Effect of Er,Cr:YSGG laser irradiation on bovine enamel surface during in-office tooth bleaching ex vivo

Effect of laser irradiation during in-office tooth bleaching on surface properties of resin-based restorative materials

This study evaluated the changes in surface properties of three resin-based restorative materials after two laser-assisted, in-office tooth bleaching protocols using erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) or diode (980 nm) lasers. A nanohybrid composite (Enamel Plus HRi), a Bis-GMA-free composite (Enamel Plus HRi Bio Function), and a resin-matrix CAD-CAM ceramic (Shofu Block HC) were tested. Forty specimens for each material were prepared and divided into four groups (n = 10/group). The control specimens did not undergo any bleaching treatment, whereas group 2 received bleaching with 40% hydrogen peroxide (H2O2), while groups 3 and 4 underwent the same bleaching procedure with the use of diode (980 nm) or Er,Cr:YSGG lasers, respectively. Surface microhardness and roughness measurements were conducted using a Vickers tester and an optical profilometer. Microhardness was lower in bleached specimens, with the nanohybrid composite exhibiting the largest difference from the no bleaching group. For the Bis-GMA-free composite the microhardness difference between no bleaching and laser-assisted bleaching were smaller than seen for the conventional bleaching technique. Surface roughness was higher in bleached specimens, with nanohybrid composite showing the largest differences from the control specimens. The examined laser-assisted tooth bleaching protocols were found not to impact surface microhardness and roughness of the tested resin-based specimens and they are deemed suitable for clinical use.

Effect of air-abrasion pretreatment with three desensitizing agents on efficacy of in-office tooth bleaching

OBJECTIVE

To evaluate the influence of air-abrasion of enamel with three different desensitizing powders on the whitening effect of a bleaching gel containing 40% H2O2, which was used for in-office tooth bleaching.

MATERIALS AND METHODS

Forty human incisors, extracted and prepared, were acquired for this study and subsequently randomized into four groups (n = 10). The control group specimens underwent no pretreatment prior to the bleaching procedure, whereas the remaining three groups underwent air abrasion using distinct desensitizing powders; (a) Sylc, which contains bioglass 45S5; (b) BioMinF, which contains calcium phospho-fluoro-silicate glass; and (c) MI Pearls, which contains nano-hydroxyapatite, 1 h preceding the Opalescence Boost PF 40% bleaching procedure. Color measurements were conducted using a double-beam UV-Vis spectrophotometer at four distinct time points (prior to bleaching, 24 h, 15 days, and 30 days post-bleaching).

RESULTS

Tooth color change outcomes revealed that there were no statistically significant results with respect to the interaction of the two criteria (treatments and time) (p = 0.990). Additionally, there were no statistically significant results with respect to the main effects of treatments (p = 0.385), while there were statistically significant effects with respect to the time criterion (p = 0.013).

CONCLUSIONS

The use of the tested desensitizing powders prior the bleaching procedure did not affect the tooth color change induced by the tested bleaching agent.

CLINICAL SIGNIFICANCE

Tooth color change and whiteness are not affected by air-abrasion desensitizing treatments when applied prior to in-office bleaching procedures.

Exploring the efficacy of laser-assisted in-office tooth bleaching: A study on varied irradiation times and power settings utilizing a diode laser (445 nm)

The aim of this study was to evaluate the effectiveness of a laser-assisted in-office tooth bleaching treatment, employing a diode laser (445 nm) using different power and time settings. Two hundred human incisors were collected for evaluating tooth color change (ΔΕ00) and whiteness index in dentistry (ΔWID) following laser-assisted tooth bleaching treatment. The specimens were distributed into 25 groups (n = 8) according to laser output power (0.5-2 W) and duration of irradiation (10-60 s) that was applied. ΔΕ00 and ΔWID were evaluated using a spectrophotometer at three points of time (24 h, 1 week and 1 month after treatments). Three-way ANOVA revealed that power, duration of laser irradiation, and time of measurement after bleaching treatments significantly affected both ΔΕ00 and ΔWID(p < 0.05). Furthermore, laser irradiation increased ΔΕ00 and ΔWID at all applied powers compared to the control group (p < 0.05), but this increase was dependent on the duration of irradiation. Laser irradiation significantly increased ΔΕ00 when the duration of operation was 50-60 s at 0.5-1 W, while at 1.5-2 W was significantly increased when the duration was 30-60 s. ΔWID was significant higher in the laser groups compared to the control group at all powers, except for 0.5 W where it was significant higher when the duration was 50-60 s. The outcomes of the study can help in selecting the suitable power settings and duration of laser exposure to achieve the optimal whitening results while ensuring the safety of the tooth pulp.

Assessment of the effect of experimental gel of pregabalin associated with 35% hydrogen peroxide bleaching on bovine dental enamel: an in vitro study

To assess the effect of bleaching with gel of pregabalin associated with 35% hydrogen peroxide on the mechanical and chemical properties and ultramorphology of dental enamel. Thirty-six (36) specimens of bovine dental incisors were obtained and divided into three groups (n = 12), namely: CG = bleaching with 35% hydrogen peroxide; KFG = bleaching with 5% potassium nitrate and 2% sodium fluoride gel + 35% hydrogen peroxide; and PGG = bleaching with experimental gel of pregabalin + 35% hydrogen peroxide. The specimens were assessed with respect to Knoop microhardness, surface roughness, and colour change, before and after bleaching. They were also assessed using scanning electron microscopy and energy-dispersive spectroscopy after treatments. All groups exhibited an increase in surface roughness and a reduction in Knoop microhardness after the protocols. There was colour change in all groups, with no difference between them. In addition, there were changes in enamel morphology and non-significant loss of calcium and phosphorus. The experimental gel of pregabalin did not influence the action of 35% hydrogen peroxide, yielding results similar to those of the other groups assessed in all the parameters. Therefore, the gel of pregabalin can be an alternative for topical application on the surfaces of the teeth in association with bleaching treatments.

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

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

Changes in enamel hardness, wear resistance, surface texture, and surface crystal structure with glass ionomer cement containing BioUnion fillers

This study investigated the potential of BioUnion filler containing glass ionomer cement (GIC) to enhance the properties of enamel surrounding restorations, with a specific focus on the effect on hardness. The hardness of the bovine enamel immersed in the cement was measured using Vickers hardness numbers. Following sliding and impact wear simulations, the enamel facets were examined using confocal-laser-scanning microscopy and scanning-electron microscopy. Surface properties were further analyzed using energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD). A significant increase in Vickers hardness numbers was observed in the BioUnion filler GIC after 2 days. Furthermore, the mean depth of enamel facets treated with BioUnion filler GIC was significantly less than that of untreated facets. Characteristic XRD peaks indicating the presence of hydroxyapatite were also observed. Our findings imply that GIC with BioUnion fillers enhances the mechanical properties of the tooth surface adjacent to the cement.

Effect of tooth brushing simulation on the surface properties of various resin-matrix computer-aided design/computer-aided manufacturing ceramics

PURPOSE

The purpose was to investigate the alterations in surface properties of different resin-matrix CAD/CAM ceramics following tooth brushing simulation (TBS) and compare them with a direct resin composite and a glass ceramic CAD/CAM material.

MATERIALS AND METHODS

Four resin-based CAD/CAM restoratives (Brilliant Crios-BR, Lava™ Ultimate-LV, Grandio Blocs-GR and Shofu Block HC-SH), a leucite-reinforced glass ceramic (IPS Empress® CAD-EC) and a resin composite (Filtek™ Z250-FZ) for direct restorations were tested. In particular, surface loss, hardness, roughness and morphology were investigated utilizing confocal microscopy, scanning electron microscopy and nanoindentation tester. TBS was conducted for 4 × 15 min on the surface of the samples and then the changes in their surface properties were evaluated.

RESULTS

After TBS, all the experimental groups exhibited surface loss to different extent. FZ and BR presented the highest surface loss, while EC and GR the lowest (p < 0.05). Regarding surface roughness, all the tested materials exhibited increase after TBS (p < 0.05), except LV (p = 0.099). EC presented the lowest Sa values, while FZ and BR the highest (p < 0.05). Changes in surface morphology were in compliance with the results of surface roughness and also surface hardness was correlated with surface loss.

CONCLUSIONS

The tested resin-matrix CAD/CAM ceramic restorative materials showed a competent behavior against abrasive forces applied during TBS. Surface loss and roughness changes were material dependent and superior compared to a resin composite for direct restorations, while in comparison with a leucite-reinforced glass ceramic exhibited inferior properties.

CLINICAL SIGNIFICANCE

Tooth brushing affected differently the surface of the tested restorative materials. However, the abrasive wear that was induced was negligible. Clinical studies are necessary to ascertain if there is clinical significance of these surface alterations that may demand repair of such restorations.

Evaluation of the laser wavelength role on tooth bleaching in terms of color change, roughness, and microhardness with pulpal rapid temperature monitoring: an in vitro study

This in-vitro study evaluates the efficacy of the teeth bleaching approach using different laser wavelengths (405 nm blue diode, 940 nm infrared diode, and Er,Cr:YSGG 2780 nm lasers) in comparison to the conventional method using light-emitting diode (LED) sources (420-480) nm. Eighty caries-free sound human premolars were randomly divided into four groups (N=20). Each group received a different bleaching procedure. Then each group was further subdivided into two subgroups (N=10) stained with different solutions. The pulp chamber temperature rise was recorded using an optical fiber sensor with a novel design and fabrication. The color was analyzed using a digital spectrophotometer. Five samples of each subgroup were tested for surface roughness, while the others were tested for Vickers microhardness. The bleaching process with a short wavelength 405 nm blue diode laser showed the best results for the shade, with a minimum pulpal temperature increase indicating no possible necrosis and hence maintaining tooth vitality. Additionally, a remarkable reduction in bleaching time was achieved compared to the conventional approach. This process also yielded the highest color change (Δ E) and increased microhardness, with no noticeable change to the tooth roughness. The 405 nm blue diode laser applied for bleaching showed the best bleaching activity against tested stains and negligible pulpal temperature rise with a noticeable reduction in the bleaching time. The proposed novel method to measure temperature change could be used to develop a promising smart sensor for quick, effective, repeatable, and in-situ monitoring of human body temperature.

Can antioxidant treatment replace delay in bracket bonding? An in vitro study

BACKGROUND

Deterioration in shear bond strength has been reported after immediate bracket bonding following hydrogen peroxide bleaching. This study compared the effectiveness of three antioxidant agents, namely, alpha-tocopherol, green tea extract, and sodium ascorbate, in reversing the bleaching effect and as possible alternatives to delayed bonding.

METHODS

A total of 105 extracted human premolars were arbitrarily assigned to 7 groups (n = 15 each), including group 1 as the unbleached control group and six experimental groups, which were bleached with 40% hydrogen peroxide in three sessions of 15 min each. In experimental group 2, bonding was performed immediately after bleaching, whereas in groups 3 and 4, bonding was delayed for 1 and 2 weeks, respectively; meanwhile, the specimens were immersed in artificial saliva at 37 °C. Groups 5, 6, and 7 were treated immediately after bleaching with 10% of alpha-tocopherol, green tea extract, and sodium ascorbate solutions, respectively, for 15 min. Specimens were processed using 500 thermal cycles between 5 and 55 °C, with a dwell time of 30 s after 24 h of bracket bonding, and then tested for shear bond strength. The adhesive remnant index was examined to evaluate fracture mode. One-way analysis of variance, Kruskal-Wallis H, and post hoc Tukey's honestly significant difference tests were used to compare the data. Significant results were subjected to pairwise comparisons with Bonferroni's correction-adjusted of p values ≤ 0.050.

RESULTS

Shear bond strength was significantly lower (p < 0.001) in the immediate bonding and 1-week delay groups than in the control group. However, no significant difference was detected among the 2-week delay, antioxidant-treated, and control groups (p > 0.05).

CONCLUSIONS

Application of 10% alpha-tocopherol, green tea extract, or sodium ascorbate for 15 min could restore shear bond strength after 40% hydrogen peroxide bleaching as an alternative to delay in bracket bonding.

Microhardness change of human dental enamel due to power bleaching with different gels

AIM

Since the introduction of bleaching treatments in the office, different lights have been suggested to accelerate the bleaching reaction. This study aimed to evaluate the microhardness of tooth enamel after office bleaching using different materials.

Effect of a fiber-reinforcing technique for direct composite restorations of structurally compromised teeth on marginal microleakage

OBJECTIVES

To evaluate if the marginal microleakage of extensive Class I composite resin restorations can be affected by applying ultra-high-molecular-weight polyethylene (UHMWPE) fibers with the wallpapering technique combined with different restorative materials and methods.

MATERIALS AND METHODS

A 120 human molars were selected and one extensive Class I cavity was prepared on the occlusal surface of each tooth. The specimens were divided into 12 groups (n = 10) according to the type of restorative material (Filtek Z550, Beautifil II LS or Beautifil Bulk Restorative), the use or not of reinforcing fibers (ribbond) and the applied restorative technique (incremental or bulk). The specimens were subjected to thermocycling and then immersed into a 50 wt% silver nitrate solution following a dying protocol. Subsequently, the teeth were prepared for SEM observations to evaluate the extent of marginal microleakage.

RESULTS

Three-way ANOVA revealed that the type of material, the use of ribbond fibers and the type of restorative technique significantly affected marginal microleakage (p < 0.001). Application of ribbond fibers decreased marginal microleakage to all tested restorative materials, regardless of the restorative technique, in a range of 31.2-81.4%. In the groups with no-use of ribbond fibers, among the materials there were no significant differences in microleakage when the teeth were restored with the incremental technique (p > 0.05).

CONCLUSIONS

The use of UHMWPE fibers with wallpapering technique in Class I composite restorations may be an effective method to reduce marginal microleakage, regardless of the selected restorative technique or the material.

CLINICAL RELEVANCE

Clinicians may be encouraged to utilize reinforcing fiber restorative techniques for direct restorations of structurally compromised teeth as a valid alternative to indirect restorations.

Effects of Bleaching Associated with Er:YAG and Nd:YAG Laser on Enamel Structure and Bacterial Biofilm Formation

OBJECTIVE

To compare the effects of bleaching associated with Er:YAG and Nd:YAG laser on enamel structure and mixed biofilm formation on teeth surfaces.

MATERIALS AND METHODS

Sixty-eight enamel samples were randomly divided into four groups (n = 17), control, Opalescence Boost only, Opalescence Boost plus Er: YAG laser, and Opalescence Boost plus Nd:YAG laser. The structure was observed using SEM after bleaching. Subsequently, the treated enamel samples were also cultured in suspensions of Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, and Fusobacterium nucleatum (Fn) for 24 and 48 h. Biofilm formation was quantified by crystal violet staining, and the structure was visualized by confocal laser scanning microscopy. The data were analyzed using the Kruskal-Wallis method.

RESULTS

The enamel structure significantly changed after bleaching. There was no obvious difference in the biofilm formation after 24 h; however, after 48 hours, the amount of biofilm increased significantly. Remarkably, the amount was significantly higher on enamel bleached only, however, there was no significant difference between samples bleached with Er:YAG or Nd:YAG laser compared to the control.

CONCLUSIONS

Bleaching only appeared to markedly promote biofilm formation after 48 h, and the biofilms on samples bleached with Er:YAG or Nd:YAG laser did not change significantly, showing that bleaching with Er:YAG or Nd:YAG laser can be safely applied in clinical practice.

Effects of tooth bleaching protocols assisted by Er,Cr:YSGG and diode (980 nm) lasers on color change of resin-based restoratives

OBJECTIVE

To evaluate color change of three resin-based restorative materials after two laser-assisted in-office tooth bleaching protocols using Er,Cr:YSGG and diode (980 nm) lasers.

MATERIALS AND METHODS

A nanohybrid composite resin (EP), a Bis-GMA free composite resin (EPBio) and a resin-matrix CAD-CAM ceramic (HC) were tested. Ninety specimens were prepared and stored in artificial saliva. Group 1 received an in-office bleaching treatment using 40% H₂ O_2. The same bleaching procedure was assisted by Er,Cr:YSGG laser in Group 2 and by a diode laser (980 nm) in Group 3. Color measurements were performed using a double-beam UV-Vis spectrophotometer at four time intervals (before, 24 h, 15 and 30 days), converted to L*, a*, and b* units of the CIELAB color space and assessed on the basis of 50:50% acceptability (ΔΕ_ab * = 2.7 and ΔΕ₀₀  = 1.77) and 50:50% perceptibility (ΔΕ_ab * = 1.2 and ΔΕ₀₀  = 0.81) thresholds. Three-way ANOVA with repeated measurements was used for statistical analysis of the data.

RESULTS

Color and whiteness changes did not exceed the established 50:50% acceptability thresholds. EP presented the highest color change after the bleaching followed by EPBio and HC (p ≤ 0.05). Three-way ANOVA revealed that type of material and time interval significantly affected color change (p ≤ 0.001).

CONCLUSIONS

The tested bleaching treatments assisted by Er,Cr:YSGG and diode (980 nm) lasers did not induce unacceptable color and whiteness changes in the resin-based restorative materials.

CLINICAL SIGNIFICANCE

The tested Er,Cr:YSGG and diode (980 nm) laser-assisted tooth bleaching protocols which may be recommended to accelerate the clinical procedures cannot affect the color of the existing resin-based restorations in case they are accidentally exposed on the bleaching gel and laser irradiation.

Evaluation of Monomer Elution and Surface Roughness of a Polymer-Infiltrated Ceramic Network CAD-CAM Material After Er,Cr:YSGG Laser-assisted Tooth Bleaching

PURPOSE

The aim of this in vitro study was to examine the effect of Er,Cr:YSGG laser-assisted tooth bleaching treatment on the elution of monomers and surface roughness of a hybrid computer-aided design-computer-aided manufacturing (CAD-CAM) material, and to compare it with a resin composite for direct restorations.

METHODS AND MATERIALS

Forty specimens of a hybrid CAD-CAM material (Enamic) and forty of a conventional resin composite (Tetric) were fabricated and randomly divided into four groups (n=10). Half of the specimens of each material were stored in distilled water and the other half in artificial saliva for 7 days. At the end of this period, the storage medium was analyzed by high-performance liquid chromatography (HPLC), and the surface roughness parameters of the specimens were evaluated by optical imaging noncontact interferometric profilometry. Afterwards, half of the specimens of each tested material received a conventional in-office tooth bleaching treatment and the other half an Er,Cr:YSGG laser-assisted bleaching treatment, and then they were again incubated in distilled water and artificial saliva for an additional 7-day time period. At the end of this period, the effect of the bleaching treatments on elution of monomers and surface roughness of the tested materials was evaluated.

RESULTS

Bisphenol A (BPA), urethane dimethacrylate (UDMA), triethylene glycol dimethacrylate (TEGDMA), and bisphenol A-glycidyl dimethacrylate (BisGMA) were eluted from the conventional resin composite into both the solutions tested. Only TEGDMA was eluted from the hybrid CAD-CAM material. However, no statistically significant differences were found among the surface roughness parameters of both materials. Both the conventional and Er,Cr:YSGG laser-assisted tooth bleaching treatments affected the monomer elution from the composite resin. However, there were no statistically significant differences (p<0.05) between the treatments.

CONCLUSIONS

According to the results of this study, tooth bleaching with Er,Cr:YSGG laser or conventional technique is safe, even if the bleaching agent comes in contact with hybrid CAD-CAM restorations.

Photoinactivation of Staphylococci with 405 nm Light in a Trachea Model with Saliva Substitute at 37 °C

The globally observed rise in bacterial resistance against antibiotics has increased the need for alternatives to antibiotic treatments. The most prominent and important pathogen bacteria are the ESKAPE pathogens, which include among others Staphylococcus aureus, Klebsiella pneumoniae and Acinetobacter baumannii. These species cause ventilator-associated pneumonia (VAP), which accounts for 24% of all nosocomial infections. In this study we tested the efficacy of photoinactivation with 405 nm violet light under conditions comparable to an intubated patient with artificial saliva for bacterial suspension at 37 °C. A technical trachea model was developed to investigate the visible light photoinactivation of Staphylococcus carnosus as a non-pathogen surrogate of the ESKAPE pathogen S. aureus (MRSA). The violet light was coupled into the tube with a fiber optic setup. The performed tests proved, that photoinactivation at 37 °C is more effective with a reduction of almost 3 log levels (99.8%) compared to 25 °C with a reduction of 1.2 log levels. The substitution of phosphate buffered saline (PBS) by artificial saliva solution slightly increased the efficiency during the experimental course. The increased efficiency might be caused by a less favorable environment for bacteria due to for example the ionic composition.

Effect of novel charcoal-containing whitening toothpaste and mouthwash on color change and surface morphology of enamel

Purpose:

The aim of this in vitro study was to investigate the effectiveness of a novel charcoal-containing whitening toothpaste and a mouthwash on tooth color change and the alterations of enamel that may be induced after toothbrushing, corresponding to a 90-day period.

Materials and Methods:

Forty human canines were used, stained with coffee, and divided into four groups (n = 10) as follows: Group 1 (control) submitted to toothbrushing with deionized water, Group 2 with a regular toothpaste, Group 3 with a whitening toothpaste (1% charcoal), and Group 4 with the same whitening toothpaste in combination with a mouthwash (1% charcoal and 0.5% H₂O₂). After the treatments, ΔΕ of the teeth was evaluated using an ultraviolet/Vis spectrophotometer, whereas the changes in surface morphology were observed by means of a confocal microscope.

Results:

The whitening toothpaste increased significantly ΔΕ (40.5%) compared to the control group (P < 0.001). In addition, the tested whitening toothpaste also increased ΔΕ (17.7%) compared to the regular toothpaste (P = 0.023). The whitening toothpaste presented smoother surfaces after toothbrushing, but more heterogeneous with numerous large craters, whereas the whitening mouthwash did not influence surface morphology changes.

Conclusions:

Charcoal-containing toothpastes may enhance the whitening of the teeth, but they should be used carefully due to changes that may induce on enamel. The patients should consult a dental professional for proper use. A charcoal-containing mouthwash in combination with whitening toothpastes probably cannot offer additional whitening effect.

Enhancing Stability and Tooth Bleaching Activity of Carbamide Peroxide by Electrospun Nanofibrous Film

Carbamide peroxide (CP) possesses a strong tooth bleaching activity, however, its clinical application is limited because of its instability in aqueous formulations. This study explores the improvement of CP stability and bleaching activity by loading CP in electrospun nanofibrous film (ENF). Polyvinylalcohol, polyvinylpyrrolidone, and silica were used as components for core-based nanofibers of ENF. Electrospinning feed aqueous solutions (EFASs) were developed for preparing CP loaded ENF (CP-ENF). Stability of CP in EFASs is significantly higher than in pure water. The highest stability of CP is found in PPS-CP3, composed of 0.5% CP, 5.5% polyvinylalcohol, 3% polyvinylpyrrolidone, and 1% silica. The results from X-ray diffraction indicate that CP is dispersed as a non-crystalline form in CP-ENFs. CP and the compositions of EFASs play a major role on characteristics and bleaching efficiency of CP-ENFs. Drug release of CP-ENFs is the first order kinetics. CP-ENF obtained from PPS-CP3 shows the highest drug entrapment efficiency, high adhesion, and suitable sustained release. Drug release mechanism is along with anomalous transport according to Korsmeyer-Peppas model. In an ex vivo study using human teeth, it shows the highest bleaching efficiency among the others. Therefore, CP-ENF obtained from PPS-CP3 is a promising ENF for clinical use.

Analysis of enamel structure and mineral density after different bleaching protocols using micro-computed tomography

OBJECTIVE

This study aims to investigate the effect of three different bleaching applications on structural integrity, mineral volume (MV) and density of the enamel by using micro-computed tomography (Micro-CT) and evaluate the colour effectiveness using CIEDE2000.

MATERIALS AND METHODS

Twenty-four maxillary premolar teeth were divided into three groups (n = 8) (group 1: 40% HP gel with erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser activation; group 2: 40% HP gel with diode laser activation; group 3: 16% CP gel). Bleaching protocols were applied and colour alteration was obtained. Data were calculated with CIEDE2000 before and after bleaching. A Micro-CT was used to scan the specimens before and after the bleaching application. Statistical analysis was performed by ANOVA.

RESULTS

No significant difference was observed between the groups for colour changes (p > .05). Micro-CT analysis showed significant differences in structural thickness, structural separation, mineral density and MV for the different ROIs before and after bleaching for all groups (p<.05).

CONCLUSIONS

All of the bleaching methods represented similar efficiency. However, bleaching with Er,Cr:YSGG laser was less harmful to enamel in comparison with other bleaching methods. The present results may be useful for establishing a numerical standard for the change in bleaching with laser systems in dental hard tissues.

Effect of air-abrasion pre-treatment with bioactive glass 45S5 on enamel surface loss after erosion/abrasion challenge

OBJECTIVES

The aim of this in vitro study was to evaluate the effect of air-abrasion surface pre-treatment with bioactive glass (BAG) 45S5 on enamel surface loss after erosion/abrasion challenge.

METHODS

Twenty-four sound bovine incisors were used for this study. Four experimental groups (n=12) were assigned as follows: Group 1 was the negative control group, Group 2 specimens were treated with a SnF₂ gel (positive control group), Group 3 specimens were air-abraded with BAG 45S5 (ProSylc) and Group 4 received both treatments. The specimens were submitted to erosion/abrasion challenge using a common soft drink. Enamel surface loss was evaluated using an optical profilometer. Additionally, surface roughness (VSI method) and surface microhardness (Vickers method) changes were evaluated, as well as SEM and EDS analyses were performed on enamel surface. The data were statistically analyzed using one-way ANOVA and Tukey's post-hoc test at a level of significance a=0.05.

RESULTS

Surface pre-treatment with BAG 45S5 reduced surface loss in comparison with negative control group (p<0.001), which exhibited the highest surface loss of the experimental groups (p<0.05). The positive control group (SnF₂ treatment) and Group 4 specimens, which received both air-abrasion pre-treatment and SnF₂ treatment, presented the lowest surface loss (p<0.05), but did not show significant differences to each other (p=0.65).

SIGNIFICANCE

Air-abrasion pre-treatment with BAG 45S5 may be beneficial as an in-office preventive method for the limitation of enamel erosive wear induced by excessive consumption of soft drinks. The clinical significance of the results regarding this preventive method should be confirmed by clinical studies.

Evaluation of a clinical preventive treatment using Er,Cr:YSGG (2780 nm) laser on the susceptibility of enamel to erosive challenge

The purpose of this in vitro study was to evaluate the effect of a clinical preventive treatment using Er,Cr:YSGG laser irradiation on bovine enamel susceptibility after erosive challenge. Twelve sound bovine incisors were used and twenty-four enamel specimens were prepared in total. Two experimental groups (n = 12) were assigned as follows: Group 1 was the control group and in Group 2, the enamel specimens were irradiated with an Er,Cr:YSGG (2780 nm) laser system for 20 s, with average output power of 0.25 W, pulse repetition rate at 20 Hz without water or air flow and the pulse duration was fixed at 140 μsec. The tip diameter was 600 μm, the tip to tissue distance was 1 mm, the speed of handpiece movement was 2 mm/s, the power density was 88.34 W/cm², and the fluence was 31.25 J/cm². The specimens were submitted to erosive challenge using a common soft drink. Surface microhardness changes, surface roughness changes, and surface loss were evaluated after erosive challenge. The data were statistically analyzed using one-way ANOVA and Tukey's post-hoc test at a level of significance a = 0.05. Er,Cr:YSGG laser-treated enamel exhibited significantly less decrease in surface microhardness and significant less surface loss compared to control enamel after the erosive challenge (p < 0.05). The experimental groups did not show significant differences in surface roughness increase after the erosive challenge (p > 0.05). Er,Cr:YSGG laser treatment may be promising for the limitation of enamel erosive tooth wear induced by excessive consumption of soft drinks. Clinical studies are needed to clarify whether this protective effect is clinically significant.

Blue-Light -Activated Nano-TiO2@PDA for Highly Effective and Nondestructive Tooth Whitening

The application of polydopamine (PDA)-modified titanium dioxide nanoparticles (nano-TiO₂@PDA) as a new blue-light-activated tooth whitening material was discussed for the first time. Compared with the classical clinical whitening agent (peroxide, hydrogen peroxide, and carbamide peroxide), nano-TiO₂@PDA-based treatment not only had a similar whitening effect but also showed remarkably less damage on the enamel structure. Essentially, a highly effective and nondestructive tooth whitening treatment could thus be realized accordingly. The toxicity and antibacterial properties of this material were also evaluated systematically.

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.

Efficacy of Er Cr: YSGG laser therapy at different frequency and power levels on bond integrity of composite to bleached enamel

The aim was to evaluate the influence of Er, Cr: YSGG laser therapy at different pulse frequency and power levels on the bond strength and microleakage of bleached enamel. One hundred samples were bleached using in-office whitening agent. Bleached samples were divided into six subgroups, four subgroups was based on laser application parameters (pulse frequency 50 and 30 Hz; Power 4.5 & 6 W) one subgroup was treated with bleach (B) and the other was control (no bleaching, no laser application). All specimens including control were etched with 37% phosphoric acid and composite build-ups were performed. Ten specimens from all the groups (B: Bleach only, L1: 50 Hz-4.5 W, L2: 50 Hz-6 W, L3: 30 Hz-4.5 W, L4:50 Hz-6W & C: Control) were assessed for shear bond strength and microleakage scores. Ten samples from all groups were immersed in 2% methylene blue for 24 h and assessed under a digital microscope for microleakage. The lowest mean bond strength was achieved in bleached group (9.49 ± 0.95) and maximum bond strength was observed in control group (33.97 ± 0.86). The highest mean microleakage score was found in bleached specimens (group B) (630.32 ± 156.58) and the lowest in controls (group C) (36.66 ± 27.33). Among assessed laser frequency and power combinations, 4.5 W and 30 Hz frequency showed maximum adhesive bond integrity (high bond strength and low microleakage) for bleached enamel samples.