Facilitation of iontophoretic drug delivery through intact and caries-affected dentine.

Aim: To investigate the facilitative role of iontophoresis in drug delivery through intact and caries-affected dentine into the pulp.

Methodology: Forty-eight intact dentine or caries-affected dentine discs were prepared from freshly extracted human third molars. The hydraulic conductance was measured before and after the experiments. Drug diffusion with and without iontophoresis (0.05 mA, 10 min) was evaluated using a split-chamber device. The enamel side chamber was filled with metronidazole (MN), sodium salicylate (SS) or naproxen sodium (NA), while the pulpal side was circulated with phosphate buffered saline (PBS) and pressurized (15 cmH2O). Samples were collected after 1 h. Drug concentrations of the pulpal side solution were determined using a spectrophotometer. Then, electrical impedance of each dentine disc was measured. Finally, the dentine disc surfaces were observed by scanning electron microscopy.

Results: Drug diffusion was significantly influenced by iontophoresis, caries-induced changes in dentine and the drugs used (three-way anova, P < 0.05). The diffusion of all the drugs through caries-affected dentine was significantly less than that through intact dentine (independent t-test, P < 0.05). Also, iontophoresis facilitated the diffusion of all the drugs through intact and caries-affected dentine. The drug diffusion of SS was significantly higher than MN and NA (one-way anova, P < 0.05), independent of iontophoresis.

Conclusions: Presence of dental caries may inhibit drug diffusion through dentine into the pulp. However, iontophoresis could enhance the delivery of ionized drugs through both intact and caries-affected dentine.