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  • 1
    Electronic Resource
    Electronic Resource
    Initial versus subsequent release of elements from dental casting alloys (1999)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 26 (1999), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The release of elements from dental casting alloys is directly related to adverse biological effects they may have. Longer-term (〉1 month) studies of elemental release have suggested that release decreases significantly after a higher initial release of elements. The aim of the current study was to measure the release of elements from a variety of clinically relevant dental casting alloys and compare the release at weekly intervals through 4 weeks. The hypothesis was that the release during the initial week should be higher than in subsequent weeks, and that cytotoxicity should decrease as elemental release decreases. Alloy samples were exposed to cell-culture medium which was changed at weekly intervals and assessed for elemental release by means of atomic absorption spectrometry. The cytotoxicity of the medium was also measured. The results showed that for single phase alloys, initial release was often significantly higher in the first weeks than in subsequent weeks, but not for all elements in an alloy. Multiple phase alloys showed steady or increasing release relative to the first week. Cytotoxicity relationships were complex depending on which elements were released and the ratios of elements released. This study suggests that short-term tests (〈1 week) may not be appropriate to evaluate longer-term elemental release or cytotoxicity because of changing rates of elemental release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2842.1999.00455.x
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  • 2
    Electronic Resource
    Electronic Resource
    Materials for endosseous dental implants (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of oral rehabilitation 23 (1996), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: summary The goal of placement of endosseous dental implants is to achieve osseointegration or biointegration of the bone with the implant. A wide variety of materials has been used for these implants, but only a few promote osseointegration and biointegration. Titanium and titanium alloy (TJ6A14V) have been the most widely used of these materials. The surface oxide of titanium appears to be central to the ability of this material to osseointegrate. The oxide limits dissolution of elements and promotes the deposition of biological molecules which allow bone to exist as close as 30 å to the surface of the implant. The details of the ultrastructure of the gap between the implant and bone remain undefined, and the consequences of elements which are released on the interface over time are not known. These areas of investigation are particularly important in defining the differences between commercially pure titanium implants and those made of titanium, aluminium and vanadium. The epithelial interface between the gingiva and titanium appears to contain many of the structural characteristics of the native tooth-gingiva interface, but details are still vague. The connective tissue interface with the titanium appears to be one of tightly fitting tissues rather than adhesion. Ceramic coatings appear to improve the ingrowth of bone and promote chemical integration of the implant with the bone. The characteristics of these coatings are complex and affect the bony response, but the mechanisms remain obscure. The degradation of the coatings is an issue of particular controversy. Progress in dental implantology is likely to continue as the interface between the material and bone is more clearly understood, and biological molecules and artificial tissues are developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2842.1996.tb01214.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of dental metal ions on glutathione levels in THP-1 human monocytes (2000)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 27 (2000), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The release of metal ions from dental restorations has been well established, but the sublethal effects of these ions on oral tissues remain undefined. Metal ions are a potential cause of sublethal oxidative stress in cells. Oxidative stress is known to alter cellular processes which are important in the inflammation of tissues. The presence of oxidative stress is commonly assessed by measuring the oxidized (GSSG) and reduced (GSH) forms of cellular glutathione. Normally, the majority of cellular glutathione exists as GSH and the GSH–GSSG ratio is high. Since monocytes often orchestrate inflammatory responses, oxidative stress in monocytes is important. Our hypothesis for the current work was that metal ions induce oxidative stress in monocytes which is manifested by a lower GSH–GSSG ratio. Human THP-1 monocytes were exposed for 24 h to sublethal concentrations of ions of Ag, Be, Co, Cu, Hg, Ni, Pd, and Zn – all known to be released from dental biomaterials. GSH and GSSG were measured using colorimetric assays. Cu lowered the GSH–GSSG ratio as hypothesized, but the ratio could not be determined for other metals because other metal ions interfered with the GSSG assay. However, a statistically significant ( anova/Tukey) increase in GSH per cell was observed upon exposure to Ag (50%), Co (100%), Hg (250%) and Zn (10%). This increase may be indicative of an oxidative stress in its own right. Alterations in GSH levels may be important to how released metal ions alter cytokine secretion from monocytes and other cells which play a role in the inflammatory response to dental biomaterials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2842.2000.00547.x
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  • 4
    Electronic Resource
    Electronic Resource
    Future directions in bonding resins to the dentine-pulp complex (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 31 (2004), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: summary  Resin-based materials are rapidly becoming the primary restorative material to replace tooth structure and the low percentage of biological problems reported for resin-based restorations is testimony to their relative biocompatibility. Despite considerable advances in the understanding of the mechanisms, which govern the integration of resin composite materials with the dentine–pulp complex, considerable potential for improvement remains. Most of these improvements centre around a better understanding of the biological and microbiological risks of resin materials and will only be possible with improved in vitro and in vivo models. There are also a number of possible future developments in materials, clinical techniques and diagnostic methods that may improve the long-term success and reliability of resin-based restorations. The remainder of this paper describes the most likely avenues for future improvements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2842.2003.01258.x
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  • 5
    Electronic Resource
    Electronic Resource
    Cytotoxicity of commercial and novel binary titanium alloys with and without a surface-reaction layer (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 31 (2004), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Titanium-based alloys form a surface reaction layer when cast. This study investigated the effect of the surface reaction layer on the cytotoxicity of novel Ti-based binary alloys. The cytotoxicities of the novel alloys were compared with commercially pure titanium, Ti-6Al-4V and Ti-6Al-7Nb. Cast discs with or without the reaction layer were first tested for cytotoxicity, then for elemental release into cell-culture medium. The elements released into the extracts were measured by means of an inductively coupled plasma atomic emission spectrometer. The commercial and novel binary Ti-based alloys showed no statistically significant cytotoxicity, although some trends were noted for several alloys. The presence of the reaction layer did not significantly alter the cytotoxicity. These favourable biocompatibility results show that these novel alloys have promise for use in dental restorations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0305-182X.2003.01083.x
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  • 6
    Electronic Resource
    Electronic Resource
    Ag, Cu, Hg and Ni ions alter the metabolism of human monocytes during extended low-dose exposures (2002)
    Oxford UK : Blackwell Science Ltd
    Journal of oral rehabilitation 29 (2002), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The monocyte and macrophage play an important role in the biological response to dental biomaterials. However, the effects of low-level, extended exposures of monocytes to metal ions which are known to be released from dental alloys is not known. Thus, in the current study we characterized the metabolic activity of monocytes in the presence of low doses of Ag, Cu, Hg and Ni ions for up to 4 weeks. THP-1 human monocytes were exposed in vitro to concentrations of metal ions at 1–10% of those known to be lethal during 24 h exposures. Mitochondrial function [succinic dehydrogenase (SDH) activity] and total cellular protein [bicinchoninic acid (BCA) assay] were assessed at weekly intervals during metal exposure. Each metal ion caused a unique pattern of effects from the monocytes. These effects were sometimes delayed until several weeks into the exposure (Cu, Ni). Large increases in total protein or SDH activity per cell were observed (Cu 150%, Hg 40–60%, Ni 50%), but these increases were always transient. The differences between concentrations with minimal effects and those which were lethal (8 versus 12 μmol L–1 for Ag, 1Ã0 versus 1Ã5 μmol L–1 for Hg) were small. Finally, concentrations which caused total suppression of cellular activity were sometimes preceded by an increased activity (Hg, Ni). We concluded that metal ions alter monocyte metabolic activity during extended exposures in vitro, but that the concentrations required are often near long-term lethal levels. Clinically, these results imply that the levels of metals released from dental alloys may be significant to monocytic function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2842.2002.00845.x
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  • 7
    Electronic Resource
    Electronic Resource
    Human peripheral blood monocytes versus THP-1 monocytes for in vitro biocompatibility testing of dental material components (2002)
    Oxford UK : Blackwell Science Ltd
    Journal of oral rehabilitation 29 (2002), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Monocytes play a central role in the response of tissues to biomaterials. Monocytic cell lines such as the THP-1 cell line have been used extensively as models for primary monocytes (directly from blood) in biocompatibility research. However, little information exists about the appropriateness of these cell lines as models. Thus, the current study compared the biological response of both primary peripheral blood monocytes (PBMs) and the THP-1 cell line to four common components of dental materials known to be released into the oral environment: nickel ions, 2-hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA), and 2,2-bis[4(2-hydroxy-3-methacryloloxy)-phenyl]propane (Bis-GMA). Comparisons were made by constructing dose–response curves for each type of monocyte and the four components. The 50% cytotoxicity values (TC50 values) were then statistically compared. In addition, the response of the monocytes to the materials with and without lipopolysaccharide (LPS) stimulation were assessed by measuring TNF-α secretion from the monocytes. The results showed that the PBMs were 5–10 times less sensitive than the THP-1 monocytes to these dental components, but that both cell lines ranked the components identically. TNF-α secretion from both types of monocytes often showed similar trends, although some inconsistent results were noted. The current study supports the use of THP-1s as a model for ranking the cytotoxicity of components of dental biomaterials. Furthermore, the secretory activity of PBMs appears to be generally well represented by the THP-1s. However, sufficient differences between these cell types exist to recommend confirmation of any critical results obtained with THP-1s using PBMs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2842.2002.00893.x
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  • 8
    Electronic Resource
    Electronic Resource
    Long-term cytotoxicity of resin-based dental restorative materials (2002)
    Oxford UK : Blackwell Science Ltd
    Journal of oral rehabilitation 29 (2002), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Highly filled composites, Ormocers (organically modified ceramics) and ‘smart’ materials have been developed to overcome the polymerization shrinkage problems of conventional composite materials. The purpose of the current study was to investigate the effect of longer-term (up to 8 weeks) ageing of these resin-based dental restorative materials and determine the effect of post-curing on cytotoxicity. Twelve discs of each material (Colombus/IDR, Definite/Degussa, Ariston pHc/Vivadent) were either light-cured (Lc) or light-cured and post-cured (Pc). For cytotoxicity testing, the discs were placed in contact with cell culture medium (DMEM) and incubated at 37 °C. Extracts from composite materials were collected after 24 h and weekly over a time period of 8 weeks. Cytotoxicity of the eluates to cultured fibroblasts (Balb/c3T3) were measured by the succinic dehydrogenase (SDH) activity (MTT assay) and the results expressed in percentage of negative controls (Teflon discs). The results showed that ageing significantly influenced the cytotoxicity of the materials. Except for Ariston pHc, materials were less cytotoxic after 8 weeks of ageing than they were in early intervals and post-curing was not generally useful in reducing cytotoxicity. The Ariston pHc was initially moderately toxic, but then become highly cytotoxic for 5 weeks before returning to initial levels. The current study demonstrated the importance of assessing the cytotoxicity of resin composite materials at multiple times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2842.2002.00804.x
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  • 9
    Electronic Resource
    Electronic Resource
    In vitro cytotoxicity of dental casting alloys over 8 months (1999)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 26 (1999), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Although in vitro cytotoxicity tests have been a valuable part of the biological testing of dental casting alloys, these tests are generally limited by their short-term nature (≪168 h). The objective of the current study was to measure the in vitro cytotoxicity of representative types of dental casting alloys over a relatively long-term interval (months) and compare longer-term cytotoxicity with that seen initially. Polished casting alloy samples were exposed to cell-culture medium for 30-day intervals. During the last 3 days of each interval, the medium was changed to provide a 3-day extract which was then placed on fibroblast or macrophage cultures for 48 h. The mitochondrial activity of the cells was measured and compared to control cultures to assess the cytotoxic effect of the alloys. The cytotoxic effect was plotted versus time of medium exposure. The total time of exposure was 8 months. For most alloys, the mitochondrial response was constant over the 8 months, indicating that the cytotoxic effect of the alloys did not change significantly after extended exposure to the medium. A trend of improving biological response was suspect for a reduced-gold alloy, but this trend was not statistically significant. The mitochondrial activity of the macrophages was less sensitive to the alloy extracts than the activity of the fibroblasts, which was significantly suppressed for several alloy types. However, mitochondrial activity of the macrophages was significantly increased for several alloys in the early time intervals. The total noble metal content of the alloys was not necessarily predictive of the biological response. Thus, it appears that in this indirect test of in vitro cytotoxicity, the short-term cytotoxicity is predictive of the longer-term for many types of dental casting alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2842.1999.00398.x
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of enamel matrix protein application on the viability, proliferation, and attachment of human periodontal ligament fibroblasts to diseased root surfaces in vitro (2003)
    Oxford, UK : Munksgaard International Publishers
    Journal of clinical periodontology 30 (2003), S. 0 
    Details
    ISSN: 1600-051X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objectives: The purpose of this research was to examine the influence of enamel matrix proteins (EMP) on the viability, proliferation, and attachment of periodontal ligament fibroblasts (PDLF) to diseased root surfaces.Materials and Methods: Primary cell cultures of PDFL were obtained from clinically healthy third molars or premolar teeth. Viability and proliferation rates were carried out over a 10-day period. A total of 80,000 cells were plated in 24-well plates followed by EMEM with 10% FBS (positive control) and EMEM plus EMP at 25, 50, 75, and 100 μg/ml. Cells were harvested on days 1, 3, 5, 7, and 10 and viability was performed utilizing an MTS assay. PDLF proliferation rates were assessed by a CyQUANT GR dye assay. SEM analysis was used to examine the qualitative effects of cellular attachment to diseased root surfaces following EMP compared to nontreated controls.Results: The results indicated that viability was negatively affected for higher doses over time while lower doses displayed viability effects similar to control. Proliferation, however, appeared to be ameliorated following exposure to EMP. The SEM analysis suggests that cellular attachment to diseased dentin was enhanced following EMP application.Conclusion: These in vitro studies support the concept that EMP may act as a suitable matrix for PDLF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-051X.2003.00150.x
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