Influence of Storage on De- and Remineralization of Bovine Dentin

Objectives: The aim of this investigation was to compare the influence of various storage solutions on the de- and remineralization of bovine dentin in vitro. Methods: 100 freshly extracted and carefully cleaned bovine incisors were divided randomly into five groups and stored immediately after extraction in five various solutions [NaCl 0.9%; Accustain® Formalin Solution 10% (Sigma-Aldrich, Steinheim, Germany); Isopropyl-alcohol 70%; H₂O₂ 3%; Thymol 0.1%] at room temperature. After ten months, a cylindrical dentin block was obtained from each incisor. Additionally, 20 blocks from freshly extracted bovin teeth were prepared (control). The specimens were embedded in epoxy resin, ground flat and partly covered with nail varnish. After demineralization in Buskes` solution (pH 5.5; 7 d), parts of the demineralized area were also covered with nail varnish and the specimens exposed to a remineralizing solution (18 d). Lesion depth (LD) and mineral loss (ΔZ) were evaluated from microradiographs of thin sections (110 µm) by a dedicated software package (TMR 1.24, ethylene glycol). Results: Compared with control, dentin stored in formalin, alcohol and H₂O₂ showed significantly lower LDs in the demineralized area (formalin: p=0.043, alcohol: p=0.000, H₂O₂: p=0.017; Mann-Whitney test) and also a significantly slower decrease of LD in the remineralized area (formalin: p=0.000, alcohol: p=0.000, H₂O₂: p=0.004; Mann-Whitney test). Furthermore, some of the storage solutions significantly affected the mineral content, which resulted in higher levels of mineral content in the demineralized area (alcohol: p=0.004; Mann-Whitney test) and a slower increase in the remineralized area (formalin: p=0.001, alcohol: p=0.000, thymol: p=0.014; Mann-Whitney test). Conclusion: Storage of bovine teeth in formalin, alcohol, H₂O₂ and thymol seems to influence de- and remineralization of dentin. No significant effects were seen after storage in NaCl, which might be suitable as a storage solution.