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Biomedical subjects

G S Schuster

Publications and source records attributed to G S Schuster.

At least 19 recordsLinked to original sources
PubMed1992

Sodium hypochlorite disinfection of irreversible hydrocolloid impression material.

Alginate impression material is one of the most frequently used in dentistry. However, this material is susceptible to dimensional distortion during disinfection because of its hydrophilic nature. This study examined the effects of alginate disinfection using a sodium hypochlorite spray or impression immersion. Spray disinfection of an alginate impression did not cause dimensional differences of the poured stone casts when compared with casts from water-rinsed controls. Immersion disinfection created dimensional distortion of the anterior, posterior, and interarch model segments. Both the spray and immersion treatments equally decreased the surface detail reproducibility. The antimicrobial effects of the spray treatment were similar to those of the immersion treatment, while mere water rinsing resulted in inadequate disinfection.

Aerosols↗
PubMed1992

A comparison of monomer conversion and inorganic filler content in visible light-cured denture resins.

Visible light-cured (VLC) denture resins are relatively new products used for the reline and repair of dentures. The conversion of monomer into polymer in 3 brands of visible light-cured denture resins was investigated. The relationship of the inorganic filler content to this conversion was also studied. It was determined that these reline materials vary in monomer conversion and weight percentage of filler, and this variation is brand dependent. The monomer conversion ranged from 77% to 97%. Significant differences in these values were found when duration of light exposure was increased. In addition, resin nearest to the light source polymerized to a greater extent when compared to resin that was 1 mm deep to this surface, hence furthest from the light source. The inorganic filler content ranged from 0% to 15%. For the resin systems studied, the relationship between monomer conversion and inorganic filler loading was inversely proportional. Results indicated that monomer conversion of VLC repair resins was affected by the duration of light exposure as well as the amount of inorganic filler present in the material.

Acrylic Resins↗
PubMed1992

Cariostatic and ultraconservative sealed restorations: six-year results.

The objective of this clinical study was to determine the ability of an ultraconservative, sealed composite resin restoration, without a traditional cavity preparation and without the removal of the carious lesion, to arrest Class I caries. Tooth preparation was limited to placing a bevel in the enamel. These restorations were compared, over 6 years, with (1) ultraconservative, localized, sealed amalgam restorations with no extension for prevention and (2) traditional, unsealed amalgam restorations with the usual extension for prevention outline form. Caries was arrested by the ultraconservative, sealed composite resin restorations for 6 years. Complete sealant retention on the sealed amalgam restorations was somewhat lower than that on the sealed composite resin restorations; conversely, partial sealant retention was higher for the sealed amalgam group. The marginal integrity of the sealed amalgam restorations was significantly superior to that of the unsealed amalgam restorations. The sealant also protected Class I posterior composite resin restorations against wear.

Adolescent↗
PubMed1992

Sealed restorations: 5-year results.

This clinical study determined the feasibility of a sealed resin composite restoration to arrest dental caries using a minimal tooth preparation: a bevel in enamel only without removal of the carious lesion. These ultra-conservative sealed composite restorations placed over caries (CompS/C) were compared with ultra-conservative sealed amalgam restorations (AGS) that had no "extension for prevention". The CompS/C restorations were also compared with the traditional (unsealed) amalgam restorations (AGU) with the "extension for prevention" outline form. Caries progress, as determined by standardized radiographs, revealed that after 5 years caries remained arrested under the CompS/C restorations; the marginal integrity was similar for the CompS/C and the AGS groups, and exhibited highly significant superiority to the AGU restorations (Chi square, P less than = 0.00004). Complete sealant retention over the amalgam restorations (AGS group) was less than over the composite restorations (CompS/C), and conversely, partial sealant retention was higher for the AGS group. Sealants also appeared to protect the posterior composite restorations against wear.

Adolescent↗
PubMed1991

Correlation of cytotoxicity, filler loading and curing time of dental composites.

Previous studies have shown that dental resin composites tested in cell culture produce cytotoxic effects on human gingival tissues. In this study, the cytotoxic potential of resin composites on primary human gingival fibroblast cultures was evaluated, based on inhibition of cellular protein synthesis measured by [35S] methionine incorporation. Both resin content and percentage of monomer conversion were considered as potential causes of cytotoxicity. Three resin composites were selected to provide a range of filler content from 45 to 86 wt%. Duplicate sample discs (1 mm thick x 10 mm diameter) of each composite were polymerized for 15, 30 and 60 s, followed by heat (110 degrees C, 10 min), and the degree of monomer conversion for each sample group was measured using Fourier transform infrared spectrophotometry. Identically fabricated discs were placed into 35 mm culture dishes with gingival fibroblasts and incubated for 24 h at 37 degrees C. The cell monolayers then were labelled at 24 h with [35S] methionine, washed and solubilized; then incorporated radioactivity was quantitated by liquid scintillation spectrometry. For each composite, as the percentage of monomer conversion increased, cellular toxicity decreased. In comparing different composites having similar monomer conversions, it was found that the filler/resin ratio was not the only factor determining the composite's relative toxicity.

Biocompatible Materials↗
PubMed1991

Ultraconservative sealed restorations: three-year results.

The overall objective of this clinical study was to determine the feasibility of using a sealed composite restoration to arrest caries without the removal of the carious lesion and without the traditional cavity preparation. The minimal tooth preparation (a bevel in enamel) usually did not require any anesthetic injection and conserved tooth structure. These ultraconservative sealed composite restorations placed over caries (CompS/C) have been compared with ultraconservative sealed amalgam restorations (AGS) and with the traditional outline form (unsealed) amalgam restorations (AGU). This clinical study has shown that: (1) caries can be arrested by the CompS/C restoration for a period of three years; (2) the marginal integrity of the AGS restorations showed a definite trend toward improvement as compared to the AGU restorations; and (3) complete sealant retention over posterior restorations was similar in both the CompS/C and the AGS groups during the first two years; however, at Year 3 complete sealant retention was 16 percent higher in the CompS/C than in the AGS group.

Adolescent↗
PubMed1991

Binding, uptake, and release of nicotine by human gingival fibroblasts.

Previous studies of the effects of nicotine on fibroblasts have reported an altered morphology and attachment of fibroblasts to substrates and disturbances in protein synthesis and secretion. This altered functional and attachment response may be associated with changes in the cell membrane resulting from binding of the nicotine, or to disturbances in cell metabolism as a result of high intracellular levels of nicotine. The purpose of the present study, therefore, was to 1) determine whether gingival fibroblasts bound nicotine and if any binding observed was specific or non-specific in nature; 2) determine whether gingival fibroblasts internalized nicotine, and if so, at what rate; 3) determine whether gingival fibroblasts also released nicotine back into the extracellular environment; and 4) if gingival fibroblasts release nicotine intact or as a metabolite. Cultures of gingival fibroblasts were prepared from gingival connective tissue biopsies. Binding was evaluated at 4 degrees C using a mixture of 3H-nicotine and unlabeled nicotine. Specific binding was calculated as the difference between 3H-nicotine bound in the presence and absence of unlabeled nicotine. The cells bound 1.44 (+/- 0.42) pmols/10(6) cells in the presence of unlabeled nicotine and 1.66 (+/- 0.55) pmols/10(6) cells in the absence of unlabeled nicotine. The difference was not significant. Uptake of nicotine was measured at 37 degrees C after treating cells with 3H-nicotine for time periods up to 4 hours. Uptake in pmols/10(6) cells was 4.90 (+/- 0.34) at 15 minutes, 8.30 (+/- 0.75) at 30 minutes, 12.28 (+/- 2.62) at 1 hour and 26.31 (+/- 1.15) at 4 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Altered lipid metabolism in parvovirus-infected cells.

A broad spectrum of cell lipid alterations are known to occur as a consequence of various viral infections. These changes include inhibition of lipid synthesis, stimulation of lipid synthesis and changes in the proportions of various lipids. The current study examined the effects of two parvoviruses on lipids of rat kidney (NRK) cells. Cells were infected with H-1 or Kilham rat virus (KRV) and the effects on 14C-acetate incorporation determined. Results showed that H-1 virus rapidly inhibited lipid formation (in 1 h) while KRV produced a similar effect beginning around 8 h. Pretreatment of the cells with cycloheximide did not alter this response. Fatty acid analysis by gas chromatography did not reveal major alterations in this component of total cell lipids although some fatty acids became undetectable by 18 h post-infection. The data suggest that these parvoviruses, especially H-1 virus, are able to rapidly alter lipid formation following infection and that this effect may be mediated by a virion component.

Animals↗
PubMed1991

Sealed restorations: 4-year results.

The overall objective of this clinical study was to determine the feasibility of using a sealed composite restoration to arrest caries. This objective was to be achieved using minimal tooth preparation for Class I lesions, without the traditional Class I cavity preparation and without the removal of the carious lesion. The minimal tooth preparation consisted of no [corrected] removal of the carious lesion, bevel in enamel only, and usually not requiring any anesthetic injection. These ultra-conservative sealed composite restorations placed over caries (CompS/C) were compared with ultra-conservative sealed amalgam restorations (AGS) and with the traditional (unsealed) amalgam restorations (AGU). This study showed that: 1) caries is arrested under the CompS/C restoration for a period of 4 years; 2) sealant retention is similar in both the CompS/C and the AGS groups; 3) the marginal integrity of the AGS restorations is markedly superior to that of the AGU restorations; and 4) sealant appears to prevent wear of posterior composite restorations.

Adolescent↗
PubMed1990

Glass ionomer and composite resin cements: effects on oral cells.

Because the cement interfaces of restorations can approximate the periodontium, it is critical to determine the biocompatibility of cements. In this study, the cytotoxic potential of resin luting agents on cultures of gingival fibroblasts and oral epithelial cells was evaluated for direct microscopic cytotoxicity, cell morbidity, impaired adherence, and inhibition of macromolecular synthesis. Visible effects ranged from severe toxicity with inadequately polymerized composite resin to no detectable morphologic cell damage by a glass ionomer cement, but inhibition of protein and RNA synthesis varied with the material and cell type. The glass ionomer cement demonstrated no morphologic damage, but exhibited inhibition of macromolecular synthesis in gingival fibroblasts. These results confirmed that in vitro metabolic assays are appropriate for examining the biologic effects of materials.

Cells, Cultured↗
PubMed1990

Indirect immunofluorescence microscopy for the identification of Actinomyces sp. in endodontic disease.

Indirect immunofluorescence microscopy was used to determine the presence of select Actinomyces sp. in a clinical survey of teeth with endodontic disease. Thirty canal samples were tested for the presence of Actinomyces sp.: A. israelii, A. odontolyticus, A. viscosus serotype I, and A. viscosus serotype II. Actinomyces sp. were identified in 18 (60%) samples. A. israelii was most frequently identified with immunofluorescence in 16 (53%) cases examined and was the test organism most often associated with endodontic disease within the restrictions of this study. Positive and negative controls were appropriate to support findings. Indirect immunofluorescence microscopy can be used for the clinical identification of Actinomyces sp. in endodontic disease without the necessity of performing a parallel culture study.

Actinomyces↗
PubMed1990

Binding and uptake of N-nitrosonornicotine by oral epithelial cells.

N-nitrosonornicotine (NNN), a significant nitrosamine component of tobacco binds to and is taken up by cells prior to its activation by intracellular enzymes. A variety of factors may affect the binding of substances to a cell including the cell type, medium composition and the cell membrane lipid composition. This study examines the binding and uptake of NNN to various cell types and relates these to the cells' lipid composition. Hamster buccal pouch keratinocytes were exposed to NNN and the amount of bound NNN determined. This was compared with cells pretreated with 12-0-tetradecanoylphorbol-13-acetate (TPA). While the keratinocytes bound significant amounts of NNN, this binding was not specific. Pretreatment of the cells with TPA significantly increased the amount of NNN bound. Cultures of human gingival fibroblasts and a human liver cell line also bound NNN, in quantities greater than that bound to the keratinocytes. The TPA caused changes in long chain unsaturated fatty acids although major changes in lipid metabolism were not detected. The fatty acid composition of the liver cells more closely resembled that of the TPA treated keratinocytes than the untreated ones. The data suggest that NNN binds to the cells non-specifically and the binding may be related to the amount of long-chain, unsaturated fatty acids present.

Animals↗
PubMed1990

Bacterial penetration of gingiva in the adult beagle dog with periodontitis.

Invasion of gingival tissues by bacteria is thought to be a major factor in development of periodontal lesions. Morphologic studies have revealed bacteria within the pocket epithelium, gingival connective tissues, alveolar bone, and oral epithelium. The current studies are intended to determine whether they are present in healthy and diseased tissues and to identify the microbial source. Five beagle dogs with naturally occurring periodontitis were fed a soft diet. Two quadrants of the dentition of each dog were cleaned regularly and health maintained while others were allowed to develop further disease. After 4 weeks, samples of gingiva were removed both prior to and after the animals were sacrificed by perfusion fixation attempting not to introduce microorganisms. The identical samples were examined by light and scanning electron microscopy for numbers and location of organisms. Their numbers were greater in diseased than in healthy tissues. Furthermore, the quantity was greater in samples taken prior to perfusion fixation than after such treatment, especially in the oral epithelium. The results suggest that normally there are some microorganisms present within the periodontal tissues and that their numbers are greater in diseased tissues. However, the data also indicated that significant numbers may be introduced into the tissues during sampling of unfixed tissues.

Analysis of Variance↗
PubMed1979

Ultrastructural and autoradiographic observations of hamster cheek pouch epithelium grown in vitro.

Epithelial outgrowths from hamster cheek pouch explants were cultured for varying periods of time up to 22 days. Growth of the epithelial sheets was monitored, employing colcemid for demonstrating mitotic activity and tritiated thymidine for DNA synthesis. Mitoses and thymidine uptake were observed among epithelial outgrowths at a considerable distance form the original explant. The epithelial nature of the growing cell sheets was confirmed, employing electron microscopic techniques. The cells exhibited the presence of tonofilaments, desmosomes, ribosomes, Golgi, mitochondria, and rough endoplasmic reticulum. The cultured explants were treated with cyclic nucleotides in order to investigate their modulatory effects on epithelial cell differentiation. Dibutyryl cAMP induced marked mitotic inhibition (46.3%) in our assay, which was increased to 57% with the addition of theophylline. Dibutyryl cGMP showed only a mild (5%) stimulatory effect on mitotic activity. Dibutyryl cAMP enhanced keratinization in the epithelial cell outgrowths with the biogenesis of keratohyalin granules, whereas dibutyryl cGMP did not produce any observable alterations.

Animals↗
PubMed1979

Clinical progress of sealed and unsealed caries. Part II: Standardized radiographs and clinical observations.

At the present time, a trend has been shown that the progress of sealed caries is markedly slowed by sealant therapy as compared to open lesions. This fact has been substantiated by depth measurements, viable bacterial counts, standardized radiographs, and clinical observations. The radiographic and clinical observations agreed with the previously reported two parameters in confirming that (1) sealed cavities showed little or no change in depth and (2) open lesions showed a significant increase in depth as compared to sealed lesions.

Child↗
PubMed1979

Clinical progress of sealed and unsealed caries. Part I: Depth changes and bacterial counts.

1. A method for measuring depth changes in carious lesions has been developed. 2. A method for estimating bacterial viability in the study lesions has been developed. 3. Sealed cavities showed little or no change in depth over a 1-year period. 4. Open lesions showed a significant increase in depth as compared to sealed lesions. 5. Elimination or marked decrease in viable organisms under the sealant occurred.

Bacteria↗
PubMed1979

Effects of in vivo single and multiple isoproterenol injections on subsequently explanted submandibular glands.

The present study reports on the effects of in vivo single and multiple isoproterenol (ISP) injections on the proliferative response of subsequently explanted mouse submandibular glands. Explants were cultured in Waymouth's medium supplemented with 10% fetal bovine serum, and were harvested after 1,2,4 or 6 days in culture. 24 h prior to harvest, the explants were fed medium containing [3H] thymidine. At the time of harvest, the explants were fixed in situ and processed for light-microscopic radioautography. The number of labeled nuclei and the total number of nuclei were counted, and labeling indices were calculated for the control and ISP-treated explant sectons. The results show that the ISP-treated explants had more cells actively synthesizing DNA than did the corresponding control explants after 1 day in culture. In addition, after 2 days in culture, the explants from mice that had received a single dose of ISP incorporated more [3H] thymidine than the corresponding control explants. These results suggest that the in vivo ISP stimulus initiated a hyperplastic response in vivo that was completed during the 1st or 2nd day in vitro.

Animals↗