PubMed Health⌕ Search

Biomedical subjects

K L Knoernschild

Publications and source records attributed to K L Knoernschild.

At least 19 recordsLinked to original sources
PubMed2001

Effect of pH on endotoxin affinity for metal-ceramic alloys.

STATEMENT OF PROBLEM: Crevicular pH may modify bacterial endotoxin affinity for high-noble metal-ceramic alloys. PURPOSE: Porphyromonas gingivalis lipopolysaccharide (LPS) affinity for 3 metal-ceramic alloys at 3 different pH levels was compared in vitro by measuring adsorption to and release from the alloy surface. MATERIAL AND METHODS: Metallographically polished disks were fabricated from Pd-Ag-Sn, Au-Pd-Ag-Sn-In, and Au-Pd-In-Ga alloys. Clean disks were placed individually into 1 mL at pH 6.5, 7.0, or 7.5 phosphate-buffered saline solution containing 0.9 endotoxin units per square millimeter tritiated LPS (n = 3 disks per alloy-pH group). The disks were incubated for 24 hours at 37 degrees C before being transferred to LPS-free buffer and incubated, again for 24 hours at 37 degrees C, to evaluate elution. This transfer continued at 24-hour intervals up to 96 hours total elution incubation. Lipopolysaccharide adsorption to and elution from disks was determined through liquid scintillation spectrometry. Adsorption data were evaluated with a 2-way analysis of variance (alpha=.05) and the post hoc Tukey honestly significant difference test. RESULTS: Lipopolysaccharide adsorption values ranged from 0.48 +/- 0.04 EU/mm(2) for the Au-Pd-Ag-Sn-In alloy at pH 7.5 to 0.75 +/- 0.04 EU/mm(2) for the Pd-Ag-Sn alloy at pH 6.5. Alloy type (P=.0001) and environmental pH (P=.0001) significantly influenced adsorption. Adsorption to the Pd-Ag-Sn and Au-Pd-In-Ga alloys at pH 6.5, 7.0, and 7.5 were similar and decreased with increasing pH. In contrast, adsorption to the Au-Pd-Ag-Sn-In alloy was significantly less than to other alloys at pH 6.5 but did not differ at other pH levels. Lipopolysaccharide release from the alloy surface could not be detected. CONCLUSION: P. gingivalis LPS affinity for metal-ceramic alloys was modified by environmental pH. The degree of LPS adsorption depended on the composition and surface chemistry of each alloy.

Adsorption↗
PubMed2000

Periodontal tissue responses after insertion of artificial crowns and fixed partial dentures.

PURPOSE: The purpose of this review was, first, to critically evaluate published evidence on the effects of artificial crowns and fixed partial dentures (FPDs) on adjacent periodontal tissue health, and second to synthesize this evidence into meaningful summaries. Restoration qualities that contribute to inflammatory responses were identified based on strength of evidence, and variables that should be controlled in future investigations were outlined. Such information is necessary to accurately predict the prognosis of periodontal tissues adjacent to crowns or FPDs. METHODS: Clinical trial and epidemiologic evidence published in English was collected. The effects of crowns or FPDs on gingival inflammation, probing depths, and bone loss were evaluated based on accuracy of measurement, reliability of measurement, and/or appropriateness of data analysis. RESULTS: Crowns and FPDs increased the incidence of advanced gingival inflammation adjacent to restorations, particularly if restorations had intracrevicular finish line placement, poor marginal adaptation, or rough surfaces. However, because of the limitation in the accuracy and reliability of probing depth measurements, reports of greater mean probing depths of crowned teeth, which tended to be less than 1 mm greater than control teeth, should be questioned. Finally, crowns and FPDs in general did not accelerate the rate of adjacent bone loss. CONCLUSION: Clinically deficient restorations, as well as clinically acceptable restorations, can contribute to gingival inflammation. However, with the limitations of the applied methods of measurement, current evidence has not shown an increased attachment loss adjacent to crowns or FPDs. Future trials should document periodontal health before therapy and periodically after restoration insertion so that each tooth serves as its own control. In future studies, the periodontal disease history of the patient, the influence of the restoration on plaque formation, and the composition of the crevicular microflora must be recorded.

Alveolar Bone Loss↗
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↗
PubMed1998

An in vivo study of voluntary mandibular lateral translation concerning its existence, magnitude, and timing.

STATEMENT OF PROBLEM: The existence of mandibular lateral translation and the approaches to its measurement and interpretation by using a pantograph are controversial. PURPOSE: This study evaluated the validity of using a pantograph to measure mandibular lateral translation and analyzed human pantographic tracings to determine whether they exhibited mandibular lateral translation. MATERIAL AND METHODS: A pantograph was modified by adding 2 posterior horizontal recording tables and styli at the transverse horizontal axis. Pantographic tracings of 25 human subjects were compared with the corresponding theoretically determined values for tracings that exhibited only rotation with no translation. Differences in the tracings at 2 pantographic recording table locations, relative to the transverse horizontal axis, were also compared. RESULTS: The character of the lateral component of 100 pantographic tracings all differed from the lateral component of theoretically determined values for pure rotation. In 64% of tracings, over 50% of the total mandibular lateral translation occurred by the first 1 mm of forward movement of the nonworking side condyle. In 94% of tracings, more than 50% of the translation had occurred in the first 3 mm of forward movement. For the pantographic system used, the amount of mandibular translation represented in the tracing was not changed by altering the posterior horizontal recording table position in the anterior-posterior direction, relative to the transverse horizontal axis. CONCLUSION: All subjects showed evidence of mandibular lateral translation. New definitions for timing of mandibular lateral translation are proposed. Of the tracings, 64% were classified as exhibiting early translation, 30% as intermediate, and 4% as late mandibular lateral translation.

Adult↗
PubMed1997

Lipopolysaccharide affinity for titanium implant biomaterials.

STATEMENT OF PROBLEM: Lipopolysaccharide (LPS) affinity for titanium implant biomaterials could affect crevicular LPS concentrations and thereby influence periimplant inflammation. PURPOSE OF STUDY: The purpose of this study was to evaluate Porphyromonas gingivalis and Escherichia coli LPS affinity for titanium biomaterials groups that differed in surface oxide composition and surface roughness. MATERIAL AND METHOD: Polished and abraded grade 1 commercially pure titanium and grade 5 alloyed extra low interstitial titanium specimens were treated with 10 EU/mm2 and radiolabeled LPS. RESULTS: The resultant mean +/- SD LPS adherence values ranged from 4.17 +/- 0.29 to 4.79 +/- 0.40 EU/ mm2. No difference in adherence and elution was indicated on the basis of LPS type, surface oxide composition, or surface roughness. Moreover, P. gingivalis and F. coli LPS desorption was below detection. CONCLUSION: Clinically, the high affinity of both LPS types for titanium biomaterials may adversely influence the periimplant tissue response.

Adsorption↗
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

Porphyromonas gingivalis endotoxin affinity for dental ceramics.

This study evaluated the effects of chemical composition, surface treatment, and initial exposure dose on Porphyromonas gingivalis lipopolysaccharide adherence to and elution from dental ceramics. Lipopolysaccharide, commonly known as endotoxin, can initiate a variety of biologic responses. Opaque, body, and Dicor ceramic disks were individually exposed to 250, 1000, or 2500 EU/ml 3H-lipopolysaccharide and incubated for 24 hours at 37 degrees C. Disks were then transferred to fresh lipopolysaccharide-free water and incubated for up to 96 hours to evaluate elution. Mean initial lipopolysaccharide adherence ranged from 0.397 +/- 0.048 EU/mm2 to 5.056 +/- 0.117 EU/mm2. Greater initial exposure levels resulted in greater adherence, and at higher lipopolysaccharide exposure levels, lipopolysaccharide adherence differences were based on ceramic type. Mean lipopolysaccharide elution levels ranged from 0.063 +/- 0.02 EU/mm2 to 0.00 EU/mm2 at 96 hours for all groups. Greater initial adherence resulted in greater elution. Ceramic type did not affect elution. Surface finish affected elution at the 2500 EU exposure level. The affinity of lipopolysaccharide for dental ceramics could contribute to a periodontal inflammatory process.

Adhesiveness↗
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↗
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

Cytotoxicity of eluates from light-polymerized denture base resins.

This study examined the metabolic effects of eluates from four light-polymerized denture base resins and one heat-polymerized denture base resin on oral epithelial cells in vitro. The eluate was cell culture medium that contained either or both of apparently nonpolymerized components and reaction products that diffused out of the resin samples. Eluates were prepared by daily transfer of sample disks in a cell culture medium over 10 days. Toxicity of eluates was tested immediately after transfer (fresh) and after storage for 30 days (aged) by use of radioisotope incorporation and cell viability studies. The fresh eluates inhibited cell metabolism, whereas the aged eluates stimulated then inhibited the responses. Results suggest that the components that leach out of the tested materials do so at different rates and have prolonged toxic effects on cells. Thus soaking prosthesis in water before insertion may be beneficial.

Acrylic Resins↗
PubMed1994

Endotoxin affinity for provisional restorative resins.

PURPOSE: This study compared the relative affinity of Porphyromonas gingivalis and Escherichia coli endotoxin, bacterial cell envelope lipopolysaccharide (LPS), for three provisional resins. MATERIALS AND METHODS: As-polymerized and pumiced polymethyl methacrylate and polyethyl methacrylate resin discs were exposed to 1,000 endotoxin U/mL P. gingivalis or E. coli LPS in water for 24 hours at 37 degrees C, whereas control discs were placed in LPS-free water. LPS-treated discs were transferred at 24-hour intervals to fresh, LPS-free water for up to 96 hours, and the incubated eluates were tested for the presence of LPS. RESULTS: Initial adherence of P. gingivalis LPS to as-polymerized and pumiced-finish resin was a function of resin type, but surface characteristics modified adherence levels. When steady rates of elution were reached at 72 to 96 hours, as-polymerized specimens released significantly greater LPS levels than pumiced samples. Comparison of initial adherence of P. gingivalis and E. coli LPS with pumiced resins showed that adherence was based on a combination of LPS and resin type. P. gingivalis LPS had a greater relative affinity for polyethyl methacrylate, and E. coli LPS has a greater relative affinity for polymethyl methacrylate. Regardless of resin type, P. gingivalis LPS eluted at levels greater than E. coli LPS. CONCLUSIONS: The affinity of LPS for provisional resins seems to be a function of selective interactions based on the chemical nature of the resin, the surface finish of the resin, and the molecular structure of the LPS.

Analysis of Variance↗
PubMed1993

Enhancing retention in complete dentures for patients with atypical muscle attachments: case reports.

Preprosthetic surgery is often indicated to obtain a firm, resilient covering that is uninterrupted by frena, scars, or redundant tissue. However, surgical intervention is contraindicated for some patients, especially the medically compromised. This paper presents a viable alternative to surgical intervention of atypical tissue attachments--the use of beading on the master cast. This procedure requires minimal time and is easily accomplished.

Contraindications↗
PubMed1993

A zinc phosphate cement-luted and resin-luted fixed partial denture: a case report.

An innovative fixed partial denture design for restoring a posterior edentulous space is described. The distal retainer is conventionally luted with a zinc phosphate cement, and the mesial retainer is luted with a resin cement. Contingency planning, which involves placement of a nonrigid connector between the pontic and the distal retainer, allows recementation of the resin-luted segment if the resin bond fails.

Adult↗
PubMed1992

Overdentures and the periodontium.

Several periodontal factors are critical to the prognosis of overdenture abutment teeth. This literature review outlines these factors and discusses the documented effects of long-term overdenture use on periodontal health. The efficacy of a professional periodontal maintenance program, which is coordinated with a home oral hygiene program, is related to the success of overdenture therapy.

Dental Abutments↗
PubMed1991

Transcranial radiography and linear tomography: a comparative study.

There is continual controversy concerning the use of radiographs to determine the position of the mandibular condyle within the glenoid fossa for the diagnosis and treatment of temporomandibular disorders. This study compared joint space measurements from transcranial radiographs and linear tomographs with the anatomic joint space to determine whether condylar position could be accurately recorded radiographically. Anterior, superior, and posterior joint space dimensions were measured from projected radiographs with a sonic digitizer, whereas anatomic joint space dimensions were recorded from the thickness of polyether impressions of the joint space. Posterior/anterior joint space ratios were used to classify relative condylar position as anterior, concentric, or posterior. The Pearson correlations (alpha = 0.05) were calculated to determine the consistency between radiographic and anatomic joint space ratios. The corrected and standard transcranial projections did not accurately reproduce the anatomic joint spaces or the relative condylar positions. Only the corrected tomographic projection accurately reflected the condyle-fossa relationships.

Arthrography↗
PubMedDate not supplied

The effect of pH on the cytotoxicity of eluates from denture base resins.

This in vitro study examined the effects of environmental pH on elution of potentially toxic substances from heat-, light-, and dual- (chemical plus light) polymerized denture base resins. Eluates were prepared by daily transfer of disks to fresh buffers at pH 4.0, 5.0, and 6.8 over a 5-day period. Oral epithelial cells were plated in culture dishes in medium containing the eluate. After 24 hours, cellular RNA synthesis was assessed by measuring tritiated uridine uptake. Effects of materials were compared to identical cultures that contained the appropriate buffer without the eluate. The results indicate that the cytotoxic components leach out of the denture base resins in different amounts and at different rates, and the amount of leaching can be affected by pH.

Acrylic Resins↗