Evaluation of the bond strengths of 3 endodontic cements via push-out test.

In this study, the push-out method was used to evaluate the bond strengths of 3 types of endodontic cements according to their composite base: methacrylate, epoxy resin, and an experimental copaiba oil resin. The study hypothesis was that the methacrylate-based and experimental cements would have bond strengths equal to or greater than that of the epoxy resin-based cement. Thirty bovine tooth roots, 18 mm long, were divided into 3 groups (n = 10) based on the chosen cement treatment. After treatment, the specimens were sectioned and submitted to a push-out test. Results showed that there was no statistically significant difference (P < 0.05) between the cements used or between the middle and apical thirds of the roots. It could be concluded that the tested cements had satisfactory and similar bond strengths to dentin.

Push-out bond strength of self-adhesive methacrylate resin-based sealers to root dentin.

This study examined the adhesive strength of two self-adhesive methacrylate resin-based sealers (MetaSEAL and RealSeal SE) to root dentin and compared them with RealSeal and AH Plus in properties. A total of 48 extracted human single-rooted teeth were used to prepare the 0.9-mm thick longitudinal tooth slice (each per tooth). Standardized simulated canal spaces of uniform dimensions were prepared in the middle of radicular dentin. After treated with 5.25% sodium hypochlorite (NaOCl) and 17% EDTA, tooth slices were allocated randomly to four groups (n=12) in terms of different sealers used: MetaSEAL, RealSeal SE, RealSeal, and AH plus groups. The simulated canal spaces were obturated with different sealers in each group. There were 10 slabs with 20 simulated canal spaces (n=20) used in each group for push-out testing. The failure modes and the ultrastructures of fractured sealer-dentin interfaces were examined. The remaining 2 slabs in each group underwent partial demineralization for observation of the ultrastructure of resin tags. The results showed that the push-out bond strength was 12.01±4.66 MPa in MetaSEAL group, significantly higher than that in the other three groups (P<0.05). Moreover, no statistically significant differences were noted in the push-out bond strength between RealSeal SE (5.43±3.68 MPa) and AH Plus (7.34±2.83 MPa) groups and between RealSeal SE and RealSeal (2.93±1.76 MPa) groups (P>0.05). Mixed failures were predominant in the fractured sealer-dentin interfaces in MetaSEAL and AH Plus groups, while adhesive failures were frequently seen in RealSeal SE and RealSeal groups. In conclusion, after complete removal of the smear layer, MetaSEAL showed superior bond ability to root dentin. The RealSeal SE is applicable in clinical practice, with its adhesive strength similar to that of AH Plus. The self-adhesive methacrylate resin-based sealer holds promise for use in endodontic treatment.

Determination and validation of an aquatic Maximum Acceptable Concentration-Environmental Quality Standard (MAC-EQS) value for the agricultural fungicide azoxystrobin.

The main goal of the present study was to determine and validate an aquatic Maximum Acceptable Concentration-Environmental Quality Standard (MAC-EQS) value for the agricultural fungicide azoxystrobin (AZX). Assessment factors were applied to short-term toxicity data using the lowest EC50 and after the Species Sensitivity Distribution (SSD) method. Both ways of EQS generation were applied to a freshwater toxicity dataset for AZX based on available data, and to marine toxicity datasets for AZX and Ortiva® (a commercial formulation of AZX) obtained by the present study. A high interspecific variability in AZX sensitivity was observed in all datasets, being the copepoda Eudiaptomus graciloides (LC50,48h = 38 µg L-1) and the gastropod Gibbula umbilicalis (LC50,96h = 13 µg L-1) the most sensitive freshwater and marine species, respectively. MAC-EQS values derived using the lowest EC50 (≤0.38 µg L-1) were more protective than those derived using the SSD method (≤3.2 µg L-1). After comparing the MAC-EQS values estimated in the present study to the smallest AA-EQS available, which protect against the occurrence of prolonged exposure of AZX, the MAC-EQS values derived using the lowest EC50 were considered overprotective and a MAC-EQS of 1.8 µg L-1 was validated and recommended for AZX for the water column. This value was derived from marine toxicity data, which highlights the importance of testing marine organisms. Moreover, Ortiva affects the most sensitive marine species to a greater extent than AZX, and marine species are more sensitive than freshwater species to AZX. A risk characterization ratio higher than one allowed to conclude that AZX might pose a high risk to the aquatic environment. Also, in a wider conclusion, before new pesticides are approved, we suggest to improve the Tier 1 prospective Ecological Risk Assessment by increasing the number of short-term data, and apply the SSD approach, in order to ensure the safety of aquatic organisms.

Influence of filler parameters on the mechanical coherence of dental restorative resin composites.

Next to the presence of (chemical) coupling between filler and resin, filler particle size is important for the mechanical coherence of dental resin composites which are used for posterior restorations. In the range of the current composites a smaller particle size is desirable. The better mechanical coherence for composites with smaller particles found in an in vitro erosive wear test is probably related to the size of food fibres, which are part of the erosive medium. It appears that there is a critical value of the filler particle size (1.3-1.5 microns), under which the food fibres are not able to penetrate in the interparticle space, so the erosive capability of the erosive medium will be reduced.

Sealing ability of new generation adhesive systems in primary teeth: an in vitro study.

PURPOSE: This study evaluated the sealing ability of different types of restorative-adhesive combinations on deciduous molars in vitro. METHODS: Facial and lingual Class V cavities were prepared in 120 primary teeth. They were randomly divided into 8 groups of N= 15, in which different adhesives were used (XE=Xeno III; LP=Adper Prompt L Pop; IB=I Bond; SB=Scotch Bond 1; EP=Etch & Prime 3.0; AS=AdheSE; OB=Optibond Solo plus self-etch primer; CS=Clearfil SE Bond). All cavities were restored with composite Z 250. After thermocycling and immersion in 2% methylene blue, the dye penetration was evaluated under a microscope. RESULTS: In enamel and in cementum: the best seals were obtained with XE and LP, followed by CS, AS, IB, OB, SB, and EP (P=.001). No significant differences were recorded in the microleakage degree between the cementum and the enamel margins (P=.40). CONCLUSIONS: In this in vitro model, Xeno III and Adper Prompt L Pop provided the best seals both at the enamel and the cementum margins of Class V cavities in primary molars.

Correlation between stated and measured concentrations of acrylate and methacrylate allergens in patch-test preparations.

BACKGROUND: Contact allergy to acrylates and methacrylates is not uncommon. The allergy is confirmed by patch-testing patients with commercial patch-test preparations. OBJECTIVE: To investigate acrylate and methacrylate allergens used for patch testing in nine different dermatology departments from Europe, America, Asia, and Australia. METHODS: The acrylate and methacrylate (methyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, ethylene glycol dimethacrylate, and triethylene glycol diacrylate) allergen samples were analyzed with high-performance liquid chromatography to measure the allergen content. RESULTS: Variation in measured versus stated concentrations was seen in these samples. The ratio of measured to stated concentrations ranged from 0.11 to 1.1. Only 22 (63%) of 35 samples were within the arbitrary acceptable limits of 80 to 120% of the stated concentrations. CONCLUSION: The results may have implications for individual diagnosis and prevention and when test results from various centers are compared.

Physicochemical properties of methacrylate resin-based root canal sealers.

INTRODUCTION: This study assessed in vitro the physicochemical properties of 2 methacrylate resin-based sealers (Epiphany SE and Hybrid Root SEAL), comparing the results with a well-established epoxy resin-based sealer (AH Plus). METHODS: Five samples of each material were used for each test (setting time, flow, radiopacity, dimensional change after setting, and solubility) according to American National Standards Institute/American Dental Association (ANSI/ADA) Specification 57. The samples were assigned to 3 groups: I, AH Plus; II, Epiphany SE; and III, Hybrid Root SEAL. The distilled and deionized water used at the solubility test was submitted to atomic absorption spectrometry to observe the presence of Ca2+, K+, Ni2+, and Zn2+ ions. In addition, the surface morphology of the specimens was analyzed by means of scanning electron microscopy (SEM). Statistical analysis was performed by using one-way analysis of variance and Tukey-Kramer test (P < .05). RESULTS: Flow, radiopacity, and solubility of all sealers were in accordance with ANSI/ADA. The setting time of Hybrid Root SEAL did not agree with ANSI/ADA requirements. The dimensional change of all sealers was greater than the values considered acceptable by ANSI/ADA. The spectrometry analysis showed significant Ca(2+) ions release for AH Plus. In SEM analysis, Hybrid Root SEAL presented spherical monomers with inferior size than AH Plus and Epiphany SE. CONCLUSIONS: It might be concluded that physicochemical properties of the tested sealers conformed to ANSI/ADA (2000) standardization, except for the setting time of Hybrid Root SEAL and the dimensional change of all sealers, which did not fulfill the ANSI/ADA requirements.

[Detection of inferior products in arthroplasty and implementation of findings: a retrospective analysis of the Boneloc incident]. / Erfassung von minderwertigen Produkten in der Endoprothetik und Umsetzung der Erkenntnisse: eine retrospektive Analyse am Beispiel des Boneloc-Knochenzements.

AIM: By a retrospective assessment of the Boneloc incident, a bone cement which had an inferior outcome in terms of survival rate, the value of published datasets for the detection of inferior outcomes was evaluated. METHOD: A structured literature review of English and German peer reviewed journals was conducted. The articles were assessed with respect to revision rate and statements about the product. In a standardised methodology, adjusted for number of cases and follow-up period, the revision rate was calculated. Main goal was to assess the agreement of published information from different datasets. RESULTS: In the first 4 years after Boneloc had been brought on the market exclusively experimental studies were published, most of which were in favour of the product. In 1995, clinical studies, migration analyses and register-based articles were published. Most of them reported about inferior results, in the same year Boneloc was taken from the market worldwide. Sample-based clinical follow-up studies were not able to contribute to the decision-making process, they were published with a delay of several years and were underpowered from a statistical point of view. All of them published critical statements--after the product had no longer been available on the market for many years. The average revision rate in sample-based studies exceeded the reference value in the Norwegian Arthroplasty Register 7.35-fold. When the inferior results with Boneloc were published, the product had already disappeared from the national markets in Scandinavian countries' operating registers. The central position of orthopaedic scientific societies in the entire outcome monitoring system in these countries seems to be a key factor for success and rapid reaction to identified problems. CONCLUSION: Arthroplasty registers and migration analyses have the highest value for the rapid and reliable detection of inferior outcomes in comparative analyses of published articles. Experimental studies did not agree with the performance of the product in a retrospective view, the data cannot be transferred from the estimation of future clinical outcome like survival rates. The involvement of scientific societies in the assessment and dissemination of the results is a key factor to realise potential benefit by an advanced quality monitoring project like arthroplasty registers.

Bond strength of adhesive systems to human tooth enamel.

The purpose of this study was to evaluate in vitro three adhesive systems: a total etching single-component system (G1 Prime & Bond 2.1), a self-etching primer (G2 Clearfil SE Bond), and a self-etching adhesive (G3 One Up Bond F), through shear bond strength to enamel of human teeth, evaluating the type of fracture through stereomicroscopy, following the ISO guidance on adhesive testing. Thirty sound premolars were bisected mesiodistally and the buccal and lingual surfaces were embedded in acrylic resin, polished up to 600-grit sandpapers, and randomly assigned to three experimental groups (n = 20). Composite resin cylinders were added to the tested surfaces. The specimens were kept in distilled water (37 degrees C/24 h), thermocycled for 500 cycles (5 degrees C-55 degrees C) and submitted to shear testing at a crosshead speed of 0.5 mm/min. The type of fracture was analyzed under stereomicroscopy and the data were submitted to Anova, Tukey and Chi-squared (5%) statistical analyses. The mean adhesive strengths were G1: 18.13 +/- 6.49 MPa, (55% of resin cohesive fractures); G2: 17.12 +/- 5.80 MPa (90% of adhesive fractures); and G3: 10.47 +/- 3.14 MPa (85% of adhesive fractures). In terms of bond strength, there were no significant differences between G1 and G2, and G3 was significantly different from the other groups. G1 presented a different type of fracture from that of G2 and G3. In conclusion, although the total etching and self-etching systems presented similar shear bond strength values, the types of fracture presented by them were different, which can have clinical implications.

[Studies of the dental methacrylic resins. (V) Effects of molecular weight and temperature on the plasticity (author's transl)].

The plasticity, the douing time, and the working time, of the mixture of powder-liquid type methacrylic resin were measured under the various circumstances of the elapsed time and the certain temperature. Six polymethyl methacrylates, whose molecular weight was prepared by mean of gamma-ray irradiation, were used as the polymer of resin, again methyl methacrylate being used as the monomer of resin. The results obtained are as follows: (1) The plasticity is reduced with the increase of the molecular weight of the polymer. (2) The plasticity, generally, is reduced with the time elapsed, but its values appear at 10 min. and 5 min. elapsed at 16 degrees C and 23 degrees C respectively. (3) The plasticities of the mixtures of polymers with 6 X 10(4), 8 X 10(4), 20 X 10(4) and 34 X 10(4) molecular weights are increased with the increase of temperature. The plasticities of the mixtures of polymers with 60 X 10(4) and 74 X 10(4) molecular weights at 0 min. time elapsed, indicate their maximum value at 30 degrees C. At 5 min. time elapsed plasticities of all mixtures indicate their maximum value at 23 degrees C. Over 5 min. time elapsed, however, the plasticity is reduced with the increase of temperature. (4) The doughing time and the working time are reduced with the increase of molecular weight of the polymer and the temperature.

[Mechanical and dimensional properties of thermosetting resins for crown (author's transl)].

The various mechanical and dimensional properties of seven thermosetting methacrylic resins for crown and one heat-curing methacrylic resin as the control were investigated. The obtained results were as follows. 1. The water sorption, namely amount of sorption water and linear expansion by water sorption of hydrophobic poly-bis-MEPP resins were 50 to 70% of that of the control. But hydrophilic poly-EDMA resins indicated the water sorption about 1 to 1.5 times as much as the control. And a poly-UDMA resin was also hydrophilic as poly-EDMA resins, indicated about 1.3 times as much as the control. 2. The properties of poly-bis-MEPP resins were more excellent than that of poly-EDMA resins especially in the wet condition, at least were equal. 3. A poly-UDMA resin contained so-called organic composite fillers, indicated more excellent properties than other resins on hardness, abrasion resistance, linear coefficient of thermal expansion, compressive strength and bending strength in the dry condition. But, in the wet condition, some of these properties of a poly-UDMA resin were approximately equal to those of other resins.

[Application of 4-META on adhesive opaque resin. (Part 2) Improvement of adhesive stability (author's transl)].

We had reported 4-META adhesive opaque resin for a metal casting etched with HC1. The bonding strength was as excellent as 260 kg/cm2 after 300 times thermal cycles between 4 degrees C and 60 degrees C but it decreased to 70 kg/cm2 when immersed in water at 37 degrees C for 30 weeks. It was required to improve the stability of bonding against water penetration into the adhesive junction before the clinical application. Preparation of the passive state on the metal casting adhesive stability between this film and the opaque resin were studied in this paper. When the metal casting was dipped in conc. HNO3 for fifteen minutes, adhesive strength was 260 kg/cm2 even after a 30 weeks immersion in water at 37 degrees C or the 10 weeks at 80 degrees C. It could be concluded that the adhesive opaque resin possesses enough adhesive strength and the stability for oral application.

Gas chromatographic and mass spectrometric purity analysis of acrylates and methacrylates used as patch test substances.

BACKGROUND: To make a correct diagnosis of allergic contact dermatitis, patch testing needs to be performed, and the patch test substances need to be pure. OBJECTIVE: We wanted to study how pure commercial (meth)acrylic patch test substances are. METHODS: The purity of (meth)acrylic patch test substances (diacrylates, dimethacrylates, and triacrylates) dissolved in acetone was determined by gas chromatography. The impurities were identified by mass spectrometry in both electron impact and chemical ionization mode. RESULTS: The analyzed dimethacrylates were very pure (97% to 99%). The purity of the three studied diacrylates were 81% to 91%, but tripropyleneglycol diacrylate (81% pure) contained as much as 13% of tripropyleneglycol monoacrylate. The purities of the triacrylates were 82% to 86%. All diacrylates and triacrylates contained 1% to 13% of the corresponding hydroxyacrylates. CONCLUSION: The impurities may result in false interpretation of the patch test results, and accordingly in wrong diagnosis. If the patch test substance is impure, at least, the chemical impurities that can be detected by gas chromatography should be measured and reported in a certificate of analysis, preferably from each batch.

Hemocompatibility on graft copolymers composed of poly(2-methacryloyloxyethyl phosphorylcholine) side chain and poly(n-butyl methacrylate) backbone.

To improve the hemocompatibility on hydrophobic biomedical materials by a simple coating technique, graft copolymers composed of a hydrophilic side chain with phospholipid polar groups and a hydrophobic backbone were synthesized. The hydrophilic chain had phospholipid polar groups, poly[2-methacryloyloxyethyl phosphorylcholine (MPC)], and the hydrophobic backbone was poly[n-butyl methacrylate (BMA)]. Because the graft copolymers obtained could dissolve in ethanol, they could be used as a coating material. When the poly(MPC-graft-BMA) was coated onto a poly(BMA) membrane, the composition of the MPC units on the surface was maintained in the bulk graft copolymer even after immersion in water. Protein adsorption on the membrane coated with the graft copolymer from human plasma detected by a gold-colloid labeled immunoassay was drastically decreased compared with that on glass and the original membrane. Moreover, blood cell adhesion, activation, and aggregation on the membrane after contact with human citrated whole blood were suppressed by the coating of the graft copolymer. These results clearly show that the poly(MPC-graft-BMA) is a suitable material for improving hemocompatibility on the biomedical devices because of its protein adsorption and cell adhesion resistant properties.

[Fissure sealing with Evicrol in animal experiments]. / Fissurenversiegelung mit Evicrol im Tierexperiment.

The preventive effect of fissure sealing with the composite material Evicrol was tested in a programmed standardized caries experiment on Wistar rats. The results obtained indicate that Evicrol is not suited for fissure sealing.

Epoxy putty for free-form external skeletal fixators.

OBJECTIVE: To evaluate the suitability of epoxy putty for use as a connecting beam material in a free-form external skeletal fixator. DESIGN: Mechanical evaluation of beams and the pin-material interface of commonly used methacrylates and the proposed epoxy putty. PROCEDURE: The apparent modulus, bending strength, and toughness of 10 beams of three methacrylates (Technovit, APEF System, Bone Cement) and three epoxy putties (Oatey Epoxy Putty, All-Metals PowerPoxy, and Plumber's PowerPoxy) were determined in three-point bending. The shear strength of smooth and roughened-shaft pins embedded in the three methacrylates and the Oatey Epoxy Putty was determined by pull-out testing. RESULTS: The epoxy putties had similar strength, greater apparent modulus, and reduced toughness when compared with the methacrylates. The shear strength of the smooth pin interface with the Oatey Epoxy putty was greater than that with the methacrylates. The interface with roughened pins was much stronger than that with smooth pins for all materials tested. CLINICAL RELEVANCE: Epoxy putty is a suitable material for free-form external fixators. It is easy to handle, inexpensive, and has suitable setting times and mechanical properties.

Raman and IR studies on adsorption behavior of adhesive monomers in a metal primer for Au, Ag, Cu, and Cr surfaces.

6-[N-(4-vinylbenzyl)propylamino]-1,3,5-triazine-2,4-dithione (VBATDT) and 10-methacryloyloxydecyl dihydrogen phosphate (M10P) are functional monomers used for the surface treatment of dental alloys. The aim of our study was to clarify the role of a commercial metal primer containing both the monomers in adhesion between resin and various dental metals on a molecular level. We used surface-enhanced Raman scattering (SERS) and infrared reflection absorption (IRA) spectroscopy. An SERS measurement was performed with a 647 nm laser line for a mixture of aqueous Au colloid and the primer. IRA spectra were taken for cast films of the primer on Au, Ag, Cu, and Cr surfaces as a function of rinse time, and for self-assembled monolayer (SAM) films from dilute mixed solution of VBATDT and M10P. These spectra indicate that VBATDT in the primer is mainly chemisorbed on Au, Ag, and Cu surfaces with respect to thickness, whereas only M10P is adsorbed on Cr. We also examined the tensile bond strengths between resin and Au, Ag, Cu, and Cr plates treated by VBATDT, with and without M10P, and found that VBATDT effectively promotes the bond strength between resin and the metals except for Cr, whereas M10P is effective only for Cr. These adhesion characteristics are consistent with the chemisorbed species on each metal surface as shown in the spectroscopic evidence.