California Registered Dental Assistant (RDA) Written Practice Exam

According to manufacturer's directions, how long should etchant be left on tooth structure?

1. 10-15 seconds

2. 15-20 seconds

3. 30 seconds

4. 1 minute

The correct answer is: 15-20 seconds

Etchant is a solution that is used to prepare tooth structure before placing dental sealants or restorations. It contains an acid that helps create a rough surface for better bonding. Leaving etchant on the tooth structure for too long can cause over-etching, leading to potential damage to the tooth enamel. Therefore, it is important to follow the manufacturer's directions for the recommended time. In this case, options A, C, and D are all longer than the correct answer of 15-20 seconds, which can increase the risk of over-etching. Option A is also shorter than the recommended time. Thus, option B is the correct answer that follows the manufacturer's directions for optimal results.