Australian Dental Council (ADC) Practice Test 2026 – The All-in-One Guide to Exam Success!

The optimal positioning of the retentive part of a clasp is below the survey line. This positioning is crucial because clasps function to retain removable prostheses by engaging the undercuts of the abutment teeth. The survey line refers to the height achieved when the cast is surveyed and indicates the line where the tooth surface begins to diverge from being parallel to the path of insertion of the prosthesis.

By placing the retentive clasp element below this line, it effectively utilizes the undercut area of the tooth, providing a secure retention mechanism. This allows the prosthesis to be held more firmly in place while still permitting the removal of the prosthesis without causing trauma to the oral soft tissues or the tooth itself.

In contrast, positioning the retention above the survey line would not engage the undercut properly and may lead to inadequate retention. Similarly, placing it at the midpoint of the tooth might not achieve the necessary undercut engagement, while positioning it on top of the gingival margins could risk damage to the gum tissue, which is not ideal for maintaining periodontal health. This understanding highlights the importance of proper clasp design and positioning in achieving functional and comfortable prosthetic solutions.