Rene Garcia-Contreras

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.

Nanomaterials made of non-toxic metallic sulfides: A systematic review of their potential biomedical applications

Metallic sulfides involve the chemical bonding of one or more sulfur atoms to a metal. Metallic sulfides are cheap, abundant semiconductor materials that can be used for several applications. However, an important and emerging use for non-toxic metallic sulfides in biomedical applications has arisen quickly in the medical field. In this systematic review, the available data from electronic databases were collected according to PRISMA alignments for systematic reviews. This review shows that these metallic sulfides could be promising for biomedical uses and applications. This systematic review is focused primarily on the following compounds: silver sulfide, copper sulfide, and iron sulfide. The aim of this review was to provide a quick reference on synthesis methods, biocompatibility, recent advances and perspectives, with remarks on future improvements. The toxicity of metallic sulfides depends directly on the cytotoxicity of their interactions with cells and tissues. Metallic sulfides have potential biomedical applications due to their antibacterial properties, uses in imaging and diagnostics, therapies such as photothermal therapy and chemotherapy in tumors and cancer cells, drug delivery and the fabrication of biosensors for the sensitive and selective detection of moieties, among others. Although current evidence about metallic sulfide NPs is promising, there are still several issues to be addressed before these NPs can be used in biomedicine. The current review is a brief but significant guide to metallic sulfides and their potential uses in the biomedical field.

Copper: synthesis techniques in nanoscale and powerful application as an antimicrobial agent

Nanosized metal particles show specific physical and chemical properties that allow the creation of new composites materials, which are important for multiple applications in biology and medicine such as infections control. Metal nanoparticles, mainly copper, exhibit excellent inhibitory effect on Gram-positive and Gram-negative bacteria; therefore the exploration about the efficient, economical, and friendly environmental technics to synthesize inorganic nanoparticles is imperative. In this work a brief overview of the several methods ismade including the comparison of the methods, mainly between sonochemical, microwave, and chemical routes. It allows determining the optimal parameters and technical conditions to synthesize copper nanoparticles with physical and chemical properties suitable for the oral bacterial inhibition.

A comparative in vitro efficacy of conventional rotatory and chemomechanical caries removal: Influence on cariogenic flora, microhardness, and residual composition.

Background: Chemomechanical caries removal system is part of the minimal invasive dentistry; the aim of the study was to compare the amount of bacteria after caries removal with chemomechanical system and conventional rotatory instruments and to test the Vickers microhardness and micro-RAMAN analysis of residual dentin after excavation. Materials and Methods: Molars were induced for demineralization, confirmed with DIAGNOdent; Streptococcus mutans were inoculated into the cavities and filled. Caries removal was performed with rotatory instruments and chemomechanical system; surviving bacteria were cultured for 24 and 48 hours at 37°C. Vickers microhardness and micro-RAMAN analysis were tested after excavation. Data were analyzed with Wilcoxon, continuity correction, odds ratio, ANOVA post hoc Tukey test, and Spearman correlation. Results: Demineralization was significantly detectable at 240 hours of incubation; conventional rotatory instruments and chemomechanical caries removal were effective in 19.4%-22.6% and 25.8%-32.3%, respectively. Vickers microhardness of chemomechanical system was higher (P < 0.0001) than conventional rotatory instruments and comparable to healthy dentin. Micro-RAMAN analysis showed that healthy dentin is correlated to chemomechanical system (R2 = 0.683, P < 0.00001) and drilling with burs (R2 = 0.139, P < 0.00001). Conclusion: The chemomechanical system is effective for caries elimination, comparable to conventional rotatory instruments; the remaining Vickers microhardness and composition surface tissue are similar to healthy dentin.

Effect of titanium dioxide nanoparticle on proliferation, drug-sensitivity, inflammation, and metabolomic profiling of human oral cells

Although titanium dioxide nanoparticles (TiO 2 NPs) improve mechanical and antibacterial properties of conventional glass ionomer cements (GIC), their biocompatibility is still controversial. Most of the previous studies of TiO 2 NP toxicity have been done using animal models or nonoral tissue cells. We initiated a series of studies to show how TiO 2 NPs affect viability, inflammation, and drug sensitivity in human malignant and nonmalignant cells derived from the oral cavity. TiO 2 NPs did not affect the cytotoxicity of representative anticancer drugs (doxorubicin, melphalan, 5-FU, docetaxel, gefitinib) against squamous carcinoma cell lines, but significantly stimulated PGE 2 production and COX-1/COX-2 protein expression by gingival fibroblasts in synergy with interleukin-1β (IL-1β). TiO 2 NPs slightly stimulated the proliferation of gingival fibroblasts (possibly for repair synthesis), and also enhanced GIC-induced PGE 2 production, suggesting a possible link between inflammation and hormesis. TiO 2 NPs, once endocytosed into vacuoles, reduced cellular intermediate molecules of the urea cycle and polyamine, S -adenosylmethionine, and glutathione synthetic pathways. TiO 2 NPs further enhanced the IL-1β effects on cellular metabolites. Based on these experimental evidences, we recommend that dental materials containing TiO 2 NPs for patients with gingivitis or periodontitis should be used carefully. Metabolomics analysis may be useful to elucidate the mechanism of inflammation induction and explore the therapeutic strategy for gingivitis and periodontitis.

Effects of TiO2 NPs Coating-Titanium for Fibroblast Adhesion

El objetivo fue determinar los efectos del recubrimiento con nanoparticulas de dioxido de titanio (TiO2 NPs) e irradiacion UV sobre placas de titanio (Ti) para la adhesion y proliferacion de fibroblastos gingivales humanos (FGH). Un total de 15 placas de Ti se dividieron en tres grupos (n= 5); (i) control Ti, (ii) experimental Ti+NPs TiO2, (iii) experimental: Ti+NPs TiO2+UV. Las placas fueron analizadas en microscopia de fuerza atomica (MFA) y se determino la rugosidad (Ra y Rmax). La irradiacion con UV se realizo durante 20 min. FGH fueron subcultivados en DMEM+10 % de suero fetal bovino a 37 °C con 5 % de CO2. 2x106 celulas/mL fueron inoculadas sobre las placas e incubadas durante 1 h, se lavaron con solucion salina de buffer fosfato. En el caso de la proliferacion celular, las celulas se incubaron por 24 h mas. La viabilidad celular se determino con el metodo de MTT, el formazan fue disuelto con dimetilsulfoxido y se analizo a 540 nm. Los experimentos se realizaron a partir de tres experimentos independientes y los datos se analizaron por Kruskall-Wallis y por comparacion multiple de Mann-Whitney. La topografia de la superficie de las muestras correspondio de la siguiente manera: Ti (Ra= 0,492 µm y Rms= 0,640 µm), Ti+NPs TiO2, (Ra= 0,55 µm y Rms= 0,714 µm), respectivamente. El recubrimiento con NPs TiO2 aumento significativamente la adhesion y proliferacion de HGF en comparacion con el grupo de Ti control (p <0,05). La modificacion de la superficie de las placas de Ti recubiertas con NPs TiO2 aumento significativamente la adhesion y proliferacion de HGF con la formacion de una superficie hidrofila que favorece la humectancia. Este tratamiento aqui informado tal vez sea un metodo conveniente para acelerar el proceso de la osteointegracion de los implantes dentales a base de titanio.

Effects of alkaline treatment for fibroblastic adhesion on titanium

Background: The surface energy of titanium (Ti) implants is very important when determining hydrophilicity or hydrophobicity, which is vital in osseointegration. The purpose of this study was to determine how Ti plates with an alkaline treatment (NaOH) affect the adhesion and proliferation of human periodontal ligament fibroblasts (HPLF). Materials and Methods: In vitro experimental study was carried out. Type 1 commercially pure Ti plates were analyzed with atomic force microscopy to evaluate surface roughness. The plates were treated ultrasonically with NaOH at 5 M (pH 13.7) for 45 s. HPLF previously established from periodontal tissue was inoculated on the treated Ti plates. The adhered and proliferated viable cell numbers were determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method for 60 min and 24 h, respectively. The data were analyzed using Kruskal–Wallis tests and multiple comparisons of the Mann–Whitney U-test,P value was fixed at 0.05. Results: The mean roughness values equaled 0.04 μm with an almost flat surface and some grooves. The alkaline treatment of Ti plates caused significantly (P < 0.05) more pronounced HPLF adhesion and proliferation compared to untreated Ti plates. Conclusion: The treatment of Ti plates with NaOH enhances cell adhesion and the proliferation of HPLF cells. Clinically, the alkaline treatment of Ti-based implants could be an option to improve and accelerate osseointegration.