OBJECTIVEThe aim of this study was to establish sol-gel technique of coating titanium on the surface of Ni-Cr alloy (PFM) in order to enhance corrosion resistance and reduce corrosive rate in oral cavity.

METHODSThe sol-gel technique included four steps: (1) pre-treatment; (2) preparation of sol; (3) coating; (4) heat treatment. Elements on the surface of Ni-Cr alloy were analyzed with X-ray photoelectron spectroscopy.

RESULTSAfter coating Ti, the surface of Ni-Cr alloy looked light golden without particles, blisters and fragments. Besides Ni and Cr, titanium was found on surface of Ni-Cr alloy after coating. With Ar(+) ion carving-corrosion figure, the thickness of titanium was about 20 - 80 microm.

CONCLUSIONWith sol-gel technique, titanium could be coated on the surface of Ni-Cr alloy.

Chromium Alloys ; chemistry ; Coated Materials, Biocompatible ; Dental Alloys ; chemistry ; Dental Materials ; Gels ; Humans ; Materials Testing ; methods ; Nickel ; chemistry ; Titanium ; chemistry

This paper is aimed to study the effect of notch's angle and depth on crack propagation of zirconia ceramics. We fabricated cuboid-shaped zirconia ceramics samples with the standard sizes of 4. 4 mm x 2. 2 mm x 18 mm for the experiments, divided the samples into 6 groups, and prepared notches on these samples with different angles and depth. We placed the samples with loads until they were broke, and observe the fracture curve of each sample. We then drew coordinates and described the points of the fracture curve under a microscope, and made curve fitting by the software-Origin. When the notch angle beta = 90 degrees, the crack propagation is pure type I; when beta = 60 degrees, the crack propagation is mainly type I; and when beta = 30 degrees, the crack propagation is a compound of type I and type III. With the increasing of the notch depth, the effect of notch angles on crack propagation increases. In addition, Notch angle is a very important fracture mechanics parameter for crack propagation of zirconia ceramics. With the increasing of notch depth, the impact of notch angle increases.
Ceramics ; chemistry ; Dental Implants ; Dental Materials ; chemistry ; Dental Restoration Failure ; Dental Stress Analysis ; Materials Testing ; Zirconium ; chemistry

Titanium alloy material (TC4) samples were treated with nitriding technique. The dynamic friction and wear behavior of the modified layer were examined on a reciprocating sliding rig in artificial saliva. Microhardness, depth profile and wear mechanisms were investigated by means of MVK-H12, TALYSURF6, XPS and microscopy. The results demonstrate that after being treated with nitriding technique the titanium alloy material (TC4) has better tribological behavior and up-graded wear resistance. The wear mechanism involves adhesion.
Adsorption ; Biocompatible Materials ; Dental Alloys ; chemistry ; Dental Materials ; Dental Prosthesis ; Electricity ; Friction ; Humans ; Materials Testing ; Surface Properties ; Titanium ; chemistry

OBJECTIVES: This work aimed to synthesize a novel injectable alginate impression material and evaluate its accuracy. METHODS: Certain proportions of sodium alginate, trisodium phosphate dodecahydrate, potassium fluorotitanate, diatomaceous earth, and other ingredients were dissolved in water and mixed evenly with a planetary centrifugal mixer to obtain a certain viscosity base paste. Certain proportions of calcium sulfate hemihydrate, magnesium oxide, glycerin, and polyethylene glycol (PEG) 400 were mixed evenly with a planetary centrifugal mixer to obtain the reactor paste with the same viscosity as the base paste. The base and reactor pastes were poured into a two-cylinder cartridge at a 2∶1 volume ratio. A gun device was used to accomplish mixing by compressing materials into a mixing tip. The samples were divided into three groups: injectable alginate impression materials (IA group) as the experimental group, and Jeltrate alginate impression materials (JA group) and Silagum-putty/light addition silicone rubber impression materials (SI group) as the two control groups. RESULTS: Scanning electron microscopy (SEM) showed that the injectable alginate impression materials had a denser structure and fewer bubbles than the commercial alginate impression material. The accuracy of the three kinds of impression materials was evaluated by 3D image superposition. The deviations between the three test group models and the standard model (trueness) were 49.58 μm±1.453 μm (IA group), 54.75 μm±7.264 μm (JA group), and 30.92 μm±1.013 μm (SI group). The deviations of the models within each test group (precision) were 85.79 μm±8.191 μm (IA group), 97.65 μm±11.060 μm (JA group), and 56.51 μm±4.995 μm (SI group). Significant differences in trueness and precision were found among the three kinds of impression materials (P<0.05). CONCLUSIONS The accuracy of the new injectable alginate impression material was better than that of the traditional powder-type alginate impression material but worse than that of the addition silicone rubber impression materials. The novel injec-table alginate impression material demonstrated good operation performance and impression accuracy, showing broad application prospect.
Alginates/chemistry* ; Silicone Elastomers/chemistry* ; Dental Impression Materials/chemistry* ; Powders

OBJECTIVETo evaluate the biological safety of compound galvano-ceramic bridge by measuring the consistency of released nickel ion of the galvano-form slices cohered with Ni-Cr alloy slice specimens which were immersed in artificial saliva.

METHODSSpecimens were divided into five groups with four tests and one control. Test specimens were made into the structure like rectangle sandwich that one side of Ni-Cr alloy was cohered to the center surface of galvano golden base of 0.2 mm and another side was fused porcelain with the thickness of 0.3 mm (group A), 0.5 mm (group B), 1.0 mm (group C), and 0.3 mm (group D). And the Ni-Cr alloys were totally embedded in galvano golden base and firing porcelain. Naked Ni-Cr alloy was taken as control. Group D was immersed into acid artificial saliva (AS) with high fluoride, while others were in acid AS at 37 degrees C for 120 h. Then the consistency of released nickel ion in the solution was measured with inductively coupled plasma-atomic emission spectrometry (ICP-AES).

RESULTSNickel ions detected in the artificial saliva for the groups A, B, C, and D in acid AS with or without high fluoride were all under 0.005 mg/L Significant differences were found between each test group and the control [(0.65 +/- 0.45) mg/L].

CONCLUSIONSGalvano-ceramic bridge, Ni-Cr alloy bridge with fused porcelain and golden base, shows biological safety responsible for the consistency of released nickel ion.

Biocompatible Materials ; chemistry ; Dental Materials ; Materials Testing ; Metal Ceramic Alloys ; chemistry ; Nickel ; analysis

OBJECTIVETo compare the microstructure and mechanical properties of pure titanium specimens fabricated using laser melted rapidly solidified forming (LMRSF) and casting, and to provide scientific evidence for the new method of laser rapid forming in prosthodontic field.

METHODSSix pure titanium specimens were fabricated from pure titanium powder using LMRSF technology, and six pure titanium casting specimens were used as the controls. The tensile strength was measured and the microstructures and natural fracture surface of the pure titanium specimens made in two different ways were observed.

RESULTSCompared to that in the casting specimen, the microstructure of the LMRSF titanium specimens was denser and acicular structure distributed more uniformly. The tensile strength and the microhardness of the pure titanium specimens were (510.0 +/- 21.2) MPa and (201.4 +/- 14.5) MPa respectively, which were much higher than those of the dental pure titanium castings [(425.0 +/- 35.1) MPa and (186.5 +/- 9.5) MPa] (P < 0.01).

CONCLUSIONSThe microstructure and mechanical properties of the pure titanium specimens fabricated using LMRSF are better than that of the pure titanium castings. Therefore, the LMRSF will provide titanium framework with better quality for removable dental restoration.

Dental Casting Technique ; Dental Materials ; Dental Stress Analysis ; Hardness ; Lasers ; Materials Testing ; Titanium ; chemistry

OBJECTIVETo evaluate the influence of veneer application on failure behavior and reliability of lithium disilicate glass-ceramic (LDG) crowns of maxillary first molar, and thus to reveal the failure mechanism of bilayered LDG crowns.

METHODSTwenty-six LDG maxillary first molar crowns were fabricated in a dental laboratory using IPS e. max Press or IPS e. max Press/Ceram. The crowns were randomly assigned into two groups (with or without veneer application) with thirteen in each group. The crowns were cemented on composite resin dies. After storage in water for one week, the sliding-contact fatigue test was performed by sliding the steatite ceramic ball indenter (6 mm in diameter) from central fossa up to the lingual surface of disto-buccal cusp, cyclic loaded 1 200 000 times with a weight of 100 N at 2 Hz with a fatigue chewing simulator. Survived specimens were subjected to single-load-to-fracture testing using a steatite ceramic ball of 6 mm in diameter at a cross-head speed of 0.5 mm/min in a universal testing machine. Fracture load values were recorded and analyzed with t test. Weibull modulus was calculated to evaluate structure reliability. Fractographic analysis was carried out to determine fracture modes of the failed specimens by a stereomicroscope and a scanning electron microscope (SEM).

RESULTSStatistical analysis results indicated a significant difference of the fracture load values between monolithic group [(2071.23 ± 397.05) N] and bilayered group [(1483.41 ± 327.87) N] (P < 0.001). Monolithic and bilayered groups present similar Weibull modulus (95% confidence interval) as 6.15 (5.15 ∼ 7.15) and 5.54 (4.01 ∼ 7.08) respectively, with no significant difference (the confidence bounds overlapped with each other). Bulk fracture initiating from the middle of oblique ridge of the first maxilla molar was the primary failure mode of monolithic/bilayered LDG crowns. Crack propagation initiated from core-veneer interfacial defects was another major failure mode of bilayered all-ceramic crowns.

CONCLUSIONSVeneer application has some influence on fatigue failure of LDG crowns, but shows no effect on structure reliability. Accumulated damage combined with tensile stress concentration on the surface of veneer layer and defects within core-veneer interface lead to initiating of cracks. The mechanical property of veneering materials should be increased, and procedure of veneer application should be standardized and improved in order to reduce the failure rate of LDG molar crowns.

Crowns ; Dental Porcelain ; chemistry ; Dental Restoration Failure ; Materials Testing ; Molar

OBJECTIVETo explore the effect of changes of processing time on the surface properties of titanium coating formed by micro-arc oxidation (MAO).

METHODSForty-four disc-shaped pure titanium specimens with 10 mm diameter and 1 mm thickness were equally divided into 4 groups and processed by MAO technique in electrolytes containing 0.2 mol/L calcium acetate (CA) and 0.02 mol/L β-glycerol phosphate disodium salt pentahydrate (β-GP). The processing time were set at 1 min, 5 min, 10 min and 15 min respectively. The topograph of the MAO film surface and the film-substrate interface was observed by a scanning electron microscopy (SEM), and the composition was analyzed by an energy dispersive spectroscope (EDS) incorporated in the SEM. The phase and the microstructure of the film were analyzed by X-ray diffraction (XRD). The roughness of the film was measured using a roughness tester. The surface static contact angle was detected by a contact angle measurement instrument and the surface energy was calculated accordingly.

RESULTSWith the increase of processing time from 1 min to 15 min, the pore size increased from (1.30 ± 0.07) µm to (1.55 ± 0.09) µm, and film thickness increased from (10.2 ± 1.1) µm to (20.9 ± 2.9) µm. The content of the Ca in the film increased accordingly, and Ca/P increased from 1.99 to 2.45, and the surface energy increased from 24.62 mJ/m(2) to 39.49 mJ/m(2). Meanwhile, the XRD pattern indicated that rutile increased but anatase and titanium decreased gradually. At the time of 15 min, part of the MAO film peeled off.

CONCLUSIONSProcessing time has impact on the thickness, surface topography, crystal component and surface energy of titanium MAO coating. MAO film treated for 5 - 10 min demonstrated favorable surface properties.

Dental Implants ; Dental Materials ; chemistry ; Materials Testing ; Oxidation-Reduction ; Surface Properties ; Titanium ; chemistry

OBJECTIVETo study the strengthening of fluorophlogopite-based dental machinable ceramic through developing a new type of calcium-mica-based ceramic.

METHODSBased on the analysis of the crystal structure of the fluorophlogopite ceramic of Dicor MGC, the structure of a new type of calcium-mica-based ceramic was designed and the corresponding composition of the new material was experimented. And the new glass-ceramic was obtained through the treatment of glass preparation and nucleation. Then crystal content of the glass ceramic was analyzed by X-ray diffraction analysis (XRD) and the 3-point bending strength of the new ceramic was recorded.

RESULTSA new type of calcium-mica-based glass ceramic was developed and had the 3-point bending strength of (210.2 +/- 14.7) MPa. Compared with the strength of fluorophlogopite-based dental machinable ceramic, such as Dicor MGC, which was reported in the range of 150 approximately 180 MPa within inclusive studies, the higher strength of the new ceramic was recorded.

CONCLUSIONSThe fluorophlogopite-based dental machinable ceramic could be reinforced through internal strengthening.

Aluminum Silicates ; chemistry ; Dental Materials ; Dental Porcelain ; chemistry ; Materials Testing ; Tensile Strength

OBJECTIVETo research the influence of K(2)O composition in the raw material on leucite microcrystallization and to study the effect of leucite content on compressive strength of the dental glass ceramics reinforced by leucite microcrystallization.

METHODSThe raw materials with different K(2)O content were treated by a decided thermal treatment system. The products were analyzed by polaring microscope and X-ray diffractometer, and their compressive strength was also tested.

RESULTSThe microstructure of products from high K(2)O component was remarkably good, at microcrystal size of 0.8 micro m and the compressive strength was 206.6 MPa. A positive correlation was found between leucite volume and the compressive strength when leucite volume was less than 50% (Vol%).

CONCLUSIONSThe component of K(2)O has a great effect on the microstructure and the properties of the leucite-microcrystal-reinforced dental glass ceramics and the content of leucite microcrystals has a notable influence on the compressive strength of the dental glass ceramics.

Compressive Strength ; Crystallization ; Dental Porcelain ; chemistry ; Glass ; chemistry ; Materials Testing