Risk assessment of predicted serum concentrations of bisphenol A in children and adults following treatment with dental composite restoratives, dental sealants, or orthodontic adhesives using physiologically based pharmacokinetic modeling.

Bisphenol A (BPA) is a chemical used to manufacture bisphenol A glycidyl methacrylate (BisGMA). BisGMA has been used for decades in dental composite restoratives, sealants, and adhesives. Based on published studies, exposure to low concentrations of BPA are possible from dental and orthodontic devices. The serum BPA concentrations arising from such devices and oral doses were predicted using a PBPK model in children and adult females based on 1) published extraction data for cured and uncured 3M ESPE Filtek Supreme Ultra Flowable, 3M ESPE Filtek Bulk Fill Restorative, and 3M ESPE Clinpro Sealant and 2) published 20% ethanol/water and water rinsate data following orthodontic application with 3M ESPE Transbond MIP Primer and 3M ESPE Transbond XT Adhesive. Predicted oral exposure to BPA arising from these dental and orthodontic devices is low (median <10 ng/treatment) and predicted serum BPA concentrations were also low (<10-4 nM). Even the maximum predicted exposure in this study (533.2 ng/treatment) yields a margin of exposure of 7.5 relative to the EFSA t-TDI (4 µg/kg-day) and is only 2.8% of the daily BPA exposure for the US population in a 58-kg woman (15,660 ng/day). Therefore, the exposure to BPA arising from the 3M ESPE dental and orthodontic devices evaluated in this study is negligible relative to daily BPA exposure in the general population and these potential BPA sources do not constitute a risk to patients.

Isocyanate-terminated urethane-based methacrylate for in situ collagen scaffold modification.

When damaged or fractured collagen-rich hard tissues are repaired by resin material, the collagen matrix may be used as a scaffold, after removal of the natural minerals, for resin monomers to penetrate and polymerize in-situ. Formation of a collagen-polymer hybrid biocomposite via mechanical hybridization provides a stable and strong link between endogenous tissue and the prosthesis for successful clinical integration. However, the heterogeneity between hydrophobic resin polymers and hydrophilic collagen presents a challenge to the quality of hybrid biocomposite. The objective of the present study was to evaluate the potential benefits of a collagen-reactive monomer (CRM, an isocyanate-terminated urethane-based methacrylate) with covalent affinity to collagen as "chemical link" to enhance in-situ resin hybridization within a collagen scaffold. Here, the CRM ligand with active isocyanate group may be chemically grafted onto the collagen receptor via covalent and hydrogen bonds. Dentin-derived collagen chemical modified by CRM shows improved mechanical property, thermostability and enzymatic stability. Moreover, CRM inhibited both exogenous and endogenous collagenase activities. The modification of collagen by chemical grafting of resin monomers improved its mechanical and physicochemical properties and demonstrated the potential of CRM for use in promoting chemical adhesion and creating a much stronger and durable bonding interface. Formation of a chemical bond between polymer and collagen scaffold in-situ improves the mechanical performance of collagen and may create a much stronger and durable collagen-polymer hybrid material. Addition of CRM into adhesives might effectively prolong the longevity of clinical resin-bonded restorations.

Assessment of oral ciprofloxacin impaired gut barrier integrity on gut bacteria in mice.

Gut bacteria and gut barrier plays important roles in body homeostasis. Ciprofloxacin (CPFX) is widely used to treat bacterial infections. However, whether high dosage of CPFX has side effects on gut barrier integrity is still unclear. Our results indicated that the High CPFX treatment (1 mg/ml) caused weight loss, nervousness, anorexia, and increased apoptosis cells in gut, but less influence was observed in the Low CPFX group (0.2 mg/ml). Meanwhile, the High CPFX treatment impaired tight junction molecules Ocln/ZO-1 level and down-regulated antibacterial genes expression (reg3γ, pla2g2α and defb1). Further, the High CPFX treatment increased pro-inflammatory cytokine IL-1ß in intestinal tract, decreased IL-17A of duodenum but increased IL-17A of colon at day 37. In addition, the gut bacterial diversity and richness behaved significantly loss regarding CPFX treatment, especially in the High CPFX group during the experiment. Indole exhibited sharply decline in both Low and High CPFX groups at day 7, and the High CPFX mice needed longer time on restoring indole level. Meanwhile, CPFX treatment strongly decreased the concentrations of butyric acid and valeric acid at day 1. Correlation analysis indicated that the linked patterns between the key bacteria (families Bacteroidales_S247, Ruminococcaceae and Desulfovibrionaceae) and metabolites (indole and butyric acid) were disturbed via the CPFX treatment. In conclusion, the High CPFX treatment impaired the gut barrier with the evidence of reduced expression of tight junction proteins, increased apoptosis cells and inflammatory cells, decreased the bacterial diversity and composition, which suggesting a proper antibiotic-dosage use should be carefully considered in disease treatment.

Development and calibration of biochemical models for testing dental restorations.

Currently, resin composites are the most popular materials for dental restoration in clinical practice. Although the properties of such materials have been improved significantly, together with better clinical techniques used for their placement, early restoration failure still occurs too frequently. As clinical studies take years to complete, and new resin composites are being produced at ever increasing pace, laboratory assessment using accelerated but representative tests is necessary. The main types of failure in resin-composite restoration are tooth/restoration fracture and secondary caries, which are caused by a combination of mechanical and biochemical challenges. In this study, a biofilm model (S. mutans) and a chemical model (lactic-acid buffer) for producing artificial caries in bovine dentin are developed and calibrated against in situ data. Using a power law relationship between the demineralization depth and challenge duration, scale factors that convert the in vitro durations to the equivalent clinical durations are determined for different pH values for each model. The scale factors will allow the synchronization of biochemical and mechanical challenges in terms of their rates of action to potentially test resin-composite restoration in an accelerated but clinically representative manner. STATEMENT OF SIGNIFICANCE: Although the properties of resin composites for dental restoration have been improved significantly, early restoration failure still occurs too frequently. As clinical studies take years to complete, accelerated laboratory testing is necessary. Resin-composite restoration fail mainly through fracture and secondary caries, caused by a combination of mechanical and biochemical challenges. In this study, a biofilm and a chemical model for producing artificial caries in bovine dentin are calibrated against in situ data. Using a power law relationship between demineralization depth and challenge duration, scale factors are determined for different pH for each model. The scale factors will allow the synchronization of biochemical and mechanical challenges in testing resin-composite restoration in an accelerated but clinically representative manner.

Human neutrophils degrade methacrylate resin composites and tooth dentin.

Cholesterol esterase-like (CE) activity from saliva and esterase from cariogenic bacteria hydrolyze ester linkages of dental methacrylate resins. Collagenolytic, matrix metalloproteinase-like (MMP) activities from dentin and bacteria degrade collagen in demineralized tooth dentin. Human neutrophils in the oral cavity contain factors that are hypothesized to have CE and MMP activities that could contribute to the degradation of methacrylate resins and dentinal collagen. OBJECTIVES: To measure the CE and MMP activities from human neutrophils and their ability to degrade dental methacrylate resin composite and dentinal collagen. Neutrophils' CE and MMP activities were measured using nitrophenyl-esters or fluorimetric MMP substrates, respectively. Neutrophils' degradation of resin composite and dentinal collagen was quantified by measuring release of a universal 2,2-Bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bisGMA)-derived resin composite degradation byproduct, bishydroxy-propoxy-phenyl-propane (bisHPPP), or a collagen degradation by-product, hydroxyproline, respectively using ultra performance liquid chromatography/mass spectrometry. Neutrophils' CE activity increased the release of bisHPPP from bisGMA monomer compared to control after 24 and 48 h (p < 0.05). Neutrophils degraded polymerized resin composite and produced higher amounts of bisHPPP than buffer after 48 h of incubation (p < 0.05). Neutrophils show generic MMP, gelatinase, MMP-2 and MMP-9, and collagenase, MMP-1 and MMP-8 activities that were stable or increased over the first 24 h (p < 0.05). Neutrophils degraded demineralized dentin more than buffer-only groups, indicated by higher amounts of hydroxyproline (p < 0.05). The ability of neutrophils to degrade both dental resin composite and tooth dentin, suggest neutrophil's potential role in root caries, and in recurrent carries by accelerating the degradation of resin-dentin interfaces, and compromising the longevity of the restoration. STATEMENT OF SIGNIFICANCE: Neutrophils are part of the innate immune system and are constantly entering the oral cavity through the gingival sulcus, in direct contact with the tooth, restoration, restoration-tooth margins and pathogenic bacteria. The current study is the first to characterize and quantify degradative activities from neutrophils toward methacrylate resin and demineralized dentin, the two main components of the restoration-tooth interface, suggesting that this interface could be negatively influenced by neutrophils, potentially contributing to increase in caries formation and progression, and premature restoration failure. This study provides a significant finding to the biomaterials and oral health fields by identifying a potential weakness in current restorative procedures and materials used to manage gingival proximal and cervical gingival or sub-gingival carious lesions.

A comparative evaluation of the staining capacity of microhybrid and nanohybrid resin-based composite to indian spices and food colorants: An In vitro study.

INTRODUCTION: Resin composite restorative materials can mimic the natural color and shade of the tooth. However, exogenous colorants from food and drinks can stain them due to adsorption. The influence of Indian food colorants and spices on resin composite restorations has not been evaluated extensively. AIM: This study aims to evaluate the staining capacity of microhybrid and nanohybrid resin-based composites, to saffron extract, tandoori powder, and turmeric powder. SUBJECTS AND METHODS: Forty samples of microhybrid (Kulzer Charisma) and nanohybrid (3M Filtek Z350) resin composites were prepared using an acrylic template of dimension 5 mm × 3 mm. They were randomly divided into four groups and immersed into solutions of saffron extract, tandoori powder, and turmeric powder. Distilled water was used as the control group. Color values (LFNx01, aFNx01, bFNx01) were measured by colorimeter using the CIE LFNx01aFNx01bFNx01 system before and after 72 h of immersion. Color differences ΔEFNx01ab were statistically analyzed. STATISTICAL ANALYSIS USED: Two-way ANOVA and post-hoc Tukey (honest significant difference) test were done using IBM SPSS Statistics for Windows, Version 19.0. Armonk, NY: IBM Corp. RESULTS AND DISCUSSION: : All the immersion media changed the color of the resin composites to varying degrees. However, turmeric solution showed the maximum mean color variation ΔEFNx01ab of 14.8 ± 2.57 in microhybrid resin composites and 16.8 ± 3.50 in nanohybrid resin composites. CONCLUSION: Microhybrid and nanohybrid resin composites tend to stain to Indian food colorants, especially to turmeric powder.

Enterococcus faecalis Hydrolyzes Dental Resin Composites and Adhesives.

INTRODUCTION: After root canal treatment, the dentin-sealer interface undergoes degradation, allowing for interfacial microbial biofilm proliferation and treatment failure. Saliva and cariogenic bacteria showed esterase-like activities (ie, cholesterol esterase [CE]-like and/or pseudocholinesterase [PCE]-like) that degrade methacrylate-based resin materials and/or the restoration-tooth interface, increasing microbial interfacial proliferation. Enterococcus faecalis is a gram-positive bacterium that is commonly detected in persistent endodontic infections. The aim of this study was to measure E. faecalis esterase-like, CE-like, and PCE-like activities and to assess the ability of the bacterium to degrade methacrylate-based resin composite (RC) and total-etch (TE) and self-etch (SE) adhesives. METHODS: CE-like and PCE-like activities from E. faecalis were measured using nitrophenyl and butyrylthiocholine substrates, respectively. The ability of E. faecalis to degrade resin composite, total-etch and self-etch adhesives was examined by quantifying the release of a universal resin degradation by-product (ie, Bis[hydroxypropoxy]-phenyl propane [BisHPPP]) using high-performance liquid chromatography. RESULTS: E. faecalis showed CE-like (1.23 ± 0.13 U/µg dry bacteria) but no PCE-like activity. After 30 days and/or 14 days of incubation, the amount of BisHPPP released was significantly higher in the presence of bacteria versus media for TE and RC but not SE (P < .05). The amount of BisHPPP released after 30 days of incubation with bacteria was highest for TE (23.69 ± 1.72 µg/cm2) followed by RC (3.43 ± 1.20 µg/cm2) and lowest for SE (0.86 ± 0.44 µg/cm2) (P < .05). CONCLUSIONS: E. faecalis possesses esterase-like degradative activity toward dental methacrylate resin restoration materials, which could accelerate the degradation of the dentin-methacrylate resin interface, increasing bacterial biofilm proliferation and penetration into the root canal system.

Time of Application of Sodium Ascorbate on Bonding to Bleached Dentin.

This study examined the effects of different application times of sodium ascorbate (SA) on the bond strength of composite resin to bleached dentin. Specimens with an exposed dentin surface were divided into 3 groups according to the type of bleaching agent used: Group A, mixture of sodium perborate (SP) and distilled water (DW); Group B, mixture of SP and hydrogen peroxide (HP); control group, no bleaching. Each group was classified into 10 subgroups. Subgroups IB and DB underwent immediate bonding and delayed bonding, respectively. 10% SA was applied to 3, 5, 10, and 30 minutes and 1, 24, 48, and 72 hours, respectively. Microtensile bond strength (µTBS) was measured after restoration, and the data was analyzed by one-way ANOVA and Scheffé's test. Before restoration, the dentin surfaces were examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). SEM showed that most dentin surfaces were filled with crystals when SA was applied to more than 24 hours. EDS revealed peaks of calcium, carbon, oxygen, and sodium. The application of SA for 5 minutes to 48 hours or for 30 minutes to 24 hours is suggested when a mixture of SP and DW or HP is used, respectively.

Chlorhexidine Nanocapsule Drug Delivery Approach to the Resin-Dentin Interface.

In this study, we are introducing a new drug-delivery approach to demineralized dentin substrates through microsized dentinal tubules in the form of drug-loaded nanocapsules. Chlorhexidine (CHX) is widely used in adhesive dentistry due to its nonspecific matrix metalloproteinase inhibitory effect and antibacterial activities. Poly(ε-caprolactone) nanocapsules (nano-PCL) loaded with CHX were fabricated by interfacial polymer deposition at PCL/CHX ratios of 125:10, 125:25, and 125:50. Unloaded nanocapsules (blank) were fabricated as control. The fabricated nanocapsules were characterized in vitro in terms of particle size, surface charges, particle recovery, encapsulation efficiency, and drug loading. Nanocapsule morphology, drug inclusion, structural properties, and crystallinity were investigated by scanning and transmission electron microscopes (SEM/TEM), energy-dispersive x-ray analysis, Fourier transform infrared spectroscopy, and x-ray diffraction. Initial screening of the antibacterial activities and the cytotoxicity of the nanocapsules were also conducted. Nanocapsules, as carried on ethanol/water solution, were delivered to demineralized dentin specimens connected to an ex vivo model setup simulating the pulpal pressure to study their infiltration, penetration depth, and retention inside the dentinal tubules by SEM/TEM. Nanocapsules were Ag labeled and delivered to demineralized dentin, followed by the application of a 2-step etch-and-rinse dentin adhesive. CHX-release profiles were characterized in vitro and ex vivo up to 25 d. Spherical nanocapsules were fabricated with a CHX core coated with a thin PCL shell. The blank nanocapsules exhibited the largest z-average diameter with negatively charged ζ-potential. With CHX incorporation, the nanocapsule size was decreased with a positive shift in ζ-potential. Nano-PCL/CHX at 125:50 showed the highest drug loading, antibacterial effect, and CHX release both in vitro and ex vivo. SEM and TEM revealed the deep penetration and retention of the CHX-loaded nanocapsules inside dentinal tubules and their ability to be gradually degraded to release CHX in vitro and ex vivo. Ag-labeled nanocapsules revealed the close association and even distribution of nanocapsules throughout the resin tag structure. This study demonstrated the potential of introducing this novel drug-delivery approach to demineralized dentin substrates and the resin-dentin interface with nanosized CHX-loaded nanocapsules through the microsized dentinal tubules.

Influence of light curing units and fluoride mouthrinse on morphological surface and color stability of a nanofilled composite resin.

Composite resin is a dental material susceptible to color change over time which limits the longevity of restorations made with this material. The influence of light curing units and different fluoride mouthrinses on superficial morphology and color stability of a nanofilled composite resin was evaluated. Specimens (N = 150) were prepared and polished. The experimental groups were divided according to the type of light source (halogen and LED) and immersion media (artificial saliva, 0.05% sodium fluoride solution-manipulated, Fluordent Reach, Oral B, Fluorgard). Specimens remained in artificial saliva for 24-h baseline. For 60 days, they were immersed in solutions for 1 min. Color readout was taken at baseline and after 60 days of immersion. Surface morphology was analyzed by Scanning Electron Microscopy (SEM) after 60 days of immersion. Color change data were submitted to two-way Analysis of Variance and Tukey tests (α = 0.05). Surface morphology was qualitatively analyzed. The factor light source presented no significant variability (P = 0.281), the immersion media, significant variability (P < 0.001) and interaction between factors, no significant variability (P = 0.050). According to SEM observations, no difference was noted in the surface of the specimens polymerized by different light sources, irrespective of the immersion medium. It was concluded that the light source did not influence the color stability of composite, irrespective of the immersion media, and among the fluoride solutions analyzed, Fluorgard was the one that promoted the greatest color change, however, this was not clinically perceptible. The immersion media did not influence the morphology of the studied resin.

Cigarette smoke: effects on water sorption and solubility of restorative dental composites.

Although scientific evidence has shown the effects of tobacco on changes in the color of composite resins, the association between tobacco exposure and the physical properties of composite resins has not been thoroughly investigated. The purpose of this study was to evaluate the effects of cigarette smoke products on water sorption and solubility of microfilled, microhybrid, and nanofilled composite resins (Durafill VS, Filtek Z250, and Filtek Z350 XT, respectively). Ten discs were prepared of each material and divided into 2 groups (n =5), according to cigarette smoke exposure. Specimens were first desiccated until a constant mass was obtained (M1). Then half of the samples were immersed in deionized water while the other half were exposed daily to tobacco smoke, then washed and stored in deionized water. After 21 days, the resin discs were measured (M2) and placed in desiccators until constant mass was achieved (M3). Water sorption and solubility were calculated and the data was statistically analyzed. Water sorption revealed significant differences among the composite resins. The Filtek Z350 XT exhibited the highest water sorption, followed by Durafill VS and Filtek Z250. Cigarette smoke significantly increased water sorption for all products, but only the solubility of Durafill VS showed a significant difference. Filtek Z250 demonstrated significantly lower solubility than Durafill VS, and Filtek Z350 XT had intermediate values. These results indicated that water sorption and solubility varied among the products, and tobacco smoke may alter the physical properties of resin-based materials.

Rapid and reversible knockdown of endogenous proteins by peptide-directed lysosomal degradation.

Rapid and reversible methods for altering the levels of endogenous proteins are critically important for studying biological systems and developing therapeutics. Here we describe a membrane-permeant targeting peptide-based method that rapidly and reversibly knocks down endogenous proteins through chaperone-mediated autophagy in vitro and in vivo. We demonstrate the specificity, efficacy and generalizability of the method by showing efficient knockdown of various proteins, including death associated protein kinase 1 (160 kDa), scaffolding protein PSD-95 (95 kDa) and α-synuclein (18 kDa), with their respective targeting peptides in a dose-, time- and lysosomal activity-dependent manner in rat neuronal cultures. Moreover, we show that, when given systemically, the peptide system efficiently knocked down the targeted protein in the brains of intact rats. Our study provides a robust and convenient research tool for manipulating endogenous protein levels and may also lead to the development of protein knockdown-based therapeutics for treating human diseases.

Biodegradation of resin composites and adhesives by oral bacteria and saliva: a rationale for new material designs that consider the clinical environment and treatment challenges.

OBJECTIVE: To survey the recent literature from the late 1980s to recent years in order to assess the relationship between resin degradation, catalyzed by biological factors, and clinical failure outcomes such as marginal breakdown. METHODS: The literature shows that degradation occurs in many manufacturers' products despite varied vinyl acrylate compositions. The authors examine salivary enzyme activity and their ability to degrade the polymeric matrix of resin composites and adhesives, as well as oral microorganisms that can promote demineralization of the tooth surface at the marginal interface. A survey of recent research relating matrix metalloproteinase (MMPs) to the degradation of the exposed collagen at the dentin adhesive interface is also discussed in the context of marginal breakdown. RESULTS: The literature provides strong support that together, the above factors can breakdown the marginal interface and limit the longevity of resin composite restorations. The authors have found that the field's current understanding of resin biodegradation in the oral cavity is just beginning to grasp the role of bacteria and enzymes in the failure of resin-based restorations. SIGNIFICANCE: Knowledge of these biodegradation processes is pertinent to areas where innovative strategies in the chemistry of restorative materials are anticipated to enhance the longevity of resin composites.

Influence of chemical degradation on the surface properties of nano restorative materials.

OBJECTIVES: The aim of this in vitro study was to investigate the effect of chemical degradation on the surface roughness (Ra) and hardness (Knoop hardness number [KHN]) of nano restorative materials. METHODS: Disc-shaped specimens (5-mm diameter; 2-mm thick) of Filtek Z350 and TPH Spectrum composites and the Vitremer and Ketac Nano light-curing glass ionomer cements were prepared according to the manufacturers' instructions. After 24 hours, polishing procedures were performed and initial measurements of Ra and KHN were taken. The specimens were divided into 12 groups (n=10) according to material and storage media: artificial saliva, orange juice, and Coca-Cola. After 30 days of storage, the specimens were reevaluated for Ra and KHN. The pH values of the storage media were measured weekly. Data were tested for significant differences by repeated-measures three-way analysis of variance and Tukey tests (p<0.05). RESULTS: Composites were found to present lower roughness values and higher hardness values than the ionomeric materials under all storage conditions. After degradation, the KHN of all experimental samples decreased significantly, while the Ra of the ionomeric materials increased, depending on the media, with a markedly negative impact of Coca-Cola and orange juice. There was no difference among the storage media for Filtek Z350 with regard to the KHN values. Nanofillers did not show any influence on the roughness and hardness of resin-modified glass ionomer cements and resin composites concerning their degradation resistance.

A review of adaptive mechanisms in cell responses towards oxidative stress caused by dental resin monomers.

Dental composite resins are biomaterials commonly used to aesthetically restore the structure and function of teeth impaired by caries, erosion, or fracture. Residual monomers released from resin restorations as a result of incomplete polymerization processes interact with living oral tissues. Monomers like triethylene glycol dimethacrylate (TEGDMA) or 2-hydroxylethyl methacrylate (HEMA) are cytotoxic via apoptosis, induce genotoxic effects, and delay the cell cycle. Monomers also influence the response of cells of the innate immune system, inhibit specific odontoblast cell functions, or delay the odontogenic differentiation and mineralization processes in pulp-derived cells including stem cells. These observations indicate that resin monomers act as environmental stressors which inevitably disturb regulatory cellular networks through interference with signal transduction pathways. We hypothesize that an understanding of the cellular mechanisms underlying these phenomena will provide a better estimation of the consequences associated with dental therapy using composite materials, and lead to innovative therapeutic strategies and improved materials being used at tissue interfaces within the oral cavity. Current findings strongly suggest that monomers enhance the formation of reactive oxygen species (ROS), which is most likely the cause of biological reactions activated by dental composites and resin monomers. The aim of the present review manuscript is to discuss adaptive cell responses to oxidative stress caused by monomers. The particular significance of a tightly controlled network of non-enzymatic as well as enzymatic antioxidants for the regulation of cellular redox homeostasis and antioxidant defense in monomer-exposed cells will be addressed. The expression of ROS-metabolizing antioxidant enzymes like superoxide dismutase (SOD1), glutathione peroxidase (GPx1/2), and catalase in cells exposed to monomers will be discussed with particular emphasis on the role of glutathione (GSH), which is the major non-enzymatic antioxidant. The causal relationship between vital cell functions like the regulation of cell survival or cell death in monomer-treated cell cultures and the availability of GSH will be highlighted. We will also consider the influence of monomer-induced oxidative stress on central signal transduction pathways including mitogen-activated protein kinases (MAPK) ERK1/2, p38, and JNK as well as the stress-activated transcription factors downstream Elk-1, ATF-2, ATF-3, and cJun. Finally, we address signaling pathways originating from monomer-induced DNA damage including the activation of ATM (ataxia-telangiectasia mutated), Chk2, p53, p21, and H2AX. The understanding of the mechanisms underlying adaptive cell responses will stimulate a constructive debate on the development of smart dental restorative materials which come into contact with oral tissues and effective strategies in dental therapy.

Genotoxic biomonitoring of flowable and non-flowable composite resins in peripheral blood leukocytes.

OBJECTIVE: Composite restorative materials represent one of the most important groups of materials in contemporary dental practice. However, their incomplete polymerization may lead to monomer-induced genotoxicity. The objective of this study was to evaluate the genotoxicity of three flowable (Filtek Supreme XT Flow, Tetric EvoFlow, Gradia Direct Flo) and three non-flowable dental composite materials (Filtek Z250, Tetric EvoCeram, Gradia Direct Posterior). MATERIALS AND METHODS: Genotoxicity assessment of composite materials was carried out in vitro in human peripheral blood leukocytes using the alkaline single-cell gel electrophoresis technique (comet assay). Prepared materials were eluted in saline solution for 1 h, 1 day and 5 days. Thereafter leukocyte cultures were treated with different concentrations of eluates obtained from each of the tested dental composite materials. Kruskall-Wallis non-parametric test was used for statistical analysis (p < 0.05). RESULTS: The tested materials did not show genotoxic effects after exposure of leucocytes to 1 h eluates. Culture treated with 1 day eluates of all tested materials, only at a highest concentration (10(-2)), affected the measured cytogenetic parameters. Of all tested materials, only Filtek Z250 and Filtek Supreme XT Flow did not exhibit a genotoxic effect in cultures that were under the influence of 5 day eluates. CONCLUSION: Tested materials exhibited limited genotoxic activity in peripheral blood leukocytes. Since the effect was observed only in leukocyte cultures treated by 1-day eluates at the highest concentration (10(-2)) and it decreases in cultures exposed to 5 day eluates, it should not pose a significant risk to the human genome.

Microtomographic evaluation of the bone-cell interactions with a silorane-based composite.

The low-shrink Silorane-based composite could bond effectively to bone and showed the potential be used as a bone cement. Bone organ culture maintains the anatomical order, natural cell-to-cell and cell-to-matrix relationship. The purpose of this study was to evaluate the responses of bone cells to a Silorane-based composite which was compared with a representative polymethyl methacrylate (PMMA) bone cement. The critical size defects were created through the parietal bones from one litter of mice. The paired bones were divided into two groups: Silorane-based composite group and PMMA group. The prepared two groups of disks were put into the defects. The cultures were grown in vitro for 38 days and analyzed with microcomputed-tomography, dissecting-microscope, phase- contrast-microscope, scanning-electron-microscopy, and energy- dispersive-X-ray. At the 10th day, the Silorane disk was almost fully covered by a sheet of cells but the cells hardly attached to the disk surface. The edge of the PMMA disk was covered by a sheet of cells and the migrated individual cells attached to the whole surface of the disk. At the 38th day, some cells attached to the exposed disk area of the Silorane disk while the formed tissues covered the whole surface of the PMMA disk. The collagen fibers, globular deposits and bone formation were visible in both groups. The Silorane-based composite showed promise as a potential bone cement when compared with PMMA which is used in clinical orthopedics. However, the cell attachment to PMMA was evidently better than to Silorane-based composite.

In vitro long-term degradation of aesthetic restorative materials in food-simulating media.

OBJECTIVE: The aim of this study was to evaluate the effect of long-term food-simulating media storage on degradation of restorative materials through roughness measurements. MATERIALS AND METHODS: Sixty cylindrical specimens of each material (Filtek Z250, Esthet X, Filtek Flow, Dyract AP and Vitremer) were prepared, stored for 24 h, and polished. The surface roughness analysis was conducted using Surfcorder (SE1700) roughness-measuring instrument. Three traces were recorded on each specimen at three different locations. The specimens were randomly distributed into five groups (n = 12) according to the storage media: (water, ethanol, Coca-Cola®, citric acid and lactic acid). Roughness measurements were recorded after 1 week, 1, 3 and 6 months. The storage solutions were weekly changed. Data were submitted to ANOVA and Tukey test (p < 0.05). RESULTS: There was no significant increase on roughness means for Filtek Z250, Filtek Flow and Vitremer over time, regardless the storage media. Significant increase on surface roughness was observed for Esthet X after 1 month of storage in Coca-Cola® and after 3 months of storage in citric acid and for Dyract AP after 6 months in water. There were no significant differences on surface roughness between resin composites and compomer. Resin-modified glass ionomer showed a significantly higher surface roughness mean than the other materials. CONCLUSIONS: Food-simulating media affects the surface roughness of the materials. Biodegradation is material-, solution- and time-dependent.

Degradation of polymeric restorative materials subjected to a high caries challenge.

OBJECTIVES: The aim of this study was to evaluate the degradation of different resin filling materials after a caries challenge, by high performance liquid chromatography (HPLC) and contact angle (θ) measurement. METHODS: Four different polymeric restorative materials (a resin composite, a polyacid-modified resin composite, an ormocer and a resin-modified glass ionomer cement) were tested. Five samples (30 mm × 6 mm × 2 mm) of each material were formed in a Teflon mold, following the manufacturer's instructions. After pH cycles, the solutions were injected in an HPLC. The θ was obtained, before and after pH cycle, by a goniometer at 60% air humidity and 25°C. A distilled water drop (0.006 ml) was put on the material surface, and after 6 min, 10 measures were obtained at 20s intervals. Each sample received 4 drops, one at a time, on different areas. RESULTS: HPLC results showed elution of byproducts in all materials. This was greater in the acid medium. Bis-GMA and TEGDMA were detected in TPH Spectrum and Definite residues. Analyses of the contact angle by ANOVA and Student-Neuman-Keuls's test showed that the surfaces of TPH Spectrum, Dyract AP and Definite were altered, except Vitremer (p<0.05). SIGNIFICANCE: All materials tested degraded on a caries simulated medium, suggesting that a great effort should be made to disseminate oral health information, since a high caries challenge environment (low pH) can lead to dental composite degradation, with potential toxic risks to patients.