What occurs during the process of border molding?

During the process of border molding, shaping the impression with fingers is the critical step that takes place. This technique involves manipulating the impression material around the periphery of the tray to create a more anatomically accurate shape that captures the details of the oral structures, such as the vestibule and borders of the edentulous areas. By using fingers to apply pressure and create a functional form, the dental assistant helps ensure that the impression will accurately reflect the patient's anatomy and function.

This detailed shaping is essential for achieving a proper fit for prosthetic devices, such as dentures, as it enhances retention and stability when the final restoration is placed. Additionally, this manipulation helps remove any undercuts, which could impede the seating of the prosthesis.

The other options do not encapsulate the specific actions involved in border molding. For instance, trimming models refers to the finishing process after the impressions have been taken, mixing materials pertains to preparing the impression material before use, and seating the tray properly relates to ensuring proper fit and positioning during the impression-taking process, rather than the active shaping of the impression edges.