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Three series of two types of specimens were cast from a cobalt and a nickel base alloy using variation in mould and metal temperatures and in mould size. The casting procedures included a unidirectional solidification system and a problem of feeding. Porosity was assessed by radiographic and metallographic analyses.
A series of standard tensile specimens produced from a nickel-base removable partial denture casting alloy were subjected to heat treatments at three temperatures and three periods at each temperature. The microstructures developed within the castings disclose changes in both the matrix and interdendritic zones.
In order to develop analytical methods for identifying plaster or dental stone (calcium sulphate hemihydrate) and quantifying its content in gypsum-bonded dental casting investments, six dental gypsum products were studied by means of simultaneous differential thermal analysis-thermogravimetry (DTA-TG). Under the same analytical conditions employed in the present study, a phase change in calcium sulphate anhydrite (III-CaSO4 to II-CaSO4) was shown to occur at about 220 degrees C for four dental stones manufactured by various wet methods and at about 350 degrees C for two plasters manufactured by dry methods. This confirms the general view that the two types of calcium sulphate hemihydrate manufactured by dry or wet method could be identified by the DTA method. A reasonable estimate of chemically bound water could be made from the TG results at 300 degrees C. The present DTA-TG method can be used to identify the plaster or dental stone and calculate its content in gypsum-bonded casting investments.
A severe case of the cast syndrome is described following Harrington rod distraction and application of a body cast. The case was unusual as it presented late with no warning symptoms and progressed rapidly to death.
The hypothesis of the present study was that rats subjected to short-term unilateral hindlimb immobilization would incur skeletal muscle wasting and concomitant alterations in protein synthesis, controllers of translation, and indexes of protein degradation. Rats were unilaterally casted for 1, 3, or 5 days to avoid complications associated with other disuse models. In the casted limb, gastrocnemius wet weight decreased 12% after 3 days and thereafter remained constant. In contrast, the contralateral control leg displayed a steady growth rate over time. The rate of protein synthesis and translational efficiency were unchanged in the immobilized muscle at day 5. The total amount and phosphorylation state of regulators of translational initiation and elongation were unaltered. The mRNA contents of polyubiquitin and the ubiquitin ligases muscle atrophy F-box (MAFbx)/Atrogin-1 and muscle RING finger 1 (MuRF1) were elevated in immobilized muscle at all time points, with peak expression occurring at day 3. Daily injection of the type II glucocorticoid receptor antagonist RU-486 did not prevent decreases in gastrocnemius wet weight nor increases in mRNA for MAFbx/Atrogin-1 and MuRF1. However, in vivo administration of the proteasome inhibitor Velcade prevented 53% of wet weight loss associated with 3 days of immobilization. These data suggest that the loss of skeletal muscle mass in this model of disuse appears to be glucocorticoid independent, can be partially rescued with a potent proteasome inhibitor, and is associated with enhanced mRNA expression of multiple factors that contribute to ubiquitin- proteasome-dependent degradation and are likely to control the remodeling of immobilized skeletal muscle during atrophy.
Atrophy and growth failure of muscle in a tail-cast suspension model were evaluated in hindlimbs of female Sprague-Dawley rats. Based on measurements of food consumption, animal growth rate, urinary excretion of urea and ammonia, and muscle size, 6 days seemed to be the optimum duration of suspension for studying muscle unloading. After 6 days, the soleus, plantaris, and gastrocnemius muscles from suspended animals were 27, 10, and 11% smaller (P less than 0.05), respectively, than those from tail-casted weight-bearing animals. The extensor digitorum longus and tibialis anterior muscles were unaffected by suspension (less than or equal to 6 days) while the triceps brachii hypertrophied (8%, P less than 0.05). Wet weight-to-dry weight ratios were smaller in the plantaris (-0.19, P less than 0.05) and gastrocnemius (-0.19, P less than 0.05) muscles from suspended rats. In the plantaris, this difference coincided with a higher protein concentration (+12 mg/g, P less than 0.001). In vitro measurements of protein metabolism in the soleus muscles of suspended rats showed both slower protein synthesis (P less than 0.05) and faster protein degradation (P less than 0.05), whereas these processes were unaltered in the extensor digitorum longus muscles.
The purpose of the present study is to determine the changes of vascular architecture in the degenerated retina. We used mainly corrosion casts of the retinal vasculature and scanning electron microscopy to obtain a wide three-dimensional view. WBN/Kob rats (a spontaneously diabetic strain) were used because their outer retinas degenerate and become very thin with age. In 15-month-old rats, localized constriction and irregular caliber of the capillaries were evident in the vascular casts. Two layers of capillary network in the retina were maintained, but the capillaries were decreased in number. Numerous loop formations were present in the superficial capillary networks. Neither microaneurysms nor arteriovenous shunts were seen in young and old rats. Transmission electron microscopy revealed that capillary pericytes in the inner and outer plexiform layers had thickened basement membranes and that endothelial cells had many vesicles in their cytoplasm. Thus the retinal capillary changes in WBN/Kob rats are nondiabetic but due to hereditary retinal degeneration, although the systemic and pancreatic abnormalities in this rat strain are diabetic. Even when the retina becomes very thin, two layer capillary networks remain.
Specific researches, employing corrosion casts, were performed on different skeletal muscles, but not on extra-ocular muscles (EOMs). The microvascular bed of EOMs was studied by the corrosion cast technique in the rat. Two histologically and physiologically different layers were present in the EOMs. On the whole, the capillary pattern of EOMs was less dense than in the other skeletal muscles. The EOM orbital layer turned out to have a higher number of transverse anastomoses and tuning-fork divisions than the global layer had. These different microcirculatory patterns can be related with the physiological function and the anatomical situation of the EOMs.
Plastic corrosion casts of the rat retinal vasculature were studied by scanning electron microscopy. This technique demonstrated the entire retinal vasculature of the rat. The retinal blood vessels supplying the rat's retina have a definite and fairly constant pattern. At the disk there are usually six main artery and vein branches that run symmetrically towards the periphery. Veins are wider and more tortuous. The characteristic arrangement of endothelial cell nuclear indentations clearly differentiates arteries from veins. Retinal arteries have side-arm and dichotomous branchings. The number of vessel branches is greater on the nasal side than on the temporal side of the retina. The vein-over-artery crossing phenomenon is more frequent than the artery-over-vein. Retinal capillaries appear tortuous and are arranged cylindrically in two layers. The superficial network of capillaries comes essentially from arterioles, while deep layer capillary networks are more regularly and densely arranged and are mainly connected with venules. The inner and the outer capillary networks have interconnections, vertical runs and short vascular bridges. Within the retina there are regional variations in capillary pattern and distribution. More regular, dense and rich capillary networks are observed in the peripheral area than at the posterior pole area. No arteriovenous shunts were seen. The study of such plastic casts makes possible a more accurate assessment of some aspects of vascular abnormalities. These findings will be helpful in further investigations of retinal vascular abnormalities.
Standard tensile specimens were cast from a nickel-base partial denture casting alloy and subsequently fractured in a tensile stress testing machine. Fracture sites were subjected to scanning electron microscopy in order to determine the exact mechanism by which failure had occurred. A metallographic examination of prepared specimens was used to demonstrate the distribution of phases within the alloy.
The cytotoxic potentials of three Ni-Cr based alloys and an Fe-Cr based alloy were assessed. In tissue culture, casting of all four test materials and powders of the Fe-Cr based material did not elicit adverse cellular changes. However, cultures containing Ni-Cr powders showed prominent zones of lysis and cell alteration. The cytotoxic potential of products obtained from the surfaces of casting alloys may offer an expedient means for estimation of long-term clinical toxicity.
The structure of a commercial dental Ag-Pd-Cu-Au casting alloy has been studied by microprobe and X-ray diffraction analyses after various heat treatments. The composition of phases in equilibrium was established. After being annealed at 400 degrees C, 500 degrees C, and 600 degrees C for seven wk, the alloy consisted of three phases: a Cu- and Pd-rich fee phase (alpha 1) with alpha = 0.372nm, a Ag-rich matrix (alpha 2) with alpha = 0.399nm, and an ordered CsCl-type bcc PdCu phase with alpha = 0.296nm. The PdCu phase was not observed above 600 degrees C, and the proportion of the alpha 1 phase decreased sharply above 700 degrees C. After being annealed at 900 degrees C, the alloy matrix was partly decomposed at the Cu-enriched grain boundaries. The decomposed areas grew into the grain interior during subsequent precipitation hardening. No segregation of Au was detected after casting, and the element was evenly distributed throughout the alloy structure after all heat treatments.
Eighty-eight athletes treated for an acute hemarthrosis of the knee without any demonstrable ligament tear were evaluated. Analysis of the clinical data from these cases, all treated between 1970 and 1975 with aspiration and casting, revealed that the injury was apparently worse than had been thought at the time of first treatment. Surgery was subsequently performed in 32 (37%) because of meniscus tear, and 28 demonstrated anterior cruciate ligament insufficiency. In the 56 who did not have surgical treatment, 38 (43% of the entire group) had significant symptoms and disability causing them to decrease sports participation, and only 18 (20% of the overall group) returned to sports without symptoms or disability. Objective findings at followup suggested that in 70% of the patients injury of the anterior cruciate ligament occurred during the original trauma. A precise diagnosis is needed in every knee ligament sprain with hemarthrosis before one decides upon conservative treatment such as aspiration and casting.
A prospective study was performed on 40 patients who were treated with a modified thumb spica cast (MTSC) for injuries involving the region of the metacarpophalangeal joint of the thumb. Twenty-seven of these injuries occurred during sports participation. The immobilization consisted of a fiberglass cast which incorporated the thumb in a balanced position and allowed full flexion and extension of the wrist. Twenty patients had injuries involving the ulnar collateral ligament (five surgical). Three patients had radial collateral ligament injuries (two surgical). Fourteen patients had fractures of the proximal phalanx, including five epiphyseal plate injuries. Two patients had dorsal dislocations and one patient had a metacarpal fracture. One patient with a nondisplaced distal metacarpal fracture was treated with simple immobilization. All patients had successful completion of their treatment within the usual time frame. There was no recurrence or increase in symptomatology during the treatment. There was no residual discomfort, loss of position or malunion of the fractures treated. The advantages of the MTSC include improved functional capabilities during immobilization, good patient acceptance, and no period of limited wrist motion or atrophy of forearm musculature. Our experience has been that the MTSC has been a reliable form of immobilization for treating injuries of the metacarpophalangeal joint of the thumb.
A 1.5-cm longitudinal, full-thickness incision was made in the vascularized portion of the medial meniscus in 20 adult dogs and anatomically repaired. Postoperatively, the animals were either placed in a long leg cast (N = 9) or mobilized immediately (N = 11). The animals were sacrificed at 2 weeks (6 dogs), 4 weeks (6 dogs), or 10 weeks (8 dogs). Five medial menisci from the nonoperated side were used as controls. Collagen content was measured using a digital image analysis system, and the collagen percentage in the repair tissue in each postoperative treatment group was compared. In the 2-week and 4-week groups, there was no statistically significant difference in the percentage of collagen between those animals immobilized versus those that had early mobilization. The animals in the 10-week group that were mobilized had a significantly greater collagen percentage in the healing meniscal incision than those that were cast immobilized (44.6% +/- 10% versus 27.0% +/- 11%, P < 0.0001). There was no significant difference in the collagen percentages between the mobilized 10-week group and the contralateral control menisci group. All other menisci had a decreased collagen percentage compared with the controls. Prolonged immobilization decreases collagen formation in healing menisci. Thus, our results suggest that patients undergoing isolated meniscal repair either be immediately mobilized after surgery or immobilized for short periods only.
Side-effects from dental materials are a minor problem, but should be recognized. In recent questionnaire surveys about side-effects, the incidence was estimated to be 1:300 in periodontics and 1:2600 in pedodontics. None of these reactions was related to dental casting alloys. In prosthodontics, the incidence was calculated to be about 1:400, and about 27% were related to base-metal alloys for removable partial dentures (cobalt, chromium, nickel) and to noble/gold-based alloys for porcelain-fused-to-metal restorations. The complaints consisted of intra-oral reactions (such as redness, swelling, and pain of the oral mucosa and lips), oral/gingival lichenoid reactions, and a few instances of systemic reactions. In orthodontics, the incidence was 1:100, and most reactions (85%) were related to metal parts of the extra-oral anchorage devices. Even though the extensive use of base-metal alloys has been of major concern to the dental profession, relatively few case reports substantiate this concern. Allergy to gold-based dental restorations has been more commonly reported. Palladium-based alloys have been associated with several cases of stomatitis and oral lichenoid reactions. Palladium allergy seems to occur mainly in patients who are very sensitive to nickel. All casting alloys, except titanium, seem to have a potential for eliciting adverse reactions in individual hypersensitive patients. Tolerance induction may be a possible benefit of the use of intra-orally placed alloys. In non-sensitized individuals, oral antigenic contacts to nickel and chromium may induce tolerance rather than sensitization. A variety of systemic diseases and reactions has been claimed to be caused by dental materials. The claims are generally poorly documented.
INTRODUCTION: Total Contact Casting (TCC) is considered the gold standard in the treatment of neuropathic diabetic foot ulcers. To overcome some disadvantages of TCC we developed a removable fiberglass combicast shoe--the MABAL shoe. PATIENTS AND METHODS: The MABAL shoe was used to treat 23 plantar ulcers. RESULTS: Before treatment the mean surface area was 2.0 cm2 (0.5-7.1 cm2). Twenty-one of 23 ulcers healed, with a mean healing time of 34 days (7-75 days). CONCLUSION: The MABAL shoe provides healing of neuropathic diabetic foot ulcers comparable to existing methods of treatment, while offering some potential advantages. The main advantages are mobilization of the ankle, removability of the cast and a less time consuming form of treatment.
We evaluated the ability of seven devices to immobilize a prosthetic ankle-foot complex against plantarflexion, dorsiflexion, inversion, and eversion forces: two casts (plaster of Paris and Fiberglas) and five removable braces (molded ankle/foot orthosis, composite boot brace, pneumatic boot walker, nonarticulating fracture boot, and ankle stirrup). Each device was applied to a prosthetic ankle-foot complex and evaluated on a test frame for resistance to sagittal motion and coronal torque. Results showed that casts offered significantly (P < or = 0.05) more resistance to motion in all directions tested than did the braces. The resistance offered by the devices tested depends on the conformity of the device to the shape of the foot in that plane and the material properties of the device. Braces offer the advantage of being easily removed and reapplied. Different braces offer specific advantages and disadvantages in different planes tested, and immobilization selection should be individualized based on this information.