Biomedical subjects

C A Lefebvre

Publications and source records attributed to C A Lefebvre.

At least 19 recordsLinked to original sources

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↗

PubMed2000

The hippocampal neurons of neuronal apoptosis inhibitory protein 1 (NAIP1)-deleted mice display increased vulnerability to kainic acid-induced injury.

The neuronal apoptosis inhibitory protein (NAIP) is a member of a novel family of inhibitor of apoptosis (IAP) proteins. The IAP genes are highly conserved from baculovirus to metazoans and suppress apoptosis induced by a variety of triggers both in vitro and in vivo. Here we describe the generation and characterization of mice with the targeted deletion of NAIP1. We demonstrate that the NAIP1-deleted mice develop normally. However, the survival of pyramidal neurons in the hippocampus after kainic acid-induced limbic seizures is greatly reduced in the NAIP1 knock-out animals. Thus, although NAIP1 is not necessary for normal development of murine central nervous system, the endogenous NAIP1 is required for neuronal survival in pathological conditions.

Animals↗

PubMed1999

Genomic organization and physical map of the human inhibitors of apoptosis: HIAP1 and HIAP2.

We report the genomic organization, mapping, and tissue distribution of the human inhibitors of apoptosis, HIAP1 and HIAP2. HIAP1 is 8.7 kb in length and is contained within eight coding and two non-coding (5'UTR) exons. The 4.5-kb HIAP2 message is contained within eight coding region exons and a single 5'UTR exon. The HIAP1 and HIAP2 genes lie in tandem on Chromosome (Chr) 11 (q22-23) with the intergenic distance being approximately 7 kb. The tissue distributions of HIAP1 and HIAP2 appear similar although the relative expression of HIAP1 is generally higher. Expression is highest in the kidney, small intestine, liver, and lung and lowest in tissues of the central nervous system.

5' Untranslated Regions↗

PubMed1999

Dental considerations in upper airway sleep disorders: A review of the literature.

STATEMENT OF PROBLEM: Upper airway sleep disorders are becoming recognized as common medical concerns. Multiple treatment options have been advocated, including the use of dental devices. Dental practitioners are being asked by the medical profession to become a part of the treatment team. This may be a challenging task because of the large number of dental devices available, rapid advancement in the understanding of this disease, and numerous publications. PURPOSE: This article reviews the anatomic features and etiologic factors of upper airway sleep disorders and medical and dental treatment options. METHODS: The literature review was conducted with an accepted literature research tool, PubMed, developed by the National Library of Medicine. Key words searched included "obstructive sleep apnea," "sleep apnea," "sleep disorders," and "snoring". CONCLUSION: Dental devices are indicated in snoring and mild-to-moderate obstructive sleep apnea patients after medical evaluation and referral.

Humans↗

PubMed1999

Effect of dentin bonding agents on the secretion of inflammatory mediators from macrophages.

Dentin bonding agents (DBAs) have been proposed as substitutes for amalgam as root-end filling materials. The current study tested the hypothesis that certain components of DBAs could alter the secretion of cytokines from macrophages. Such alteration would likely be undesirable for healing of the periapical tissues. Human THP-1 macrophages were exposed to 2-hydroxyethyl methacrylate, 4-methacryloxyethyl trimelliate anhydride, bisphenol-gycidylmethacrylate, and urethane dimethacrylate. The secretion of interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) were measured with or without challenge by lipopolysaccharide (LPS). Results showed that all DBA components completely suppressed LPS-induced IL-1 beta and TNF-alpha secretion at concentrations that suppressed mitochondrial activity by 50%. In addition, 4-methacryloxyethyl trimelliate anhydride induced secretion of IL-1 beta, but not TNF-alpha, without the LPS challenge. These results indicate that DBA components may alter normal macrophage-directed inflammatory responses if the macrophages are exposed to sufficiently high concentrations of these components.

Acrylic Resins↗

PubMed1999

Endotoxin affinity for orthodontic brackets.

Endotoxin, cell envelope lipopolysaccharide produced by gram-negative bacteria can activate an immune response through a variety of pathways. In addition, it can stimulate bone resorption and reduce the periodontal tissue's healing capacity. Previous studies have documented the affinity of lipopolysaccharide for restorative materials. This study evaluated the affinity of lipopolysaccharide for commercially available orthodontic brackets. Stainless steel, ceramic, plastic, and "gold" brackets were exposed to 10 EU/mm2radiolabeled Porphyromonas gingivalis or Escherichia coli lipolpoysaccharide in water and incubated for 24 hours at 37 degrees C. Brackets were then transferred to fresh lipopolysaccharide-free water and incubated for 24 hours at 37 degrees C to evaluate elution. This elution transfer was continued up to 96 hours total incubation. Lipopolysaccharide adherence and elution levels were calculated after treatment, and elution solutions were evaluated through liquid scintillation spectrometry. Mean initial lipopolysaccharide adherence ranged from 2.42 +/- 0.26 EU/mm2(E. coli, plastic) to 6.75 +/- 0.34 EU/mm2 (P. gingivalis, stainless steel). P. gingivalis lipopolysaccharide adherence was significantly greater than E. coli lipopolysaccharide adherence for all bracket types. Moreover, for each lipopolysaccharide type, stainless steel brackets exhibited significantly greater lipopolysaccharide adherence. Regarding elution, only the P. gingivalis lipopolysaccharide-exposed ceramic and plastic brackets at 24 hours and the stainless steel and ceramic brackets at 48 hours eluted measurable lipopolysaccharide. Results from this study demonstrate that P. gingivalis and E. coli LPS exhibit a high affinity for orthodontic brackets. In vivo, this affinity could affect the concentration of LPS in the gingival sulcus, thereby contributing to inflammation in tissues adjacent to the brackets.

Analysis of Variance↗

PubMed1999

Effects of long-term sub-lethal concentrations of dental monomers on THP-1 human monocytes.

Studies have shown that monomers from dental resins are acutely cytotoxic, but little is known of their long-term effects at sub-lethal concentrations. The current study determined the long-term effects of sub-lethal concentrations of TEGDMA (triethyleneglycol dimethacrylate) and Bis-GMA (bisphenol-glycidylinethacrylate), two common dental monomers, on the in vitro cellular proliferation, succinic dehydrogenase activity, and total cellular protein production of monocytes. Human THP-1 monocytes were exposed to concentrations of 100, 200, and 400 micromol l(-1) of TEGDMA or 1, 5, and 25 micromol l(-1) Bis-GMA for 5 weeks. Controls received only vehicle solutions of ethanol. Each week cellular proliferation (hemocytometer), succinic dehydrogenase (SDH) activity (MTT) and total cellular protein (bicinchoninic acid) were assessed. The results were compared with ANOVA and Tukey intervals (alpha = 0.05). TEDGMA had no proliferative or cellular protein effects, but increased SDH activity 20-60% in week 1 (p < 0.05). SDH activity then decreased 40% in week 2, followed by a gradual increase of 30-40% over week 3-5 (p < 0.05). Bis-GMA reduced proliferation by 40-60% from 1-5 weeks exposure (p < 0.05). However, SDH activity and total protein per cell were not affected. There was some indication of increased SDH activity after 5 weeks (20-30%, p < 0.05). Sub-lethal concentrations of TEGDMA and Bis-GMA have significant long-term effects on monocytes at low-dose 5-week exposures in vitro. Each monomer acted differently.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1999

Alterations in cell lipid metabolism by glycol methacrylate (HEMA).

Components of dental resins such as dimethylaminoethyl methacrylate (DMAEMA) can alter cell lipid composition, presumably by esterase-mediated hydrolysis. The resulting dimethylethanolamine is incorporated into cell phospholipids, while the methacrylic acid may alter several metabolic pathways. We hypothesize that HEMA is cleaved in a similar manner and the released ethylene glycol is incorporated into cell lipids, yielding phosphatidylethylene glycol (PtEG), and the methacrylic acid alters other lipid pathways in a manner similar to that of methacrylic acid released from hydrolysis of DMAEMA. Cultures of hamster buccal pouch (HCP) and rabbit kidney (RK13) epithelial cells were exposed to subtoxic concentrations of HEMA in the presence of [14C]-acetate or [3H]-oleic acid. Other cultures were prelabeled with [14C]-acetate followed by exposure to various concentrations of HEMA. Cell lipids were extracted by the method of Bligh and Dyer and separated by thin layer chromatography on silica gel K-6 plates or SG-81 silica gel loaded chromatography paper. The fate of the ethylene glycol was traced using [14C]-ethylene glycol. Radioactive lipids were located using autoradiography and known standard lipids and quantitated by liquid scintillation spectrometry. In the presence of HEMA several classes of lipids were altered. Among the neutral lipids, the most notable changes involved sterol precursors, triglycerides, fatty acids, and cholesterol esters, while phosphatidylcholine was affected among the phospholipids. The results differed quantitatively between the two cell types. Results also suggest that EG, including that released by hydrolysis of HEMA, is incorporated into cell phospholipids, producing PtEG. The changes in neutral lipid labeling may occur by alteration of lipid synthetic pathways utilizing acetyl Co-A as well as inhibition of enzymes involved in synthesis of cholesterol from sterol precursors and hydrolysis of cholesterol esters. Synthesis of PtEG may take place via phospholipase D-mediated headgroup exchange. Alterations in the cellular lipids may affect cell membrane properties and associated cell functions.

Animals↗

PubMed1998

Effects of dentin bonding agents on macrophage mitochondrial activity.

Dentin bonding agents (DBA) have been considered for use as root-end fillings. Previous studies have documented the release of DBA components in vivo and in vitro, but the biological implications are not clear. The macrophage is important in wound healing, and likely to be important in any inflammatory response. Therefore, this study determined the concentrations of the components of DBAs that suppress the mitochondrial activity of human macrophages in vitro. THP-1 macrophages were cultured in the presence of four DBA components (2-hydroxyethyl methacrylate (HEMA), 4-methacryloxyethyl trimellitate anhydride (4-META), bisphenol-glycidylmethacrylate (Bis-GMA), and urethane dimethacrylate (UDMA)) at various concentrations and for varying durations. Residual effects were also measured after the resins were removed. Controls received only the vehicle solution, ethanol or water. THP-1 mitochondrial activity was estimated using the MTT assay, and the 50% toxicity concentrations (TC50) were determined graphically. Resin components suppressed the mitochondrial activity of macrophages at different concentrations (TC50 values for HEMA (10,000 mumol/L), 4-META (3,800 mumol/L), Bis-GMA (130 mumol/L), and UDMA (110 mumol/L) at 24 h, and the effect was time-dependent. Residual effects were observed for all resins.

Acrylic Resins↗

PubMed1998

Effect of heating delay on conversion and strength of a post-cured resin composite.

Physical property enhancement in light-cured resin composites from post-cure heating is attributed to free radicals created during initial photocuring, the number of which decreases following initial light-curing. Clinically, it is important to know when the number of remaining free radicals is too low to provide for additional conversion of monomer in post-cure-heated specimens. The hypothesis tested is that the potential for additional conversion in post-cure-heated resin composite restorations is dependent upon the time after initial light-curing at which the specimen is exposed to heat treatment. This research examined the effect of delay in post-cure heating after initial photo-activation on strength and monomer conversion of a commercial resin composite material. Discs (10 x 1 mm) of Herculite XRV (Kerr/Sybron, Orange, CA) were photocured at standardized conditions. One group was left unheated, and another was subjected to post-cure heating (Brilliant DI-500, Coltène AG, Altstätten, Switzerland) at the following times after being light-cured: 5 and 30 min, and 6, 24, 48, 72, 96, and 120 hrs. After the appropriate delay time, unheated and heated specimens (n = 10) were tested for biaxial flexural strength at a constant stressing rate. Recovered, fractured strength specimens (n = 10) were analyzed for cure by means of IR spectroscopy. Post-cure heating increased strength over that of the unheated specimens only for the shortest delay times: 5 or 30 min. Thereafter, strength values were statistically equivalent (p < 0.05). Delay in heating did not significantly enhance strength of post-cure-heated specimens, but delay in time did improve strength of the unheated groups. The greatest monomer conversion was obtained when post-cure heating was applied within 6 hrs following light-curing. The difference in cure between unheated and heated specimens remained significant up to 96 hrs of delay. Flexural strength of post-cure-heated specimens remained unchanged with time delay for heating specimens. Maximal monomer conversion of post-cured specimens is obtained only within 6 hrs of light-curing. The potential for additional conversion arising from post-cure heat treatment is dependent upon the time following initial curing at which heat is applied following initial light-curing. However, delay in heat application has no influence on flexural strength.

Analysis of Variance↗

PubMed1997

Burning mouth syndrome: a review of etiologies.

STATEMENT OF PROBLEM: Dental practitioners occasionally have patients present clinically with a history of chief complaint of burning and painful sensations in the oral cavity. Often the patient demonstrates clinically normal mucosa, which can make formulating a diagnosis challenging. This scenario, has been referred to as burning mouth syndrome, a multifactorial syndrome. PURPOSE: The purpose of this article is to present a review of etiologic factors and clinical implications related to the condition of burning mouth syndrome.

Adult↗

PubMed1997

Effect of treatment concentration on lipopolysaccharide affinity for two alloys.

OBJECTIVE: This study compared gram-negative bacterial lipopolysaccharide (LPS) adherence to and elution from a Type III gold and a Ni-Cr-Be alloy using Escherichia coli LPS. METHOD: One-half of the specimens of each alloy were pre-treated with 500 micrograms non-radiolabeled E. coli LPS for 24 h at 37 degrees C. All disks were then incubated with 0.15, 15 or 150 micrograms radiolabeled E. coli LPS for 24 h at 37 degrees C. To evaluate radiolabeled LPS elution, specimens were transferred to LPS-free water and incubated for 24 h at 37 degrees C. The elution scheme, which consisted of 24 h incubations and subsequent transfer to new LPS-free water, continued for up to 96 h total elution. Radiolabeled LPS adherence and elution was determined through liquid scintillation spectrometry. Control disks not treated with LPS were evaluated throughout the study with an enzymatic assay to ensure that extraneous LPS contamination did not occur. A multifactor ANOVA (p = 0.05) was used to evaluate differences in adherence to alloy specimens based upon alloy type, pretreatment status and [3H]LPS concentration. A repeated measures analysis ANOVA (p = 0.05) was used to evaluate differences in elution patterns among groups over time. Least square means were compared in case of significant effects. RESULTS: Toxin uptake at each treatment concentration was significantly different from the other treatment concentrations. In addition, significantly greater amounts of [3H]LPS eluted from the non-pretreated Ni-Cr-Be alloy following the 0.15 and 15 micrograms radiolabeled [3H]LPS treatment, whereas no difference in elution was found among experimental groups following the 150 micrograms [3H]LPS treatment. SIGNIFICANCE: E. coli LPS, an LPS type representative of enteric bacteria common to the gingival sulcus, has differing affinities for the alloys. This affinity difference could influence periodontal inflammatory processes, thereby resulting in differing tissue responses adjacent to dental restorations fabricated from these materials. The interaction of other LPS types with these alloys could differ.

Adhesiveness↗

PubMed1997

Effects of an aminomethacrylate on epithelial cell lipid metabolism.

Methacrylates can affect cell functions by surfactant-like effects or by altering cell lipid composition. Dimethylaminoethyl methacrylate (DMAEMA), an activator widely used in visible-light polymerized dental resins has been shown to elute readily into aqueous environments. The current study examined the metabolism of this material by oral epithelial cells (HCP) and its subsequent effects on cell lipids. Cells were plated in culture medium, then exposed to DMAEMA in the presence of 14C-acetate, a precursor which labeled the cell lipids. Other cultures were prelabeled with radioisotope, then exposed to DMAEMA. After incubation, the cell lipids were extracted and separated by TLC. Radioactive lipids were located and quantitated. Exposure of the cells to DMAEMA resulted in decreased synthesis of cholesterol with a concomitant increase in sterol precursors. Cholesterol esters and triacylglycerides also increased. Among the polar lipids, phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) decreased in response to DMAEMA. However, dimethylphosphatidyl ethanolamine (DMPE), a precursor of PC not detectable in control cultures, accumulated to a significant extent in cells exposed to DMAEMA. Furthermore, changes in PC and DMPE levels persisted in the cells for at least 48 h after removal of the DMAEMA. The results indicate that DMAEMA produces alterations in the relative amounts of several cellular neutral and polar lipids. Such alterations, especially of the normal phospholipid composition, along with an alteration in cellular cholesterol, could result in altered membrane-associated cell functions.

Acetates↗

PubMed1996

The structure and complete nucleotide sequence of the human cyclophilin 40 (PPID) gene.

Cyclophilin 40 is a recently identified member of the cyclophilin family that is found in an unactivated steroid hormone receptor complex. Cyclophilin 40 possesses a region homologous to FKBP59, a member of the FK506-binding protein family that is also a component of the receptor complex. We report the isolation and sequencing of the entire human cyclophilin 40 (hCyP40) gene (human gene symbol PPID). The gene contains 10 exons (43 to 698 bp) and 9 introns encompassing 14.2 kb. The exon organization of the cyclophilin-like region is not similar to that of the human cyclophilin A gene (PPIA), suggesting their early divergence in evolution. Determination of the sequence of the 5' end of the hCyP40 mRNA by an "anchor-ligation PCR" procedure showed that transcription is initiated from a cluster of sites about 80 bp upstream from the first in-frame ATG. The immediate 5'-flanking region of the gene lacks typical TATA and CAAT boxes, but is GC-rich and contains Sp1 sites, features characteristic of promoters associated with housekeeping genes. The hCyP40 gene was mapped to chromosome 4 by PCR with genomic DNA from somatic cell hybrids. As shown by "Zoo blot" analysis, the cyclophilin 40 gene appears to be highly conserved throughout evolution.

Amino Acid Isomerases↗

PubMed1996

Responses of oral epithelial cells to dental resin components.

The light-polymerized resins used in dentistry and their various constituents have been shown to produce significant levels of cytotoxicity, depending upon the material and the cell type exposed to it. These responses include altered cell growth and macromolecule synthesis. The current study examined the effects of several resin components on growth and lipid metabolism of oral epithelial cells. Resin discs were fabricated from triethyleneglycol dimethacrylate (TEGDMA) as received from the manufacturer and after removal of the stabilizer methyl ether hydroquinone (MEHQ). Some discs also contained the initiators benzoyl peroxide (BPO) and camphoroquinone (CQ), and/or an activator, dimethylaminoethyl methacrylate (DMAEMA). After polymerization, the ability of components to elute from the discs and alter cell growth and lipid synthesis were assayed by a colorimetric method and thin layer chromatography respectively. Purified TEGDMA had little effect on the cells' growth or lipid metabolism, while TEGDMA containing MEHQ did inhibit growth as well as total polar lipid synthesis. Eluates from discs containing DMAEMA inhibited cell growth as well as decreasing polar lipid formation. However, this same material produced increased synthesis of diglycerides and cholesterol esters. Eluates from BPO-containing discs, as well as those with CQ, with or without DMAEMA resulted in increased levels of diglycerides. These results demonstrate that even after polymerization, components used in dental resins may elute into the immediate environment and alter various cell metabolic processes.

Animals↗

PubMed1996

Biocompatibility of posterior restorative materials.

Biocompatibility of dental materials is an important consideration for the patient, clinician, laboratory technician and manufacturer. This paper examines biocompatibility testing methods and the biocompatibility of posterior restorative materials, including amalgam, casting alloys, resin composites, dentin bonding agents, cements, porcelains and ceramics.

Acrylic Resins↗

PubMed1995

Porphyromonas gingivalis lipopolysaccharide affinity for two casting alloys.

With the exception of plaque, the affinity of biologically active bacterial products for restorative materials and the influence of that affinity on periodontal health has not been detailed. This study recognized that Porphyromonas gingivalis endotoxin, which is cell envelope lipopolysaccharide (LPS) produced by a bacterium that is common to the crevicular microbial flora, has an affinity for dental casting alloys. Regardless of surface finish, no difference in LPS initial adherence or elution was recorded between a type III gold or nickel-chromium-beryllium alloy (p > 0.05), but LPS readily adhered and remained attached to both alloys. LPS affinity could contribute to periodontal inflammation in tissues that approximate restorations fabricated from either alloy.

Bacterial Adhesion↗

PubMed1994

Biocompatibility of visible light-cured resin systems in prosthodontics.

Frequently dental products are introduced that have had little or no biologic testing. Cell culture systems that traditionally have been used for the study of cellular responses have recently been used to assess biocompatibility. This article reviews various cellular toxicity assays and their application to the resin systems used in clinical prosthodontics.

Acrylic Resins↗