Biomedical subjects

J C Wataha

Publications and source records attributed to J C Wataha.

At least 37 records · Page 2Linked to original sources

PubMed2001

Relating nickel-induced tissue inflammation to nickel release in vivo.

Nickel has a number of adverse biological effects that have made the use of nickel in biomedical implants controversial. Yet information about the distribution of nickel in tissues around nickel-containing implants is scarce. The purpose of the current study was to use a laser ablation technique, combined with inductively coupled mass spectroscopy, to assess the spatial distribution of nickel around nickel-containing implants in vivo. Polyethylene, pure nickel wire, or a nickel-containing alloy (Ni-Cr) were implanted subcutaneously into rats for 7 days. The tissues were analyzed for Ni content and inflammation at 1-mm intervals up to 5 mm away from the implants. The sham surgery sites and the polyethylene caused mild to moderate inflammation 1-2 mm from the implant site with no detectable nickel in the tissue. The nickel wire caused severe inflammation up to 5 mm away from the implant site with necrosis for 1 mm around the implant. Nickel concentrations reached 48 microg/g near the implants, falling exponentially to undetectable levels at 3-4 mm from the implants. The Ni-Cr wire caused inflammation equivalent to polyethylene, with less than 4 microg/g of nickel present in the tissue for 1-2 mm around the implants. The current study showed that the laser-ablation technique was well suited for the analysis of soft tissues for metal-ion content, and that the nickel distribution in tissues correlated well with overt tissue inflammation.

Alloys↗

PubMed2001

Bonding characteristics to dentin walls of class II cavities, in vitro.

OBJECTIVES: The objective of this study was to test the hypothesis that bond strengths to intact class II cavity wall surfaces are lower than those measured on corresponding flat surfaces isolated by cutting away the rest of the cavity walls. METHODS: Class II (MOD) cavities were prepared in extracted human third molars and then divided into two groups: Intact cavity bonding group or flat surface group. All prepared surfaces were acid-etched and bonded with Scotchbond Multi-Purpose Plus adhesive system and restored with Z100 resin composite. After storage in water for 2 days, the teeth were divided mesio-distally into two equal halves. One half was vertically serially sectioned, while the other half was horizontally serially sectioned to yield a series of 0.5mm thick slabs. Each slab was trimmed into an hour-glass outline with the narrowest cross-sectional area at the region of interest (i.e., axial resin-dentin interface). RESULTS: The mean bond strengths obtained in the cavity bonding group were significantly lower (p<0.05) than those of the flat bonding group. However, within either group, there were no significant consistent differences among the various regions. SIGNIFICANCE: The large flat surfaces used in most laboratory bonding studies may overestimate the bond strengths that can be achieved in complex cavities prepared and restored under clinically relevant conditions.

Acid Etching, Dental↗

PubMed2001

Elemental release from dental casting alloys into biological media with and without protein.

OBJECTIVE: The objective of this study was to determine the role of proteins in affecting elemental release from a variety of clinically available dental casting alloys. An important role for proteins was suspected based on previous reports about the corrosion of stainless steel and the cytotoxicity of alloys after exposure to a saline-protein solution. METHODS: Clinically available alloys with compositions ranging from 0 to 94at.% noble elements were exposed for 1 week to either saline, saline with 3% bovine serum albumin (BSA), or complete cell-culture medium with 3% serum. Atomic absorption spectrophotometry was used to measure the release of elements from the alloys. Elemental release was normalized for the exposed surface area of the alloys. RESULTS: In general, more elemental release occurred into the saline-BSA solution compared to saline alone for all released elements (Ag, Cu, Pd, and Zn) except for Ni. Ni release from the NiCr alloy was lower in the presence of BSA. Each element responded somewhat differently with Pd being the least predictable in its behavior. Elemental release was less in the cell-culture medium than in the saline-BSA solution for most elements. For alloys which released multiple elements, all elements responded similarly but not identically to the presence of protein. A high elemental release during exposure to the saline-BSA solution correlated with a low alloy cytotoxicity post-exposure to the saline-BSA. SIGNIFICANCE: This study demonstrates the importance of defining exactly the composition of biological solutions used to assess in vitro corrosion and biocompatibility of dental casting alloys. Other molecules in addition to proteins appeared to be critical to the corrosion of these alloys in vitro.

Analysis of Variance↗

PubMed2001

Bond strength of composite to dentin using conventional, one-step, and self-etching adhesive systems.

OBJECTIVES: This in vitro study compared the dentin bonding performance of eight adhesive systems using a microtensile bond strength test. METHODS: Thirty bovine teeth were ground to 600-grit to obtain flat root-dentin surfaces. Two conventional adhesive systems (Scotchbond Multipurpose Plus, OptiBond FL), four one-step adhesive systems (Scotchbond 1, Asba S.A.C., Prime and Bond NT, Excite) and two self-etching adhesive materials (Clearfil Liner Bond 2 V and Prompt L-Pop) were evaluated. Each bonding system was applied according to manufacturer's instructions and followed by composite (Z100) application. Immediately after bonding, the teeth were prepared for microtensile testing. Bond strength to dentin was measured using a Vitrodyne V-1000 universal tester. There were 14 replicates for each material. Fractured specimens were further observed by SEM. RESULTS: Scotchbond Multipurpose Plus exhibited significantly (p<0.05) higher bond strength values (30.3+/-9.4 MPa) than all other materials. The bond strengths of the other materials were (from highest to lowest): Opitbond FL (22.4+/-4.3 MPa); Scotchbond 1(18.9+/-3.2); Clearfil Liner Bond 2 V (18.9+/-3.0); Prime and Bond NT (18.3+/-6.9); Asba S.A.C. (14.4+/-2.9); Excite (13.8+/-3.7); and Prompt L-Pop (9.1+/-3.3). Statistical comparisons frequently overlapped, but Optibond was significantly (p<0.05) greater than Asba, Excite, and Prompt L-Pop; whereas, Scotchbond 1 was only significantly (p<0.05) greater than Prompt L-Pop. Asba, Excite and Prompt L-Pop were not significantly different. The fracture modes were mostly adhesive. CONCLUSIONS: The conventional adhesive systems produced higher bond strengths to root dentin than most one-step adhesives and one self-etching adhesive; with the exception of one material in each respective system.

Adhesiveness↗

PubMed2001

Effects of triclosan on the cytotoxicity and fungal growth on a soft denture liner.

STATEMENT OF PROBLEM: Contamination of removable prostheses with microorganisms, particularly Candida albicans, is a common clinical problem. Microban, a broad-spectrum antimicrobial containing triclosan, recently has been proposed to inhibit microbial growth. PURPOSE: This study aimed to determine whether the addition of Microban to PermaSoft denture liner prevents the growth of C albicans and affects the cytotoxicity of the PermaSoft material. MATERIAL AND METHODS: Experimental specimen disks (5 x 1 mm each) with and without incorporated Microban were fabricated aseptically (n = 6) against polyester film to produce a smooth surface. To assess the cytotoxic effect of Microban, the MTT assay was used. To determine the effect of Microban on the growth of C albicans, disks were placed in Transwell dishes, covered with Sabouraud's broth containing an ATCC strain of C albicans, and incubated at 37 degrees C for 24 hours. Wells containing fluorocarbon resin disks or broth alone served as controls. The disks were rinsed to remove unattached C albicans and then sonicated in sterile water to remove surface organisms. Serial dilutions of the water extracts were plated on Sabouraud's agar and returned to the incubator for 24 hours. Colonies were counted with a Brunswick Colony Counter. Growth of C albicans in the internal aspects of the specimens was determined in a manner as previously described, with the exception that the specimens were sonicated to remove surface organisms, minced, and sonicated once more before making serial dilutions. The results were compared with ANOVA and Tukey intervals (alpha=.05). RESULTS: The number of colonies formed ranged from 17 to 31 x 10(5) (mean = 23 +/- 4 x 10(5)) and 14 to 69 x 10(5) (mean = 32 +/- 20 x 10(5)) for the PermaSoft with and without Microban groups, respectively. There was no statistically significant difference between PermaSoft with and without Microban. CONCLUSION: The addition of Microban did not significantly alter the cytotoxicity of the PermaSoft denture lining material or reduce the adherence of viable C albicans to the surface of PermaSoft material after 24 hours.

Analysis of Variance↗

PubMed2001

In vitro TNF-alpha release from THP-1 monocytes in response to dental casting alloys exposed to lipopolysaccharide.

STATEMENT OF PROBLEM: Studies have found that lipopolysaccharide (LPS) attaches to and is eluted from dental alloys, but the biologic effects of LPS are not known. PURPOSE: This study evaluated the ability of dental casting alloys pre-exposed to LPS to activate human monocytes with and without subsequent elution of the LPS. MATERIAL AND METHODS: Eight types of casting alloys (n = 6 specimens per type) were exposed to LPS (Escherichia coli @ 100 micrograms/mL) for 24 hours. Controls were not exposed to LPS. Teflon (Tf) (+/- LPS) served as the material control. Treated alloys were transferred to THP-1 human monocytes for 24 hours or placed into phosphate-buffered saline (PBS) solution for 120 hours before monocyte exposure. Monocyte activation was assessed by tumor necrosis factor alpha (TNF-alpha) secretion into the medium. Alloys without LPS, with LPS but without PBS elution, and with LPS and elution were compared with ANOVA and Turkey intervals (alpha=.05). RESULTS: Specimens without LPS exposure but with elution caused no detectable TNF-alpha secretion from monocytes. Specimens without elution into PBS caused low-to-moderate TNF-alpha secretion, indicating a possible false-positive result from the alloy conditioning solution used. After LPS exposure but no elution, high levels of TNF-alpha were found. When alloys were eluted for 120 hours after LPS exposure, there was no detectable TNF-alpha released. CONCLUSION: In this in vitro system as in past studies, LPS appeared to adhere to and elute from the alloys. Monocytes were activated initially but not after elution into PBS for 120 hours. Alloy conditioning solutions may also have an artifactual effect on cytokine release.

Analysis of Variance↗

PubMed2001

Principles of biocompatibility for dental practitioners.

This article is an evidence-based tutorial on the principles of biocompatibility. Although the technical issues of biocompatibility may seem beyond the scope of most practicing dentists, knowledge of these issues is fundamentally important to ensure the health of patients, dental staff members (including laboratory personnel), and practitioners themselves. Furthermore, the legal liability of dentists is often linked to biocompatibility issues. The biocompatibility of a material is not absolute; it must be measured with regard to the way the material is used. Measuring biocompatibility is a complex process that involves in vitro and in vivo tests. These tests contribute to understanding biologic responses to a material but cannot define the material's biocompatibility with 100% certainty. Practitioners should understand enough about biocompatibility testing methods to critically judge advertising claims and ask relevant questions of manufacturers. Because there is no infallible way to assess biologic response to a material, decisions about the clinical use of a material ultimately must weigh the biologic risks of a material against its potential benefits.

Biocompatible Materials↗

PubMed2001

Effect of lipopolysaccharide contamination on the attachment of osteoblast-like cells to titanium and titanium alloy in vitro.

Failing implants with loss of alveolar bone are associated with gram-negative bacteria that carry lipopolysaccharide (LPS) in the bacterial cell wall. Bony regeneration around these implants is still an unpredictable procedure due to the many clinical factors involved. One important factor is the presence of contaminants such as LPS on the implant surface. The effect of implant-associated LPS on the attachment of bone cells to the implant surface is unknown. This project investigated the effect of LPS on the attachment of osteoblast-like cells (MC3T3-E1) to titanium and titanium alloy surfaces in vitro. We hypothesized that LPS would inhibit bone cell attachment either through loss of cellular attachment sites or alteration of cellular function. Three experimental approaches were used. First, alloy surfaces were exposed to LPS (100 microgram/mL) before the cells were allowed to attach. In the second approach, the cells were exposed to the LPS before they were allowed to attach. Last, the cells were allowed to attach before exposure to LPS. Cellular attachment to implant materials was measured by using a histochemical stain (MTT). The results indicated that LPS presence did not significantly (P > .05) alter osteoblast attachment to titanium or titanium alloy surfaces whether the exposure occurred before or after cellular adherence. It was concluded that LPS did not directly effect the attachment of the MC3T3-E1 osteoblasts to these implant surfaces in vitro. Further research is needed to define the clinical liabilities of LPS during implant placement and maintenance.

3T3 Cells↗

PubMed2000

Effect of silver, copper, mercury, and nickel ions on cellular proliferation during extended, low-dose exposures.

Previous studies have demonstrated and quantified the cytotoxicity of metal ions in vitro, but the data from these reports have been limited to short-term exposures of metal ions to cells (24-72 h). Yet, the longer-term, low-dose effects of metal ions are most relevant to the clinical use of dental and other biomedical alloys. Thus, the purpose of the current study was to assess longer-term effects of ions of silver, copper, mercury, and nickel - four metal ions known to be released from dental alloys - on monocytes. THP-1 human monocytes were exposed to the metal ions for up to 4 weeks. Concentrations of the metal ions were 1-10% of those known to cause cytotoxicity with 24-h exposures. Cellular proliferation and cellular viability were measured weekly. Ag(1+) and Hg(2+) did not alter the percentage of nonviable cells, but Cu(2+) and Ni(2+) increased the nonviable component as a function of metal concentration. These effects were cumulative over the 4 weeks only for Ni(2+). All metal ions caused a significant reduction in cellular proliferation, but the pattern of the effect was unique to each metal ion, and the effects were often not evident until 3 or 4 weeks of exposure. The results of the current study indicate that metal ions released from metallic biomaterials may have adverse biological effects at concentrations lower than previously reported.

Biocompatible Materials↗

PubMed2000

Biocompatibility of dental casting alloys: a review.

STATEMENT OF PROBLEM: Dental casting alloys are widely used in applications that place them into contact with oral tissues for many years. With the development of new dental alloys over the past 15 years, many questions remain about their biologic safety. Practitioners must choose among hundreds of alloy compositions, often without regard to biologic properties. PURPOSE: This article is an evidence-based tutorial for clinicians. Concepts and current issues relevant to the biologic effects of dental casting alloys are presented. SUMMARY: The single most relevant property of a casting alloy to its biologic safety is its corrosion. Systemic and local toxicity, allergy, and carcinogenicity all result from elements in the alloy being released into the mouth during corrosion. Little evidence supports concerns of casting alloys causing systemic toxicity. The occurrence of local toxic effects (adjacent to the alloy) is not well documented, but is a higher risk, primarily because local tissues are exposed to much higher concentrations of released metal ions. Several elements such as nickel and cobalt have relatively high potential to cause allergy, but the true risk of using alloys containing these elements remains undefined. Prudence dictates that alloys containing these elements be avoided if possible. Several elements in casting alloys are known mutagens, and a few such as beryllium and cadmium are known carcinogens in different chemical forms. Despite these facts, carcinogenic effects from dental casting alloys have not been demonstrated. Prudent practitioners should avoid alloys containing these known carcinogens. CONCLUSION: To minimize biologic risks, dentists should select alloys that have the lowest release of elements (lowest corrosion). This goal can be achieved by using high-noble or noble alloys with single-phase microstructures. However, there are exceptions to this generality, and selection of an alloy should be made on a case-by-case basis using corrosion and biologic data from dental manufacturers.

Biocompatible Materials↗

PubMed2000

Effect of sub-lethal concentrations of HEMA (2-hydroxyethyl methacrylate) on THP-1 human monocyte-macrophages, in vitro.

OBJECTIVE: Resin monomers such as HEMA (2-hydroxyethyl methacrylate) can be released from restorative materials and diffuse into the tooth pulp over long periods of time. Although the short-term toxicity of resin monomers has been well documented, little is known about the risk for chronic toxicity resulting from low concentrations of resins. Thus, the hypothesis tested in this study was that sub-lethal concentrations of HEMA alter the functions of macrophages after long-term exposure. METHODS: Human THP-1 monocyte-macrophages were exposed to concentrations of HEMA between 0 and 1.5 mmol/l for up to 6 weeks. Cellular proliferation was measured by a hemocytometer with trypan-blue dye exclusion. Mitochondrial activity was measured by the MTT assay, and total cellular protein was measured using the bicinchoninic acid assay. RESULTS: Macrophage proliferation was inhibited 40-50% (significant, p < 0.05) by as little as 0.75 mmol/l after 1 week of exposure. Inhibition of proliferation remained constant after 1 week. The total protein per cell increased by as much as 80% (significant, p < 0.05) after 2 weeks and remained elevated through 6 weeks. Mitochondrial activity per cell increased 60-80% (significant, p < 0.05) after 2 weeks, then decreased. However, mitochondrial activity remained significantly elevated above controls through 6 weeks. SIGNIFICANCE: Findings from the current study indicate that 6-week exposures of monocytes to HEMA alter their proliferation and other activities at concentrations substantially lower than previously reported. This is particularly relevant in light of evidence that such concentrations have been previously shown to come through dentin by diffusion.

Analysis of Variance↗

PubMed2000

Effect of dental metal ions on glutathione levels in THP-1 human monocytes.

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.

Analysis of Variance↗

PubMed2000

4-Hydroxytamoxifen-induced cytotoxicity and bisphenol A: competition for estrogen receptors in human breast cancer cell lines.

Increasing concerns over the effects of environmental estrogens on wildlife and humans have highlighted the need for screening systems to assess potentially estrogenic effects of test compounds. As a result, in vitro screening methods such as cell proliferation assays using the estrogen-responsive human breast cancer cell line, MCF-7, have been developed. The present study describes an alternative in vitro approach for the assessment of such xenoestrogens, based on estrogenic rescue of MCF-7 cells from antiestrogen-induced cytotoxicity. This method measures the ability of various estrogenic compounds to compete with a known estrogen-receptor-mediated antihormonal drug, 4-hydroxytamoxifen, using the 1-[4,5-dimethylthiazol-2-yl]-3,5-diphenylformazan (MTT) assay to assess mitochondrial activity. Because 4-hydroxytamoxifen treatment of cells results in a dramatic decrease in mitochondrial dehydrogenase activity which is directly related to their estrogen-receptor content, inhibition of this effect with estrogenic compounds represents an estrogen-receptor interaction, or estrogenic rescue. The estrogenic compounds tested include a weak xenoestrogen, bisphenol A (BPA), and two biological estrogens, 17alpha- and 17beta-estradiol. Competitive inhibition of 4-hydroxytamoxifen-induced cytotoxicity by BPA was compared to that of the biological estrogens. The results indicate that the biological estrogens can successfully compete with the antiestrogen in a dose-dependent manner. In addition, the assay is sensitive enough to detect estrogenic rescue by even the very weak xenoestrogen, BPA, albeit at high BPA concentrations. This simple in vitro method could be used as an alternative or second-line screen for potential xenoestrogens.

Benzhydryl Compounds↗

PubMed1999

Estrogenicity of bisphenol A and bisphenol A dimethacrylate in vitro.

Although pit and fissure sealants have been utilized extensively in dentistry as a way of preventing occlusal caries, results described by Olea et al. (1996) raised concerns about the safety of sealants and other resin-based dental materials due to the reported presence of bisphenol A (BPA) and its dimethacrylate ester (BPA-DM). Although the release of these compounds from dental materials has not been substantiated by two subsequent studies, we believed it was important to confirm or refute the report that BPA and BPA-DM have estrogenic activity in vitro. We grew breast cancer cells (MCF-7, T-47D, ZR-75-1) known to proliferate under estrogenic stimulation in phenol red-free DMEM containing human serum and concentrations of BPA or BPA-DM ranging from 10(-8)M to 5 x 10(-6)M. After 1 week, plates were harvested for crystal violet or sulforhodamine-B assays, and the optical densities of groups of treated cells were compared with values from control cells. At concentrations at or above 10(-6)M, both BPA and BPA-DM significantly increased cell proliferation (p < 0.05), comparable to the increase seen with 10(-9)M of estrogen. Flow cytometric methods demonstrated that these mitogenic effects occurred within 24 h of exposure to estrogen, BPA, or BPA-DM. The increase in DNA synthesis was analogous to that seen with estrogen stimulation. Thus, we confirmed that BPA and BPA-DM cause cell proliferation at micromolar concentrations that exceed the effective concentrations of estrogen by 1 to 10,000-fold.

Benzhydryl Compounds↗

PubMed1999

Ability of Ni-containing biomedical alloys to activate monocytes and endothelial cells in vitro.

Nickel-containing alloys commonly are used in medical and dental applications that place them into long-term contact with soft tissues. The release of Ni ions from these alloys is disturbing because of the toxic, immunologic, and carcinogenic effects that have been documented for some Ni compounds. In particular, Ni ions in solution recently have been shown to cause expression of inflammatory mediators, such as interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and intercellular adhesion molecules (ICAMs) from keratinocytes, monocytes, and endothelial cells. However, the ability of the solid alloys themselves to induce these inflammatory effects has not been demonstrated. An in vitro system was used to determine if Ni-containing biomedical alloys could cause secretion of either IL-1beta or TNF-alpha from monocytes or expression of ICAMs on endothelial cells. Pure nickel, titanium, and three biomedical alloys-18-8 stainless steel, NiTi, and Rexillium III-were evaluated. First, it was determined whether or not the alloys or pure metals could cause cytotoxicity to THP-1 human monocytes or human microvascular endothelial cells (HMVECs) by measuring the succinic dehydrogenase (SDH) activity of the cells. Then, using identical conditions of exposure, the secretion of IL-1beta or TNF-alpha from monocytes or ICAM-1 expression on the HMVECs was determined. Only pure nickel suppressed (by 48% compared to Teflon controls) the SDH activity of the HMVECs or THP-1 monocytes. No alloy or metal caused the HMVECs to express ICAM-1, but the NiTi alloy caused a significant (ANOVA/Tukey) secretion of IL-1beta from the THP-1 monocytes. Secretion of TNF-alpha induced by NiTi was detectable but not statistically significant. The levels of IL-1beta secretion from monocytes were sufficient to induce ICAM-1 expression on HMVECs. The release of Ni from the NiTi was a logical suspect in causing the IL-1beta secretion by monocytes, but its role was not confirmed since other alloys, such as Rexillium III, released the same quantities of Ni yet did not activate the THP-1 monocytes. Within the limitations of in vitro conditions, our results indicate that NiTi alloys pose a risk of promoting an inflammatory response in soft tissues by activating monocytes. Further study is needed to substantiate this finding in vivo.

Alloys↗

PubMed1999

Cytotoxicity of Au-based dental solders alone and on a substrate alloy.

Gold-based dental solders are commonly combined with a substrate alloy in dental prostheses and are in long-term intimate contact with oral tissues, yet the biological properties of dental solders are almost unknown. Previous studies have shown that combinations of dissimilar alloys may increase the risk of elemental release and adverse biological effects. The purpose of the current study was to measure the cytotoxicity of dental solders alone and in combination with a substrate metal. Based on previous reports, which measured the cytotoxicity of combinations of dissimilar alloys, we hypothesized that the cytotoxicity of solder-substrate combinations cannot be predicted based on the cytotoxicity of the solders alone. Specimens of 13 high-noble (Au >/= 40 wt%; Au+Pt+Pd >/= 60%) and 6 noble (Au+Pt+Pd >/= 25 wt%) solders were made either in bulk or in combination with a compatible Au-Pd substrate alloy. The results showed that, most often, solder-substrate combinations were less toxic than the solders alone, but three high-noble solders were more cytotoxic in combination. We concluded that, when screening new Au-based dental solders for cytotoxicity, the solder should be assessed in combination with a clinically relevant substrate alloy.

Alloys↗

PubMed1999

In vitro cytotoxicity of resin-containing restorative materials after aging in artificial saliva.

Studies have reported that dental resin-based materials release substances which have biological liabilities. However, some current methods for detecting these substances may not be adequate to detect biologically relevant concentrations. In the current study, we hypothesized that resin-based materials exhibit cytotoxic effects and alter cellular function in vitro when high-pressure liquid chromatography (HPLC-UV detection) cannot detect any release of substances. We further hypothesized that this release continues even after aging the samples in artificial saliva. Five types of composite or compomer materials (Z-100, Tetric Ceram, Dyract AP, Solitaire, and Clearfil AP-X) and one organically modified ceramic material (Definite) were tested after aging in artificial saliva for 0, 7, or 14 days. Cytotoxicity was assessed using direct contact with fibroblasts and measurement of succinic dehydrogenase activity after 48 h of exposure post aging. Release of substances from the materials was assessed using HPLC with UV detection. Altered cellular function was estimated by measuring proliferation of MCF-7 cells with sulforhodamine staining. HPLC showed that whereas initial release of substances was higher without aging, this release dropped significantly after 7 or 14 days of aging, and was equivalent to the Teflon controls after 14 days for four of the materials (Tetric Ceram, Definite, Solitaire, and Clearfil AP-X). Without aging in saliva, all materials had cytotoxicities > 50% of the Teflon negative controls. After 14 days of aging, all materials except the Definite continued to show severe cytotoxicity. Only the Definite could be tested for its ability to alter cellular function because of the continuing toxicity of the other materials. This modified ceramic material caused a significant proliferative effect on the MCF-7 cells indicating that sufficient substances were released to alter cellular function. We concluded that all of these commercially available resin-based dental materials continue to release sufficient components to cause lethal effects or alter cellular function in vitro even after 2 weeks of aging in artificial saliva.

Analysis of Variance↗

PubMed1999

Accelerated toxicity testing of casting alloys and reduction of intraoral release of elements.

STATEMENT OF PROBLEM: Short-term (72-168 hours) in vitro testing of dental casting alloys for cytotoxicity may not reflect in vivo biocompatibility. An accelerated test for evaluation of dental casting alloy cytotoxicity could help screen newly developed alloys more rapidly and accurately. PURPOSE: This study evaluated a method of accelerating alloy cytotoxicity by short-term conditioning of alloys. Cytotoxicity and mass release of these conditioned alloys were compared with alloys conditioned for 10 months or unconditioned alloys. The hypothesis was that a short-term conditioning procedure could be developed that would give cytotoxicity and mass release values similar to alloys exposed to a biologic solution for 10 months. MATERIAL AND METHODS: Dental casting alloys were conditioned in either saline, cell-culture medium, or a saline/bovine serum albumin (BSA) solution for 168 hours before standard in vitro cytotoxicity testing. Eight types of casting alloys with a range of nobilities (98% to 0%) were tested (n = 6). Controls were Teflon (Tf). Conditioned alloys were placed in direct contact with Balb/c fibroblasts for 72 hours, and cell viability was measured by succinic dehydrogenase activity (MTT method) relative to Tf controls. Elements released into the conditioning solutions were measured by atomic absorption spectroscopy. The cytotoxicities of conditioned alloys and total mass released were compared with unconditioned alloys (0 month) and alloys that were exposed to cell culture medium for 10 months. ANOVA and Tukey multiple comparison intervals (alpha =. 05) were used to compare mass released and cytotoxicity. RESULTS: Conditioning for 168 hours altered the cytotoxicity of the alloys. The saline/BSA conditioning solution reduced cytotoxicity of the alloys compared with unconditioned alloys, except for the Ni-Cr alloy. Other conditioning solutions were not as uniform in their effects, some increasing toxicity, others decreasing it. Overall, the saline/BSA solution was the most effective at changing alloy cytotoxicity from the unconditioned (0 month) toward the 10-month values. Mass loss during saline/BSA conditioning most closely approximated 10-month loss for most alloys. CONCLUSION: Conditioning of casting alloys appeared to be a useful method for predicting long-term cytotoxicity with a short-term in vitro test, but all conditioning solutions were not equivalent.

Animals↗