Purpose: To determine the long-term ultimate tensile strength (UTS) and modulus of elasticity (E) of EDTA-demineralized human dentin after storage in PBS (phosphate buffered saline) for up to 48 months.
Materials and methods: Dentin beams measuring 0.7 x 0.7 x 8.0 mm were prepared from the crowns of extracted human third molars. The ends of the beams were covered with resin composite and demineralized for 6 days in 0.5 mol/L EDTA (pH = 7.0). Demineralized control specimens were subjected to tensile testing at 0.5 mm/min after 24 hours of immersion in PBS solution. Experimental specimens were stored in PBS at room temperature (25 degrees C) and tested after 18 and 48 months. The maximum load at failure and the load/displacement curves were used to calculate the UTS as a function of the cross-sectional area and E, respectively. The results were analyzed by ANOVA and Student Neuman Keuls tests. TEM micrographs were obtained from the control specimens and from those that were stored and tested after 48 months.
Results: No significant changes in either UTS or E were observed in the specimens after long-term storage. The 48-month values were not statistically significantly different from the values obtained at 24 hours (p > 0.05). TEM images revealed a normal, intact structure of the collagen fibrils with no signs of degradation or denaturation.
Conclusion: Long-term storage of EDTA-demineralized human dentin in PBS solution did not cause any significant reduction of its mechanical properties. The structure of the collagen fibrils as observed by TEM appeared normal and did not seem affected by long-term storage.