Dental Alginate Impressions

Making of impressions for partial dentures is more difficult compared to those for complete dentures. Most of the failures occur as a result of the rigid nature of the impression material used, which results in an inaccurate impression of the oral tissues and undercuts surrounding the teeth. A material which is sufficiently elastic and that can be retrieved from the mouth without any defect is a solution for this issue. As a result, researchers invented flexible impression materials which can retain the elastic nature even after a complete set. The idea evolved from the making impressions of statutes using jelly molds. In 1925, an Austrian, Alphons Poller, invented and patented a material known as "Nogacoll." After Alphons Poller's death in 1931, the formula was attained by a company and given a new name: "Denticole."Many companies started manufacturing a similar material. All of these compounds were reversible hydrocolloids with agar-agar as their fundamental ingredient. This substance, which was a jelly-like substance, became soft when heated and hardened when cooled. The use of agar-agar was not convenient as it required special equipment such as heaters, syringes, and water-cooled rim lock trays. During the World War II, agar-agar was no longer available. Chemical treatment of brown algae led to the formation of a new elastic impression material which had an alginate base which is an irreversible hydrocolloid and was much easier to use. The alginate powder, when mixed with water, forms a gel, which is known as alginate. Agar-agar impression materials are no longer used in clinics because of the inconvenience of manipulation; whereas, alginates are still popularly advocated. Alginates remain an economical option and easily manipulated impression material.