Responsive antimicrobial dental adhesive based on drug-silica co-assembled particles.

Most dental resin composite restorations are replacements for failing restorations. Degradation of the restoration-tooth margins by cariogenic bacteria results in recurrent caries, a leading cause for restoration failure. Incorporating antimicrobial agents in dental adhesives could reduce interfacial bacterial count and reduce recurrent caries rates, inhibit interfacial degradation, and prolong restoration service life, while minimizing systemic exposure. Direct addition of antimicrobial compounds into restorative materials have limited release periods and could affect the integrity of the material. Attempts to incorporate antimicrobial within mesoporous silica nanoparticles showed theoretical promise due to their physical robustness and large available internal volume, yet yielded short-term burst release and limited therapeutic payload. We have developed novel broad-spectrum antimicrobial drug-silica particles co-assembled for long-term release and high payload incorporated into dental adhesives. The release of the drug, octenidine dihydrochloride, is modulated by the oral degradative environment and mathematically modeled to predict effective service life. Steady-state release kills cariogenic bacteria, preventing biofilm formation over the adhesive surface, with no toxicity. This novel material could extend dental restoration service life and may be applied to other long-term medical device-tissue interfaces for responsive drug release upon bacterial infection. STATEMENT OF SIGNIFICANCE: This study describes a novel dental adhesive that includes a broad-spectrum antimicrobial drug-silica co-assembled particles for long-term antimicrobial effect. The release of the drug, octenidine dihydrochloride, is modulated by the oral degradative environment and mathematically modeled to predict effective release throughout the service life of the restoration. Steady-state drug-release kills caries-forming bacteria, preventing biofilm formation over the adhesive surface, without toxicity. This novel material could extend dental restoration service life and may be applied to other long-term medical device-tissue interfaces for responsive drug release upon bacterial infection. Since recurrent cavities (caries) caused by bacteria are the major reason for dental filling failure, this development represents a significant contribution to the biomaterials field in methodology and material performance.

A theranostic dental pulp capping agent with improved MRI and CT contrast and biological properties.

Different materials have been used for vital dental pulp treatment. Preferably a pulp capping agent should show appropriate biological performance, excellent handling properties, and a good imaging contrast. These features can be delivered into a single material through the combination of therapeutic and diagnostic agents (i.e. theranostic). Calcium phosphate based composites (CPCs) are potentially ideal candidate for pulp treatment, although poor imaging contrast and poor dentino-inductive properties are limiting their clinical use. In this study, a theranostic dental pulp capping agent was developed. First, imaging properties of the CPC were improved by using a core-shell structured dual contrast agent (csDCA) consisting of superparamagnetic iron oxide (SPIO) and colloidal gold, as MRI and CT contrast agent respectively. Second, biological properties were implemented by using a dentinogenic factor (i.e. bone morphogenetic protein 2, BMP-2). The obtained CPC/csDCA/BMP-2 composite was tested in vivo, as direct pulp capping agent, in a male Habsi goat incisor model. Our outcomes showed no relevant alteration of the handling and mechanical properties (e.g. setting time, injectability, and compressive strength) by the incorporation of csDCA particles. In vivo results proved MRI contrast enhancement up to 7weeks. Incisors treated with BMP-2 showed improved tertiary dentin deposition as well as faster cement degradation as measured by µCT assessment. In conclusion, the presented theranostic agent matches the imaging and regenerative requirements for pulp capping applications. STATEMENT OF SIGNIFICANCE: In this study, we combined diagnostic and therapeutic agents in order to developed a theranostic pulp capping agent with enhanced MRI and CT contrast and improved dentin regeneration ability. In our study we cover all the steps from material preparation, mechanical and in vitro characterization, to in vivo study in a goat dental model. To the best of our knowledge, this is the first time that a theranostic pulp capping material have been developed and tested in an in vivo animal model. Our promising results in term of imaging contrast enhancement and of induction of new dentin formation, open a new scenario in the development of innovative dental materials.

Assessment of curing behavior of light-activated dental composites using intensity correlation based multiple reference optical coherence tomography.

BACKGROUND AND OBJECTIVES: Monitoring the curing kinetics of light-activated resin is a key area of research. These resins are used in restorative applications and particularly in dental applications. They can undergo volumetric shrinkage due to poor control of the depth dependent curing process, modulated by the intensity and duration of the curing light source. This often results in the formation of marginal gaps, causing pain and damage to the restoration site. In this study, we demonstrate the capabilities of a correlation method applied using a multiple references optical coherence tomography (MR-OCT) architecture to monitor the curing of the resin. STUDY DESIGN/MATERIALS AND METHODS: A MR-OCT system is used in this study to monitor the curing of the resin. The system operates at the center wavelength of 1310 nm with an A-scan rate of 1200 A-scans per second. The axial and lateral resolution of the system is ∼13 µm and ∼27 µm. The method to determine the intensity correlation between adjacent B-frames is based on the Pearson correlation coefficient for a region of interest. Calculating the correlation coefficient for multiple B-frames related to the first B-frame at regular spaced time points, shows for a noncured resin a reduction of the correlation coefficient over time due to Brownian motion. The time constant of the reduction of the correlation value is a measure for the progress of the polymerization during LED light irradiation of the resin. The proposed approach is potentially a low-cost, powerful and unique optical imaging modality for measuring the curing behavior of dental resin and other resins, coatings, and adhesives in medical and industrial applications. RESULTS: To demonstrate the proposed method to monitor the curing process, a light-activated resin composite from GRADIA DIRECT ANTERIOR (GC Corporation, Japan) is studied. The curing time of resin was measured and monitored as a function of depth. The correlation coefficient method is highly sensitive to Brownian motion. The process of curing results in a change in intensity as measured by the MR-OCT signal and hence can be monitored using this method. CONCLUSIONS: These results show that MR-OCT has the potential to measure the curing time and monitor the curing process as a function of depth. Moreover, MR-OCT as a product has potential to be compact, low-cost and to fit into a smartphone. Using such a device for monitoring the curing of the resin will be suitable for dentists in stationary and mobile clinical settings.

Penetration of micro-filled infiltrant resins into artificial caries lesions.

OBJECTIVES: Infiltrants are non-filled low-viscosity resins that have been developed to arrest lesion progression by penetrating into the porosities of non-cavitated lesions where they are hardened and arrest lesion progression. The addition of fillers to infiltrant resin might combine the high penetrativity of the former with the better applicability of composite resins. The aim of the present study was to evaluate the penetration of different experimental micro-filled infiltrant resins (MFIRs) into artificial enamel lesions. METHODS: An infiltrant (Icon; DMG) was mixed with either one of three fillers [OF83: organic filler (83µm), OF42: organic filler (42µm) or GF0.7: glass filler (0.7µm)] reaching 35, 45 and 55% filler content, respectively. In each of 180 bovine enamel specimens three artificial lesions were created; two lesions were etched for 5s (37% H3PO4), leaving one lesion as control. Specimens were randomly allocated to 10 groups, in which either one of the MFIRs or the infiltrant was applied onto the two etched lesions for either 5s or 10s (n=18/group). Percentage of penetration (PP) was calculated and analysed. RESULTS: For both application times a significant influence of filler size but not of filler concentration on PP could be revealed (p<0.05; two-way ANOVA). PP of MFIRs-OF42 was not significantly different from unfilled infiltrant but significantly higher than those of OF83 and GF0.7 (p<0.05; two-way ANOVA). CONCLUSIONS: MFIRs-OF42 showed the ability to penetrate into artificial enamel caries lesions similar to the unfilled infiltrant resin. CLINICAL SIGNIFICANCE: MFIRs could provide a new micro-invasive treatment for small-cavitated lesions.

Transformação do sorriso por meio de fechamento de diastema utilizando resina composta nanoparticulada - relato de caso / Smile transformation through diastema closure using composite nanofilled - case report

A presença de diastema entre os dentes anteriores pode gerar desarmonia do sorriso e comprometer a estética do paciente. Com a evolução dos materiais e das técnicas restauradoras, o fechamento de diastema empregando resinas compostas tornou-se alternativa viável para resolução da maioria dos casos clínicos. Este tratamento permite restabelecer a função, possibilitando os contatos interproximais, bem como restabelecimento da estética, proporcionando um sorriso mais harmônico e agradável. Este artigo tem como objetivo relatar um caso clínico de correção de diastemas nos dentes anteriores superiores, utilizando resina composta nanoparticulada pela técnica direta para restabelecimento funcional e estético. O caso foi acompanhado por quatro anos, sendo realizados alguns reparos ao longo desse tempo, demonstrando que o fechamento de diastema com resina composta ‚ uma técnica viável e confiável, além de apresentar boa longevidade

The presence of anterior diastema can result on smile disharmony and compromise the patient’s aesthetic. The evolution of dental materials and techniques has made the use of composite resin for diastema closure a viable option treatment for most clinical cases. It restores function allowing the interproximal contacts, as well as harmony, reestablishing of the smile’s aesthetic. This clinical report aims at demonstrating the clinical correction of an anterior diastema restoring the functional anatomy and especially aesthetic through nanofilled composite resin restorations. The case was followed for 4-years and some repairs were carried out over this time, demonstrating the reliability and viability of the technique, with good longevity of the treatment

Sistemas de pulido de un o múltiples pasos de resinas compuestas hibridas y su alteración en la estabilidad del color y rugosidad superficial / One and multiple steps polishment system of hybrid resin composites and the color stability and surface roughness

El presente estudio evaluó la rugosidad y pigmentación de dos resinas compuestas nanohíbridas, Tetric EvoCeram (TE) y Ceram X Duo (CD) después del uso de dos técnicas de pulido: de paso único Pogo (P) y múltiples pasos Sof-Lex Discs (S). Sesenta especímenes fueron confeccionados con dimensiones de 7mm x 2mm, subdivididos en grupos (n=10): G1- TE+ P;G2- TE+S; G3- TE control; G4- CD + P;G5- CD + P; G6- CD control. Se realizó la toma de color a través de espectrofotómetro VITA Easyshade y lectura de la rugosidad superficial por el rugosímetro Surf-Corder. Los especímenes fueron inmersos en solución de café soluble por siete días, dejando dos especímenes de cada grupo almacenados en agua destilada durante el periodo del experimento. Después de ese tiempo, se realizó una nueva toma de color de los especímenes y los datos fueron analizados estadísticamente a través del test de Anova y Tukey. Para los dos sistemas de pulido hubo diferencia estadísticamente significante en relación a las dos resinas compuestas (p<0,05). El grupo control presentó superficies más lisas que las demás, mientras que en los especímenes pulidos con sistema Sof-Lex presentaron superficies más lisas que las pulidas con Pogo. Los especímenes pulidos con sistema de "múltiples pasos" obtuvieron valores menores de variación de color (?E*), mientras que las muestras tratadas con tira de poliéster fueron las que más se pigmentaron. Cuando se comparan las dos técnicas de pulido, la técnica de múltiples pasos resultó tener una mayor lisura superficial y menor variación de color.

This study compared two different nanohybrid composite resins, Tetric EvoCam and Ceram X Duo about its roughness and staining, after two polishing techniques, "one step" Pogo and "multiple steps" Sof-Lex Disc. Sixty test-samples were fabricated with dimensions of 7mm x 2mm, divided into groups: (n=10): G1- TE+ P;G2- TE+S; G3- TE control; G4- CD + P;G5- CD + P; G6- CD control. A color check was performed with VITA Easyshade spectrophotometer and a reading of the surface roughness by the Surf-Corder (Kosaka Lab. SE 1700). So, the specimens were immersed in a solution of solved coffee (Nescafe) for seven days, with two specimens of each group stored in distilled water during the study period. After this period, it was performed another color check of the specimens and the data was statistically analyzed by ANOVA and Tukey test. For both polishing systems there was statistically significant differences, on both resin composites (p<0.05). The control group showed smoother surfaces than the others, while that the ones polished with Sof-Lex presented smoother surfaces than the ones polished with the Pogo system. The specimens polished with the "multiple steps" system had lower values of color variation (?E*), while that the specimens treated with polyester strips were the most stained ones. When comparing the two polishing techniques, the technique of "multiples steps" resulted in greater smoothness surface and less color variation.

Degradation resistance of silorane, experimental ormocer and dimethacrylate resin-based dental composites.

There are several degradation mechanisms of resin-composite restorations and possible deleterious effects created by leached components cannot be ignored. Additionally, the surface integrity influences the long-term clinical performance of resin-composite restorations and can be affected by several factors. Novel technologies have been proposed, but there is a lack of information considering the degradation resistance of such materials. The aim of this study was to investigate the degradation resistance of silorane (SIL), pure-ormocer (ORM) and dimethacrylate (ELS and GRD) resin-based dental composites. Water sorption and solubility tests were adapted from ISO4049, color change trough the CIELab parameters after 24h and 30d immersion in distilled water. Knoop hardness readings were performed at the aforementioned periods and the percentage of hardness decrease was considered. Results were analyzed with one-way ANOVA followed by Tukey's test (P = 0.05). SIL and GRD produced lower water sorption than ORM and ELS. SIL presented the lowest solubility. All materials demonstrated acceptable results for color stability. SIL demonstrated the more stable surface, when considering surface hardness, in aqueous environment. It can be concluded that i) silorane and ormocer-based materials did not produced higher color stability than dimethacrylates in distilled aqueous media; and ii) silorane-based materials exhibited lower water solubility and lower hardness decreases after water immersion than dimethacrylate-based resin-composites, while the pure-ormocer-baed material not.

Tissue response and biodegradation of composite scaffolds prepared from Thai silk fibroin, gelatin and hydroxyapatite.

This work aimed to investigate tissue responses and biodegradation, both in vitro and in vivo, of four types of Bombyx mori Thai silk fibroin based-scaffolds. Thai silk fibroin (SF), conjugated gelatin/Thai silk fibroin (CGSF), hydroxyapatite/Thai silk fibroin (SF4), and hydroxyapatite/conjugated gelatin/Thai silk fibroin (CGSF4) scaffolds were fabricated using salt-porogen leaching, dehydrothermal/chemical crosslinking and an alternate soaking technique for mineralization. In vitro biodegradation in collagenase showed that CGSF scaffolds had the slowest biodegradability, due to the double crosslinking by dehydrothermal and chemical treatments. The hydroxyapatite deposited from alternate soaking separated from the surface of the protein scaffolds when immersed in collagenase. From in vivo biodegradation studies, all scaffolds could still be observed after 12 weeks of implantation in subcutaneous tissue of Wistar rats and also following ISO10993-6: Biological evaluation of medical devices. At 2 and 4 weeks of implantation the four types of Thai silk fibroin based-scaffolds were classified as "non-irritant" to "slight-irritant", compared to Gelfoam(®) (control samples). These natural Thai silk fibroin-based scaffolds may provide suitable biomaterials for clinical applications.

Biodegradation of resin-dentin interfaces increases bacterial microleakage.

Bis-GMA-containing resin composites and adhesives undergo biodegradation by human-saliva-derived esterases, yielding Bis-hydroxy-propoxy-phenyl-propane (Bis-HPPP). The hypothesis of this study is that the exposure of dental restorations to saliva-like esterase activities accelerates marginal bacterial microleakage. Resin composites (Scotchbond, Z250, 3M) bonded to human dentin were incubated in either buffer or dual-esterase media (pseudocholinesterase/cholesterol-esterase; PCE+CE), with activity levels simulating those of human saliva, for up to 90 days. Incubation solutions were analyzed for Bis-HPPP by high-performance liquid chromatography. Post-incubation, specimens were suspended in a chemostat-based biofilm fermentor cultivating Streptococcus mutans NG8, a primary species associated with dental caries, for 7 days. Bacterial microleakage was assessed by confocal laser scanning microscopy. Bis-HPPP production and depth and spatial volume of bacterial cell penetration within the interface increased with incubation time and were higher for 30- and 90-day PCE+CE vs. buffer-incubated groups, suggesting that biodegradation can contribute to the formation of recurrent decay.

Study on a novel copper-containing composite for contraception.

BACKGROUND: The copper-containing intrauterine devices (Cu-IUDs) are being increasingly used worldwide as an effective contraception for family planning. To avoid abnormal bleeding, pain, partial and complete expulsion, which are associated with the burst release of cupric ions during the first few days, a novel cross-linked composite based on polyvinyl alcohol (PVA) that contained cupric ions, but not metallic copper, was developed by our research team. STUDY DESIGN: As a logical extension of our previous work, the corrosion products and release behavior of this composite after immersing in simulated body fluid (SBF) for 1 year were studied by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD) and atomic absorption spectrophotometry (AAS). RESULTS: No other new elements, such as P, Cl and Ca, appeared on the surface of the composite, and no Cu(2)O was formed after immersing in SBF for 1 year, indicating that the effectiveness of copper can be greatly improved. Furthermore, no significant change on time dependence was found for the release rates of cupric ions in the composite compared with that of metallic copper, suggesting the absent burst release of cupric ions in the composite. CONCLUSION: The present in vitro long-term data suggest that this novel copper-containing composite has potential as a substitute for conventional materials used in the manufacture of IUDs.

Effect of filler level and particle size on dental caries-inhibiting Ca-PO(4) composite.

Secondary caries and restoration fracture are common problems in restorative dentistry. The aim of this study was to develop Ca-PO(4) nanocomposite having improved stress-bearing properties and Ca and PO(4) ion release to inhibit caries, and to determine the effects of filler level. Nanoparticles of dicalcium phosphate anhydrous (DCPA), two larger DCPA powders, and reinforcing whiskers were incorporated into a resin. A 6 x 3 design was tested with six filler mass fractions (0, 30, 50, 65, 70, and 75%) and three DCPA particle sizes (112 nm, 0.88 mum, 12.0 mum). The DCPA nanocomposite at 75% fillers had a flexural strength (mean +/- SD; n = 6) of 114 +/- 23 MPa, matching the 112 +/- 22 MPa of a commercial non-releasing, hybrid composite (P > 0.1). This was 2-fold of the 60 +/- 6 MPa of a commercial releasing control. Decreasing the particle size increased the ion release. Increasing the filler level increased the ion release at a rate faster than being linear. The amount of ion release from the nanocomposite matched or exceeded those of previous composites that released supersaturating levels of Ca and PO(4) and remineralized tooth lesions. This suggests that the much stronger nanocomposite may also be effective in remineralizing tooth lesion and inhibiting caries. In summary, combining calcium phosphate nanoparticles with reinforcing co-fillers in the composite provided a way to achieving both caries-inhibiting and stress-bearing capabilities. Filler level and particle size can be tailored to achieve optimal composite properties.

Excretion of dental resin monomers and metabolic intermediates via urine in guinea pigs.

OBJECTIVE: Monomers like BisGMA (Bisphenol-A-glycidyldimethacrylate) and comonomers like TEGDMA (triethyleneglycoldimethacrylate) are used in dental restorative materials in order to build up the three-dimensional network of filling materials. Since earlier investigations revealed uptake and subsequent metabolism of unpolymerized remainders of (co)monomers, the present experiment investigates the metabolic urine pattern of guinea pigs (n=4) after application of TEGDMA or BisGMA (each dose=0.02 mmol/kg body weight=100%), respectively. METHODS: For the investigations BisGMA was pre-dissolved in DMSO and subsequently diluted with 0.9% NaCl solution (final DMSO concentration 1%) and TEGDMA was dissolved in 0.9% NaCl solution. The solutions were administered with a gastric tube into the animals. Control animals received either 0.9% NaCl or 0.9% NaCl solution with 1% DMSO solution. RESULTS: After 24h in collected urine the following metabolites were identified. After administration of TEGDMA (mean relative concentration of administered substances)+/-s.d. [%]; n=4): unchanged TEGDMA: 12+/-1.5%, MA: 2.4+/-0.8%, and triethyleneglycol: 35+/-2.2%. After administration of BisGMA (mean+/-s.d. [%]; n=4): unchanged BisGMA: 11.4+/-2.7%, MA: 2.2+/-0.6%, and bisphenol-A-bis(2,3-dihydroxypropyl)ether: 60.1+/-5.2%). CONCLUSION: No further metabolites like the previously identified intermediate 2,3-epoxymethacrylic acid and derived reaction products were identified in the urine, indicating that these metabolites must have reacted further.

Influência da distância de fotoativação na microdureza, sorção, solubilidade e estabilidade de cor de uma resina composta microhíbrida / Influence of light curing tip distance on microhardness, water sorption, solubility and color stability of a microhybrid resin composite

O objetivo deste trabalho foi avaliar a influência da distância de fotoativação na microdureza Knoop, na sorção, na solubilidade e na estabilidade de cor de uma resina composta microhíbrida (Filtek Z250 3M ESPE). Os corpos-de-prova foram confeccionados em uma matriz de teflon (6,0mm x 2,5mm espessura) e fotoativados por 20s variando-se a distância entre a ponta do aparelho fotoativador e a superfície da resina composta: G1- 0mm (controle), G2- 5mm, G3- 10mm, G4- 15mm. Em seguida, os espécimes foram armazenados secos em recipientes escuros por 24h. O teste de microdureza Knoop (100g por 15s) foi realizado nas superfícies topo e base dos espécimes após 24h, 6 meses e 1 ano. Para o teste de sorção e solubilidade, os espécimes foram colocados no dessecador para obtenção da massa inicial, armazenados em água até uma massa constante e novamente submetidos ao processo de dessecamento até a obtenção de uma massa constante. Para o teste de estabilidade de cor, após a medida de cor inicial realizada com um espectrofotômetro, os espécimes foram diariamente submetidos a dois ciclos de 10 minutos de imersão no suco de uva, permanecendo o restante do tempo em água. Os espécimes do grupo controle ficaram imersos em água ao longo de todo o período experimental (28 dias). A cor foi mensurada semanalmente. Os dados de microdureza e estabilidade de cor foram submetidos aos testes estatísticos ANOVA a 3 critérios/Tukey e os de sorção e solubilidade a ANOVA um critério/Tukey ('alfa'=0,05). Após 24h, o G4 apresentou valores significativamente menores de dureza comparados ao G1 na superfície topo, enquanto que na base, a dureza do G2, G3 e G4 foi estatisticamente menor que G1. Ambas as superfícies avaliadas mostraram redução nos valores de microdureza após 6 meses e 1 ano. G3 e G4 apresentaram maior sorção de água e G4 maior solubilidade, comparado a G1. A estabilidade de cor do compósito foi influenciada pelo tempo, meio de imersão e pela distância de fotoativação. O suco de uva...

The purpose of this in vitro study was to evaluate the influence of light curing tip distance on microhardness, sorption, solubility and color stability of a microhybrid resin composite (Filtek Z250-3M ESPE). Specimen discs (6mm x 2,5mm) were irradiated for 20s with a continuous output at 640mW/cm2, according to different curing tip distances: G1-0mm (control), G2-5mm, G3-10mm and G4-15mm. Specimens were stored dry in a lightproof container for 24h. Knoop hardness measurements were obtained on the top and bottom surfaces of the samples (100g, 15s) after 24h, 6 and 12 months. To evaluate sorption and solubility, specimens were desiccated to be weighed and then stored in distilled water until a constant mass was obtained. The reconditioning in the desiccators was also done until a constant mass. To evaluate de color stability of the resin composite, the first color measurements were made and then specimens were immersed in a grape juice twice a day for 10 minutes, during 28 days. Control groups were immersed in distilled water for the same period of time. Color measurements were made weekly using a spectrophotometer. Data from microhardness/color stability and from water sorption/solubility were submitted to three-way ANOVA/Tukey and one-way ANOVA/Tukey tests, respectively (p < 0,05). For top and bottom surfaces, there were statistical differences among the curing tip distances after 24h. Although, the microhardness values were lower for both surfaces after 6 and 12 months. G3 and G4 showed significant higher water sorption and G4 higher solubility when compared to G1. Grape juice showed significant color change of the resin composite as a function curing tip and resin composite surface decreases microhardness and color stability, and increases sorption and solubility of the evaluated resin composite.

The penetration of RealSeal primer and Tubliseal into root canal dentinal tubules: a confocal microscopic study.

AIM: To compare penetration depth into dentinal tubules of RealSeal with that of a well-established endodontic sealer (Tubliseal) by means of confocal microscopy. METHODOLOGY: Twenty sound extracted, single-rooted premolars were selected. Following completion of root canal instrumentation, the teeth were divided into two groups using a stratified sampling method, ranking teeth according to size. In group 1, 10 teeth were filled with Gutta-percha and Tubliseal using cold lateral condensation. In group 2, 10 teeth were filled with RealSeal. Both sealers were labelled with Rhodamine B dye. The teeth were sectioned parallel to their long axis resulting in 20 specimens per group. Confocal microscopy was used to assess the penetration depths of the sealers at three sites for each specimen (coronal, middle and apical). Data were analysed statistically using Stata Release 9.1. RESULTS: The penetration depth of RealSeal in each one of the thirds of the root canal was found to be higher than that of Tubliseal (P < 0.05). The penetration depths of the two sealers was found to be significantly different (P = 0.001). The mean penetration value for the RealSeal group was 908.8 microm whereas the mean value for the Tubliseal group was 139.5 microm. CONCLUSIONS: The penetration depth of RealSeal into the root dentinal tubules is significantly greater than that of Tubliseal.

A mathematical model for predicting controlled release of bioactive agents from composite fiber structures.

A mathematical model for predicting bioactive agent release profiles from core/shell fiber structures was developed and studied. These new composite fibers, which combine good mechanical properties with desired protein release profiles, are designed for use in tissue regeneration and other biomedical applications. These fibers are composed of an inner dense polymeric core surrounded by a porous bioresorbable shell, which encapsulates the bioactive agent molecules. The model is based on Fick's second law of diffusion, and on two major assumptions: (a) first-order degradation kinetics of the porous shell, and (b) a nonconstant diffusion coefficient for the bioactive agent, which increases with time because of degradation of the host polymer. Three factors are evaluated and included in this model: a porosity factor, a tortuosity factor, and a polymer concentration factor. Our study indicates that the model correlates well with in vitro release results, exhibiting a mean error of less than 2.2% for most studied cases. In this study, the model was used for predicting protein release profiles from fibers with shells of various initial molecular weights and for predicting the release of proteins with various molecular weights. This new model exhibits a potential for simulating fibrous systems for a wide variety of biomedical applications.

Genetic and cellular toxicology of dental resin monomers.

Monomers are released from dental resin materials, and thus cause adverse biological effects in mammalian cells. Cytotoxicity and genotoxicity of some of these methacrylates have been identified in a vast number of investigations during the last decade. It has been well-established that the co-monomer triethylene glycol dimethacrylate (TEGDMA) causes gene mutations in vitro. The formation of micronuclei is indicative of chromosomal damage and the induction of DNA strand breaks detected with monomers like TEGDMA and 2-hydroxyethyl methacrylate (HEMA). As a consequence of DNA damage, the mammalian cell cycle was delayed in both G1 and G2/M phases, depending on the concentrations of the monomers. Yet, the mechanisms underlying the genetic and cellular toxicology of resin monomers have remained obscure until recently. New findings indicate that increased oxidative stress results in an impairment of the cellular pro- and anti-oxidant redox balance caused by monomers. It has been demonstrated that monomers reduced the levels of the natural radical scavenger glutathione (GSH), which protects cell structures from damage caused by reactive oxygen species (ROS). Depletion of the intracellular GSH pool may then significantly contribute to cytotoxicity, because a related increase in ROS levels can activate pathways leading to apoptosis. Complementary, cytotoxic, and genotoxic effects of TEGDMA and HEMA are inhibited in the presence of ROS scavengers like N-acetylcysteine (NAC), ascorbate, and Trolox (vitamin E). Elevated intracellular levels of ROS can also activate a complex network of redox-responsive macromolecules, including redox-sensitive transcription factors like nuclear factor kappaB (NF-kappaB). It has been shown that NF-kappaB is activated probably to counteract HEMA-induced apoptosis. The induction of apoptosis by TEGDMA in human pulp cells has been associated with an inhibition of the phosphatidylinositol 3-kinase (PI3-K) cell-survival signaling pathway. Although the details of the mechanisms leading to cell death, genotoxicity, and cell-cycle delay are not completely understood, resin monomers may be able to alter the functions of the cells of the oral cavity. Pathways regulating cellular homeostasis, dentinogenesis, or tissue repair may be modified by monomers at concentrations well below those which cause acute cytotoxicity.

Controlled release of chlorhexidine from UDMA-TEGDMA resin.

Chlorhexidine salts are available in various formulations for dental applications. This study tested the hypothesis that the release of chlorhexidine from a urethane dimethacrylate and triethylene glycol dimethacrylate resin system can be effectively controlled by the chlorhexidine diacetate content and pH. The filler concentrations were 9.1, 23.1, or 33.3 wt%, and the filled resins were exposed to pH 4 and pH 6 acetate buffers. The results showed that Fickian diffusion was the dominant release mechanism. The rates of release were significantly higher in pH 4 buffer, which was attributed to the increase of chlorhexidine diacetate solubility at lower pH. The higher level of filler loading reduced the degree of polymerization, leading to a greater loss of organic components and higher chlorhexidine release rates.

Susceptibilidad a la degradación de un material de obturación de conductos radiculares basado en una policaprolactona. I. Hidrólisis alcalina / Susceptibility of a polycaprolactone-based root canal filling material to degradation. I. Alcaline hydrolisis

La policaprolactona, unpoliéster alifático termoplástico, se ha mostrado susceptible tanto a la hidrólisis alcalina y enzimática. Este estudio de screening examinó la susceptibilidad a la hidrólisis alcalina del Resilon, un composite de obturación de conductos basado en policaprolactona. se prepararon discos de 15 mm de diámetro de Resilon y gutapercha Obtura, preparadas por compresión en moldes y sumergidas en etóxido de sodio de 20 a 60 minutos. Los discos de control se sumergieron en etanol durante 60 minutos. Estos discos se examinarion empleando microscopia electrónica de barrido de campo de emisión y análisis de rayos X de energía dispersiva. Para el Resilon, el componente resinoso de superficie se hidrolizó tras 20 minutos de inmersión en etóxido de sodio, exponiendo el polímero esferulítico y los rellenos de oxicloruro de bismuto y vidrio subsuperficial. Se produjo una erosión más severa tras 60 min de tratamiento con etóxido de sodio. La gutapercha no se afectó tras la inmersión en el etóxido de sodio. como el Resilon es susceptible con la hidrólisis alcalina, es posible que se produzca la hidrólisis enzimática. La biodegradación del Resilon por enzimas bacterianos/salivales y bacterias relevantes en endodoncia requiere más investigación

Polycaprolactone, a thermoplastic aliphatic polyester, is reportedly susceptible to both alkaline and enzymatic hydrolyzes. This screening study examined the susceptibility of Resilon, a polycaprolactone-based root filling composit, to alkaline hydrolisis. There were 15 mm diameter disks of Resilon and Obtura gutta-percha prepared by comprenssive molding and immersed in 20% sodium ethoxide for 20 or 60 min. Control disks were immersed in ethanol for 60 min. These disks were examined using field-emission scanning electron microscopy and energy dispersive X-ray analysis. for Resilon, the surface resinous component was hydrolyzed after 20 min of sodium ethoxide immersion, exposing the spherulitic polymer structure and subsurface glass and bismuth oxyclorhide fillers. More severre erosion occurred after 60 min of sodium ethoxide treatment. Gutta-percha was unaffected after immersion in sodium ethoxide. As Resilon is susceptible to alkaline hydrolysis, it is possible that enzymatic hydrolysis may occur. Biodegradation of Resilon by bacterial/salivary enzymes and edodontically relevant bacteria warrants further investigation

[The penetration of various adhesives into early enamel lesions in vitro]. / Penetration verschiedener Adhäsive in initiale Schmelzläsionen in vitro.

The aim of the present study was to evaluate the penetration depth (PD) and the thickness of the oxygen inhibition layer (OIL) of a fissure sealant (Helioseal, Vivadent) and various adhesives (Heliobond, Excite, Vivadent; Resulcin, Merz; Solobond M, Voco; Prompt L-Pop, 3M-Espe) applied to enamel lesions in vitro. From 27 bovine teeth 54 enamel specimens were prepared and covered with nail varnish (control) thus obtaining three windows for treatment. After demineralisation (pH 5.0, 14 d) two of the windows were etched with phosphoric acid (20%, 5 s), whereas the third area served as control. The specimens were divided randomly into six groups (n = 9) and the respective adhesive was applied (90 s), either once or twice. Light-curing followed each application. Enamel slabs (perpendicular to the surface) were cut and studied after infiltration with a fluorescent low-viscous resin using confocal microscopy (CLSM). The image of the lesion was divided into two areas with different grey values. Lesion depths were calculated (ImageJ) from the surface to that point in the lesion where the grey value clearly changed to a darker grey value. The zone with the darker grey values marked the front of demineralisation. Mean lesion depths (+/- SD) after demineralisation were measured at 105 (+/- 21) microm. After single application, Resulcin [89 (+/- 22)%] and Helioseal [98 (+/- 6)%] had almost completely penetrated the lesion. Heliobond [126 (+/- 33)%] and Excite [184 (+/- 40)%] penetrated even deeper than the defined lesion. For Excite double application decreased the OIL significantly (p = 0.03; adjusted paired t-test). Adhesives are capable to penetrate artificial initial enamel lesions completely. Follow-up studies are needed to confirm this effect for natural lesions.