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PubMed1977

Effect of a Ca(OH)2 solution and a chlorhexidine based detergent on the microbial activity of human carious teeth.

Occlusar carious lesions from human molars, preserved in continuous humidity after extraction, were removed using conventional clinical techniques. Bacteriological samples were taken after rinsing the cavity with water only, after experimentally infecting the cavity and after treating uninfected cavities either with a saturated Ca(OH)2 solution or with a chlorhexidine based detergent. The samples were cultivated on blood agar plates aerobically and anaerobically. Cavities rinsed with water only showed very sparce bacterial growth. After experimental infection the growth was significant, but decreased radically after treatment with the test materials. In order to describe the effect of the two test materials on the microbial enzyme activity in infected dentin, cryostat sections of 10 micrometer were prepared from undermineralized carious dentin fragments excavated from freshly extracted human teeth. Conventional histochemical techniques were applied to demonstrate the aminopeptidase activity in the sections using N-L-leucyl-2-naphthylamide as a substrate. The aminopeptidase activity of carious dentin was inhibited totally with the Ca(OH)2 solution, whereas the chlorhexidine based detergent had no effect on the enzyme activity.

Aminopeptidases↗

PubMed2000

Role of preconditioning and recovery time in repeated testing of aortic valve tissues: validation through quasilinear viscoelastic theory.

We investigated how preconditioning history and specimen recovery time affect the accuracy of measurements of mechanical properties obtained from sequential, repeated materials testing of porcine aortic valve (PAV) cusps. Strain history protocols were modeled by quasilinear viscoelastic theory and the results compared with the experimental data. Assuming that the model was predictive, the accuracy of predicting experimental data was related to the suitability of the materials testing protocol. We found that the preconditioned state of the PAV material was not unique but was a function of the deformation history that had occurred before the preconditioning cycles. Preconditioning without an adequate rest period between tests increased predictive errors, whereas allowing the material to rest without preconditioning reduced errors. Modeling more of the strain history reduced errors for specimens briefly rested between tests but had no impact on specimens with long rest periods. The smallest predictive errors were obtained for a loading protocol with a 24 h specimen recovery period followed by material preconditioning. We recommend the use of this protocol for estimating material properties of PAV tissues.

Animals↗

PubMed1985

False-positive, follicular and irritant patch test reactions to metal salts.

853 hard metal workers were patch tested with nickel sulphate 5%, potassium dichromate 0.5% and cobalt chloride 1%, each in petrolatum. Non-allergic reactions appeared in 6.5% of the nickel tests, 13% of the chromium tests and 18.3% of the cobalt tests. Most of the individuals with positive, poral or pustular reactions were retested with serial dilutions of metal salts in pet. and in water. The accuracy of a positive initial nickel reaction was 83%, a chromium reaction 40% and a cobalt reaction 62%. The nonallergic reactions were partly reproducible and correlated with both the type of patch test material and with individual factors. Weak and moderately strong positive patch test reactions to metal salts may be irritant and should be checked with serial dilution tests or at least be retested. A reduction of the cobalt chloride concentration from 1% to 0.5% in the standard test material is discussed.

Chromates↗

PubMed1991

[The x-ray opacity of tooth-coloring inlay materials and composite cements].

For a proper radiographic diagnosis of secondary caries and interproximal overhangs or undercuts, tooth colored inlays and their appropriate luting agents have to be radiopaque. With the help of a spectrophotometer the radiopacity of 1 mm thick samples made of enamel, dentin, seven tooth colored inlay materials and seven composite cements was quantitated and related to 99.5% pure aluminum. The mean radiopacity values of three inlays (two of them significantly, p less than 0.05) and of three composite cements (one of them significantly, p less than 0.05) were lower than enamel. All other materials tested exhibited a higher radiopacity than enamel. A radiopacity value of 1 mm thick samples greater than 2.5 mm of 99.5% pure aluminum is advocated by the authors. Four of the materials tested fulfilled this requirement.

Color↗

PubMed2001

Development of a new test for mechanical irritation: behind the knee as a test site.

BACKGROUND/AIMS: Certain consumer products, such as feminine hygiene products, and baby and adult diapers, are worn for prolonged periods of time in close proximity to the skin. A sensitive test method was needed to evaluate these products and their components for the potential to cause mechanical irritation during use. METHODS: We investigated several test sites on the body where normal, daily activities provided the opportunity for movement and, therefore, friction. These test sites were: the back of the knee, the axilla, and the wrist. Three exposure regimens were tested: 6-h daily for 4 days, 24-h daily for 3 days, and 24-h daily for 4 days. Controls consisted of satin fabric (a non-irritating material) or burlap (an irritating material). Test materials were secured to the test sites using an Ace elastic bandage (on the back of the knee), a snug fitting garment (on the axilla), or an athletic band (on the wrist). Test sites were scored for irritation on a visual scale prior to the initial application and 30-60 min after removal each day. Data were evaluated for the ability to reliably detect irritating materials, and for the ability to consistently differentiate between irritating and non-irritating materials. Quantitative measures of these abilities were used to rank the overall effectiveness of various test protocols as a model for mechanical irritation. RESULTS/CONCLUSION: The results of these studies indicated that a protocol using the back of the knee as a test site with an exposure regimen of 6-h daily for 4 days, best met the success criteria for an effective test system for evaluating mechanical irritation.

Adolescent↗

PubMed1977

[Development of a new testmethod for surface disinfection procedures. III. The impression method: influence of the test surface material and the types of microorganisms on the recovery rate (author's transl)].

The preceding test results appear to favour the impression method used for the testing of surface disinfection procedures. Further investigations were concerned with the selection of a suitable germ carrier. The high recovery rate of the bacteria and the invariably uniform quality of the germ carrier are the decisive criteria. Since a dependence on the type of germ was also to be expected, we checked Staph. aureus, Str. faecalis, E. coli, Kl. pneumoniae and P. aeruginosa for their behaviour on PVC, varnished wooden surfaces, V 2A, rough and smooth glass, resopal, ceramic tiles with dull and glazing finish as well as on plywood. The germ carriers were contaminated quantitatively, dried, sprayed with distilled water to stimulate disinfection and examined after they were allowed to react for a period of 6 hours. A set of 10 germ carriers was examined simultaneously with 10 Rodac impressions. The data were checked by variance analytical methods and evaluated on the mean (or median) values. It was found that while the initial germ number was kept equal OP tiles and V 2A steel produced the highest germ yield. Plywood proved largely unsuitable. Among the test germs, E. coli and Kl. pneumoniae had the lowest adhesion; it was inferior to that of staphylococci and pseudomonads. However, for these 4 germ types 3 impressions per germ carrier suffice for a reliable assessment based on computations. The yield amounts to more than 90 per cent. 94 per cent of the Streptococci were also recovered with 3 impressions, but the absolute germ quantity was low. The use of this type of germ can be recommended only with reservation.

Bacteriological Techniques↗

PubMed2003

Encrustation and strength retention properties of the self-expandable, biodegradable, self-reinforced L-lactide-glycolic acid co-polymer 80:20 spiral urethral stent in vitro.

PURPOSE: Encrustation of urological stents is a clinical problem. The chemical composition and surface properties of the devices have a marked effect on its incidence. The ability of the stent to prevent duct collapse depends on its compression strength, which decreases as degradation progresses. We have developed a new self-reinforced, L-lactide-glycolic acid co-polymer with a molar ratio of 80:20 (SR-PLGA 80/20), that is the SpiroFlow (Bionx Implants, Ltd., Tampere, Finland) stent. We compared the resistance to encrustation of the new stent material to that of 2 temporary metallic stents, Prostakath (Doctors and Engineers, Inc., Copenhagen, Denmark) and Memokath 028 (Engineers and Doctors A/S, Ltd., Kvistgård, Denmark). In addition, mechanical compression properties during degradation were investigated. MATERIALS AND METHODS: For encrustation studies 7 mm segments of the test material of the SR-PLGA 80/20, Prostakath and Memokath stents were incubated in vitro in sterile artificial urine for 4 and 8 weeks, and the SR-PLGA 80/20 also for 12 weeks. After incubation the specimens were fixed in glutaraldehyde, critical point dried and coated with gold in sputter for scanning electron microscope analysis. Analysis was done at 100x magnification in 5 randomly selected areas per sample. Results are presented as a median percent of the whole analyzed area covered by encrustation in each tested material. For compression strength studies 20 mm pieces of manufactured SR-PLGA 80/20 spiral stent wire were similarly incubated in sterile artificial urine for 12 weeks. Measurements were made by compressing the specimens between 2 parallel planes at 2, 4, 6, 8 and 12 weeks. All analyses were made in triplicate. RESULTS: The areas covered by encrustation at 4 weeks were 8.01% for the Memokath, 1.49% for the Prostakath and 0% for the SR-PLGA 80/20. At 8 weeks the percent was 28.4%, 4.1% and 0.12%, respectively, remaining steady at 0.12% in the SR-PLGA 80/20 at 12 weeks. Compression strength of the SR-PLGA stent remained stable up to 6 weeks, after which it decreased rapidly. CONCLUSIONS: The new SR-PLGA 80/20 material is markedly more resistant to encrustation than metallic urethral stent materials and it retains compression strength up to 6 weeks, which is long enough for temporary stenting for most clinical indications in urology. Thus, the new stent is well suited to future clinical use.

Absorbable Implants↗

PubMed1995

Minimized virus binding for tests of barrier materials.

Viruses are used to test the barrier properties of materials. Binding of virus particles during passage through holes in the material may yield misleading test results. The choices of challenge virus and suspending medium may be important for minimizing confounding effects that might arise from such binding. In this study, different surrogate viruses, as well as different support media, were evaluated to determine optimal test parameters. Two membranes with high-binding properties (nitrocellulose and cationic polysulfone) were used as filters to compare binding activities of different surrogate challenge viruses (MS2, phi X174, T7, PRD1, and phi 6) in different media. The media consisted of buffered saline with surfactants, serum, or culture broth as additives. In addition, elution rates of viruses that bound to the membranes were determined. The results suggest that viruses can bind by hydrophobic and electrostatic interactions, with phi X174 displaying the lowest level of binding by either process. The nonionic detergents Triton X-100 and Tween 80 (0.1%) equally minimized hydrophobic interactions. Neither anionic nor cationic surfactants were as effective at nontoxic levels. Serum was effective at reducing both hydrophobic and electrostatic binding, with 2% being sufficient for eliminating binding under our test conditions. Thus, phi X174 remains the best choice as a surrogate virus to test barrier materials, and Triton X-100 (0.1%) remains a good choice for reducing hydrophobic binding. In addition, binding of viruses by barrier materials is unlikely to prevent passage of blood-borne pathogens.

Adsorption↗

PubMed1997

In vitro effects of alcohol-containing and alcohol-free mouthrinses on microhardness of some restorative materials.

Daily application of mouthrinses has been recommended for the prevention and control of caries and periodontal disease. The aim of this study was to evaluate the effect of alcohol-containing and alcohol-free mouthrinses on the microhardness of three restorative materials. Materials tested included visible light cured (VLC) composite resin (Amelogen), VLC glass-ionomer cement (Fuji II LC) and a fissure sealant (Ultra Seal XT). Eighteen cylinders of each restorative were fabricated and initially stored in distilled water for 24 h. Six samples of the restoratives were stored for 12 hours to simulate a 2 min/day for 1 year exposure to mouthrinses in the following solutions: distilled water (control), alcohol-containing mouthrinse (Viadent) and alcohol-free mouthrinse (Rembrandt). At the end of the test period microhardness was measured with a Tukon microhardness tester. Kruskal-Wallis one-way analysis of variance was used to analyse the data. Both mouthrinses affected the hardness of the materials tested.

Alkaloids↗

PubMedDate not supplied

Effect of dentinal tubule orientation on the microtensile bond strength to primary dentin.

Direction of dentin tubules is an important factor that affects bond strength of contemporary adhesive materials. Because conservative proximal cavity preparations in primary teeth contain more dentin tubules running oblique or parallel to the cavity walls, this study was conducted to evaluate the influence of tubule orientation on the bond strength to primary dentin. A polyacid-modified resin composite material was used as the test material. A microtensile test was utilized to enable evaluation of bond strengths in three different tubule orientations (perpendicular, oblique, parallel) following aging of the resindentin bonds by long-term immersion of the test samples in water. Samples bonded parallel to the dentin tubules showed the highest microtensile bond strength, followed by the oblique and perpendicular groups. Statistical analysis of the data showed no significant difference between the bond strength of parallel and oblique groups. Independent of the tubule orientation, all samples revealed cohesive fracture within dentin.

Analysis of Variance↗

PubMed2004

C-reactive protein and white blood cell count increases in the first 24 hours after acute stroke.

UNLABELLED: Levels of C-reactive protein (CRP) and white blood cell count (WBC) in acute stroke may reflect the stroke lesion itself or pre-existing factors such as infections, smoking or atherosclerosis. The aim of this study was to investigate the relation between CRP and WBC levels and time from onset of stroke, stroke severity and outcome. PATIENTS AND METHODS: The analyses were based on 719 patients in whom WBC test material was obtained within 9 h of stroke onset and CRP test material within 24 h of stroke onset. Stroke severity was assessed by the Scandinavian Stroke Scale Score on admission and outcome by death 7 days, 3 months and 1 year after symptom onset as well as modified Rankin Scale 3 months after stroke onset. RESULTS: CRP and WBC levels correlated significantly with time from symptom onset as well as with stroke severity and outcome. Levels of CRP and WBC were higher in later determinations in severe stroke. In multivariate logistic regression analysis, CRP(+10 mg/l) was independently related to 1-year mortality (OR 1.1, 95% CI 1.02-1.2). CONCLUSION: Levels of WBC and CRP increase within the first 24 h in patients with severe stroke. CRP but not WBC is related to long-term mortality possibly by reflecting the vascular risk profile.

Aged↗

PubMed2003

Bond strengths of polyacid-modified resin composites and a resin-modified glass-ionomer cement to primary dentin.

PURPOSE: To evaluate the bond strengths of three polyacid-modified resin composites and one resin-modified glass-ionomer cement to caries-simulated primary dentin after 18-months' water immersion. METHODS: Dyract AP, Compoglass F, F2000 and Vitremer were used as test materials. Standardized preparations cavities with a C-factor of 5 were prepared in primary molars. Half of the cavities were stored in a demineralizing media for 7 days to simulate caries-affected dentin. Thereafter, all preparations were restored with the test materials, after which the specimens were stored in water for 18 months, changing the water every week. The specimens were subjected to a microtensile test and all bond strength data (in MPa) were statistically analyzed using one-way analysis of variance (ANOVA) and Tukey HSD tests at P < 0.01. RESULTS: The mean microtensile bond strength to normal primary dentin specimens were 11.2 +/- 1.5 (Dyract AP), 10.6 +/- 2.1 (Compoglass F), 10.8 +/- 1.1 (F2000) and 7.3 +/- 1.6 (Vitremer), while those to the caries-simulated dentin were 4.1 +/- 0.7 (Dyract AP), 3.0 +/- 0.6 (Compoglass F), 2.3 +/- 0.9 (F2000) and 1.9 +/- 0.5 (Vitremer). SEM evaluation of the unfractured specimens revealed evidence of gap formation in the adhesive interface in all samples.

Analysis of Variance↗

PubMed2004

Biomaterials in periodontal regenerative surgery: effects of cryopreserved bone, commercially available coral, demineralized freeze-dried dentin, and cementum on periodontal ligament fibroblasts and osteoblasts.

The ultimate goal of periodontal therapy is to achieve successful periodontal regeneration. The effects of different biomaterials, allogenic and alloplastic, used in periodontal surgeries to achieve regeneration have been studied in vitro on periodontal ligament (PDL) cells and MC3T3-E1 cells. The materials tested included cryopreserved bone allograft (CBA), coralline hydroxyapatite (CH), demineralized freeze-dried dentin (DFDD), and cementum. CBA and CH revealed an increase in initial PDL cell attachment, whereas CH resulted in an increase in long-term PDL cell attachment. Mineral-like nodule formation was observed significantly higher in DFDD compared to other materials tested for osteoblasts. Based on the results of this in vitro study, we conclude that the materials used are all biocompatible with human PDL cells and osteoblasts, which have pivotal importance in periodontal regeneration.

3T3 Cells↗

PubMedDate not supplied

A protocol system for testing biohazardous materials in an impact biomechanics research facility.

This article presents a protocol system, comprised of a review process and a series of checklists, that was developed for testing cadaveric tissue in an impact biomechanics research facility. The use of cadaveric tissue may expose personnel to bloodborne pathogens including HIV and hepatitis B, which have been shown to remain virulent in a cadaver for several weeks after death. To minimize exposure risks, the protocol system presented emphasizes initial blood screening to keep infectious tissue from entering the laboratory, and adopts universal precautions to prevent exposure by treating all tissue as though it were infected. All lab employees must read, sign, and demonstrate proficiency in the protocol. Well-developed test procedures for the handling of biohazardous materials along with an annual individual protocol review have proven effective for the past 6 years in minimizing exposure risks.

Biomechanical Phenomena↗

PubMed2006

Aluminum sulfate significantly reduces the skin test response to common allergens in sensitized patients.

BACKGROUND: Avoidance of allergens is still recommended as the first and best way to prevent allergic illnesses and their comorbid diseases. Despite a variety of attempts there has been very limited success in the area of environmental control of allergic disease. Our objective was to identify a non-invasive, non-pharmacological method to reduce indoor allergen loads in atopic persons' homes and public environments. We employed a novel in vivo approach to examine the possibility of using aluminum sulfate to control environmental allergens. METHODS: Fifty skin test reactive patients were simultaneously skin tested with conventional test materials and the actions of the protein/glycoprotein modifier, aluminum sulfate. Common allergens, dog, cat, dust mite, Alternaria, and cockroach were used in the study. RESULTS: Skin test reactivity was significantly reduced by the modifier aluminum sulfate. Our studies demonstrate that the effects of histamine were not affected by the presence of aluminum sulfate. In fact, skin test reactivity was reduced independent of whether aluminum sulfate was present in the allergen test material or removed prior to testing, indicating that the allergens had in some way been inactivated. CONCLUSION: Aluminum sulfate was found to reduce the in vivo allergic reaction cascade induced by skin testing with common allergens. The exact mechanism is not clear but appears to involve the alteration of IgE-binding epitopes on the allergen. Our results indicate that it may be possible to diminish the allergenicity of an environment by application of the active agent aluminum sulfate, thus producing environmental control without complete removal of the allergen.

Journal Article↗

PubMed1989

[Problems in disinfection of dental impression materials].

In view of the risk of infection of the dentist and his staff in the dental surgery and dental laboratory and also of the patient with regard to hepatitis B and potentially also of AIDS, interruption of possible chains of infection by means of specific disinfection measures is to be demanded. Whereas appropriate hygiene concepts exist for disinfection of instruments, surfaces of equipment and furniture with regard to selection and application of various methods which may be considered, there are still extensive deficits for the domain of impression materials and their possible decontamination. In this regard, dentists frequently lack information with an adequate scientific basis that is understandable and oriented to practical requirements. Owing to the diversity of materials and their different behavior (cf. Tab. 1), appropriate recommendations can only be made on the basis of extensive studies. We assume that a practically relevant procedure must meet the following requirements: 1) sufficiently high rates of bacterial reduction in accordance with the guidelines of the DGHM, 2) lack of alterations in the dimensions or surfaces of the materials, 3) universal applicability, 4) practicability within a time period which is acceptable for smooth operation of the practice, 5) can be employed without problems for the staff. The object of the report are bacteriological results and materials testing data for the application of various methods of disinfection to selected impression materials. To summarize, it can be stated with regard to the bacteriological results that disinfection of impression materials is possible with fulfillment of the criteria specified above, but that there is a pronounced dependence of the results on the product formulation of the disinfectant and also of the impression material (cf. Fig. 4 and 5). Investigations of the material-related effects of the disinfection measures showed that extrapolation of the findings from one group of materials to another is also not possible in this connection, and that moreover the materials used to produce the model must also be included besides the impression materials used (cf. Fig. 9). Accordingly, statements on the suitability of a disinfection procedure are present admissible at most for the respective combination of materials tested, which makes practical introduction problematical.

Bacteria↗

PubMedDate not supplied

Biocompatibility test procedures for materials evaluation in vitro. II. Objective methods of toxicity assessment.

Methods of assessing the biocompatibility of materials for use in medical devices were evaluated. Ten materials were tested using quantitative, objectively graded in vitro biochemical and functional assays employing four cell lines (CCL 1, 74, 76, and 131) used in previous work and five primary cell types (human lymphocytes, polymorphonuclear leukocytes, and mixed leukocytes, mouse macrophages, and mouse embryo). The biochemical methods (DNA synthesis, protein synthesis, and ATP activity) demonstrated good agreement in toxicity ranking of the materials, regardless of which cell culture was used and, also, the cell cultures responded similarly for each method. Methods that measured functional characteristics of cells (adhesion and phagocytosis) were highly sensitive but had low toxicity ranking agreement and reproducibility. Assays (defined as method and cell culture combinations) using cell lines were more reproducible than assays using primary cell types. Significant differences in sensitivity were noted among the assay systems for particular material types. The in vitro assays were more sensitive to differences in material composition than was a 90-day assay by subcutaneous implantation in rats.

Adenosine Triphosphate↗

PubMed2001

Microleakage of root-end filling materials.

The purpose of this study was to evaluate the microleakage of various root-end filling materials using a fluid filtration system. Sixty extracted human single-rooted teeth were used. The crowns were removed, the canals prepared, and root-end fillings placed. The samples were divided into two control and five experimental groups. The root-end filling materials tested were: amalgam, Intermediate Restorative Material (IRM), a dentin-bonded resin, Super-EBA, and mineral trioxide aggregate. The results showed that amalgam root-end fillings demonstrated significantly more microleakage than Super-EBA, dentin-bonded resin, or mineral trioxide aggregate. There was no significant difference between amalgam and IRM. However IRM was also not significantly different from the other three groups. There were no significant differences between the other three groups.

Aluminum Compounds↗