| Summary: | Mineral trioxide aggregates (MTA) have been developed as a dental root repair material for a range of endodontics procedures. They contain a small amount of bismuth oxide (Bi<sub>2</sub>O<sub>3</sub>) as a radiopacifier to differentiate adjacent bone tissue on radiographs for endodontic surgery. However, the addition of Bi<sub>2</sub>O<sub>3</sub> to MTA will increase porosity and lead to the deterioration of MTA’s mechanical properties. Besides, Bi<sub>2</sub>O<sub>3</sub> can also increase the setting time of MTA. To improve upon the undesirable effects caused by Bi<sub>2</sub>O<sub>3</sub> additives, we used zirconium ions (Zr) to substitute the bismuth ions (Bi) in the Bi<sub>2</sub>O<sub>3</sub> compound. Here we demonstrate a new composition of Zr-doped Bi<sub>2</sub>O<sub>3</sub> using spray pyrolysis, a technique for producing fine solid particles. The results showed that Zr ions were doped into the Bi<sub>2</sub>O<sub>3</sub> compound, resulting in the phase of Bi<sub>7.38</sub>Zr<sub>0.62</sub>O<sub>12.31</sub>. The results of materials analysis showed Bi<sub>2</sub>O<sub>3</sub> with 15 mol % of Zr doping increased its radiopacity (5.16 ± 0.2 mm Al) and mechanical strength, compared to Bi<sub>2</sub>O<sub>3</sub> and other ratios of Zr-doped Bi<sub>2</sub>O<sub>3</sub>. To our knowledge, this is the first study of fabrication and analysis of Zr-doped Bi<sub>2</sub>O<sub>3</sub> radiopacifiers through the spray pyrolysis procedure. The study reveals that spray pyrolysis can be a new technique for preparing Zr-doped Bi<sub>2</sub>O<sub>3</sub> radiopacifiers for future dental applications.
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