Oriented polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) films by Langmuir-Blodgett deposition: a synchrotron X-ray diffraction study.

Langmuir-Blodgett films of polyvinylidene fluoride trifluoroethylene - P(VDF-TrFE)-copolymers possess substantially improved electrocaloric and pyroelectric properties, when compared with conventionally spin-cast films. In order to rationalize this, we prepared single-layered films of P(VDF-TrFE) (70 : 30) using both deposition techniques. Grazing incidence wide-angle X-ray scattering (GIWAXS), reveals that Langmuir-Blodgett deposited films have a higher concentration of the ferroelectric ß-phase crystals, and that these films are highly oriented with respect to the substrate. Based on these observations, we suggest alternative means of deposition, which may substantially enhance the electrocaloric effect in P(VDF-TrFE) films. This development has significant implications for the potential use of P(VDF-TrFE) in solid-state refrigeration.

Penetration pattern of rhodamine dyes into enamel and dentin: confocal laser microscopy observation.

Enamel and dentin are susceptible to extrinsic and intrinsic stains. The purposes of this study were to determine the penetration pattern of Rhodamine B and dextran-conjugated Rhodamine B into the enamel and dentin as observed by confocal laser microscopy and to relate it to the penetration pattern of hydrogen peroxide commonly used as an active ingredient in tooth-whitening agents and high-molecular-weight staining molecules. Eighteen recently extracted human maxillary anterior teeth were used. Teeth were cleaned and painted with nail varnish except for the crown area above the cemento-enamel junction (CEJ). The painted teeth were then immersed in Rhodamine B and dextran-conjugated Rhodamine B (70 000 MW) for 4, 7, 10 and 15 days. Teeth were sliced to 3 mm thickness in transverse plane and mounted on a glass slide just prior to observation with confocal laser microscopy. Rhodamine B and dextran-conjugated Rhodamine B readily penetrated into the enamel and dentin when exposed for 4 and 7 days, respectively. Rhodamine B penetrated along the interprismatic spaces of the enamel into the dentin. The penetration was accentuated in sections with existing crack lines in the enamel. Rhodamine B was readily absorbed into the dentinal tubules at the dentino-enamel junction and continued to penetrate through the dentin via the dentinal tubules into the pre-dentin. Within the limitations of this study, it is concluded that Rhodamine B and dextran-conjugated Rhodamine B when applied to the external surface of the tooth readily penetrate into the enamel and dentin via the interprismatic spaces in the enamel and dentinal tubules in the dentin, suggesting that stain molecules and bleaching agents possibly exhibit similar penetration pathways.

Preliminary evaluation of a novel polymer nanocomposite as a root-end filling material.

AIM: To evaluate two nanoparticle-enhanced polymer root-end filling materials (NERP1 and NERP2) on the initial apical seal as compared to a polymer-based commercial compomer. METHODOLOGY: One hundred and forty extracted roots with completely formed apices were resected 3 mm from the apex. Cavities were then prepared in the apical openings of the resected root ends using an ultrasonic handpiece to a depth of 3 mm. The roots were then randomly divided into five groups to receive one of five root-end filling materials. Roots in groups 1 and 2 received NERP1 and NERP2, whilst those in groups 3 and 4 received identical polymers as groups 1 and 2 but without nanoparticle addition (RP1 and RP2, respectively). The root-end cavities for the fifth group were filled with commercially available root-end filling compomer. Roots were mounted in a dual-chamber leakage apparatus and inoculated coronally with Enterococcus faecalis. Turbidity of the apical broth was assessed daily for 4 weeks as a sign of initial leakage. The results were statistically analysed using odds ratio and Fisher's chi-square analysis. RESULTS: Nanoparticle-enhanced root-end filling polymer 1 displayed significantly fewer leaked samples compared to all other tested groups as early as 5 days, whilst NERP2 was not significantly different compared to other groups. Odds ratio analysis revealed leakage of the commercial compomer was 12 times more likely than NERP1. CONCLUSION: Nanoparticle-enhanced root-end filling polymer 1 can reduce apical microleakage significantly under laboratory conditions.

The accuracy of optical scanning: influence of convergence and die preparation.

The purpose of this study was to determine the reliability of the data acquisition and modeling process of laser and white light scanners by evaluating the reproducibility of digitized simulated crowns with different convergences. A secondary purpose was to analyze the influence of die preparation by testing this hypothesis with a set of dies without ditching compared with a set with well-defined margins. Ditching or trimming the die defines the position of the margin and acts as a guide to gingival contour when the restoration is being waxed. Two light scanners (a white light optical scanner [Steinbichler Gmbh, Neubeuern, Germany] and red laser light scanner [TurboDent System, Taichung, Taiwan]) were evaluated. Two sets of simulated crowns were fabricated as cone frustrum models with a total occlusal convergence (TOC) of 0°, 5°, 10°, 15°, 20°, and 25° and a 9-mm base and 3-mm height using a precision milling machine and computer-aided design/computer-aided manufacturing (CAD/CAM) technique. One set of the dies was ditched immediately below the finish line to enhance marginal definition. Each die was optically digitized five times directly with the two different measuring systems. The area of each triangle in the scan that is occlusal to the margin line was calculated and summed to produce the final surface area measurement provided. The digitizing error was compared with the computed surface area of the original master die sets and compared with a paired t-test (df=4; 95% CI). There was no difference in accuracy of the untrimmed dies between the two systems evaluated. We also did not find any difference in the 0° (p=0.12) and 5° degree (p=0.21) groups among the ditched dies. However, when the TOC exceeded 5°, there was a significant difference between the two groups, with the laser groups having a smaller error percentage. Three-dimensional light scanning was not affected by the convergence angle except in the 0°-5° range. Trimming the dies greatly affected the accuracy of scanning.

The effects of repeated heat-pressing on properties of pressable glass-ceramics.

The aim of this study was to evaluate the properties of four heat-pressed glass-ceramic materials after repeated heat-pressing. Two commercially available heat-pressed glass-ceramic systems [Optimal pressable glass-ceramics (OPC and 3G) and Empress pressable glass-ceramics (Empress and Empress2)] were selected. Disc samples (14 mm x 1.4 mm) of each tested material were heat-pressed and used as controls. Sprue and button parts of the pressed groups were retrieved and used for repeated heat-pressing to construct specimens of re-pressed group. All the heat-pressed casting procedures were performed according to the manufacturers' instructions. A biaxial flexural strength (BFS) test (ISO 6872) was performed to determine the strength of pressed and re-pressed glass-ceramic disc specimens (n = 10) at a crosshead speed of 0.5 mm min(-1). Ions eluted from etching procedure were collected and examined using inductively coupled plasma mass spectrometer. Surface characteristics were examined with electron probe microanalysis, X-ray diffraction and secondary electron imaging (SEI). The data were analysed statistically (ANOVA + Tukey's HSD post hoc test, P < 0.05). The BFS values obtained ranged from 123.5 +/- 18.5 to 365.9 +/- 35.5 MPa. The re-pressed Empress2 group had a statistically significant higher BFS mean than the pressed control group (P < 0.05). The SEI micrographs of the lithium disilicate-reinforced glass-ceramic material (Empress2) showed a densely packed, interlocking microstructure and an increase in size with preferred orientation of the lithium disilicate crystals after repeated heat-pressing. Repeated heat-pressing treatment produced a statistically significant increase in the flexural strength of Empress2 glass-ceramic material.

Changes in resin-infiltrated dentin stiffness after water storage.

Plasticization of polymers by water sorption lowers their mechanical properties in a manner that is predictable by the polarity of their component resins. This study tested the hypothesis that when adhesive resins were used to create resin-infiltrated dentin, the reductions in their flexural moduli after water storage would be lowered proportional to their hydrophilic characteristics. Three increasingly hydrophilic resin blends were used to fabricate polymer beams and macro-hybrid layer models of resin-infiltrated dentin for testing with a miniature three-point flexure device, before and after 1-4 weeks of water storage. Flexural modulus reductions in macro-hybrid layers were related to, and more extensive than, reductions in the corresponding polymer beams. Macro-hybrid layers that were more hydrophilic exhibited higher percent reductions in flexural modulus, with the rate of reduction proportional to the Hoy's solubility parameters for total intermolecular attraction forces (delta(t)) and polar forces (delta(p)) of the macro-hybrid layers.

Mesenchymal stem cell-based repair of articular cartilage with polyglycolic acid-hydroxyapatite biphasic scaffold.

This study investigates the capacity of a composite scaffold composed of polyglycolic acid-hydroxyapatite (PGA-HA) and autologous mesenchymal stem cells (MSCs) to promote repair of osteochondral defects. MSCs from culture-expanded rabbits were seeded onto a PGA and HA scaffold. After a 72-hour co-culture period, the cell-adhered PGA and HA were joined together, forming an MSCs-PGA-HA composite. Full-thickness cartilage defects in the intercondylar fossa of the femur were then implanted with the MSC-PGA-HA composite, the PGA-HA scaffold only, or they were left empty (n=20). Animals were sacrificed 16 or 32 weeks after surgery and the gross appearance of the defects was evaluated. The specimens were examined histologically for morphologic features, and stained immunohistochemically for type 2 collagen. Specimens of the MSCs-PGA-HA composite implantation group demonstrated hyaline cartilage and a complete subchondral bone formation. At 16 weeks post-implantation, significant integration of the newly formed tissue with surrounding normal cartilage and subchondral bone was observed when compared to the two control groups. At 32 weeks, no sign of progressive degeneration of the newly formed tissue was found. A significant difference in histological grading score was found compared with the control groups. The novel MSCs-seeded, PGA-HA biphasic graft facilitated both articular cartilage and subchondral bone regeneration in an animal model and might serve as a new approach for clinical applications.

Effect of pre-processing surface treatments of acrylic teeth on bonding to the denture base.

The aim of this study was to examine the bond strength between acrylic teeth after various surface treatments and processing with either a heat- or microwave-polymerized denture base material. Specimens were prepared and tested according to the methods described in American National Standard/American Dental Association Specification No.15 (Synthetic Polymer Teeth) using a special assembly. Three brands of acrylic teeth were used with the following treatments: control (no treatment), grinding and grinding plus sandblasting. Treatment groups were further divided into two denture base processing subgroups: heat-polymerized and microwave-polymerized methods. Denture base processing to the acrylic teeth was performed according to the manufacturer's recommendations. Bond strength test was performed using a universal testing machine with five specimens and each specimen is composed of six anterior teeth per experimental group. Data were analysed using a three-way anova and the Scheffe'F-test post hoc pair wise comparison at the 95% significance level. The mean bond strength values ranged from 33.1 +/- 4.1 to 51.6 +/- 2.5 MPa. The bond strength values of sandblasted surfaces were significantly higher than those of the ground surface and the control (P < 0.05). Combined (acrylic tooth and denture base resin) cohesive failures were disclosed in all tested samples. Acrylic tooth surface pre-processed surface treatment with grinding plus sandblasting and processed with a heat-polymerized denture base provided the greatest bond strength between acrylic tooth and denture base.

Surface mechanical properties, corrosion resistance, and cytocompatibility of nitrogen plasma-implanted nickel-titanium alloys: a comparative study with commonly used medical grade materials.

Stainless steel and titanium alloys are the most common metallic orthopedic materials. Recently, nickel-titanium (NiTi) shape memory alloys have attracted much attention due to their shape memory effect and super-elasticity. However, this alloy consists of equal amounts of nickel and titanium, and nickel is a well known sensitizer to cause allergy or other deleterious effects in living tissues. Nickel ion leaching is correspondingly worse if the surface corrosion resistance deteriorates. We have therefore modified the NiTi surface by nitrogen plasma immersion ion implantation (PIII). The surface chemistry and corrosion resistance of the implanted samples were studied and compared with those of the untreated NiTi alloys, stainless steel, and Ti-6Al-4V alloy serving as controls. Immersion tests were carried out to investigate the extent of nickel leaching under simulated human body conditions and cytocompatibility tests were conducted using enhanced green fluorescent protein mice osteoblasts. The X-ray photoelectron spectroscopy results reveal that a thin titanium nitride (TiN) layer with higher hardness is formed on the surface after nitrogen PIII. The corrosion resistance of the implanted sample is also superior to that of the untreated NiTi and stainless steel and comparable to that of titanium alloy. The release of nickel ions is significantly reduced compared with the untreated NiTi. The sample with surface TiN exhibits the highest amount of cell proliferation whereas stainless steel fares the worst. Compared with coatings, the plasma-implanted structure does not delaminate as easily and nitrogen PIII is a viable way to improve the properties of NiTi orthopedic implants.

Investigation and diagnosis of an immediate allergy to amide local anaesthetic in a paediatric dental patient.

Local anaesthetics remain the most common prescription medication utilized in dental practise. Adverse reactions following administration of local anaesthetic are somewhat common and are frequently reported as 'allergies'. However, of these events, it is estimated that only 1% are confirmed allergies to the local anaesthetic. This case report presents the process of referral for investigation and testing to confirm an amide local anaesthetic allergy in a paediatric patient. Testing for a safe alternative was also completed to identify local anaesthetic agents also of the amide variety that could be utilized safely on this individual. Following skin testing of alternative agents, intraoral challenges were completed. Finally, restorative dental treatment was provided safely for the patient with the use of an alternative amide local anaesthetic on a number of occasions with no further adverse outcomes.

Local anesthetics can interact electrostatically with membrane proteins.

The fluorescent probe 1-anilinonaphthalene 8-sulfonate was used to examine the binding of spin-labeled local anesthetics to lipid model systems, to the membranes of human red blood cells, and rabbit sarcoplasmic reticulum. 1-Anilinonaphthalene 8-sulfonate exhibits two distinct fluorescent lifetimes when bound to these biological membranes. The shorter lifetime represents the probe associated with the purely lipid region while the longer lifetime is associated with the protein region. The spin-labeled local anesthetic quenches the fluorescence of both of these components as indicated by the decrease in the lifetimes. Since nitroxide free radicals are known to quench fluorophores upon 'contract', the results reflect the relative interaction of local anesthetics with membrane lipids and proteins. The evidence is consistent with the concept of multiple binding sites for local anesthetics in membranes. Local anesthetics, once intercalated into the bilayer, may diffuse laterally and interact with membrane components, lipid as well as proteins. In biological membranes, however, positively charged local anesthetics are better able to quench 1-anilinonaphthalene 8-sulfonate in protein regions, suggesting that the interaction between local anesthetics and membrane proteins can be electrostatic in nature.

Carbon plasma immersion ion implantation of nickel-titanium shape memory alloys.

Nickel-titanium (NiTi) shape memory alloys possess super-elasticity in addition to the well-known shape memory effect and are potentially suitable for orthopedic implants. However, a critical concern is the release of harmful Ni ions from the implants into the living tissues. We propose to enhance the corrosion resistance and other surface and biological properties of NiTi using carbon plasma immersion ion implantation and deposition (PIII&D). Our corrosion and simulated body fluid tests indicate that either an ion-mixed amorphous carbon coating fabricated by PIII&D or direct carbon PIII can drastically improve the corrosion resistance and block the out-diffusion of Ni from the materials. Our tribological tests show that the treated surfaces are mechanically more superior and cytotoxicity tests reveal that both sets of plasma-treated samples favor adhesion and proliferation of osteoblasts.

Corrosion resistance, surface mechanical properties, and cytocompatibility of plasma immersion ion implantation-treated nickel-titanium shape memory alloys.

Nickel-titanium shape memory alloys are promising materials in orthopedic applications because of their unique properties. However, for prolonged use in a human body, deterioration of the corrosion resistance of the materials becomes a critical issue because of the increasing possibility of deleterious ions released from the substrate to living tissues. We have investigated the use of nitrogen, acetylene, and oxygen plasma immersion ion implantation (PIII) to improve the corrosion resistance and mechanical properties of the materials. Our results reveal that the corrosion resistance and mechanical properties such as hardness and elastic modulus are significantly enhanced after surface treatment. The release of nickel is drastically reduced as compared with the untreated control. In addition, our in vitro tests show that the plasma-treated surfaces are well tolerated by osteoblasts. Among the three types of samples, the best biological effects are observed on the nitrogen PIII samples.

Investigation of nickel suppression and cytocompatibility of surface-treated nickel-titanium shape memory alloys by using plasma immersion ion implantation.

Nickel-titanium (NiTi) shape memory alloys are increasingly being used in orthopedic applications. However, there is a concern that Ni is harmful to the human body. We have recently investigated the use of nitrogen, or oxygen plasma immersion ion implantation to mitigate this deleterious effect. Our results reveal that the near-surface Ni concentration in all the treated samples is significantly suppressed. In addition, our in vitro tests show that the plasma-treated surfaces are cytologically compatible allowing the attachment and proliferation of osteoblasts. Among the two types of samples, the best biological effects are found on the samples with nitrogen implantation.

Specific binding proteins for human chorionic gonadotrophin in a patient with trophoblastic disease.

Human chorionic gonadotrophin (hCG) is present in high concentration in patients with trophoblastic disease. The hCG concentration parallels tumor activity. The first known case of an endogenous binder for hCG in the serum of a patient with trophoblastic disease is reported. The patient's hCG concentration was not detectable when analyzed by a radioimmunoassay using a double antibody method; however, it was positive by a radioimmunoassay using polyethylene glycol precipitation. A high serum blank was also observed in this patient. This led the authors to suspect the presence of an endogenous binder for hCG. Scatchard analysis of the patient's serum revealed a high affinity binder with Ka = 1 x 10(10) M(-1), concentration of binding site = 2 x 10(-11) M. This investigation strongly suggested a specific binder(s) for hCG in the serum of this patient.

Composite resin compatibility and bond longevity of a dentin bonding agent.

The shear strength of a commercial dentin bonding agent was studied using human dentin in vitro. The agent was tested for compatibility with three proprietary composite resins. In addition, some samples were subjected to prolonged water immersion and thermocycling to determine effects on bond strength. There was no statistically significant difference in shear strengths when the three composite resins were used. In addition, there was no difference in shear strengths among those samples thermocycled or immersed for up to one year. The implications of this study are that the dentin bonding agent may be used with several composite resins with no significant difference in bond strengths, and that the bond seems stable when subjected to immersion or simulated intra-oral thermal stresses.

In vitro evaluation of a fluoride-releasing orthodontic resin.

Decalcification around brackets is sometimes observed following orthodontic treatment. Fluoride-releasing orthodontic adhesives have been developed and used for reduction of the frequency and severity of decalcification. This study evaluated a light-activated, fluoride-releasing resin composite adhesive, FluorEver OBA. Our findings indicate that FluorEver OBA released small concentrations of fluoride ions over time. However, the adhesive had significantly lower tensile bond strengths than a conventional composite cement. Microhardness testing indicated that the resin underneath metal orthodontic brackets was not thoroughly polymerized, which may have contributed to cohesive failures of the resin composite. Despite its lower tensile bond strength, FluorEver OBA may be indicated for cases where decalcification is expected.

Hydroxyapatite and their use as coatings in dental implants: a review.

At present, no standard manufacturing guideline exists for depositing hydroxyapatite (HA) on implant surfaces. Although animal and in vitro studies have reported on the benefits of using HA-coated implants as well as the risks of dissolution, these short-term studies did not demonstrate that the dissolution of the HA coating leads to a loss of implants. In addition, many in vivo and clinical studies did not include the chemical and structural characterization of the coatings, and thus comparisons between studies are difficult. In the clinics, the recommendation is that HA-coated screw implants be used for the anterior maxilla and posterior mandible where the bone depth exceeds 10 mm and when the cortical layer is thinner and spongiosia is less dense. In the posterior maxilla or when the cortical layer is very thin with low density, the use of HA-coated cylindrical implants is recommended. However, there are concerns for using HA-coated implants. The clinician needs to take into consideration the enhanced bacterial susceptibility of HA coatings compared with titanium implants. In addition, the clinician needs to consider the possible failure of HA coatings as a result of coating-substrate interfacial fracture. Finally, besides the surgical skills, it is also important that the clinical investigators be well versed with the materials characterization needed for HA-coated implants, the problems associated with the current HA coatings, and the indications for use. In addition, the correlation between well characterized coatings and their effect on bone formation rate and long-term implant success, coating-implant interfacial strength, and alternative superior coating process need to be investigated further.

Clinical features of 46 eyes with calcified hydrogel intraocular lenses.

PURPOSE: To clarify the clinical features of delayed calcification of hydrogel intraocular lenses (IOLs) based on observation of a large case series. SETTING: Ophthalmology department of 2 university teaching hospitals, Hong Kong, China. METHODS: The first 44 patients with a known diagnosis of calcified IOL were recruited. Medical and ophthalmic histories were obtained. Surgical details, surgical complications, and visual acuity before and after IOL implantation were also retrieved. Patients then had a visual acuity test, a slitlamp examination of the features of the IOL calcification, and a fundus examination for clarity of view. RESULTS: Forty-six eyes of 44 patients had IOL calcification. All had a Hydroview IOL. The onset was from 4 to 26 months after surgery. Ninety-three percent of eyes had generalized IOL calcification, and 96% had forceps marks on the IOL. Mean visual acuity deteriorated from 0.4 at 3 months to 0.13 at 19 months. Visual loss was more severe in patients with diabetes mellitus or ischemic heart disease and in those in which the IOL calcified earlier after implantation. CONCLUSION: All cases of IOL calcification were delayed in onset. The presence of forceps marks may provide a clue to the pathogenesis. Bilateral but asymmetric involvement in 2 patients suggests that the IOL was involved in the pathogenesis. Affected patients lost an average of 2.8 Snellen lines of visual acuity. Some eyes progressed more rapidly; however, the modulating factors remain unknown.

Microleakage of indirect composite inlays.

The purpose of this in vitro study was to evaluate the microleakage of indirect composite inlays and to compare leakage of inlays with directly placed composite restorations. Standardized MOD preparations were cut in 50 extracted human molars. One gingival margin was placed in enamel above the CEJ, and the other was placed in dentin below the CEJ. Two groups of teeth were directly filled with composites (P-30 and Heliomolar) after being etched, and dentin bonding agents were applied. Two groups of teeth were restored with composite inlays that were fabricated on stone dies. The inlays were made and luted with the same two composites. The last group of teeth was restored with Heliomolar inlays luted with Dual cement. The specimens were thermocycled 300 times between 5 and 50 degrees C. Microleakage was evaluated by use of the silver-nitrate staining technique. The depth of leakage was measured microscopically after the teeth were sectioned. Both direct restorations and inlays showed substantial leakage at gingival-dentin margins; however, there was only superficial leakage at enamel margins. P-30 inlays and Heliomolar inlays cemented with Dual leaked less than direct restorations at the gingival-dentin margins. There was no difference in leakage of enamel margins of inlays and direct restorations, except that direct Heliomolar restorations leaked more than the others. There was no difference in leakage between Heliomolar restorations luted with light-cured or dual-cured cement.