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At least 523 records · Page 29Linked to original sources
PubMed1985

Plastic bronchitis: large, branching, mucoid bronchial casts in children.

Expectoration of large, branching, bronchial casts, termed plastic bronchitis, is an uncommon condition in children. Asthma or allergy often is the cause of cast production, but in some instances no etiology is found. Five children produced large, obstructing bronchial casts that either were expectorated or were extracted at bronchoscopy. Four of the children had asthma or allergies and the fifth had congenital tricuspid atresia and chronic pericardial and pleural effusions. In two patients, expectorated casts initially were thought to be aspirated food material. Radiographic findings during periods of cast formation included atelectasis, obstructive emphysema, bronchiectasis, pleural effusion, and pneumomediastinum. Cast formation may be self-limited but generally ceases with appropriate treatment of the causative disorder. Bronchoscopic extraction of casts may benefit some patients.

Asthma↗
PubMed1992

[Clinical significance of urinary sediment dysmorphic red blood cells and casts in renal disease].

We investigated the utility of measuring dysmorphic red blood cells (d-RBC) and urinary casts in the diagnosis and assessment of prognosis of renal diseases by evaluating these parameters in a total of 278 urine specimens from 78 patients with various renal diseases at our hospital. Urinary sediments obtained by the conventional method with in 4 hours after voiding were subjected to Sternheimer and Malbin's staining and examined under a conventional light microscope. We used the criteria we previously devised for classification of RBC as d-RBC and for classification of casts hyaline, granular, epithelial, red blood cell, white blood cell, fatty, or waxy. When there were 5 or more urinary sediment red blood cells per high-power field, d-RBC was found in 94% of samples from patients with chronic glomerulonephritis. The finding of d-RBC was not related to glomerulonephritis pathologically diagnosed according to the WHO classification system for biopsy specimens. Even when there were fewer than 5 red blood cells per high-power field, d-RBC was sometimes found. Casts of all types were found in samples from patients with chronic glomerulonephritis or chronic renal failure. In samples from patients with chronic pyelonephritis, however, white blood cell, fatty, and waxy casts were not found, and less than 1 granular or epithelial cast per low-power field was found. The findings for the presence and the extent of both d-RBC and casts were in good accord with and changed with the clinical course, indicating that d-RBC and casts of urinary sediment can be used to predict the prognosis of patients with renal disease.

Adult↗
PubMed1994

Casting in sport.

Attempts by sports medicine professionals to return high school athletes with hand and wrist injuries to competition quickly and safely have been the source of confusion and debate on many playing fields around the country. In addition to the differing views regarding the appropriateness of playing cast usage in high school football, a debate exists among sports medicine professionals as to which material is best suited for playing cast construction. Materials used in playing cast construction should be hard enough to provide sufficient stabilization to the injured area and include adequate padding to absorb blunt impact forces. The purpose of the biomechanical portion of this investigation was to attempt to determine the most appropriate materials for use in constructing playing casts for the hand and wrist by assessing different materials for: 1) hardness using a Shore durometer, and 2) ability to absorb impact using a force platform. Results revealed that RTV11 and Scotchcast were the "least hard" of the underlying casting materials and that Temper Stick foam greatly increased the ability of RTV11 to absorb impact. Assessment of the mechanical properties of playing cast materials and review of current developments in high school football rules are used to aid practitioners in choosing the most appropriate materials for playing cast construction.

Journal Article↗
PubMed2006

[3D-data acquisition of partially edentulous cast using grating projection method].

OBJECTIVE: A method for 3D-data acquisition of partially edentulous cast was introduced to lay the foundation for reconstructing 3D digital model of a partially edentulous cast and studying computer aided design (CAD) to a removable partial denture framework. METHODS: Using projection system controlled by a computer, four frames of sinusoidal fringe pattern at pi/2 intervals were projected onto the surface of partially edentulous cast consecutively within 0.4 second. Deformed fringe patterns modulated by the surface height of the cast were recorded by a digital camera. The phase value with the height information was demodulated with phase-shifting method. The transition from the unwrapped phase to the height of the points on the cast was performed with triangulation method. The multiview 3D data was integrated automatically to obtain the complete 3D profile data and the 3D digital model of the partially edentulous cast was reconstructed. RESULTS: Dense and complete points-cloud data was achieved without scanning blind zone basically. The anatomic structure of reconstructed 3D digital model was sharp and clear. CONCLUSION: As an alternative for acquiring 3D data of partially edentulous cast, this method presented here with high precision and high speed meets the need for the subsequent 3D design to removable partial denture framework.

Computer-Aided Design↗
PubMed1992

Casting system effectiveness--measurement and theory.

Evaluating castability as a property of dental casting alloys is an unworkable concept, since any measure is demonstrably affected by several external factors. Casting System Effectiveness (CSE) is shown experimentally and theoretically to depend primarily upon the time taken for the advancing front to freeze. A spiral tube mold was used to measure casting length obtained under variations in casting temperature; this pattern is proposed as a standard measure of CSE. A Bernoulli 'free-fall' numerical model is shown to reproduce the principal features of such casting, with some evidence of viscosity limitation of the turbulent flow at long casting lengths. Direct measurement of melt velocities confirmed turbulent flow in the mold. A method is also suggested for assessing the influence of investment porosity on CSE.

Acceleration↗
PubMedDate not supplied

Sprue design in removable partial denture casting.

OBJECTIVES: Correct sprue design is a major factor in the reduction of defects in castings of cobalt-chromium alloy. The purpose of this study was to investigate the sprue arrangements decided by a group of dental technicians, for a series of proposed removable partial denture castings, in order to determine if there was any consistency between them which would suggest the application of criteria in their design. METHODS: Information was gathered by postal inquiry with recipients asked to indicate their sprue designs on diagrams of patterns for proposed cobalt-chromium partial denture castings. RESULTS: Replies were received for 260 proposed castings from dental schools, technical colleges and commercial laboratories which gave an overall response rate of 52%. Results displayed a wide range of responses in relation to sprue number and dimension, attachment site and the intended direction of metal flow. CONCLUSION: It was concluded that the group of technicians studied arbitrarily chose sprue arrangements for the castings proposed rather than following definite design criteria that seek to minimize potential problems during casting procedures.

Chromium Alloys↗
PubMed2000

Evaluation of the dimensional changes and surface roughness of gold crowns cast with rapidly prepared phosphate-bonded investment: a pilot study.

STATEMENT OF PROBLEM: Accelerated bench-set and burnout schedules are used with little knowledge of the effect acceleration has on clinical factors determining casting success. PURPOSE: This pilot study investigated the effect of 2 rapid mold preparation schedules on full crown castings by comparing size, margin sharpness, and surface roughness. MATERIAL AND METHODS: Three groups of 10 crowns were cast with a type III gold alloy. All crowns were nominally identical, only their mold preparation schedules differed. Two groups used accelerated schedules; the third group was cast using a conventional schedule. Group comparisons were based on direct microscopic measurements of crown diameters (x50 magnification), and surface roughness was measured. Margin sharpness was judged by amount of marginal length lost in the axial direction as a result of the casting process. RESULTS: Measured crown diameters, indexing size for the 3 groups, were not significantly different. Crowns made with the conventional schedule had greater surface roughness, and better margin sharpness or length. CONCLUSION: Crowns were successfully cast using accelerated mold preparation techniques and considerable time was saved, but a small loss of margin length or fineness was observed.

Crowns↗
PubMed1997

The effects of sprue design on the roughness and porosity of titanium castings.

PURPOSE: This study measured the effects of the sprue number and position on the roughness and porosity of cast titanium crowns. MATERIAL AND METHODS: Twenty-four complete veneer crown wax patterns were fabricated on a stainless steel die with a 30-degree bevel finish line. Twelve wax patterns were sprued with one 8-gauge wax sprue and the remaining 12 were double sprued. All patterns were invested with a phosphate bonded investment. Castings were made with a titanium casting, according to the manufacturer's instructions, with commercially pure titanium (> 99.5%) ingots. The castings were carefully cleaned and the surface roughness was measured with a profilometer. The specimens were then embedded and sectioned. Internal porosities were quantified with photographs by computerized image analysis. Data were analyzed with an ANOVA and the Student's t test with a confidence level of 95%. RESULTS: The roughness value of the occlusal third of the crowns for the single sprue group (Ra = 3.0 +/- 0.9 microns) was significantly higher than other measurements (p < 0.05). There were statistically significant differences in values of porosity areas between the single sprue group (1.5 +/- 0.7 mm2) and the double sprue group (0.2 +/- 0.2 mm2) (p < 0.01). The double sprue design resulted in a relatively smoother casting surface and less internal porosity than the single sprue design. CONCLUSIONS: Improvements in the degree of roughness and porosity of titanium crown castings were the result of the double sprue design.

Analysis of Variance↗
PubMed1998

A new method for casting discrepancy: some results for a phosphate-bonded investment.

OBJECTIVES: An accurate and realistic casting discrepancy method applicable to base metal alloys has hitherto been lacking. The purpose of this study was to develop a method for determining casting discrepancy free of interference from oxide, slag and surface defects, working under realistic conditions. In addition, a variable was sought that could be used for calibrating the casting process to allow for local errors. METHODS: A crown pattern was designed to incorporate circular V-grooves on the margin and the inside surface of the occlusal part for determination of the 'groove root diameter' (GRD) with a measuring microscope. Castings using a phosphate-bonded investment were made to test the effects of 'hygroscopic' expansion, burn-out temperature, powder/liquid ratio and groove location. RESULTS: The tested investment variables showed the expected effects, but the distortion between marginal and pulpal regions was clearly shown, as were interactions between some variables. 'Special liquid' proportion appears to be a good candidate variable for process calibration. CONCLUSIONS: The GRD method was shown to be sensitive and reproducible. It is also applicable to many other casting systems, and in particular to monitoring overall process discrepancy, i.e. from tooth preparation to casting, which is suggested as being the key issue.

Analysis of Variance↗
PubMed1982

Effect of casting methods on accuracy of peridental restorations.

The present study has shown that the accuracy of peridental gold alloy castings depends 1) on the type of casting machine used, 2) on the diameter of the casting sprue, and 3) on the strength properties of the investment material. The dependence between the accuracy and the three factors mentioned is based on erosion of the investment mold by the inflow of the liquid casting alloy. The vacuum casting technique proved to be a more gentle casting method than centrifugal and vacuum/pressure techniques.

Chemical Phenomena↗
PubMed1981

Correlation between macroscopic porosity location and liquid metal pressure in centrifugal casting technique.

Radiographic analysis of uniform cylindrical castings fabricated by the centrifugal casting technique has revealed that the macroscopic porosity is dependent on the location of the sprue attachment to the casting. This is attributed to the significant pressure gradient associated with the centrifugal casting technique. The pressure gradient results in different heat transfer rates at portions of the castings near and away from the free surface of the button. Consequently, the macroscopic porosity is invariably at portions of the casting close to the free surface of the button. In addition, some optimized sprue-reservoir combinations could be predicted and proved, based on this pressure gradient concept.

Chemical Phenomena↗
PubMed2005

The influence of mold temperature on the fit of cast crowns with commercially pure titanium.

Commercially pure titanium (CP Ti) has been widely applied to fabricate cast devices because of its favorable properties. However, the mold temperature recommended for the manufacture of casts has been considered relatively low, causing inadequate castability and poor marginal fit of cast crowns. This study evaluated and compared the influence of mold temperature (430 degrees C--as control, 550 degrees C, 670 degrees C) on the marginal discrepancies of cast CP Ti crowns. Eight bovine teeth were prepared on a mechanical grinding device and impressions were used to duplicate each tooth and produce eight master dies. Twenty-four crowns were fabricated using CP Ti in three different groups of mold temperature (n = 8): 430 degrees C (as control), 550 degrees C and 670 degrees C. The gap between the crown and the bovine tooth was measured at 50 X magnification with a traveling microscope. The marginal fit values of the cast CP Ti crowns were submitted to the Kruskal-Wallis test (p = 0.03). The 550 degrees C group (95.0 microm) showed significantly better marginal fit than the crowns of the 430 degrees C group (203.4 microm) and 670 degrees C group (213.8 microm). Better marginal fit for cast CP Ti crowns was observed with the mold temperature of 550 degrees C, differing from the 430 degrees C recommended by the manufacturer.

Animals↗
PubMed1989

[Application of nitrides to dental casting. 2. Feasibility as coating materials for Co-Cr alloy].

Nitrides used in this experiment are hBN, A1N and Si3N4. We studied feasibility of nitrides as wax pattern coating materials for Co-Cr alloy in an atmosphere of argon. Wax patterns were painted with coating material of nitrides (first investing), then a mixture of phosphate bonded investment and water was used in outer investing (second investing). The temperature of mold was 800 degrees C, and an argon arc vacuum-pressure casting machine was used. We cast the thin specimens in Co-Cr alloy (composition Co: 63 wt%, Cr: 27 wt%, Mo: 5 wt%, Bal.: 5 wt%; melting point: 1,380 degrees C). Surfaces of cast specimens were investigated using the unaided eye, a scanning electron microscope and a surface roughness analyzer. Furthermore, the thick specimens (globular form: phi 6.5 mm) using coating material of hBN were investigated using the unaided eye. Results were summarized as follows; 1. The nitrides controlled remarkably the reaction between cast specimen and investment. 2. The nitrides had the good effect of separation. 3. The cast surface coated the nitrides had less clinging than uncoated one, and this indicated that its cleansability was improved. 4. The nitrides decreased the surface roughness (Rz) of the cast to about 1/3. 5. hBN had the best effect in nitrides. 6. hBN also had the effect in a thick globular specimen.

Ammonia↗
PubMed1989

Layered structure of cast titanium surface.

The present study concerns the surface layered structure of the cast Ti. A commercial Ti was cast into a mold which was made of a phosphate-bonded Al2O3/SiO2 investment. Elemental analyses of the interfacial zone of the casting were made under an electron probe micro-analyzer. The interfacial zone was composed of four layers: the outermost reaction or casting burn layer, the second layer of an O-and Al-stabilized alpha case, the third layer in which Si, P, O, and C were inhomogeneously concentrated, and the fourth layer which consisted of acicular or plate-like crystals. It was observed that the larger the cast volume and the higher the mold temperature, the thicker became each layer and the coarser became the acicular grains. Probably, the layered structure was formed through decomposition of reducible species in the burnout investment and diffusion of the resulting elements into the casting.

Dental Casting Investment↗
PubMed2000

Evaluation of the new TAMZ titanium alloy for dental cast application.

OBJECTIVE: To reveal the potential of the new titanium alloy as dental prosthodontic materials. METHODS: Dental castings of TAMZ alloy were investigated in the casting machine specially designed for titanium. A mesh pattern was used to count the castability value. The mechanical properties were measured by means of a universal testing machine. Optical micrography was done on the exposed cross-section of TAMZ alloy casting. From the surface to the inner part the Knoop hardness in reacted layer of TAMZ alloy casting was measured. The structure and elemental analyses of the reacted layer were made by SEM and element line scanning observation. RESULTS: The castability value (Cv = 98%) and the tensile test (sigma b = 850 Mpa, sigma 0.2 = 575 Mpa, delta = 7.33%) data were collected. The castings microstructure showed main alpha phase and small beta phase. Knoop hardness in the surface reacted layer was greater than that in the inner part. From the SEM and element line scanning observation, there are three different layers in the surface reacted layer of the TAMZ alloy castings, and higher level of element of O, Al, Si and Zr were found in the reacted layer while the Si permeated deeper than others. CONCLUSION: TAMZ alloy can be accepted as a material for dental alloy in prosthodontics.

Aluminum↗
PubMed2003

[The measurement of retentive force of laser-melted and cast post-keepers of Magfit magnetic attachments].

OBJECTIVE: In 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. METHODS: 5 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. RESULTS: The 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). CONCLUSION: Laser welding had less influence on the magnetic retentive force of the magnetic attachments than casting.

Dental Alloys↗
PubMed2005

[Effect of two different ring liner thickness on the precision of castings].

OBJECTIVE: To investigate the effect of two different ring liner thickness on the deformation of resulted castings. METHODS: GC 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. RESULTS: The 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). CONCLUSION: The liners with two different thickness failed to eliminate non-isotropic deformation of the castings under the testing conditions of this study.

Calcium Sulfate↗
PubMed1981

[Studies on the accuracy of the castings. (Part 10) On the effects of starting time of the heat to phosphate bonded investment mold (author's transl)].

Properties of phosphate bonded investments are superior than that of plaster bonded investments in mechanical properties, expansional values for compensating to the casting shrinkage of alloys, and refractory resistance. Therefore, phosphate bonded investments have been available to casting for high fusing alloys. But, their properties are varied easily by manipulating. In this report, two commercial products of Cerami Gold (Whip--Mix Corp.) and Ceravest (G--C Dental Industrial Corp.) were used. They were studied on setting expansion, thermal expansion, compressive strength, change of pH value caused by setting reaction, decrement of weight, casting accuracy and roughness of castings in process of time. Results were follows; 1. The weight decrement of investment mold were about 1.5% on Cerami Gold and 3.5% on Ceravest at 24 hours after the mold had been prepared. 2. pH value of Cerami Gold investment mold changed to 8.5 from 7.0 at 5 hours after mixing, but that of Ceravest investment mold changed to 9.0 from 7.0 at 3 hours. 3. The setting expansion of Cerami Gold investment was caused about 0.9% at 3 hours and that of Ceravest investment was about 0.3% at 1 hour ater mixing. Since then, they were to be constant. 4. The thermal expansion of Cerami Gold investment was decreased by elapsed time until 3 hours after mixing, and then since passing at 5 hours, they were increased. But, that of Ceravest investment was decreased in process of time. 5. The compressive strength of both investments were increased as long as elapsed time after setting. Heating at 800 degrees C in the oven, it was 100--110 Kg/cm2 regardless of time on Ceravest investment, and other was 170 kg/cm2 which was increased until passing 5 hours. 6. The roughness of castings surface were similar to the mold surface and they were H3 12--16 microns which were decreased as elapsed time after investment was mixed. 7. Accurate castings were produced by the mold heated after 24 hours, using with Cerami Gold investment. On the Ceravest investment, it was 30 minutes of 5 hours after mixing.

Dental Casting Investment↗