What is the primary purpose of an impression in dentistry?

The primary purpose of an impression in dentistry is to form a mold for future reference. Impressions are taken to capture the precise contours of a patient’s teeth and surrounding tissue, providing a detailed model that dentists and dental technicians can use for various purposes. This includes creating restorations such as crowns, bridges, or dentures, ensuring they fit accurately in the patient's mouth.

The process of taking an impression involves applying a material that will harden into a negative mold, which can then be used to produce either a positive replica or a dental cast. These molds are essential for fabricating dental appliances and can also guide the dentist in planning treatments.

The other options, while related to dental procedures, do not accurately define the primary purpose of an impression. Creating a dental crown indeed utilizes impressions, but it is not the foundational purpose itself; rather, it's a result of having that mold. Evaluating tooth decay is typically conducted through visual examination or X-rays rather than through impressions. Finally, filling dental cavities is a separate procedure that addresses decay in existing teeth and does not require an impression.