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At least 55 records · Page 3Linked to original sources
PubMed2004

Clinical outcome of the altered cast impression procedure compared with use of a one-piece cast.

STATEMENT OF THE PROBLEM: An altered cast impression procedure to improve the support of distal extension removable partial dentures is widely taught, but not often used in dental practice. PURPOSE: The purpose of this study was to determine the efficacy of an altered cast compared to a one-piece cast with regard to base support, abutment health, and patient comfort over time. MATERIAL AND METHODS: Seventy-two patients receiving a mandibular bilateral distal extension removable partial denture were assigned randomly for treatment using either a one-piece or an altered cast. All impressions and associated laboratory procedures were made by one investigator. A second investigator evaluated extension, support, and adaptation of the denture bases by observation of border length and lifting of the indirect retainer from its seat. The space between the soft tissues and the base when the framework was related to the teeth was measured cross-sectionally at half the length of the denture base. Mobility, gingival index, and sulcus depths at 6 locations around each abutment tooth were recorded at insertion and again 1 year later. Chi-square tests were used to evaluate differences between the treatment groups (alpha=.05). RESULTS: There was 0.15 mm less space between the ridge crest and base in the altered cast group (P<.01), and underextension of the base occurred only in the one-piece cast group (P=.01). At insertion, no tissue-ward movement was observed in 85% of the prostheses when anterior-posterior rotation was attempted. Fifteen subjects (21%) were lost to recall at 1 year, but they were distributed equally between the 2 groups. Of the remaining 57 prostheses, 42% exhibited decreased base support and 33% had increased gingival inflammation; the deepest probing depth decreased in 61%, mobility decreased or remained the same in 80% of the direct abutments, and 88% of the subjects were satisfied. None of these findings were related to the impression procedure. CONCLUSION: The altered cast impression procedure does not offer significant advantages over the one-piece cast, provided the standards used in this study are met. These include a completely extended impression, use of magnification to adjust and ensure complete seating of the framework, and coverage of the retromolar pad and buccal shelf by the base.

Adult↗
PubMed1989

Dental casting of titanium and Ni-Ti alloys by a new casting machine.

The purpose of this study was to develop a new casting machine for titanium and Ni-Ti alloys. Properties of cast pure titanium and Ni-Ti alloys were studied by means of the tensile and casting tests. As gas in the mold was removed by the mold being heated under a high vacuum, the reaction between the molten metal and the mold decreased. The new control system and the two types of crucibles developed proved very useful for prevention of internal macro-defects in castings and for improvement of castability. Mechanical properties and castability of pure titanium were improved. Ni-Ti alloys could be cast without loss of their shape-memory effect or super-elasticity characteristics. The new casting machine is thought to be promising for the casting of titanium and Ni-Ti alloys. Furthermore, we can cast these alloys using conventional techniques and investments.

Dental Alloys↗
PubMed1996

Analysis of cryotherapy penetration: a comparison of the plaster cast, synthetic cast, Ace wrap dressing, and Robert-Jones dressing.

Four groups were studied to determine the cooling effect at skin level of ice application over common ankle bandages and casts. The plaster cast, synthetic cast, and Ace wrap dressing groups had 18 participants and the Robert-Jones dressing group had four participants. In a standardized fashion, ice bags were applied over each bandage or cast and skin temperatures were measured with a thermocouple over a 90-min period. The average final skin temperature was 16.5 degrees in the plaster cast, 18.8 degrees in the synthetic cast, 21.2 degrees in the Ace wrap dressing, and 28.7 degrees in the Robert-Jones dressing. The temperature curves showed that ice application effectively decreased skin temperatures through the plaster cast, synthetic cast, and Ace wrap dressing. The cooler temperature did not adequately penetrate the Robert-Jones dressing.

Adult↗
PubMed1992

Evaluation of the dermal effects of cast padding in coaptation casts on dogs.

Three configurations of cast padding and no cast padding were evaluated for their effects on skin in dogs. Padding was placed over bony prominences, between bony prominences, and over both areas for full-length padding under short-limb walking casts applied to 1 pelvic limb of Greyhounds. Evaluations were performed by pressure measurement over the calcaneal tuberosity, measurement of skin thromboxane B2 (TxB2) concentrations in skin over bony prominences, and measurement of plasma TxB2 concentrations. Pressure studies were performed to evaluate cutaneous pressures related to no cast padding and various configurations of cast padding. Concentrations of TxB2 in the skin were determined to evaluate the skin inflammatory effects of no padding and the padding configurations, and TxB2 concentrations in the plasma were analyzed to ascertain whether they could be used to predict impending dermal pressure lesions. Flexion of casted limbs revealed the greatest pressure over the calcaneal tuberosity with full-length cast padding. This was followed in decreasing order by no cast padding, padding over the prominences, and padding between the prominences. Compared with all other bony prominences and padding configurations, TxB2 skin concentrations were significantly higher over the calcaneal tuberosity when no padding was used and over the lateral base of metatarsal V when padding was placed between the prominences. Over the calcaneal tuberosity, this was attributed to the sharpness of the prominence and its potential for movement. This high TxB2 concentration corresponded to the high pressure found in the pressure studies. Over the lateral base of metatarsal V, the increase in TxB2 concentration was related to the mass of the prominence and the tendency for localized padding to settle around the area.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

In vitro determination of equine third metacarpal bone unloading, using a full limb cast and a walking cast.

OBJECTIVE: To improve fracture treatment, in vitro experiments were performed to study the influence of a full limb cast and a walking cast on the loading regimen of bones in the distal portion of the equine forelimb. ANIMALS: 6 forelimbs of 6 Shetland ponies. PROCEDURE: Loading of the third metacarpal bone was considered a representative measure for distal limb loading. Electrical resistance rosette strain gauges were attached to the dorsal, palmar, medial, and lateral surfaces of the midshaft of this bone in 6 forelimbs of 6 Shetland ponies. The limbs were tested in a pneumatic loading device to a maximal load of 1,500 N. RESULTS: Both casts decreased the amount of compressive forces acting on the metacarpal bone. Application of a full limb cast resulted in a variable and eccentric decrease, remaining strains ranging from 84 to 7% of the baseline value. A walking cast was superior in that it gave a centric and more uniform reduction of compressive loading to < 11% of the baseline value. Moreover, a walking cast neutralized the bending and torsion components of the loading. CONCLUSION: This study confirmed the clinical experience that a walking cast creates more reliable and favorable conditions for healing of fractures than does a full limb cast.

Animals↗
PubMed1992

Use of plastic bar molded casting in the modification of variably expanding investment to compensate for casting shrinkage of nickel-chromium alloy.

Trial plastic bar molded castings were compared for accuracy with cast crowns by means of a nickel-chromium alloy, which was used to establish the liquid density of variably expanding investments. The plastic bars were invested to evaluate the change of expansion rate in a wide range of six liquid densities from 0% to 100%, and the distances between the sections were measured before and after casting. Wax crowns were cast to obtain a more detailed relation around 0% expansion at seven liquid densities, and the gaps between the base of the die and the margin of the crown were measured before and after casting. The expansion rates of both castings were calculated and thus were proportional to the liquid density; both regression curves indicated high correlation coefficients. As a result of the statistics of the Student's t-test, the difference between the two methods was not significant. The trial plastic bar was useful in establishing the variably expanding investment for precise casting of artificial crowns.

Chromium Alloys↗
PubMed1990

[Casting accuracy and shrinkage of titanium castings made with zirconia investments].

To obtain inlay, crown and bridge types of titanium castings with sufficient size accuracy, zirconia investments with 10 mol % calcia were studied for their setting expansion, thermal expansion, total expansion, casting shrinkage compensation deficiency on fabrication method, particle size of zirconia, calcia and mixing liquid. Addition of calcia caused the change from contraction to expansion in setting and the additional thermal expansion at 900-1,200 degrees C. The choice of calcia and mixing liquid makes great influence on setting expansion, which is grouped into saturation type and delayed expansion type. By the use of the saturation type, total expansion could be controlled in the range of -2-(+)3%. Titanium castings of inlay, crown, bridge types with the values -2-(+)2% of casting shrinkage compensation deficiency could be successfully obtained. The casting shrinkage of titanium was estimated as 1.8-2%. The castings have the surface with a metallic brilliance as cast.

Calcium↗
PubMed1980

The effects of alginate impressions on the surface of cast gypsum. I. The physical and chemical structure of the cast surface.

The surface of cast gypsum which has set against alginate impression material has been shown to vary according to the specific impression material used. The variation is both physical and chemical. Poor cast surfaces have been shown to consist completely of unreacted calcium sulphate hemihydrate to a depth of at least 80 micrometer. The best cast surfaces consist of considerable amounts of syngenite (potassium calcium sulphate), along with a small amount of gypsum and unreacted hemihydrate. Cast surfaces with a lower syngenite content were intermediate between these two extremes. No cast surfaces which had set against any alginate impression exhibited complete conversion of hemihydrate to gypsum, which characterized the surface formed when the same gypsum products set against Teflon. Although dental stones may contain a small amount of a potassium salt as an accelerator, it was shown that this amount does not significantly alter gypsum surfaces cast against alginates. The potassium ions involved in the setting reaction to form syngenite clearly enter the cast at its interface with the impression, presumably by way of an exudate from the gelled impression.

Alginates↗
PubMed2000

Full-crown castings made with water-saturated and dry casting ring liners.

The carcinogenic potential of asbestos has led to the development of non-asbestos materials for use as casting ring liners. Cellulose paper are replacing asbestos paper. The brass die and crown were made to produce full crowns. The standardized wax pattern was replicated twenty-nine times. Two grooves were marked on the die and wax patterns. The marginal gaps between wax pattern and die shoulder were measured. Then, the wax specimens were divided into three groups. The dry ring liner and the water-saturated ring liner were used, in the third group, any liner was used. The castings were fabricated and were fitted on the die. Measurements were made of the distance separating the gingival margin of the castings from the shoulder on the die. Measurement points (X and Y) were the same points used for wax pattern measurement. The difference between wax pattern and casting was found to be statistically significant in all the groups (p = 0.0051). There was no statistically significant difference between groups on the comparative fit of the castings. The mean marginal space in the water-saturated liner group was 0.51 +/- 0.12 mm (X), 0.51 +/- 0.11 mm (Y), and in the dry liner group, the mean marginal space was 0.47 +/- 0.09 mm (X), 0.49 +/- 0.08 mm (Y). In the unlined group, they were 0.52 +/- 0.18 mm (X), 0.55 +/- 0.17 mm (Y). Use of dry ring lining material resulted in smaller marginal spaces between castings and the die than use of water-saturated cellulose ring lining material. The results demonstrated that the use of dry liners may improve the fit of castings to dies.

Cellulose↗
PubMedDate not supplied

Synthetic casting tapes: benefits and uses of Delta-Cast Conformable.

Casting is a traditional practice that has changed relatively little over thousands of years. Today, however, with the emphasis on evidence-based medicine, health professionals are examining the practice and investigating ways of improving it for the benefit of both patients and those who perform it. Most fractures and many soft tissue injuries are usually managed in a rigid cast, which brings with it complications and disadvantages. The ideal form of fracture fixation would stabilize the fracture while allowing some movement of the fracture site and soft tissue compression. This article explores the use of Delta-Cast Conformable (Johnson and Johnson), a synthetic casting tape, in both primary and secondary casting. The role of Delta-Cast Conformable with regard to focused rigidity casting, a new philosophy in fracture management, is discussed.

Casts, Surgical↗
PubMed1989

[Influence of casting temperature on mechanical properties of castings].

The influence of the different casting conditions on mechanical properties of castings was investigated for two kinds of Ni-Cr alloys, pure gold and pure silver by means of tensile strength tests, fractography, microstructural observation and EPMA. The casting rates of Ni-Cr alloy castings increased as the casting temperature increased. On the other hand mechanical properties worsened as the casting temperature increased. The same phenomena were observed in the case of pure gold and pure silver. These worsened mechanical properties seemed to be caused by a decrease of intergranular coherence and an increase of porosity in the Ni-Cr alloys and pure silver. Furthermore, in the case of pure silver, identical causes were responsible for the worsened mechanical properties following the rise in casting pressure and mold temperature. But in the case of pure gold, worsened mechanical properties seemed to be caused by the growth in grain size. Therefore, the best mechanical properties were obtained when the controlled temperature was at the liquid point or at the melting point.

Chromium Alloys↗
PubMed1992

Comparison of the retentive properties of a sleeve cast crown/core system with crowns cemented to conventional cast cores.

The retention of the crown to the core substructure is of great importance for a successful restoration. The aim of this study was to compare the retentive values of the Flexi-Cast post and its sleeve crown/core complex with that of a crown cemented to a conventional cast post. Forty single-rooted teeth divided equally into four groups were used. Flexi-Cast crown and cores were cemented to Flexi-Cast posts in groups 1 through 3. Group 4, the control group, comprised crowns cemented to conventional cast cores. Groups 1 through 4 had retentive values of 126.2, 135.5, 185.0, and 79.3 lb, respectively. Statistically, the increase in retention for all sizes of the Flexi-Cast crown and cores when compared with the control cast post and crown was found to be significant (p less than or equal to 0.0001).

Cementation↗
PubMed2004

Why cast shadows are expendable: insensitivity of human observers and the inherent ambiguity of cast shadows in pictorial art.

The kinds of visual cues artists choose to use or not use in their work can offer insight into perceptual processes. On the basis of the observed paucity of the use of cast shadow in pictorial art, we hypothesized that cast shadows might be relatively expendable as pictorial cues. In this study, we investigated two potential reasons for this expendability: first, viewers might be insensitive to much of the information that cast shadows provide; and, second, ambiguities about what is shadow and what is pigment can often be resolved only through motion-something that static media are ill-equipped to deal with. In experiment 1, we used a visual-search paradigm in which viewers had to determine if there were odd cast shadows in sets of 4, 8, 16, and 32 objects. In experiment 2, viewers had to discriminate between shadow/pigment ambiguities in both still and moving images. Our results demonstrate that viewers are neither particularly sensitive to static cast-shadow incongruities, nor are they able to disambiguate cast shadow from pigment without continuous motion information. Taken together, these results may help explain why cast shadows are relatively rare in static pictorial work.

Adult↗
PubMed2006

Bending resistance of unit cast posts-and-cores compared with noble posts following molten cast core attachment.

The aim of this in vitro study was to evaluate the bending resistance of unit cast posts-and-cores (UPC) and prefabricated high noble posts with cast-on cores. Tapered posts (ER post-restoring system) of three sizes in diameter (ISO 50, 90, 110) were investigated: UPC were cast of three different alloys (Au-Pt-Pd, Au-Ag-Pt, Co-Cr-Mo). Also, prefabricated tapered noble posts (Heraplat and Pt-Ir) were cast over with metal cores of the different alloys. Prefabricated titanium posts of each size were precision fit into the central core channels of the Co-Cr-Mo cores to serve as control specimens. The 0.2% yield strengths (R(0.2)) of all specimens were tested on a universal testing machine. One-way and three-way anova and Bonferroni-Dunn's multiple comparison tests were performed for the statistical analysis. The mean bending resistance R(0.2) of the unit cast posts-and-cores was 45 +/- 4-46 +/- 5 N for ISO 50 (control group: 54 +/- 3 N), 91 +/- 9-93 +/- 7 N for ISO 90 (control group: 117 +/- 11 N) and 115 +/- 13-130 +/- 12 N for ISO 110 (control group: 141 +/- 12 N). Except for the Au-Pt-Pd UPC of ISO 110, the yield strengths of the control groups were significantly superior to all unit cast alloy combinations (P < 0.05). Significantly lower bending resistance was found for Co-Cr-Mo cores cast over Heraplat and Pt-Ir posts compared with the corresponding Heraplat/Au-Ag-Pt, Heraplat/Au-Pt-Pd and Pt-Ir/Au-Ag-Pt posts-and-cores.

Dental Alloys↗
PubMed1980

Fit of unit-cast fixed partial dentures related to casting ring size and shape.

Four types of casting rings were tested for producing accurate-fitting fixed partial dentures. None of the casting rings tested produced ideal results, but the larger oval and round rings produced fixed partial dentures cast as a single unit with more complete seating than those produced in smaller round casting rings when phosphate bonded investment and Type III gold were used. Fixed partial denture seating was affected by the casting ring size but not because of its shape. While distortion of the wax and dimensional change in the gold alloy do affect the seating qualities of castings, this was not statistically significant in this study.

Dental Casting Investment↗
PubMed1992

When should a synthetic casting material be used in preference to plaster-of-Paris? A cost analysis and guidance for casting departments.

An accurate cost analysis of the use of one of the new synthetic casting materials (Cellacast) compared with plaster-of-Paris (Gypsona) was undertaken over a 3-month period in the fracture clinic of Cardiff Royal Infirmary. The mean duration of usage before failure for synthetic forearm, scaphoid and below-knee casts was found to be approximately twice that of plaster casts. The use of synthetic casting materials was found to be cost-effective in situations where there was thought to be a high probability that structural failure of the cast would occur. Guidelines for the use of plaster-of-Paris and synthetic casting materials are presented.

Calcium Sulfate↗
PubMed1997

The distortion of cast cobalt-chromium alloy partial denture frameworks fitted to a working cast.

PURPOSE: This in vitro study examined the distortion of 10 identically designed cast cobalt-chromium alloy frameworks, individually constructed, and adjusted by 10 technicians to fit one of 10 replicated stone working casts. MATERIAL AND METHODS: The distortion was measured with a specially developed strain gauge apparatus when the frameworks were seated on the maxillary metal analog, the stone working cast, or a stone duplicate cast. RESULTS: A statistically significant difference between the distortion of each of the frameworks was observed. A significant difference in the distortion was also observed for the frameworks when placed on each of the three casts. The distortion was the least when the frameworks were seated on the stone working cast and the greatest when seated on the metal analog. CONCLUSION: This study demonstrated that the distortion of a framework is not related to its closeness of fit as observed by the presence or absence of gaps between the framework components and the teeth.

Alloys↗
PubMed1996

Plantar pressure measurements during ambulation in weightbearing conventional short leg casts and total contact casts.

Total contact casts have been shown to be effective in healing plantar neuropathic ulcerations. The proposed mechanism of action is reduction of pressure over the ulcer during ambulation. However, there is little information to support this contention. Plantar pressure distribution was studied using standard short leg casts and total contact casts in normal feet. Both types of casts reduced forefoot pressure in study subjects. This occurred because of an increase in plantar surface area exposed to weightbearing forces. While increased force was shifted to the midfoot, there was no increase in pressure due to a corresponding increase in midfoot surface area exposed to this force. No significant difference was noted between standard short leg casts and total contact casts.

Adult↗