Self-Etch vs Total-Etch Adhesives — MFDS Part 1 MCQ

Correct answer: D — It uses an acidic primer to demineralise and prime, so a separate phosphoric acid etch-and-rinse step is not mandatory.

Explanation lettering: C = shown as A · E = shown as C · A = shown as D · D = shown as E

A is correct. In a two-step self-etch system, acidic functional monomers in the primer demineralise and prime the tooth surface concurrently; the primer is not rinsed away, and a separate phosphoric-acid etch-and-rinse stage is not required. By contrast, etch-and-rinse systems condition tooth tissue with phosphoric acid before rinsing and applying primer and adhesive. Therefore, B and C describe incorrect handling sequences, while E incorrectly attributes complete smear-layer removal to the self-etch approach. Silane is a coupling agent used principally when bonding to silica-containing restorative materials and does not replace tooth primer, so D is incorrect. Selective phosphoric-acid etching of enamel may sometimes supplement a self-etch strategy to improve enamel bonding, but it is not the defining self-etch mechanism.

Reference: Sofan E et al. Self-etch and etch-and-rinse adhesive systems in clinical dentistry. Dentistry. 2013. https://pubmed.ncbi.nlm.nih.gov/30799468/