EFFECT OF VARIOUS SURFACTANTS AND ALUMINUM SOLUTIONS ON IN-VITRO ACIDDISSOLUTION OF DENTAL ENAMEL

Various surfactants were investigated for compatibility and stability in aqueous dispersions with aluminum (Al) and for their ability to inh ibit enamel acid dissolution both with and without Al present. A total of 39 samples, representing anionic, cationic and nonionic surfactant classes, were dispersed at a concentration of 1% in water or a 0.005 mol/l AIK(SO4)(2) solution. After 24 h the dispersions were evaluated for visual appearance, pH and ability to reduce enamel acid dissolutio n (EDR). Because reactions involving Al are sometimes very slow to equ ilibrate, the surfactants that were compatible with Al and did not sup press the 80% EDR of the Al solution were tested again after storage f or 12 months. Most surfactant samples formed limpid aqueous dispersion s that had little or no EDR activity. However, there were substantial differences in the effect of surfactants on Al EDR activity. Under the conditions of this study, nonionic samples from every subclass were c ompatible with Al. Anionics usually resulted in the formation of insol uble products that inactivated Al, although a polyethoxy carboxylate a nd a sulfated ester were exceptions which formed clear, stable dispers ions that yielded high EDR values. The cationics varied in their respo nse to Al; the amines reacted with and deactivated Al, but quaternary ammonium compounds were more compatible. No surfactants from any class enhanced the capacity of Al to reduce enamel acid dissolution. The lo ng-term stability data revealed that 21 of 22 Al-surfactant combinatio ns tested retained a significant EDR activity. However, some dispersio ns exhibited visual signs of instability, and the pH of many nonionic samples decreased. This study showed that, in the presence of Al, noni onic surfactants were relatively stable for long periods and did not b lock the ability of Al to inhibit enamel acid dissolution. However, ce rtain anionic and cationic surfactants also displayed comparable prope rties.