Abstract：
:A number of studies have been made investigating the properties of dental prosthodontic soft polymer materials. In such materials, which are used as short-term denture soft liners, the polymer component is complexed with one or more plasticizers. This lowers the glass transition temperature, Tg, of the polymer by allowing greater chain mobility and produces a more flexible material. Little information is available relating to the polymer components of such soft-lining materials. The chemical composition and molecular-weight distribution of a polymer help to determine its ability to form a plasticized soft polymer-gel. In the present work, both pyrolysis depolymerization/gas chromatography (GC) and size exclusion chromatography (SEC) have been used to characterize 11 commercial polymer powders. By use of SEC and polymer standards having a narrow molecular-weight range, it has been possible for accurate molecular-weight distributions to be determined for all 11 powders. The peak molecular weights were found to be between 1.79 x 10(5) and 3.28 x 10(5). These values are above the molecular weight at which chain entanglement occurs. The polydispersity ratios (Mw/Mn) were between 2.09 and 4.48. Methacrylate polymers can be readily decomposed thermally to their constituent monomers, which, once recovered, can be analyzed by gas chromatography. The simple pyrolysis apparatus used in the present study was easily assembled and was capable of producing both qualitative and quantitative results. None of the commercial polymers analyzed gave methacrylate decomposition products with pendant chains greater than ethyl (-CH2-CH3). All of the commercial polymers successfully studied by the pyrolysis test method proved to be poly(ethyl [100-79%]/methyl [0-21%] methacrylate) polymers or co-polymers.
journal_name
J Dent Resjournal_title
Journal of dental researchauthors
Jones DW,Hall GC,Sutow EJ,Langman MF,Robertson KNdoi
10.1177/00220345910700050201subject
Has Abstractpub_date
1991-05-01 00:00:00pages
874-9issue
5eissn
0022-0345issn
1544-0591journal_volume
70pub_type
杂志文章abstract：:With the objective of contributing to the understanding of factors influencing the characteristics of dentition, dental observations from 429 children and adult highland people of western Bolivia are described. Various age, sex, ethnic, and village differences are observed in malocclusion, dental caries, periodontal d...
journal_title：Journal of dental research
pub_type： 杂志文章
doi：10.1177/00220345780570030901
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abstract：:It was the aim of this 24-mo randomized controlled clinical trial to investigate whether the survival of a single median implant placed in the edentulous mandible to retain a complete denture is not compromised by immediate loading. Secondary outcomes were differences in prosthetic complications between the loading pr...
journal_title：Journal of dental research
pub_type： 杂志文章,多中心研究,随机对照试验
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abstract：:A search was made for expression of genes for proline-rich proteins (PRPs) and other salivary-type proteins, including statherin and histatins, in taste-bud tissues of mice and primates because of previous genetic findings in mice (Azen et al., 1986) that Prp and taste genes for certain bitter substances are either th...
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abstract：:Inflammatory conditions as they occur during periodontal disease often result in decreased alveolar bone levels and a loss of connective tissue homeostasis. Here we have focused on the effect of microRNA-138 (miR-138) as a potential regulator of periodontal stem cells as they affect homeostasis during inflammatory con...
journal_title：Journal of dental research
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doi：10.1177/0022034515613043
更新日期：2016-02-01 00:00:00
abstract：:Lipopolysaccharide (LPS) from the Gram-negative pathogen Porphyromonas gingivalis (Pg) stimulates cytokine secretion in immune cells, and thereby initiates the inflammation associated with periodontitis. Modulation of pro-inflammatory cytokine activity is a plausible therapeutic target in periodontal disease. Vasoacti...
journal_title：Journal of dental research
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更新日期：2005-11-01 00:00:00
abstract：:The human temporalis and masseter muscles are not activated homogeneously during static bite force tasks. In this study, we studied the possible existence of regional differences in these muscles under dynamic conditions. Electromyographic (EMG) activity was recorded by means of bipolar fine-wire electrodes. Six elect...
journal_title：Journal of dental research
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doi：10.1177/00220345950740061201
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abstract：:In the past two decades, accumulated evidence has clearly demonstrated the inhibitory effects of laser irradiation on enamel demineralization, but the exact mechanisms of these effects remain unclear. The purpose of this study was to investigate the effects of low-energy CO2 laser irradiation on demineralization of bo...
journal_title：Journal of dental research
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doi：10.1177/00220345000790091401
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abstract：:Studies on mechanisms underlying the differentiation of dental pulp stem cells are critical for the understanding of the biology of odontogenesis and for dental tissue engineering. Here, we tested the hypothesis that stem cells from exfoliated deciduous teeth (SHED) differentiate into functional odontoblasts and endot...
journal_title：Journal of dental research
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更新日期：2010-08-01 00:00:00
abstract：:The surface enamel of fetal bovine teeth was stained with GBHA to indicate the position of bands of smooth-ended and ruffle-ended ameloblasts relative to the developing enamel. The boundaries of the bands were scored, under a dissecting microscope, and the bulk enamel under each band was collected. The enamel samples ...
journal_title：Journal of dental research
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abstract：:This study demonstrated a correlation between silicon x-ray counts and area fractions of adherent porcelain as determined by point-counting. This correlation has allowed a method to be devised for measuring area fractions of porcelain adherent to porcelain-fused-to-metal (PFM) fracture surfaces. The described method, ...
journal_title：Journal of dental research
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abstract：:The purpose of the study was to determine the exposure times needed to harden a light-activated composite cement through various thicknesses of porcelain. A negative exponential model was developed with which the relative hardness of a composite could be predicted from the product of the exposure time and the square r...
journal_title：Journal of dental research
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更新日期：1989-03-01 00:00:00
abstract：:Since Thewlis found the "two fiber axes" patterns on x-ray diffractograms of human enamel in 1934, many investigators have studied this problem. However, a definite answer has not yet been obtained. The present detailed x-ray diffraction study showed that the "two fiber axes" patterns in human enamel were caused by re...
journal_title：Journal of dental research
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abstract：:Degradation of dentin matrix components within caries dentin has been correlated with the activity of host-derived proteases, such as matrix metalloproteases (MMPs) and cysteine cathepsins (CTs). Since this relationship has not been fully established, we hypothesized that the abundance of MMPs and CTs in caries-affect...
journal_title：Journal of dental research
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journal_title：Journal of dental research
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journal_title：Journal of dental research
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journal_title：Journal of dental research
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更新日期：1995-02-01 00:00:00
abstract：:The recent bioengineering of complex tooth structures from pig tooth bud tissues suggests the potential for the regeneration of mammalian dental tissues. We have improved tooth bioengineering methods by comparing the utility of cultured rat tooth bud cells obtained from three- to seven-day post-natal (dpn) rats for to...
journal_title：Journal of dental research
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abstract：:Amelogenin gene organization varies from 6 exons (1,2,3,5,6,7) in amphibians and sauropsids to 10 in rodents. The additional exons are exons 4, 8, 9, and "4b", the latter being as yet unidentified in AMELX transcripts. To learn more about the evolutionary origin of these exons, we used an in silico approach to find th...
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更新日期：1997-08-01 00:00:00
abstract：:It is shown that the creep behavior of a commercial dispersant-amalgam containing copper is improved by the addition of a manganese-containing alloy. This improvement is apparently obtained without any serious changes in corrosion resistance, provided that no more than 20% of the Mn alloy is added. ...
journal_title：Journal of dental research
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doi：10.1177/00220345780570090601
更新日期：1978-09-01 00:00:00
abstract：:Attempts to produce resin composite with antibacterial properties by incorporation of an antibacterial agent such as chlorhexidine have been reported, but problems can arise due to release of the inhibitory agent from the composite. Such problems may include toxic effects, influence on mechanical properties, and loss ...
journal_title：Journal of dental research
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更新日期：1994-08-01 00:00:00
abstract：:The objective of this study was to calculate the stress distribution induced in anterior metal-ceramic crowns fabricated with either gold-alloy or nickel-alloy copings of reduced thickness using plane stress analyses. Two-dimensional finite element models of three crown designs were subjected to a simulated biting for...
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更新日期：1986-09-01 00:00:00
abstract：:Matrix metalloproteinases (MMPs) produced by resident and inflammatory cells in response to periodontopathogens play a major role in periodontal tissue destruction. Our aim was to investigate the effects of A-type cranberry proanthocyanidins (AC-PACs) on: (i) the production of various MMPs by human monocyte-derived ma...
journal_title：Journal of dental research
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abstract：:Weanling rice rats were fed either standard laboratory chow or Diet 2000. The animals were sacrificed at 4, 8, 12, and 15 weeks. There was an increasing amount of exposed root surface and root surface caries with age in the animals fed Diet 2000. There was exposed root surface but no caries in the animals fed laborato...
journal_title：Journal of dental research
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abstract：:The Kubelka-Munk (K-M) theory provides a reflectance model for translucent materials placed on backings of different colors. We hypothesize that Kubelka-Munk (K-M) theoretical diffuse reflectance spectra of dentin and enamel are in good agreement with observed diffuse reflectance. The aim of this study was to measure ...
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更新日期：2001-02-01 00:00:00
abstract：:Smoking has been established as an important risk factor for periodontal disease and tooth loss. The purpose of this study was a prospective evaluation of the effects of smoking on dental care utilization and its costs, based on data from 5712 males aged 20-59 yrs. Age, dental health behavior, and history of diabetes ...
journal_title：Journal of dental research
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