Gypsum is one of the most common natural minerals, which is widely used in medical practice. To obtain the material, the crystals of the mined gypsum stone are ground in special mills and fired in kilns.
The composition of medical gypsum is a semi-aqueous calcium sulfate s alt (CaSO4 H2O). Available as a white powder.
Depending on the purpose of gypsum, grinding technology and firing temperature will be different.
Classification
According to the requirements of the international hardness standard, the following types are distinguished:
- soft plaster, used for making impressions in orthopedic dentistry;
- ordinary (medical) gypsum, used in general surgery and orthopedics;
- hard gypsum, designed for making models of jaws in dentistry;
- extra strong gypsum, used to create collapsible jaw models;
- heavy-duty plaster, designed for models in the dentalorthotics requiring ultra-high strength are made with the addition of synthetic components.
When mixed with water after 5-7 minutes, the gypsum begins to harden, gaining strength. The material acquires its final characteristics and hardness after complete drying.
Properties
Medical gypsum has won its recognition due to its low price, availability, ease of handling and such important properties for medical use as:
- non-toxic, harmless;
- no smell;
- the ability to keep in shape for a long time;
- resistance when interacting with water;
- low shrinkage ratio.
The powder has a high water absorption, when combined with water, it reacts with the formation of gypsum dihydrate and the transition of the mass to a solid state. The hardening rate is influenced by the conditions of gypsum firing, water temperature, gypsum-water mass ratio, and the presence of impurities. Water heated to 37 °C speeds up the hydration reaction (particle binding), anything above or below this temperature slows it down.
Water consumption per kilogram of powder is 0.6–0.7 liters. Hardening time - 10-15 minutes. You can evaluate the suitability of gypsum by taking it in your hands and squeezing it between your palms. If it crumbles when unclenched, then the material is dry and suitable for use. If a lump forms, then the plaster is wet and cannot be worked with.
Application
Ordinary calcined plaster is used to make plaster casts(bandages) at:
- pain relief of fractures;
- applying adhesive stretching;
- fixing damaged areas;
- manual reposition of bone fragments;
- reposition using pull sections.
Soft plaster is used in the manufacture of both dental impressions (full and partial) and impressions from edentulous jaws.
Removable dentures of the entire dentition or removable dentures of partial replacement can be made from high-strength medical plaster.
Terms of Use
For a favorable work with the material in dental practice, you should adhere to the following rules.
- Dental plaster must be stored in a dry place. Reservoirs must be cleaned of residue after each emptying.
- The tools used in the work must be washed and cleaned of traces of plaster after previous use.
- The amount of plaster to be kneaded at a time should be calculated for no more than three impressions.
- Keeping the proportions of gypsum and water when mixing is extremely important.
Gypsum Impression Technology:
- powder is slowly poured into a container with water at a temperature of 20 ° C;
- waiting for the gypsum to settle to the bottom;
- start mixing - machine lasting no more than 30 seconds, manual - no more than a minute;
- the resulting mixture is poured into a mold.
For comfortable and quick work of doctors in surgery, it is recommended to adhere to the following principles when making plaster casts.
- To determine the amount of plaster required, first measure the length of the bandage along a he althy limb.
- It is more convenient to apply plaster bandages when the patient is in a supine position. For convenience, the diseased limb is raised above this level of position.
- Medical plaster dressings should be laid evenly, with a certain step, avoiding kinks, creases and folds.
- Areas subject to heavy loads need to be strengthened and strengthened with an additional layer.
- Toes and hands should be left open so that it is possible to track the possible squeezing of the limb and remove the bandage in time.
- After applying plaster bandages with stroking movements, they are brought closer to the actual contour of the surface of the limb, repeating all the bends and depressions.
- After drying, data on the date of application, date of fracture, a schematic representation of the fracture and the estimated date of removal are applied to the bandage.
Removing casts
Petrified plaster bandages are removed with plaster tongs or scissors, a saw and a metal spatula. In the case when it is possible to cut the plaster, then use special scissors. If the space under the bandage does not allow, then a spatula is inserted under the bandages to protect the skin from injury. After that, cutting or sawing is carried out.
Cutthe bandage follows from that party where there are soft fabrics. For example, plaster bandages up to the middle third of the thigh are cut along the back surface, corsets - from the back, and so on. The cut edges are pulled apart and the limb is removed. Discard the removed parts of the dressing. Since the price of gypsum is low, its one-time use is very economical and low-cost.
The presence of a doctor during the manipulation is mandatory: he controls the condition of the limb and decides on the need to apply a new plaster cast.
Where to buy
Medical gypsum is produced by companies that manufacture products for construction and finishing works. Its main difference from gypsum for construction purposes lies in the degree of grinding, and as a result, in faster hardening times. You can buy gypsum for medical practice directly from the manufacturer. One of the leading manufacturing companies are Samaragips and Volma.
Medical gypsum "Volma" is produced according to TU 5744-013-78667917-13, the product from "Samaragyps" - according to TU 5744-013-21151476-2014 in paper bags weighing 20 or 25 kg. The cost of a kilogram varies depending on the type of gypsum and its purpose. On average, it is 15–25 rubles.
