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Impression materials are classified as either elastic or non-elastic based on mechanical properties.[1] Elastic materials are capable of stretching, compressing, and recovering after deformation. Elastic materials comprise reversible and irreversible hydrocolloids, addition and condensation silicones, polysulfides, and polyether.[2] Nonelastic or rigid impression materials include impression compounds, zinc oxide eugenol, and impression waxes.[2] Hydrocolloids were the first elastic materials used in the dental field. Hydrocolloids produce an imprint providing high-definition details despite undercuts. While the impressions deform upon removal, they later adapt to the original shape due to their elastic properties. Alginate is an elastic, irreversible hydrocolloid that offers lower costs, improved patient tolerance, ease of manipulation, reduced execution times, and the possibility of obtaining a detailed impression in a single step.
Creating dental impressions and the resulting dental casts is one of the best examples of collaborative work between dental clinicians, nurses, and laboratory technicians. The dentist selects the appropriate material and corresponding stock tray for the clinical case. The dental assistant usually mixes and loads the freshly made alginate into the tray. The dental assistants are also responsible for cleaning and disinfecting the impressions and either pouring them with gypsum or packing them to send to the laboratory. The package must contain documentation of adequate disinfection. The technician fabricates the impression if the impression arrives at the lab unpoured. Understanding the inherent properties of irreversible hydrocolloids reduces errors and improves patient outcomes.