influenced by LED activation. After bleaching, LED/CP exhibited greater Δb than CP (p>0.05), but no differences were found between these groups at T 14 (p>0.05). LED treatment promoted the lowest risk of TS (16%), while HP promoted the highest (94.4%) (p<0.05). No statistical differences of risk of TS were found for CP (44%), LED/CP (61%) and LED/HP (88%) groups (p>0.05). No differences were found in enamel Ca/P ratio among treatments, regardless of evaluation times. Conclusions Violet LED alone produced the lowest bleaching effect, but enhanced HP bleaching results. Patients treated with LED/CP reached the same efficacy of HP, with reduced risk and intensity of tooth sensitivity and none of the bleaching protocols adversely affected enamel mineral content.

Effect of Er,Cr:YSGG Laser on the Prevention of Primary and Permanent Teeth Enamel Demineralization: SEM and EDS Evaluation.

Objective: To evaluate in vitro the effect of the erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on resistance of primary and permanent human enamel to demineralization using water cooling and fluoride coapplication as variable parameters. Methods: Enamel specimens were prepared from extracted primary and permanent teeth (n = 225 each). The specimens were separated into 15 subgroups (n = 15/group) based on laser application at three different power settings (0.25, 0.50, and 0.75 W), laser application with and without water cooling, and application of acidulated phosphate fluoride (APF) gel before laser treatment. Morphological changes were assessed with scanning electron microscopy (SEM), and the specimens' chemical contents were determined with energy-dispersive X-ray spectroscopy. Results: In both the primary and permanent teeth, the highest Ca and P content was observed in the noncooled 0.75 W laser group (p < 0.05), irrespective of APF pretreatment (p > 0.05). The Ca and P content for the noncooled APF +0.75 W laser group was lower than that for the APF group and the noncooled 0.75 W laser group. For both dentitions, the F mass content for the APF+laser groups was significantly higher than laser-only groups (p < 0.05). Under SEM, both the primary and permanent enamel exhibited cracks, craters, and surface roughness without water cooling, consistent with increased power output. Conclusions: Er,Cr:YSGG laser application at 0.75 W without water cooling increased enamel resistance to demineralization. Compared with topical APF application, Er,Cr:YSGG laser application barely improved enamel resistance against demineralization, and coapplication did not result in a synergistic effect.

Effect of violet LED light on in-office bleaching protocols: a randomized controlled clinical trial

Abstract Objective This study evaluated the clinical effect of violet LED light on in-office bleaching used alone or combined with 37% carbamide peroxide (CP) or 35% hydrogen peroxide (HP). Methodology A total of 100 patients were divided into five groups (n=20): LED, LED/CP, CP, LED/HP and HP. Colorimetric evaluation was performed using a spectrophotometer (ΔE, ΔL, Δa, Δb) and a visual shade guide (ΔSGU). Calcium (Ca)/phosphorous (P) ratio was quantified in the enamel microbiopsies. Measurements were performed at baseline (T 0 ), after bleaching (T B ) and in the 14-day follow-up (T 14 ). At each bleaching session, a visual scale determined the absolute risk (AR) and intensity of tooth sensitivity (TS). Data were evaluated by one-way (ΔE, Δa, ΔL, Δb), two-way repeated measures ANOVA (Ca/P ratio), and Tukey post-hoc tests. ΔSGU and TS were evaluated by Kruskal-Wallis and Mann-Whitney, and AR by Chi-Squared tests (a=5%). Results LED produced the lowest ΔE (p<0.05), but LED/HP promoted greater ΔE, ΔSGU and Δb (T 14 ) than HP (p<0.05). No differences were observed in ΔE and ΔSGU for LED/CP and HP groups (p>0.05). ΔL and Δa were not influenced by LED activation. After bleaching, LED/CP exhibited greater Δb than CP (p>0.05), but no differences were found between these groups at T 14 (p>0.05). LED treatment promoted the lowest risk of TS (16%), while HP promoted the highest (94.4%) (p<0.05). No statistical differences of risk of TS were found for CP (44%), LED/CP (61%) and LED/HP (88%) groups (p>0.05). No differences were found in enamel Ca/P ratio among treatments, regardless of evaluation times. Conclusions Violet LED alone produced the lowest bleaching effect, but enhanced HP bleaching results. Patients treated with LED/CP reached the same efficacy of HP, with reduced risk and intensity of tooth sensitivity and none of the bleaching protocols adversely affected enamel mineral content.

Effect of 2.94 µm Er: YAG laser on the chemical composition of hard tissues.

The aim was to investigate the effect of the Er-YAG laser radiation on morphology and chemical composition of enamel, dentin, and bone. The specimens of the three groups were irradiated with a very long pulse mode (VLP) of 2.94 µm Er-YAG laser with 100 mJ pulse energy and energy density of 8.42 J/ c m 2 for 30 s, at a repetition rate of 15 Hz. The organic and inorganic content of the samples were investigated by Fourier Transforms Infrared spectroscopy (FTIR). The morphological characteristics were investigated with scanning electron microscopy (SEM) and elemental analysis (calcium and phosphorus) with energy-dispersive X-ray spectroscopy (EDX). FTIR data were analyzed with a One-Way ANCOVA test and EDX data with the independent sample t-test. Following the laser radiation, FTIR showed a significant decrease in the organic content of all tissues. The weight percentage (wt %) calcium content of dentin and bone increased significantly following irradiation with a p-value of .002 for both tissues, but the wt % of phosphorus content was not influenced significantly. The morphological alterations expressed signs of fusion in all the samples.

A comparative evaluation of APF gel, CPP/ACP paste alone and in combination with carbon dioxide laser on human enamel resistance to acid solubility using atomic absorption spectrometry: an in-vitro study.

BACKGROUND: The aim of this study was to compare the effects of acidulated phosphate fluoride (APF) gel, calcium phosphopeptide-amorphous calcium phosphate (CPP/ACP) paste alone and in combination with CO2 laser on the resistance of enamel to acid solubility. METHODS: Ninety enamel sections were obtained from 15 extracted teeth and were randomly assigned to six groups: 1) control group; 2) APF group; 3) CPP-ACP group; 4) CO2 laser group; 5) APF + CO2 group; and 6) CPP-ACP + CO2 group. The specimens were individually demineralized in 0.1 M lactic acid solution with adjusted pH of 4.8 for 24h at 37 ºC. The acid solubility was determined using atomic absorption spectrometry. Statistical analysis was done using one-way ANOVA and Tukey-Kramer post hoc test (P<0.05). RESULTS: The average extent of calcium ion released (ppm) was estimated as follow: group 1: 6.974±1.757, group 2: 5.363±1.383, group 3: 6.962±1.489, group 4: 6.890±1.560, group 5: 4.803±1.080 and group 6: 6.789±1.218. Based on the between-group comparison results, group 2 and group 5 showed significant differences with the other groups. CONCLUSIONS: Under the studied conditions, only, the APF group alone and in combination with CO2 laser could decrease enamel acid solubility.

Effects of Er:YAG Laser Treatment on the Mineral Content and Morphology of Primary Tooth Enamel.

Objective: The aim of this study was to evaluate the mineral content and morphology of primary tooth enamel prepared using an Er:YAG laser at different power settings. Materials and methods: The buccal surfaces of 45 noncarious primary molars were assessed in this study. The surfaces were cleaned and the teeth were randomly divided into nine groups (n = 5 each) to evaluate the effects of Er:YAG laser treatment at different energy levels: 200 mJ, 2 Hz; 200 mJ, 3 Hz; 200 mJ, 10 Hz; 250 mJ, 2 Hz; 250 mJ, 3 Hz; 250 mJ, 10 Hz; 300 mJ, 2 Hz; 300 mJ, 3 Hz; and 300 mJ, 10 Hz. The mean percentage weight (wt%) of calcium (Ca), phosphorous (P), fluoride (F), magnesium (Mg), potassium (K), and sodium (Na) in the primary tooth enamel was calculated for each group using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy before and after laser application. The enamel morphology was also evaluated using SEM. The obtained data were statistically analyzed by one-way analysis of variance and Tukey's honest significant difference test. Results: The mean wt% of Ca, P, and F in the enamel exhibited a significant change after laser treatment (p < 0.05); the wt% of Mg, K, and Na remained unchanged (p > 0.05). There was no association between the power setting of the laser and changes in the wt% of minerals in the enamel (p > 0.05). SEM showed that enamel irradiated at different energy levels exhibited a characteristic lava flow appearance, and more surface irregularities were observed with the 250-mJ setting than with the 200-mJ setting. Conclusions: Our findings suggest that the mineral content and morphology of the enamel of primary teeth are affected by Er:YAG laser irradiation.

Bond Strength of Abraded and Non-Abraded Bleached Enamel to Resin After Er,Cr:YSGG Laser Irradiation.

OBJECTIVE: The objective of the study was to evaluate the microtensile bond strength (µTBS) of a composite resin to abraded or non-abraded bleached enamel after Er,Cr:YSGG laser irradiation and to observe the fracture patterns of the tested interfaces. MATERIALS AND METHODS: Two hundred twenty-eight bovine incisors were sectioned, resulting in 228 enamel blocks (7 × 4 × 4 mm3) that were divided into 12 groups (n = 19) according to the factors "adhesion" after bleaching (immediate adhesion; after 14 days; and a control group with adhesion on unbleached teeth); enamel "abrasion" (with or without abrasion simulating cavity preparation); and "laser" (with or without Er,Cr:YSGG laser irradiation). Bleached enamel groups were treated with 20% carbamide peroxide, 8 h/day for 21 days. Abrasion was performed with silicon carbide sandpaper. Specimens were restored with adhesive system and a composite resin (Adper Single Bond 2 and Z250; 3M ESPE). After 7 days, specimens were prepared by cutting into 1 mm beans to µTBS test performed in a universal testing machine. Fracture mode analysis was performed by using a stereoscopic loupe. The µTBS data were statistically analyzed by three-way analysis of variance with 95% confidence level and compared by running a Tukey post hoc test (α = 0.05). RESULTS: There was no statistically significant difference between triple interaction and double interactions among factors. There was no significant difference between the factors "adhesion," "abrasion," and "laser." Laser irradiation produced significantly lower bond strength values in irradiated groups compared with the non-irradiated ones. All groups had a high percentage of adhesive failures. CONCLUSIONS: Abrasion provided no benefit to bond strength of composite resins to bleached enamel. Er,Cr:YSGG (20 Hz, 0.5 W, 3.97 J/cm2) treatment reduced the bond strength of composite resins to enamel.

Effect of Nd:YAG and CO2 Laser Irradiation on Prevention of Enamel Demineralization in Orthodontics: In Vitro Study.

OBJECTIVE: The aim of this study was to investigate Nd:YAG and CO2 laser effects in the prevention of demineralization in deeper layers of enamel via successive acid challenge cycles. BACKGROUND DATA: Lasers are promising in the prevention of enamel demineralization around the orthodontic brackets; however, there are very few studies that evaluate if the effects of treatment could be extended after successive acid challenge cycles due to permanent enamel structural alterations. MATERIALS AND METHODS: Human enamel samples were divided into five groups (n = 12): G1-application of 1.23% acidulated fluoride phosphate gel (AFP, control); G2-Nd:YAG laser irradiation (0.6 W, 84.9 J/cm2, 10 Hz, 110 µs, contact mode); G3-Nd:YAG laser irradiation associated with AFP; G4-CO2 laser irradiation (0.5 W, 28.6 J/cm2, 50 Hz, 5 µs, and 10 mm focal distance); and G5-CO2 laser irradiation associated with AFP. The samples were submitted to successive acid challenge cycles. Quantitative light-induced fluorescence and scanning electron microscopy were used to assess enamel demineralization. The data were statistically compared (α = 5%). RESULTS: G1: 50.87 ± 4.57; G2: 47.72 ± 2.87; G3: 50.96 ± 4.01; G4: 28.21 ± 2.19; and G5: 30.13 ± 6.38. The CO2 laser groups had significantly lower mineral losses than those observed in all other groups after successive acid challenge cycles. CONCLUSIONS: Only the CO2 laser (10.6 µm) irradiation prevents enamel demineralization around the orthodontic brackets even after exposure to successive acid challenges. The CO2 laser at 10.6 µm showed a deeper effect in enamel regarding caries prevention.

Sub ablative Er: YAG laser irradiation on surface roughness of eroded dental enamel.

OBJECTIVE: This study evaluated the effects of Er:YAG laser irradiation applied at varying pulse repetition rate on the surface roughness of eroded enamel. METHODS: Bovine enamel slabs (n = 10) were embedded in polyester resin, ground, and polished. To erosive challenges, specimens were immersed two times per day in 20mL of concentrated orange juice (pH = 3.84) under agitation, during a two-day period. Specimens were randomly assigned to irradiation with the Er:YAG laser (focused mode, pulse energy of 60 mJ and energy density of 3.79 J/cm(2) ) operating at 1, 2, 3, or 4 Hz. The control group was left nonirradiated. Surface roughness measurements were recorded post erosion-like formation and further erosive episodes by a profilometer and observed through atomic force microscopy (AFM). RESULTS: Analysis of variance revealed that the control group showed the lowest surface roughness, while laser-irradiated substrates did not differ from each other following post erosion-like lesion formation. According to analysis of covariance, at further erosive episodes, the control group demonstrated lower surface roughness (P > 0.05), than any of the irradiated groups (P < 0.05). CONCLUSIONS: The pulse repetition rate of the Er:YAG laser did not affect roughness of dental enamel eroded. The AFM images showed that the specimens irradiated by the Er:YAG laser at 1 Hz presented a less rough surface than those irradiated at 2, 3, and 4 Hz.

Evaluation of pH Levels and Surface Roughness After Bleaching and Abrasion Tests of Eight Commercial Products.

OBJECTIVE: This in vitro study evaluated the effect of different bleaching protocols and the variation of pH levels of bleaching gels regarding roughness and wear of bovine enamel, after in-office bleaching protocols and brushing. MATERIALS AND METHODS: Ninety fragments were randomly divided into nine groups: C, control; WHP15, 35% hydrogen peroxide (HP) (Whiteness HP, FGM) three gel applications of 15 min each, three sessions with 1 week intervals; WHP45, 35% HP (Whiteness HP) one application/45 min, three sessions with 1 week intervals; LPS, 35% HP (Lase Peroxide, DMC) plus hybrid light (HL) [light-emitting diode (LED)/diode laser], four applications/7 min 30 sec (6 min of HL activation), one session; LPSII, 25% HP (Lase Peroxide II, DMC) plus HL, four applications/7 min 30 sec (6 min of HL activation), one session; LPL, 15% HP (Lase Peroxide Light, DMC) four applications/7 min 30 sec (6 min of HL activation), one session; WO, 35% HP (Whitegold Office, Dentsply) three applications/15 min, three sessions with 1 week intervals; WBC40, 35% HP (Whiteness HP Blue Calcium, FGM) one application/40 min, three sessions with 1 week intervals; and WBC50, 20% HP (Whiteness HP Blue Calcium) one application/50 min, three sessions with 1 week intervals. The median pH values were determined utilizing a pH meter during the initial and final gel applications. A rugosimeter was utilized to evaluate the surface roughness (Ra) before and after bleaching and brushing (100,000 strokes), and the surface wear after brushing. RESULTS: For the results of the pH values, there was a decrease in the pH levels from the initial to the final bleaching time, except for the WBC50. The WO and WBC40 groups exhibited higher pH values. For the results of roughness and wear, there was an increase in surface roughness and wear among the groups. CONCLUSIONS: The pH values tended to decrease from the initial to the final bleaching. After tooth brushing, bleaching procedures with lower pH products provided a significant increase in enamel wear and surface roughness.

Effects of Bleaching Agents Combined with Regular and Whitening Toothpastes on Surface Roughness and Mineral Content of Enamel.

OBJECTIVE: The purpose of this study was to evaluate surface roughness and changes in the composition of enamel submitted to different bleaching protocols and toothbrushing with regular and whitening toothpastes. BACKGROUND DATA: Bleaching treatment could promote morphological and chemical changes in enamel surface. METHODS: Enamel blocks were randomized into nine groups (n=10) according to the bleaching treatment (no bleaching, control group; 6% hydrogen peroxide, HP; or 10% carbamide peroxide, CP) and toothpaste used (placebo, PL; regular, R; or whitening dentifrice, W). Bleaching was performed according to manufacturers' instructions and all groups were submitted to 30,000 cycles of simulated toothbrushing with toothpaste (PL, R, or W). Mineral content evaluation and enamel roughness were evaluated initially (T1), after bleaching (T2), and after toothbrushing (T3), using an energy-dispersive micro X-ray fluorescence spectrometer and profilometry, respectively. Data were statistically analyzed with two way ANOVA, Tukey, and Dunnett tests (5%). RESULTS: Enamel surface roughness was influenced by bleaching and toothbrushing. Surface roughness increased for the groups that brushed with the placebo dentifrice (CP+PL, HP+PL, C+PL) and for the control group that brushed with whitening dentifrice (C+W). Enamel Ca/P ratio decreased after bleaching, but toothbrushing, regardless of the dentifrice used, did not reduce the enamel mineral content. CONCLUSIONS: The bleaching treatment resulted in a decrease of enamel mineral content, but the studied dentifrices did not contribute to surface mineral loss.

Chemical and Morphological Changes of Primary Teeth Irradiated with Nd:YAG Laser: An Ex Vivo Long-Term Analysis.

OBJECTIVE: The aim of this study was to assess any long-term chemical and morphological Nd:YAG laser modifications on irradiated primary enamel. BACKGROUND DATA: Previous studies on irradiated primary human enamel employed methodologies that evaluated the short-term effects only. METHODS: One hundred and eighty-six irradiated (with and/or without fluoride) primary enamel teeth from high-caries-risk children, which were exfoliated over a 1-year period, were collected, and the sample surface area was submitted for scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray energy-dispersive spectrometry (EDS). The subsurface was analyzed by Knoop microhardness and light microscopy (LM). Data were analyzed by one way ANOVA and Tukey tests (α=0.05) and Kruskall-Wallis and Tukey tests (α=0.05). RESULTS: FTIR analysis revealed a higher concentration of phosphate and carbonate in the irradiated (0.987±0.064) and lower concentration in the control groups (1.477±0.310). SEM analysis showed that the control samples exhibited a slightly smoother surface than the irradiated groups. The EDS analysis did not show any differences in the amount of calcium, phosphorus, or fluoride among the groups. The microhardness analysis revealed that sealant (249.86±7.15) and laser irradiation (262.44±22.69) led to higher hardness values than the negative control group (128.35±25.19). LM indicated significantly reduced caries formation in the laser (5.35±5.38%) and the laser plus acidulated phosphate fluoride (APF) groups (10.35±0.88%) compared with the negative control group (72.56±12.86%). CONCLUSIONS: Even with the limitations of the present study, these results suggest that Nd:YAG irradiation clinically modified the chemical composition of the enamel surface regardless of fluoride concentration, which successfully inhibited demineralization of primary tooth enamel over a 1-year period without significant morphological changes.

Insight in the chemistry of laser-activated dental bleaching.

The use of optical radiation for the activation of bleaching products has not yet been completely elucidated. Laser light is suggested to enhance the oxidizing effect of hydrogen peroxide. Different methods of enhancing hydrogen peroxide based bleaching are possible. They can be classified into six groups: alkaline pH environment, thermal enhancement and photothermal effect, photooxidation effect and direct photobleaching, photolysis effect and photodissociation, Fenton reaction and photocatalysis, and photodynamic effect.

Comparison of Nd:YAG and diode laser irradiation during intracoronal bleaching with sodium perborate: color and Raman spectroscopy analysis.

OBJECTIVE: The aim of this study was to evaluate the color and enamel structure changes after intracoronal bleaching with sodium perborate under neodymium:yttrium-aluminum-garnet (Nd:YAG) and diode laser irradiation. BACKGROUND DATA: Although some studies investigated the efficacy of laser irradiation during intracoronal bleaching, no study has been conducted to investigate the changes in both color and enamel structure during intracoronal bleaching with laser irradiation. METHODS: Thirty-six extracted mandibular incisors were used. The root canals were prepared and filled with AH Plus and gutta-percha. Baseline color values and Raman spectra were obtained from all samples. The samples were randomly divided into three groups as follows: group 1, intracoronal bleaching with sodium perborate plus NdYAG laser irradiation; group 2, intracoronal bleaching with sodium perborate plus diode laser irradiation; and group 3, intracoronal bleaching with sodium perborate without any laser irradiation. Following the bleaching procedures, the final baseline color values and Raman spectra were obtained. The baseline and final values were statistically analyzed. Statistical analyses were performed with SPSS 18.0 software using Anova and the Kruskal-Wallis test. RESULTS: There was a significant difference between the Nd:YAG laser and control groups (p<0.05). There was no significant difference between the diode laser group and the control group, or the diode laser group and the Nd:YAG laser group. There was no significant difference among all groups in terms of Raman relative intensity (RRI) and fluorescence intensity (FI) percentage values (p>0.05). CONCLUSIONS: Laser application, especially Nd:YAG laser irradiation, was able to increase the efficacy of intracoronal bleaching with sodium perborate. Laser irradiation significantly increased the bleaching efficacy without any changes in the enamel surface structure.

In vitro assessment of the acid resistance of demineralized enamel irradiated with Er, Cr:YSGG and Nd:YAG lasers.

PURPOSE: This study's purpose was to evaluate the acid resistance of demineralized enamel irradiated with high-intensity lasers. METHODS: Enamel fragments were demineralized and treated as follows (N=10): Group 1-no treatment; Group 2-five percent sodium fluoride (NaF) varnish; Group 3-Er, Cr:YSGG laser (8.92 J/cm2, 0.5 W, 20 Hz, 30 seconds); Group 4-NaF and Er, Cr:YSGG laser; Group 5-Er, Cr:YSGG laser and NaF; Group 6-Nd:YAG laser (84.9 J/cm2, 0.5 W, 10 Hz, 30 seconds); Group 7-NaF and Nd:YAG laser; and Group 8-Nd:YAG laser and NaF. The samples were subjected to pH-cycling and assessed by microhardness (analysis of variance; α equals five percent) at different depths from the outer enamel surface. Samples were observed using polarized light microscopy (PLM) and scanning electron microscopy (SEM). RESULTS: There were no significant differences among the experimental groups in any of the subsurface layers evaluated. PLM observation revealed that the extent of demineralization of the irradiated samples was similar to the samples for Group 1 (control). SEM observation showed that irradiated surfaces were ablated and presented areas of melting. CONCLUSIONS: Laser irradiation, with or without applying five percent sodium fluoride, was not capable of increasing the enamel white spot lesions' acid resistance.

The combined use of Er,Cr:YSGG laser and fluoride to prevent root dentin demineralization.

UNLABELLED: The use of erbium lasers to prevent caries in enamel has shown positive results. However, it is not known if Er,Cr:YSGG laser can also be used to increase acid resistance of root dentine, which is another dental tissue susceptible to the action of cariogenic bacteria. OBJECTIVE: To analyze the effects of the Er,Cr:YSGG laser (λ=2.78 µm, 20 Hz) irradiation associated with 2% neutral sodium fluoride (NaF) to prevent root dentin demineralization. MATERIAL AND METHODS: One hundred human root dentin samples were divided into 10 groups (G) and treated as follows: G1: no treatment; G2: NaF; G3: laser (4.64 J/cm2) with water cooling (WC=5.4 mL/min); G4: laser (4.64 J/cm2) without WC; G5: laser (8.92 J/cm2) with WC; G6: laser (8.92 J/cm2) without WC; G7: laser (4.64 J/cm2) with WC and NaF; G8: laser (4.64 J/cm2) without WC and NaF; G9: laser (8.92 J/cm2) with WC and NaF; G10: laser (8.92 J/cm2) without WC and NaF. The NaF gel was applied alone or after 4 min of irradiation. After 14 days of acid challenge, the samples were sectioned and the Knoop microhardness (KHN) test was done at different depths (30, 60, 90 and 120 µm) from the outer dentin surface. Data were analyzed by one-way ANOVA and Fisher's test (α=5%). RESULTS: The results showed that G8 and G10 presented higher KHN than the G1 for the depths of 30 and 60 µm, indicating an increase of the acid resistance of the dentin in up to 35% (p<0.05). CONCLUSIONS: The use of Er,Cr:YSGG laser irradiation at 4.64 J/ cm2 and 8.92 J/cm2 without water cooling and associated with 2% NaF can increase the acid resistance of human root dentin.

Microhardness evaluation of enamel adjacent to an improved GIC sealant after different enamel pre-treatment procedures.

AIM: This in vitro study was carried out to evaluate the microhardness of enamel adjacent to a glass ionomer cement (GIC) with high fluoride content used as a sealant (Fuji Triage, GC Corp., Japan) after laser, bur or air abrasion treatment procedures. STUDY DESIGN: 200 freshly extracted non-carious human molars were divided into 10 experimental groups according to the enamel pre-treatment method: A air abrasion (Mach 4.1 Kreativ Inc., USA); AP, Air abrasion + conditioning with 20% polyacrylic acid (GC cavity conditioner); L, Er,Cr:YSGG laser application (Waterlase, Biolase Technology, Inc., San Clemente, USA); LP, Er,Cr:YSGG laser application and fissure conditioning; B, ameloplasty carried out with a diamond bur especially designed for preparing fissures (Komet #8833); BP, ameloplasty + fissure conditioning; P, application of 20% polyacrylic acid and all fissures sealed with GIC; C, no fissure treatment, the material was applied directly to the fissures (control); R, application of 37% orthophosphoric acid and fissures sealed with a resin-based sealant (Fissurit; Voco, Germany) (control); N, no treatment (control). Half of each group of teeth were left in artificial saliva for one month and the rest for three months. The teeth were then sectioned and microhardness was measured using a Vickers test apparatus. Kruskal-Wallis, Mann-Whitney U and Dunn's multiple comparison tests were carried out (5% significance). RESULTS: After one month results regarding hardness at the base and lateral walls of fissures were significantly higher in groups A, AP, L, LP, B, BP, P and C than in groups R and N (p<0.01), but no difference was seen between the treatment procedures. The results after three months produced similar findings with evenly increased values for all groups. CONCLUSION: The results of this study showed that the tested GIC with a higher fluoride content seemed to improve the enamel hardness of the fissure enamel and could be regarded as an alternative material in cases where resin sealant applications are questionable.

The combined use of Er, Cr: YSGG laser and fluoride to prevent root dentin demineralization

The use of erbium lasers to prevent caries in enamel has shown positive results. However, it is not known if Er,Cr:YSGG laser can also be used to increase acid resistance of root dentine, which is another dental tissue susceptible to the action of cariogenic bacteria. Objective: To analyze the effects of the Er,Cr:YSGG laser (λ=2.78 μm, 20 Hz) irradiation associated with 2% neutral sodium fluoride (NaF) to prevent root dentin demineralization. Material and Methods: One hundred human root dentin samples were divided into 10 groups (G) and treated as follows: G1: no treatment; G2: NaF; G3: laser (4.64 J/cm2) with water cooling (WC=5.4 mL/min); G4: laser (4.64 J/cm2) without WC; G5: laser (8.92 J/cm2) with WC; G6: laser (8.92 J/cm2) without WC; G7: laser (4.64 J/cm2) with WC and NaF; G8: laser (4.64 J/cm2) without WC and NaF; G9: laser (8.92 J/cm2) with WC and NaF; G10: laser (8.92 J/cm2) without WC and NaF. The NaF gel was applied alone or after 4 min of irradiation. After 14 days of acid challenge, the samples were sectioned and the Knoop microhardness (KHN) test was done at different depths (30, 60, 90 and 120 μm) from the outer dentin surface. Data were analyzed by one-way ANOVA and Fisher’s test (α=5%). Results: The results showed that G8 and G10 presented higher KHN than the G1 for the depths of 30 and 60 μm, indicating an increase of the acid resistance of the dentin in up to 35% (p<0.05). Conclusions: The use of Er,Cr:YSGG laser irradiation at 4.64 J/ cm2 and 8.92 J/cm2 without water cooling and associated with 2% NaF can increase the acid resistance of human root dentin. .

Light-activated bleaching: effects on surface mineral change on enamel.

AIM: This study evaluated the in vitro effect of 35% hydrogen peroxide (HP) on surface enamel change when activated with different light curing units (LCUs). MATERIALS AND METHODS: Enamel blocks (4 × 4 × 2 mm) were obtained from bovine incisors. The initial microhardness of the enamel was determined for each specimen. After this enamel blocks were randomly divided into four groups (n = 10) and treated as follows: Control, no bleaching procedure performed; HP - LCU, application of 35% HP gel without light activation; HP + QTH, application of 35% HP gel and light activation with a Quartz Tungsten-Halogen (QTH); and HP + Light Emitting Diode, application of 35% HP gel and light-activation with a LED. New microhardness measurements were obtained, immediately, 7 and 14 days after treatment. The percentage of surface mineral change was calculated according to the baseline and post-treatment microhardness values. Additionally, six samples from each group were randomly selected and prepared for scanning electron microscopy (SEM) characterization. The data were analyzed using an analysis of variance (ANOVA) to detect differences between the three time periods, and an ANOVA and Tukey's test with a confidence level of 95%. RESULTS: There was no significant difference between the initial hardness values and hardness values after treatment in any of the groups or time periods (p > 0.05). No major surface alterations were detected with SEM when comparing control groups to those undergoing bleaching treatments. CONCLUSION: The use of 35% HP in combination to QTH or LED light curing units LCU does not have detrimental effect on the enamel surface topography or in the mineral content, when compared with unbleached enamel or enamel submitted to 35% HP treatment alone.