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Biomedical subjects

Eiji Kawada

Publications and source records attributed to Eiji Kawada.

12 recordsLinked to original sources

Adhesion of mouse fibroblasts on hexamethyldisiloxane surfaces with wide range of wettability.

Surface wettability is an important physicochemical property of biomaterials, and it would be more helpful for understanding this property if a wide range of wettability are employed. This study focused on the effect of surface wettability on fibroblast adhesion over a wide range of wettability using a single material without changing surface topography. Plasma polymerization with hexamethyldisiloxane followed by oxygen (O2)-plasma treatment was employed to modify the surfaces. The water contact angle of sample surfaces varied from 106 degrees (hydrophobicity) to almost 0 degrees (super-hydrophilicity). O2 functional groups were introduced on polymer surfaces during O2-plasma treatment. The cell attachment study confirmed that the more hydrophilic the surface, the more fibroblasts adhered in the initial stage that includes super-hydrophilic surfaces. Cells spread much more widely on the hydrophilic surfaces than on the hydrophobic surfaces. There was no significant difference in fibroblast proliferation, but cell spreading was much greater on the hydrophilic surfaces. The fibronectin adsorbed much more on a hydrophilic surface while albumin dominated on a hydrophobic surface in a competing mode. These findings suggest the importance of the surface wettability of biomaterials on initial cell attachment and spreading. The degree of wettability should be taken into account when a new biomaterial is to be employed.

Animals↗

Micro-tensile bond strength of sound and caries-affected primary tooth dentin measured with original designed jig.

To measure the micro-tensile bond strength (MTBS) on sound and caries-affected primary tooth dentin using an original designed jig that was developed for making symmetric and uniformly-sized specimens for the micro-tensile strength testing. The MTBS of dumbbell-shaped specimens and matchstick-shaped specimens were measured. Dumbbell-shaped specimens: The occlusal surfaces of 15 sound primary molars were ground with a water-cooled air turbine using a diamond bur. The adhesive systems and resin-based composites were Clearfil SE Bond and Clearfil AP-X (SE group) and Single Bond and Z250 (SB group). Matchstick-shaped specimens: Sixteen primary molars (5 sound and 11 carious) were used. The occlusal surfaces of sound teeth were ground with a water-cooled air turbine using a diamond bur. Infected dentin was determined by a caries detecting dye solution and removed with a round-shaped steel bur under water-cooling and with a hand instrument. SE was applied. Data was statistically analyzed using ANOVA and Fisher's PLSD at p < 0.05. The MTBSs (MPa) for the dumbbell-shaped specimens were 8.9 +/- 7.0 in the SE group and 10.3 +/- 5.8 in the SB group and that for the matchstick-shaped specimens were 9.0 +/- 6.3 in the sound-SE group and 9.2 +/- 5.8 in the carious-SE group. No significant difference was observed among them.

Bisphenol A-Glycidyl Methacrylate↗

Control of bisphosphonate release using hydroxyapatite granules.

The efficacy of hydroxyapatite (HAp) as a carrier was investigated to establish a method of local administration of bisphosphonates (Bps), which has currently been administered systemically. HAp granules (300-500 microm in size) with different physicochemical features were prepared by altering the sintering temperature. To ascertain the physicochemical properties of the HAp granules, their crystallinity was assessed using X-ray diffraction, the surface morphology was examined under scanning electron microscopy, and the specific surface area and calcium dissolution were evaluated. Different Bps-HAp composites were subsequently prepared and the concentration of Bps released from these composites was measured. The influence of Bps-HAp composites on the rate of osteoclast survival was also evaluated. The results revealed that (1) HAp solubility depends on the sintering temperature; (2) The concentration of released Bps could be controlled by regulating the sintering temperature of HAp as a carrier; and (3) Bps released from Bps-HAp composites reduced the number of osteoclasts. These findings indicated that Bps-HAp composites could be locally administered as a drug delivery system to areas with bone resorption.

Animals↗

Resin bonding to dentin irradiated by high repetition rate Er:YAG laser.

OBJECTIVE: This study evaluated the influence of laser irradiation with a high pulse repetition rate on dentin bonding. BACKGROUND DATA: Although resin bonding to erbium:yttrium-aluminium-garnet (Er:YAG) laserirradiated dentin has frequently been investigated, the effects of a high pulse repetition rate have not yet been sufficiently investigated. METHODS: Four groups treated under different laser conditions were evaluated in this study: 100 mJ/pulse-10 pulses per second [pps], 50 mJ/pulse-20 pps, 33 mJ/pulse-30 pps, and the unlased condition as a control. The total energy used to irradiate each group was adjusted to 1.0 W. After bovine dentin specimens were irradiated by an Er:YAG laser, acid conditioners (10% citric acid/3% ferric chloride) were applied to the lased surface. Thereafter, a PMMA rod was bonded to the lased dentin using 4- META/MMA-TBB resin, and mini-dumbbell-shaped specimens were prepared. These specimens were then tested under tensile mode and fractured surfaces were observed under scanning electron microscopy (SEM). RESULTS: The bond strength of the unlased control was significantly higher than those of the three lased groups. Among the three lased groups, irradiation with higher output energy and lower pulse repetition rate tended to affect the higher bond strength. Upon SEM observation of the fractured surface, the lased groups showed the mixture of failure in the hybrid layer in almost part. There was no significant difference among the three lased groups. CONCLUSION: It can be concluded from the results of this study that a higher pulse repetition rate is not effective for resin bonding to laser-irradiated dentin.

Animals↗

Corrosion behavior and surface characterization of titanium in solution containing fluoride and albumin.

The objective of this study was to demonstrate the role of albumin on the corrosion behavior of titanium in a solution containing 2.0 g/l fluoride and either 0.1 or 1.0 g/l albumin. The corrosion behavior and surface characterization of passive films on titanium immersed in such a solution were examined. In addition, the change in pH and the concentration of dissolved titanium in the solution were examined. The results showed that the corrosion of titanium in a solution containing fluoride was distinct, and that adding albumin to the solution containing fluoride suppressed corrosion. Fluorine was detected on the titanium surface immersed in the solution containing fluoride, and dissolution of the titanium was confirmed. The titanium immersed in a solution containing both fluoride and albumin had an albumin film regardless of the albumin concentration. In addition, the amount of dissolved titanium from the titanium immersed in the solution was less than when the solution contained no albumin. It was suggested that the formation of adsorbed albumin films on or in the passive film acted to not only protect the titanium from attack by the fluoride but also suppressed dissolution of the titanium-fluoride compounds.

Albumins↗

Influence of fabrication techniques on retention force of fiber-reinforced composite posts.

The purpose of this study was to compare the retention force of FRC posts which were built up using direct and direct-indirect fabrication techniques with two fiber-reinforced core build-up systems (FibreKor and i-TFC). Posts were cemented in endodontically treated bovine single roots with resin cement using either direct or direct-indirect technique. Following which, the retention force of post-and-cores and fracture sites were examined. It was found that both the retention force and fracture site depended on the fabrication technique and resin cements. Post-and-cores built up with direct-indirect technique had greater retention force than those fabricated using direct technique. Fracture modes most frequently observed were adhesive failure at Resin/Dentin interface, a mixture of adhesive failures at Post/Resin and Resin/Dentin interfaces as well as cohesive failure of resin cements. Based on the results of this study, we concluded that when it comes to post-and-core build-up for endodontically treated tooth, the direct-indirect technique is more effective than the direct technique on the retention force of FRC posts.

Analysis of Variance↗

Effects of surface treatment and joint shape on microtensile bond strength of reattached root dentin segments.

STATEMENT OF PROBLEM: An effective bonding technique for reattaching vertical root fracture segments has not yet been established. PURPOSE: The purpose of this study was to investigate the effects of surface treatment and joint shape on bond strength of reattached root dentin segments. MATERIAL AND METHODS: Microtensile dentin specimens (n=120, cross-sectional area=1.5 mm2) were obtained from 12 bovine teeth roots, and fractured under a tensile force. The segments of each group (n=6) were reattached by a 4-META/MMA-TBB adhesive resin after different treatments (etching or polishing, a 50-microm or 500-microm gap space, butt or wedge joint). The group with a 50-microm gap space and butt joint, which was not etched or polished, served as the control. After 24 hours of storage in 0.9% normal saline solution or thermal cycling (3000 cycles, 4 degrees C and 60 degrees C), the specimens were fractured in a universal testing machine at a crosshead speed of 1.0 mm/min. The microtensile bond strengths (MPa) were recorded. The bonded interface and fractured surface were observed by SEM (original magnification x 1000). The results were analyzed by a 2-way analysis of variance and the Fisher protected least significant difference post-hoc test (alpha=.05). RESULTS: Significantly higher bond strengths (P=.0001) were shown for the nonpolished group (9.78 +/- 4.44 MPa) and the etched group (9.31 +/- 1.23 MPa) than for the polished group (fractured before test). The wedge-shaped joint exhibited the highest bond strength (18.57 +/- 3.40 MPa, P=.0017). SEM observations showed that the penetration of resin tags along the oblique dentinal tubules was within the wedge joint. CONCLUSION: Etching and oblique tubule orientation contributed to significantly high bond strength of reattached segments to dentin after vertical root fracture.

Acid Etching, Dental↗

Fatigue strengths of particulate filler composites reinforced with fibers.

The aim of this study was to evaluate the dynamic fatigue strengths at 10(5) cycles and the strains of particulate filler composite resins with and without reinforcing fibers. An UHMWPE (Ribbond), a polyaromatic polyamide fiber (Fibreflex), and three glass fibers (GlasSpan, FibreKor, Vectris Frame) were used to reinforce the particulate filler composite resins. The fatigue properties were measured in three-point bending mode using a servohydraulic universal testing machine at a frequency of 5 Hz, until failure occurred or 10(5) cycles had been completed. The fatigue strengths at 10(5) cycles were determined by the staircase method. The fractured aspects of specimens were evaluated by an optical and scanning electron microscope. The fatigue strengths of particulate filler composite resins were 49-57 MPa, and those of fiber-reinforced were 90-209 MPa. Unidirectional glass fibers showed higher reinforcing effects on the fatigue strengths of composite resins. The strain of UHMWPE-reinforced composite was largest.

Analysis of Variance↗

Corrosion behavior and surface characterization of Ti-20Cr alloy in a solution containing fluoride.

The purpose of this study was to investigate the correlation between corrosion resistance and surface composition of an experimental Ti-20 mass% Cr casting alloy in a saline solution containing fluoride. The alloy had a greater resistance to corrosion in a fluoride-containing saline solution than did commercially pure titanium. However, with confirmed dissolution of titanium and chromium, it meant that the fluoride in the saline solution corroded the alloy slightly. X-ray photoelectron spectroscopy analysis revealed that the surface composition of the alloy consisted of titanium and chromium oxides containing hydroxide. The [Ti]/([Ti] + [Cr]) ratio in the surface oxide film decreased when immersed in fluoride-containing saline solution, that is, the surface oxide film became chromium-rich oxide. Therefore, the alloy obtained good corrosion resistance to fluoride due to formation of a chromium-rich oxide film.

Chromium Alloys↗

Adhesion of 4-META/MMA-TBB resin to heated dentin: effects of pre-treatments with FeCl3 and/or HEMA.

The purpose of this study was to compare the tensile bond strengths (TBSs) and failure mode of 4-META/MMA-TBB resin to 60 degrees C-heated and unheated bovine dentin, especially to investigate the influence of ferric chloride contained in citric acid pre-conditioning. In addition, the effect of HEMA priming for heated dentin was also evaluated. The TBSs to heated dentin were significantly lower than those to unheated dentin. Adhesive failures were observed in most specimens of the heated and HEMA-non primed group. HEMA application to heated dentin significantly increased the TBSs in each acid conditioning, which were also significantly higher than those of the unheated and ferric chloride-contained citric acid-conditioned group. It was clarified that heating dentin decreased the bond strength without HEMA priming even if the dentin surfaces were acid conditioned with 10-3, while HEMA priming after acid conditioning recovered the bond strength.

Acid Etching, Dental↗

The influence of albumin on corrosion resistance of titanium in fluoride solution.

Proteins can interact with corrosion reactions in several ways. In this study, we investigated the effect of albumin on the corrosion resistance of titanium in the presence of fluoride. The effects of the NaF concentration, albumin concentration, and pH on the corrosion characteristics of commercially pure titanium (CP-Ti) were examined by means of electrochemical techniques. The corrosion resistance of titanium decreased as the NaF concentration increased and as pH decreased. The corrosion resistance of titanium in NaF solutions was improved in the presence of albumin. The natural electrode potential was elevated, and the passive current density was reduced by albumin at a concentration of 0.01%. The polarization resistance rose with increased concentrations of albumin in fluoride solution. These results showed that the albumin in saliva and dental plaque affected the corrosion resistance of CP-Ti in fluoride solution.

Albumins↗

Effect of tubule orientation and dentin location on the microtensile strength of bovine root dentin.

To investigate the mechanical properties of root dentin and to further clarify the cause of vertical root fracture (VRF), this study evaluated the effect of tubule orientation (parallel, perpendicular and oblique to the cross-section of dumbbell specimens in microtensile tests) and dentin location (cervical, middle, and apical location of the root) on the microtensile strength of bovine root dentin. Each specimen was stressed in tension at a crosshead speed of 1.0 mm/min. The results of the microtensile strength measurements were statistically analyzed with one-way ANOVA and the Fisher PLSD. The oblique group (95.18+/-23.80 MPa) was significantly (p<0.01) higher than the parallel group (38.93+/-5.28 MPa) or the perpendicular group (32.64+/-4.69 MPa). There were no significant differences among the different dentin locations within the parallel group (p>0.05). It was clarified that the VRF occurs frequently in practical situations due to the tubule orientation of root dentin.

Analysis of Variance↗