Effects of sandblasting and electrical discharge machining on porcelain adherence to cast and machined commercially pure titanium

The aim of this study was to determine the effect of sandblasting and electrical discharge machining (EDM) on cast and machined titanium surfaces and titanium-porcelain adhesion. Twenty machined titanium specimens were prepared by manufacturer (groups 1 and 2). Thirty specimens were prepared with autopolymerizing acrylic resin. Twenty of these specimens (groups 3 and 4) were cast with commercially pure titanium and the alpha-case layer was removed. For control group (group 5), 10 specimens were cast by using NiCr alloy. Groups 2 and 4 were subjected to EDM while groups 1, 3, and 5 were subjected to sandblasting. Surface examinations were made by using a scanning electron microscope (SEM). A low-fusing porcelain was fused on the titanium surfaces, whereas NiCr specimens were covered using a conventional porcelain. Titanium-porcelain adhesion was characterized by a 3-point bending test. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests. Metal-porcelain interfaces were characterized by SEM. The bond strength of control group was higher than that of the titanium-porcelain system. There was no significant difference between cast and machined titanium groups (p > 0.05). There was no significant difference between EDM and sandblasting processes (p > 0.05). The use of EDM as surface treatment did not improve titanium-porcelain adhesion compared with sandblasting.     

氮化钛涂层和黏结瓷对钛瓷结合强度的影响

背景：氮化钛涂层与黏结瓷均可改善钛瓷结合强度。 目的：观察氮化钛涂层和Noritake Ti-22黏结瓷对钛瓷结合强度的影响。 方法：将32个纯钛铸件表面喷砂后分为4组：纯钛组、氮化钛涂层组、黏结瓷涂布组、氮化钛涂层联合黏结瓷涂布组。将处理后各组试件中间部分烤瓷,运用三点弯曲方法测试各组金瓷结合强度。 结果与结论：纯钛组钛瓷结合力低于氮化钛涂层组、黏结瓷涂布组、氮化钛涂层联合黏结瓷涂布组(P < 0.05),后3组组间结合强度差异无显著性意义(P > 0.05)。氮化钛涂层组、黏结瓷涂布组、氮化钛涂层联合黏结瓷涂布组钛瓷界面结合紧密,无明显孔隙和气泡;纯钛组钛瓷结合界面有明显孔隙。说明氮化钛涂层和黏结瓷的应用有利于提高钛瓷结合强度,单两种处理方法同时作用并不能更好地提高钛瓷结合强度。     

Titanium-porcelain system. Part III: effects of surface modification on bond strengths

During its development, titanium was found to be incompatible with conventional dental porcelains due to weak bond strength brought about by titanium's high yet oxidative nature. In spite of the development of new low-fusing porcelains designed for titanium application, previous studies have shown that sandblasting pre-treatment prior to porcelain application led to weakening of the metal-ceramic bonding. The aim of this study is to search for an effective alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system. The research evaluated the bond strength of 165 samples of titanium-porcelain systems divided into 11 groups. A three-point flexural bend test was conducted to measure the force required to fracture the porcelain on the titanium substrate. A correlation between the type of surface treatment and the bond strengths of each group was evaluated if it resulted to significant differences. The study found significantly differences in the energy-to-break of titanium-porcelain systems treated with hydrochloric acid and sandblasting compared with the control group. The bonds strength achieved by the titanium-porcelain system when treated with hydrochloric acid is comparable to that of conventional metal-ceramic alloy system. Hydrochloric acid treatment of the titanium substrate is a promising alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system.     

Bond strength of binary titanium alloys to porcelain

The purpose of this study was to investigate the bond strength between porcelain and experimental cast titanium alloys. Eleven binary titanium alloys were examined: Ti-Cr (15, 20, 25 wt%), Ti-Pd (15, 20, 25 wt%), Ti-Ag (10, 15, 20 wt%), and Ti-Cu (5, 10 wt%). As controls, the bond strengths for commercially pure titanium (KS-50, Kobelco, Japan) and a high noble gold alloy (KIK, Ishifuku, Japan) were also examined. Castings were made using a centrifugal casting unit (Ticast Super R, Selec Co., Japan). Commercial porcelain for titanium (TITAN, Noritake, Japan) was applied to cast specimens. The bond strengths were evaluated using a three-point bend test according to ISO 9693. Since the elastic modulus value is needed to evaluate the bond strength, the modulus was measured for each alloy using a three-point bend test. Results were analyzed using one-way ANOVA/S-N-K test (alpha = 0.05). Although the elastic moduli of the Ti-Pd alloys were significantly lower than those of other alloys (p = 0.0001), there was a significant difference in bond strength only between the Ti-25Pd and Ti-15Ag alloys (p = 0.009). The strengths determined for all the experimental alloys ranged from 29.4 to 37.2MPa, which are above the minimum value required by the ISO specification (25 MPa).     

Porcelain adherence to dental cast CP titanium: effects of surface modifications

OBJECTIVES: A reaction layer forms on cast titanium surfaces due to the reaction of the molten titanium with the investment material. Such a layer prevents strong adhesion between titanium and porcelain. This study characterized the effects of surface modifications on cast titanium surfaces and titanium-ceramic adhesion. METHODS: ASTM grade II CP titanium was cast into an MgO-based mold. Castings were devested by sandblasting with alumina particles, and subjected to surface modification by immersion in one of the following solutions: (1) 35% HNO3-5% HF at room temperature for 1min; (2) 50% NaOH-10% CuSO4 x 5H2O at 105 degreesC for 10min; (3) the NaOH-CuSO4 solution followed by the HNO3-HF solution; (4) 50% NaOH-10% NaSO4 at 105 degreesC for 10 min; (5) the NaOH-NaSO4 solution followed by the HNO3-HF solution; and (6) 50% NaOH solution at 105 degreesC for 10min. Surfaces only sandblasted with alumina were used as controls. Specimen surfaces were characterized by XRD and SEM/EDS, and hardness-depth profiles were determined. All specimens were sandblasted with 110 microm alumina particles before porcelain firing. An ultra-low-fusing porcelain (Vita Titankeramik) was fused on the titanium surfaces. The titanium-ceramic adhesion was characterized by a biaxial flexure test, and area fraction of adherent porcelain (AFAP) was determined by X-ray spectroscopy. RESULTS: EDS analyses revealed a substantial amount (13-17 wt%) of Al on the control, and specimens modified with Methods 2, 4, and 6. XRD revealed residual stress in the titanium surfaces and corundum on the control, and Methods 2, 4, and 6 specimens. A new Ti(Cu, Al)2 phase was identified on the titanium surfaces modified by immersion in 50% NaOH-10% CuSO4 x 5H2O aqueous solution. Reduced residual stress was observed on Method 1, 3, and 5 specimens. No corundum peaks were detected on these specimens. Compared to the control, significantly lower (P < 0.05) hardness values were found for Methods 1-3 and Method 5 specimens at 20 microm below the surfaces and for Method 1-5 specimens at 50 microm below the surfaces. Significantly higher (P < 0.05) AFAP values were found for surfaces modified with Methods 2-6 compared to the control and Method 1, and no significant differences were found among Methods 1-6, and between control and Method 1. SIGNIFICANCE: Based on the results from the present study, porcelain adherence to cast CP titanium can be improved by the caustic baths used in the study.     

SEM/EDS evaluation of porcelain adherence to gold-coated cast titanium

The adhesion between titanium and dental porcelain is related to the diffusion of oxygen to the reaction layer formed on cast-titanium surfaces during porcelain firing. The diffusion of oxygen could be suppressed by coating the titanium surface with a thin gold layer. This study characterized the effects of gold coating on titanium-ceramic adhesion. ASTM grade II CP titanium was cast into a MgO-based investment (Selevest CB, Selec). The specimen surfaces were air abraded with 110-microm Al(2)O(3) particles. Gold coating was applied on titanium surfaces by three methods: gold-paste (Deck Gold NF, Degussa-Ney) coating and firing at 800 degrees C for three times, single gold-paste coating and firing followed by sputter coating (40 mA, 500 s), and sputter coating (40 mA, 1000 s). Surfaces only air abraded with Al(2)O(3) particles were used as controls. An ultra-low-fusing dental porcelain (Vita Titankeramik, Vident) was fused on titanium surfaces. Specimen surfaces were characterized by SEM/EDS and XRD. The titanium-ceramic adhesion was evaluated by a biaxial flexure test (N = 8), and area fraction of adherent porcelain (AFAP) was determined by EDS. Numerical results were statistically analyzed by one-way ANOVA and the Student-Newman-Keuls test at alpha = 0.05. SEM fractography showed a substantial amount of porcelains remaining on the gold-sputter-coated titanium surfaces. A new Au(2)Ti phase was found on gold-coated titanium surface after the firing. Significantly higher (p <.05) AFAP values were determined for the gold-sputter-coated specimens compared to the others. No significant differences were found among the other groups and the control. Results suggested that gold coatings used in this study are not effective barriers to completely protect titanium from oxidation during the porcelain firing, and porcelain adherence to cast titanium can be improved by gold-sputter coating used in the present study.     

Corrosion behavior of cast titanium with reduced surface reaction layer made by a face-coating method

This study characterized the corrosion behavior of cast CP titanium made with a face-coating method. Wax patterns were coated with oxide slurry of Y(2)O(3) or ZrO(2) before investing with a MgO-based investment. Three surface preparations were tested: ground, sandblasted, and as-cast. Uncoated castings served as controls. Sixteen-hour open circuit potential (OCP) measurement, linear polarization and potentiodynamic cathodic polarization were performed in an aerated modified Tani-Zucchi synthetic saliva at 37 degrees C. Anodic polarization was conducted in the same deaerated medium. Polarization resistance (R(p)) and Tafel slopes were determined. Corrosion current density was calculated for each specimen. Results (n=4) were subjected to nonparametric statistical analysis (alpha=0.05). Cross sections of cast specimens were examined by optical microscopy. Energy dispersive spectroscopy (EDS) spot analysis was performed at various depths below the surface. The OCP stabilized within several hours for all the specimens. Apparent differences in anodic polarization behavior were observed among the different surfaces. A distinctive wide passive region followed by breakdown was seen on specimens with ground and sandblasted surfaces. There were no significant differences in the corrosion resistance among the control and the two face-coating groups for each group. The Mann-Whitney test showed significantly lower OCP and higher R(p) values for ground surfaces. The surface condition significantly affected the corrosion behavior more than the face coating methods. In most cases, specimens with as-cast surfaces exhibited the least corrosion resistance during the potentiodynamic anodic polarization.     

Removal of noncollagenous components affects dentin bonding

The structural integrity of fibrillar type I collagen is critical for effective dentin bonding. Since most noncollagenous matrix components in dentin are closely associated with collagen, we hypothesized that they may also contribute to dentin bonding. To test this hypothesis, bovine dentin was acid-etched, treated with chondroitinase ABC (C-ABC), endo-beta-galactosidase (Endo-beta), or trypsin. Controls were prepared in the same manner but without the enzymes. All control and experimental specimens were then bonded with One-Step. Bond strength data were analyzed by one-way ANOVA and Fisher's PLSD test (p < 0.05). When dentin was treated with C-ABC or trypsin, bond strengths significantly decreased for the rewetted groups (p < 0.05). The treatment with Endo-beta showed no effects on bond strengths (p > 0.05). When the treated dentin surfaces were observed under SEM, the C-ABC and trypsin treated groups revealed significant loss of collagen fibril architecture. The results indicate that chondroitin sulfate glycosaminoglycans and trypsin-digestible noncollagenous proteins play roles in maintaining the open dimensions of the collagen fibril scaffold, which is essential for optimal dentin bonding.     

An investigation of the shear bond strength of compomer restorative material to enamel and dentine

The aim of this study was to investigate the effect of one step adhesives on the shear bond strength of a compomer restorative material to both enamel and dentine. Human extracted teeth were used for the study. Ten samples were prepared for both enamel and dentine specimens for each of the five groups: Tooth, no etch, Prime and Bond NT (P+B NT); tooth, Non-Rinse Conditioner (NRC), P+B NT; tooth, NRC, Prime and Bond 2.1 (P+B 2.1); tooth, etch, P+B NT; tooth, etch, P+B 2.1. The specimens were subjected to bond testing. The shear bond strength was measured using an Inston 1193 testing machine using a cross head speed of 1 mm/minute. The specimens were tested to destruction. The results show that for the enamel specimens the highest bond strength was recorded for those specimens subjected to Etch, P+B 2.1 (22.1 MPa) and Etch P+B NT (20.0 MPa). The groups of specimens which did not undergo etching had very low bond strengths ranging from 11.4 MPa for NRC, P+B 2.1, 8.5 MPa for NRC P+B NT to 6.9 MPa for P+B NT. For the dentine specimens, for all of the groups, the shear bond strengths were low. Those groups subjected to etching produced the highest values of 7.9 MPa for NRC P+B 2.1 with the lowest value of 6.1 MPa for NRC P+B NT. These bond strengths were significantly lower than those achieved for bonding to enamel. Prime and Bond NT and Prime and Bond 2.1, used in conjunction with acid etching, produce satisfactory bond strengths of compomer restorative material to enamel. Bond strengths to dentine were low.     

Effect of elapsed time following bleaching on the shear bond strength of composite resin to enamel

The purpose of this study was to investigate the effect of post-treatment time on the shear bond strength of composite resin to enamel after bleaching with 10% carbamide peroxide (CP) and 35% hydrogen peroxide (HP) bleaching systems. One hundred and thirty-five flattened labial enamel surfaces obtained from human mandibular incisors were divided into two bleaching groups of 10% CP (n = 60) and 35% HP (n = 60) and a control group (n = 15). Specimens in the control group (group 1) were not bleached. Each bleaching group was then divided into four subgroups (n = 15). For both CP and HP groups, group 2 consisted of specimens bonded immediately after bleaching. In groups 3, 4, and 5, specimens were immersed in artificial saliva for 24 h, 1 week, or 2 weeks after bleaching, respectively. After the specimens were bonded with Clearfil SE Bond and Clearfil ST, they were tested in shear until failure. For both CP and HP groups, shear bond strength of composite resin to enamel that was bonded immediately after bleaching was significantly lower than that of unbleached enamel (p < 0.05). However, in CP group restored after 24 h, the bond strength returned to values close to those of nonbleached enamel (p > 0.05). It took 1 week to return to conditions that lead to control bond values for HP bleaching applications (p > 0.05). The results of this study proved that immediate bonding of composite to enamel bleached with 10% CP and 35% HP gels result in a significant decrease in shear bond strength. It is advisable that composite resin application onto bleached enamel surfaces should be delayed at least 24 h for 10% CP and 1 week for 35% HP.     

Bonding characteristics of newly developed all-in-one adhesives

This study evaluated the microtensile bond strength and the interfacial morphology of newer adhesives. The occlusal surfaces of extracted teeth were ground flat for random allocation to four equal groups. Resin composite was bonded to each surface using either Clearfil SE Bond [SEB], Clearfil Protect Bond [PB], G-Bond [GB], or an experimental adhesive, SSB-200 [SSB]. After storage for 24 h in water at 37 degrees C, they were sectioned into beams (cross-sectional area 1 mm(2)) for microtensile bond strength testing (muTBS) at a crosshead speed of 1 mm/min. The load at failure of each was recorded; the data were analyzed by one-way ANOVA and Games Howell tests. The surfaces of the fractured specimens were observed using SEM. For the ultra-morphology of the interface, the occlusal surfaces of four more teeth were prepared as before and a thin layer of flowable resin composite was bonded to each surface using one of the four adhesives.The mean muTBS ranged from 39.68 MPa (GB) to 64.97 MPa (SEB). There were no statistical differences between SEB and SSB, or between PB and GB (p > 0.05). The muTBS of SEB and SSB were significantly greater than that of PB and GB (p < 0.05). SEMs of the fractured surfaces revealed a mixed (cohesive/interfacial) failure. TEM examination highlighted differences in the hybrid layer; SEB had a thicker layer than the others. In conclusion, the newer all-in-one adhesives produced a thin hybrid layer but varied in their bond strengths. The 2-step self-etching adhesives do not necessarily produce higher bond strengths than that of the all-in-one systems.     

Electrochemical characterization of cast titanium alloys

A reaction layer forms on cast titanium alloy surfaces due to the reaction of the molten metal with the investment. This surface layer may affect the corrosion of the alloy in the oral environment. The objective of this study was to characterize the in vitro corrosion behavior of cast titanium alloys. ASTM Grade 2 CP titanium, Ti-6Al-4V, Ti-6Al-7Nb and Ti-13Nb-13Zr alloys were cast into a MgO-based investment. Experiments were performed on castings (N=4) with three surface conditions: (A) as-cast surface after sandblasting, (B) polished surface after removal of the reaction layer, and (C) sandblasted surface after removal of the reaction layer. Open-circuit potential (OCP) measurement, linear polarization, and potentiodynamic cathodic polarization were performed in aerated (air+10% CO(2)) modified Tani-Zucchi synthetic saliva at 37 degrees C. Potentiodynamic anodic polarization was subsequently conducted in the same medium deaerated with N(2)+10% CO(2) gas 2 h before and during the experiment. Polarization resistance (R(P)) and corrosion rate (I(CORR)) were calculated. Numerical results were subjected to nonparametric statistical analysis at alpha=0.05. The OCP stabilized for all the specimens after 6 x 10(4)s. Apparent differences in anodic polarization were observed among the different surfaces for all the metals. A passivation region followed by breakdown and repassivation were seen on specimens with surfaces A and C. An extensive passive region was observed on all the metals with surface B. The Kruskal-Wallis test showed no significant differences in OCP, R(p), I(CORR) or break down potential for each of the three surfaces among all the metals. The Mann-Whitney test showed significantly lower R(P) and higher I(CORR) values for surface C compared to the other surfaces. Results indicate that the surface condition has more effect on corrosion of these alloys than the surface reaction layer. Within the oxidation potential range of the oral cavity, all the metal/surface combinations examined showed excellent corrosion resistance.     

Titanium-porcelain system. Part IV: some mechanistic considerations on porcelain bond strengths

The titanium-porcelain system can be considered as a double-layered structure, comprising of at least titanium substrate and porcelain body including bonding agent. Stress distribution pattern of such a double-layered structure is not necessarily same as that of a single beam under the 3-point bending testing mode. Previously tested porcelain-fired commercially pure titanium samples (n = 285) were re-evaluated. All obtained data on bond strengths and bond toughness (energy-to-break) were re-grouped in terms of c/t ratio, where c is the distance from the maximum compressive side of the beam to the calculated neutral axis and t is the thickness of titanium substrate plate thickness. It was found that (1) when the double-layered structure falls in the c < t situation, both bond strength and bond toughness are in a lower zone, which is slightly lower than the cohesive tensile strength of the porcelain, (2) when the c > t situation (with relatively thick porcelain application) is established, both bond strength and toughness are in higher zone than the porcelain itself, and (3) there is a transition zone between the above.     

Bond strength of adhesively luted ceramic discs to different core materials

The purpose of this in vitro study was to compare the shear bond strengths of resin, glass-ionomer, and ceramic-based core materials to all ceramic discs. Five core materials (Core max, Sankin; Clearfil AP-X, Kuraray; Empress Cosmo, Ivoclar-Vivadent; Photocore, Kuraray; Dyract Extra, Dentsply) were prepared as discs 10 mm in diameter and 2 mm in height according to the manufacturer's instructions. Ten disc specimens per group were prepared, and dentin served as the control. All resin specimens were embedded in autopolymerizing acrylic resin, with one surface facing up. All ceramic discs (IPS Empress I, Ivoclar-Vivadent) 3 mm in diameter and 2 mm in height were prepared and bonded to core specimens with a dual-curing luting resin cement (Variolink II, Vivadent). Specimens were stored in distilled water at 37 degrees C. Shear bond strength of each sample was measured after 24 h using a universal testing machine at a crosshead speed of 0.5 mm/min. The data were analyzed with one-way analysis of variance and Tukey HSD tests (alpha = 0.05). Shear bond strength varied significantly depending on the core material used (p < 0.05). Clearfil AP-X and Photocore showed the highest shear bond strength value while Empress Cosmo provided the lowest (p < 0.05). There were no statistically significant differences among Clearfil AP-X, Photocore, and Core-Max (p > 0.05). And also there were no statistically significant differences between Dyract Extra and the control group (p > 0.05). In vitro shear bond strengths of ceramic discs bonded to resin-based core materials showed higher bond strength values than ceramic-based core material.     

Impaction-modified densely sintered yttria-stabilized tetragonal zirconium dioxide: methodology, surface structure, and bond strength

The objectives of the study were to describe a novel method for producing zirconium dioxide specimens with a cementation surface that allows adhesive cementation techniques, to describe the surface structure and to evaluate the bond strength. Forty-eight pairs of specimens were fabricated and adhesively luted together. Three different surfaces were tested: impaction-modified surfaces created by using glass granules (G), impaction-modified surfaces created by using polymer granules (P) and a nonmodified control surface (C). Two bonding systems were used, Variolink(?)II (VA) or Panavia?F 2.0 (PA). During the different fabrication steps, the surfaces were examined under light microscope and analyzed with an optical interferometer. All groups were thermocycled and subjected to shear bond strength test. The groups with modified cementation surfaces showed significantly higher shear bond strength: 34.9 MPa (VA-G), 30.9 MPa (VA-P), 29.6 MPa (PA-P), and 26.1 MPa (PA-G) compared with the relevant control group: 20.5 MPa (VA-C) and 17.8 MPa (PA-C). The groups with surface modification showed a rougher surface structure and significantly fewer fractures between the cement and the zirconium dioxide surfaces compared to the control groups where all failures were adhesive. Impaction modification with an impaction medium pressed into the cementation surface of zirconium dioxide-based reconstructions can be used in combination with an additive production technique to increase bond strength. Both modification techniques described in the study result in a rougher surface structure and higher shear bond strength compared to the control groups.     

Cement bond strengths of titanium plates

The success of the oral rehabilitation of implant patients depends not only on the osseointegration of implant fixtures but also on maintaining the integrity of the connection of prosthetic superstructures to these fixtures. It was an objective of the present study to evaluate and compare cement bond strengths among rolled (R), cast (C) and metal-injection-molded (M) commercially pure titanium plates which were bonded with Panavia 21 (Kuraray) and Imperva (Shofu) cements. Two plates (15x5x1 mm) of each R, C, and M were lap-jointed (lap length: 5 mm). The joints were stored in 37 degrees C distilled water for 24 h, followed by tensile tests with an INSTRON system under 1 mm/min crosshead speed. It was found that the bond strength of R with Panavia 21 (PAN) was 5.31 (SD:1.5) MPa and 2.30 (0.83) MPa with Imperva (IMP) cement. These were improved by applying an alloy primer to 7.08 (1.31) MPa and 6.72 (1.63) MPa, respectively. Using PAN with primer application, C and M samples showed bond strengths of 7.99 (1.31) and 7.20 (2.50) MPa, while they were 5.83 (2.15) and 6.79 (2.09) MPa using IMP with primer. There was a significant difference (p<0.01) between PAN and IMP cements for C samples. Additionally, samples were pre-oxidized at 100 degrees C in air for 10 min. Bond strengths of PAN with the primer were 5.69 (2.25), 9.14 (1.28), and 5.60 (3.13) MPa for R, C, and M sample groups. If the cement with the primer was applied immediately after the polishing (instead of pre-oxidized surfaces), bond strengths were improved to 9.14 (1.78) for R, 9.29 (1.85) for C, and 9.36 (1.81) MPa for M sample group. At p<0.05 level, there was a significant difference between surface pre-condition of R and M, but no significance with C.     

Influence of contamination on bonding to zirconia ceramic

The purpose of this study was to investigate the influences of contaminations and cleaning methods on bonding to dental zirconia ceramic. After saliva immersion and using silicone disclosing agent, airborne-particle abraded ceramic specimens were cleaned with isopropanol (AL), acetone (AC), 37% phosphoric acid (PA), additional airborne-particle abrasion (AA), or only with water rinsing (SS). Airborne-particle abraded specimens without contaminations (CL) were used as control group. For chemical analysis specimens of all groups were examined with X-ray photoelectron spectroscopy (XPS). Plexiglas tubes filled with composite resin were bonded to ceramic specimens using a phosphate-monomer containing composite luting resin. After 3-day water storage, tensile bond strengths (TBS) were tested. XPS analysis of group SS showed the presence of saliva and silicone (Si) contamination on the surface. The ratios of carbon/zirconium and oxygen/zirconium for groups PA and AA were comparable to those ratios obtained for group CL, indicating the removal of the organic saliva contamination. Airborne-particle abrasion and acetone completely removed Si contamination from ceramic surfaces. Isopropanol had little cleaning effect on the two contaminants. TBS (median +/- standard deviation) in MPa of the groups SS (11.6 +/- 3.1), AL (10.0 +/- 2.9), and AC (13.0 +/- 2.8) were statistically lower than those of groups PA (33.6 +/- 5.5), AA (40.1 +/- 3.6), and CL (47.0 +/- 8.1) (p < 0.001), while no differences were found in TBS between groups AA and CL (p > 0.5). Contamination significantly reduced bond strengths to zirconia ceramic. Airborne-particle abrasion was the most effective cleaning method.     

Preparation of different forms of titanium oxide on titanium surface: effects on apatite deposition

Methods of preparing different types of titanium oxide (TiO(2)) and their effects on apatite deposition and adhesion on titanium surfaces were investigated. Forty-eight commercially pure titanium (Ti) discs were divided into four groups (12 per group) and each group was subjected to the following treatments: Group 1, heat treatment at 750 degrees C; Group 2, oxidation in H(2)O(2) solution followed by heat treatment; Group 3, dipping in rutile/gelatin slurry; and Group 4, dipping in anatase/gelatin slurry. Surface-treated Ti discs were immersed in a supersaturated calcium phosphate solution to allow apatite deposition. Results showed that the percentage of area covered by deposited apatite was highest in Group 4 compared to the other groups. Apatite deposited on Ti discs pretreated in H(2)O(2) solution (Group 2) demonstrated the highest adhesion to the titanium substrate. Results from this study indicated that surface treatment method affects the type of TiO(2) layer formed (anatase or rutile) and affects apatite deposition and adhesion on the Ti surface.     

Corrosion behavior of cast Ti-6Al-4V alloyed with Cu

It has recently been found that alloying with copper improved the inherently poor grindability and wear resistance of titanium. This study characterized the corrosion behavior of cast Ti-6Al-4V alloyed with copper. Alloys (0.9 or 3.5 mass % Cu) were cast with the use of a magnesia-based investment in a centrifugal casting machine. Three specimen surfaces were tested: ground, sandblasted, and as cast. Commercially pure titanium and Ti-6Al-4V served as controls. Open-circuit potential measurement, linear polarization, and potentiodynamic cathodic polarization were performed in aerated (air + 10% CO(2)) modified Tani-Zucchi synthetic saliva at 37 degrees C. Potentiodynamic anodic polarization was conducted in the same medium deaerated by N(2) + 10% CO(2). Polarization resistance (R(p)), Tafel slopes, and corrosion current density (I(corr)) were determined. A passive region occurred for the alloy specimens with ground and sandblasted surfaces, as for CP Ti. However, no passivation was observed on the as-cast alloys or on CP Ti. There were significant differences among all metals tested for R(p) and I(corr) and significantly higher R(p) and lower I(corr) values for CP Ti compared to Ti-6Al-4V or the alloys with Cu. Alloying up to 3.5 mass % Cu to Ti-6Al-4V did not change the corrosion behavior. Specimens with ground or sandblasted surfaces were superior to specimens with as-cast surfaces.     

Effect of temporary filling materials on repair bond strengths of composite resins

Endodontic access cavities sometimes can be prepared through a permanent composite restoration. Between the appointments, temporary cements are used to seal access cavities and may have negative effect on bonding of further composite restoration. The purpose of this study was to compare shear bond strength of composite to composite which had been in contact with various temporary filling materials. Standard cavities were prepared on 160 acrylic resin blocks, obturated with composite resin (Clearfil AP-X, Kuraray, Japan) and randomly divided into eight groups (n = 20). Group 1 received no treatment. From group 2-8, composite surfaces were covered with the following cements temporarily: Zinc-oxide/calcium-sulphate (Cavit-G, ESPE, Germany), two different Zinc-Oxide-Eugenol materials (ZnOE, Cavex, Holland and IRM, Dentsply, USA), Zinc-phosphate cement (Adhesor, Spofa-Dental, Germany), Zinc-polycarboxylate cement (Adhesor-Carbofine, Spofa-Dental, Germany), Glass-Ionomer-Cement (Argion-Molar, Voco, Germany), or light curing temporary material (Clip, Voco, Germany). The cements were removed mechanically after 1 week storage in distilled water at 37 degrees C and composite surfaces were treated with a self-etch adhesive system (SE-Bond, Kuraray, Japan). Composite resin build-ups were created on composite surfaces. Shear bond strength values were measured using universal testing machine at crosshead speed of 1 mm/min. The data was calculated in MPa and statistically analyzed using one-way ANOVA and Tukey tests. Eugenol-containing cements significantly reduced shear bond strengths of composite to composite (p < 0.05), while the other temporary materials had no adverse effect on shear bond strength (p > 0.05). These findings suggested that temporary filling materials except eugenol-containing materials have no negative effect on composite repair bond strengths.