Rogelio J. Scougall-Vilchis

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.

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.

Editor's Summary, Q & A, Reviewer's Critique

INTRODUCTION This study was conducted to compare the effects of 6 self-etching primers (SEPs) on the shear bond strength (SBS) of orthodontic brackets bonded with the same orthodontic composite resin. METHODS One hundred forty extracted premolars were randomly divided into 7 groups (20 per group). In group I (control), the enamel was etched with 37% phosphoric acid. In the other groups, it was conditioned with SEPs according to each manufacturers instructions: group II, Transbond Plus SEP (3M Unitek, Monrovia, Calif); group III, AdheSE (Ivoclar Vivadent AG, Schaan, Liechtenstein); group IV, Primers A and B (Shofu, Kyoto, Japan); group V, Clearfil Mega Bond FA (Kuraray Medical, Tokyo, Japan); group VI, Peak SE and Peak LC Bond (Ultradent Products, South Jordan, Utah); and group VII, Bond Force (Tokuyama, Osaka, Japan). All brackets were bonded with Transbond XT (3M Unitek), and the teeth were then stored (37 degrees C, 24 hours), tested, and statistically analyzed (Scheffé, ANOVA [P <0.05], and Weibull analyses). The adhesive remnant index (ARI) was also recorded. RESULTS Group I (26.5 +/- 8.1 MPa) had a significantly higher SBS value than the other groups except group II (21.1 +/- 6.2 MPa). There were no significant differences among groups II, V (19.0 +/- 4.3 MPa), VI (19.6 +/- 5.1 MPa), and VII (18.3 +/- 4.4 MPa). The values for groups I, II, and VI were significantly higher than for group III (13.4 +/- 4.1 MPa), and the value for group IV (8.8 +/- 2.6 MPa) was significantly lower than the values for groups I, II, V, VI, and VII. Significant differences were found in the ARI scores. CONCLUSIONS The SBS values of all groups might be clinically acceptable, and orthodontic brackets can be successfully bonded with Transbond XT after enamel conditioning with any of these SEPs. However, since the SEPs used in groups III and IV significantly affected the bond strength negatively, further studies are warranted to evaluate their effectiveness.

Biosynthesis of Silver Nanoparticles on Orthodontic Elastomeric Modules: Evaluation of Mechanical and Antibacterial Properties

In the present study, silver nanoparticles (AgNPs) were synthesized in situ on orthodontic elastomeric modules (OEM) using silver nitrate salts as metal-ion precursors and extract of the plant Hetheroteca inuloides (H. inuloides) as bioreductant via a simple and eco-friendly method. The synthesized AgNPs were characterized by UV-visible spectroscopy; scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The surface plasmon resonance peak found at 472 nm confirmed the formation of AgNPs. SEM and TEM images reveal that the particles are quasi-spherical. The EDS analysis of the AgNPs confirmed the presence of elemental silver. The antibacterial properties of OEM with AgNPs were evaluated against the clinical isolates Streptococcus mutans, Lactobacillus casei, Staphylococcus aureus and Escherichia coli using agar diffusion tests. The physical properties were evaluated by a universal testing machine. OEM with AgNPs had shown inhibition halos for all microorganisms in comparison with OEM control. Physical properties increased with respect to the control group. The results suggest the potential of the material to combat dental biofilm and in turn decrease the incidence of demineralization in dental enamel, ensuring their performance in patients with orthodontic treatment.

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.

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.

Influence of different self-etching primers on the bond strength of orthodontic lingual buttons

The aim of this study was to evaluate the influence of six self-etching primers (SEPs) on the shear/peel bond strength (SPBS) of orthodontic lingual buttons. A total of 150 extracted human premolars were randomly divided into six equal groups. In all groups, the lingual buttons were bonded with BeautyOrtho Bond and the enamel was conditioned with the following-group I (Control): Primers A & B; group II: Transbond Plus SEP; group III: Clearfil Mega Bond FA™; group IV: AdheSE; group V: Peak SE & Peak LC Bond; and group VI: Bond Force. The teeth were stored at 37°C for 24 hours and the SPBS was tested (0.5 mm/minute). The results were calculated in mega pascals (MPa) and statistically analysed [mean, standard deviation, Scheffè, analysis of variance (P < 0.05)]. The adhesive remnant index (ARI) was also evaluated and statistically analysed with a chi-square test. All groups demonstrated higher SPBS than the force suggested as necessary to accomplish orthodontic tooth movement, except group IV (7.7 ± 1.7 MPa), which showed a significantly lower value than groups I (10.7 ± 2.4 MPa), II (11.3 ± 3.1 MPa), and V (10.9 ± 2.8 MPa). The values of groups III (9.9 ± 1.6 MPa) and VI (10.5 ± 1.6 MPa) were comparable with those of groups I and V. Significant differences (P < 0.05) were found among the groups in ARI scores. The SPBS values of all groups could be clinically acceptable and lingual buttons might be successfully bonded with any of these SEPs except AdheSE since that conditioner significantly influenced bond strength. As the SPBS was lower in all groups than the value at which enamel fractures have been found, a sound enamel surface might be left after removal of lingual buttons.

Comparative study of fluoride released and recharged from conventional pit and fissure sealants versus surface prereacted glass ionomer technology.

Context: The fluoride release of sealants in vitro shows a marked decrease. Giomers are distinguishable from manufactured resin-based sealants and contain prereacted glass-ionomer particles (PRG). Aims: To compare the amounts of fluoride released from the main pit and fissure of a resin-based sealant with that from a Giomer and to assess the abilities of the sealant and the Giomer to recharge when exposed to regular use of fluoride rinse. Materials and Methods: The readings for the fluoride concentration were carried out for 60 days using a fluoride ion-specific electrode. After this period, the samples were recharged using a fluoride mouth rinse. The amount of fluoride released after this recharge was determined for 5 days. The data were analyzed using Student′s t- and analysis of variance tests. Results: In general, all materials presented higher fluoride release in the first 24 h; G1 and G4 showed a higher fluoride release in this period. On the other hand, G3 and G1 presented the most constant fluoride release until the 8 th day, wherein all the sealants considerably decreased in the amount of fluoride released. Conclusion: G1 and G3 released higher concentrations of fluoride, although no significant differences were found. Giomers recharged in the first 24 h after polymerization presented an improved and sustained fluoride release.