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PubMed2005

Basic evaluation of cast joining for electroformed coping using multi-purpose alloys.

The purpose of this study was to evaluate the bonding interface and bonding strength of electroformed coping when cast joining was used with a multi-purpose alloy. The multi-purpose alloy was cast at a mold temperature of 700, 750 or 800 degrees C. A high noble alloy tab was also soldered onto an electroformed coping as a control. Sectioned surfaces of cast joining and soldered specimens were observed using a scanning electron microscope and analyzed using an electron probe micro analyzer. Shear bonding strength of specimens cast at 750 degrees C and that of soldered specimens were determined. The edge of the cast joining alloy was round, but this improved as temperature increased. Diffusion of elements from the cast joining alloy and electroformed coping was detected at the interface, which contributed to a significantly higher bonding strength in the cast joining specimen than in the soldered specimen. These results suggested that the cast joining could be potentially employed for electroformed copings.

Dental Abutments↗
PubMed1992

The castability of unalloyed titanium in three different casting machines.

The general demand for a variety of fine detail work made of titanium has resulted in the development of equipment/systems for the casting of this metal. Dental casting machines suitable for the casting of titanium are now also available. The aim of the present study was therefore to evaluate the possibility of precision casting of dental crown restorations of unalloyed titanium. The three kinds of casting equipment currently used in Sweden were tested by evaluating the crown edge diameter of 10 titanium crowns processed by each one of the titanium casting machines. The results revealed that clinically acceptable margins can be obtained but also that further improvements in processing have to be achieved before titanium casting can be considered as uncomplicated as the casting of traditional dental gold alloys.

Crowns↗
PubMed2004

[The effect of mold temperature on the accuracy of titanium castings].

PURPOSE: To study the effect of mold temperature on the accuracy of titanium castings invested in the ZrP99 investment. METHODS: 30 artificial stone dies simulated the post-tooth and their corresponding complete crown wax patterns were made with a truncated cone-shape standard brass model with round sleeves. They were divided randomly into five groups and each group had six samples. Four group wax patterns were invested in ZrP99 investment as test groups and one group was invested in Titavest-CB investment as control. The test group moulds were cast at the mould temperature 600 degrees centigrade, 450 degrees centigrade, 300 degrees centigrade, 150 degrees centigrade, respectively. Measure the distance separating the gingival margin of the crown and the shoulder of the die in the same way as for the wax pattern. The casting accuracy was represented by the discrepancies derived from the space distance measurements made with wax patterns and cast crowns. t test and one-way ANOVA were used for statistical analysis. RESULTS: Measurement of the casting accuracy indicated that the casting accuracy of the control group was higher than all the test groups. When the mold temperature was lower than 450 degrees centigrade, the accuracy of the castings invested in ZrP99 investment was improved significantly with the mold temperature raised. CONCLUSION: To satisfy the requirement of the clinical practice in the point of the casting accuracy, the mold temperature of ZrP99 investment must be chosen higher than 300 degrees centigrade.

Crowns↗
PubMed1980

[Measurement of casting shrinkage with U-type tungsten die (author's transl)].

A simple method was developed for the accurate measurement of casting shrinkage using a U-type tungsten die. A wax pattern was prepared on the die and both were invested together in phosphate bonded investment. Cobalt-chromium alloy, Regalloy shot 2, was cast and its shrinkage was calculated from the distance of the gap created between the die and the cast piece. In order to evaluate the effects of some manipulative variables on the cast shrinkage value of the alloy, mold temperature, kind of liquid for the investment and powder/liquid ratio were varied and shrinkage values were obtained. The results showed that the shrinkage value was not affected by the kind of liquid and the power/liquid ratio, but significantly decreased as the mold temperature raised up to 600 degree C. However, this effect was eliminated by means of substractive correction of the thermal expansion of the tungsten die. Thus, the casting shrinkage of the cobalt-chromium alloy, Regalloy shot 2, was calculated to be 2.08 +/- 0.02%. The casting shrinkage of pure gold was also measured with the same procedure. The casting shrinkage was calculated to be 1.73 +/- 0.04% and highly consistent with the value (1.74%) reported by R. Earnshaw. This suggested that the developed method was sufficiently effective for the accurate measurement of casting shrinkage.

Dental Casting Investment↗
PubMedDate not supplied

The influence of spruing technique on the development of tension in a cast partial denture framework.

Distortions of cast removable partial denture frameworks result more from the method of sprue connection than from other variables in the investment and mold preparation. A standard test pattern and optical measuring equipment were used to evaluate residual casting stresses. Based on the data obtained from the initial study, modified removable partial framework patterns were made and cast under varying conditions. The use of a dorsal spruing technique and a box-type casting flask resulted in less distortion than use of the conventional vertical sprue attachment and investing in a ring flask. Dorsal spruing and use of a box-type casting flask reduced the deformation of a cast partial denture framework in the area of the palatal bar and retentive elements up to 0.3 mm. Such a tension-free casting method means a better fit of the partial framework on the master cast and intraorally.

Dental Casting Investment↗
PubMed2000

Can skin surface pressure under a cast reveal intracompartmental pressure?

Although monitoring intracompartmental pressure (IP) under a cast is very important, it is not possible to measure it in every patient undergoing cast treatment. This study aims to answer the question of whether skin surface pressure (SSP) under a cast can reveal IP. A plaster cast was applied to a sculpted inflatable forearm model with dorsal and volar compartments. SSP under the cast was measured at five different localizations from both dorsal and volar sides of the model and compared to the corresponding IP. In the second experiment, a posterior tibial compartment syndrome model was created in both limbs of five rabbits. Correlation analysis was performed between IP and SSP under the cast. All of the SSP measurements taken from the dorsal and volar side of the sculpted forearm model correlated with IP. Mean correlation coefficient of the measurements was 0.995 (P = 0.000) (SD 0.002, range 0.992-0.999). SSP and IP correlation analysis in the posterior tibial compartment syndrome model of 10 limbs in five rabbits revealed a high correlation. The mean correlation coefficient was 0.973 (P = 0.000) (SD 0.024, range 0.916-0.997). Measuring the pressure between the skin and cast can monitor IP. SSP monitoring can help the physician, patient or parents in the follow-up of patients undergoing cast treatment.

Animals↗
PubMed1982

The casting accuracy of nickel--chromium alloys for fixed prostheses.

The casting accuracy of four nickel--chromium alloys (Ultratek, Omega, Microbond N/P2, and Nobil-Ceram) was compared to that of a precious alloy, Jelenko "O". The experiment consisted of fabricating and fitting cast copings to a cobalt--chromium test preparation of a maxillary central incisor and measuring the marginal discrepancy in eight selected points. The experiment indicated that Jelenko "O" had the greatest casting accuracy, followed successively by Ultratek, Nobil-Ceram, Microbond N/P2, and Omega. Statistical analysis of the data revealed no significant difference between Jelenko "O" and Ultratek alloys in fit of five of eight test points, but Jelenko "O" was significantly better in fit than Nobil-Ceram, Microbond N/P2, and Omega alloys. The following conclusions may be drawn from this experiment: 1. The nickel--chromium alloys tested did not cast as consistently or as accurately as precious alloy Jelenko "O". 2. The casting accuracy may be related to the amount of casting shrinkage that occurs in each alloy type, and further research is necessary to determine if expansion compensation of the selected phosphate-bonded investment recommended by the alloy manufacturers is adequate for the casting shrinkage of the test alloys. 3. Alloy composition and technique parameters may also influence the accuracy of the casting, but further research is necessary to determine their singular effects.

Chemical Phenomena↗
PubMed2006

The effects of Scaphoid and Colles casts on hand function.

Although necessary for bone healing, immobilisation temporarily prevents hand function and may necessitate corrective physiotherapy later. Scaphoid and Colles casts are both commonly used to immobilize scaphoid fractures. Non-union rates are comparable with both casts. The Scaphoid cast incorporates the thumb, whereas the Colles cast leaves the thumb free. We compared the effect of the two casts on hand function in 20 healthy right-hand-dominant volunteers using the Jebsen-Taylor Hand Function Test. Data were obtained through a mixed between and within subject design. Both casts prolonged the time taken to complete the hand function test compared to controls. Testing in the Scaphoid cast took significantly longer than in the Colles cast.

Adult↗
PubMed2003

Fatigue resistance of cast occlusal rests using Co-Cr and Ag-Pd-Cu-Au alloys.

STATEMENT OF PROBLEM: Fatigue failure in a removable partial denture framework includes fracture of the occlusal rest at the rest-minor connector angle. PURPOSE: This in vitro study evaluated the fatigue resistance of 0.8-mm-thick occlusal rests cast with Co-Cr and Ag-Pd-Cu-Au alloys. MATERIAL AND METHODS: The specimen consisted of occlusal rest (0.8 x 2.0 x 10 mm), vertical minor connector (0.9 x 2.0 x 5.0 mm), and denture base connector (1.5 x 5.0 x 25 mm). Twenty-five specimens each were cast with Co-Cr and Ag-Pd-Cu-Au alloys. From each group, 5 specimens were subjected to a load-deflection test conducted to determine the amount of deflection to be used in fatigue test. The fatigue test was performed such that the occlusal rest component was deflected by displacing the denture base component in a tissueward direction. Predetermined denture base displacement values of 0.25 and 0.49 mm for Co-Cr and Ag-Pd-Cu-Au specimens, respectively, were repeated at a rate of 500 cycles/min by use of a displacement-controlled fatigue testing machine, until occlusal rest failure occurred or a preset limit of 2 million cycles was achieved. The survival rates of the occlusal rests were calculated assuming a chewing cycle of 2 x 10(5) per year. Scanning electron microscopy (SEM) photographs were made to examine the fracture surfaces and to identify casting defects. The relationship between fatigue cycles and number of casting defects was determined by Spearman rank correlation analysis (P<.01). RESULTS: All 20 Co-Cr specimens outran the preset limit, whereas 18 Ag-Pd-Cu-Au specimens fractured. After 3 years of simulated clinical use, only 50% of the Ag-Pd-Cu-Au occlusal rests survived. Statistical analysis showed that the fatigue cycles and number of casting defects were inversely related (P<.01). Fatigue crack initiation occurred at the inner-curvature surface of the rest-minor connector angle. The typical Ag-Pd-Cu Au fatigue fracture surface consisted of smooth propagation and dimpled and smooth final fracture areas. CONCLUSIONS: This study suggests that cast Co-Cr rests are more rigid and fatigue resistant than Ag-Pd-Cu-Au rests. The fatigue resistance of 0.8-mm-thick occlusal rests may be adequate if cast with Co-Cr alloy. An increased number of casting defects may hasten the fatigue failure of occlusal rests.

Chromium Alloys↗
PubMed1999

Comparison of the accuracy of working casts made by the direct and transfer coping procedures.

STATEMENT OF PROBLEM: A working cast with dies that accurately record the prepared abutments, surrounding soft tissues, and adjacent and opposing teeth is necessary. PURPOSE: This study compared the accuracy of the direct and transfer coping methods in recording the vertical and horizontal dimensional relationship of a pair of removable dies in a working cast before and after separation from the stone base. Among the procedures used for making impressions of abutments for fixed partial dentures, the transfer coping procedure has specific advantages. In particular, where there are multiple abutments, this procedure, in which individual impressions are made of the abutments, transfer copings are made, and a transfer impression of the copings is used for seating the dies and fabrication of a dental stone base, is useful. METHODS: Two groups of working casts were fabricated from a stone master cast containing 2 ivorine teeth to simulate abutments. The first group of working casts was fabricated directly from the elastomeric impression of the abutments using a 2-pour procedure. The second group of working casts was made using the transfer coping procedure. RESULTS: When the interdie dimensions in each group were compared with that of the master cast, after separation and replacement of the dies in the stone base, the differences were less than 100 microm and similar for both the direct and transfer coping techniques. CONCLUSIONS: These findings show that either procedure is equally effective in positioning the dies in the working casts.

Analysis of Variance↗
PubMed1998

The effect of casting conditions on the biaxial flexural strength of glass-ceramic materials.

OBJECTIVE: To assess the effect of mould and glass casting temperatures on the biaxial flexural strength (BFS) of two different types of castable glass-ceramic, using existing laboratory equipment and techniques. METHODS: Two castable glass-ceramic materials were evaluated. One glass (LG3) is based on SiO2-Al2O3-P2O5-CaO-CaF2, and is similar in composition to glasses used in the manufacture of glass-ionomer cements. The other glass (SG3) is based on SiO2-K2O-Na2O-CaO-CaF2, and is a canasite-based material. Both materials were used to produce discs of 12 mm diameter and 2 mm thickness using the same lost-wax casting process as used for metal castings. Mould temperatures of between 500 degrees C and 1000 degrees C and glass casting temperatures of between 1100 degrees C and 1450 degrees C were evaluated. The cast discs were cerammed and the biaxial flexural strength determined with a Lloyd 2000 R tester. RESULTS: A significant difference was found for the BFS in the range of mould temperatures evaluated, with the optimum investment mould temperature being 590 degrees C for LG3 and 610 degrees C for SG3 (p = 0.0002 and p = 0.019, respectively). No significant differences were seen between any of the glass casting temperatures evaluated. SIGNIFICANCE: The mould temperature for castable glass-ceramic materials produced using the lost-wax casting process can have a significant effect on BFS. The optimum mould temperature may differ slightly depending on the type of material being used. The glass casting temperature of these materials does not appear to have a significant effect on BFS.

Analysis of Variance↗
PubMed1982

Effect of tone-inhibiting casts and orthoses on gait. A case report.

In the adult case presented, inhibitory casting proved successful in decreasing the positive support reaction. When casting was discontinued, the positive reaction returned. To provide a long-term solution for this problem, a polypropylene tone-inhibiting AFO was fabricated. It incorporated the same principles as the casts. The success achieved with casting was rapidly regained and then surpassed with the use of the tone-inhibiting AFO. Natural recovery might be cited by some as the cause for improvement in the patient presented. However, the loss of improvement during the interval between the removal of the inhibitory casts and the initiation of the use of the tone-inhibiting AFO demonstrates that the casting and the position provided by the casts had a positive effect on our patient. This notion is further supported by the fact that our patient still required use of the tone-inhibiting AFO as late as March 1980. We have no explanation for the rapid improvement following the cranioplasty. Suggestions for further research would include a similar study with a larger number of subjects and the use of cinematography and kinesiological EMG during walking with and without tone-inhibiting casts and orthoses to determine the effect of the devices on spastic muscle groups and gait patterns.

Adult↗
PubMed2003

Use of a lateral offset short-leg walking cast before high tibial osteotomy.

The clinical results after high tibial osteotomy for the treatment of symptomatic varus gonarthrosis are unpredictable. Although preoperative gait analysis has been shown to be useful in predicting successful outcome after high tibial osteotomy, there are no readily available preoperative clinical tests for predicting success. The authors did a study to determine the effects of an offset short-leg walking cast as a potential predictor of clinical success after high tibial osteotomy. Specifically, the authors evaluated the effect of an offset short-leg walking cast on pain relief and changes in the peak external adduction moments in patients with symptomatic varus gonarthrosis indicated for high tibial osteotomy. Nineteen consecutive patients indicated for high tibial osteotomy were enrolled and completed the study. All patients had precast gait analysis to determine baseline parameters. Immediately after gait analysis, a short-leg lateral offset walking cast was applied and worn for 3 days to allow time for adaptation. Gait analysis then was repeated. Western Ontario and McMaster Universities Osteoarthritis Index pain scores were obtained before and after the cast was applied. The cast resulted in a mean reduction in pain of 53%, and a mean reduction in the peak external adduction moment of 36% in the 17 of 19 patients who tolerated the cast. The reduction in pain was correlated with the reduction in the peak adduction moment (r = 0.63). The authors conclude that an offset short-leg walking cast results in pain reduction that correlates with changes in external adduction moments about the knee. Therefore, an offset short-leg walking cast may prove to be an effective tool for predicting patients who ultimately will benefit from valgus high tibial osteotomy.

Adult↗
PubMedDate not supplied

Postoperative shoulder-spine spica cast for young children.

Immobilization of the young child after spinal surgery is an important component of the surgical plan. This study reviews the authors' experience with postoperative immobilization in a shoulder-body spica cast and provides a detailed description of the technique. Twenty-two children with an average age of 31 months at the time of surgery were placed in the shoulder-spine spica cast after hemivertebra excision. There was no loss of correction in any of the 22 children during the period of postoperative immobilization. All patients were able to be ambulatory in the shoulder-spine spica cast while immobilized. Patients experienced the minor complications of prolonged cast wear, with one cast becoming loose and three casts causing skin rash. One patient required removal of the cast 6 weeks after surgery for unrelated nausea and vomiting. The shoulder-spine spica cast has been used at the authors' institution with great success and allows children to be ambulatory after hemivertebra resection.

Casts, Surgical↗
PubMed1989

Mechanical properties and material characteristics of orthopaedic casting material.

In this study, two types of orthopaedic casting materials were evaluated: the Johnson & Johnson Specialist plaster bandage and the 3M Scotch-cast Plus fiber glass bandage. The materials were evaluated using tensile tests to determine the elastic modulus, yield strength, and ultimate tensile strength. To determine the structural characteristics and stiffness of a cylindrical cast, each material was formed around a foam cylinder core and tested in a four-point bend jig. A computer-based model using the finite element method (FEM) was developed for a cylindrical cast of both types and compared with the experimental findings. A second FEM model with loads applied at the periphery was performed to simulate the clinical observations of plaster bandage breakdown at the ends of a cast. It is with these tests that the two bandage materials were compared and evaluated. It was concluded that the plaster bandage, while initially stiffer than the fiber glass bandage, had much lower yield stress. This implies that the plaster cast may break down under loads that would leave the fiber glass cast intact. It was also determined that the plaster bandage load displacement curve is bilinear. The bilinear characteristic of the plaster bandage explains its breakdown at the ends of a cast.

Biomechanical Phenomena↗
PubMed1997

The effect of a plaster cast on lumbosacral joint motion. An in vivo assessment with precision motion analysis system.

STUDY DESIGN: This study was conducted to assess the effect of a plaster cast on the mobility of the lumbosacral joint in 10 patients with chronic low back pain. During static and dynamic exercises, movements between the proximal vertebra (L4 or L5) and the sacrum were registered in 10 patients without a support and after the application of a plaster cast, and with and without unilateral hip immobilization, respectively. OBJECTIVES: To investigate whether plaster casts actually immobilize the lumbosacral joint. SUMMARY OF BACKGROUND DATA: The presumed stabilizing effect of a lumbar orthosis on the lumbosacral joint has been the subject of many studies in the past years, and contradictory reports have been published. METHODS: The measurements were performed by means of Precision Motion Analysis System, an optoelectronic three-dimensional motion analysis system using infrared light. The patients were asked to perform maximal spinal flexion to extension, maximal pelvic tilt (static test conditions), and to walk within the measurement volume (dynamic test condition). This procedure was repeated with the patients wearing a plaster cast with and without unilateral hip fixation. Mobility was expressed in translations and rotations around three axes. For statistical analysis, repeated measurements two-way analysis of variance was used. RESULTS: Considerable rotations were found only in the sagittal plane. Both plaster casts appeared to decrease mobility during the static test conditions. During the dynamic test condition, however, no significant decrease of mobility of the lumbosacral joint by either of the casts could be observed. In both cast conditions, considerably more sagittal rotation was found during walking than with the other two exercises. CONCLUSION: In the sagittal plane, a plaster cast with or without unilateral hip immobilization can decrease motion during spinal flexion-extension. This stabilizing effect on the lumbosacral joint could not be observed during walking.

Adult↗
PubMedDate not supplied

Immediate single-leg spica cast for pediatric femoral diaphysis fractures.

PURPOSE: Immediate spica cast application is the standard of care for young children with isolated femur fractures. We evaluated the outcomes and function of children treated with single-leg spica casts. METHODS: We performed a retrospective review of 45 children treated with single-leg spica casts. Demographic data, mechanism of injury, hospitalization time, time in cast, and complications were collected by chart review. Children returned for a physical examination and radiographs. Subjects completed a questionnaire about the child's functional level and the Activities Scale for Kids. RESULTS: There were 33 boys and 12 girls. The average age was 3.3 (9 months to 9 years). The mechanism of injury was a fall in 71%. The mean hospitalization was 1 day (0-4 days) and the mean time to union was 6 weeks (4-9 weeks). Ninety-five percent of the patients crawled in the cast, 90% pulled to stand, 81% cruised, and 62% walked either independently or with assistive devices. One half of the patients in school or daycare returned while in the cast. Two children failed because of unacceptable shortening. Two children required repeat reductions under anesthesia due to unacceptable alignment. Five casts broke at the hip joint. At final review, there was 1 rotational malunion. There were no radiographic malunions. The median Activities Scale for Kids score was 95 of 100 possible points. CONCLUSIONS: The single-leg spica can safely, effectively manage low-energy femur fractures in young children. SIGNIFICANCE: The single-leg spica may address some of the social concerns associated with the use of a spica cast for simple femur fractures.

Casts, Surgical↗
PubMed1999

Distortion of three-unit implant frameworks during casting, soldering, and simulated porcelain firings.

PURPOSE: The aim of this study was to assess distortion inherent in casting, soldering, and simulated porcelain firings of screw-retained, implant-supported three-unit fixed partial dentures (FPDs). MATERIALS AND METHODS: Ten wax patterns were fabricated on a die-stone cast containing two implants, 20 mm apart from center to center. Five specimens were cast in a high-palladium alloy, exposed to simulated porcelain firings, sectioned, and then soldered with low-fusing solder. Five specimens were cast, sectioned, soldered with high-fusing solder, and then exposed to simulated porcelain firings. For each specimen, two horizontal and six vertical distances between appropriately scribed reference points were measured with a traveling microscope. Comparisons were made among the various measurements taken after wax-pattern fabrication, casting, high- and low-fusing soldering, and each porcelain firing. Data were analyzed using a repeated-measures factorial ANOVA (alpha = 0.05). RESULTS: Significant difference was detected in the amount of horizontal distortion during casting (53 +/- 24 microns) and high-fusing soldering (-49 +/- 50 microns), as well as in the amount of horizontal distortion during high-fusing soldering (-49 +/- 50 microns) and low-fusing soldering (17 +/- 26 microns). However, no clinically significant difference was found in the amount of horizontal distortion during casting, low-fusing, and high-fusing soldering. The greatest amount of distortion during the simulated porcelain firings took place during the oxidizing cycle. CONCLUSIONS: Soldering did not improve the casting misfit of a three-unit implant-retained FPD model. Metal-ceramic implant frameworks should be oxidized before intraoral fit evaluation.

Analysis of Variance↗