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Biomedical subjects

John C Wataha

Publications and source records attributed to John C Wataha.

At least 19 recordsLinked to original sources
PubMed2006

Sublethal concentrations of diverse gold compounds inhibit mammalian cytosolic thioredoxin reductase (TrxR1).

UNLABELLED: Thioredoxin reductase (TrxR) reduces thioredoxin (Trx), thereby contributing to cellular redox balance, facilitating the synthesis of deoxy-ribose sugars for DNA synthesis, and regulating redox-sensitive gene expression. Auranofin is a gold compound that potently inhibits TrxR. This inhibition is one suspected mechanism of auranofin's therapeutic benefit in the treatment of rheumatoid arthritis. The use of other gold compounds to treat cancer or inflammatory disease may rely on their ability to inhibit TrxR. In the current study, we tested the hypothesis that a variety of gold compounds may inhibit TrxR. METHODS: We exposed rat-TrxR1 to auranofin, gold sodium thiomalate, sodium aurothiosulfate, triphenyl phosphine gold chloride, or gold acetate, and measured TrxR activity ex vivo. We then compared TrxR1 inhibitory levels of gold compounds to those that inhibited mitochondrial activity of THP1 monocytes and OSC2 epithelial cells, estimated by succinate dehydrogenase activity. RESULTS: All gold compounds inhibited TrxR1 at concentrations ranging from 5 to 4000 nM (50% inhibitory concentration). The oxidation state of gold did not correlate with inhibitory potency, but ligand configuration was important. Au(I)-phosphine compounds (triphenyl phosphine gold chloride and auranofin) were the most potent inhibitors of TrxR. All TrxR1 inhibitory concentrations were sublethal to mitochondrial activity in both THP1 and OSC2 cells. CONCLUSIONS: Diverse types of gold compounds may be effective inhibitors of TrxR1 at concentrations that do not suppress cellular mitochondrial function. Inhibition may be optimized to some degree by altering the ligand configuration of the compounds. These results support future study of a variety of Au compounds for therapeutic development as inhibitors of TrxR1.

Animals↗
PubMed2005

Gold-induced reactive oxygen species (ROS) do not mediate suppression of monocytic mitochondrial or secretory function.

UNLABELLED: The toxicity of anti-rheumatic gold compounds has limited their use and development, yet both the toxicological and therapeutic actions of these compounds remain unclear. In the current study, we tested the hypothesis that intracellular reactive oxygen species (ROS) induced by Au(I) or Au(III) compounds mediate their ability to suppress mitochondrial activity. METHODS: Human THP1 monocytes were exposed to HAuCl(4) x 3H(2)O (Au(III)), or the anti-rheumatic compounds auranofin (AF) or gold sodium thiomalate (GSTM) for 6-72 h, after which mitochondrial activity (succinate dehydrogenase) was measured. To assess the role of cellular redox status as a mediator of mitochondrial suppression, monocytes were pre-treated with a pro-oxidant (t-butyl hydroquinone, t-BHQ) or antioxidant (N-acetyl cysteine, NAC ). ROS levels were measured 0-24h post-gold addition to determine their role as mediators of mitochondrial activity suppression. RESULTS: AF was the most potent inhibitor of mitochondrial activity, followed by Au(III) and GSTM. Only Au(III) induced intracellular ROS; no ROS formation was observed in response to AF or GSTM exposure. Although anti- and pro-oxidants had some effects on mitochondrial suppression of Au compounds, collectively the data do not support redox effects or ROS formation as major mediators of Au-compound mitochondrial suppression. CONCLUSIONS: Our results do not indicate that ROS and redox effects play major roles in mediating the cytotoxicity of AF, GSTM or Au(III).

Auranofin↗
PubMed2005

Extracellular environment as one mediator of blue light-induced mitochondrial suppression.

OBJECTIVES: The current study tested the hypothesis that the extracellular environment mediates mitochondrial suppression of oral epithelial cells and fibroblasts by blue light. METHODS: We exposed Balb fibroblasts (Balb), normal human epidermal keratinocytes (NHEK), and oral squamous carcinoma cells (OSC2) to blue light (30-120J/cm2) in different cell-culture media and in phosphate buffered saline (PBS). Mitochondrial activity (MTT method) was used to assess cellular response 72 h post-light exposure. Cell-culture media were replaced or supplemented before or after light exposure to assess the variables of exposure time and medium degradation as mediators of blue light-induced effects. RESULTS: Mitochondrial activity of NHEK was not suppressed by exposure to blue light regardless of extracellular conditions. The mitochondrial activity of OSC2 and Balb cells was suppressed most when cells were exposed to light in cell-culture medium (versus PBS). Blue light suppressed mitochondrial activity more when irradiated medium remained in contact with the cells at least 1h, indicating a time-dependence of the medium effects. Neither a replacement nor a supplementation of medium components reduced blue light-induced mitochondrial suppression. SIGNIFICANCE: Our results suggest that tissue environments influence cellular responses to blue light and that these environments should be considered when assessing any biological effects of blue light during the photopolymerization of restorative resins.

Animals↗
PubMed2005

Blue light differentially alters cellular redox properties.

Blue light (lambda = 380-500 nm) historically has been used to initiate polymerization of biomaterials and recently has been proposed as a therapeutic agent. New evidence suggests that cell-type-specific responses result from redox changes induced by exposure to blue light. Cultured cells were exposed to defined doses of blue light, equivalent to exposure times of 10 s and 2 min, to achieve energies of 5 J/cm2 and 60 J/cm2, respectively, after which (a) viable cell number, (b) cellular protein profiles, (c) mitochondrial succinate dehydrogenase (SDH) activity, (d) total reactive oxygen species (ROS), and (e) induction of apoptosis were compared to that of nonexposed control cultures. Results showed that blue-light exposure arrested monocyte cell growth and increased levels of peroxiredoxins. SDH activity of normal epidermal keratinocytes (NHEK) was slightly enhanced by blue light, whereas identical treatment of OSC2 oral tumor cells resulted in significant suppression of SDH activity. Blue-light exposure generally induced higher levels of total ROS in OSC2 cells than in NHEK. Finally, only OSC2 cells exhibited signs of apoptosis via Annexin V staining following exposure to blue light. These data support the central hypothesis that blue light induces an oxidative stress response in cultured cells resulting in cell-type-specific survival outcomes. The identification of oxidative stress as a mediator of the effects of blue light is a critical first step in defining its biological risks and therapeutic opportunities.

Apoptosis↗
PubMed2005

Thermal risks from LED- and high-intensity QTH-curing units during polymerization of dental resins.

The aim of this study was to test the ability of an infrared (IR) camera to assess temperature changes and distributions in teeth below restorations when quartz-tungsten-halogen (QTH) and light-emitting diode (LED) curing lights were used to photopolymerize the restorative material. Our hypothesis was that the higher power density and broader spectral distribution of the QTH source would cause greater increases in tooth temperature than the LED source, and that these differences would be best demonstrated with the IR camera. Cavities were prepared on human third molars and restored with a resin composite restorative material. The material was light-cured using three light-curing sources using several exposure times. The external (outside the tooth) and internal (inside the pulp chamber) temperature changes during polymerization of the composite material were recorded over 360 s with thermocouples and an IR camera. Using thermocouples the maximum increase in external temperature (+17.7 degrees C) was reported for the Swiss Master light after 20 s of curing time while the minimum temperature rise (+7.8 degrees C) was reported for the Freelight 2. Whereas a 2.6 degrees C increase in internal temperature was observed after curing 20 s with the Freelight 2, 7.1 degrees C was reported after 60 s of light exposure to Astralis 10. Infrared images showed similar trends in external-internal rises in temperature as the thermocouples, although temperatures measured by the IR were generally higher. These results indicate that the higher power density QTH sources caused greater increases in tooth temperatures than the LED source and that thermocouples may underestimate the heat applied to the tooth.

Composite Resins↗
PubMed2005

Mercury (II) alters mitochondrial activity of monocytes at sublethal doses via oxidative stress mechanisms.

The perennial controversy about the safety of mercury in dental amalgams has adversely affected the availability and the quality of dental care. Chronic Hg(II) blood concentrations above 300 nM are known to alter function of the nervous system and the kidney. However, the effects of blood concentrations of 10 to 75 nM, far more common in the general population, are not clear and mechanisms of any effects are not known. The monocyte is an important potential target of Hg(II) because of its critical role in directing inflammatory and immune responses. In the current study we tested the hypothesis that concentrations of Hg(II) of 10 to 300 nM alter monocyte activity via a redox-dependent mechanism. Mitochondrial activity was used to establish inhibitory concentrations of Hg(II) following 6 to 72 h of exposures to THP1 human monocytic cells. Then subinhibitory concentrations were applied, and total glutathione levels and reactive oxygen species (ROS) were measured. Antioxidants [N-acetyl cysteine, (NAC); Na2SeO3, (Se)] and a pro-oxidant (tert-butylhydroquinone, tBHQ) were used to support the hypothesis that Hg(II) effects were redox-mediated. After 72 h of exposure, 20 microM of Hg(II) inhibited monocytic mitochondrial activity by 50%. NAC mitigated Hg(II)-induced mitochondrial suppression only at concentrations of greater than 10 microM, but Se had few effects on Hg-induced mitochondrial responses. tBHQ significantly enhanced mitochondrial suppression at higher Hg(II) concentrations. Hg(II) concentrations of 75 and 300 nM (0.075 and 0.30 microM, respectively) significantly increased total glutathione levels, and NAC mitigated these increases. Se plus Hg(II) significantly elevated Hg-induced total cellular glutathione levels. Increased ROS levels were not detected in monocytes exposed to mercury. Hg(II) acts in monocytic cells, at least in part, through redox-mediated mechanisms at concentrations below those commonly associated with chronic mercury toxicity, but commonly occurring in the blood of some dental patients.

Biocompatible Materials↗
PubMed2005

Blue light generates reactive oxygen species (ROS) differentially in tumor vs. normal epithelial cells.

OBJECTIVES: Blue light of high intensity is commonly used in dentistry to activate polymerization of resin restorative materials. Other than its effects on the retina, the biological effects of blue light (380-500nm wavelengths) are poorly studied. Limited evidence suggests that blue light acts by forming intracellular reactive oxygen species (ROS) that then affect critical cell functions. If the biological effects of blue light are redox-mediated, antioxidants might be used to mitigate unwanted side effects of blue light during clinical use, or blue light might be used therapeutically to modulate redox-sensitive cell signaling responses. METHODS: Intracellular ROS were estimated using HFLUOR-DA (dihydrofluorescein diacetate), a vital fluorescein-based, redox-sensitive dye. ROS were measured in normal (NHEK) and oral squamous carcinoma (OSC2) epithelial cells, shown previously to respond differentially to blue light irradiation. Two-hour cumulative levels of ROS and approximate ROS lifetimes were measured after irradiation doses of 5-30 J/cm(2). The blue light-induced generation of ROS was further tested by the ability of the antioxidants N-acetylcysteine (NAC) and vitamin E to mitigate intracellular ROS levels. RESULTS: Dose-dependent ROS levels were generated in both NHEK and OSC2 cells, but cumulative levels were higher and persisted longer in the OSC2 cells. Both vitamin E and NAC significantly reduced blue-light-induced levels of ROS, but were more effective in the OSC2 cells. SIGNIFICANCE: The induction of intracellular ROS by blue light implies that redox effects may mediate cellular responses to blue light. This result suggests the opportunity to mitigate any effects of direct or coincident exposure during dental treatment via antioxidants, and the opportunity to exploit differences in redox processing among cells for possible treatment of epithelial cancer or wound healing.

Antioxidants↗
PubMed2005

Effects of sub-toxic concentrations of camphorquinone on cell lipid metabolism.

The biological effects of camphorquinone (CQ), an initiator for light-polymerized resins, have been reported to relate to its ability to generate free radicals and cause radical-induced membrane damage via lipid peroxidation. However, the effects of CQ on lipids other than peroxidation may result in unfavorable tissue responses especially at concentrations that are not overtly toxic to cells. The purpose of the current study was to examine the effects of CQ on cell lipid metabolism at subtoxic concentrations, with or without visible light irradiation. HCP and THP-1 cells were exposed to CQ with or without light irradiation under clinically relevant conditions and lipid metabolism was analyzed using 14C-labeling and thin-layer chromatography. We found that CQ increased synthesis of neutral lipids, such as triglycerides, from 7 to nearly 15% of the total and diglycerides from 2% to about 3% of the total in HCP cells, while synthesis of phospholipids, such as sphingomyelin, was decreased by 1-1.5%. In THP-1 cells cholesterol synthesis increased more than 2-fold and cholesterol ester synthesis increased more than 5-fold. Light-activated CQ did not differ significantly in terms of its bioactivity compared to no-light conditions. We conclude that CQ significantly altered the metabolism of several important structural lipids in two cell types at sub-toxic concentrations that are clinically relevant. These changes in lipid metabolism may in turn affect membrane integrity and permeability and possibly lead to significant changes in cell responses.

Animals↗
PubMed2005

Effect of vascular stent alloys on expression of cellular adhesion molecules by endothelial cells.

OBJECTIVE: Nickel and cobalt ions activate ICAM1 expression on endothelial cells and keratinocytes. Furthermore, these ions are released in vitro and in vivo from the types of alloys used for vascular stents, but the full biological consequences of this release is not known. In the current study, we determined if release of elements from vascular stent alloys that contained nickel and cobalt was sufficient to activate expression of key cellular adhesion molecules (CAMs) by endothelial cells. Expression of these CAMs is a critical step in the long-term inflammatory response to stent materials and possibly to in-stent restenonsis. METHODS: Stainless steel, NiTi, CoCrNi, and NiCr alloys were placed in direct contact with primary human microvascular endothelial cells for 72 hours after preparation at three roughnesses (120, 320, and 1200 grit). Expression of three CAMs--ICAM1, VCAM1, and e-selectin--was assessed using a modified ELISA procedure. Cytotoxicity of the alloys was assessed by measuring succinate dehydrogenase (SDH) activity and total protein content of the cells, and nickel release was measured by atomic absorption spectroscopy. RESULTS: None of the alloys suppressed SDH activity or total cellular protein significantly at any surface roughness, indicating little or no cytotoxicity. Ni release was measurable from all alloys, was greatest from the rougher surfaces, and was significantly different for the different alloy types. NiTi alloys exhibited the lowest nickel release. However, none of the alloys activated expression of the CAMs, regardless of surface roughness or nickel release level. Supplemental experiments using nickel ions alone confirmed that ICAM1 was inducible on the endothelial cells by Ni(II) concentrations above 100 microM. CONCLUSIONS: In this in vitro system, nickel or other elemental release from several common types of stent alloys was not sufficient to activate expression of CAMs on endothelial surfaces. Although these results indicate a low risk for direct activation of endothelial cells by ions released from stent alloys, other mechanisms, such as modulation of CAM expression by monocytes or smooth muscle cells, must be considered before ion-mediated influence on CAM expression can be dismissed.

Alloys↗
PubMed2004

Effects of subtoxic concentrations of benzoyl peroxide on cell lipid metabolism.

Benzoyl peroxide (BP), a tumor promoter, has been shown to cause free-radical-induced lipid peroxidation and membrane damage at toxic concentrations. However, its effects on lipid metabolism at concentrations that were not overtly toxic have not been investigated. The purpose of the current study was to examine the effects of BP and its final degradation product, benzoic acid (BA), on lipid metabolism. Two cell lines, hamster cheek pouch (HCP) and human monocytes (THP-1), were used to determine the effects of BP, BA, and BP combined with FeCl2 on cell lipid metabolism. Cells were exposed to BP and 14C acetate for 24 h, or cells with prelabeled lipids were harvested, and the lipids were extracted and separated with the use of thin-layer chromatography. Lipid metabolism of some neutral lipids such as triglycerides was altered for both cell types in response to BP. Also, cholesterol content was reduced in THP-1 cells and a phospholipid, phosphatidylethanolamine (PE), was reduced in HCP cells. The final degradation product of BP, BA, failed to elicit any response in lipid metabolism. Subtoxic concentrations of BP induced changes in neutral lipids such as triglycerides and cholesterol. The metabolism of major phospholipids except PE remained unchanged. The effects were related to BP and its degradation and varied with the cell type.

Animals↗
PubMed2004

Sublethal concentrations of Au (III), Pd (II), and Ni(II) differentially alter inflammatory cytokine secretion from activated monocytes.

Many transition metals have been viewed collectively as nonspecific biological toxins in cells, which has limited investigation into their possible therapeutic effects. In the current study, the effects of Au(III), Ni(II), and Pd(II) on the differential secretion of cytokines from monocytes has been investigated. This is critical to understanding any therapeutic potential of these metals, their allergenicity, or the clinical effects of current metal therapies such as chrysotherapy. Lethal concentrations (defined as > 50% suppression of mitochondrial succinate dehydrogenase (SDH) activity) of metals were determined by dose-response curves with the use of 72 h exposures to human THP-1 monocytes. Then, secretion of TNFalpha, IL1beta, and IL6 were measured after the monocytes were exposed to sublethal concentrations of metals, with or without stimulation by lipopolysaccharide. The concentrations of Au(III), Pd(II), and Ni(II) required to suppress SDH activity by 50% were found to be 255, 270, and 90 microM, respectively. No sublethal concentration of any metal alone caused secretion of the cytokines. However, LPS-induced cytokine secretion was significantly and differentially altered by sublethal concentrations of each metal. Differential responses were highly dependent on metal concentration and involved both suppression and potentiation of the LPS activation. In the case of Ni(II), potentiation of TNFalpha, IL1beta, and IL6 ranged from 200% for TNFalpha to over 1200% for IL6. Metals such as Au(III), Pd(II), and Ni(II) differentially alter cytokine expression from monocytes. These results imply that metals have more specific effects on cell signaling than previously assumed. These results also are important in explaining multiple clinical effects often seen with chrysotherapy, identifying potential new avenues for metal therapy, and understanding the inflammatory effects of metals such as nickel.

Cell Line↗
PubMed2004

Casting alloys.

Although the role of dental casting alloys has changed in recent years with the development of improved all-ceramic materials and resin-based composites, alloys will likely continue to be critical assets in the treatment of missing and severely damaged teeth. Alloy shave physical, chemical, and biologic properties that exceed other classes of materials. The selection of the appropriate dental casting alloy is paramount to the long-term success of dental prostheses,and the selection process has become complex with the development of many new alloys. However, this selection process is manageable if the practitioner focuses on the appropriate physical and biologic properties, such as tensile strength, modulus of elasticity,corrosion, and biocompatibility, and avoids dwelling on the less important properties of alloy color and short-term cost. The appropriate selection of an alloy helps to ensure a longer-lasting restoration and better oral health for the patient.

Biocompatible Materials↗
PubMed2004

Biological effects of blue light from dental curing units.

OBJECTIVES: This study assessed the effects of three common dental photo-curing light sources (quartz-tungsten-halogen (QTH), plasma-arc (PAC), and laser) on the cellular function of fibroblasts in vitro. METHODS: Mouse fibroblasts were exposed to light from dental photo-curing units for clinically relevant durations, with total energy exposures ranging from 1.3 to 60 J/cm(2). The temperature rise of the cell-culture medium was measured to assess any possible effect from temperature increases, and cellular function was assessed by succinic dehydrogenase (SDH) activity of mitochondria. To directly compare the three light sources, additional experiments were done using equivalent total energy exposures from each source by adjusting the exposure durations for each unit. RESULTS: In experiments that used clinically relevant exposure durations for each light, exposures ranging from 5 J/cm(2) (laser) to 15 J/cm(2) (PAC, QTH) irreversibly suppressed SDH activity nearly 100% when compared to no-light controls up to 72 h post-exposure. For the PAC and QTH sources, exposures as low as 3.5 J/cm(2) also irreversibly suppressed SDH activity. When equivalent energies were used from each light source, exposures of 1 J/cm(2) did not suppress SDH activity for the QTH and laser sources, but significantly (50%) suppressed SDH for the PAC source, indicating a difference in the biological effects of the outputs of the different curing units. Equivalent energy exposure experiments also indicated a definite dependence of SDH activity on the total light energy of exposure. Temperature rises ranged from 2 to 9 degrees C, and elevated temperatures lasted for 60-300 s above the base temperature of 37 degrees C, but peak temperature and the duration of temperature elevation were not always related and depended on the light source used. SIGNIFICANCE: Results from the current study indicate that these photo-curing sources pose some risk of disrupting cellular function in vivo. Further study is necessary in other cell types and under more clinically relevant conditions to estimate the in vivo risk of photo-curing to oral tissues.

3T3 Cells↗
PubMed2004

Cytotoxicity and sealing properties of four classes of endodontic sealers evaluated by succinic dehydrogenase activity and confocal laser scanning microscopy.

The objectives of this study were to evaluate the cytotoxicity and sealing properties of four classes of endodontic sealers (PCS/Kerr, RoekoSeal/Roeko, TopSeal/Dentsply, and EndoREZ/Ultradent). For cytotoxicity testing (MTT method), the materials were either placed immediately in contact with cultured cells or 24 h after setting, then evaluated at three subsequent time points (24 h, 48 h, or 1 wk). For the leakage study, extracted human roots were obturated with acrylic cones and sealers and immersed for 48 h into rhodamine-labeled lipopolysaccharide. The roots were then observed under a confocal laser scanning microscope to estimate (semiquantitatively) the presence of the rhodamine-lipopolysaccharide (LPS) inside the canal. The results showed that cytotoxicity generally increased with time, and that most materials pose significant cytotoxic risks, particularly in the freshly mixed condition. Further, all materials showed significant leakage although there was large variation among teeth. Overall, the silicon-based material (Roeko Seal) was less cytotoxic and more effective in sealing root canals against LPS leakage than other materials.

Analysis of Variance↗
PubMed2003

Toothbrushing causes elemental release from dental casting alloys over extended intervals.

The release of elements from dental alloys has been linked to alloy biocompatibility. Much of the research measuring elemental release has been done in vitro under passive conditions. The current study supplements a previous report that measured elemental release from dental alloys during and after the equivalent of 1 week of toothbrushing. In the current study, toothbrushing times were extended to the equivalent of 2 years, and elemental release was measured during and after brushing, with and without toothpaste. The results showed that for the major classes of dental alloys, brushing alone caused no significant elemental release during the brushing, and only minor increases after brushing. Brushing with toothpaste caused significant increases in elemental release for all elements of all alloys, but the largest increases were for the two nickel-based alloys. Nickel released during brushing with toothpaste reached 600-800 microg/cm(2) of alloy surface. Both beryllium-containing and non-beryllium-containing nickel-based alloys behaved similarly, refuting claims that non-beryllium alloys are superior in this regard. Thus, brushing with toothpaste under these extended in vitro conditions appears to increase the biological liabilities from elemental release for all alloys, but primarily for nickel-based alloys.

Alloys↗
PubMed2003

Effect of subtoxic concentrations of metal ions on NFkappaB activation in THP-1 human monocytes.

THP-1 human monocytes and human peripheral blood monocytes have altered inflammatory cytokine secretion profiles after exposure to a variety of metal ions known to be released from biomaterials. Transcriptional regulation of these cytokines often involves activation of the transcription factor NFkappaB. The present study was designed to determine whether metal ion treatment of monocytes results in changes in levels of activated NFkappaB. THP-1 cells were grown in suspension in the presence of sublethal concentrations of ions of Ag(+), Co(2+), Cu(2+), Hg(2+), Ni(2+), and Pd(2+). After 24 h of exposure to metal ions, the cells were harvested, counted, and the nuclear proteins extracted. Electrophoretic mobility shift assays were performed using a (32)P-ATP end-labeled oligonucleotide consensus sequence for the NFkappaB transcription factor. DNA/protein complexes were quantified by phosphorimage analysis and compared by ANOVA (Tukey, alpha = 0.05). Exposure of THP-1 cells to 100 microM of Pd(2+) caused a significant increase in activated NFkappaB (p < 0.05) whereas treatment with 5 microM of Ag(+) resulted in significantly decreased levels of nuclear NFkappaB (p < 0.05). No other metal ions tested caused a significant change in basal levels of nuclear NFkappaB (Co(2+), Hg(2+), Ni(2+), and Cu(2+)). However, exposure to 50 microM of Cu(2+) resulted in a reproducible, though not significant, increase in nuclear NFkappaB levels. These results indicate that inflammatory responses to some metal ions may be influenced by NFkappaB-mediated transcriptional regulation.

Autoradiography↗
PubMed2003

In vitro cytotoxicity of traditional versus contemporary dental ceramics.

STATEMENT OF PROBLEM: The biocompatibility of new dental ceramics has not been assessed with the same scrutiny as has been applied to alloys and composites. Yet, the biocompatibility of ceramics is critical to the long-term success of dental prostheses because ceramics are in close contact with oral tissues for extended periods. MATERIAL AND METHODS: Five dental ceramics (2 traditional feldspathic veneer porcelains [Vita Omega and Duceragold], 2 lithium disilicate pressable materials [Stylepress and Empress-2], and a pressable leucite-based material [Empress-1]) were tested for their ability to alter cellular mitochondrial dehydrogenase activity after fabrication using a tetrazolium assay, after aging for 2 weeks in a biologic solution and after post-aging polishing with either a fine diamond or diamond polishing paste. Cellular responses were compared with polytetrafluoroethylene controls (analysis of variance, Tukey pairwise post-hoc comparison, alpha=.05). RESULTS: The feldspathic porcelains caused only mild (<25% of controls) mitochondrial suppression regardless of aging or polishing. The pressable leucite-based material initially caused a 5% stimulation (not significant) of mitochondrial activity, which decreased significantly (P<.05) by 30% with aging to levels comparable to the feldspathic porcelains, and did not change with polishing. Both lithium disilicate materials caused an initial suppression of mitochondrial activity that decreased significantly with aging, but Empress-2 was severely cytotoxic initially (<20% of controls, P<.01), and became more cytotoxic again after polishing. Stylepress was less cytotoxic initially (85% of controls, not significant) and did not become cytotoxic again after polishing. CONCLUSIONS: Dental ceramics are not equivalent in their in vitro biologic effects, even within the same class of material, and biologic safety should not be assumed. Most ceramics caused only mild in vitro suppression of cell function to levels that would be acceptable on the basis of standards used to evaluate alloys and composites. However, 1 Li-disilicate material (Empress-2) exhibited cytotoxicity that would not be deemed biologically acceptable on the basis of prevailing empirical standards for dental alloys and composites.

Aluminum Silicates↗
PubMed2003

In vitro biological response to core and flowable dental restorative materials.

OBJECTIVES: In vitro cytotoxicities of commercially available core and flowable dental restorative materials were assessed and compared to traditional resin composites. Our hypothesis was that the increased resin diluents added to achieve higher flow in flowables would increase cytotoxicities, whereas the higher filler content of core materials would decrease cytotoxicities relative to traditional resin composites. METHODS: Specimens were made under aseptic conditions, then extracted into an artificial saliva solution for 0-4 weeks, to assess the effect of aging on cytotoxicity. After extraction, specimens were tested for cytotoxicity in vitro using Balb/c fibroblasts in direct contact format. Cells were exposed to the materials for 48h, after which the mitochondrial activity of the cells was measured (MTT method). Cellular activity was normalized to Teflon negative controls. RESULTS: Core materials were uniformly and severely (<50% of Teflon cellular activity) cytotoxic initially, but several materials (Corepaste, Definite core) improved somewhat with aging in artificial saliva. Flowable materials were uniformly and severely cytotoxic with no trend toward improvement with aging. The Definite-flow was the least cytotoxic of the flowable materials, but it too was severely cytotoxic. SIGNIFICANCE: Commercially available core and flowable restorative materials showed severe in vitro cytotoxicities that are worse than some traditional composites and most dental casting alloys and amalgams used today. Of particular note was the persistent cytotoxicity of these materials after 4 weeks of extraction with artificial saliva. These cytotoxicities indicate a continuing release of mass from these materials at levels that have biological relevance in vitro. In vivo relevance of these cytotoxicities is less clear, but these results indicate a higher biological risk for these materials compared to traditional materials that exhibit less initial toxicity and improve with aging time.

3T3 Cells↗