A nanoleakage perspective on bonding to oxidized dentin

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Adhesion Science

Background:

• Sodium hypochlorite (NaOCl) is widely used in dentistry but can reduce dentin bond strength.
• The exact mechanism behind this reduction and its reversal by reducing agents remains unclear.
• Nanoleakage is a key indicator of bond integrity in dentin bonding.

Purpose of the Study:

• To investigate the relationship between nanoleakage and the reversal of compromised dentin bonding after sodium hypochlorite treatment.
• To understand how reducing agents like sodium ascorbate affect bond strength and nanoleakage patterns.
• To elucidate the mechanism of bond strength reduction and restoration in dentin adhesives.

Main Methods:

• Acid-etched dentin specimens were treated with sodium hypochlorite to oxidize the collagen matrix.
• Two single-bottle dentin adhesives were applied to the treated dentin.
• Specimens were assessed for tensile bond strength and nanoleakage using ammoniacal silver nitrate and transmission electron microscopy.
• The effect of sodium ascorbate as a reducing agent on bond strength and nanoleakage was evaluated.

Main Results:

• Sodium hypochlorite significantly reduced tensile bond strength for both adhesives tested.
• Nanoleakage patterns changed from reticular to vertical, shag-carpet-like structures after NaOCl treatment.
• Sodium ascorbate treatment successfully reversed the reduction in bond strength and eliminated the observed nanoleakage.
• Complete depletion of the demineralized collagen matrix was observed after NaOCl application.

Conclusions:

• Residual sodium hypochlorite in dentin porosities may inhibit resin polymerization, leading to reduced bond strength.
• Sodium ascorbate effectively reverses NaOCl-induced bond strength reduction by mitigating nanoleakage.
• Understanding these mechanisms is crucial for optimizing dentin bonding protocols and adhesive material formulation.