Physicochemical properties of apatites are affected dramatically by the substitution of trace elements. Especially, biological apatites constituting bone and teeth contain several wt% of CO32– ions, which are related to the crystallinity and solubility. Recently, scaffold biomaterials are being developed with a shape-maintaining property in addition to large pores and high porosity, into which cells can easily invade. To develop a new biodegradable scaffold biomaterial, bone-like carbonate apatites (CO3Ap) were synthesized and CO3Ap-collagen scaffolds were created. This scaffold biomaterial is useful for regions with bone regeneration ability. When these sponge-frame complexes with rh-BMP2 were implanted beneath the periosteum cranii of rats, sufficient new bone was created at the surface of the periosteum cranii after 4 weeks’ implantation. Furthermore, when a CO3Ap-collagen sponge containing SVVYGLR peptide was implanted as a graft into a tissue defect created in rat tibia, the migration of numerous vascular endothelial cells, as well as prominent angiogenesis inside the graft, could be detected after 1 week. Thus, the modification of higher functions such as cytokine and angiogenesis factors is effective for low regeneration regions using tissue engineering biomaterials.
Changes in the translucency, fluorescence, and opalescence of experimental 10–50% 2-hydroxyethyl methacrylate (HEMA)-added glass ionomers (HAGIs) after 5,000 cycles of thermocycling were determined and compared with those of commercial resin-modified glass ionomers (RMGIs). Changes in the translucency (TP), fluorescence (FL), and opalescence (OP) parameters were in the range of –3.5 to 0.2, –2.3 to 0.3 and –2.6 to 9.1 units respectively for HAGIs; and –0.9 to 0.3, –0.7 to 0.6, and 1.1 to 2.3 units respectively for RMGIs. Changes in the TP, FL, and OP of HAGIs were influenced by the HEMA content and powder shade, and were generally larger than those of RMGIs. Since the changes in TP, FL, and OP of experimental HAGIs were influenced by the HEMA content, there arises a need to determine the optimal HEMA ratio to attain high stability for these optical properties. In addition, results of this study showed that apart from optimal HEMA ratio, future studies should include other aspects and factors that contribute to age-dependent changes in optical properties.
In this study, morphological shape, elemental distribution and elution properties of Ca, P, Mg in four types of calcium phosphate powder were investigated using SEM, EPMA and ICP-AES. Calcium phosphate powder: OHAp, DCPD, β-TCP and OCP were observed in the white powder form and in the photopolymerized adhesive monomer they scattered like dispersed fillers in resin composite. In elemental analysis, CaKα showed a relatively high concentration in relation to PKα. In elution analysis, each calcium phosphate showed different elution of Ca and P. But Mg was almost equal to the detection limit of ICP-AES. Namely it was suggested that reparative dentin formation was effectively promoted under the following conditions: a calcification promoting effect by direct contact of the calcium phosphate powder, an ionic effect of Ca and P eluted from the powder located in the vicinity of the exposed pulp and environmental pH change of the surface in exposed pulp.
The purpose of this study was to evaluate the effect of primers on bonding between a silver-palladium-copper-gold alloy and an indirect composite material. Cast disks were air-abraded with alumina, conditioned with one of five primers (Alloy Primer, Luna-Wing Primer, Metal Primer II, Metaltite, M.L. Primer), and bonded with a light-activated indirect composite. Shear bond strengths were determined after 20,000 times of thermocycling. The results showed that four of the primers, except the Luna-Wing Primer, were effective in enhancing the bond strength as compared with the unprimed control group. Of these four primers, Alloy Primer, Metal Primer II, and M.L. Primer exhibited significantly greater bond strengths. It can be concluded that the effectiveness of primers varies considerably according to the organic sulfur compounds added to the solvent, and that care must be taken in selecting priming agents for bonding the composite material and the silver-palladium-copper-gold alloy.
The purpose of the present study was to test the hypothesis that glazing will affect the Weibull modulus or the mean flexural strength of dental porcelain. Four groups (n = 30) of specimens were prepared from feldspathic body porcelain (Vita VMK 68). The specimens were tested in groups: original glazed condition (control), and after grinding separately with 1,000-grit, 600-grit, and 100-grit silicon carbide abrasive. A three-point flexure test was undertaken for each specimen. The flexural strength of porcelain and the Weibull modulus were then obtained using a computer program and load-to-failure data. Flexural strength decreased as surface roughness increased, and the differences were significant (p < 0.05), as determined by Tukey’s multiple range test, except between the 600-grit group and the 100-grit group. The Weibull modulus of the glazed group was the largest (16.3), and the surface roughness was found to influence the Weibull modulus.
The aim of this study was to investigate and compare the radio-opacity of core materials for all-ceramic restorations, such as zirconia (NANOZR and Y-TZP) and alumina, against commercially pure titanium (cpTi) and aluminum. X-ray images were taken under general settings using an X-ray film. The X-ray film images were scanned using a digital scanner, and the darkness at the central area of each specimen image was quantitatively analyzed using an image analysis software. Amongst the materials investigated, alumina showed the most transparency against X-rays. Conversely, both types of zirconia showed the highest radio-opacity, whereby that of NANOZR was slightly lower than that of Y-TZP. This was because NANOZR contained 30 vol% of alumina and its density was also slightly lower than that of Y-TZP.
The aim of this study was to evaluate the effects of thermocycling on the degree of cure (DC) and water sorption behavior of two lingual retainer composites. A total of 50 composite specimens, 5 mm diameter and 2 mm height, were prepared using Light Cure Retainer® (LCR) (Reliance) and Transbond Lingual Retainer® (TLR) (3M Unitek). After 40-second curing with a halogen light and after 24-hour water storage, the composite specimens were subjected to different thermocycling regimes. Absorbance peaks to monitor the DC were recorded using Fourier transform infrared (FTIR) spectroscopy, while water sorption was calculated in μg/mm3. On DC, significant differences among the different thermocycling regimes were observed only for the TLR specimens (p<0.05). On water sorption behavior, an increase in the number of thermal cycles resulted in increased water sorption for both composites, but the statistical differences in these groups were not significant. On the effect of thermocycling up to 20,000 cycles, present findings showed that LCR was less affected than TLR. Further, LCR exhibited higher DC and lower water sorption values than TLR after thermal cycling.
The aim of this study was to compare the effects of antioxidant treatment and delayed bonding, following intra-coronal bleaching, on the shear bond strength (SBS) and bond failure site of brackets bonded to enamel. Eighty mandibular incisors were divided into four equal groups. After root canal filling, specimens in Group 1 were used as control and not bleached. For experimental groups 2 to 4, bleaching agent was placed into the rest of the cavity for a four-day period and this bleaching treatment was performed two times. In Group 2, specimens were bonded immediately after bleaching; in Group 3, specimens were bleached and then immersed in artificial saliva for 30 days before bonding; in Group 4, specimens were bleached, treated with an antioxidant agent, and then bonded. The SBS values of bonded brackets were measured in megapascal (MPa), while adhesive remnant index (ARI) scores were determined after the brackets failed. The SBS values of Group 1 (mean: 20.3±7.1 MPa) and Group 4 (mean: 18.2±6.1 MPa) were significantly higher (p>0.001) than those of Group 2 (mean: 4.9±3.2 MPa) and Group 3 (mean: 8.7±4.9 MPa). No significant differences in SBS were found between Groups 1 and 4, and between Groups 2 and 3.
This study investigated the corrosion properties of ion implanted nickel-titanium wire (Neo Sentalloy Ionguard) in artificial saliva and fluoride mouth rinse solutions (Butler F Mouthrinse, Ora-Bliss). Non ion implanted nickel-titanium wire (Neo Sentalloy) was used as control. The anodic corrosion behavior was examined by potentiodynamic polarization measurement. The surfaces of the specimens were examined with SEM. The elemental depth profiles were characterized by XPS. Neo Sentalloy Ionguard in artificial saliva and Butler F Mouthrinse (500 ppm) had a lower current density than Neo Sentalloy. In addition, breakdown potential of Neo Sentalloy Ionguard in Ora-Bliss (900 ppm) was much higher than that of Neo Sentalloy although both wires had similar corrosion potential in Ora-Bliss (450 and 900 ppm). The XPS results for Neo Sentalloy Ionguard suggested that the layers consisted of TiO2 and TiN were present on the surface and the layers may improve the corrosion properties.
To examine the effects from the chemical structure of acidic methacrylate monomers on the primer’s shelf life, N-methacryloyl-2aminoethylphosphonic acid (NMEP)- N-methacryloyl glycine (NMGly), 2-methacryloyloxyethyl dihydrogen phosphate (MEP)-NMGly and 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-NMGly primers were designed. Immediately after preparation, these primers were stored at 40°C for 0, 6 and 14 weeks. At the end of each storage period, 13C NMR observations were performed. Shear bond strengths of resin to dentin, conditioned by non-stored or stored primers, were measured. Alteration rates of these primers were strongly dependent on the chemical structure of acidic methacrylate monomers. The NMEP-NMGly primer exhibited noticeably higher hydrolytic stability and greater bond strength stability than MEP-NMGly and MDP-NMGly primers. These results demonstrated that methacryl amide monomers, NMEP and NMGly, are more advantageous than methacryl ester monomers. To develop self-etching primers with longer shelf life, it is essential to utilize acidic and hydrophilic methacryl amide monomers.
Three-dimensional computer models of dental arches play a significant role in prosthetic dentistry. The microfocus X-ray CT scanner has the advantage of capturing precise 3D shapes of deep fossa, and we propose a new method of measuring the three-dimensional morphology of a dental impression directly, which will eliminate the conversion process to dental casts. Measurement precision and accuracy were evaluated using a standard gage comprised of steel balls which simulate the dental arch. Measurement accuracy, standard deviation of distance distribution of superimposed models, was determined as ±0.050 mm in comparison with a CAD model. Impressions and casts of an actual dental arch were scanned by microfocus X-ray CT and three-dimensional models were compared. The impression model had finer morphology, especially around the cervical margins of teeth. Within the limitations of the current study, direct three-dimensional impression modeling was successfully demonstrated using microfocus X-ray CT.
We evaluated the effects of high-dose major components in oral disinfectants on oral cells from the standpoints of the cell cycle and apoptosis. We examined the viability and cell cycle of human gingival fibroblasts (HGFs) treated with the components of dental disinfectants, benzethonium chloride (BEC), benzalkonium chloride (BAC), and povidone iodine (PVD-I) using a cell counting kit and flow cytometry. The IC50 inhibitory concentration value in HGF cultures at 24 hours was 1.3×10–2 mM BEC, 6.0×10–3 mM BAC, and 2.6×10–1 mM PVD-I. In the cell cycle analysis, propidium iodide-stained HGFs were arrested in G0/G1 of the cell cycle by all three disinfectants, and in the apoptosis assay, annexin V-FITC/PI-stained HGFs that became apoptotic at 5.0×10–2 and 1.0×10–1 mM BEC and 5.0×10–2 and 1.0×10–1 mM BAC, but not in PVD-I at concentrations as high as 5.0×10–1 mM. Our findings describe the effects of high-dose oral disinfectants, rather than clinical concentrations. Nevertheless, appreciating the effects of high-dose disinfectants absorbed into the human body is important, where they may accumulate in specific tissues and cells.
The shear bond strength of a veneering composite (Solidex) and silver-palladium-copper-gold alloy (Castwell M.C.12) was evaluated for different duration times and irradiance for preliminary photo-polymerization. A veneering composite was applied onto a cast disk. Preliminary photo irradiation was performed using different duration times or irradiance. After final polymerization, the bond strength and the spectral distribution of each curing unit were determined. Shear bond strength was significantly higher for 90 s (12.4 MPa), than that for 0 s (8.3 MPa). With regard to the effect of irradiance, that from Solidilite (11.4 MPa) was significantly higher than that from Sublite S at 3 cm (8.7 MPa). The irradiance of Hyper LII and Sublite S at 3 cm was higher than Sublite S at 15 cm or Solidilite unit. Long time irradiation and low intensity is effective for preliminary irradiation in order to enhance the bond strength.
We examined the light transmittance characteristics and refractive indices of light-activated pit and fissure sealants. Five commercial pit and fissure sealants and human enamel were studied, along with the CIE L*a*b* color values of the materials and enamel. The light transmittance spectra of the pit and fissure sealants showed a similar trend to the enamel, especially at wavelengths below 530 nm. The average light transmittance values from 400 to 500 nm of the materials at 0.5-mm-thick ranged from 10.0% to 40.4%. The refractive indices at 589.3 nm ranged from 1.504 to 1.546, and were approximately 4−8% lower than that of enamel. The measurements for the surface hardness of materials indicate that the light-attenuating effect of enamel and the material itself reduced the polymerization efficiency of the material. For all materials, chromatic a* showed negative and b* showed positive values, as did enamel. Significant differences in light transmittance characteristics and refractive indices between the materials and enamel may affect color matching between them.
The purpose of this study was to determine whether the brushing durability of a titanium dioxide coating on a polymethyl methacrylate (PMMA) substrate was improved by prior treatment with an acryloxypropyl trimethoxysilane-based agent. Titanium dioxide coatings were obtained by spray-coating substrates with or without prior treatment. Structure was investigated using IR, SEM, and an EPMA. Effect on durability against brushing was determined with a brush-wear test machine utilizing a commercial denture brush. A thin layer comprised of siloxane and TiO2 was formed on a PMMA substrate by prior treatment with an acryloxypropyl trimethoxysilane-based agent and spray-coating of TiO2. Prior treatment demonstrated improved stability against brushing, whereas the titanium coating was removed after less than 1×105 brushing cycles without prior treatment. This suggests that prior treatment with an acryloxypropyl trimethoxysilane-based agent would confer improved durability against brushing-induced stress on a TiO2 coating in its application to dentures.