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.
Highlights
Human tooth enamel is mostly composed of calciumand phosphorus-rich minerals
21 samples were discarded, whereas the remaining 30 samples were randomly divided into three groups: Untouched Enamel (UE), Demineralized Enamel (DE) and Demineralized Enamel Treated with Enamel Matrix Derivative (EMD) (ET)
The acid treatment selected in the current study to simulate enamel demineralization lesion is in compliance with parameters used in similar researches, which adopted a wide variety of methodologies, whose protocols included from the direct application of 30% phosphoric acid for 30 s (9,11) to holding samples in buffered acidic solution for 18 days prior to enamel acid etching (5)
Summary
Human tooth enamel is mostly composed of calciumand phosphorus-rich minerals. Apatite crystals’ development during amelogenesis is directed by an organic matrix made of proteins, mainly of amelogenins. Amelogenins are responsible for regulating the mineralization process and for organizing apatite crystals into juxtaposed prisms (1). Certain external factors may lead to partial loss of enamel, whose restoration process should meet some requirements in order to assure its durability and aesthetics. Enamel regeneration has been investigated as an alternative way to replace these losses. The biomimetic approach recommends adopting techniques inspired in natural processes, according to which the matrix reestablishment process guides tissue growth (2)
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