Final answer:
Light body and heavy body impression materials are elastomeric substances used in dentistry to create detailed molds of teeth. The heavy body material captures the overall impression, while the light body material captures fine details. Together they provide a precise model for dental restorations.
Step-by-step explanation:
Light body and heavy body impression materials are used in dental procedures for making accurate impressions of a patient's teeth. These materials are types of elastomeric impression materials, differing in viscosity. The heavy body material is thicker and is used to capture the basic structure and overall impression of the teeth and gums. This material is generally loaded into a dental tray which is then positioned in the mouth, forming the primary layer of the impression.
Once the heavy body material is in place, the lighter body material, being more fluid, is injected specifically around the teeth to capture the fine details like contours, grooves and the gingival crevice. The light body material flows into the finer areas where the heavier material cannot reach, thus ensuring a highly detailed impression. When the two materials set, they create a definitive mold that can be used for making dental restorations and appliances, ensuring they fit the patient exactly.