Several studies have investigated toughening porcelain that is layered over a frame or a core. The introduction of residual compressive stress to the surface of porcelain has been shown to be effective to strengthen it. In the present study, nanoparticles of precious metals of silver and platinum (rather than non-precious metals) were used to evaluate if they could increase the fracture resistance of porcelain. The addition of silver and platinum nanoparticles was found to improve the mechanical properties of porcelain since it increased both the Young's modulus and the fracture toughness of commercial porcelain.

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The aim of this study was to optimize the concentration of 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin^® TPO) in unfilled and filled composite resins in relation to the degree of conversion (DC). Increasing concentrations of Lucirin^® TPO between 0.05-4.97 wt% were added to equimolar mixtures of Bis-GMA/TEGDMA. Filled resins contained 75 wt% fillers. Standardized samples were cured using a polywave LED light-curing unit (bluephase^® G2, Ivoclar Vivadent). Increased initiator concentrations increased logarithmically the DC of unfilled and filled resins. The DC of unfilled resins was in the range of 73-91% at the top and 63-81% at the bottom surfaces and that of filled resins was in the range of 53-81% at the top and 47-70% at the bottom surfaces. The DC in unfilled and filled resins reached a plateau at 1.08 wt% and 1.50 wt% Lucirin^® TPO, respectively. Fillers significantly reduced conversion but had no effect on the logarithmic relationship between initiator concentration and the DC.

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This study aimed to develop a dental investment for titanium casting. ZrO₂ and Al₂O₃ were selected as refractory materials to prepare three investments (Codes: A-C) according to the quantity of Zr. Al₂O₃ cement was used as a binder at a ratio of 15%, they were mixed with special mixing liquid. B1 was used as a control mixed with water. Fundamental examinations were statistically evaluated. A casting test was performed with investment B. Fluidities, setting times, and green strengths showed no remarkable differences; however, they were significantly different from those of B1. Expansion values for A, B, C, and B1 at 850°C were 1.03%±0.08%, 1.96%±0.17%, 4.35%±0.23%, and 1.50%±0.28%, respectively. Castings were covered by only small amounts of mold materials. The hardness test showed no significant differences between castings from B and the ones from commercial investments. The experimental special mixing liquid effectively reduced the water/powder ratio and improved the strength and thermal expansion.

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The purpose of this study was to evaluate the effect of sports and energy drinks on the surface hardness of different restorative materials over a 6-month period. Forty-two disk-shaped specimens were prepared for each of the four restorative materials tested: Compoglass F, Filtek Z250, Filtek Supreme, and Premise. Specimens were immersed for 2 min daily, up to 6 months, in six storage solutions (n=7 per material for each solution): distilled water, Powerade, Gatorade, X-IR, Burn, and Red Bull. Surface hardness was measured at baseline, after 1 week, 1 month, and 6 months. Data were analyzed statistically using repeated measures ANOVA followed by the Bonferroni test for multiple comparisons (α=0.05). Surface hardness of the restorative materials was significantly affected by both immersion solution and immersion period (p<0.001). All tested solutions induced significant reduction in surface hardness of the restorative materials over a 6-month immersion period.

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The purpose of this study was to investigate the reinforcing effect of short E-glass fiber fillers oriented in different directions on composite resin under static and dynamic loading. Experimental short fiber-reinforced composite resin (FC) was prepared by mixing 22.5 wt% of short E-glass fibers, 22.5 wt% of resin, and 55 wt% of silane-treated silica fillers. Three groups of specimens (n=5) were tested: FC with isotropic fiber orientation, FC with anisotropic fiber orientation, and particulate-filled composite resin (PFC) as a control. Time-dependent creep and recovery were recorded. ANOVA revealed that after secondary curing in a vacuum oven and after storage in dry condition for 30 days, FC with isotropic fiber orientation (1.73%) exhibited significantly lower static creep value (p<0.05) than PFC (2.54%). For the different curing methods and storage conditions evaluated in this study, FC achieved acceptable static and dynamic creep values when compared to PFC.

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Simple chemical and thermal treatments were applied to prepare fluorinated porcine hydroxyapatite (FPHA). Morphology of FPHA was observed using SEM. Physiochemical characteristics, namely crystalline phase, chemical composition, functional groups, and binding energy of fluorine were investigated using XRD, EDX, FTIR, and XPS respectively. Concentration of free fluoride ion released from FPHA in HCl solution (pH 3.0-4.0) was detected using a fluoride ion concentration meter. SEM, XPS, XRD, and FTIR results confirmed the fluorination of porcine hydroxyapatite (PHA). Significant crystal morphological difference was observed between PHA and FPHA. Concentration of free fluoride ion released from FPHA increased with rising concentration of immersion solution and length of immersion period. Fluoride was successfully incorporated into PHA by chemical and thermal processes in this study. Fluoride incorporation rate into PHA was a strong function of the fluorine concentration in the immersion solution.

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The purpose of this study was to evaluate the influence of air-abrasion and subsequent heat treatment on the shear bond strength of the bond between indirect composites and a zirconia material. Four surface preparations were employed; ground flat, then heated to regenerate the crystal phase (C); air-abraded with alumina for 10 s (S10), for 20 s (S20), and air-abraded for 10 s and heated (H). Disks were primed with Alloy Primer and bonded either with Estenia or with Gradia composite. XRD analysis suggested that the monoclinic zirconia content was increased by air-abrasion, and decreased by heating. The surface roughness of S10, S20 and H disks was similar. Nevertheless, H groups showed lower bond strengths than the S10 and S20 groups both before and after thermal cycling. Although alumina air-abrasion considerably enhanced bonding between zirconia and indirect composites, subsequent heat treatment had a negative effect on the durability of bond strength.

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This study evaluated the effect of different amounts of dentin powder (DP) mixed in Clearfil SE Bond (CSB) or Single Bond (SB) on adhesion to dentin. Human third molars (n=96) were sectioned to expose the mid-coronal dentin and divided into eight experimental groups (n=12 per group), namely, Group 1: CSB, Group 2: CSB+1.5 mg DP, Group 3: CSB+3 mg DP, Group 4: CSB+4.5 mg DP, Group 5: SB, Group 6: SB+1.5 mg DP, Group 7: SB+3 mg DP, and Group 8: SB+4.5 mg DP. Filtek Z250 composite was bonded onto dentin, and all specimens were subjected to shear bond strength test at a crosshead speed of 1 mm/min. Highest bond strength was obtained in Groups 1, 2, and 3 (15.1, 13.5, and 16.4 MPa respectively; p>0.05) and the lowest in Groups 6, 7, and 8 (5.5, 5.6, 4 MPa; p>0.05). DP addition, regardless of amount, adversely affected the bond strength of SB. Bond strength of CSB was not affected when 1.5 or 3 mg of DP was added.

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This study aimed to examine the shear bond strength between cobalt chromium alloy and autopolymerizing acrylic resin using experimental primers containing 5, 10, and 15 wt% of 4-methacryloxyethyl trimellitic anhydride or 1, 2, and 3 wt% of 3-methacryloxypropyl-trimethoxysilane comparison to 5 commercial primers (ML primers, Alloy primer, Metal/Zirconia primer, Monobond S, and Monobond plus). Sixty alloy specimens were sandblasted and treated with each primer before bonded with an acrylic resin. The control group was not primed. The shear bond strengths were tested and statistically compared. Specimens treated with commercial primers significantly increased the shear bond strength of acrylic resin to cobalt chromium alloy (p<0.05). The highest shear bond strength was found in the Alloy primer group. Among experimental group, using 10 wt% of 4-methacryloxyethyl trimellitic anhydride -or 2 wt% of 3-methacryloxypropyltrimethoxysilane enhanced highest shear bond strength. The experimental and commercial primers in this study all improved bonding of acrylic resin to cobalt chromium alloy.

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This study aimed to investigate the in vitro biological response of human dental pulp cells to glass ionomer cement (GIC, Fuji IX GP^®) containing 2.5% magnesium carbonate apatite (MgCO₃Ap). MgCO₃Ap was synthesized by wet method and characterized using FT-IR, XPS, and SEM. Fuji IX GP^® served as a control. Test and control cements were prepared by encapsulated mixing the powder with Fuji IX-liquid (P/L=3.6:1). Eluates from cements extracted by 1 mL culture medium were collected at day 1, 7 and 14, and used for WST-1 proliferation assay. For ALPase activity, cells were maintained with cements in transwells, harvested and enzyme activity was measured at day 1, 4, 7, 14, and 21. We found a higher cell proliferation and increased ALPase activity by pulp cells in the test group compared to the control. This suggests the potential of GIC containing this novel biological apatite as a restorative material for pulp-dentin regeneration.

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This study measured the immediate and 24 h shear (SBS) and micro-shear bond strengths (MSBS) to dentin of four self-etching adhesives. A resin composite was bonded using each adhesive to the area of 5-mm diameter for SBS test or 0.75-mm diameter for MSBS test of flat bovine dentin. The bond strengths of all adhesives at 10 min were lower than at 24 h for both tests. The mean SBS (MPa, 10 min, 24 h) were similar in ranking order at both time periods that is: Clearfil SE Bond (21.2, 25.3) >Clearfil TriS Bond (12.7, 19.5)=i Bond (11.7, 19.5)=G Bond (11.1, 16.6). For the MSBS test, G Bond provided equivalent mean bond strength (35.0) to Clearfil SE Bond (36.9) and higher than the other adhesives at 24 h [i Bond (26.3), Clearfil TriS Bond (28.5)]. In conclusion, the MSBS test was slightly more discriminating than the SBS test.

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Porcelain veneering of zirconia is necessary, but chipping of the veneer may cause clinical problems. We investigated the effects of silica coating to improve the bond strength between porcelain veneers and zirconia-based ceramics. The ceramics tested were zirconia/alumina nanocomposites stabilized with ceria. Three surface treatments, grinding with a carborundum point (CA), sandblasting with alumina (SB), and Silano-Pen treatment (SP), were performed. Untreated specimens (NT) were examined as a control. The surface roughnesses and contact angles after treatment were measured. Shear bond tests were conducted, and the average strengths were calculated. EPMA was used for elemental identifications and surface observations. The bond strengths with SP were 20.00±3.43MPa and were significantly larger than that (15.35±3.12 MPa) of NT (p<0.05). However, differences among treated specimens were not significant. Moreover, SP gave superior wettability, and smoothness as good as NT. These data suggest that SP affects the bond strength between zirconia and a porcelain veneer.

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It is attempted to augment a coating resin with a bleaching effect to provide both short- and long-term whitening effects. Base resin containing sodium percarbonate (SPC) effectively bleached bovine teeth discolored by the Maillard reaction. SPC did not reduce Vickers hardness, but hardness in the hybrid material increased. The shear bonding strength of SPC-containing resin was low. No inflammation was apparent in hamster cheek pouch mucosa when exposed to SPC resin covered with a layer of base resin. H₂O₂ was released into buffer from this resin, but when placed onto tooth tissue with a protective layer of base resin, penetration of H₂O₂ into the pulp chamber was undetectable. It is concluded that SPC resin equipped with a bleaching aid can be safely used as a coating material for discolored teeth.

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The objectives of this study were to characterize change in surface properties of tetragonal zirconia polycrystals (TZP) after hydrophilic treatment, and to determine the effect of such changes on initial attachment of osteoblast-like cells. Roughened surfaces were produced by alumina-blasting and acid-etching. Hydrophilic treatment comprised application of immediately after blasting and acid-etching (Blast/Etch), oxygen plasma (O2-Plasma), ultraviolet light (UV). Specimens stored in air were used as a control. The water contact angle was determined and surface analysis was performed using an X-ray photoelectron spectroscopy. Blast/Etch, O2-Plasma and UV specimens showed superhydrophilicity, and these hydrophilic treatments to TZP elicited a marked decrease in carbon content and an increase in hydroxyl groups. Hydrophilic treatments enhanced initial attachment of osteoblast-like cells and a change in cell morphologies. These results indicate that Blast/Etch, O2-Plasma, or UV treatment has potential in the creation and maintenance of superhydrophilic surfaces and enhancing initial attachment of osteoblast-like cells.

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This study evaluated the feasibility of using three-dimensional printing (3DP) to fabricate porous titanium implants. Titanium powder was blended with a water-soluble binder material. Green, porous, titanium implants fabricated by 3DP were sintered under protective argon atmosphere at 1,200, 1,300, or 1,400°C. Sintered implant prototypes had uniform shrinkage and no obvious shape distortion after sintering. Evaluation of their mechanical properties revealed that titanium prototypes sintered at different temperatures had elastic modulus of 5.9-34.8 GPa, porosity of 41.06-65.01%, hardness of 115.2-182.8 VHN, and compressive strength of 81.3-218.6 MPa. There were significant differences in each type of these data among the different sintering temperatures (p<0.01). Results of this study confirmed the feasibility of fabricating porous titanium implants by 3DP: pore size and pore interconnectivity were conducive to bone cell ingrowth for implant stabilization, and the mechanical properties matched well with those of the human bone.

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Orthodontic appliances often cause oral diseases such as dental caries and gingivitis due to the attachment of an oral biofilm. However, there are few reliable methods to remove the biofilm from the orthodontic appliances. The aim of this study was to investigate the effects of microbubbled water on the removal of biofilms made with Streptococcus mutans or Candida albicans on orthodontic appliances. The orthodontic appliances with biofilm were immersed with microbubbled water and the remaining biofilm on the appliances was detected and measured using a micro-plate reader and an absorbance meter. The microbubbled water had a sufficient effect on the removal of biofilm from orthodontic appliances. The effects of microbubbled water were significantly higher than those of tap water (S. mutans: p<0.05, C. albicans: p<0.01). The results of this study suggest that microbubbled water is effective in the removal of biofilm from the mouth of orthodontic patients.

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The ability of staining slurries containing silver and/or potassium compounds to enhance the mechanical properties of a leucitereinforced glass ceramic (IPS Empress CAD) was investigated by measuring the Vickers hardness, median crack length, toughness, and compressive residual stress of specimens. A staining slurry containing potassium ions was found to increase the toughness of IPS specimens more than a staining slurry containing only silver ions when applied prior to sintering. None of the staining slurries produced any color changes. Thus, the results obtained in this study demonstrate that staining slurries increase the Vickers hardness and the fracture toughness of the surface and subsurface regions of all-ceramic IPS blocks fabricated by a CAD/CAM system without sacrificing their aesthetics.

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Porosities of set and burnout compacts of phosphate-bonded investments were determined. A gas pycnometer was used to measure the volumes, and hence the densities, of fine powders and porous compacts. Porosities of set and burnout compacts were then obtained from these data for as-received powders and dry set compacts by a numerical simulation method, subsequently leading on to the estimated compositions of conventional and rapid-heating investments used in this study. Excess water content in the hardening investment compact was evaluated as a function of setting time elapsed from the start of mixing. Porosities were about 24-32% for set compacts and 43% for burnout compacts, which well agreed with the numerically computed results. It was concluded that the functional composition of investment powder needed to achieve the optimal porosity as well as process parameters such as water-powder (W/P) ratio and keeping time of mixed investment casting slurry before heat treatment could be determined using the numerical simulation method developed in this study.

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This article has been retracted by the Editorial Board of Dental Materials Journal due to violation of our publishing policies and procedures as of December 1, 2013.

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An experimental conditioner (Exp), which was an aqueous solution of 10% ascorbic acid and 5% ferric chloride, was prepared in this study. This study evaluated the effect of Exp on the microtensile bond strength between a self-curing resin and dentin after long-term water immersion. Flat human dentin surfaces were sequentially pretreated with 40% phosphoric acid, 10% sodium hypochlorite, and Exp. Surface pretreatment with an aqueous solution of 10% citric and 3% ferric chloride (10-3) was used as a control. Composite resin rods were bonded to pretreated dentin surfaces using 4-META/MMA-TBB resin. Microtensile bond strengths were evaluated after water immersion at 24 h, 12 months, 24 months, and 36 months. At each immersion period, the bond strength of Exp was significantly higher than that of 10-3. After 36 months, Exp showed no significant decrease in microtensile bond strength, but 10-3 showed significant reductions. Pretreatment with experimental acid/base conditioner markedly improved the bonding durability of 4-META/MMA-TBB resin to human dentin when compared against the conventional 10-3 treatment.

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Magnetic fields can represent a health problem, especially low frequency electromagnetic fields sometimes induced by electric current in metallic objects worn or used in or on the body (as opposed to high frequency electromagnetic fields that produce heat). Electric toothbrushes are widely used because of their convenience, but the electric motors that power them may produce electromagnetic waves. In this study, we showed that electric toothbrushes generate low frequency (1-2000 Hz) magnetic fields and induce electric current in dental appliances (e. g. orthodontic and prosthetic appliances and dental implants). Current induced by electric toothbrushes might be dependent on the quantity and types of metals used, and the shape of the appliances. Furthermore, these induced currents in dental appliances could impact upon human oral health, producing pain and discomfort.

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This article has been retracted by the Editorial Board of Dental Materials Journal due to violation of our publishing policies and procedures as of December 1, 2013.

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Composite resins were reinforced with glass and polyethylene fibers in this study, and the effect of fiber reinforcement on the color change of composite resins was investigated. After accelerated aging, the effect of fiber reinforcement on the color stability of composite resins was also examined. There were three experimental groups (n=12 disks per group): non-fiber-reinforced composite (non-FRC control), polyethylene fiber (Ribbond-THM)-reinforced composite, and glass fiber (everstick NET)-reinforced composite. According to the critical remarks of color change of National Bureau of Standarts (NSB), glass fiber-reinforced anterior composites showed trace color change and polyethylene-fiber reinforced composites showed slight color change before accelerated aging. After accelerated aging, both control and fiber-reinforced composite groups showed noticeable color change. It was concluded that both the types of fiber reinforcement and composite resin influenced the color change of fiber-reinforced composite resins.

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The purpose of this study were to evaluate the discoloration of a silorane-based resin and two methacrylated-based resin composites upon exposure to different staining solutions coffee, red wine, porcine liver esterase and distilled water for 7 days. The colors of all specimens before and after storage in the solutions were measured by a spectrophotometer based on CIE Lab system, and the color differences thereby calculated. Data were statistically analyzed by ANOVA and Scheffe's test. For coffee and red wine, the mean color change in silorane-based resin was significantly lower than that in methacylate-based resin composites (p<0.05). For porcine liver esterase and distilled water, there was no significant difference in the mean values of color change between silorane- and methacrylate-based resin composites (p>0.05). In conclusion, the silorane-based resin composites exhibited better color stability (less ΔE) after exposure to the colored staining solutions.

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