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At least 253 records · Page 14Linked to original sources
PubMed2005

Surface roughness and gloss of dental materials as a function of force and polishing time in vitro.

OBJECTIVES: The purpose of this study was (1) to analyze the influence of polishing time and press-on force on the surface gloss and roughness of dental materials by using a three-component rubber-based polishing system and to compare the results with those obtained in conjunction with an optimal polishing procedure and application of the specimens to a metal matrix, (2) to estimate the correlation between surface gloss and surface roughness. METHODS: Eight flat specimens were made of each dental material (Tetric Ceram [TC], Tetric EvoCeram [TE], Heliomolar [HM], Compoglass [CO] and Amalcap [AM]) and polished with 4000-grit SiC and a polishing liquid. Subsequently, the mean surface roughness (Ra) was measured with an optical sensor (FRT MicroProf) and the gloss (Gl) with a glossmeter (Novocurve). Prior to polishing the specimens with the polishing system, the surface was pre-roughened with 320-grit SiC paper and polishing was performed under water cooling at 10,000rpm, applying a controlled force of 2N. Each component of the Astropol system (F/P/HP) was used for 30s and Ra and Gl were measured at 5-second intervals. Other specimens of the same materials were polished with a controlled force of 4N or they were applied to a metal matrix and, subsequently, Ra and Gl were measured. To measure the influence of the polishing time on the surface gloss and roughness, repeated ANOVA with post-hoc paired t-tests was carried out in log-transformed Ra and gloss values. To estimate the correlation between Ra and Gl, the Spearman and Pearson correlation was calculated. RESULTS: (1) Surface gloss and surface roughness were time-dependent, showing the greatest improvement already after 5s of polishing with each of the polishing components, with the exception of AM, for which HP was not effective. The patterns of improvement varied considerably from material to material, but they were more consistent with regard to Gl than to Ra. (2) Ra was statistically significantly higher only in TC, TE and CO when 4N of force was applied instead of 2N. (3) Polishing the surface with a polishing machine resulted in a significantly better surface gloss in all materials. (4) After applying the specimens to a metal matrix, the surface roughness of all dental materials was significantly higher when compared to polished specimens except for TC. (5) Correlations between gloss and roughness were in general negative but they were higher for individual measurements compared to the differences between two consecutive measurements. SIGNIFICANCE: Both surface gloss and surface roughness were material-dependent and influenced by the polishing time and applied force. As gloss and roughness proved to be closely associated with each other, gloss assessment may be a sufficient method to screen materials with regard to their polishability.

Acrylic Resins↗
PubMed1990

Measurement of absorbed doses near metal and dental material interfaces irradiated by x- and gamma-ray therapy beams.

Soft-tissue damage adjacent to dental restorations is a deleterious side effect of radiation therapy which is associated with low-energy electron scatter from dental materials of high electron density. This study was designed to investigate the enhancement of dose to soft tissue (or water) close to high electron-density materials and to measure the detailed lateral and depth-dose profiles in soft-tissue-simulating polymer adjacent to planar interfaces of several higher atomic-number materials: 18-carat gold dental casting alloy; Ag-Hg dental amalgam alloy; Ni-Cr dental casting alloy; and natural human tooth structure. Interleaved stacks of calibrated thin radiochromic dosimeter films and tissue-simulating polymer were used for these measurements. Assemblies of these polymer-dosimeter stacks on both sides of the dental materials were irradiated in one fixed direction by collimated 60Co gamma-ray or 10 MV x-ray beams directed perpendicularly to the material interfaces. In another test, designed to simulate more closely therapeutic treatment conditions, a phantom constructed on both sides of a row of restored and unrestored whole teeth (restoration materials: gold alloy crown; Ni-Cr alloy crown; Ag-Hg mesial-occlusal-distal (MOD) amalgam filling; unrestored tooth) was irradiated in one fixed direction by the collimated photon beams. Results indicate that the dose-enhancement in 'tissue' is as great as a factor of 2 on the backscatter side adjacent to gold and a factor of 1.2 adjacent to tooth tissue, but is insignificant on the forward-scatter side because of the predominant effect of attenuation by the high-density, high atomic-number absorbing material.

Chromium Alloys↗
PubMed2003

Sublethal, 2-week exposures of dental material components alter TNF-alpha secretion of THP-1 monocytes.

OBJECTIVES: The aim of this study was to investigate the hypothesis that dental material components alter cytokine secretion from monocytes if applied for several weeks at sublethal doses. The current study significantly extended exposure times of monocytes to the components over times published in previous studies. These exposure times approached the estimated average life span of monocytes in the bloodstream. METHODS: Human THP-1 monocytes were exposed to 2-hydroxyethylmethacrylate (HEMA, 0-1.2mmol/l), triethyleneglycoldimethacrylate (TEGDMA, 0-0.75mmol/l), Hg(2+) (0-2 micromol/l), or Ni(2+) (0-20 micromol/l) for 2 weeks. The cells were then collected and additionally incubated for 24h, with or without bacterial lipopolysaccharide (LPS), a common component of dental plaque. TNF-alpha secretion from THP-1 was determined using by enzyme-linked immunosorbent assay. RESULTS: None of the dental material components induced TNF-alpha from THP-1 by themselves, but LPS alone strongly induced TNF-alpha secretion as expected. HEMA and TEGDMA significantly suppressed (40-70%) TNF-alpha secretion from cells stimulated with LPS. Hg(2+) at 2.0 micromol/l doubled TNF-alpha secretion from THP-1s stimulated with LPS over LPS alone. Ni(2+) did not significantly affect TNF-alpha secretion, with or without LPS exposure. Significance. The results in this study suggest that sublethal, 2-week exposures of some dental material components may alter TNF-alpha secretion from THP-1 monocytes when the cells are challenged. These alterations may influence the biological response of tissues to materials in an inflammatory intraoral environment.

Analysis of Variance↗
PubMed1991

The U.S. Army Institute of Dental Research dental materials shelf-life survey: lot request results.

In an attempt to determine the age of perishable dental materials used at any one time in U.S. Army dental care facilities, a questionnaire was distributed to each U.S. Army Dental Activity supply point. Results reveal that almost half of commonly used perishable dental restorative materials are older than the expiration date, determined by the manufacturer's shelf-life, at the time of use. Materials used in OCONUS facilities are generally several months older than materials within CONUS facilities. Supply personnel could not determine the shelf-life of perishable restorative dental materials from package information in over 25% of all entries.

Dental Materials↗
PubMed1994

Studies on calcium phosphate precipitation: effects of metal ions used in dental materials.

The effects of 26 metal ions, of which 23 are used in dental materials, on the conversion of amorphous calcium phosphate (ACP) to hydroxyapatite (HAP) in vitro were studied. From the effects on both the rate of HAP transformation and induction time, effects of metal ions were classified into three types; inhibitory (in the order: nickel, tin, cobalt, manganese, copper, zinc, gallium, thallium, molybdenum, cadmium, antimony, magnesium, and mercury); ineffective (cesium, titanium, chromium, iron [ferrous], iridium, palladium, platinum, silver, gold, aluminum, and lead); and stimulatory (iron [ferric] and indium). These results suggest that metal ions used in dental materials may modify the precipitation of oral calcium phosphate.

Calcium↗
PubMed1994

Comparison of two methods for measuring generalized wear of dental materials.

The object of this study was to analyze two measuring methods for determining the amount of generalized wear of dental materials. Using a recently developed three-body wear testing machine, generalized wear defect was produced on the surface of various dental materials. Although the generalized wear was defined as the depth of the enamel exposed at the cavity margin for both methods, this depth was measured with two different devices. One is an image-analyzer and the other was a profilometer. From the results of this study, it was confirmed that measurement by means of profilometer gave almost the same wear values with those by image-analyzer. In addition, the measurement by profilometer seemed to be more precise and not very much sophisticated.

Composite Resins↗
PubMed1991

[Biocompatibility of dental materials. Choice of testing methods: to do or not].

Three methods used to study the biocompatibility of dental materials are compared in this article. A glass-ionomer cement, Vitrabond, was studied, using gutta-percha as the control material. Specimens were standardized according to an original procedure. Unsterilized Vitrabond implants were used, because UV rays modify the material. Intraperitoneal Vitrabond implants increased the macrophage population in rats after 24 hrs. This was caused by the surgical trauma and indicates that this method is unreliable. The intramuscular placement of Vitrabond provoked well defined lesions after a week. The use of histochemical techniques on frozen muscle demonstrated that the concentration of succinic deshydrogenase and acid phosphatase enzymes were altered when compared to the control lesions. A comparison of enzymatic lesions and an evaluation of the areas of cellular growth inhibition during in vitro experiments using a computer image analyzer leads to quantitative conclusions that Vitrabond is a cytotoxic material. The simultaneous use of histochemical techniques on muscle tissue and cell culture in vitro enhances the validity of methods used to evaluate the biocompatibility of dental materials. These methods may be used to test the toxicity of various materials. Nevertheless, for a more complete evaluation of these materials, the allergenicity and carcinogenicity potential of these products should be evaluated, prior to the final verdict as to their biocompatibility.

Animals↗
PubMed1994

Clinical testing of dental materials--histological considerations.

In order to assess the biocompatibility of dental materials, clinical studies, as well as in vitro studies, are needed. Although no bacteria were detected inside tubules, pulp reactions were observed when either adhesives of the last generation aiming to create an hybrid layer were used or restorative materials controlling the interface between the biomaterial and dental tissues. However, the reactions were feeble to moderate. Reparative dentine seldom appeared after such treatments. Differences between odontoblast and pulp cells, the nature of the lesion (necrosis or apoptosis), and differences between sound experimental and carious teeth seen in the real clinical situation are discussed in the context of in vivo human studies.

Adolescent↗