Application of poly(amidoamine)-inositol hexakisphosphate conjugates for improving resin-dentine bond longevity

To synthesise and evaluate a bioactive poly(amidoamine)-inositol hexakisphosphate (PAMAM-IP6) conjugate as a selective extrafibrillar dentine demineralisation conditioner designed to preserve intrafibrillar minerals, inhibit dentinal protease activity, and enhance the durability of resin-dentine bonds.

The conjugate was synthesised by conjugating IP6 to high-molecular weight PAMAM dendrimer with amino terminal groups and characterised using ATR-FTIR, proton NMR, and ¹³C NMR spectroscopy. Calcium chelation capacity was determined by inductively coupled plasma-atomic emission spectrometry. The optimal concentration and conditioning time were identified through tensile bond strength testing under wet- and dry-bonding conditions before and after thermocycling. Morphological features were evaluated using field emission scanning electron microscopy and atomic force microscopy. Endogenous gelatinolytic activity was evluated by in-situ zymography. Antibacterial efficacy against Streptococcus mutans and Enterococcus faecalis was analysed using live/dead bacterial staining.

PAMAM-IP6 provided effective calcium chelation with partial extrafibrillar demineralisation and preservation of intrafibrillar minerals. Conditioning dentine with 50 mg/mL PAMAM-IP6 for 30 s achieved bond strengths comparable to those obtained with 37 % phosphoric acid and maintained stability after thermocycling. In-situ zymography revealed markedly reduced gelatinolytic activity relative to phosphoric acid. Antibacterial testing demonstrated substantial bacterial inhibition. PAMAM-IP6 showed low cytotoxicity towards human dental pulp cells.

PAMAM-IP6 selectively demineralises extrafibrillar dentine, preserves collagen integrity, inhibits endogenous proteases, and exhibits antibacterial activity, thereby improving the durability of resin-dentine bonds.

The PAMAM-IP6 conditioner offers a biomodulatory approach for dentine bonding by preserving intrafibrillar minerals and preventing collagen degradation. Its protease-inhibiting and antibacterial properties support improved clinical longevity of adhesive restorations and enable reliable bonding under both wet and dry bonding conditions.