Bio-functionalized titanium surfaces with modified silk fibroin carrying titanium binding motif to enhance the ossific differentiation of MC3T3-E1.

Silk fibroin (SF) from Bombyx mori has superior properties as both a textile and a biomaterial, and has been used to functionalize the surfaces of various medical inorganic materials including titanium (Ti). In this study, we endowed SF with reversible binding ability to Ti by embedding a titanium binding motif (minTBP-1 and RKLPDA). Artificial SF proteins were first created by conjugating gene cassettes for SF motif (AGSGAG) and minTBP-1 motif with different ratios, which have been shown to bind reversibly to Ti surfaces in quartz crystal microbalance analyses. Based on these results, the functionalized SF (TiBP-SF) containing the designed peptide [TS[(AGSGAG)3 AS]2 RKLPDAS]8 was prepared from the cocoon of transgenic B. mori, which accelerates the ossific differentiation of MC3T3-E1 cells when coated on titanium substrates. Thus, TiBP-SF presents an alternative for endowing the surfaces of titanium materials with osseointegration functionality, which would allow the exploration of potential applications in the medical field.

Quantitative Evaluation of MDP-Ca Salt and DCPD after Application of an MDP-based One-step Self-etching Adhesive on Enamel and Dentin.

PURPOSE: To investigate the effects of an experimental 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based one-step self-etching adhesive (EX adhesive) applied to enamel and dentin on the production of calcium salt of MDP (MDP-Ca salt) and dicalcium phosphate dehydrate (DCPD) at various periods. MATERIALS AND METHODS: The EX adhesive was prepared. Bovine enamel and dentin reactants were prepared by varying the application period of the EX adhesive: 0.5, 1, 5, 30, 60 and 1440 min. Enamel and dentin reactants were analyzed using x-ray diffraction and solid-state phosphorus-31 nuclear magnetic resonance (31P NMR). Curvefitting analyses of corresponding 31P NMR spectra were performed. RESULTS: Enamel and dentin developed several types of MDP-Ca salts and DCPDs with amorphous and crystalline phases throughout the application period. The predominant molecular species of MDP-Ca salt was determined as the monocalcium salt of the MDP monomer. Dentin showed a faster production rate and greater produced amounts of MDP-Ca salt than did enamel, since enamel showed a knee-point in the production rate of the MDP-Ca salt at the application period of 5 min. In contrast, enamel developed greater amounts of DCPD than did dentin and two types of DCPDs with different crystalline phases at application periods > 30 min. The amounts of MDP-Ca salt developed during the 30-s application of the EX adhesive on enamel and dentin were 7.3 times and 21.2 times greater than DCPD, respectively. CONCLUSION: The MDP-based one-step adhesive yielded several types of MDP-Ca salts and DCPD with an amorphous phase during the 30-s application period on enamel and dentin.

Ceramic bond durability and degradation mechanism of commercial gamma-methacryloxypropyl trimethoxysilane-based ceramic primers.

PURPOSE: To investigate the bond durability and degradation mechanism of various commercial ceramic primers that are based on gamma-methacryloxypropyl trimethoxysilane (gamma-MPTS) and contain various organic additives. The null hypotheses tested were that (1) the type of ceramic primer had no effect on the bond strength after thermocycling and (2) the type of ceramic primer had no effect on the water contact angle after rinsing with THF. METHODS: The adherent was a silica-based ceramic block used for computer-aided design/computer-aided manufacturing (CAD-CAM). Four commercial ceramic primers, Clearfil Mega Bond Porcelain Bonding kit (CM), Tokuso ceramic primer (TC), GC ceramic primer (CP), and Porcelain Liner M (PL), were compared with a simplified experimental ceramic primer (EP) that comprised gamma-MPTS and an inorganic acid (hydrochloric acid) but no other organic additives. The specimens for the adhesion test were prepared after a dual-curing type resin cement (Link Max) had adhered to the ceramic surfaces treated with each ceramic primer. The bonded specimens were then stored in water at 37 degrees C for 1 day. Then, the bonded specimens were thermocycled between 5 degrees C and 55 degrees C in water baths for 5000 or 10,000 cycles. The dwell time in each water bath and the transfer time were 60 and 7 seconds, respectively. The shear bond strength of resin to the ceramic surface was measured under a crosshead speed of 1.0 mm/minute by a conventional testing machine. Thereafter, the fracture mode for each specimen was determined. In addition, the water contact angle on the treated ceramic surfaces was measured before and after THF using a cotton pellet. As a control, the contact angle on the ground ceramic surface was measured without any ceramic primer. RESULTS: For all samples, thermocycling led to an increase in the frequency of interfacial failure, reflecting reduced mean bond strength of the resin to the treated ceramic surfaces. However, the bond degradation behavior differed among commercial ceramic primers; in particular, PL exhibited different ceramic bond durability from the others. However, the mean bond strength of PL was only 11.8 MPa and over half the specimens exhibited interfacial failure. In contrast, EP provided significantly higher mean bond strength of 17.2 MPa and most specimens exhibited cohesive failure of the ceramic. Furthermore, the contact angle measurements clearly demonstrated that the commercial ceramic primers created a multilayer consisting of gamma-MPTS species and the organic additives on the ceramic surface.

Effect of the amount of light energy transmitted through CAD/CAM resin block on bonding performance of four types of resin cement adhesive systems.

Resin-ceramic hybrid materials for computer-aided design/computer-aided manufacturing (CAD/CAM resins) have been developed. In this study, the effects of the amount of light energy transmitted through the four types of 1.5-mm-thick CAD/CAM resin blocks on the bond performance of corresponding resin cement adhesive systems consisting of an adhesive and a dual-curable resin cement were examined. The bond strengths of the four types of resin cement adhesive systems decreased with decreasing the amount of light energy transmitted through CAD/CAM resin block, due to a decrease in the light-curable ability of dual-curable resin cements. However, the degradation behavior of the bond strengths was strongly affected by the types of adhesives and initiator systems utilized. The adhesive consisting of a dimethacrylate monomer and redox-initiators enhanced the bonding performance of the dual-curable resin cement more effectively than the adhesive, which consists of a dimethacrylate monomer and photo-initiators or a γ-me thacryloxypropyltrimethoxysilane and a 10-methacryloyloxydecyl dihydrogen phosphate.

Development of dual-curing type experimental composite resin cement for orthodontic bonding -effect of additional amount of accelerators on the mechanical properties-.

In this study, a dual-curing type composite resin cement that included a photo-initiator and two accelerators was designed. In particular, special emphasis was made on addressing questions on the effects from different amounts of additional accelerators on the flexural strength of the designed experimental composite resin cement, as well as on the tensile bond strength of the bracket bonded onto the enamel surface by the experimental composite resin cement. When 0.25 mass% of the p-tolydiethanolamine and sodium p-toluenesulfinate were added, the maximum flexural strength was obtained for the chemical-cured and dual-cured experimental composite resin cement. The dual-cured experimental composite resin cement's flexural strength value was in the mid-range of the values exhibited from the commercial resin cements. However, the dual-cured experimental composite resin cement exhibited noticeably high tensile bond strength when compared with the results obtained with the commercial resin cements.

Osteoblast-like cell proliferation on tape-cast and sintered tricalcium phosphate sheets.

The influence of sintering temperature on the in vitro proliferation of osteoblast-like cells to sintered tricalcium phosphate (TCP) sheets prepared by tape-casting was investigated. Green sheets of tape-cast beta-TCP were sintered for 2h in a furnace at atmospheric pressure at five different sintering temperatures: 900, 1000, 1100, 1150 and 1200 degrees C. The number of osteoblast-like (MC3T3-E1) cells deposited onto TCP sheets was counted after cell cultivation for 1week and was found to have increased with increasing sintering temperature. The TCP sheets sintered at 900 degrees C exhibited a significantly lower cell number than TCP sheets sintered at 1000, 1100, 1150 and 1200 degrees C. In the attenuated total reflection infrared spectra, the peaks around 900-1150cm(-1), corresponding to the P-O vibration mode of the phosphate group, gradually decreased and shifted to lower wavenumbers with increasing sintering temperature. Meanwhile, the zeta potential of TCP sintered at 900 degrees C showed a highly negative charge when compared with the other groups. This would suggest that the higher solubility of the TCP sheets sintered at 900 degrees C exerted the higher negative charge obtained from zeta potential measurement. Within the limitations of this study, it was indicated that osteoblast-like cell proliferation increased with increasing sintering temperature. The biological stability of the sintered TCP sheet surface was considered to have affected cell proliferation.

Effects from applying adhesive agents onto silanated porcelain surface on the resin bond durability.

This study examined the effects on the bond durability of resins arising from the application of adhesive agent on porcelain surface, silanated by a ceramic primer consisting of gamma-methacryloxypropyltrimethoxysilane (gamma-MPTS), by comparing shear bond strengths before and after thermocycling. When an adhesive agent was applied to a porcelain surface which had been silanated by a ceramic primer for 10 seconds, a significant reduction in resin bonding durability was observed. Extending the silanating period of the ceramic primer to 60 minutes resulted in an increase in resin bonding durability to the porcelain surface. However, the effect on resin bonding durability resulting from the application of adhesive agent was nearly the same as that without adhesive agent application, even though the porcelain surface was silanated for 60 minutes. In other words, positive effects arising from adhesive agent application on resin bonding durability were not observed.

[Bonding of resin cement to bleached dental enamel].

PURPOSE: The effects of bleaching times, types of etching agent and storage period of bleached bovine tooth on the shear bond strength of resin cement to the enamel were examined. MATERIALS AND METHODS: Bovine teeth were repeatedly bleached 0, 1, 3, and 5 times then stored in 37 degrees C water for 1 week. The effect of bleaching number of the bovine tooth on the bond strength of resin cement to the enamel was investigated using 40% phosphoric acid (EG) etching technique. Next, the effects of types of etching agent and of storage period of bleached bovine tooth with three times in 37 degrees C water on the bond strength were studied using 10% citric acid-3% ferric chloride (10-3) or 10% citric acid (10-0) solution. RESULTS: The bleaching of bovine tooth allowed for a dramatic decrease in the bond strength from 18.3 MPa to 9.8 MPa (1 time), and 3.9 MPa (3 times), even though the bovine enamel was etched by EG. However, when 10-3 or 10-0 solution was applied to the three times bleached enamel, bond strengths were 13.9 and 10.0 MPa, respectively. Furthermore, prolonging of the storage period of the three times bleached bovine tooth in water to 2 months resulted in a increase in the bond strength from 3.9 to 10.1 MPa, even if bovine enamel was etched by EG, and close to that obtained from the 10-3 etching. CONCLUSION: To obtain the expected bond strength to bleached enamel, it is better to wait for 2 months for a restoration and use the 10-3 etching.

Color stability of glass-fiber-reinforced polypropylene for non-metal clasp dentures.

PURPOSE: The purpose of this study was to investigate the color stability of a glass-fiber-reinforced thermoplastic (GFRTP), for use in non-metal clasp dentures (NMCDs). METHODS: GFRTPs composed of E-glass fibers and polypropylene with 2 mass% of pigments were fabricated using injection molding. According to our previous study on the optimum fiber content for GFRTPs, we prepared GFRTPs with fiber contents of 0, 10, and 20 mass% (GF0, GF10, and GF20). Commercially available NMCD and PMMA materials were used as controls. The color changes of GFRTPs at 24h, and at 1, 2, and 4 weeks of coffee immersion at 37°C were measured by colorimetry, using the Commission Internationale de l'Eclairage (CIE) Lab system. The color stabilities of the GFRTPs were evaluated in two units: the color difference (ΔE∗) and National Bureau of Standards (NBS) units. RESULTS: After immersion, none of the GFRTPs showed visible color change. From the colorimetry measurement using the CIE Lab system, the ΔE∗ values of the GFRTPs were 0.65-2.45. The NBS values of the GFRTPs were 0.60-2.25, all lower than the threshold level of 3.0, demonstrating clinically acceptable color changes. On the other hand, an available polyamide-based NMCD material exhibited "appreciable" color change, as measured in NBS units. CONCLUSIONS: The results indicate that the GFRTPs showed clinically acceptable color stability and might be satisfactory for clinical use. Therefore, GFRTPs are expected to become attractive materials for esthetic dentures.

Glass fiber-reinforced thermoplastics for use in metal-free removable partial dentures: combined effects of fiber loading and pigmentation on color differences and flexural properties.

PURPOSE: The purpose of this study was to investigate the combined effects of fiber loading and pigmentation on the color differences and flexural properties of glass fiber-reinforced thermoplastics (GFRTPs), for use in non-metal clasp dentures (NMCDs). METHODS: The GFRTPs consisted mainly of E-glass fibers, a polypropylene matrix, and a coloring pigment: the GFRTPs with various fiber loadings (0, 10, and 20mass%) and pigmentations (0, 1, 2, and 4mass%) were fabricated by using an injection molding. The color differences of GFRTPs were measured based on the Commission Internationale de l'Eclairage (CIE) Lab color system, by comparing with a commercially available NMCD. The flexural properties of GFRTPs were evaluated by using a three-point bending test, according to International Standards Organization (ISO) specification number 20795-1. RESULTS: The visible colors of GFRTPs with pigment contents of 2mass% were acceptable for gingival color, and the glass fibers harmonized well with the resins. The ΔE* values of the GFRTPs with pigment contents of 2mass% obtained by using the CIE Lab system were lowest at all fiber loadings. For GFRTPs with fiber contents of 10 and 20mass% at 2mass% pigment content, these GFRTPs surpassed the ISO 20795-1 specification regarding flexural strength (> 60MPa) and modulus (> 1.5GPa). CONCLUSIONS: A combination of the results of color difference evaluation and mechanical examination indicates that the GFRTPs with fiber contents of 10 or 20mass%, and with pigment contents of 2mass% have acceptable esthetic appearance and sufficient rigidity for NMCDs.

Demineralization capacity of commercial 10-methacryloyloxydecyl dihydrogen phosphate-based all-in-one adhesive.

OBJECTIVE: We determined the amounts of calcium salt of 10-methacryloyloxydecyl dihydrogen phosphate (MDP-Ca salt) and dicalcium phosphate dihydride (DCPD) with an amorphous phase developed during the application of commercial MDP-based all-in-one adhesives to enamel and dentin. This is because the demineralization by MDP and following calcium salt formation of MDP may be limited by an ionic bond formation of MDP to hydroxyapaptite in the enamel and dentin and following intermediary layer formation of MDP, since MDP forms a chemically-stable adsorption layer. METHODS: Scotchbond Universal Adhesive, Clearfil Tri-S Bond ND, Clearfil Tri-S Bond ND Quick, G-Bond Plus and our designed MDP-based all-in-one adhesive were used. Enamel and dentin reactant residues of each adhesive were prepared by varying the adhesive application periods: 1, 30 and 60min, and were analyzed using phosphorous-31 nuclear magnetic resonance and X-ray diffraction. RESULTS: Increasing the adhesive application period to enamel and dentin led to the increased amount of MDP-Ca salt in contrast to amorphous DCPD. In the dentin, each adhesive showed a saturated value on the production amount of MDP-Ca salt when the adhesive was applied more than 30min. In contrast, in the enamel, each adhesive showed an intermediate value on the saturated production amount of MDP-Ca salt that the respective adhesive exhibited. This is due to MDP employed demineralizes the enamel and dentin until MDP was completely consumed yielding MDP-Ca salt. CONCLUSION: Commercial MDP-based all-in-one adhesives would not form an intermediary layer of MDP on hydroxyapatite throughout their application period to enamel and dentin. CLINICAL RELEVANCE: The rate of MDP-Ca salt produced by the demineralization of enamel and dentin depends on the components that constitute commercial adhesive more strongly than on the concentrations of MDP and water in the respective adhesive. This is because HEMA-containing adhesive shows a slower production rate of MDP-Ca salt than HEMA-free adhesive in the enamel and dentin samples.

NMR study on the demineralization mechanism of the enamel and dentin surfaces in MDP-based all-in-one adhesive.

The acidic monomers utilized in all-in-one adhesives play a key role in the enamel and dentin bonding performance. The purpose of this study is to investigate the mechanism by which 10-methacryloyloxydecyl dihydrogen phosphate (MDP) demineralizes the enamel and dentin surfaces prepared by a diamond bur in three types of experimental MDP-based all-in-one (EX) adhesives containing different amounts of water (46.6, 93.2 and 208.1 mg/g). The enamel and dentin reactants of EX adhesives were analyzed using solidstate phosphorous-31 nuclear magnetic resonance and X-ray diffraction. Increased amount of water led to increases in the efficacy by which MDP demineralizes the enamel and dentin surfaces. However, the rate of calcium salts of MDP produced slowed down at the water concentrations above 93.2 mg/g. The dentin yielded greater amounts of di-calcium salts of the MDP monomer and dimer than the enamel, which develops a different type of layered structure of MDP from the enamel.

Effect of the demineralisation efficacy of MDP utilized on the bonding performance of MDP-based all-in-one adhesives.

OBJECTIVES: The amounts of calcium salt of 10-methacryloyloxydecyl dihydrogen phosphate (MDP-Ca salt) and dicalcium phosphate dihydride (DCPD) with an amorphous phase produced by the demineralisation of enamel and dentin were determined using commercial MDP-based 2-hydroxyethyl methacrylate (HEMA)-containing and HEMA-free all-in-one adhesives. The effect of the amount of MDP-Ca salt produced on bonding performance to enamel and dentin was then characterized. METHODS: Three types of commercial HEMA-containing adhesives (Scotchbond Universal Adhesive, Clearfil Tri-S Bond ND, Clearfil Tri-S Bond ND Quick), a commercial HEMA-free adhesive (G-Bond Plus) and an experimental HEMA-free adhesive were used. The reactant residues of each adhesive were prepared after interacting with enamel and dentin samples for 60 s. The amounts of MDP-Ca salt and amorphous DCPD produced were determined using a phosphorous-31 nuclear magnetic resonance technique. Enamel and dentin bond strengths were measured for each adhesive, with and without thermocycling. RESULTS: The amounts of MDP-Ca salt and amorphous DCPD formed after interacting with enamel and dentin differed among the five adhesives and were independent of their pH values. Enamel showed a strong positive-correlation of the bond strength of the all-in-one adhesives to the amount of MDP-Ca salt produced, however, the dentin showed a weak negative-correlation. CONCLUSION: The HEMA-free all-in-one adhesives showed a greater efficacy to demineralise the enamel and dentin than the HEMA-containing all-in-one adhesives. The dentin showed a different effect of the amount of MDP-Ca salt produced on the bonding performance compared with enamel. CLINICAL SIGNIFICANCE: The enamel bond strength of MDP-based all-in-one adhesives strongly contributes to the demineralisation efficacy by the incorporation of MDP, in contrast to the dentin bond strength. However, the efficacy of MDP-based all-in-one adhesives to demineralise the enamel and dentin is not directly related to the pH value of the MDP-based all-in-one adhesive.

Effects of alumina air-abrasion and acidic priming agents on bonding between SUS XM27 steel and auto-polymerizing acrylic resin.

The purpose of this study was to evaluate the effects of functional monomers contained in the primers, as well as alumina particle abrasion on bonding between stainless steel and acrylic resin. SUS XM27 steel was primed with one of the following materials; Alloy Primer, Estenia Opaque Primer, M. L. Primer, and Super-Bond Liquid. Steel disks were either ground flat or alumina-blasted, primed with one of the four agents, and bonded with an acrylic resin (Unifast Trad). Bond strength was determined both before and after thermocycling (2,000 or 20,000 cycles). Among the four priming agents, the Alloy Primer and Estenia Opaque Primer, both of which contain 10-methacryloyloxydecyl dihydrogen phosphate (MDP), exhibited better bonding performance than the others. Alumina air-borne particle abrasion considerably improved the durability of bonding between the steel and the resin material. It can be concluded that alumina blasting followed by priming with an MDP agent is recommended for bonding the resin and SUS XM27 steel.

Multi-purpose bonding performance of newly synthesized phosphonic acid monomers.

Multi-purpose bonding performance of three kinds of newly synthesized phosphonic acid monomers was investigated. Methacryloxyalkyl or acryloxyalkyl phosphonoacetates of 6-MHPA, 6-AHPA, 10-MDPA were synthesized in 42.8-51.9% yields with a light yellow viscous liquid, and identified as new compounds by 1H NMR, IR, and elemental analysis. Conventional adhesive monomers, namely VBPA, 4-META, and 4-AETA, and CEBA-p-TSMo-t-BPMA initiator were also used. Seven experimental composite-type adhesive resins comprising these six kinds of adhesive monomers and None (control) with the initiator were prepared. Tensile bond strengths of adhesive resins to unetched ground enamel and dentin, ground porcelain, and sandblasted Ni-Cr alloy were measured at a crosshead speed of 1.0 mm/min. Results showed that except with VBPA, there were no significant differences among 6-MHPA, 6-AHPA, 10-MDPA, 4-AETA, and 4-META in bonding performance to the adherends (p<0.01). It was found that the new phosphonic acid monomers provided good multipurpose adhesion to all adherends tested.

Effect of solvent type on the degradation of 4-MET.

This study sought to investigate the degradation mechanism of 4-methacryloyloxy ethyl trimellitic acid, 4-MET, which is commonly used as an acidic monomer in solvated self-etching primers or one-step bonding agents. To this end, we examined the effects of solvent type used--such as ethanol, methanol, and acetone--on the degradation mechanism of 4-MET by using the 13C NMR technique. The degradation mechanism of 4-MET was strongly dependent on the type of solvent used. When an alcohol-based solution was used for 4-MET, the esterification of 1- or 2-carboxylic acid in 4-MET occurred. However, when an acetone solvent was used for 4-MET, the esterification reaction did not occur. Increases in the aging period of 4-MET solvated solutions resulted in the hydrolysis of the benzoyl ester portion in 4-MET. The 2-hydroxyethyl methacrylate, produced as a subproduct, also became hydrolyzed. In addition, methacrylic acid, non-esterified and esterified trimellitic acid, as well as ethylene glycol were produced as subproducts. In particular, the production of trimellitic acid and ethylene glycol affected the bonding efficacy and durability of the resin to the tooth created by self-etching primers or one-step bonding agents that contained the altered 4-MET.

NMR study on the adhesion efficacy of experimental phosphonic acid monomers.

Three experimental self-etching primers - consisting of N-methacryloyl-omega-aminoalkyl phosphonic acid (NMomegaP) with different methylene chain lengths and N-methacryloyl glycine (NMGly) - were formulated. The influence of methylene chain length in NMomegaP derivatives on the chemical nature of calcium salts was examined following their application to tooth components. Bond strengths of experimental self-etching primers created with these monomers to enamel and dentin were also investigated. Nuclear magnetic resonance spectroscopy showed that NMomegaPs decalcified tooth components with formation of calcium salts, which changed from calcium hydrogen phosphonate to calcium phosphonate with increase in methylene chain length within the NMomegaP structure. Disparity in calcium salt formation was related to increases in bond strength to enamel from 18 to 24 MPa. However, bond strength to dentin remained unchanged (22 MPa). The relative dependency of bond strength on monomer methylene chain length was probably attributable to the sites where these NMomegaP calcium salts had deposited on the bonding substrates.

Fabrication and physical properties of glass-fiber-reinforced thermoplastics for non-metal-clasp dentures.

Recently, non-metal-clasp dentures (NMCDs) made from thermoplastic resins such as polyamide, polyester, polycarbonate, and polypropylene have been used as removable partial dentures (RPDs). However, the use of such RPDs can seriously affect various tissues because of their low rigidity. In this study, we fabricated high-rigidity glass-fiber-reinforced thermoplastics (GFRTPs) for use in RPDs, and examined their physical properties such as apparent density, dynamic hardness, and flexural properties. GFRTPs made from E-glass fibers and polypropylene were fabricated using an injection-molding. The effects of the fiber content on the GFRTP properties were examined using glass-fiber contents of 0, 5, 10, 20, 30, 40, and 50 mass%. Commercially available denture base materials and NMCD materials were used as controls. The experimental densities of GFRTPs with various fiber contents agreed with the theoretical densities. Dynamic micro-indentation tests confirmed that the fiber content does not affect the GFRTP surface properties such as dynamic hardness and elastic modulus, because most of the reinforcing glass fibers are embedded in the polypropylene. The flexural strength increased from 55.8 to 217.6 MPa with increasing glass-fiber content from 0 to 50 mass%. The flexural modulus increased from 1.75 to 7.42 GPa with increasing glass-fiber content from 0 to 50 mass%, that is, the flexural strength and modulus of GFRTP with a fiber content of 50 mass% were 3.9 and 4.2 times, respectively, those of unreinforced polypropylene. These results suggest that fiber reinforcement has beneficial effects, and GFRTPs can be used in NMCDs because their physical properties are better than those of controls. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2254-2260, 2017.

Effect of fiber content on flexural properties of glass fiber-reinforced polyamide-6 prepared by injection molding.

The use of non-metal clasp denture (NMCD) materials may seriously affect the remaining tissues because of the low rigidity of NMCD materials such as polyamides. The purpose of this study was to develop a high-rigidity glass fiber-reinforced thermoplastic (GFRTP) composed of E-glass fiber and polyamide-6 for NMCDs using an injection molding. The reinforcing effects of fiber on the flexural properties of GFRTPs were investigated using glass fiber content ranging from 0 to 50 mass%. Three-point bending tests indicated that the flexural strength and elastic modulus of a GFRTP with a fiber content of 50 mass% were 5.4 and 4.7 times higher than those of unreinforced polyamide-6, respectively. The result showed that the physical characteristics of GFRTPs were greatly improved by increasing the fiber content, and the beneficial effects of fiber reinforcement were evident. The findings suggest that the injection-molded GFRTPs are adaptable to NMCDs because of their excellent mechanical properties.

Zirconia surface modification by a novel zirconia bonding system and its adhesion mechanism.

OBJECTIVE: Bonding to zirconia has been of great interest over the last 10-15 years. The aim of this study was to develop a zirconia bonding system and clarify its adhesion mechanism. METHODS: A zirconia primer was prepared using tetra-n-propoxy zirconium (TPZr) and water. A silane primer was also prepared using γ-methacryloyloxypropyltrimethoxysilane (γ-MPS) and hydrochloric acid. After the zirconia primer was applied to the oxidized zirconia surface, the silane primer was applied to the ZrO2-functionalized layer and the resin cement was applied to the silane-modified layer. Ceramic Primer II was used as a typical MDP-based ceramic primer. Shear bond strengths were measured using a universal testing machine. To clarify the enhancing mechanism of the zirconia bonding system, X-ray photoelectron spectroscopy (XPS) analyses were performed. RESULTS: The zirconia bond strength was affected by the surface wettability of zirconia, and the compositions of TPZr and water utilized in the zirconia primer. When the zirconia primer, consisting of 10µL TPZr and 13µL water, was applied to the zirconia surface that had been oxidized by H2O2 above 10%, the maximum bond strength of 8.2MPa was obtained. The mechanism of the zirconia bonding system was established as follows: the hydrolyzed zirconium species formed a more reactive ZrO2-functionalized layer on the oxidized zirconia surface, and the hydrolyzed γ-MPS species adsorbed on that layer introduces a chemical bonding to the resin. SIGNIFICANCE: The novel zirconia bonding system enhanced the bonding performance of the resin, and showed a greater bond strength than an MDP-based ceramic primer.