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At least 235 records · Page 13Linked to original sources
PubMed2003

The comparative sealing ability of hydroxyapatite cement, mineral trioxide aggregate, and super ethoxybenzoic acid as root-end filling materials.

A comparison was made of the ability of hydroxyapatite cement, mineral trioxide aggregate, and super ethoxybenzoic acid to prevent the leakage of bacteria from root canals, when used as root-end filling materials. The materials were tested in a double-chamber device in which a root segment connects the upper (delivery) chamber and the lower (receiving) chamber. The root segment was prepared by having the root canal instrumented to a #45 file, and a 3-mm-deep, root-end preparation placed at the apical foramen. The canal of each root segment was filled with gutta-percha, and the root-end preparation was filled with one of three test materials, mixed according to the manufacturer's directions. Negative controls were constructed with sticky wax sealing the apical foramen. A titered suspension of radioactively (3H-thymidine)-labeled bacteria (Enterococcus fecalis) was placed into the delivery chamber, and sterile saline was placed into the receiving chamber such that the apical third of each root section was immersed. At various time points, samples were taken from the receiving chamber, and measured for 3H activity. The results indicated that (a) all the test materials leaked significantly compared with the negative controls; and (b) there was no significant difference found between the leakage rates of the three materials tested.

Aluminum Compounds↗
PubMed2002

Effect of endocrine disrupting chemicals on germinal vesicle breakdown in Xenopus in vitro.

Currently, no standardized and well-validated alternative models exist for screening for progesterone-responsive endocrine disrupting chemicals (EDCs). Because of this, a rapid assay for evaluating progestin/antiprogestin activity using Xenopus oocyte germinal vesicle breakdown (GVBD) as a model was evaluated. Five compounds, including progesterone (P), ethinyl estradiol (EE), ethylene glycol monomethyl ether (EGME), cadmium (Cd), and boric acid (B) were used to validate the model on a preliminary basis. Each test material was tested for progestin/anti-progestin activity. The binding affinity of each test material to the oocyte plasma membrane receptor (OPMR) relative to progesterone was then determined. Results from the present studies suggested that both EE and EGME were capable of inhibiting GVBD in a concentration-dependent manner. Cd had a subtle inhibitory effect at high concentrations. B had no effect on GVBD even at concentrations of 100 mg B/L, and thus appears to have no EDC activity in this model. The binding capacity of the test substances to the OMPR relative to progesterone was low. Thus, the relative inhibitory potential of the test materials study was EE > EGME >> Cd > B. However, the relative binding affinity of the toxicants to the OMPR can be expressed as P >> EGME > EE > Cd > B. Although EE was more effective in inhibiting GVBD, EGME appeared to bind more tightly to the OMPR.

Animals↗
PubMed1991

Important factors for testing barrier materials with surrogate viruses.

This study evaluated bacteriophages phi X174, T7, PRD1, and phi 6 as possible surrogates for pathogenic human viruses to challenge barrier materials and demonstrated some important factors for their use. Chemical incompatibility with test material was demonstrated when lipid-enveloped phi 6 was inactivated by an aqueous eluate of vinyl gloves, but 0.5% calf serum protected phi 6 from the eluate. Low concentrations (2%) of calf serum also prevented the exaggerated binding of the bacteriophages to filters. Recovery of viruses from surfaces decreased with increasing time before recovery. Penetration through punctures displayed different types of kinetics. The combined data indicate that (i) some bacteriophages may serve as surrogate viruses, (ii) experimental conditions determine whether a particular virus is appropriate as a challenge, and (iii) phi X174 is an excellent choice as a surrogate virus to test barrier materials. The data further indicate that before barrier materials are challenged with viruses, adequate tests should be performed to ensure that the virus is compatible with the test material and test conditions, so that meaningful data will result.

Bacteriophage phi X 174↗
PubMed1997

A new method for assessing masticatory performance: a feasibility and reproducibility study.

The aim of this study was to develop a method for assessing masticatory performance based on incorporation of a colour binder in a test material with the presumption that the absorption of the colour is proportional to the total surface area of the masticated material. This was tested in vitro with erythrosin as the colour substance and Praestol 655BC as the colour binder incorporated into Satou's synthetic test material (equal amount of carnauba wax and bariumsulphate). The authors found that the difference in spectrophotometrical absorbance between a standard erythrosin solution and the supernatant of the same solution incubated half an hour with artificially pulverized test material was almost linearly correlated (r = 0.997) with the particle surface. This test material was then fabricated as small tablets and four adults chewed repeatedly five grams of these tablets to assess selectivity and reproducibility of the method. A good selectivity was found in that within the total range of the difference in absorbance (0.47-1.19) an inter-individual difference of more than 0.17 is significant on a 95% level with double experiments. There were no differences in the intra-individual variation for double determinations between immediate repeat and 1 week interval performances but the reproducibility was disturbed when two subjects used their partial dentures.

Absorption↗
PubMed1989

[Study of a particle counting method for index of masticatory efficiency].

The present report discusses our new simplified measuring method of masticatory efficiency by counting particles in the matter of making test materials and the standard equation for subjects with normal dentition. 1. Two kinds of hydrocolloid impression materials, reversible and irreversible, were used as the test materials. 2. For evaluating the shape of test materials, 12 subjects with normal dentition were tested and for calculating the standard equation, 108 subjects with normal dentition were tested. 3. Each subject was investigated by the simplified method of counting particles through a sieve system. The number of remaining particles on the mesh was calculated as a masticatory performance. 4. As indicated in a previous report by Dr. Ozawa about cubical test materials, columnar test materials are easier to make than the others and these were avairable for the present particle counting method for investigating masticatory efficiency. 5. We obtained the standard equation for both kinds of test material using 108 subjects with normal dentition. To simplify the measuring method, we selected the standard equation of a 5-mesh sieve with 10 strokes chewing for the index of masticatory efficiency. The standard equation of a 5-mesh sieve for both test materials are as follows; 1) Reversible hydrocolloid test material: Y = -1.605X+29.058 2) Irreversible hydrocolloid test material: Y = -1.116X+23.868 6. 5, 10-mesh sieve with 10 strokes chewing showed the smallest variation in the individual coefficient of variation with both kinds of test material.

Colloids↗
PubMed2006

Is an antibacterial adhesive system more effective than cavity disinfectants?

PURPOSE: To compare the antibacterial activity of an adhesive system containing an antibacterial monomer MDPB, Clearfil Protect Bond with three different cavity disinfectants, chlorhexidine gluconate-based Consepsis, benzalkonium chloride-based Tubulicid Red and 3% hydrogen peroxide. METHODS: Materials were tested using agar well technique and a tooth cavity model. The test materials were filled in the agar wells of plates inoculated with Streptococcus mutans. After 48 hours of incubation, the zones of inhibitions were measured in millimeters. For the tooth cavity model test, cylindrical cavities were prepared in the flat occlusal dentin of human extracted molars. The teeth were left in a broth culture of Streptococcus mutans at 37 degrees C for 72 hours allowing bacteria to invade. Teeth were then randomly assigned into five groups of five teeth (10 cavity preparations) each. In the first four groups test materials were applied into the cavities following the manufacturer's instructions and the cavities in the fifth group were left untreated for control. The teeth were kept in saline for 72 hours. Standard amounts of dentin chips were obtained from the cavity walls and the number of bacteria recovered was counted. RESULTS: The results were analyzed by ANOVA, Dunnett C and Bonferroni tests. For the agar well technique, Clearfil Protect Bond primer exhibited greater inhibition zones than all three cavity disinfectants (P< 0.05). When tested by the cavity method, the application of Clearfil Protect Bond system resulted in significantly less bacterial recovery than all disinfectants (P< 0.05). For both microbiological methods, there were no significant differences between the antibacterial activities of Consepsis and Tubulicid Red (P> 0.05). They were superior to hydrogen peroxide in the cavity test method (P< 0.05).

Analysis of Variance↗
PubMed2002

Language development in hearing-impaired children. Establishment of a reference material for a 'Language test for hearing-impaired children', LATHIC.

OBJECTIVE: In Sweden, there has previously been no normalised test material for the evaluation of language development in individual hearing-impaired children, and for the assessment of various methods of auditory habilitation. The purpose of the present study was to compose, apply and evaluate a test for language development in hearing-impaired children, and to establish the first set of reference values related to age, sex, type and degree of hearing impairment. METHODS: A test consisting of nine subtests was assembled and developed for, and subsequently applied to, hearing-impaired children in the age range 4-6 years. The inclusion criteria were a pure tone average of 80 dBHL or less and oral language (Swedish) as the first language. Two hundred and eleven hearing-impaired children and 87 normal hearing control children were tested. RESULTS: The results show that: (1) children with hearing impairment-also unilateral-have a delayed language development; (2) the delay is greater in children with larger losses and tends to decrease with increasing age; (3) 6-year-olds with hearing loss greater than 60 dB have not reached the level of the control group; (4) no difference between right- or left sided deafness with respect to language development was observed; (5) a reference material, applicable during clinical assessment, was established for the most common types of hearing impairment. CONCLUSIONS: The test designed gave graded measures of important aspects of language development in hearing-impaired children. The results merit further application of the test material.

Analysis of Variance↗
PubMedDate not supplied

Ethanol and diethyl phthalate: vehicle effects in the local lymph node assay.

The vehicle in which an allergen is presented to the skin has been recognized to have an effect on the skin-sensitizing potency of the allergen. Typical vehicles used to evaluate the skin sensitization potential of fragrance materials include ethanol, diethyl phthalate, or a combination of the two. The authors conducted a series of studies to evaluate each of these vehicles for their utility in the murine local lymph node assay and to investigate the potential differences in skin sensitization resulting from their use. Four fragrance materials were tested in four different vehicles. The test materials were p-t-butyl-alpha-methylhydrocinnamic aldehyde, geraniol, eugenol, and hydroxycitronellal. The vehicles were diethyl phthalate, 1:3 ethanol:diethyl phthalate, 3:1 ethanol:diethyl phthalate, and ethanol. Each of the fragrance materials was tested at five dose levels ranging from 0.3% to 50% w/v. In all four vehicles, each material tested elicited positive responses, exhibiting weak to moderate skin sensitization potential. Overall, p-t-butyl-alpha-methylhydrocinnamic aldehyde exhibited the most potency, followed by eugenol, geraniol, and hydroxycitronellal. The sensitization potential of both p-t-butyl-alpha-methylhydrocinnamic aldehyde and geraniol was greatest when the vehicle was ethanol. The sensitization potential of eugenol was greatest in 3:1 ethanol:diethyl phthalate, but the sensitization potential for hydroxycitronellal was greatest in 1:3 ethanol:diethyl phthalate. The strength of the sensitization response was observed to vary with the vehicle; however, the results did not show any clear pattern of one vehicle over another regarding skin sensitization.

Administration, Topical↗
PubMed1995

Determination of the aerobic biodegradability of polymeric material in a laboratory controlled composting test.

A laboratory method is presented for investigating the biodegradation of an organic test material in an aerobic composting system based on the evolution of carbon dioxide. In addition to carbon conversion, biodegradation can also be monitored through weight loss and physical disintegration. The test method is different from other biodegradation tests, especially aquatic tests, because of the elevated temperature representative for real composting conditions and also because of enhanced fungal degradation activities. A ring test was run using paper and poly-beta-hydroxybutyrate/valerate as test materials and cellulose powder as a reference material. The test results and the experience gained by the participants showed that the method is suitable and practicable. Experience with real technical-scale composting facilities confirms that the method provides test results of high predictive value. The test is designed to become a European Standard in connection with determining the compostability of packagings and packaging materials.

Bacteria, Aerobic↗
PubMed2002

The use of inert carriers in regulatory biodegradation tests of low density poorly water-soluble substances.

Many poorly water-soluble compounds fail regulatory ready biodegradation tests as the method of test material preparation limits the bioavailability of the chemical. The recognised method for delivery of poorly soluble materials into biodegradability tests consists of coating test material inside the test vessel or onto inert substrates (i.e., glass cover slide, boiling beads, filter paper, or Teflon stir bar) that are placed inside the vessels. Volatile solvents are often used to augment this process. Although these substrates work fairly well for delivering many poorly soluble materials into biodegradability tests, they have not been effective in keeping low density, poorly water-soluble substances in the test medium. Soon after medium is added to the test vessels, these chemicals break loose from the substrates and float on the surface where they have limited contact with micro-organisms in the test medium. Hence, there is a reduced potential for measuring substantial biodegradability in the test. This paper describes the work undertaken to establish a standard method of adding low density, poorly water-soluble substances into test vessels of biodegradability studies to ensure these materials remain in contact with micro-organisms in the test medium. The substances are prepared for testing by adsorption onto silica gel followed by dispersion into the culture medium. This method of delivery may provide greater intra- and inter-laboratory consistency in biodegradability test results for low density, poorly water-soluble substances and it may more closely mimic the probable transport and fate of these substances in the environment.

Biodegradation, Environmental↗
PubMed2002

Assessing restorative dental materials: I. Test methods and assessment of results.

Many methodologies are used during the testing of dental materials. Among these are compressive, tensile and flexural strengths, and fracture toughness. However, different tests are relevant to different materials and clinical situations. This paper describes different test methodologies and discusses the substantiation of research claims in publications and advertising.

Compressive Strength↗
PubMed2004

Plantar foot surface temperatures with use of insoles.

PURPOSE: Patients with diabetes are often prescribed foot orthoses to help prevent foot ulcer formation. Orthotics are used to redistribute normal and shear stress. Shear stresses are not easily measurable and considered to be responsible for skin breakdown. Local elevation of skin temperature has been implicated as an early sign of impending ulceration especially in regions of high shear stress. The purpose of this study was to measure the effects of commonly prescribed insole materials on local changes in plantar foot temperature during normal gait. METHODS: Six commonly used foot orthosis materials were tested using the Thermo Trace infrared thermometer to measure foot temperature. Ten healthy adult volunteers without any history of diabetes or abnormal sensation participated in the study. During each trial the subject walked on a treadmill with the test material in the dominant foot's shoe, for six minutes at a speed of four miles per hour and rested for six minutes between trials. Four locations on the foot (hallux, first and fifth metatarsal heads, and heel) and the contralateral bicep temperatures were measured at 0, 1, 3, 5 minutes during the rest period. The order of material and skin location testing was randomized. RESULTS: Significant differences were found between baseline temperatures and foot temperatures for all materials. However, no differences were found between materials for any location on the foot. CONCLUSION: Previous studies have attempted to characterize materials based on laboratory and clinical testing, while other studies have attempted to characterize the effect of pressure on skin temperature. However, no study has previously attempted to characterize foot orthosis materials based on foot temperatures. This study compared foot temperatures of healthy adults based on the material tested. Although this study was unable to distinguish between materials based on foot temperatures, it was able to show a rise in foot temperature with any material used. This study demonstrates a need to a larger study on a population with diabetes.

Adult↗
PubMed2001

Influence of pH and storage time on the sorption and solubility behaviour of three composite resin materials.

OBJECTIVES: The aim of this study was to determine whether pH and time has any influence on the sorption and solubility behaviour of composite resin materials stored in a buffer solution. METHODS: Three hybrid composite restorative resin materials (Spectrum, Z-100 and ArtGlass) with different matrix structure and filler composition were studied. One hundred and twenty specimens of each material were produced according to ISO 4049. The materials were stored in McIlvain's buffer solution at different pH (4, 6 and 8) at 1, 7, 60 and 180 days. pH measurements were carried out before and after completed storage. RESULTS: Time had a significant influence on the sorption and solubility behaviour of the composite resin materials tested. One of the materials Z-100 showed a significant mass increase and/or decrease depending on the pH of the solution. The material Spectrum was significantly influenced by pH, resulting in different sorption depending on the pH of the solution. CONCLUSIONS: Time of storage was important for the sorption and solubility behaviour of the composite resin materials tested. Comparison of solubility for one of the materials showed twice as high values in the present study as previously reported when distilled water was used as storage medium. pH in the solution seems to have an influence on the sorption and solubility behaviour of composite resin materials. The sensitivity of the sorption and solubility behaviour to time and pH of the materials tested seems to be related to the hydrophilicity of the matrix and the chemical composition of the filler.

Absorption↗