Addition of Na2CO3 Improves the Shelf Life of Experimental 4-META Self-etch Primer.

PURPOSE: The objective of this study was to assess the influence of the addition of Na2CO3 on the shelf life and bond strength of 4-META self-etch primer. MATERIALS AND METHODS: Two 4-META self-etch primers were experimentally formulated with and without the addition of Na2CO3 (primer A and primer B, respectively). The primers were stored at 37°C for several periods of time after formulation. Clearfil SE Bond Primer (Kuraray Noritake Dental) was used as a control. A composite was bonded to bovine dentin using a combination of the primer and a bonding agent (Clearfil SE Bond), and the shear bond strengths were measured. Changes in the pH of the experimental primers were monitored and macroscopic observations were made as a function of the storage periods. RESULTS: With 0-day storage, the bond strength of primer A was equivalent to that of primer B and significantly lower than that of Clearfil SE Primer. The bond strengths of primer A were stable during 90-day storage; by contrast, the bond strengths of primer B significantly decreased during 7-day storage. primer A exhibited stable pH values during 180-day storage; primer B exhibited significantly lower pH than primer A with 0-day storage and discolored gelation during 7-day storage. CONCLUSION: By adding Na2CO3, the shelf life of the 4-META self-etch primer was obviously improved without significant deterioration in dentin bond strength. Adjusting the pH to around 4.5 was effective for obtaining sufficient bond strength and hydrolytic stability of the primer.

Residual stresses in glass crowns generated by polymerization and water sorption of resin cements.

This study investigated residual stresses in glass crowns cemented with resin cements. Glass caps were cemented to cylindrical cores using a conventional resin composite cement, a self-adhesive resin cement, or a methyl methacrylate (MMA)-based cement in dual-cure or self-cure mode. The cemented caps were stored in 37°C water for 28 days, and stresses on the cap surface were repeatedly measured. The water sorption, water solubility, and elastic modulus of the cements were also measured. Polymerization of the cements initially generated compressive stresses on the surfaces. Dual-curing or a greater modulus yielded greater initial stress. The stresses gradually decreased over time and lingered on the surfaces at 28 days with all the cements. Greater sorption tended to lead to greater stress reduction; however, the MMA-based cement exhibited less stress reduction despite exhibiting the greatest sorption. The use of a resin composite cement or dual-curing is recommended to reinforce crown restorations.

Adsorption behaviors of salivary pellicle proteins onto denture base metals using 27-MHz quartz crystal microbalance.

BACKGROUND: The adsorption of salivary pellicle proteins onto the material surface is key for denture plaque formation. OBJECTIVE: We aimed to investigate the adsorption of bovine serum albumin (BSA) and mucin (MCN) onto denture base metal materials using a 27-MHz quartz crystal microbalance (QCM) method. METHODS: A gold (Au), titanium (Ti), and cobalt chromium alloy (Co-Cr) sensors were employed for QCM measurements. Adsorbed amounts of BSA or MCN were calculated by observing the frequency decrease, and the apparent reaction rate, kobs, was obtained by the curve fitting of the frequency shift against the adsorption time. RESULTS: The adsorbed amounts of BSA on Ti were significantly lower than those on Au and Co-Cr. For MCN adsorption, Au showed significantly greater amounts of adsorption than Co-Cr. The kobs of Ti for BSA adsorption was significantly smaller than for the Co-Cr. The kobs of Ti, and Co-Cr for MCN adsorption were significantly smaller than for the Au. A clear correlation was not determined between adsorbed amounts of BSA or MCN onto each sensor and the surface topography or contact angles. CONCLUSIONS: The difference of denture base metals and the difference of salivary proteins influences the adsorption behavior of salivary proteins.

Color changes of dental zirconia immersed in food and beverage containing water-soluble/lipid-soluble pigments.

The present study examined color changes in the tooth-colored restorative materials, zirconia (3Y-TZP), resin composite, and porcelain. The colors (CIELab) of these materials were measured using a spectrophotometer. Specimens were immersed in black tea or curry for 1 and 7 days, after which colors were re-assessed. Color differences (∆E*ab) before and after immersion were calculated. Specimens after the 7-day immersion were ultrasonically cleaned, and colors were measured again to assess the color recovery rate. The surface free energy, roughness, and water sorption/solubility of each material were also evaluated. Specimens were observed under a scanning electron microscope. The ∆E*ab of 3Y-TZP was the smallest with both immersions. Resin composite had the smallest recovery rate. The surface free energy and roughness of 3Y-TZP were smaller than those of porcelain. 3Y-TZP and porcelain showed almost no sorption during the 7-day period. The present results revealed that 3Y-TZP exhibited the strongest resistance to discoloration.

Application of multi-directionally forged high-strength titanium to dental implants in beagle dogs.

Pure titanium is widely used as a material in dental implants. However, it possesses inferior mechanical strength. This study aimed to elucidate the efficacy of acid treated multi-directionally forged (MDF) pure titanium in vivo. We verified the temporal changes until osseointegration in beagle dogs. Using two types of experimental materials (conventional pure titanium or MDF pure titanium), new bone formation was assessed using morphological examinations, and the bone-to-implant contact (BIC) value was evaluated at each time point (14, 30, and 90 days after the operation). As such, new bone formation was observed around the acid-etched MDF group, in which the BIC value was highest, followed by that in the acid-etched pure titanium group. MDF pure titanium implants showed early promotion of new bone formation compared to conventional titanium implants. The new acid-treated MDF made of pure titanium could be applied to humans in the future to prove its practicality.

Fitness accuracy and retentive forces of milled titanium clasp.

Since cast titanium prostheses have many drawbacks, multi-directionally forged titanium grade 2 (MDF) was developed, and the application of the milling process was proposed for improving the titanium clasp. This in vitro study evaluated milled titanium clasps, including MDF titanium. Milling clasps were manufactured with commercially pure (CP) titanium grade 2 (CP 2), grade 4 (CP 4), Ti-6-Al-4V, and MDF. As a control, a CP 2 cast titanium clasp was fabricated in the conventional manner. No porosities and catastrophic failures were observed in the four milled titanium clasps. Fitness accuracy and retentive forces of milled CP 2 and CP 4 tended to be worse, and the milled MDF showed the higher retentive forces (12.45 N) than did cast and milled CP 2 clasps (9.32 N and 4.42 N). Milled titanium clasps can be recommended for longer-term clinical use as compared to cast clasps.

DNA/protamine complex paste for an injectable dental material.

A DNA/protamine complex powder was prepared by reaction between DNA and protamine sulfate solution with stirring in order to develop a new injectable biomaterials for dental therapy. The powder of DNA/protamine complex became paste by kneading the complex powder and distilled water. Complex formation was confirmed by FT-IR measurement. The complex paste had a porous structure and its viscosity was approximately 280.1 Pas. The paste could easily pass through a needle of 0.25 mm internal diameter. It seemed that DNA/protamine complex paste has suitable viscosity for clinical use as an injectable biomaterial. Although, the complex paste delayed the growth speed of Staphylococcus aureus, Pseudomonas aeruginosa, Porphyromonas gingivalis and Prevotella intermedia for limited periods, it cannot kill and inhibit growing bacteria. The complex paste disk showed a mild tissue response and gradually degraded after the implantation into the soft tissue of rats. These results suggested that this DNA/protamine complex paste could be a useful material for a biodegradable biomaterial. In particular, this paste will be applicable as an injectable biomaterial using syringe for the repair of defects of living tissue, GBR treatment and/or GTR treatment in dentistry.

Cellular responses of histatin-derived peptides immobilized titanium surface using a tresyl chloride-activated method.

Effects of histatin-derived peptides immobilization by tresyl chloride-activation technique for MC3T3-E1 cellular responses on titanium (Ti) were evaluated. MC3T3-E1 were cultured on sandblasted and acid-etched Ti disks immobilized with histatin-derived peptides, including histatin-1, JH8194, and mixed histatin-1 with JH8194. Surface topography and cellular morphology were examined using a scanning electron microscope. Elemental composition and conformational peptides on Ti surface were examined using energy dispersive X-ray and fourier transform infrared spectroscopy, respectively. Cellular adhesion, proliferation, osteogenesis-related genes, and alkaline phosphatase activity were evaluated. The results showed that peptides were successfully immobilized on Ti surface. Cell attachments on histatin-1 and mixed peptides coated groups are higher than control. Histatin-1 achieved the significantly highest cellular proliferation. Histatin-derived peptides improved the osteogenesis related-gene expression and alkaline phosphatase activity (p<0.05). This study suggested that histatin-1 immobilization by tresyl chloride-activation technique enhanced cellular responses and might be able to promote cellular activities around the dental implants.

Application of multi-directional forged titanium for prosthetic crown fabrication by CAD/CAM.

Titanium are often used as dental materials, pure titanium present low strength and titanium alloy is reported poor biocompatibility, respectively. To overcome the problem, we fabricated high-strength multi-directional forged (MDF) titanium with improved mechanical properties without changing the chemical composition and evaluated its applicability in prosthetic crowns. Cutting tests: the average absolute value of the difference before and after cutting was calculated as the uncut amount. Surface evaluations: MDF titanium, pure titanium, and the Ti-6Al-4V alloy were the surface properties (the surface roughness, the contact angles, glossiness) of the samples were evaluated. The fitness test used digital data. These demonstrated that the good workability of high-strength MDF titanium. The surface-roughness and contact-angle properties of MDF titanium and pure titanium were similar. The fitness test showed no significant differences between MDF titanium and pure titanium crowns. These results suggest that MDF titanium is promising for fabricating prosthetic crowns in dental applications.

Prevention of biofilm formation on titanium surfaces modified with conjugated molecules comprised of antimicrobial and titanium-binding peptides.

Specific binding of antimicrobial peptides to titanium (Ti) surfaces may serve to prevent biofilm formation, leading to a reduction in peri-implantitis. This study evaluated the binding behavior of conjugated molecules consisting of antimicrobial and hexapeptidic Ti-binding peptides (minTBP-1) using the quartz crystal microbalance (QCM-D) technique, and investigated the effect of modification of Ti surfaces with these peptides on the bioactivity of Porphyromonas gingivalis. Four kinds of peptide were prepared: histatin 5 (DSHAKRHHGYKRKFHEKHHSHRGY), minTBP-1 + histatin 5 (RKLPDAPDSHAKRHHGYKRKFHEKHHSHRGY), lactoferricin (FQWQRNMRKVR), and minTBP-1 + lactoferricin (RKLPDAPGGFQWQRNMRKVR). The QCM-D analysis demonstrated that significantly larger increases in peptide adsorption were observed in the conjugated peptides than in antimicrobial peptides alone. In addition, ATP activity in P. gingivalis in peptide-modified specimens significantly decreased compared to that in the Ti control. These results indicate that surface modification with conjugated molecules consisting of antimicrobial and Ti-binding peptides is a promising method for reduction of biofilm formation on Ti surfaces.

Use of the molecular precursor method to facilitate thin hydroxyapatite coating of titanium fiber web scaffold and enhance bone formation: an experimental study in rat cranial bone defects.

PURPOSE: This study evaluated the bone-regeneration properties of titanium fiber web (TW) that had been coated with a thin hydroxyapatite (HA) layer using the molecular precursor method. MATERIALS AND METHODS: TW disks with or without the thin HA coating were implanted into rat cranial bone defects. The rats were sacrificed after 3 or 6 weeks. New bone formation into the TW was evaluated. RESULTS: The porous structure of TW was clearly maintained after the HA coating was applied. In the HA-coated TW group, new woven bone was observed in the majority of the disks after 6 weeks, whereas the control (uncoated TW) group showed limited new bone formation in the interior. The bone formation ratio in the HA-coated group was significantly higher than in the control group (20.6% and 59.1% after 3 and 6 weeks, respectively, versus 2.0% and 15.5%, respectively; P < .05). CONCLUSIONS: The molecular precursor method of applying a thin HA coating to TW appeared to effectively enhance new bone formation through maintenance of TW porosity and promotion of osteoconductivity in the TW three-dimensional scaffold.

In vivo evaluation of composites of PLGA and apatite with two different levels of crystallinity.

The cortical bone response towards poly(lactide-co-glycolide) (70/30) (PLGA) (70/30)/apatite complex scaffolds with different levels of crystallinity was investigated. Apatite with different levels of crystallinity, Ca-deficient hydroxyapatite (CDHA), which has a low crystallinity, and a mixture of carbonated hydroxyapatite (CHA) and CDHA, which has a higher crystallinity, were prepared from an aqueous mixture of Ca-EDTA complex, H(2)O(2), H(3)PO(4), and NH(4)OH. Two porous PLGA(70/30)/apatite composite scaffolds, composite scaffold A (containing low crystallinity CDHA) and composite scaffold B (containing the higher crystallinity CHA/CDHA mixture), were prepared. Afterwards, pure porous PLGA and the two composite scaffolds were implanted into the cortical bone of rabbit tibiae for 12 weeks. High-resolution microfocus X-ray computed tomography and histological examinations revealed a better bone response for composite scaffold A compared with PLGA and composite scaffold B. For composite scaffold A, the original bone defect was almost filled with new bone. Quantitative analysis revealed that composite scaffold A produced a significantly greater amount of new bone. The present study demonstrated that the level of apatite crystallinity influences bone response. A PLGA/apatite porous composite with a low level of apatite crystallinity shows promise as a bone substitute or scaffold material for bone tissue engineering.

Molecular precursor method for thin carbonate-containing apatite coating on dental implants.

The molecular precursor method is an easy and simple method for coating thin carbonate-containing apatite (CA) films onto titanium surfaces. A molecular precursor solution containing ethanol, calcium-EDTA complex, and phosphate salt was dropped onto a titanium surface and then heated at 600°C for 2 h. An adherent thin CA coating was achieved. Animal implantation experiments showed that CA-coated implants had significantly higher bone-to-implant values than non-coated implants (p<0.05). The molecular precursor method was also used to coat three-dimensional titanium webs (TWs). Thin CA films could be coated inside the center area, as well as the surface of the TW, with excellent bone formation inside the CA-coated TW. Furthermore, the molecular precursor method was used to coat partially stabilized zirconia with CA. Better bone response was observed for CA-coated zirconia. From this, it is concluded that the molecular precursor method is useful for producing thin CA coatings on implant materials.

Bond strength and computational analysis for silane coupling treatments on the adhesion of resin block for CAD/CAM crowns.

The purposes of this study were to evaluate the shear bond strength and perform the computational analysis for silane coupling treatments on the adhesion between CAD/CAM composite resin and resin cement. As silane coupling agents, γ-methacryloyloxy propyltrimethoxysilane, 8-methacryloyloxyoctyl trimethoxysilane, and 3-methacryloyloxypropyl trichlorosilane were used. The shear bond strengths were influenced by the silane coupling agent used, its application method, and acid addition. There was no correlation between the contact angle and shear bond strengths. The steric energy difference between a silane coupling agent and its corresponding hydrolyzed trisilanol compound, ∆E, was calculated by the molecular mechanics method. There was a moderate or strong linear correlation between ∆E and shear bond strengths in treatment without acid addition and a weak correlation between them in treatment with acid addition. Computational analysis could suggest the different path of silane coupling treatments of CAD/CAM composite resin in the presence or absence of acid.

In vitro evaluation of a removable partial denture framework using multi-directionally forged titanium.

PURPOSE: This study evaluated the availability of multi-directionally forged (MDF) titanium (Ti) as a component of removable partial dentures (RPDs). MDF-Ti remarkably improved the mechanical properties of RPDs due to its ultrafine-grained structure. MATERIALS AND METHODS: The wear resistance, plaque adhesion, and machinability of MDF-Ti were tested. As controls, commercially pure (CP) titanium was used for wear, plaque adhesion, and machinability tests. For wear resistance, the volume losses of the titanium teeth before and after wear tests were evaluated. Plaque adhesion was evaluated by the assay of Streptococcus mutans. In the machinability test, samples were cut and ground by a steel fissure bur and carborundum (SiC) point. An unpaired t-test was employed for the analysis of the significant differences between MDF-Ti and the control in the results for each test. RESULTS: Wear resistance and plaque adherence of MDF-Ti similar to those of CP-Ti (P>.05) were indicated. MDF-Ti exhibited significantly larger volume loss than CP-Ti in all conditions except 100/30,000 g/rpm in machinability tests (P<.05). CONCLUSION: Although the wear resistance and plaque adherence of MDF-Ti were comparable to those of controls, MDF-Ti showed better machinability than did CP-Ti. MDF-Ti could be used as a framework material for RPDs.

In vitro antibacterial and cytotoxicity assessments of an orthodontic bonding agent containing benzalkonium chloride.

OBJECTIVE: To assess the antibacterial activity and cytotoxicity of an orthodontic bonding material containing an antibacterial agent. MATERIALS AND METHODS: Superbond C&B (4-methacryloxyethyl trimellitate anhydride/methyl methacrylate-tri-n-butyl borane [4-META/MMA-TBB]) resin was mixed with benzalkonium chloride (BAC) to obtain final BAC concentrations of 0.25%, 0.75%, 1.25%, 1.75%, 2.5%, and 5.0% (wt/ wt). Antibacterial activity against Streptococcus mutans and Streptococcus sobrinus was evaluated by soaking the BAC-resin in distilled water at 37 degrees C for periods of 30, 90, and 180 days. Antibacterial activity of the BAC-resin was measured by the disk diffusion method, and the inhibition zone around each sample was measured and recorded. For evaluation of cytotoxicity, BAC-resin samples were put into cell culture inserts placed above human gingival cells and were incubated at 37 degrees C for 1, 3, and 6 days. Cytotoxicity was assessed with a tetrazolium bromide reduction assay. RESULTS: The antibacterial activity of BAC-incorporated resin samples decreased significantly after immersion in water for 180 days, regardless of BAC concentration. The antibacterial activity of nonimmersed resin containing 0.25% or 1.75% BAC was comparable with that of 5.0% BAC-resin immersed for 180 days. In cytotoxicity tests, most cells died when exposed to resins containing 1.75%, 2.5%, and 5% BAC. No difference was observed between resins containing 0.25% and 0.75% BAC at 1, 3, and 6 days of culture. CONCLUSIONS: The addition of BAC to 4-META/MMA-TBB resin confers an antibacterial effect even after immersion in water, and 4-META/MMA-TBB resin containing 0.25% to 0.75% BAC has no significant cytotoxic effect.

Surrounding Tissue Response to Surface-Treated Zirconia Implants.

Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), which are partially stabilized zirconia, have been used for fabricating dental implants. This study investigated the soft tissue attachment, the collagen fiber orientation to zirconia at different surface conditions, and the bone response using implantation experiments in animals. The zirconia implant surfaces were treated with ultraviolet irradiation (UV), a combination of large-grit sandblasting and hydrofluoric acid etching (blastedHF), and a combination of blastedHF and UV (blastedHF+UV). The surface treated with blastedHF and blastedHF+UV appeared rough and hydrophilic. The surface treated with blastedHF+UV appeared to be superhydrophilic. Subsequently, tapered cylindrical zirconia implants were placed in the alveolar sockets of the maxillary molars of rats. The bone-to-implant contact ratio of blastedHF and blastedHF+UV implants was significantly higher than that of the non-treated controls and UV-treated implants. The four different surface-treated zirconia implants demonstrated tight soft tissue attachments. Perpendicularly oriented collagen fibers towards zirconia implants were more prominent in blastedHF and blastedHF+UV implants compared to the controls and UV-treated implants. The area of the soft tissue attachment was the greatest with the perpendicularly oriented collagen fibers of blastedHF+UV-treated implants. In conclusion, blastedHF+UV treatment could be beneficial for ensuring greater soft-tissue attachment for zirconia implants.

Evaluation of protein adsorption to diamond-like carbon (DLC) and fluorinedoped DLC films using the quartz crystal microbalance method.

The aim of the present study was to evaluate albumin adsorption to stainless steel (SUS), diamond-like carbon (DLC) and fluorinedoped DLC (F-DLC) films using the quartz crystal microbalance (QCM) method. Each sensor was characterized using atomic force microscopy, surface roughness and surface wettability measurements and surface free energy calculations. Adsorbed amounts of bovine serum albumin on DLC and F-DLC were significantly lower than that on SUS (p<0.05). The apparent first-order reaction rate, kobs, of F-DLC was significantly larger than those of SUS and DLC (p<0.05). Moreover, significantly lower total surface free energies of DLC and F-DLC influenced the albumin absorbed amounts and kobs. Furthermore, a clear correlation was found between the albumin absorbed amounts and the hydrogen bond component of the total surface free energy. Thus, DLC or F-DLC coating is effective for preventing protein adsorption on orthodontic appliances.

Electrochemical property and corrosion behavior of multi-directionally forged titanium in fluoride solution.

Multi-directional forging (MDFing) can improve the various properties of metals and alloys due to the evolution of an ultrafine-grained structure. In the present study, electrochemical properties and corrosion behaviors in a fluoride solution of MDFed pure titanium (MDF-Ti) were evaluated by comparing with conventional coarse-grained pure titanium (Ti). The Eopen value of MDF-Ti was significantly higher than that of Ti. However, similar potentiodynamic polarization profiles were obtained for Ti and MDF-Ti. Immersion in NaF solution caused no severe corrosion to Ti or MDF-Ti. However, immersion in acidulate phosphate fluoride solution (APF) revealed that MDF-Ti had better corrosion resistance than Ti at shorter time immersion periods and was more susceptible to corrosion for longer immersion. Significantly less release of titanium was observed for MDF-Ti in shorter immersion periods in APF. In conclusion, MDF-Ti showed similar electrochemical behaviors to Ti and less susceptible to corrosion in shorter time APF immersion.

Antimicrobial Activity of Protamine-Loaded Calcium Phosphates against Oral Bacteria.

Protamine is an antimicrobial peptide extracted from fish. In this study, we loaded protamine onto dicalcium phosphate anhydride (DCPA), a dental material. Protamine was loaded by stirring DCPA into a protamine solution. To explore the antimicrobial activity of the materials, we cultivated Streptococcus mutans on fabricated discs for 24 h. When S. mutans was cultivated on the discs under no sucrose conditions, the loaded protamine was not released, and the ratio of dead bacteria increased on the surface of P (125) DCPA (half of the saturated level of protamine (125 ppm protamine) was loaded). Aside from P (500) DCPA (saturated level of protamine was loaded), some protamine was released, and the number of planktonic bacteria in the supernatant decreased. Using medium containing 1% sucrose, the release of protamine was promoted from P (125) DCPA due to lowered pH. However, lowering of the pH decreased the antimicrobial activity of protamine. On the other hand, P (500) DCPA released protamine before the pH was lowered, and biofilm formation was inhibited. The loaded protamine expressed antimicrobial activity, both on the surface of the materials and in the surrounding environment. The interaction of loaded protamine with calcium phosphates could promote the application of protamine in the dental field.