Dental materials is an important subject for dental students. It mainly deals with the materials used in both practical and laboratory dentistry.It gives an insight about the physical chemical and the mechanical properties of the materials that are used in dentistry.The dental materials may broadly classified on the basis of their use. They are:
orthodontic bands and wires
cements,bases ,varnishes and liners
the components of each genre range from polymers to metals.there are many materials under each type of material and the adequate material can be chosen according to the requisites.
Impression materials 
An impression is a negative recording of the oral cavity and associated structure in appropriate and accurate dimensions. The material that help in taking an impression is called impression material. The most common impression material is Alginate. Alginate is an irreversible hydrocolloid material. Meaning that it cannot return to the sol state after they turn into a gel. The biggest ingredient in alginate is potassium alginate which is found in seaweed. It is also used for a thickening agent in some ice creams.