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PubMed1992

The influence of casting methods on the surface microhardness and crystalline formation of aluminum-copper alloys.

The influence of air/gas, oxygen/gas, and electric casting methods on the surface microhardness and crystalline formation of three aluminum-copper alloys was verified. The inclusion, wax elimination, and casting of the pattern were accomplished by using conventional techniques for thermal expansion investment. After metalographic polishing, the surface hardness analysis was verified with a penetrator. The penetrations were transformed in Knoop hardness with the conversion table, and computed by variance analysis. The test sample surfaces were then etched with a reactive solution composed of equal parts of hydrogen peroxide and ammonium hydroxide. The crystalline grains precipitated by solution were photographed with Kodak film 32 ASA. The results demonstrated that the surface microhardness of the alloys was modified according to the heat sources used, and the crystalline grain disposition was also adversely influenced by the heat sources, with the exception of Goldent alloy.

Acid Etching, Dental↗
PubMed1992

The effect of a surface disinfectant on a dental cast.

This study determined the effect of a disinfectant solution on dental casts. Stone samples were immersed in a disinfectant solution and in control solutions. The results indicate that a saturated calcium sulfate (clear slurry) solution with 0.525% sodium hypochlorite was an effective disinfectant and acted without damage to the dental cast.

Calcium Sulfate↗
PubMed1994

Gold alloy cast to base metal removable partial denture frameworks.

For many years, gold and base metal alloys have been used in the construction of cast removable partial dentures. Each alloy has desirable properties, yet neither is ideally suited for all portions of a framework. A method has been developed to fabricate prostheses by casting gold alloy against a base metal alloy. This procedure allows the practitioner to combine the favorable characteristics of both alloys within a single framework. Consequently, the practitioner may create frameworks that more effectively meet the biomechanical demands of the oral environment.

Dental Alloys↗
PubMed1994

Effect of impression materials and techniques on the marginal fit of metal castings.

The effect of two impression materials used in three different techniques was tested for the accuracy of the marginal fit of metal castings. Sixty identically prepared Ivorine teeth were divided into groups of 20. The following methods were selected to make impressions: (1) putty in a metal stock tray with simultaneous elastomeric impression wash, (2) copper band relined with autopolymerizing acrylic resin and subsequent light-body elastomeric impression material, and (3) copper bands with modeling compound. Faciolingual sections of the Ivorine teeth with cemented metal castings were examined by scanning electron microscopy (SEM) at x 100 magnification. Measurements of the thickness of cement layers were calculated both manually and by use of a recently developed computerized method. The differences in the gingival marginal gaps between various impression materials and techniques at both the facial and lingual surfaces were not statistically significant.

Acrylic Resins↗
PubMed1989

Mesh monitor casting of Ni-Cr alloys: element effects.

A mesh monitor has previously been used for quantitative evaluation of the casting of dental alloys. A castability value, Cv was defined. For curve-fitting, a transformed castability value, Cv,t, was used. A series of alloys was selected so that effects of major elements on Cv, t and, hence, on Cv could be determined. Compositions were chosen so that correlated effects would be avoided. Assuming a linear dependence on the concentrations of individual elements, one may use the following equation to describe Cv,t: (Formula: see text) where each term employs an elemental concentration in weight percent, (Ei), and a coefficient, Ki, for the ith term. Because Ei's are constant for each alloy, Ki = fi (TA, TM) = gi (TC, TM). The temperature-dependent coefficients, Ki, were determined for seven elements and for the (Ni/(Cr) ratio. It was also found that Si and Be produce a synergistic effect. The results help our understanding of the casting behavior of Ni-Cr dental alloys; this approach may be useful in the design of dental alloys.

Chromium Alloys↗
PubMed1985

Energy of gait in below-knee casts with different soles.

This study aims to provide some guidelines for the use of soles on below-knee walking casts. Whole-body energy changes during the single limb support phase of the gait cycle have been quantified in twenty volunteer subjects fitted with below-knee casts and each wearing one of five soles in turn. Simple gait analysis was carried out with a Kistler force plate and an Apple II microcomputer, the data were sampled at 50 Hz. Three commercial soles and two 'home made' ones were used; it was generally found that the commercial products produced a more energy efficient gait. Some recommendations are included regarding the design of soles to be used in this clinically demanding situation.

Adult↗
PubMed1992

Treatment of scaphoid nonunion with casting and pulsed electromagnetic fields: a study continuation.

This article presents a continuation of a study of the treatment of scaphoid nonunion with pulsed electromagnetic fields (PEMF) and cast immobilization. Fifty-four patients were reviewed. The overall success rate for healing has decreased since the previous review from 80% to 69%. Proximal pole fractures healed in 50%. Success in nonunions with associated radiographic evidence of avascular necrosis decreased from 89% to 73%. Although we believe that the indications for use of PEMF have not changed significantly, this study suggests that a successful outcome with PEMF and casting is less likely than previously reported. We believe that until additional clinical studies have further defined the indications, treatment protocol, and efficacy of this method PEMF treatment should be a secondary alternative to bone-grafting procedures.

Adolescent↗
PubMed2005

Slipper cast management of emergency foot problems.

Foot conditions are frequently seen in the emergency department. In many cases, although weight bearing is painful, it is not precluded, per se. When a soft dressing does not provide sufficient support, a below knee walking cast may be applied. We present an alternative dressing that may be of benefit in selected foot injuries. The dressing is fashioned with cast padding, foam sheeting and plaster. It is designed and molded to fit like a slipper. The plaster slipper has distinct advantages in that it is comfortable, lighter for the patient, and avoids the problem of ankle stiffness. We believe that this option is underused in the emergency setting.

Ankle↗
PubMed2004

Casting alloys.

Although the role of dental casting alloys has changed in recent years with the development of improved all-ceramic materials and resin-based composites, alloys will likely continue to be critical assets in the treatment of missing and severely damaged teeth. Alloy shave physical, chemical, and biologic properties that exceed other classes of materials. The selection of the appropriate dental casting alloy is paramount to the long-term success of dental prostheses,and the selection process has become complex with the development of many new alloys. However, this selection process is manageable if the practitioner focuses on the appropriate physical and biologic properties, such as tensile strength, modulus of elasticity,corrosion, and biocompatibility, and avoids dwelling on the less important properties of alloy color and short-term cost. The appropriate selection of an alloy helps to ensure a longer-lasting restoration and better oral health for the patient.

Biocompatible Materials↗
PubMed2005

Ion release from dental casting alloys as assessed by a continuous flow system: Nutritional and toxicological implications.

OBJECTIVES: The aims of this study were to quantify the metallic ions released by various dental alloys subjected to a continuous flow of saliva and to estimate the nutritional and toxicological implications of such a release. METHODS: Four pieces of three nickel-based, one noble, one high-noble and two copper-aluminum alloys were cast and then immersed in a continuous flow of artificial saliva for 15 days. To simulate three meals a day, casts were subjected to thrice-daily episodes, lasting 30 min each and consisting of pH decreases and salinity increases. After 15 days, the metallic ions in the artificial saliva were analyzed. Data were expressed as averaged release rate: microg/cm2/day of ion released for each alloy. The highest value of 95% Cl of each ion was adapted to a hypothetical worst scenario of a subject with 100 cm2 of exposed metal surface. The results were compared with the tolerable upper daily intake level of each ion. RESULTS: The copper-aluminum alloys released copper, aluminum, nickel, manganese and iron. The nickel-based alloys essentially released nickel and chromium, while the beryllium-containing alloy released beryllium and significantly more nickel. The noble and high-noble alloys were very resistant to corrosion. The amount of ions released remained far below the upper tolerable intake level, with the exception of nickel, released by beryllium-containing nickel-based alloy, whose levels approach 50% of this threshold. SIGNIFICANCE: The daily amount of ions released seems to be far below the tolerable upper intake levels for each ion.

Corrosion↗
PubMed2006

(31)P solid-state MAS-NMR spectroscopy of the compounds that form in phosphate-bonded dental casting investment materials during setting.

OBJECTIVES: To use (31)P solid-state MAS-NMR to determine which compounds form in phosphate-bonded dental casting investment material during setting, when the ambient temperature is altered. To determine whether they differ in material originating at the center of the mix from material that adheres to the mixing bowl wall. METHODS: (1)H high powered decoupled (HPDC) and (1)H cross polarized (CP) (31)P solid-state MAS-NMR spectroscopy were used at a resonance frequency of 121.4MHz to determine molecular structure. Four commercial products were examined. Manufacturer's instructions were followed and special liquid used without dilution. Ambient temperature was between 18 and 37 degrees C. RESULTS: Molecular structures change with ambient temperature and product. Amorphous Mg(3)(PO(4))(2) or struvite dominate with newberyite, cattiite, amorphous Mg(2)P(2)O(7) and amorphous MgHPO(4) present as minor phases. Exceptionally, amorphous MgHPO(4) dominates. Differences in structure were found in material taken from the center of the mix compared with that scraped from the bowl wall, but the incidence may be specific to the product/mixer combination and not a general effect. SIGNIFICANCE: The formation of compounds in phosphate-bonded investment can be affected by ambient temperature. This effect and the use of material adhering to the bowl wall (instead of that from the center of the mix) are possible causes for the unpredictability of setting expansion measurements between laboratories. There is variation between products. When phosphate-bonded investment is required for casting, a consistent ambient temperature must be used and it would be wise to mix sufficient material to avoid scraping the bowl.

Dental Casting Investment↗
PubMed2005

Functional treatment of acute metatarsal fractures: a prospective randomised comparison of management in a cast versus elasticated support bandage.

A randomised controlled trial was performed in 50 patients with acute isolated minimally displaced lesser metatarsal fractures in order to compare plaster immobilisation with elasticated support bandage treatment. Patients treated with elasticated support bandage had significantly higher AOFAS mid-foot scores at 3-months follow-up and complained of less pain throughout the treatment period. There was no difference between the two groups in time to independent mobility, mid-foot circumference, analgesic requirements and radiological union at 3 months. As plaster casts are associated with serious complications, which were encountered in these studies, we conclude that minimally displaced metatarsal fractures are better treated without a cast.

Adolescent↗
PubMed2006

Thromboprophylaxis following cast immobilisation for lower limb injuries--survey of current practice in United Kingdom.

The risk of deep vein thrombosis (DVT) and pulmonary embolism (PE) is well documented in patients following cast immobilisation for injuries of lower extremities. There are no generally accepted approaches to preventing this complication and hence there remains substantial practice variation amongst surgeons regarding the use of anticoagulation measures. The present survey was conducted to investigate the current chemothromboprophylaxis practice among UK orthopaedic departments for patients immobilised with plasters for lower extremity injuries and establish any variations in practice. A telephone questionnaire survey was conducted on junior doctors (Senior House Officers and Registrars) in orthopaedic departments of 70 randomly selected hospitals in United Kingdom. This survey assessed the thromboprophylaxis practice for lower limb injuries in plaster casts. Our results show substantial variation amongst British orthopaedic surgeons in the use of chemothromboprophylaxis measures. Sixty-two percent of the departments do not use any DVT prophylaxis in this group of trauma. Furthermore, only 11.4% of the departments performed risk stratification on their patients. Ninety-nine percent of the respondents were unaware of any existing guidelines in this regard. Although the incidence of DVT in patients in plaster for lower extremity injuries is low compared to the Hip/Knee arthroplasty group, this is not insignificant. Both over and under treatment with thromboprophylaxis can have implications in terms of side effects and costs. One possible solution is to use risk stratification to identify individuals who are likely to benefit from prophylaxis. There is a substantial variation and inconsistency in practice among orthopaedic departments in United Kingdom due to a lack of clinical guidelines in this group of trauma and it remains underused even in high-risk group.

Anticoagulants↗
PubMed2006

An evaluation of the performance of cast gold bonded restorations in clinical practice, a retrospective study.

OBJECTIVES: To evaluate the performance of cast gold bonded restorations in clinical practice. MATERIALS AND METHODS: The records of all patients treated with cast gold bonded restorations between 1997 and 2004 of The Dental Hospital of Newcastle upon Tyne were reviewed. The following data were recorded: sex of patient, location of teeth (anterior or posterior), position of teeth (upper or lower) and type of cement (glass ionomer, zinc phosphate or resin cement). The survival time was calculated for each restoration; and the reason for failure (either debond or change of treatment plan) identified for each case. The restorations were stratified according to the age of the patient into 10-year age bands and survival analysis was used to identify variables associated with increased risk of failure. RESULTS: Restorations luted with resin cement showed the highest rate of survival after 7 years of follow-up. The alternative lutes had significantly worse survival (p<0.05). Restorations on anterior teeth had poorer survival than on posterior teeth but there were no differences between those placed in the mandible and the maxilla. CONCLUSIONS: Within the limitations of this study resin cements are most appropriate for this type of restoration with 80% survival at 7 years. Restorations placed on posterior teeth survived better.

Adolescent↗
PubMed2004

A prospective study of the treatment of fractures of the little finger metacarpal shaft with a short hand cast.

This prospective study describes the use of a short hand cast, which leaves the finger metacarpophalangeal and wrist joint free, for angularly displaced little finger metacarpal shaft fractures which require reduction. Twenty-seven patients with a mean age of 25 (range, 16-39) years with little finger or combined ring and little finger displaced metacarpal shaft fractures were prospectively recruited. All were treated by closed fracture reduction and immobilization in the cast. Patients were followed up at 1 week, 4 weeks, and between 6 and 12 months. At each of these follow-up visits posteroanterior and lateral radiographs of the metacarpals were performed to assess angulation of the fracture. The mean initial angulation of the 17 little finger metacarpal fractures with complete follow up was 40 degrees (range, 20-60 degrees ). Their mean final angulation at 6 to 12 months was 8 degrees. The fracture reduction was lost in three patients in whom the final angular deformities were 15 degrees (one patient) and 20 degrees (two patients). Journal of Hand Surgery (British and European volume, 2004)

Adolescent↗
PubMed2006

Marginal accuracy of titanium copings fabricated by casting and CAD/CAM techniques.

STATEMENT OF PROBLEM: Advances in computer-aided design/computer-assisted manufacturing (CAD/CAM) technology purportedly enhance the marginal fit of dental restorations. However, little information is available on the marginal accuracy of restorations manufactured with various CAD/CAM systems. PURPOSE: The purpose of this study was to evaluate and compare the marginal accuracy and refinement time of titanium copings fabricated by 3 different CAD/CAM systems relative to standard casting techniques. MATERIAL AND METHODS: Sixty-four stone die duplicates of a human maxillary central incisor, prepared for a metal-ceramic crown, with a uniform chamfer design, were divided into 4 groups (n=16). The specimens were restored with titanium copings using CAD/CAM systems Pro 50 (PRO), DCS (DCS), and Everest (EVE). A conventional titanium casting technique, Biotan (BIO), served as a control. Vertical and horizontal discrepancies between restoration margins and the preparations were each measured before and after manual refinement. This refinement was completed using a disclosing agent and by removing the internal positive defects of the copings. The marginal discrepancies of the copings were evaluated at 4 standard areas using 10 measurements, for a total of 160 measurements of each margin. Repeated-measures ANOVA was used for analyzing marginal accuracy. The coping refinement time was analyzed with the Kruskal-Wallis and post hoc Wilcoxon rank sum tests (alpha=.05). RESULTS: The marginal discrepancies (microm) ranged from 32.9 to 127.8 before and from 3.4 to 58.4 after the manual refinement of copings. Manual refinement significantly improved the marginal accuracy (P<.0001) when compared with the initial fabrication. The relative (%) gain of marginal accuracy was PRO, 74.1%; DCS, 69.7%; EVE, 68.7%; and the control, BIO, 69.2%. The median duration of manual refinement time in minutes was 6.0 for PRO, 9.5 for DCS, 4.0 for EVE, and 4.0 for BIO (Kruskal-Wallis-test: P<.0001). CONCLUSION: Manual adjustment significantly improves the marginal accuracy of CAD/CAM system-fabricated titanium copings. The highest marginal accuracy was achieved with the DCS system, using a longer refinement time.

Analysis of Variance↗
PubMed2001

Dynamised cast management of Achilles tendon ruptures.

Non-operative treatment of closed ruptures of the Achilles tendon within 48 h of injury has been shown to produce results comparable with surgical treatment [1,2]. We report 49 patients treated using a dynamised cast, with a mean follow-up of 42 months, in which there has been only one case of re-rupture. A total of 33 patients were reviewed clinically and measurements revealed a mean calf circumference deficit of 1 cm and a mean functional range of ankle motion deficit of 3 degrees and plantar-flexion strength of 81-90%, when compared with the contra-lateral uninjured limb. Early mobilisation of the injured Achilles tendon using a dynamised cast has produced a re-rupture rate and functional recovery that compare favourably with previously published results for patients treated operatively. Non-operative management, in this way, is well tolerated by patients and is of low cost.

Achilles Tendon↗
PubMed1978

Fractures of the tibial shaft treated in a patellar-tendon-bearing cast.

A retrospective review of fractures of the tibial shaft treated in patellar-tendon bearing (PTB) casts shows that a high rate of union, in respect of both time required and numbers, and a low morbidity can be expected. The method is easy to apply. In those patients who had the casts applied early, once swelling had settled down, the fractures united more quickly.

Adolescent↗