Effects of poly(amidoamine) as an extrafibrillar demineralization agent on dentin bonding durability of deciduous teeth

Abstract

Objectives

To investigate the effects of the sixth generation of poly(amidoamine) (G6-PAMAM)-based extrafibrillar demineralization on bonding durability of deciduous dentin and explore the possible mechanisms.

Methods

The cytotoxicity and inhibitory effects on recombinant human matrix metalloproteinases-9 (rhMMP-9) of G6-PAMAM were investigated. The chelation demineralization capacity of G6-PAMAM with molecular weight > 40 kDa was quantitatively analyzed. Atomic force microscopy-infrared spectroscopy (AFM-IR) was used to verify selective extrafibrillar demineralization of dentin conditioned by G6-PAMAM. After dentin surfaces were conditioned with G6-PAMAM or phosphoric acid (H₃PO₄), G6-PAMAM- and H₃PO₄-conditioned dentin were applied with adhesive restoration using both wet- and dry-bonding technique. Microtensile bond strength (μTBS) was evaluated after 24 h storage or 10,000 thermocycling. Nanoleakage expression at the bonding interface was observed using field emission scanning electron microscopy. Gelatinolytic activity within the hybrid layer was examined using in situ zymography.

Results

In addition to being nontoxic, 20 µg/mL G6-PAMAM showed inhibitory effects on rhMMP-9 and calcium-chelating capability. AFM-IR confirmed that G6-PAMAM conditioning can achieve selective demineralization of dentin extrafibrillar minerals. Deciduous dentin treated with 20 µg/mL G6-PAMAM for 60 s produced μTBS equivalent to H₃PO₄-based etch-and-rinse technique. Those bond strengths were maintained after thermocycling, irrespective of wet-bonding or dry-bonding. G6-PAMAM conditioning produced less nanoleakage and suppressed endogenous gelatinolytic activity compare with H₃PO₄ etching.

Conclusion

The G6-PAMAM-based extrafibrillar demineralization strategy under dry-bonding technique could enhance bonding durability of deciduous dentin by retaining intrafibrillar minerals, decreasing interfacial nanoleakage, and preventing endogenous protease-initiated collagen degradation.

Clinical relevance

The G6-PAMAM-based extrafibrillar demineralization strategy has the potential to improve the stability of the resin-dentin bonding interface and prolong the longevity of resin restorations in deciduous teeth.