Morphology of Enamel After Perfusion with Acid and Toothpastes Application

Objectives: to evaluate the effect of perfusion with lactic acid solution on enamel surface and the role of toothpastes in preventing surface alterations. Methods: buccal enamel samples were obtained from human extracted teeth (age 50-70 years. Samples were immersed in a perfusion pump device working at 37 °C in which lactic acid solution (pH 4.4) alternatively with deionized water was perfused at constant flow for 72 hours in order to obtain a laminar flux of solution. Samples were treated with toothpaste CPL (Complete, Procter & Gamble, USA; n=10) or AZV (AZ Verde, Procter & Gamble, USA; n=10) in the distal half of enamel sample three times a day for a total of nine applications. Perfusion flux was stopped only before toothpaste application. Toothpaste was applied on each sample with a small brush for 3 minutes, gently scrubbed, removed with water and then each sample was re-perfused. A preliminary replica of enamel surface was obtained with a polivinilxyloxane impression material (President light, Coltene, Switzerland) and additional replicas were obtained after 24, 48 and 72 hours of perfusion. Each replica was then impressed in a polyether material (Permadyne Garant 2:1, 3M ESPE, USA) and finally inspected at SEM: Number of voids, removal of inter- and intraprismatic enamel were used as index for enamel alterations. Results: untreated enamel was greatly damaged by perfused acid solution just after 24 hours. Enamel treated with CPL resulted less affected by alterations and relatively free from voids. A similar number of fractures and delamination was observed in AZV samples but with a greater extension of interprismatic lesions. Conclusions: toothpastes are able to protect enamel surface perfused by constant fluid flow lactic acid solution.