Seven brands are Calspar (Dental Products of India, Mumbai, India) Rajhans (Aruna Plaster Udyog, Haridwar, India), Elephant (Gypstona Industries, Haridwar, India), Horse Universal Plaster Industries, Howrah, India), Johnson (Johnsons & Johnsons, Mumbai, India), Lion (Snowwhite Industries, Rishikesh, India) and SNC (Shree Niwas Chemicals, Ambala, India). In the present investigation an attempt has therefore, been made to test the physical properties of seven dental laboratory gypsum manufactured in India. Beta-hemihydrates are more popularly known as plaster of paris. By different calcinations method beta-hemihydrates and alpha-hemihydrates can be found. This hemihydrate form of gypsum is fine powder rather than hard rock. After calcinations it is converted into calcium sulphate hemihydrate. Gypsum chemically known as calcium sulphate dihydrate. Deposits of gypsum, however, are found in many countries. The term plaster of paris was given to this product because it was abstained by burning the gypsum mineral from the deposits near Paris, France. After suitable manufacturing processes, gypsum may be made into various types of products, such as plaster of paris, dental stone and investment materials. It is believed that early sculptors may have made plaster casts of different objects. Since biblical times gypsum materials have also been used as building materials. Its different varieties have been use for centuries for making decorative arts and objects. Colour may be gray, red or brown due to presence of some foreign materials like as clay, iron oxide or oxides of other materials. It is usually white to yellowish milky in color and is found in a compact mass in nature. Gypsum is a type of stone that is mined from earth.

The present study shall be able to provide some beneficial information regarding their quality control and guide the manufacturers for improving the standardization of their products so that most suitable type of material may be available to the profession. It was found that none of the brands were up to mark. Statistical analysis for comparative study was done. The obtained data were tabulated and compared with Indian, Australian and US standard specification. Seven brands namely Calspar, Rajhans, Elephant, Horse, Lion, Johnson and Shree Niwas Chemicals were selected for the comparison of their particle size, consistency and setting time.

The aim of this study was to access, compare and evaluate the physical properties of different brands of laboratory gypsum available in Indian dental market. The wide use of plaster of paris motivated a number of manufacturers to introduce different brands of the profession but their physical and mechanical properties were still questionable. Gypsum products are one of the most widely used materials in dentistry.

Standard sizes of plaster rings