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Different types of wax interocclusal records were tested to determine if the type of recording material affects cast position when dental plaster is used to mount casts. The results indicate that a difference in the type of wax record is not a significant factor in cast fixation.
Electronic sensors were used to measure skin surface pressures beneath plaster and fiberglass short leg casts. Pressures were recorded after casting, univalving, bivalving, and spreading of casts. Fiberglass resulted in significantly higher pressures than plaster. Beneficial effects of bivalving and cast spreading are confirmed by significant pressure drops. Application of casts by different orthopaedic surgeons and technologists showed pressure differences due to operator technique. However, fiberglass pressures again proved to be significantly greater than those caused by plaster. Excessive pressure beneath casts can cause skin ulceration, and results confirm the need for extreme care, especially when using fiberglass. It is suggested that plaster is safer than fiberglass when significant extremity swelling is likely or when a patient's skin is more vulnerable to breakdown.
In this study, two types of orthopaedic casting materials were evaluated: the Johnson & Johnson Specialist plaster bandage and the 3M Scotch-cast Plus fiber glass bandage. The materials were evaluated using tensile tests to determine the elastic modulus, yield strength, and ultimate tensile strength. To determine the structural characteristics and stiffness of a cylindrical cast, each material was formed around a foam cylinder core and tested in a four-point bend jig. A computer-based model using the finite element method (FEM) was developed for a cylindrical cast of both types and compared with the experimental findings. A second FEM model with loads applied at the periphery was performed to simulate the clinical observations of plaster bandage breakdown at the ends of a cast. It is with these tests that the two bandage materials were compared and evaluated. It was concluded that the plaster bandage, while initially stiffer than the fiber glass bandage, had much lower yield stress. This implies that the plaster cast may break down under loads that would leave the fiber glass cast intact. It was also determined that the plaster bandage load displacement curve is bilinear. The bilinear characteristic of the plaster bandage explains its breakdown at the ends of a cast.
Pneumatic tourniquets and plaster of Paris splints and casts are the hallmarks of hand surgery, firmly entrenched as an adjunct in the routine treatment of upper extremity disorders. Because they are usually employed with a comparative degree of safety and because they are relatively simple devices from a technologic perspective. Little is written about them in the scientific literature. In this paper we extensively review their historical developments, physiologic effects, and common complications, and we attempt to provide a rationale for their safe and effective use.
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PURPOSE: To explore the role of Joshi's external stabilisation system fixator in correcting cases of clubfoot peculiar to India, we studied cases of neglected clubfoot, dropout cases of plaster-of-paris cast treatment, or failed surgical procedures that had been followed for a minimum period of 2 years. METHODS: 26 children underwent 44 Joshi's external stabilisation system procedures at the Central Institute of Orthopaedics at the Safdarjung Hospital, New Delhi, between January 1998 and December 1999 for the conditions of interest. Three-dimensional correction was achieved by use of the distractor device. RESULTS: Excellent results were obtained in 77% of the cases, good results in 13%, and poor results in 9% of the cases. Complications in half of the cases were pintract infections, which eventually healed on an outpatient basis without any residual sequelae. CONCLUSION: The Joshi's external stabilisation system frame is ideally suited for the child in whom clubfoot deformities remain uncorrected by plaster-of-paris casts and manipulation, as well as for recurrent clubfoot. Casting after complete correction not only protects the osteopenic bones while the pin-tracts heal, but also maintains correction and allows gradual weightbearing.
A 50-year-old male presented with a T4 N0 squamous cell carcinoma of the floor of the mouth and alveolus. Treatment included a partial mandibulectomy with a free osseocutaneous fibula flap reconstruction. He made a good postoperative recovery and was given adjuvant radiotherapy. No problems were reported with the donor site or ankle. Five months after harvesting the flap the patient sustained a fracture of the medial malleolus having jumped over a ditch playing golf. This was treated successfully with a below knee plaster of Paris cast. The interosseous membrane was not ruptured in the accident indicating that the distal fibula left in situ was adequate to maintain the integrity of the mortice. A degree of ankle instability may be present after fibula flap harvest which is only revealed by athletic activity. (c) 2000 Harcourt Publishers Ltd Copyright 2000 The British Association of Plastic Surgeons DOI: 10.1054/bjps.1999.3227.
Children with spina bifida cystica have a high risk of fracturing their paraplegic legs. During the last fifteen years we observed 261 fractures and epiphyseal injuries in 173 children out of 1,400 (12.2%) patients with spina bifida. The increased risk of fracture seems to be due to reduced muscle activity in the paralysed limb with insufficient axial loading of the legs. A large proportion of fractures occurs after orthopedic interventions. Fractures are less common after urologic or neurosurgical procedures. Breaks are extremely frequent after operations in association with cast immobilization. Early standing and short immobilization times are the best defence mechanisms against fractures. If plasters are needed postoperatively one should preferably use the "Max and Moritz" standing cast. Fractures in spina bifida children heal quickly as compared to those in non-paralyzed children. In 30% excessive callus is seen. Immobilization for fracture care can be done in a standing cast even in the very early phase of treatment. In spite of the swelling and elevated temperature axial loading in the standing cast should continue. Splints and braces can be used instead of the plaster cast. By any means, the vicious circle of Fracture-Plaster-Fracture-Plaster should be avoided. Repeated stress on the growth plate causes a mechanism of loosening. The most common site is the distal tibia and femur, less often loosenings occur in the proximal tibia and proximal femur. Epiphyseal loosening is a nosological entity seen in spina bifida and also in congenital absence of sensation. Distal tibial epiphyseal loosening is frequently seen in adolescents who have learned to walk only after muscle balancing procedures in the hips.(ABSTRACT TRUNCATED AT 250 WORDS)
PURPOSE: This study evaluated the positional accuracy of casts articulated on a semi-adjustable articulator, with and without rigid cast stabilization using either laboratory plaster or mounting plaster. MATERIALS AND METHODS: A reference articulation of melamine casts in maximum articulation was established and recorded in the horizontal and vertical dimensions using a verification device. The same casts were subsequently remounted 24 times using either laboratory plaster or mounting plaster. Half of the articulations from each group were stabilized using detachable mounting rods and sticky wax, and half were hand-articulated without stabilization, for a total of 6 articulations in each of 4 test groups. The resulting spatial positions established on the articulator were compared to the initial reference position on the verification device grid. Means and standard deviations of the absolute values of the horizontal and vertical displacement for each group were determined separately and compared using a one-way anaylsis of variance. Significant differences (p <0.05) were identified using Tukey's honestly significant difference multiple comparison test. RESULTS: Mean vertical mandibular cast displacement ranged from 0.26 +/-0.21mm for stabilized casts mounted with laboratory plaster to 1.58 +/-0.32 mm for unstabilized casts mounted with mounting plaster. For each mounting material, significantly less vertical displacement (p <0.001) was observed with the mandibular cast stabilized before mounting. The cast mounted with laboratory plaster exhibited horizontal displacement (0.87 +/-0.29 mm) that was significantly greater than the remaining groups (p <0.001), which did not differ from each other. CONCLUSIONS: Rigid stabilization of the mandibular to maxillary cast during mounting with laboratory and mounting plaster improved articulation accuracy.
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BACKGROUND: The development of digitized techniques for manufacturing implant frameworks has made possible alternative "impression" techniques for recording implant positions. PURPOSE: The objective of the present study was to test the precision and accuracy of a three-dimensional photogrammetric technique to record implant positions in vitro and to compare casts made with this technique with conventional casts fabricated with two conventional impression techniques. MATERIALS AND METHODS: Twenty casts were fabricated from 10 polyether (Impregum, ESPE Dental AG, Seefeld, Germany) impressions and 10 plaster (Kühns Abdrucksgips, Ernst Hirnischs GmbH, Goslar, Germany) impressions of one master model. The casts were measured in a coordinate measuring machine (Zeiss Prismo VAST, Oberkochen, Germany) and compared with the master model. Six separate three-dimensional photographs of the master model were taken with a special camera. After the photographs were measured with an analytic plotter, results were analyzed and compared to the coordinates of the original model and casts. RESULTS: A systematic pattern of distortion in the x-axis was found for the two impression techniques. Expansion of the implant arch at the terminal implants (p < .01) averaged 22 microm and 94 microm on photographs and plaster casts, respectively. Polyether casts contracted an average of 52 microm when compared with the master (p < .01). In absolute figures, photogrammetry and the polyether technique reproduced the x-axis and three-dimensional parameters more accurately than the plaster technique did when cylinder center point distortion was compared (p < .05 to p < .001). However, angular cylinder distortion in absolute figures was greater with the photographic technique than with either of the impression techniques (p < .05-p < .001). CONCLUSION: Photogrammetry is a valid option for recording implant positions and has a precision comparable to that of conventional impression techniques. At present, however, it is limited to framework fabrication techniques that are based on digital platforms.
Four female pupils at a technical school received hand burns while trying to make moulds of their hands using a dental plaster instead of ordinary plaster-of-Paris. In three cases the burns were so severe that several fingers had to be amputated due to irreversible tissue damage. The severity of the burns is explained on the basis of an experimental study where it was demonstrated that the temperature of hardening dental plaster rose to 70 degrees C and had a hardness that was 10-times greater than ordinary plaster-of-Paris. This should serve as a warning against the use of dental plaster in direct casting of living tissue. However, the technique used here is also considered dangerous, as ordinary plaster-of-Paris under certain circumstances could also cause severe burns.
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Previous reports of failures following surgery of distal femoral fractures prompted the development of a semielastic internal fixation device suitable for the mechanically weak bone of the elderly. The fixation device consists of intramedullary elastic Ender-type nails connected to cancellous screws at each condyle by a special coupling piece. Thus, the intercondylar fracture is rigidly stabilized by screws and adjusted to the supracondylar fracture by connected elastic nails. The device is easily applied through small incisions. During a two-year period 54 fractures of the distal third of the femur were treated. Most patients were elderly and suffered from concurrent diseases or previous ipsilateral fractures. The goal was twofold: to avoid traction in bed and to start early mobilization. Fifteen undisplaced fractures were treated by plaster or cast-brace. Five fractures were treated by traction. Thirty-four displaced supracondylar and bicondylar fractures were operated on using the new fixation device. No deep infections or osteomyelitis occurred. Immediate mobilization was possible in all 34 cases, most with an external support of plaster for two weeks and a hinged cast-brace for eight weeks. Twenty-nine patients were followed up to union; results in these displaced supracondylar and bicondylar femoral fractures were excellent in 12, good in nine, fair in five, and poor in three patients. The semielastic character of the system seemed to prevent the failures observed with the use of rigid internal fixation in osteoporotic bone.