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PubMed2000

[A surface reacted layer study of titanium-zirconium alloy after dental casting].

OBJECTIVE: To investigate the influence of the mold temperature on the surface reacted layer of Ti-Zr alloy castings. METHODS: Ti-Zr alloy was casted into a mold which was made of a zircon (ZrO2.SiO2) for inner coating and a phosphate-bonded material for outer investing with a casting machine (China) designed as vacuum, pressure and centrifuge. At three mold temperatures (room temperature, 300 degrees C, 600 degrees C) the Ti-Zr alloy was casted separately. The surface roughness of the castings was calculated by instrument of smooth finish (China). From the surface to the inner part the Knoop hardness and thickness in reacted layer of Ti-Zr alloy casting was measured. The structure of the surface reacted layer was analysed by SEM. Elemental analyses of the interfacial zone of the casting was made by element line scanning observation. RESULTS: The surface roughness of the castings was increased significantly with the mold temperature increasing. At a higher mold temperature the Knoop hardness of the reactive layer was increased. At the three mold temperature the outmost surface was very hard, and microhardness data decreased rapidly where they reached constant values. The thickness was about 85 microns for castings at room temperature and 300 degrees C, 105 microns for castings at 600 degrees C. From the SEM micrograph of the Ti-Zr alloy casting, the surface reacted layer could be divided into three different layers. The first layer was called non-structure layer, which thickness was about 10 microns for room temperature group, 20 microns for 300 degrees C and 25 microns for 600 degrees C. The second layer was characterized by coarse-grained acicular crystal, which thickness was about 50 microns for three mold temperatures. The third layer was Ti-Zr alloy. The element line scanning showed non-structure layer with higher level of element of O, Al, Si and Zr, The higher the mold temperature during casting, the deeper the Si permeating and in the second layer the element Si could also be found. CONCLUSION: The mold temperature is one of the major factors influencing to casting quality. In order to reduce the surface reacted layer of Ti-Zr alloy castings, the lower mold temperature and the investment without Si should be chosen.

Dental Alloys↗
PubMed2003

Biliary casts after orthotopic liver transplantation: clinical factors, treatment, biochemical analysis.

OBJECTIVES: Biliary casts develop in up to 18% of liver transplant recipients. Casts are associated with morbidity, graft failure, need for retransplantation, and mortality. Proposed etiological mechanisms include acute cellular rejection, ischemia, infection, and biliary obstruction. We aimed to identify clinical features associated with biliary cast formation, review treatments, and analyze the biochemical composition of casts at a single, large, liver transplant center. METHODS: Patient records were reviewed retrospectively to identify patients who developed casts. Data were collected with attention to ischemia, rejection, obstruction, infection, immunosuppression, postoperative biliary drain use, and cast-directed management, and were compared with data from controls. Cast specimens, retrieved at cholangiography, were analyzed with chromatography techniques. RESULTS: Ischemic factors were noted in 70% (7/10) of cast patients versus 15% (6/40) of controls (OR = 13.2; 95% CI = 2.7-66.0; p = 0.001). Biliary strictures were present in 50% of cast patients versus 10% of controls (OR = 9.0; 95% CI = 1.8-45.2; p = 0.01). Differences in cold ischemia time, acute cellular rejection, cyclosporin use, infection, and postoperative biliary drain use were not significant. Casts were successfully treated by endoscopic and percutaneous methods in 60% of patients. One patient died of cast-related complications (mortality 10%). Four casts were in satisfactory condition for biochemical analysis. Bilirubin was the main component ( approximately 10-50%). Bile acid synthesis products and cholesterol comprised smaller percentages, and protein comprised only 5-10%. CONCLUSIONS: Biliary casts are more likely to develop in the setting of hepatic ischemia and biliary strictures. Endoscopic and percutaneous cast extraction might achieve favorable results and should be attempted before surgical therapy.

Adult↗
PubMed2006

Genetic affinities among the lower castes and tribal groups of India: inference from Y chromosome and mitochondrial DNA.

BACKGROUND: India is a country with enormous social and cultural diversity due to its positioning on the crossroads of many historic and pre-historic human migrations. The hierarchical caste system in the Hindu society dominates the social structure of the Indian populations. The origin of the caste system in India is a matter of debate with many linguists and anthropologists suggesting that it began with the arrival of Indo-European speakers from Central Asia about 3500 years ago. Previous genetic studies based on Indian populations failed to achieve a consensus in this regard. We analysed the Y-chromosome and mitochondrial DNA of three tribal populations of southern India, compared the results with available data from the Indian subcontinent and tried to reconstruct the evolutionary history of Indian caste and tribal populations. RESULTS: No significant difference was observed in the mitochondrial DNA between Indian tribal and caste populations, except for the presence of a higher frequency of west Eurasian-specific haplogroups in the higher castes, mostly in the north western part of India. On the other hand, the study of the Indian Y lineages revealed distinct distribution patterns among caste and tribal populations. The paternal lineages of Indian lower castes showed significantly closer affinity to the tribal populations than to the upper castes. The frequencies of deep-rooted Y haplogroups such as M89, M52, and M95 were higher in the lower castes and tribes, compared to the upper castes. CONCLUSION: The present study suggests that the vast majority (> 98%) of the Indian maternal gene pool, consisting of Indio-European and Dravidian speakers, is genetically more or less uniform. Invasions after the late Pleistocene settlement might have been mostly male-mediated. However, Y-SNP data provides compelling genetic evidence for a tribal origin of the lower caste populations in the subcontinent. Lower caste groups might have originated with the hierarchical divisions that arose within the tribal groups with the spread of Neolithic agriculturalists, much earlier than the arrival of Aryan speakers. The Indo-Europeans established themselves as upper castes among this already developed caste-like class structure within the tribes.

Chromosomes, Human, Y↗
PubMed1998

Radiolucent casting tape allows for accurate measurement of forearm bone mineral density using dual-energy X-ray absorptiometry.

The ability to perform dual-energy X-ray absorptiometry (DXA) while a patient is in a cast would give investigators the opportunity to follow early changes in bone mineral density (BMD, g/cm2) during fracture healing or to evaluate bone changes related to immobilization. The objective of this study was to determine if accurate and precise DXA scans could be obtained through polyester-based radiolucent casting tape (Delta-Cast Elite [DCE], Johnson & Johnson, Inc., Raynham, MA) and standard fiberglass casting tape (Delta Lite [DL], Johnson & Johnson, Inc.). DXA scans were performed using a Lunar DPXL densitometer. Standard forearm regions of interest were analyzed. Ten normal volunteers had three consecutive scans of their dominant arm with no cast, with a radiolucent (DCE) cast, and with a fiberglass (DL) cast. Precision was calculated using data from three volunteers (three scans each; no cast, DCE, DL). Results of DCE and DL were compared with results with no cast. In a second series, a spine phantom was placed inside rice-filled forearm casts and repetitively scanned; results with DCE and DL were compared with the mean BMD values for the phantom alone. Analyses of the scans through the DL casts were difficult because the radiodensity of the fiberglass interfered with edge detection. This problem was exacerbated by low BMD (i.e., scans for women). Edge detection was not a problem with the DCE scans. Although the group mean BMD values with in vivo no cast, DCE, or DL scans were similar for all regions of interest, the data obtained for ultradistal regions of interest with DL scans were less precise. BMD values for the fiberglass-encased phantom were significantly lower compared with no cast or DCE scans (p = 0.0002). This study demonstrates that it is possible to perform accurate and precise forearm DXA scans through polyester-based radiolucent DCE casting tape.

Journal Article↗
PubMed2001

Fit of implant-supported fixed prostheses fabricated on master casts made from a dental stone and a dental plaster.

STATEMENT OF PROBLEM: The impression and cast on which an implant-supported fixed prosthesis is fabricated must accurately reproduce the intraoral relations. PURPOSE: The fit of fixed prostheses fabricated on master casts poured in a conventional die stone and in an ultra-low-expansion plaster was investigated in vitro. MATERIAL AND METHODS: An impression was made of patient replicas with inter-implant abutment distances of 50 and 35 mm. Ten master casts were poured in a conventional die stone (Velmix, Kerr) and 10 in an ultra-low-expansion plaster (Gnathostone, Zeus). A simulated plaster fixed prosthesis was fabricated on each master cast and then returned in a random order to the appropriate patient replica. The fixed prostheses were screwed into place on one abutment with a torque of 10 Ncm. Vertical discrepancies were measured at the other abutment by an operator blinded to the cast on which the fixed prosthesis was fabricated. A 2-way analysis of variance was performed for distance and materials, and significant differences were identified with regression analysis. RESULTS: For the 50-mm inter-abutment distance, die stone master casts produced a mean vertical discrepancy of 80 microm (SD 32.50 microm). Plaster master casts produced a mean vertical discrepancy of 42.8 microm (SD 12.17 microm). The means were significantly different (P=.01). For the 35-mm inter-abutment distance, the mean vertical discrepancy produced from the die stone and plaster master casts was 84.33 microm (SD 49.9 microm) and 0 microm (SD 0), respectively. The means were significantly different (P<.001). A significant difference was found between the mean vertical seating discrepancies of fixed prostheses produced from plaster casts with inter-abutment differences of 50 mm and plaster casts with inter-abutment distances of 35 mm (P=.003). No significant differences were found between mean vertical seating discrepancies for fixed prostheses fabricated on die stone casts. CONCLUSION: In this in vitro study, master casts poured in an ultra-low-expansion plaster limited to a maximum inter-abutment dimension of 35 mm were more accurate than casts with 50-mm inter-abutment spans or those poured in a conventional die stone.

Analysis of Variance↗
PubMed1985

Comparison of accuracy of multiunit one-piece castings.

An investigation was conducted to evaluate the accuracy of one-piece castings of FPDs consisting of three, four, and five units with a ceramometal alloy cast in a large circular ring. A three-piece aluminum mold with stainless steel dies simulating the various lengths of the FPDs was used. A total of 18 castings, six castings for each FPD, were fabricated. Marginal discrepancies of the castings on the dies and the length of the castings were compared before and after sectioning the castings at the connectors. The following conclusions were drawn from the study. Seating of the castings improved approximately 50% after sectioning, which indicates that the castings were distorted. The distortion was a three-dimensional phenomenon, with the greatest discrepancy on the mesiogingival surface of the anterior retainer and on the distolingual surface of the posterior retainer. The distortion was least for the three-unit FPDs and greatest for the five-unit FPDs. The lingual-facial diameter of the castings at the gingival axial line angle was significantly larger than the dies in most cases. The mesiodistal diameter of the castings at the gingival axial line angle was smaller than that of the dies but was only significant with the three-unit FPDs. Although the castings were slightly oversized or undersized, the primary reason the castings did not seat was warpage.

Dental Alloys↗
PubMed2004

Effect of initial weight-bearing in a total contact cast on healing of diabetic foot ulcers.

BACKGROUND: Although total contact casts are highly effective in the treatment of plantar ulcerations in patients with diabetes mellitus, they are not widely used. One reason for this lack of acceptance may be the difficulty in complying with an initial period of non-weight-bearing, as is generally recommended by physicians. We performed this study to assess the effects of early weight-bearing on the healing rates of plantar ulcers in patients with diabetes who were wearing a total contact cast. METHODS: Forty patients with diabetes mellitus who had a noninfected forefoot or midfoot ulcer were treated with total contact casts until healing or for thirteen weeks. The patients were instructed to bear no weight on the cast for forty-eight hours after it was applied. Using an embedded step counter, we measured the number of steps taken during the first twenty-four and forty-eight hours, the first week, and each subsequent two-week period after application of the cast. We removed the cast, measured the radius of the ulcer, and then reapplied the cast at the end of the first week and of each subsequent two-week period after cast application until the ulcer healed or for thirteen weeks. We then determined the effect of the number of steps during various time intervals on the rate of ulcer healing (defined as a change in the ulcer radius). RESULTS: Most patients walked on the cast in the immediate postoperative period. The effects of modest amounts of early weight-bearing on ulcer healing rates appear negligible. Only excessive walking during the first twenty-four or forty-eight hours after cast application is likely to prolong the duration of cast treatment. CONCLUSIONS: Moderate early weight-bearing retards healing of plantar ulcers only minimally in patients with diabetes mellitus treated with total contact casts. Allowing patients to walk immediately after placement of a total contact cast may improve their acceptance of this form of therapy. LEVEL OF EVIDENCE: Therapeutic study, Level II-1 (prospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

Adult↗
PubMed1990

Scanning electron microscopy of vascular corrosion casts--technique and applications: updated review.

The present paper states very briefly the main steps leading to the technique of scanning electron microscopy (SEM) of vascular corrosion casts. From the terms presently used (injection method, microcorrosion cast, injection replica, vascular corrosion cast, vascular cast) the use of "vascular corrosion cast" for lymphatic and blood vessels is recommended. Specification and pretreatment (kind, volume, dosage of anticoagulants, vasoactive substances and spasmolytica used) of the animals examined are referenced as they are available from the literature. The recommendation is given to pay more attention to these parameters than done so far. The steps necessary for producing reasonable and suitable vascular corrosion casts are critically described. Special attention is paid to the physical and chemical properties of the casting media and their significance for polymerization, shrinkage, casting quality, corrosion resistance, and thermal and spatial stability. Emphasis is also focused on the advantages of cutting the vascular corrosion casts embedded in an ice block by a band saw, a self constructed multi-blade cutting device or a mini wheel-saw placed in the chamber of a cryomicrotome. From the drying methods presently used freeze-drying is stressed because of minimal specimen damage. To render casts conductive in most cases sputter-coating is sufficient. It is recommended to run the SEM with 5-10 kV since the resolution received still reveals all details the casting media presently can replicate. Further the application of scanning electron microscopy of vascular corrosion casts in fully differentiated normal tissue, in pathologic tissue as well as in developing tissues and organs is stated. Lastly possibilities and conditions are discussed under which SEM of vascular corrosion casts can serve to quantify vascular structures in order to make the technique more than pure descriptive.

Animals↗
PubMed1978

[On deffect of cobalt-chromium-nickel alloy for dental castings (author's transl)].

We studied about castability and microporosity of cobalt-chromium-nickel alloy for dental casting in various methods of fusion and casting. The combinations of fusion and casting were induction fusion and centrifugal casting, arc discharge fusion and argon gas pressure casting and oxy-acetylene flame fusion and centrifugal casting. The following results were obtained. 1. The amount of microposity was smaller, when only mold temperature was low, and as mold temperature and casting temperature were high, castability was better. 2. The arc discharge fusion and argon gas pressure casting was the best method about castability and microporosity in three methods. Second method was the induction fusion and centrifugal casting. 3. In the induction fusion and centrifugal casting, blowing arong gas of 1 l/min to molten metal to protect the metal from oxidization improved the castability the best, but amount of microporosity was large, so that it was needed to lower the mold temperature in this condition. 4. The oxyacetylene flame fusion and centrifugal casting was not suitable for the casting of Co-Cr alloy "Regalloy No. 3", for the alloy was made for the induction fusion casting.

Chromium Alloys↗
PubMed2000

Sorption of atrazine and metolachlor by earthworm surface castings and soil.

Atrazine and metolachlor were more strongly retained on earthworm (Lumbricus terrestris L.) castings than on soil, suggesting that earthworm castings at the surface or at depth can reduce herbicide movement in soil. Herbicide sorption by castings was related to the food source available to the earthworms. Both atrazine and metolachlor sorption increased with increasing organic carbon (C) content in castings, and Freundlich constants (Kf values) generally decreased in the order: soybean-fed > corn-fed > not-fed-earthworm-castings. The amount of atrazine or metolachlor sorbed per unit organic carbon (Koc values) was significantly greater for corn-castings compared with other castings, or soil, suggesting that the composition of organic matter in castings is also an important factor in determining the retention of herbicides in soils. Herbicide desorption was dependent on both the initial herbicide concentration, and the type of absorbent. At small equilibrium herbicide concentrations, atrazine desorption was significantly greater from soil than from any of the three casting treatments. At large equilibrium herbicide concentrations, however, the greater organic C content in castings had no significant effect on atrazine desorption, relative to soil. For metolachlor, regardless of the equilibrium herbicide concentration, desorption from soybean- and corn-castings treatments was always less than desorption from soil and not-fed earthworm castings treatments. The results of this study indicate that, under field conditions, the extent of herbicide retention on earthworm castings will tend to be related to crop and crop residue management practices.

Acetamides↗
PubMed1995

The effect of potential investment expansion and hot strength on the fit of full-crown castings made with a gypsum-bonded investment.

OBJECTIVES: It has been claimed that the strength of the investment mold at the casting temperature affects the dimensional accuracy of castings (e.g., Markley, 1953; Earnshaw, 1957; Asgar, 1972), but the relationship has not been studied quantitatively. In this investigation, the effects of both mold expansion and hot strength on the relative inaccuracy of full-crown castings have been measured and analyzed. The likelihood that a strong investment could cause distortion of the casting by non-uniform restriction of casting shrinkage (Earnshaw, 1969b) was also considered. METHODS: Castings were made with a commercial gypsum-bonded inlay investment, used both as supplied and with modifications that increased its expansion and reduced its hot strength. In both series of tests, the investments were used over a wide range of liquid/powder (L/P) ratios in casting rings fitted with dry ceramic liners, and set under dry conditions. RESULTS: Casting inaccuracy showed a significant linear correlation with total expansion and a highly significant linear correlation with the combination of total expansion and hot strength. The modified investment, with its low hot strength, gave less distortion of casting shape than did the much stronger unmodified material. However, it was found that to ensure sound castings, the hot compressive strength should not be less than 1.8MPa. SIGNIFICANCE: This investigation showed that while investment expansion is the major variable affecting casting inaccuracy, hot strength is an important modifying factor which also has to be considered when predicting casting inaccuracy from measured properties of the investment.

Calcium Sulfate↗
PubMed2006

Over-refractory casting technique as an alternative to one-piece multi-unit fixed partial denture frameworks.

STATEMENT OF PROBLEM: Soldering has been suggested to achieve acceptable fit of multi-unit fixed partial denture (FPD) frameworks of 3 or more elements. However, distortion of the entire framework may occur. PURPOSE: The purpose of this study was to evaluate marginal fit in 1-piece-casting FPD frameworks comparing 2 casting techniques: the conventional technique (CT) and the over-refractory technique (ORT). The techniques were evaluated on castings made from commercially pure titanium (CP Ti; Tritan), titanium-aluminum-vanadium (Ti-6Al-4V), and nickel-chromium (Ni-Cr; VeraBond II) alloys. MATERIAL AND METHODS: A metal master cast including 3 preparations was created to simulate a 5-unit FPD. The metal cast was duplicated in vinyl polysiloxane for fabrication of 60 working casts. For the CT, 0.7-mm-thick patterns were waxed on the casts using an electrical wax-dipping unit. Patterns were removed from the preparations before investing. For the ORT, the silicone impressions were poured with an investment material (Rematitan for CP Ti and Ti-6Al-4V, and Talladium for Ni-Cr). The patterns were waxed on the refractory casts, and the assembly was invested. Both CT and ORT (n = 10), CP Ti, and Ti-6Al-4V frameworks were cast using an arc-melting titanium vacuum-casting machine. The Ni-Cr frameworks were cast using an automated centrifugal-casting machine. The mean marginal discrepancies of the frameworks were measured at the mesial, distal, buccal, and lingual interfaces. Marginal gap measurements were recorded 3 times for each surface to the nearest 0.5 microm using a traveling microscope (x50). The data were analyzed with 2-way analysis of variance, followed by the Tukey HSD test (alpha=.05). RESULTS: Marginal discrepancies for the ORT specimens (82.8 +/- 1.7 microm for CP Ti; 64.4 +/- 1.3 microm for Ti-6Al-4V; and 77.2 +/- 1.5 microm for Ni-Cr) were significantly lower than those obtained for the CT specimens (106.3 +/- 2.6 microm for CP Ti; 75.7 +/- 0.8 microm for Ti-6Al-4V; 101.9 +/- 1.7 microm for Ni-Cr) (P < .05). For both techniques, marginal discrepancies were significantly different among the alloys evaluated, presenting the following order from greatest to least marginal discrepancy: CP Ti, Ni-Cr alloy, and Ti-6Al-4V (P < .05). CONCLUSION: The ORT for multi-unit FPD frameworks demonstrated significantly lower marginal discrepancies than the CT.

Alloys↗
PubMed2000

Dimensional accuracy of castings produced with ringless and metal ring investment systems.

STATEMENT OF PROBLEM: The ringless casting procedure is in use in clinical dentistry, although there is no adequate scientific data to support its use. PURPOSE: This study compared the vertical margin accuracy of lost wax castings produced with the conventional casting technique using a metal ring and a technique that uses a ringless system. MATERIAL AND METHODS: From copings fabricated on a metal die, 30 castings were produced from a high palladium alloy for metal ceramic restorations (Argedent). Ten castings were cast with Bellavest T (Bego) phosphate-bonded investment with the ringless technique, 10 were cast with the same investment with a metal ring, and the final 10 were cast using Hi-temp (Whip Mix) phosphate-bonded investment with a metal ring. The internal surface of the castings were not modified before seating with finger pressure. For vertical margin discrepancy measurements, an optical microscope at a magnification of 100x was used. Data were analyzed with 1-way multivariate ANOVA (repeated measures) and the Student-Newman-Keuls test. RESULTS: When following the manufacturers' recommendations, the castings of the ringless technique provided less vertical margin discrepancy (mean value 181 +/- 71 microm) than the castings produced with the conventional metal ring technique (290 +/- 87 microm and 291 +/- 88 microm). The difference was significant (P <. 001). CONCLUSION: The ringless technique may produce accurate castings for use in fixed prosthodontics, therefore further investigation is needed to develop a protocol for its use.

Analysis of Variance↗
PubMed1993

A comparison of an accelerated technique for casting post-and-core restorations with conventional techniques.

PURPOSE: This project compares an accelerated technique for the casting of post-and-core restorations with four traditional techniques. The accelerated technique uses two phosphate-bonded investments and the traditional techniques use a gypsum- and a phosphate-bonded investment. The study measures and compares the differences between the seating of the casting and the seating of the acrylic resin pattern. The effects of the techniques on the fit of castings with and without a ferrule are also compared. MATERIALS AND METHODS: Six groups of 10 castings were made from plastic patterns formed on a stainless steel test die. A different investment and/or burnout method was used for each group. Each group had two subgroups: ferruled and nonferruled. The fit of the plastic patterns was measured at two time intervals after forming, 2 weeks and 3 months. The patterns were invested immediately after the 3-month measurement, and the difference in fit of the castings was calculated. An ANOVA and Tuckey-Kramer test were done to determine the statistical validity. RESULTS: The seating of the patterns after 3 months of storage was consistently worse than the 2-week measurements of fit. The ferrule and nonferrule patterns were not statistically different in seating. Measurement of the castings showed that the ferruled castings seated significantly worse than the nonferrule castings. The difference in the seating of the castings as compared with the patterns was considered clinically unacceptable, showing a range of 0.301 mm to 0.528 mm. The nonferrule castings showed a significant difference in seating among groups. The difference ranged from -0.099 mm to 0.322 mm. CONCLUSIONS: The castings of the ferrule subgroups were considered clinically unacceptable and were not analyzed for significance. Among the nonferrule castings, the group using a gypsum investment and conventional technique for investing and burnout but no ring liner showed the best seating. The accelerated technique was intermediate in seating with a difference of 0.148 mm from the seating of the patterns. This group was significantly different from the two best groups but not from the remaining three groups.

Analysis of Variance↗
PubMed1998

Determination of gold alloy loss during the production of cast dental restorations.

Values for the loss of high gold content dental alloy during the fabrication of three types of cast dental restorations were determined. The mass changes measured were for the melting, casting and cleaning processes and the docking and laboratory finishing procedures involved in producing the final restoration. The casting yield from the alloy cast was also determined. Five Brisbane dental laboratories participated and 407 cast restorations were assessed. The mean mass loss for the melting and casting process was 0.109 g (SD 0.326) per cast restoration, and 0.827 per cent (SD 1.805) of the total mass of alloy melted. The data were analysed in four categories: alloy crowns, metal-ceramic crowns, metal-ceramic bridges, and combined. The mean total mass loss per restoration from docking and finishing for each of the four groups of cast dental restorations examined was 0.329 g, 0.350 g, 0.927 g and 0.363 g; 13.11, 28.30, 22.07 and 22.18 as a per cent of the mass of the docked casting respectively. The yield of casting masses from the alloy cast were 19.97, 9.11, 29.10 and 13.71 per cent respectively, with all differences significant at the 0.001 level. These values indicate that the recommendation for 50 per cent addition of new alloy for each cast is impractical. The wide spread of the data precludes the establishment of a precise agreed value between dentists and technicians for expected loss. However, the use of the median or mean would provide a value which might be an equitable indicator in the long term. Alternatively, working values can be developed for individual dentist/technician partnerships.

Crowns↗
PubMed1989

Studies of Ti alloys for dental castings.

Casting of Ti has been recently investigated in dentistry. The purpose of this study was to examine the alloying effect on the cast Ti. Metallurgical structures, mechanical properties, and in vitro corrosion resistance were, therefore, studied for cast Ti and for four selected cast Ti alloys such as Ti-6AI-4V, Ti-15V, Ti-20Cu, and Ti-30Pd. A "Castmatic" dental casting machine was utilized, which involved argon-arc melting and subsequent argon/vacuum-pressurized casting. The photomicrographs revealed quite large grains in the cast structures. XRD analyses on cast Ti metals showed the quasi-equilibrium phases present. The strength of cast Ti could be significantly increased by alloying. Cross-sectional microhardness measurements of cast Ti alloys showed U-type hardness distribution due to the surface mold reaction. All the cast Ti alloys examined showed a strong passivity trend in the corrosion test. The present results suggest that cast Ti alloys have promising features for future dental uses.

Dental Alloys↗
PubMed2003

Semi-rigid vs rigid glass fibre casting: a biomechanical assessment.

OBJECTIVES: To determine if semi-rigid synthetic casts provide any measurable advantages compared to rigid synthetic casts. BACKGROUND: Glass fibre bandages are now commonly applied immediately post-injury to provide rigid immobilisation of the limb, for both weight bearing and non-weight bearing casts. However, composite casts that have inherent flexibility are also available and it is claimed they provide some functionality. METHODS: Five members of the orthopaedic department each applied a rigid and a semi-rigid below elbow (Colles) and a below knee walking cast to a single volunteer subject. Joint immobilisation and functional movement was assessed using electrogoniometry and limb support using pressure transducers. RESULTS: Semi-rigid Colles casts provided slightly greater immobilisation at the wrist while allowing full finger function and greater support to the forearm during hand movements. Similarly, semi-rigid below knee walking casts produced greater immobilisation at the ankle while allowing more forefoot movement and were less of an impediment to walking. CONCLUSIONS: Semi-rigid casting techniques have measurable advantages compared to rigid synthetic casts and represent a further development in the conservative management of fractures and soft tissue injuries. RELEVANCE: Semi-rigid casting is a relatively new technique that can reduce some of the problems of rigid cast immobilisation and could potentially shorten the rehabilitation phase following injury. Information about the performance of these casts to assess their value in specific applications is very limited.

Ankle Injuries↗
PubMed2002

Effectiveness of serial casting in patients with severe cerebral spasticity: a comparison study.

OBJECTIVE: To compare the improvement and complication rate between a technique using a short casting interval and a more conventional changing interval. DESIGN: A retrospective case-comparison study. SETTING: A rehabilitation center for adults with neurologic disorders. PARTICIPANTS: One hundred five patients with cerebral spasticity of different etiologies treated with serial casting to relieve fixed contractures caused by increased muscle tone. INTERVENTION: Serial casting of 172 joints (42 elbow, 41 wrist, 21 knee, 68 ankle joints), with cast-changing intervals of 5 to 7 days (group 1:92 joints, 56 patients), or 1 to 4 days (group 2:80 joints, 49 patients). MAIN OUTCOME MEASURES: Percentage of normal maximum range of motion (ROM) at the completion of casting and 1 month after discontinuation, and the number of complications resulting from casting procedure. RESULTS: Improved percentage ROM immediately after serial casting and 1 month later in both groups (F=1469.5, P<.001). No differences in ROM improvement between groups were observed (F=0.3, P=.72). Complications in serial casting were found in 19.8% of 172 casting procedures, in 29.3% in group 1 and in 8.8% in group 2 (chi(2)=10.2, P=.001). Discontinuations of treatment because of casting complications or other reasons were observed in 12.8% of the entire sample, in 18.5% in group 1 and in 6.3% in group 2 (chi(2)=4.7 P=.03). CONCLUSION: Casting is effective in the treatment of fixed contractures of the upper and lower extremities caused by increased muscle tone of cerebral origin. Short changing intervals in serial casting provide improvements in ROM comparable with conventional changing intervals, and result in fewer complications.

Adult↗