Evaluation of selected properties of a new root repair cement containing surface pre-reacted glass ionomer fillers.

OBJECTIVE: This study evaluated selected properties of a prototype root repair cement containing surface pre-reacted glass ionomer fillers (S-PRG) in comparison to mineral trioxide aggregate (MTA) and intermediate restorative material (IRM). MATERIALS AND METHODS: The antibacterial effect of S-PRG, MTA, and IRM cements was tested against Porphyromonas gingivalis and Enterococcus faecalis after 1 and 3 days of aging of the cements. The set cements were immersed in distilled water for 4 h to 28 days, and ion-releasing ability was evaluated. Initial and final setting times of all cements were evaluated using Gilmore needles. The push-out bond strength between radicular dentin and all cements was tested at different levels of the roots. RESULTS: S-PRG and IRM cements, but not MTA cement, demonstrated significant antibacterial effect against P. gingivalis. All types of cements exhibited significant antibacterial effect against E. faecalis without being able to eliminate the bacterium. S-PRG cement provided continuous release of fluoride, strontium, boron, sodium, aluminum, and zinc throughout all tested time points. Both initial and final setting times were significantly shorter for S-PRG and IRM cements in comparison to MTA. The push-out bond strength was significantly lower for S-PRG cement in comparison to MTA and IRM at coronal and middle levels of the roots. CONCLUSIONS: S-PRG cement demonstrated significant antibacterial effects against endodontic pathogens, multiple ion-releasing ability, relatively short setting time, and low bonding strength. CLINICAL RELEVANCE: S-PRG cement can be used as a one-visit root repair material with promising antibacterial properties and ion-releasing capacity.

Effect of random/aligned nylon-6/MWCNT fibers on dental resin composite reinforcement.

The aims of this study were (1) to synthesize and characterize random and aligned nanocomposite fibers of multi-walled carbon nanotubes (MWCNT)/nylon-6 and (2) to determine their reinforcing effects on the flexural strength of a dental resin composite. Nylon-6 was dissolved in hexafluoropropanol (10 wt%), followed by the addition of MWCNT (hereafter referred to as nanotubes) at two distinct concentrations (i.e., 0.5 or 1.5 wt%). Neat nylon-6 fibers (without nanotubes) were also prepared. The solutions were electrospun using parameters under low- (120 rpm) or high-speed (6000 rpm) mandrel rotation to collect random and aligned fibers, respectively. The processed fiber mats were characterized by scanning (SEM) and transmission (TEM) electron microscopies, as well as by uni-axial tensile testing. To determine the reinforcing effects on the flexural strength of a dental resin composite, bar-shaped (20×2×2 mm(3)) resin composite specimens were prepared by first placing one increment of the composite, followed by one strip of the mat, and one last increment of composite. Non-reinforced composite specimens were used as the control. The specimens were then evaluated using flexural strength testing. SEM was done on the fractured surfaces. The data were analyzed using ANOVA and the Tukey׳s test (α=5%). Nanotubes were successfully incorporated into the nylon-6 fibers. Aligned and random fibers were obtained using high- and low-speed electrospinning, respectively, where the former were significantly (p<0.001) stronger than the latter, regardless of the nanotubes׳ presence. Indeed, the dental resin composite tested was significantly reinforced when combined with nylon-6 fibrous mats composed of aligned fibers (with or without nanotubes) or random fibers incorporated with nanotubes at 0.5 wt%.

Influence of zirconia surface treatment on veneering porcelain shear bond strength after cyclic loading.

STATEMENT OF PROBLEM: The influence of yttria-stabilized tetragonal zirconia polycrystal surface treatment on veneering porcelain shear bond strength after cyclic loading is not fully understood. PURPOSE: The purpose of this study was to investigate the influence of yttria-stabilized tetragonal zirconia polycrystal surface treatment on veneering porcelain shear bond strength and cyclic loading on the shear bond strength between the 2 materials. MATERIAL AND METHODS: A total of 48 cylinder-shaped yttria-stabilized tetragonal zirconia polycrystal specimens were fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM), sintered for 8 hours at 1500°C, ground with 320-grit diamond paper, and divided into 4 groups (n = 12) according to surface treatment as follows: no treatment/control; heat treatment of 650°C to 1000°C at 55°C/min; airborne-particle abrasion with 50-µm alumina at 0.4 MPa pressure for 10 seconds; or heat treatment after abrasion. A veneering porcelain cylinder was built and fired on the prepared yttria-stabilized tetragonal zirconia polycrystal specimens. The shear bond strength was tested with a universal testing machine. Six specimens from each group were subjected to cyclic loading (10000 cycles, 1.5 Hz, 10 N load) before testing. RESULTS: The mean ± SD ranged from 10.7 ± 15.4 to 34.1 ± 10.0. Three-way ANOVA found no statistically significant (P > .05) effect of surface treatment and cyclic loading on shear bond strength. The Sidak multiple comparisons procedure found that cyclic loading specimens had significantly lower shear bond strength than noncyclic loading specimens after airborne-particle abrasion without heat treatment (P = .013). CONCLUSIONS: Within the limitations of this study, the shear bond strength between yttria-stabilized tetragonal zirconia polycrystal and veneering porcelain was not significantly affected by surface treatment. Airborne-particle abrasion without subsequent heat treatment should be avoided as a surface treatment in fabrication methods.

Quantitative Determination of Carthamin in Carthamus Red by 1H-NMR Spectroscopy.

Carthamus Red is a food colorant prepared from the petals of Carthamus tinctorius (Asteraceae) whose major pigment is carthamin. Since an authentic carthamin standard is difficult to obtain commercially for the preparation of calibration curves in HPLC assays, we applied (1)H-NMR spectroscopy to the quantitative determination of carthamin in commercial preparations of Carthamus Red. Carthamus Red was repeatedly extracted in methanol and the extract was dissolved in pyridine-d(5) containing hexamethyldisilane (HMD) prior to (1)H-NMR spectroscopic analysis. The carthamin contents were calculated from the ratios of singlet signal intensities at approximately σ: 9.3 derived from H-16 of carthamin to those of the HMD signal at σ: 0. The integral ratios exhibited good repeatability among NMR spectroscopic analyses. Both the intra-day and inter-day assay variations had coefficients of variation of <5%. Based on the coefficient of absorption, the carthamin contents of commercial preparations determined by (1)H-NMR spectroscopy correlated well with those determined by colorimetry, although the latter were always approximately 1.3-fold higher than the former, irrespective of the Carthamus Red preparations. In conclusion, the quantitative (1)H-NMR spectroscopy used in the present study is simple and rapid, requiring no carthamin standard for calibration. After HMD concentration has been corrected using certified reference materials, the carthamin contents determined by (1)H-NMR spectroscopy are System of Units (SI)-traceable.

Application of 1H-NMR spectroscopy to validation of berberine alkaloid reagents and to chemical evaluation of Coptidis Rhizoma.

Berberine, palmatine, and coptisine are major pharmacologically active protoberberine alkaloids in Coptidis Rhizoma, and have been used as indices for chemical evaluation of the crude drug. (1)H-NMR spectroscopy was applied to determination of purities of commercial reagents of protoberberine alkaloids. The purities of the alkaloids were calculated from the ratios of the intensities of the H-13 singlet signal at about δ 8.7 ppm of target protoberberine alkaloids to integration of a hexamethyldisilane (HMD) signal at 0 ppm. The concentration of HMD was corrected with SI traceability using potassium hydrogen phthalate of certified reference material (CRM) grade. The purity of the reagent estimated by the (1)H-NMR was, in general, lower than that claimed by the manufacturer, leading to over-estimation of the alkaloid contents of Coptidis Rhizoma when determined by HPLC. The present quantitative (1)H-NMR method was also applicable to direct determination of protoberberine alkaloid contents in Coptidis Rhizoma.

Construction of database for three-dimensional human tooth models and its ability for education and research--Carious tooth models -.

To construct a human teeth database which is freely available to researchers and students, three-dimensional human tooth models were generated in a previous study, by means of micro-CT, from 35 human teeth extracted during orthodontic treatment. In this study, X-ray images of 55 extracted human teeth were acquired using three-dimensional micro-CT at a resolution of 50x50x50 microm, and then visualized using a numerical data visualization software. These carious tooth models provided insight into the morphology and progression of carious defects as well as a rare insight into the morphology of carious tooth pulp, therefore rendering them as a useful tool and efficient method for dental students' learning. Moreover, these three-dimensional models could be simultaneously observed and used by many students and researchers at any one time, which was a superior advantage than having only one actual tooth for learning and study by many.

Quantitative determination of atractylon in Atractylodis Rhizoma and Atractylodis Lanceae Rhizoma by 1H-NMR spectroscopy.

(1)H-NMR spectroscopy was successfully applied to the quantitative determination of atractylon in Atractylodis Rhizoma (dried rhizomes of Atractylodes ovata and A. japonica) and Atractylodis Lanceae Rhizoma (dried rhizomes of Atractylodes lancea and A. chinensis). The analysis was carried out by comparing the integral of the H-12 singlet signal of atractylon, which was well separated in the range of delta 6.95-7.05 ppm in the NMR spectrum, with the integral of a hexamethyldisilane (HMD) signal at delta 0 ppm. The atractylon contents obtained by the (1)H-NMR spectroscopy were consistent with those obtained by the conventional HPLC analysis. The present method requires neither reference compounds for calibration curves nor sample pre-purification. It also allows simultaneous determination of multiple constituents in a crude extract. Thus, it is applicable to chemical evaluation of crude drugs as a powerful alternative to various chromatographic methods.

Nonlinear stress analysis of titanium implants by finite element method.

With use of dental implants on the rise, there is also a tandem increase in the number of implant fracture reports. To the end of investigating the stress occurring in implants, elasticity and plasticity analyses were performed using the finite element method. The following results were obtained: (1) With one-piece type of implants of 3.3 mm diameter, elasticity analysis showed that after applying 500 N in a 45-degree direction, stress exceeding 500 MPa which is the proof stress of grade 4 pure titanium - occurred. This suggested the possibility of fatigue destruction due to abnormal occlusal force, such as during bruxism. (2) With two-piece type of implants that can tolerate vertical loading of 5,000 N, plasticity analysis suggested the possibility of screw area fracture after applying 500 N in a 45-degree direction. (3) On the combined use of an abutment and a fixture from different manufacturers, fracture destruction of even Ti-6Al-4V, which has a high degree of strength, was predicted.

High temperature characteristics and solidification microstructures of dental metallic materials. Part III alloys for metal-bond porcelain.

The thermal expansion rate, coefficient of thermal expansion, and high temperature strength of two types of commercially available alloy for metal-bond porcelain, KIK-HII (KIK) and Degubond-J2 (J2), were evaluated up to the liquidus point temperature using a thermo-mechanical analyzer. Furthermore, microstructure in the solid-liquid coexisting region was observed for evaluation. Our results revealed the following findings: 1. For KIK, solidus point was 1,209.3 +/- 3.2 degrees C, liquidus point was 1,308.3 +/- 7.10 degrees C, and melting expansion rate was 0.41+/- 0.16%. 2. For J2, solidus point was 1,198.3 +/- 0.6 degrees C, liquidus point was 1,253.0 +/- 4.4 degrees C, and melting expansion rate was 4.50 +/- 0.80%. 3. At high temperature, the mechanical characteristics of KIK greatly differed from those of J2. The risk of causing deformation during porcelain baking was suggested for KIK. Removal of segregation during casting was considered difficult in J2.

Bond strength of resin cements to H2O2-treated titanium plates.

OBJECTIVE: This study investigated the effects of H(2)O(2)-treatment of titanium surfaces on cement shear bond strengths, and characterized H(2)O(2)-treated titanium surfaces. METHODS: Using 34.5% hydrogen peroxide solution, cp Ti plates (10 mm x 10 mm x 1 mm) were treated by (1) an immersion method, and (2) halogen irradiation while immersed in H(2)O(2) for varying times. A cylindrical block (6 mm diameter, 4 mm height) of four different cements was bonded onto H(2)O(2)-treated surfaces. The cement bond strengths were evaluated under shear mode. Treated surfaces were also characterized for color change, wettability, AC impedance, and transmission electron diffraction of stripped oxide film. RESULTS: The cement shear bond strength of cp Ti treated with H(2)O(2) and halogen for 160 s was the highest and was approximately 14 times higher than the un-treated control cp Ti plates. Bond strengths are correlated linearly to wettability. The more surface wetted with the cement material, the higher the resultant shear bond strength value. SIGNIFICANCE: These results suggest that a combined treatment of hydrogen peroxide and halogen light irradiation provides an effective surface condition with appropriate oxide film thickness to enhance the cement bond strength.

High temperature characteristics and solidification microstructures of dental metallic materials. Part II. ADAS Type 3 gold alloy.

Previously, high temperature properties of the silver-palladium-copper-gold alloy were investigated. In this study, the thermal expansion percentage and coefficient, and high temperature strengths of ADAS Type 3 gold alloy were investigated up to the liquidus temperature. Furthermore, microstructural and compositional changes in the solid/liquid dual phase were studied. The following conclusions were obtained. (1) The solidus point of the Type 3 gold alloy was 899.3+/-11.7 degrees C, and the liquidus point was 962.3+/-2.4 degrees C. (2) The thermal expansion percentage at the solidus point was 1.636+/-0.046%, while it was 4.853+/-0.213% for the liquidus point. The thermal expansion percentage of the melt was 3.217+/-0.257%. (3) The melt expansion was observed even under the measuring pressure of 373.75 HPa, which was quite different from the fact that the melt expansion disappeared at the pressure of 20.87 HPa for the silver-palladium-copper-gold alloy. (4) The morphology of solid phase in the solid/liquid dual zone of this alloy was quite different from those observed with the silver-palladium-copper-gold alloy.

Effects of repeated baking on the mechanical and physical properties of metal-ceramic systems.

This study evaluates effects of repeated baking processes on the mechanical and physical properties of single and triple applications of opaque, body and enamel porcelains fused to three different metal substrates (precious metal, semi-precious metal and non-precious metal). The vintage halo porcelain system was employed and fused to metals. Fused samples were subjected to three-point bend tests to evaluate bend strength and modulus of elasticity. It was found that, by increasing repeated baking cycles, (1) body and enamel porcelains increased bend strengths but opaque porcelain did not show any changes, (2) all triple-layered porcelains fired to metals increased bend strengths, and (3) all three porcelains and metal substrates did not exhibit changes in thermal expansion percentage. It was concluded that repeating baking procedures up to 10 cycles did not exhibit any adverse effects on the final properties of porcelain-fired to metals, rather it was noticed that mechanical strengths increased by increasing cycles.

In situ monitoring of metal nanoparticle self-assembly on protein-functionalized glass by broadband optical waveguide spectroscopy.

Broadband, time-resolved optical waveguide (OWG) spectroscopy has been used for in situ, real-time investigation into the self-assembly of metal nanoparticle monolayers. The OWG spectroscopy makes it possible to use the transverse electric (TE) and transverse magnetic (TM) modes to measure surface plasmon absorption of immobilized metal nanoparticles in two directions, parallel and normal to the waveguide surface. Therefore, this technique can provide direction-dependent information on the metal nanoparticles at the interface. In this paper, a 50-microm-thick glass plate was used as a slab waveguide and the kinetics of Au nanoparticle adsorption on a hemoglobin-functionalized glass substrate was examined in the early stage of self-assembly. The findings show that with the TE mode the surface plasmon resonance (SPR) behavior for immobilized Au nanoparticles is different from that with the TM mode.

High temperature characteristics and solidification microstructures of dental metallic materials part I: silver-palladium-copper-gold alloy.

Ag-Pd-Cu-Au alloy was subjected to a Thermo-Mechanical Analyzer to investigate high temperature properties up to its liquidus temperature. Microstructural examination and elemental analysis with EPMA were also conducted in the solid/liquid mixture region. The following conclusions were obtained. (1) The solidus temperature was 838.3 +/- 2.52 degrees C and 957.7 +/- 1.53 degrees C for the liquidus point. (2) Thermal expansion coefficients were 1.39 +/- 0.08% at the solidus, 2.338 +/- 0.13% at the liquidus, and the melting expansion coefficient was 0.932 +/- 0.058%. (3) The expansion during melting was controlled by a small amount of pressure such as 1/100 of the air pressure, therefore the fit accuracy of castings is suggested not to be influenced by the solidification shrinkage. (4) Although the softening heat treatment and casting exhibited an influence on thermal expansion behavior, casting temperature in addition to post-casting plastic deformation did not show an effect on the thermal expansion. (5) The yield strength at 750 degrees C was reduced down to about 1/400 of that at room temperature, and the modulus of elasticity was about 1/100 of the room temperature value.

Colloidal gold submonolayer-coated thin-film glass plates for waveguide-coupled surface plasmon resonance sensors.

A novel optical sensor based on spectroscopic measurement of the plasmon absorption of a colloidal gold submonolayer immobilized upon a planar waveguide has been developed for label-free detection of biomolecular interactions at the sensor's surface. We fabricated the sensor by locally modifying a 50-microm-thick glass plate with hemoglobin (Hb) and then self-assembling gold colloids from the aqueous solution onto the Hb-modified area of the glass plate. Polychromatic light from a xenon-arc lamp was launched into the thin-film glass plate by use of a broadband fiber-coupling method. With the use of a CCD detector to monitor the light beam emitted from an end face of the glass plate, the plasmon absorption spectrum of the colloidal gold submonolayer was determined to depend on the polarization states of the guided light and to change with the refractive index of the medium in contact with the colloids. In addition to simplicity of fabrication and the ease of use, the sensor yields a larger absorbance sensitivity than the normal transmission measurement.

Cement bond strengths of titanium plates.

The success of the oral rehabilitation of implant patients depends not only on the osseointegration of implant fixtures but also on maintaining the integrity of the connection of prosthetic superstructures to these fixtures. It was an objective of the present study to evaluate and compare cement bond strengths among rolled (R), cast (C) and metal-injection-molded (M) commercially pure titanium plates which were bonded with Panavia 21 (Kuraray) and Imperva (Shofu) cements. Two plates (15x5x1 mm) of each R, C, and M were lap-jointed (lap length: 5 mm). The joints were stored in 37 degrees C distilled water for 24 h, followed by tensile tests with an INSTRON system under 1 mm/min crosshead speed. It was found that the bond strength of R with Panavia 21 (PAN) was 5.31 (SD:1.5) MPa and 2.30 (0.83) MPa with Imperva (IMP) cement. These were improved by applying an alloy primer to 7.08 (1.31) MPa and 6.72 (1.63) MPa, respectively. Using PAN with primer application, C and M samples showed bond strengths of 7.99 (1.31) and 7.20 (2.50) MPa, while they were 5.83 (2.15) and 6.79 (2.09) MPa using IMP with primer. There was a significant difference (p<0.01) between PAN and IMP cements for C samples. Additionally, samples were pre-oxidized at 100 degrees C in air for 10 min. Bond strengths of PAN with the primer were 5.69 (2.25), 9.14 (1.28), and 5.60 (3.13) MPa for R, C, and M sample groups. If the cement with the primer was applied immediately after the polishing (instead of pre-oxidized surfaces), bond strengths were improved to 9.14 (1.78) for R, 9.29 (1.85) for C, and 9.36 (1.81) MPa for M sample group. At p<0.05 level, there was a significant difference between surface pre-condition of R and M, but no significance with C.

Adsorption behavior of cytochrome c, myoglobin and hemoglobin in a quartz surface probed using slab optical waveguide (SOWG) spectroscopy.

Slab optical waveguide (SOWG) spectroscopy was used to observe the adsorption behavior of three important heme proteins, namely cytochrome c, myoglobin and hemoglobin, in a quartz surface. Using prism-coupled polychromatic visible light propagated into a quartz waveguide by internal total reflection, the real-time monitoring of evanescent wave absorption revealed a strong dependence of the protein-surface interaction on the protein concentration, the solution pH and the ionic strength. For the three proteins studied, the absorbance-bulk concentration ratio was higher at low bulk concentrations, and decreased at higher concentrations. For cytochrome c and myoglobin, the absorbance approached a limiting value, but buffered hemoglobin surprisingly did not show any indication of forming a signal plateau. Moreover, the slow introduction of protein into the solution lessened the total adsorbed amount per unit area. These observations suggested a possible conformational transition of the protein molecules at the quartz surface after adsorption. For a bulkier protein, hemoglobin, adsorption onto the quartz surface was enhanced in the presence of a phosphate buffer, while the opposite effect was observed for the smaller cytochrome c and myoglobin molecules. The results of pH studies concurred with the electrostatic interactions predicted from the isoelectric data of proteins and the quartz surface.

Effect of wax melting range and investment liquid concentration on the accuracy of a three-quarter crown casting.

STATEMENT OF PROBLEM: Dental casting accuracy is influenced by the setting expansion of investment materials. Although setting expansion can help compensate for casting shrinkage, it cannot be fully realized under a confined wax pattern. Exactly how soft a wax pattern should be to ensure optimum setting expansion has not been determined. PURPOSE: In this study, the relationship between wax characteristics and the casting accuracy of a three-quarter crown was investigated. MATERIAL AND METHODS: Four different wax materials were used: paraffin 135 with a softening temperature of 37.5 degrees C (P38), paraffin 1080 with a softening temperature of 63.5 degrees C, Shofu Red with a softening temperature of 41.5 degrees C, and Shofu Hard with a softening temperature of 51 degrees C. Two mixtures of phosphate-bonded investment were prepared: one with 100% special liquid and another with 75% special liquid plus 25% distilled water. For both, the liquid/powder ratio was 16:100. A type IV gold alloy was cast into a three-quarter crown mold. The discrepancy at 6 locations (1 lingual, 1 mesial, 1 distal, and 3 facial) was measured with a traveling microscope. Five readings were collected. Means and standard deviations were calculated for all data. A 2-way analysis of variance followed by the Student-Newman-Keuls test for multiple comparisons was used to identify significant differences between groups at the 95% confidence level. RESULTS: For the gingival measurement sites (lingual, mesial, and distal), there was no significant difference in cast adaptation when Shofu Hard and paraffin 1080 waxes were used. However, the results with these 2 waxes were different than with Shofu Red and P38. For the 3 facial measurement sites, significantly different measurements were found for each wax; P38 demonstrated the best results. Casting shrinkage was smaller with the use of 100% special liquid. CONCLUSION: Within the limitations of this study, casting shrinkage was affected by the type of wax used and was sensitive to the site at which dimensional measurements were performed. The higher the softening temperature, the larger the casting shrinkage.

Optical waveguide spectrometer based on thin-film glass plates.

Commercially available thin-film glass plates have been successfully used for optical waveguide spectroscopy of chemical and biological films adsorbed upon the plates' surfaces. A 50-mum -thick glass plate was placed in contact with two parallel strips of silicone rubber supported on a slide glass. The plate area between the rubber strips served as the waveguiding region, eliminating the negative effect of the substrate on absorbance sensitivity. We coupled white light into the waveguide by focusing the light from a xenon lamp onto one end of a glass fiber and then inserting the other end into a glycerol drop overlaid upon the plate's surface. With a CCD detector, light at wavelengths as short as 360 nm was found to transmit out of the plate's end face. The propagation loss of the waveguide was measured to be