Restorative & Materials · single question
Which action will most likely cause the collapse of collagen fibrils during bonding procedures?
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Correct answer: B. Excess drying
After acid etching removes the smear layer, the exposed collagen network must remain hydrated (moist). Excess drying causes the demineralized collagen fibrils to collapse ('dry bonding'), preventing adequate penetration of the adhesive resin. This creates a weak hybrid layer with many voids. The key is to leave the dentin 'moist but not wet' after rinsing the etchant.
- A. INCORRECT. Excess preparation (over-cutting) removes more tooth structure but does not specifically cause collagen collapse.
- B. CORRECT. Excess drying after acid etching causes the exposed, unsupported collagen fibrils to collapse due to surface tension. The collapsed collagen cannot be re-expanded by the adhesive, resulting in poor hybrid layer formation and reduced bond strength.
- C. INCORRECT. Excess etching can over-etch dentin (deeper demineralization), but this does not directly cause collagen COLLAPSE — it creates deeper demineralized zones that adhesive cannot fully penetrate, a different failure mode.
- D. INCORRECT. Excess bonding agent application (over-applying adhesive) can create thick layers that don't polymerize well, but this is not the mechanism of collagen fibril collapse.
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