Modeling Plastic

 Impression Compound is a rigid, thermoplastic material used in dentistry primarily for border molding of custom denture trays and preliminary impressions of edentulous arches. Softened by heat and hardened by cooling, it allows for precise functional molding of vestibular borders but cannot be elastically withdrawn from undercuts. Its use demands careful temperature control to avoid burns and ensure proper flow, making it a technique-sensitive material. While largely supplanted by modern elastomers for most impressions, it remains a valuable and sometimes irreplaceable tool in advanced complete denture prosthodontics and certain corrective impression techniques.