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PubMed1993

[A study of restoration of seriously damaged posterior teeth by cast metal prostheses].

A total of 38 seriously damaged posterior teeth were restored by cast metal prostheses, including onlays (with pulp chamber retainer and radicular retainer), cast dowelcore, two-piece dowel-core or cast dowel crown. As followed up for 6-48 months, 37 prostheses remained firm and sound, with perfect periphery seal, no secondary caries and pathological changes of peridontium were observed, The clinical consummate rate was 97%, The occlusal force of the restored teeth measured in 14 cases was 13.6-30.2 kg, which can satisfy the needs of masticatory function. The selection of retainers should be in accordance with the position and degree of crown damage of the posterior teeth. The key links guaranteeing smooth insertion and perfect periphery seal of cast metal prostheses were also pointed out.

Adolescent↗
PubMed1993

Scanning electron microscopy of styrene-methylethylketone casts of the airway and the arterial system of the lung.

The method of making casts of airways and the pulmonary arterial system using a styrene polymer resin is described. A human and a dog were used as models. The viscosity of this resin ranges between 40 and 60 dPa/s at 24 degrees C. The elastic rubber tube used for resin injection allows a constant perfusion pressure, i.e., 44 mm Hg and 110 mm Hg for airway and vascular filling, respectively. The casts obtained using this method are suitable both for macro- and microscopic analysis. Shrinkage during polymerization is minimal. Moreover, a preceding lavage is not necessary. Scanning electron microscopy (SEM) of cast lungs showed the endothelial cell nuclei imprints on vessels. Computer assisted analysis of alveolar capillary interspaces showed that these holes are larger than those described in normal rats. The diameter of alveolar capillaries in dogs is almost the same as in the normal rat lung. When casting the airways, alveolar cells and/or materials inhaled might be preserved and observed in SEM.

Animals↗
PubMed1997

All-cast-titanium removable partial denture for a patient with a severely reduced interarch distance: a case report.

A patient had a maxillary posterior edentulous area and severely reduced interarch distance that precluded the use of a conventional removable partial denture. An all-cast-titanium denture base and occlusal surface was designed to fabricate a removable denture to restore the edentulous area. Titanium was cast in a centrifugal casting machine with electric are melting design. The desirable characteristics of titanium, such as favorable mechanical properties, low density, and comparatively low cost, make this metal particularly effective and suitable for construction of an all-cast-metal denture base with a metal occlusal surface.

Adult↗
PubMed1997

[Muscular lengthening of the triceps by successive casts in children with cerebral palsy].

PURPOSE OF THE STUDY: Twenty children with cerebral palsy who underwent elongation of the triceps surae using successive plaster-casts (28 short triceps) were reviewed. This study was retrospective. MATERIAL AND METHODS: Among the eighteen children, 10 were hemiplegic, 8 were diplegic and 2 were spastic quadriparetic. All of them except one were ambulatory children. The authors describe their elongation technique by plaster-casts and the treatment they lead. The mean age at time of elongation was 4 years and 6 months (range 2 years 4 months to 8 years). The passive dorsiflexion of the foot before elongation was of 0 degree (range -20 degrees to +10 degrees) knee in extension, and of 5 degrees (range -15 degrees to +15 degrees) knee in flexion. RESULTS: The passive dorsiflexion of the foot after elongation was of 23 degrees (range +10 degrees to +30 degrees) knee in extension, and of 27 degrees (range +10 degrees to +35 degrees) knee in flexion. One major complication was noted: the persistence of a varus foot in child after elongation. 24 elongations were reviewed with a mean follow-up of 21 months (range 12 months to 30 months). The passive dorsiflexion of the foot was of 10 degrees (range 0 degree to +20 degrees) knee in extension and of 17 degrees (range -5 degrees to +25 degrees) knee in flexion. DISCUSSION: Compared to different procedures (surgical lengthening, botulinum-A toxin) elongation by successive plaster-casts is a quick, safe, complication-free, and simple technique, whose results are equivalent. Even if recurrence of equinus is probable, a surgical procedure of lengthening could be made on an operative-free tendon. CONCLUSION: Elongation of the triceps surae muscle by successive plaster-casts constitutes a safe alternative technique compared to surgical procedure.

Achilles Tendon↗
PubMedDate not supplied

[Results of treatment of lower leg fractures with functional lower leg casts].

INTRODUCTION: Problems, consequences and influence of immobilization on tissue and fracture healing, as well as patient's psyche and entire condition of the organism, are well known. With immobilisation patient looses a part of extremity movement. Healing of fractures and remaining tissues is a natural process, so it is usually said that fractures and tissues heal not because of immobilization, but in spite of it. The theory of treating by functional cast (PTB-patellar tendon bearing), firstly described by Sarmiento, is based on tissues natural capability to heal and on its functional guiding to the final cause. The aim of this study is to analyze our previous expirience in regard to this method. MATERIAL AND METHODS: We have studied patients from 7 to 70 years of age with fracture of one or both lower leg bones. After injury, patients were mobilized using upper leg plaster impregned bandages applied to two thirds of extremity's circumference. After X-ray control and locating the position of broken parts, patients were released with thromboprophylaxis using Acetilsalycil acid (Midol) 3 x 1 tablet per day. In some cases, where reduction of broken fragment was hard, total anesthesia was performed. In cases of oblique and spiral fractures, because of possible redislocation we have waited with application of lower leg functional cast up to 3 weeks. RESULTS: We have studied 59 patients, most of them between the age of 11 and 20. In most cases functional cast was applied after 21 to 30 days, fractures healed after 90 to 99 days and the shortening of extremities was clinically non measureable. Usually it was 24 mm. DISCUSSION: Treatment of lower leg fractures is not simple. We especially point to problems with circulation and skin which have to be controlled over and over. There are reports of rejecting operational method as a method for lower leg fracture treating. Our results are the same as those achieved by other authors. Reposition of bone fragments must be performed with special attention. It is best if it is performed during total anesthesia, because muscles are relaxed and therefore circulation gets better, intensity of pain decreases and there are no skin necroses. In few cases, at the beginning of treatment there were skin blisters which only lengthened the treatment. These problems were prevented by early reposition, retention of bone parts and elevation of extremities. CONCLUSION: Lower leg functional cast gives excellent results in treating diaphyseal lower leg fractures. Early mobilization positively influences the patient's psyche and enables quick resocialization. Physical treatment is usually not necessary.

Adolescent↗
PubMed1996

Alterations in equine guttural pouch morphology with head position: observations using a new technique for producing accurate casts.

BACKGROUND: An improved technique for preparing casts of the equine guttural pouch is described. The new technique is simplified and inexpensive in comparison to previous techniques and produces highly accurate anatomic models which are both durable and flexible. METHODS: Silicone rubber bathtub caulk was injected into the guttural pouches of horse cadavers. The silicone was allowed to cure overnight, and casts were removed by dissection. The new technique was then used to evaluate changes in the shape of the guttural pouch with changes in head position. RESULTS: With flexion of the atlanto-occipital joint, the lateral compartment of the guttural pouch in particular was found to change considerably in size in shape. The angle of inclination of the ventral border of this pouch increased with flexion, as did the depth of the impression made by the rostral portion of the stylohyoid bone. In addition, the lateral compartment diminished in thickness rostrally in casts from flexed animals. CONCLUSIONS: The viscous silicone caulk resulted in superior casts of the equine guttural pouch. Observations of changed pouch shape with head position agree well with previous reports of increased difficulty in draining the lateral compartment of the horse's guttural pouch when the head is held in the flexed position.

Animals↗
PubMed1997

Relationship between microstructure and ductility of investment cast ASTM F-75 implant alloy.

Hip replacement implants fabricated using the ASTM F-75 alloy sometimes fail in a sudden catastrophic way. In general, fractures start at microstructural defects subjected to stress-corrosion under chemical attack by body fluids. In this paper the results of a study on the effect of casting parameters on the microstructure of ASTM F-75 are presented. The preheating mold temperature and the liquid temperature were varied between 900 and 1000 degrees C, and 1410 and 1470 degrees C, respectively. Optimum static strength and ductility were obtained when shrinkage microporosity and the volume fraction of M23C6 "eutectic" carbides precipitated at grain boundaries were minimized by increasing the preheating mold temperature to 1000 degrees C and by using intermediate pouring temperatures of 1455 degrees C. Under these casting conditions, however, the solidification rates are low, leading to large grain sizes, which, in turn, reduce the strength of the material under dynamic loading conditions. The volume fraction of the M23C6 "blocky" carbides appears to be independent of the casting conditions; however, their size and spatial distributions determine the strength of the as-cast alloys.

Alloys↗
PubMed1988

Venous valve anatomy and morphometry: studies on the duckling using vascular corrosion casting.

The anatomy and morphometry of venous values associated with the vasculature of the head of the duckling were studied using vascular corrosion casting and scanning electron microscopy. All valves encountered were bicuspid, and casts typically exhibited slight expansions at valve sinuses and deep slits at the sites of valve leaflets. The locations, numbers, and orientations of endothelial nuclei on all surfaces of the valves were clearly revealed by imprints in the casting resin. Endothelial cell densities were significantly higher on the surfaces of valve leaflets (about 10 cells/1,000 micron2) than on other venous surfaces (about 7 cells/1,000 micron2). Endothelial nuclei on the medial surface of the valve leaflet were oriented parallel to the long axis of the vessel, whereas those on the lateral surface were oriented perpendicular to that axis. The close proximities of valves in some vessels and the presence of anomalies such as the sharing of leaflets by adjacent valves were readily demonstrated with the corrosion-casting techniques. These methods provide a useful means for studying the fine, three-dimensional details of venous valve anatomy.

Animals↗
PubMed1981

Running inhibits the reversal of atrophic changes in canine knee cartilage after removal of a leg cast.

The effect of vigorous exercise on the reversibility of canine knee cartilage atrophy produced by immobilization of the leg was studied. In comparison to cartilage from the contralateral control knees, cartilage from knees which had been immobilized in a cast for 6 weeks showed an increase in water content and decreases in thickness, Safranin O staining of the matrix, uronic acid content, and net proteoglycan synthesis. In addition, the ability of both newly synthesized (35S) and total tissue proteoglycans to interact with hyaluronic acid to form aggregates was diminished; this was apparently due to an abnormality in the hyaluronate-binding region of the core proteins. If the casts were removed and the animals were then allowed to ambulate ad libitum for 3 weeks, all of these changes were reversed. However, knee cartilage from 3 dogs which had been run daily on a treadmill (6 miles/day) for 3 weeks after removal of the casts exhibited continuing decreases in thickness, Safranin O staining, and uronic acid content (mean 31%), even though net proteoglycan synthesis was increased (mean 16%) in comparison to that in control cartilage from the contralateral (nonimmobilized) knee. Furthermore, the abnormality in both 35S- and total tissue proteoglycans which precluded their interaction with high molecular weight hyaluronic acid persisted. In this respect, the proteoglycans were indistinguishable from those obtained from knee cartilage immediately following 6 weeks in a cast.

Animals↗
PubMed2002

Effect of chemical composition on the corrosion behavior of Ni-Cr-Mo dental casting alloys.

The objective of this investigation was to study the compositional influence on the corrosion behavior of Ni-Cr-Mo dental casting alloys in acidic artificial saliva. Cyclic potentiodynamic and potentiostatic tests were used to evaluate the corrosion behavior of different Ni-Cr-Mo dental casting alloys in deaerated artificial saliva with pH 5 at 37 degrees C. Optical microscope observations were made following the cyclic potentiodynamic tests. Surface chemical analyses were characterized by X-ray photoelectron spectroscopy and auger electron spectroscopy following the potentiostatic tests. The results show that the corrosion resistance of the Ni-Cr-Mo casting alloys investigated is associated with the formation of passive film containing Ni(OH)(2), NiO, Cr(2)O(3), and MoO(3), on the surface. The pitting potential and passive range, respectively, were statistically different among the different Ni-Cr-Mo alloys. The Ni-Cr-Mo alloys with higher Cr ( approximately 21%) and Mo ( approximately 8%) contents had a much larger passive range in the polarization curve and were immune to pitting corrosion due to the presence of high Cr (maximum approximately 31-35%) and Mo (maximum approximately 12%) contents in the surface passive film. The presence of Ti lower than 4% in the Ni-Cr-Mo casting alloy had no effect on corrosion resistance. A pitting resistance equivalent (PRE) of about 49 could provide the Ni-Cr-Mo alloy with a good pitting corrosion resistance.

Chromium↗
PubMed1986

The effects of an enhanced inflammatory reaction on the surface properties of cast Biomer.

The ability of a biomaterial to withstand the rigors of the harsh biologic environment is an important consideration when considering a material for long-term biomedical applications. Using a cage implant system, the effects of an intense inflammatory reaction on cast Biomer have been investigated. The inflammatory response to cast Biomer was greatly increased by coimplanting Biomer films with a cytotoxic poly(vinyl chloride) (PVC) in rats for a period of 21 days. Cast Biomer films were characterized by weight, advancing contact angle with water in air, attenuated total reflectance infrared spectroscopy and scanning electron microscopy (SEM). The analyses were performed before any treatment, after autoclaving and sonication, and after 21 days implantation with the cytotoxic (PVC) in rats. The results of the study indicated that cast Biomer does not undergo significant chemical degradation when subjected to the effects of an intense inflammatory reaction for 21 days. Implantation does, however, lead to rearrangement that results in a more polar and hydrophilic surface, suggesting that the polymer adapts to the hydrophilic environment of the inflammatory exudate.

Animals↗
PubMed2004

Osteoblast responses to tape-cast and sintered bioactive glass ceramics.

The advantage of tape-cast bioactive glasses lies in the manufacturing procedure, which allows the build-up of layers and, therefore, the production of complex shapes. This, therefore, has applications to tissue engineering, where specific shapes are required such as repair of craniofacial defects. The bioactivity of tape-cast discs sintered at temperatures ranging from 800 degrees C to 1000 degrees C and for 3 or 6 h was analyzed by FTIR. Tape-cast discs were used to culture primary human osteoblasts, and cell attachment, cell death, collagen production, nodule formation, and mineralization were studied. These responses were dependent upon Si and Na release profiles of the tape-cast discs, and development of the hydroxyapatite layer.

Apoptosis↗
PubMed2005

Tape-casting technique can prepare beta-TCP sheets with uniform thickness and flexibility.

The objective of this study is to propose a new fabrication technology for bone substitutes. In this study, a tape-casting method was used to prepare flexible beta-tricalcium phosphate (beta-TCP) sheets. A beta-TCP slurry containing a binder and plasticizer was used in a doctor blade system. The beta-TCP sheet obtained by this tape-casting method was highly flexible, enabling twisting and free-form shaping. The beta-TCP sheet was approximately 0.21 mm thick. X-ray diffraction and Fourier transform infrared spectrometry revealed that the structure of the beta-TCP component in the sheet is the same as that of the original beta-TCP powder. Observation by field-emission scanning electron microscopy showed that the beta-TCP sheet had a flat, microgranular surface. During the early stages, the tensile stress-strain curves of the beta-TCP sheet showed a nonlinear behavior until reaching the point of final fracture. This result was derived from the ductile property of the prepared beta-TCP sheet. In conclusion, a flexible beta-TCP sheet was easily prepared using a tape-casting technique. Fabrication using tape casting offers the advantages of enabling the preparation of ceramic sheets with precise thickness and not requiring expensive fabrication facilities.

Biocompatible Materials↗
PubMed2006

Joint properties of cast Fe-Pt magnetic alloy laser welded to gold alloys.

This study investigated the joint properties of a cast Fe-Pt magnetic alloy (Fe-36 at % Pt) laser welded to three gold alloys. The gold alloys used were ADA Type II and Type IV gold alloys, and an Ag-based (Ag-Au) gold alloy. Cast plates (0.5 x 3.0 x 10 mm) were prepared for each alloy. After the cast Fe-Pt plates were heat treated, they were butted against each of the three alloys and then laser welded with Nd:YAG laser at 200 V. Homogeneously welded specimens were also prepared for each alloy. Tensile testing was conducted at a crosshead speed of 1 mm/min. Failure load (N) and elongation (%) were recorded. After tensile testing, the fractured surfaces were examined with the use of SEM. The failure-load values of the group of alloys welded homogeneously were ranked in the order of: Ag-Au alloy > Type IV alloy > Type II alloy > Fe-Pt alloy. The Type IV alloy welded to Fe-Pt alloy had the highest failure-load value among the three alloys tested. The elongation results tended to follow a similar pattern. The results of this study indicated that Type IV gold alloy is a suitable alloy for metal frameworks to which cast Fe-Pt magnetic alloy is laser welded.

Alloys↗
PubMed2006

Effects of sandblasting and electrical discharge machining on porcelain adherence to cast and machined commercially pure titanium.

The aim of this study was to determine the effect of sandblasting and electrical discharge machining (EDM) on cast and machined titanium surfaces and titanium-porcelain adhesion. Twenty machined titanium specimens were prepared by manufacturer (groups 1 and 2). Thirty specimens were prepared with autopolymerizing acrylic resin. Twenty of these specimens (groups 3 and 4) were cast with commercially pure titanium and the alpha-case layer was removed. For control group (group 5), 10 specimens were cast by using NiCr alloy. Groups 2 and 4 were subjected to EDM while groups 1, 3, and 5 were subjected to sandblasting. Surface examinations were made by using a scanning electron microscope (SEM). A low-fusing porcelain was fused on the titanium surfaces, whereas NiCr specimens were covered using a conventional porcelain. Titanium-porcelain adhesion was characterized by a 3-point bending test. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests. Metal-porcelain interfaces were characterized by SEM. The bond strength of control group was higher than that of the titanium-porcelain system. There was no significant difference between cast and machined titanium groups (p > 0.05). There was no significant difference between EDM and sandblasting processes (p > 0.05). The use of EDM as surface treatment did not improve titanium-porcelain adhesion compared with sandblasting.

Acrylic Resins↗
PubMed1988

Controlled vascular corrosion casting of the rabbit eye.

We have refined the technique of vascular corrosion casting with methacrylate to permit the reproduction of physiological states of vascular tone and to produce sturdy castings of ocular microvasculature. The method entails careful maintenance of homeostasis up to the moment of plastic perfusion, avoidance of vascular rinsing or fixation with the attendant anoxia, reduction of the viscosity of the casting resin without impairing the properties of the resultant polymer, addition of a cross-linking agent to increase the strength of the plastic, and injection at physiological temperature and pressure. This casting regimen reproduces the normal anatomical conditions of blood vessels and can be used to demonstrate altered conditions of vascular tone. In all instances, the second, untouched eye serves as a control for unilateral manipulations. Special problems of replicating the ocular vasculature are related to the intraocular pressure, which opposes the vascular perfusion pressure and constitutes an impediment to perfusion.

Animals↗
PubMed2006

Comparative analysis of dental enamel polyvinylsiloxane impression and polyurethane casting methods for SEM research.

Dental casting is a very common procedure for making high-quality replicas of paleo-anthropological remains. Replicas are frequently used, instead of original remains, to study both fossil and extant Primate teeth in morphological and metrical analyses. Several commercial products can be used in molds. This study analyzed SEM image resolution and enamel surface feature definition of tooth molds at various magnification levels and obtained, with both Coltène and 3M low-viscosity body polyvinylsiloxane impression, materials and polyurethane casts. Results, through comparison with the original teeth, show that both the negative molds and the positive casts are highly reliable in replicating enamel surfaces. However, positive cast quality is optimal for SEM observation only till the fourth consecutive replica from the original mold, especially at high SEM magnification levels.

Dental Enamel↗
PubMed2003

Winged presoldiers induced by a juvenile hormone analog in Zootermopsis nevadensis: implications for plasticity and evolution of caste differentiation in termites.

To elucidate the switching mechanism of caste differentiation in termites and to examine the possible induction of soldier-reproductive intercastes experimentally, we investigated the effects of juvenile hormone on the morphologies of soldier caste by applying a juvenile hormone analog (JHA) to nymphs of the damp-wood termite Zootermopsis nevadensis (Isoptera : Termopsidae). JHA treatment for about 2 weeks induced a variety of intermediate castes, showing both alate and soldier morphological features. The principal component analysis (PCA) of those morphological characters showed that those intercastes were a deviation from the developmental line into alates to soldier differentiation, which is known to be triggered by juvenile hormone. Detailed morphological examination of the compound eyes, wing joint, and mandibles showed that those intercastes expressed soldier features, although they had started to develop alate characteristics. The morphology of the resultant intercastes seemed to be determined by the nymphal stage, at which JHA treatment was applied. The induced intercastes with exaggerated soldier-specific characteristics (e.g., mandibles) repressed alate-specific characteristics (e.g., wings), namely, the alate and soldier morphological characteristics in induced intercastes show opposite responses against the application of JHA. On the other hand, ovarian development was not suppressed by the JHA application, even in the soldier-like individuals. Naturally differentiated presoldiers also possessed developed ovarioles, although ovaries of mature soldiers were degenerated. Our results suggest that the juvenile hormone plays complicated roles in the expression of caste morphologies and ovarian development in termites.

Animals↗