Effect of Protein-Based Treatment on Chemical Composition, Hardness and Bond Strength of Remineralized Enamel

Abstract

This study evaluated the chemical composition and microhardness of human enamel treated with an Enamel Matrix Derivative (EMD) solution, and the bond strength between composite resin and this enamel. Thirty human enamel samples were randomly divided into three groups: Untouched Enamel (UE), Demineralized Enamel (DE) and Demineralized Enamel Treated with EMD (ET). DE and ET groups were subjected to acid challenge and ET treated with EMD (EMD was directly applied over conditioned enamel and left for 15 min). Samples from each group (n=4) had chemical composition assessed through to attenuated total reflectance Fourier transform infrared (ATR-FTIR). Knoop microhardness of enamel samples from each group (n=10) was measured. For the microshear bond strength, the samples were etched for 30 s, and the adhesive was applied and cured for 10 s. Two matrixes were placed on the samples, filled with Filtek Z350 XT composite and cured for 20 s, each. The matrix was removed, and the microshear bond strength of each group (n=10) was tested. Data were subjected to Kruskal-Wallis test (for microhardness), to analysis of variance and to Tukey’s test (for microshear bond strength); (α=0.05). FTIR results have shown phosphate (hydroxyapatite indicator) in 900-1200 cm-1 bands in the UE and ET groups, which were different from the DE group. Microhardness and microshear analyses recorded higher statistical values for the UE and ET groups than for DE. EMD application to demineralized enamel seems to have remineralized the enamel; thus, the microhardness and bond strength was similar between UE and ET groups.

Effect of Amelogenin Solution in the Microhardness of Remineralized Enamel and Shear Bond Strength of Orthodontic Brackets

“…Results recorded for hardness control during samples' treatment at T 0 and T 2 are in compliance with previous studies [ 22 ], which used the same sample treatment methodology. TE group has shown Knoop hardness recovery at T 2, and it indicated successful remineralization of samples subjected to treatment with amelogenin solution.…”

“…Enamel surface featuring through hardness test is often adopted in this type of study to check enamel mineralization. It can be easily performed at each method stage, and it does not compromise or damage samples subjected to shear test [ 14 , 17 , 18 , 22 , 26 ].…”

“…All samples had their microhardness evaluated at three different points in a microhardness tester (HMV-G; Shimadzu, Kyoto, Japan). Results recorded for the initial microhardness test were tabulated, and samples were randomly divided into three experimental groups with 8 samples ( n = 8) according to treatment: the SE group (sound enamel, untreated) was kept under refrigeration in humid environment (RH 100%), and the DE (demineralized enamel) and TE groups (demineralized enamel, treated with emdogain enamel matrix protein solution (Straumann AG, Basel, Switzerland), which presents as clear gel in a 0.7 ml syringe) were subjected to pH cycling [ 22 ].…”

“…Samples from the TE group were subjected to acid etching with 37% acid gel (Villevie, Joinville, SC, Brazil) for 20 seconds, washed with water and air jets for 40 seconds, dried with superficial air jets, and subjected to amelogenin solution application for 15 minutes, according to the previously established methodology [ 22 ]. The product was applied in its nondiluted form, in a layer at of least 1 mm (in thickness) that completely covered the exposed tooth enamel surface.…”