OBJECTIVETo investigate the surface roughness property of the titanium castings cast in a new investment for titanium casting.

METHODSSix wax patterns (20 mm × 20 mm × 0.5 mm) were invested using two investments: three in a new titanium investment material and three in the control material (Rematitan Plus). Six titanium specimens were obtained by conventional casting. After casting, surface roughness of the specimens were evaluated with a surface profilometer.

RESULTSThe surface roughness of the specimens cast in new titanium investment material was (1.72 ± 0.08) µm, which was much smaller than that from Rematitan Plus [(1.91 ± 0.15) µm, P < 0.05].

CONCLUSIONSThe surfaces of titanium cast using these two investment materials are both smooth enough to fulfill the demand of the titanium precision-casting for prosthodontic clinical use.

Dental Casting Investment ; chemistry ; Dental Casting Technique ; Materials Testing ; Surface Properties ; Titanium ; chemistry

OBJECTIVETo investigate the effect of self-developing investment (FUS-invest) on the reactive layer of titanium castings.

METHODSThree 10 mm x 10 mm x 1 mm pure titanium castings were founded using FUS-invest. Metallographical structure of reactive layer was observed. X-ray diffraction (XRD) and scanning electron microscope with energy-dispersive spectrum (EDS) were used to analyze the status of composition of the casting surface. Micro-Vickers hardness was measured.

RESULTSThe metallograph indicated that the reactive layer was composed of coarse flake-shaped alpha phase of grains. The value of micro-Vickers hardness with the range 243 to 314 MPa had not significantly difference under the depth of 105 microm beneath the surface. The XRD pattern clearly showed the peaks of ZrO2, SiO2, Mg2TiO4 and TiO2. EDS analysis demonstrated that the main elements were Al, Si, Zr and Cl.

CONCLUSIONFUS-invest is suited for pure titanium casting because of the thin reactive layer and less change to metallographical structure.

Crowns ; Dental Casting Investment ; Dental Casting Technique ; Hardness ; Humans ; Investments ; Silicon Dioxide ; Surface Properties ; Titanium

OBJECTIVETo investigate expansion characteristics of two kinds of commercial investment (Cristo balite Micro II and Cristo Quick), and their effects on cast accuracy of a dental Ag-Pd casting alloy.

METHODSTwo kinds of investment were mixed at the ratio of 1:3. The setting and thermal expansion curves of the investment were recorded according to the requirements of ISO7490 and expansion rate calculated, respectively. Plate-like wax-patterns with pre-marked points were invested in casting rings (lined with ceramic fiber liners with thickness of 0.45 mm). Castwell M.C dental alloy were melted with gas flame and cast with a centrifugal casting machine. The differences between the castings and the wax patterns at corresponding points were calculated to represent the dimensional changes of the investment.

RESULTSThe setting, thermal and total expansion rates were 0.68, 1.18, 1.86 for Cristo balite Micro II, and 0.94, 1.03, 1.97 for Cristo Quick. The setting and thermal expansion rates were statistically significant between two kinds of investment (P < 0.05), while not for the total expansion rates (P > 0.05). Effect of different investment on the precision of castings was not statistically significant (P > 0.05).

CONCLUSIONWithin the scope of this study, gypsum-bonded investment with similar total expansion rates but different expansion characteristics has no effect on the casting precision of Ag-Pd dental alloys.

Calcium Sulfate ; Ceramics ; Dental Alloys ; Dental Casting Investment ; Dental Casting Technique ; Investments

The aim of this study is to evaluate the physical and mechanical properties of our homemade investment material for the IPS-Empress2 castable ceramic. The IPS specific investment material was taken as control. Results show that the setting time, density before heating, density after heating, rate of open hole, compressive strength at 2 hours after setting and the compressive strength after heating to 920 degrees C of the homemade investment material are 9 minutes, 1.813 g/cm3, 1.402 g/cm3, 38.1%, 5.42 MPa and 8.37 MPa respectively, which are comparable or even better than the specific material. Under the SEM, the crystals of the phosphate hydrate in our homemade material are smaller than those in the special material. Since the physical and mechanical properties of our homemade investment material are comparable or superior to those of the specific material, a conclusion is drawn that it has a promising prospect of future clinical application.
Aluminum Silicates ; chemistry ; Crowns ; Dental Casting Investment ; chemical synthesis ; chemistry ; Dental Materials ; chemical synthesis ; chemistry ; Dental Porcelain ; chemistry ; Lithium Compounds ; chemistry ; Microscopy, Electron, Scanning ; Shear Strength ; Surface Properties ; Tensile Strength

OBJECTIVETo study the effects of different heating timings after mixing the materials and different heating methods on the expansion characters of a quick-heating gypsum-bonded investment.

METHODSThe setting expansion rate of GC Cristoquick II gypsum-bonded investment was measured with a setting expansion tester 30, 60, 120 min after mixing the material respectively. The thermal expansion rates of the material at different setting time (30, 60, 120 min after mixing) and under different heating treatment methods (quick and conventional heating techniques) were also determined using a thermal dilatometer for dental investments, the total linear expansion rate were calculated. The effects of heating time and heating methods on the expansion of the investments were statistically analyzed with SPSS 11.0 software, using ANOVA multiple comparison (alpha=0.05).

RESULTSStatistical differences were found among the setting and thermal expansion rates of the investment at different heating timings after mixing the material (P<0.01). Setting expansion, thermal expansion and total expansion rates increased with the setting time before heat treatment, while thermal expansion rates under different (quick and conventional) heating methods were not statistically significant (P>0.05).

CONCLUSIONThe expansion characters of the quick-heating gypsum-bonded investment are influenced by different heating timings after mixing the material. The heat treatment technique of this quick-heating investment recommended needs to be modified to ensure casting precision.

Calcium Sulfate ; Dental Casting Investment ; Dental Casting Technique ; Heating ; Hot Temperature ; Humans ; Investments

OBJECTIVETo investigate the effects of the improved FUS-invest investment for zirconium-oxide titanium crown and bridge on the reaction layer.

METHODS10 mm x 10 mm x 1 mm titanium castings were invested. Spectrum analysis was done to its reaction layer, the metallographic examination was observed and Vickers hardness was measured.

RESULTSThe reaction layer was not obvious by the metallographic examination. The layer with plenty of Si was hardly detectable. The needle crystal layer diffused distribution on the surface of the titanium matrix. The depth was about 55 microm. Spectrum analysis showed that the contents of Si and Zr decreased as the depth increased. The microhardness, which obviously decreased from the surface to the matrix, tended to be equal with the hardness of the matrix after the depth reached 75 microm from the surface.

CONCLUSIONThe thickness of the reaction layer of the improved FUS-invest investment for zirconium-oxide titanium crown and bridge was decreased to 55 microm from 85 microm, which was the thickness before improvement.

Crowns ; Dental Casting Investment ; Dental Casting Technique ; Hardness ; Humans ; Investments ; Oxides ; Surface Properties ; Titanium ; Zirconium

OBJECTIVETo observe the influence of different investing methods and mold cooling methods on pure titanium castings invested in the self-made investment, and to provide theoretic base for the development for the investment.

METHODSThe influence of investing methods (one-step investing method and two-step investing method) on castability and crown fit of titanium castings were investigated, and the influence of cooling methods on reaction layers, mechanical properties and crown fit of titanium castings were investigated.

RESULTSBoth the investing methods exhibited good castability, but only the titanium full crowns by one-step investing method showed clinically acceptable fit. Although the quenching group showed thinner reaction layer(100 microm), lower strength and similar elongation rate, the titanium castings by bench cooling showed clinically acceptable full crown fit with 115 microm thick reaction layer as cast.

CONCLUSIONThe one-step investing method and the bench cooling are recommended for the self-made investment.

Crowns ; Dental Casting Investment ; Dental Casting Technique ; Dental Materials ; Fungi ; Investments ; Materials Testing ; Surface Properties ; Titanium

OBJECTIVETo investigate the effect of two different ring liner thickness on the deformation of resulted castings.

METHODSGC No.2 casting rings (50 mm in height and 39.5 mm in diameter) were lined with two dry ceramic fiber liners with thickness of 0.70 mm and 0.45 mm. Plate-like wax patterns with pre-marked points were invested with a gypsum-bonded investment and the rings were cast with a silver-based dental alloy. The difference between the castings and the wax patterns at corresponding points was calculated to represent the dimensional change of the investment in the rings at different directions.

RESULTSThe expansion of the investment in the ring was non-isotropic, with larger radial direction expansion than the axial direction expansion (P < 0.01). In the scope of this study, the effect of two different ring liner thickness on the casting precision was statistically non-significant (P > 0.05).

CONCLUSIONThe liners with two different thickness failed to eliminate non-isotropic deformation of the castings under the testing conditions of this study.

Calcium Sulfate ; Ceramics ; Crowns ; Dental Casting Investment ; Dental Casting Technique ; Humans ; Prostheses and Implants

OBJECTIVEIn order to compare the influence of casting and laser welding on magnetic retentive force, the magnetic retentive forces of laser-melted and cast post-keepers of the magnetic attachments were measured in vitro.

METHODS5 cast and 6 laser-melted post-keeper specimens (Magfit MD800) were formed, respectively. Using untreated keeper as control group, the vertical magnetic retentive forces were measured by a universal testing machine.

RESULTSThe average vertical magnetic retentive force of the laser-melted post-keeper group and the cast post-keeper group in vitro were (4.223 +/- 0.217,0)N, (3.792,9 +/- 0.296,4)N, respectively. Compared with the cast post-keeper group, the average vertical magnetic retentive force of the laser-melted post-keeper groups was much higher in vitro (P < 0.05).

CONCLUSIONLaser welding had less influence on the magnetic retentive force of the magnetic attachments than casting.

Dental Alloys ; Dental Casting Investment ; Dental Casting Technique ; Dental Prosthesis Retention ; instrumentation ; Dental Soldering ; methods ; Denture Precision Attachment ; Electromagnetic Fields ; Lasers ; Magnetics ; instrumentation ; Post and Core Technique ; Stainless Steel ; Welding ; methods

OBJECTIVEIn order to introduce the laser welding technology into root-cap making, this study compared the surface characters and internal structures of laser-melted and cast post-keeper to provide experimental data for clinical application of the technique.

METHODSUsing untreated keeper as the control group, the surface characters and metallographic structures of the keepers were examined by stereomicroscope, metallographic microscope and SEM, and element analysis were conducted with EPMA.

RESULTSThe laser-melted post-keeper basically kept the original smooth and the internal structure of the keeper, the heat reaction zone was extremely small and elements diffused mutually around the fusion zone obviously. While in the cast post-keeper, the surface was rough and had an oxide-layer. The internal structure changed and a fusion band formed between the base alloy and the keeper, but element diffusion was limited to the fusion zone.

CONCLUSIONCompared with casting, laser welding technique demonstrated less influence on the surface and internal structure of the keepers.

Dental Alloys ; Dental Casting Investment ; Dental Casting Technique ; Dental Prosthesis Retention ; instrumentation ; Dental Soldering ; methods ; Denture Precision Attachment ; Electromagnetic Fields ; Hot Temperature ; Lasers ; Magnetics ; instrumentation ; Stainless Steel ; Welding ; methods