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At least 1,747 records · Page 97Linked to original sources
PubMed1993

Study of gypsum-bonded casting investments. Part 1.

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.

Calcium Sulfate↗
PubMed1988

Dust emission during cutting of polyurethane-impregnated bandages.

The airborne dust generated when cutting splinting bandages represents a potential respiratory hazard, particularly to those who regularly remove casts with a power saw. Plaster of Paris (POP) dust is already classified by the Health and Safety Executive as a nuisance dust. This paper reports on a study to determine the nature, size and concentration of dust produced when cutting polyurethane (PU) impregnated bandages using a power saw. It has been shown that, under severe conditions PU bandages produce lower airborne dust concentrations than POP bandage but that all of the bandages tested produced particles small enough to reach the final divisions of the lung. It is therefore recommended that a dust extraction unit be used when cutting all types of bandage.

Air Pollutants, Occupational↗
PubMed1993

Ipsilateral tibia and ankle fractures.

This study reports on 18 cases of diaphyseal fractures of the tibia associated with ipsilateral but not contiguous ankle fractures. Thirteen of these complex fractures resulted from low-energy torsional forces, while five were caused by high-energy impact. Definitive treatment consisted solely of cast immobilization in four; 14 had operative stabilization of each fracture component. Of these 14, four patients were treated initially in long leg casts and one in a plaster splint, but each required surgical intervention to control fracture alignment. The average follow-up time was 21.2 months. In the nonoperative group of four patients, clinically significant shortening and/or rotational deformity were noted in three limbs, with ankle mobility decreased by > 50% and advanced posttraumatic arthritis evident in two ankles. Of the cases managed operatively, 10 (71%) had full structural and functional recovery, three patients regained only 75% of ankle mobility, and two patients developed slight valgus deformities, one with a concomitant rotational deformity of less than 10 degrees. These findings demonstrate the unstable nature of this complex fracture pattern and the advantages of operative management.

Adult↗
PubMed1978

A new approach to the management of wounds of the extremities. Controlled environment treatment and its derivatives.

Controlled Environment Treatment is a new approach to wound management--for the first time it provides the surgeon with the means of controlling and optimizing the wound environment for the duration of the healing period. Equipment is commercially available and the technique is now being applied internationally; the technique has been established for the treatment of limbs--application to the trunk requires further investigation and development. Spin-offs have already occurred, one being the control of certain types of lymphoedema by the patient in their own home; the other concerns the application of plaster of Paris to produce casts having significantly superior physiological characteristics using minimal manipulative skills. The former is known as Pressure Environment Treatment, the latter is known as Controlled Pressure Casting; equipment is commercially available internationally.

Bandages↗
PubMed2000

Excision of a remarkable tumour of the upper jaw in 1834 by Robert Liston.

A series of pre-operative casts of the head, one of plaster of Paris and the other of wax, have recently been discovered in the Department of Anatomy, Edinburgh, of a patient with an immense tumour of the left maxillary antrum which produced an enormous degree of facial distortion. These casts complement a series of engravings published in the contemporary literature. This lady's tumour was successfully excised by Robert Liston in 1834 in the Royal Infirmary of Edinburgh, only a month before he left Edinburgh for London. The tumour was believed to be benign, and was removed without the benefit of anaesthesia. The patient returned the following summer to have a gold palate fitted, and while her voice was initially indistinct, it subsequently recovered.

History, 19th Century↗
PubMed1983

Treatment of broken legs before and after the introduction of gypsum.

Gypsum or plaster-of-Paris has given long and efficient service in the management of fractures of the leg, and in spite of the recent introduction of a variety of synthetic materials (Hunt, 1980) it remains the most commonly used splintage material. Plaster-of-Paris bandages can compete successfully with synthetic ones because of their convenience and easy use notwithstanding the superior strength, shorter curing time, water resistance, and radiotranslucence of the synthetics. However, Orthoplast in sheet form is a very satisfactory material for forming the tibial cast brace while synthetic bandages with plastic flexible hinges are advantageous for femoral cast bracing. Nowadays, in fact, plaster-of-Paris has been supplanted to some extent. A review of the methods of fracture splintage that were used before the introduction of gypsum helps to provide a perspective of the merits of this material, whose properties and availability have been taken for granted for more than a hundred years.

Braces↗
PubMed1985

A comparison of some casting materials.

The physical and mechanical properties of four casting materials are compared with two plaster of Paris preparations. Properties evaluated include working and specific strengths, resistance to abrasion and radiolucency. Ease of application, conformability and rate of strength development are discussed and the clinical relevance of these properties is considered.

Acrylic Resins↗
PubMed2006

Validity, reliability, and reproducibility of plaster vs digital study models: comparison of peer assessment rating and Bolton analysis and their constituent measurements.

INTRODUCTION: The objective of this validation study was to compare standard plaster models (the current gold standard for cast measurements) with their digital counterparts made with emodel software (version 6.0, GeoDigm, Chanhassen, Minn) for the analysis of tooth sizes and occlusal relationships--specifically the Bolton analysis and the peer assessment rating (PAR) index and their components. METHODS: Dental casts were poured from 24 subjects with 8 malocclusion types grouped according to American Board of Orthodontics categories. Measurements were made with a digital caliper to the nearest 0.01 mm from plaster models and with the software from the digital models. A paired samples t test was used to compare reliability and validity of measurements between plaster and digital methods. RESULTS: Reproducibility of digital models via the concordance correlation coefficient was excellent in most cases and good in some. Although statistically significant differences in some measurements were found for the reliability and validity of the digital models via the average mean of the absolute differences of repeated measurements, none was clinically significant. Grouping of the measurements according to the 8 American Board of Orthodontics categories produced no significant difference (Kruskal-Wallis test). No measurement associated with Bolton analysis or PAR index made on plaster vs digital models showed a clinically significant difference. The PAR analysis and its constituent measurements were not significantly different clinically between plaster and emodel media. CONCLUSIONS: Preliminary results did not indicate that digital models would cause an orthodontist to make a different diagnosis of malocclusion compared with plaster models; digital models are not a compromised choice for treatment planning or diagnosis.

Computer Simulation↗