INBDE (Integrated National Board Dental Examination) Practice Exam

Why is self-etch not as effective?

1. It is too acidic

2. It leaves behind a smear layer

3. It is not acidic enough

4. It doesn't contain HEMA

The correct answer is: It leaves behind a smear layer

Self-etch adhesive systems are formulated to eliminate the need for a separate etching step by simultaneously priming and bonding to the tooth structure. However, one of the drawbacks of self-etch systems is that they can leave behind a smear layer on the dentin surface. This smear layer can inhibit the penetration of the adhesive into the dentinal tubules, leading to compromised bond strength. Therefore, the correct answer is B because the presence of a smear layer can reduce the effectiveness of self-etch adhesives. Option A is incorrect because the acidity of self-etch systems is carefully balanced to achieve optimal bonding without causing excessive demineralization of the tooth structure. Option C is incorrect as self-etch adhesives are designed to be moderately acidic to promote bonding. Option D is incorrect as the presence or absence of HEMA (2-hydroxyethyl methacrylate) does not solely determine the effectiveness of self-etch adhesives.