Electrokinetically Resin-infiltrated Normal Enamel is Mechanically Protected From Cariogenic Challenge

Objectives: We used electrokinetic flow (EKF) to transport (without acid etching) a fluid resin infitrant into the nanopores of normal human enamel. The aim of this study was to test the null hypothesis that the mechanical properties (microhardness, MH, and ultimate tensile strength, UTS) of normal enamel submitted to acid challenge are similar regardless the existence of previous resin infiltration treatment with EKF.
Methods: Occlusal surfaces of extracted unerupted third molars were used in two experiments (MH and UTS), each one with both control (no treatment; n = 10) and experimental groups (resin infiltration treatment with EKF with 2 V for 2 h; n =10). In vitro artificial caries was induced in both groups after EKF. MH was evaluated at different distances from the enamel surface (up to 500 µm). UTS was tested with ground sections stressed both parallel and perpendicular to enamel prisms.
Results: MH values were higher in the experimental group up to 0.20 mm from the enamel surface (p < 0.01, paired T test; Hedge’s g ≥ 1.52; power ≥ 89%). UTS was significantly higher in the experimental group for both directions of stress in relation to enamel prisms: parallel (p = 0.004; Hedge’s g 7.7, power 99.9%) and perpendicular (p = 0.005; Hedge’s g 2.0; power 88%).
Conclusions: The null hypothesis was rejected, with EKF-driven resin infiltration promoting a protective effect on the mechanical properties of normal enamel against artificial caries formation.