Effects of phytic and tannic acids on dentin bonding, nanoleakage, and micropermeability under wet and dry bonding techniques

Acid-conditioned dentin may contain exposed collagen fibrils that are vulnerable to hydrolytic degradation when resin infiltration is incomplete. Thus, alternative acidic conditioners with dentin-biomodifying potential may help improve resin-dentin interface stability. This study investigated the effects of dentin biomodification with phytic acid (IP6), tannic acid (TA), and glutaraldehyde (GLU) on resin-dentin bonding performance under dry and wet conditions. Seventy-two extracted human molars were assigned to eight groups according to the dentin conditioning agent and bonding protocol: 37% phosphoric acid for 15 s (Control), 5% GLU for 30 s, 1% IP6 (pH 1.2) for 30 s, and 20% TA (pH 2.8) for 30 s, applied under dry or wet dentin conditions. Adper™ Single Bond 2 was applied, and resin-dentin specimens were prepared for microtensile bond strength testing (µTBS; n = 6), nanoleakage analysis (NL; n = 1), and micropermeability evaluation (MP; n = 2). Half of the specimens were tested after 24 h and the remaining half after 6 months of water storage. NL was assessed by SEM/EDS, MP by confocal laser scanning microscopy, and µTBS data by two-way ANOVA and Tukey's test (α = 0.05). TA showed significantly lower µTBS values than the Control and GLU groups under both bonding conditions and at both periods (p < 0.001). Compared with IP6, TA exhibited lower µTBS in all conditions, except under wet bonding at 24 h, where no significant difference was observed (p > 0.05). No significant reduction in µTBS after 6 months was observed for the Control, GLU, and IP6 groups (p > 0.05). Under dry bonding, IP6 reduced silver nitrate deposition, whereas TA showed greater silver uptake. Under wet bonding, IP6 showed increased interfacial infiltration, while TA displayed reduced NL despite lower bond strength. MP analysis revealed reduced fluorescein penetration and improved sealing for IP6- and TA-treated dentin. The highest µTBS values occurred in the IP6 Dry 24 h group. IP6 showed the most favorable overall performance, maintaining bond strength over time while reducing NL and improving sealing.