Rosalía Contreras-Bulnes

Morphological and Structural Changes on Human Dental Enamel After Er:YAG Laser Irradiation: AFM, SEM, and EDS Evaluation

OBJECTIVE The purpose of this study was to evaluate, using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), the morphological and structural changes of the enamel after irradiation with the Er:YAG laser. BACKGROUND DATA A previous study showed that subablative Er:YAG laser irradiation produced undesirable morphological changes on the enamel surface, such as craters and cracks; however, the enamel acid resistance was not increased. METHODS Fifty-two samples of human enamel were divided into four groups (n = 13): Group I was the control (no laser irradiation), whereas Groups II, III, and IV were irradiated with the Er:YAG 100 mJ (12.7 J/cm(2)), 100 mJ (7.5 J/cm(2)), and 150 mJ (11 J/cm(2)), respectively, at 10 Hz with water spray. The morphological changes were observed by AFM and SEM. The weight percentages (wt%) of calcium (Ca), phosphorus (P), oxygen (O) and chlorine (Cl) were determined in the resultant craters and their periphery using EDS. Kruskal-Wallis and Mann-Whitney U tests were performed (p ≤ 0.05) to distinguish significant differences among the groups. RESULTS The AFM images showed cracks with depths between 250 nm and 750 nm for Groups II and IV, respectively, and the widths of these cracks were 5.37 μm and 2.58 μm. The interior of the cracks showed a rough surface. The SEM micrographs revealed morphological changes. Significant differences were detected in Ca, P, and Cl in the crater and its periphery. CONCLUSIONS AFM observations showed triangular-shaped cracks, whereas craters and cracks were evident by SEM in all irradiated samples. It was not possible to establish a characteristic chemical pattern in the craters.

Mechanical, antibacterial and bond strength properties of nano-titanium-enriched glass ionomer cement

The use of nanoparticles (NPs) has become a significant area of research in Dentistry. Objective The aim of this study was to investigate the physical, antibacterial activity and bond strength properties of conventional base, core build and restorative of glass ionomer cement (GIC) compared to GIC supplemented with titanium dioxide (TiO2) nanopowder at 3% and 5% (w/w). Material and Methods Vickers microhardness was estimated with diamond indenter. Compressive and flexural strengths were analyzed in a universal testing machine. Specimens were bonded to enamel and dentine, and tested for shear bond strength in a universal testing machine. Specimens were incubated with S. mutans suspension for evaluating antibacterial activity. Surface analysis of restorative conventional and modified GIC was performed with SEM and EDS. The analyses were carried out with Kolmogorov-Smirnov, ANOVA (post-hoc), Tukey test, Kruskal-Wallis, and Mann Whitney. Results Conventional GIC and GIC modified with TiO2 nanopowder for the base/liner cement and core build showed no differences for mechanical, antibacterial, and shear bond properties (p>0.05). In contrast, the supplementation of TiO2 NPs to restorative GIC significantly improved Vickers microhardness (p<0.05), flexural and compressive strength (p<0.05), and antibacterial activity (p<0.001), without interfering with adhesion to enamel and dentin. Conclusion GIC supplemented with TiO2 NPs (FX-II) is a promising material for restoration because of its potential antibacterial activity and durable restoration to withstand the mastication force.

Alteration of metabolomic profiles by titanium dioxide nanoparticles in human gingivitis model

Although nanoparticles (NPs) has afforded considerable benefits in various fields of sciences, several reports have shown their harmful effects, suggesting the necessity of adequate risk assessment. To clarify the mechanism of titanium dioxide nanoparticles (TiO2 NPs)-enhanced gingival inflammation, we conducted the full-scale metabolomic analyses of human gingival fibroblast cells treated with IL-1β alone or in combination with TiO2 NPs. Observation with transmission electron microscope demonstrated the incorporation of TiO2 NPs into vacuoles of the cells. TiO2 NPs significantly enhanced the IL-1β-induced prostaglandin E2 production and COX-1 and COX-2 protein expression. IL-1β reduced the intracellular concentrations of overall primary metabolites especially those of amino acid, urea cycle, polyamine, S-adenosylmethione and glutathione synthetic pathways. The addition of TiO2 NPs further augmented these IL-1β-induced metabolic changes, recommending careful use of dental materials containing TiO2 NPs towards patients with gingivitis or periodontitis. The impact of the present study is to identify the molecular targets of TiO2 NPs for the future establishment of new metabolic markers and therapeutic strategy of gingival inflammation.

Acid resistance and structural changes of human dental enamel treated with Er:YAG laser.

OBJECTIVE The purpose of this study was to evaluate the acid resistance and structural changes in the enamel surface of permanent teeth after subablative Er:YAG laser irradiation in vitro. BACKGROUND DATA Er:YAG irradiation laser is expected to enhance acid resistance and to produce morphological changes on the enamel surface. METHODS One hundred twenty samples of human enamel were divided into four groups (n = 30): Group I was the control (no laser irradiation), and Groups II, III, and IV were irradiated with Er:YAG laser at 100 mJ (12.7 J/cm(2)), 100 mJ (7.5 J/cm(2)), and 150 mJ (11 J/cm(2)), respectively, at 10 Hz and with water spray. The samples were placed in an acid solution, and the released calcium was quantified by atomic absorption spectrometry. The weight percentages of calcium, phosphorus, oxygen, and chlorine on the enamel surface were determined by energy dispersive X-ray spectroscopy. The morphological changes were observed by scanning electron microscopy. One-way ANOVA and Kruskal-Wallis tests were performed (p <or= 0.05) to distinguish significant differences among groups. RESULTS The weight percentage of calcium in the samples obtained from EDS and the amount of calcium in the solution did not show any significant difference. All irradiated samples showed morphological changes on the enamel surface compared to the control group. CONCLUSIONS The results of this study suggest that acid resistance of enamel due to subablative Er:YAG laser irradiation on the samples did not increase as expected. Morphological microscopic changes included craters and cracks on the irradiated zones.

Color differences: Polymerized composite and corresponding Vitapan Classical shade tab

OBJECTIVES This study compared newer composite resin restorative materials to the Vitapan Classical tabs they purported to represent. METHODS Five Vitapan Classical tabs were studied: A3.5, B2, C1, C3, and D2 (n=3). These tabs created a variety of levels of lightness, chroma and hue. Each of these five shade tabs was removed from three different shade guides, and an intraoral spectrophotometer was used to capture CIELAB color coordinates. Three separate readings were made and all nine were averaged. The inter-tab color differences were also calculated. Five specimens approximately 4.0mm thick were fabricated for each of the shades studied using five different composite resin materials. Composite specimens were of the same size and shape as target shade tabs, and three separate recordings were made for each of them. This average was compared to five Vitapan Classical shade tabs to calculate the color differences using both CIELAB and CIEDE2000 color difference formulas. Color differences were compared to thresholds for perceptibility and acceptability reported in other studies. RESULTS CIELAB and CIEDE2000 color differences ranged from 3.9 to 22.8 and from 2.1 to 13.8, respectively. None of the materials proved, an acceptable CIELAB color match to any of the shades tested. CONCLUSION When various shade tabs of Vitapan Classical shade guides were compared with correspondent tabs made of direct restorative composites, no material/shade combination resulted in an acceptable mismatch relative to the used standard of acceptability. Therefore, evaluated resin composites exhibited poor match compared to target Vitapan Classical tabs.

Quantitative analysis of S. mutans and S. sobrinus cultivated independently and adhered to polished orthodontic composite resins

In Orthodontics, fixed appliances placed in the oral cavity are colonized by microorganisms. Objective The purpose of this study was to quantitatively determine the independent bacterial colonization of S. mutans and S. sobrinus in orthodontic composite resins. Material and methods Seven orthodontic composite adhesives for bonding brackets were selected and classified into 14 groups; (GIm, GIs) Enlight, (GIIm, GIIs) Grengloo, (GIIIm, GIIIs) Kurasper F, (GIVm, GIVs) BeautyOrtho Bond, (GVm, GVs) Transbond CC, (GVIm, GVIs) Turbo Bond II, (GVIIm, GVIIs) Blugloo. 60 blocks of 4x4x1 mm of each orthodontic composite resin were made (total 420 blocks), and gently polished with sand-paper and ultrasonically cleaned. S. mutans and S. sobrinus were independently cultivated. For the quantitative analysis, a radioactive marker was used to codify the bacteria (3H) adhered to the surface of the materials. The blocks were submerged in a solution with microorganisms previously radiolabeled and separated (210 blocks for S. mutans and 210 blocks for S. sobrinus) for 2 hours at 37ºC. Next, the blocks were placed in a combustion system, to capture the residues and measure the radiation. The statistical analysis was calculated with the ANOVA test (Sheffè post-hoc). Results Significant differences of bacterial adhesion were found amongst the groups. In the GIm and GIs the significant lowest scores for both microorganisms were shown; in contrast, the values of GVII for both bacteria were significantly the highest. Conclusions This study showed that the orthodontic composite resin evaluated in the GIm and GIs, obtained the lowest adherence of S. mutans and S. sobrinus, which may reduce the enamel demineralization and the risk of white spot lesion formation.

Evaluation of self-etching adhesive and Er:YAG laser conditioning on the shear bond strength of orthodontic brackets.

The purpose of this study was to evaluate the shear bond strength, the adhesive remnant index scores, and etch surface of teeth prepared for orthodontic bracket bonding with self-etching primer and Er:YAG laser conditioning. One hundred and twenty bovine incisors were randomly divided into four groups. In Group I (Control), the teeth were conditioned with 35% phosphoric acid for 15 seconds. In Group II the teeth were conditioned with Transbond Plus SEP (5 sec); III and IV were irradiated with the Er:YAG 150 mJ (11.0 J/cm2), 150 mJ (19.1 J/cm2), respectively, at 7–12 Hz with water spray. After surface preparation, upper central incisor stainless steel brackets were bonded with Transbond Plus Color Change Adhesive. The teeth were stored in water at 37°C for 24 hours and shear bond strengths were measured, and adhesive remnant index (ARI) was determined. The conditioned surface was observed under a scanning electron microscope. One-way ANOVA and chi-square test were used. Group I showed the significantly highest values of bond strength with a mean value of 8.2 megapascals (MPa). The lesser amount of adhesive remnant was found in Group III. The results of this study suggest that Er:YAG laser irradiation could not be an option for enamel conditioning.

Chemical and morphological changes in human dentin after Er:YAGlaser irradiation: EDS and SEM analysis.

Sixty samples of human dentin were divided into six groups (n = 10) and were irradiated with Er:YAG laser at 100 mJ–19.9 J/cm2, 150 mJ–29.8 J/cm2, 100 mJ–35.3 J/cm2, 150 mJ–53.0 J/cm2, 200 mJ–70.7 J/cm2, and 250 mJ–88.5 J/cm2, respectively, at 7 Hz under a water spray. The atomic percentages of carbon, oxygen, magnesium, calcium, and phosphorus and the Ca‐to‐P molar ratio on the dentin were determined by energy dispersive X‐ray spectroscopy. The morphological changes were observed using scanning electron microscopy. A paired t‐test was used in statistical analysis before and after irradiation, and a one‐way ANOVA was performed (P ≤ 0.05). The atomic percent of C tended to decrease in all of the groups after irradiation with statistically significant differences, O and Mg increased with significant differences in all of the groups, and the Ca‐to‐P molar ratio increased in groups IV, V, and VI, with statistically significant differences between groups II and VI. All the irradiated samples showed morphological changes. Major changes in the chemical composition of dentin were observed in trace elements. A significant increase in the Ca‐to‐P ratio was observed in the higher energy density groups. Morphological changes included loss of smear layer with exposed dentinal tubules. The changes produced by the different energy densities employed could have clinical implications, additional studies are required to clarify them. Microsc. Res. Tech. 78:1019–1025, 2015.

Chemical Changes Associated with Increased Acid Resistance of Er:YAG Laser Irradiated Enamel

Background. An increase in the acid resistance of dental enamel, as well as morphological and structural changes produced by Er:YAG laser irradiation, has been reported. Purpose. To evaluate the chemical changes associated with acid resistance of enamel treated with Er:YAG laser. Methods. Forty-eight enamel samples were divided into 4 groups (n = 12). Group I (control); Groups II, III, and IV were irradiated with Er:YAG at 100 mJ (12.7 J/cm2), 200 mJ (25.5 J/cm2), and 300 mJ (38.2 J/cm2), respectively. Results. There were significant differences in composition of irradiated groups (with the exception of chlorine) and in the amount of calcium released. Conclusions. Chemical changes associated with an increase in acid resistance of enamel treated with Er:YAG laser showed a clear postirradiation pattern characterized by a decrease in C at.% and an increase in O, P, and Ca at.% and no changes in Cl at.%. An increased Ca/P ratio after Er:YAG laser irradiation was associated with the use of higher laser energy densities. Chemical changes produced by acid dissolution showed a similar trend among experimental groups. Stable or increased Ca/P ratio after acid dissolution was observed in the irradiated groups, with reduction of Ca released into the acid solution.

Influence of four systems for dental bleaching on the bond strength of orthodontic brackets.

OBJECTIVE To compare the influence of four systems for dental bleaching on the shear bond strength (SBS) of orthodontic brackets. MATERIALS AND METHODS One-hundred and fifty freshly extracted bovine teeth were randomly divided into five groups. In group I the teeth were untreated (control). In the remaining groups the teeth were bleached, as follows: group II: 38% hydrogen peroxide; group III: 10% carbamide peroxide; group IV: resin-based coating material (RBCM), Beauty Coat; and group V: RBCM, White Coat. In all groups the enamel was conditioned with a self-etching primer and brackets were bonded with composite resin. Samples were stored (37°C, 24 hours), tested, and statistically analyzed, with significance predetermined at P ≤ .05. The adhesive remnant index (ARI) was also evaluated and analyzed. RESULTS The SBS of group V (22.49 ± 5.34 MPa) was significantly higher than that of all other groups (I: 17.1 ± 5.11 MPa; II: 14.72 ± 5.42 MPa; III: 12.04 ± 5.29 MPa; and IV: 18.23 ± 5.58 MPa). In contrast, the SBS of group III was significantly lower than that of all groups (except group II). Significant differences in the ARI scores were present between groups. CONCLUSIONS The use of RBCM for dental bleaching before bonding orthodontic brackets did not reduce the SBS. In contrast, hydrogen and carbamide peroxides negatively affected the SBS. The SBS yielded after bleaching with carbamide peroxide was significantly lower.