A Comparative Evaluation of BPA Released from Different Orthodontic Adhesives: An Invitro Study using Gas Chromatography Coupled with Mass Spectrometry

BACKGROUND: Dental composite is increasingly used in orthodontic bracket bonding. Review of literature shows the evidence regarding the toxic effects of the released monomers from composites containing triethylene glycol dimethacrylate (TEGDMA) and HEMA, and indicates non negligible concentrations of residual BPA. AIM OF THE STUDY: The aim of this study is to qualitatively and quantitatively evaluate the BPA released using Gas phase chromatography coupled with mass spectrometry, from five different light cure composite adhesives when immersed in artificial saliva after curing. METHODOLOGY: Five different light cure orthodontic adhesives - Transbond XT, Heliosit, Ortho fix, Blugloo and Light bond are used in this study. Resin blocks (5 mm diameter * 3 mm thick) samples from each resin were prepared, and photo activated with a LED light-curing unit. Each sample was immersed in a separate glass tube containing 4 mL of artificial saliva solution at room temperature. Aliquots of 1 mL of the solutions with the samples were collected 30 minutes, 24 hours, 1 week, and 1 month after immersion. The composition of the BPA released was analyzed using Gas phase chromatography coupled with mass spectrometry. RESULT: The results of the conducted study showed that BPA was found to be released from all the 5 groups and was progressively increasing with increase in duration of immersion i.e, from 30 minutes to 1 month. Group 4 (Blugloo) showed the greatest release, at 1month 119.56 ng/g and Group 5 (Light bond) showed the least release, at 30 minutes - 55.00ng/g. and were statistically significant (p < 0.001). CONCLUSION: All orthodontic light cure adhesives tested showed BPA release. Blugloo and Light Bond had, respectively, the highest and lowest BPA releases. Even though the levels were significant, they are lower than the reference dose for daily ingestion

Treatment with Dental Polymer-based Restorative Materials. Exposure to Bisphenol A Effects on Pregnancy Outcomes

Dental polymer-based materials have become the first choice for restorative treatment in many countries, and the increased use of these materials over the last decades has raised questions about their biological safety. It has been shown that monomers as well as contaminants can leak from dental polymer-based restorations. Due to its estrogenic effect, bisphenol A (BPA) has been considered as a compound of specific interest. Exposure to BPA during early developmental stages of life is of particular concern. Large epidemiological studies exploring whether placement of dental polymer-based restorative materials in pregnant women is associated with increased risk for the fetus are warranted. The overall aim of the present work was to gain knowledge about the exposure to BPA from dental polymer-based restorations in humans and to investigate whether placement of polymer-based dental fillings during pregnancy is associated with increased risk for adverse birth outcomes. The thesis comprises three studies. In the first study, 20 individuals with six or more tooth surfaces filled with polymer-based materials (composite group) and 20 individuals without dental polymer-based materials (comparison group) were enrolled. Saliva was collected to assess if presence of dental polymer-based fillings is associated with increased salivary BPA level. In the second study, 20 patients who were scheduled for treatment of at least two tooth surfaces with dental polymer-based restorative material were included. Saliva and urine were collected before and up to one week after treatment to assess if placement of dental polymer-based material is associated with increased BPA concentrations in saliva and urine. The BPA concentration in the biological samples was determined using liquid chromatography/mass spectrometry. Presence of dental polymer-based fillings was associated with slightly higher concentration of BPA in saliva. Directly after treatment with dental polymer-based material, there was a considerable increase in the concentration of BPA in saliva. After the initial increase, the concentration decreased exponentially over time. One week after treatment, the salivary BPA level was only marginally higher compared to the pretreatment level. In urine, no statistically significant change of BPA concentration after placement was observed. In the third study, data from the large Norwegian Mother and Child Cohort Study was used to investigate if placement of white fillings during pregnancy was associated with increased risk for adverse birth outcomes. The results indicated that there was no statistically significant increased risk for adverse birth outcomes for participants who had white fillings placed during pregnancy compared with women who did not consult a dentist during pregnancy. In conclusion, dental polymer-based restorative materials might contribute to BPA exposure in humans. However, the exposure appears to be relatively short and transient. Women participating in the Norwegian Mother and Child Cohort Study who received dental polymer-based restorations (white fillings) during pregnancy had no increased risk for adverse birth outcomes including stillbirth, malformations, preterm birth, and low or high birth weight

ANTIMICROBIAL EFFECT OF NEW RESTORATIVE DENTAL MATERIAL INCORPORATING SILVER NANOPARTICLES

Secondary or recurrent caries are dental lesions originated at the margins of an existing restoration, and are considered the most common reason for restoration failure. Usually, these lesions are histologically similar to the primary caries and can be difficult to detect unless somewhat advanced, resulting in a considerable loss of tooth structure. Over the past decades, resin-based dental materials have been used in restorative dentistry for their excellent esthetics and improved mechanical performance. However, they represent potential sources of carbon and energy for microorganisms including oral bacteria and fungi residual in the dental cavity. In addition, cariogenic bacteria can infiltrate the restoration-tooth margins compromise the restoration’s longevity. Because caries at the restoration margins is a main reason for restoration failures, it would be highly desirable for the composite and bonding agent to possess antibacterial capabilities. Novel antibacterial dental materials were developed by introducing quaternary ammonium monomers, including 12-methacryloyloxydodecylpyridinium bromide (MDPB), dimethylaminohexadecyl methacrylate (DMAHDM), and dimethylaminododecyl methacrylate (DMADDM). These monomers can form covalent bonds with the polymer matrix and be immobilized in the resin-based materials, representing a non-released, contact-killing agent. Several other antimicrobial formulations were also developed, including a methacryloxylethylcetyl dimethyl ammonium chloride (DMAE-CB) containing adhesive, quaternary ammonium polyethylenimine (PEI) nanoparticles for antimicrobial dental composites, antibacterial glass ionomer cements, and antibacterial nanocomposites and bonding agents incorporating a quaternary ammonium dimethacrylate (QADM). Quaternary ammonium acrylate (QAM) resins possess positively-charged quaternary amine N+ which can interact with the negatively-charged membrane of bacteria, leading to membrane disruption and cytoplasm leakage. It is postulated that long-chained quaternary ammonium compounds can be especially effective by inserting into the bacterial membrane, resulting in physical disruption and bacteria death. Aside from the antibacterial monomers added to the resin matrix, an alternative approach is to add silver nanoparticles. Indeed, silver (Ag) is known for its antimicrobial activity against a diverse group of bacteria and has been used for many years as an antimicrobial substance in the medical field. Composite containing Ag particles with long-lasting antibacterial activity have been manufactured and observed to inhibit S. mutans growth . In addition, resins containing Ag nanoparticles were able to inhibit biofilm viability. Although the restorative materials had significant evolvement in the past few decades, the high rates of treatment failure suggest that the current restorative approaches are not yet optimized and have a potential for improvement. The aim of this work is to synthesize and evaluate new bioactive and antibacterial composite materials based on photo-activated Bis-GMA/TEGDMA matrix, containing an hydrotalcite-like compound intercalated with Ag nanoparticles as filler. We have obtained a dental resin with improved physical and biological properties and, in addition, able to release low amount of silver in a controlled and tunable way for a long period of time. In contrast to the conventional and resin-modified glass-ionomers, our CR-Agx were able to release silver ions when intraoral pH values drop below the critical pH of 5.5, counteracting the demineralization process of the tooth surface. The caries protective effect of these materials may be related to the material’s ability to release adequate amounts of silver ions for sustained periods of time and during acidic attack

Antimicrobial Materials with Medical Applications

This Special Issue of the International Journal of Molecular Science comprises a comprehensive study on “Antimicrobial Materials with Medical Applications”. The Special Issue has been inspired by the great progress made in the development of new antimicrobial materials that go beyond the resistance of microbes to modern antibiotics. It covers a selection of recent research and review articles in the field of antimicrobial materials and their medical applications. Moreover, it also provides an overview of this increasingly diverse field, presenting recent developments and the latest research, with particular emphasis on new antimicrobial surfaces, medical devices, contact lens, package materials, etc

Hetrocyclic methacrylate systems as vehicles for the release of active species.

PhDThe room temperature polymerising heterocyclic polymer system, poly(ethyl methacrylate)/tetrahydrofurfuryl methacrylate (PEM/THFM) has been shown previously to be biocompatible and supported tissue repair, specifically for bone and cartilage, and biologically inert when in contact with the dental pulp. It proved more effective, than other glassy methacrylates in the release of active species. The PEM/THFM system is a rigid material. The aim of this study was to develop and characterise the use of this system as a flexible patch, for application and retention to the buccal mucosa, thus facilitating sustained regulated release. Model species, dextrans, were used to represent macromolecular drugs whereby the effect of molecular weight could be studied. N-methyl pyrrolidone was added to the polymer system as a biocompatible plasticiser to enhance molecular mobility, and hence the transport of species. The effect of the addition of chitosan was also studied, due to its bioadhesiveness and permeation enhancing ability. A range of systems was investigated both in terms of water and species release. The release of the agent was measured by a fluorometer, the leachable components by HPLC and Confocal microscopy demonstrated the transport of water and active species through the system. Immunological and viability studies established whether the leachants or released components of the polymeric systems had an inflammatory or irritant action on `in vitro' stratified epithelium. The addition of N-methyl pyrrolidone, dextran and chitosan substantially increased water uptake, thus affecting the release kinetics. Analysis of the kinetics of water uptake showed Case I, combination of Case I and Case II, and Case II kinetics, depending on the systems studied. Dextran release was largely diffusion controlled, from which diffusion coefficients were calculated; the amount released varied between the systems studied

Physical Vapor Deposited Biomedical Coatings

The book outlines a series of developments made in the manufacturing of bio-functional layers via Physical Vapour-Deposited (PVD) technologies for application in various areas of healthcare. The scrutinized PVD methods include Radio-Frequency Magnetron Sputtering (RF-MS), Cathodic Arc Evaporation, Pulsed Electron Deposition and its variants, Pulsed Laser Deposition, and Matrix-Assisted Pulsed Laser Evaporation (MAPLE) due to their great promise, especially in dentistry and orthopaedics. These methods have yet to gain traction for industrialization and large-scale application in biomedicine. A new generation of implant coatings can be made available by the (1) incorporation of organic moieties (e.g., proteins, peptides, enzymes) into thin films using innovative methods such as combinatorial MAPLE, (2) direct coupling of therapeutic agents with bioactive glasses or ceramics within substituted or composite layers via RF-MS, or (3) innovation in high-energy deposition methods, such as arc evaporation or pulsed electron beam methods

Combining nanofabrication with natural antimicrobials to control denture plaque

Management of fungal biofilms represents a significant challenge to oral healthcare. As a preventive approach, minimising adhesion between intra-oral devices and microorganisms would be an important step forward. Denture stomatitis (DS) is a multifactorial denture-associated inflammation of the oral mucosa where candidal biofilms are one of the contributing factors. Therefore, understanding candidal biofilms on dentures and finding novel strategies to control these biofilms are of significance. Interference with the adhesion step of biofilm formation is hypothetically effective strategy to control biofilms. To understand the relationship between denture candidal load, denture material type and C. albicans biofilm forming heterogeneity in DS, quantitative polymerase chain reaction (qPCR) molecular method and crystal violet (CV) assay were used. This study investigated two novel strategies to control C. albicans biofilms through interfering with adhesion: natural polyphenol curcumin (CUR) and modifying the topography of the denture material surface. Based on the optimised effective CUR concentrations, CUR adsorption to PMMA denture material was spectrophotometrically analysed. Based on these data, the effect of adsorbed CUR to PMMA and CUR pre-exposure on adhesion of C. albicans were assessed. The effect of CUR on Candida-Candida adhesion was investigated and the expression profile of selected adhesion and aggregation-associated genes was assessed using qPCR method. Micro/nano-fabricated polycarbonate and PMMA materials were replicated using injection and compression moulding techniques, respectively and were characterised using scanning electron microscopy (SEM). Adhesion of C. albicans on the micro and nano-scaled patterns was assessed using microscopic and qPCR molecular methods, respectively. The physical characteristics of the materials were assessed using theta tensiometer and a white light profiler. The data demonstrated that although C. albicans was detected in greater quantities in diseased individuals, it was not associated with increased biofilm biomass. Denture substrata were shown to influence biofilm biomass, with poly(methyl methacrylate) providing the most suitable environment for C. albicans to reside. Subsequent studies showed that CUR concentrations of 50 μg/ml could prevent adhesion to PMMA. This effect was enhanced by the CUR pre-treatment of yeast cells (>90% inhibition, p < 0.001). Investigation of the biological impact of CUR showed that it preferentially affected immature morphological forms (yeast and germlings), and actively promoted aggregation of the cells. Transcriptional analyses showed that CUR temporally modulated adhesion and aggregation associated genes. Finally, PMMA denture material was replicated to show nano features. These topographies influenced adhesion of C. albicans, depending on the candidal morphological form and the shape. Nano-pit spatial arrangements variably affect the adhesion of C. albicans, where SQ arrangement demonstrated a significant anti-adhesive capacity. Differential adhesin expression was observed on these surfaces, which were affected by the wettability and roughness of surfaces tested. In summary, C. albicans is an important determinant of denture disease, so preventing its adhesion and biofilm formation were worthwhile objectives. This thesis has shown that CUR molecules and SQ nano-pit topographies reduced C. albicans adhesion, demonstrating that chemical and physical inhibition strategies are useful. The data presented in this thesis showed the high potential of the novel strategies to be used against C. albicans biofilms, and encourages the further investigation of these approaches against polymicrobial denture biofilms

Aplicação do teste do micronúcleo em células da mucosa bucal como biomarcador de expoisção a mutagenos

O teste do micronúcleo vem ganhando cada vez mais espaço no biomonitoramento de populações, uma vez que se mostrou um marcador útil para a investigação de possíveis agressões genômicas sob condições ambientais adversas, estilo de vida e de natureza ocupacional em decorrencia da exposição de agentes quimícos e fisícos. O objetivo desta revisão foi avaliar se o ensaio de micronúcleo em células esfoliadas orais é um biomarcador adequado para o biomonitoramento de populações específicas expostas a agentes mutagênicos. Por meio das bases de dados eletrônicas PubMed/Medline, Scopus e Web of Science, foram pesquisados todos os estudos que examinaram a relação entre exposição a poluentes ambientais, radiação e ensaio do micronúcleo em células orais em crianças e adultos. Os resultados referentes aos danos citogenéticos em crianças e adultos por meio de uma revisão sistemática da literatura foi capaz de demonstrar uma forte associação entre aumento da frequência de micronúcleos em células esfoliadas orais expostas a poluentes ambientais. Na revisão sistemática de crianças que realizaram exames radiográficos odontológicos, os resultados se mostraram conflitantes. Porém, quando efetuada a metanálise, a micronucleação de células epitelais foi maior, após a realização do exame, mostrando que a radiação oriunda de exames de imagem pode provocar alterações nucleares nos mais jovens. Já a revisão sistemática sobre adultos expostos a pesticidas, os resultados demonstraram que houve um aumento de células micronucleadas, porém na metanálise houve alta heterogeneidade, uma vez que, os estudos apresentaram divergências sobre seus protocolos. A partir dos resultados obtidos no presente estudo, é possível inferir que populações expostas aos mais diferentes agentes genotóxicos podem se beneficar com a inclusão do ensaio do micronúcleo em células do epitélio oral, revelando-se como um importante biomarcador de danos genéticos.The micronucleus test has been gaining more and more space in the biomonitoring of populations, since it has proved to be a useful marker for the investigation of possible genomic injuries due to environmental, lifestyle and occupational conditions and also for the exposure of chemical and physical agents. The aim of this review was to assess whether the micronucleus assay in oral exfoliated cells is a suitable biomarker for biomonitoring pediatric populations exposed to mutagens. Using PubMed/Medline, Scopus, and Web of Science electronic databases, all studies that examined the relationship between exposure to environmental pollutants, radiation, and oral cell micronucleus assay in children were searched. The results regarding cytogenetic damage induced by environmental pollutants in children through a systematic review, was able to demonstrate a strong association between increased frequency of micronuclei in oral exfoliated cells of children exposed to environmental pollutants. In the systematic review of children who underwent dental radiographic examinations, the results were conflicting. However, when the meta-analysis was carried out, the micronucleation of epithelial cells was higher after the examination when compared to the period before the radiography was performed, showing that radiation from imaging tests can cause nuclear alterations in younger people. The systematic review on adults exposed to pesticides, however, showed that there was an increase in the marking of micronucleated cells when in contact with the pesticide, but in the meta-analysis there was high heterogeneity, since the studies showed divergences about their protocols. In short, such results are consistent with the fact that the micronucleus test is a plausible methodology for detecting mutagenic agents from the environment, pesticides and radiation and under various contexts and paradigms