Where is the retentive position on teeth according to the survey line?

The retentive position on teeth, as determined by the survey line, is crucial for understanding how removable partial dentures will engage with the available tooth structure. The correct answer indicates that the retentive position is located below the height of contour.

The height of contour is defined as the greatest diameter of the tooth when viewed from any angle, which typically aligns with the convex part of the crown's surface. When a survey line is established, it helps dental professionals identify where to place clasps or other retentive elements for optimal retention. Placing these retentive features below the height of contour ensures that they engage with the tooth structure effectively, allowing the prosthesis to stay securely in place while also accommodating periodontal health and aesthetics.

This positioning is essential because any retentive elements placed above the height of contour may not provide adequate support and could lead to dislodgement, thus diminishing the effectiveness of the dental prosthesis. Understanding these principles is vital for the successful design and implementation of oral prosthetics.