Mesoporous bioactive glass (MBG) is an advanced biomaterial widely recognized for its application in bone regenerative engineering. This study synthesized an MBG powder (80 mol% SiO₂, 5 mol% P₂O₅, and 15 mol% CaO) using a facile sol-gel method with the non-ionic surfactant Pluronic^® P123, which acted as a pore-forming agent. MBGs form bioactive surfaces that facilitate HA formation, and the presence of Pluronic^® P123 increases the surface area and promotes HA nucleation. Various percentages of strontium (Sr) doping were examined to improve bioreactivity, biological response, and bone formation, with 3SMBG (3 mol% Sr) showing the highest specific surface area. In vitro biocompatibility tests revealed HA formation on all glass surfaces after immersion in simulated body fluid (SBF), indicated by sheet-like HA morphologies, the presence of PO₄³⁻ and CO₃²⁻ functional groups, and the amorphous structure along with SrCO₃ crystalline phases corresponding to HA and Sr-HA structures. Sr doping resulted in delayed initial degradation and sustained release of Sr²⁺, achieving over 95% cell viability. Surfactant-induced mesoporous structure and Sr incorporation synergistically enhance osteocyte induction and formation in vitro. These findings suggest that Sr-doped MBG, particularly with P123-assisted Sr/Ca substitution, optimizes the material’s properties for advanced bone regenerative applications.

Mineral trioxide aggregates (MTA) have been widely used in endodontic treatments, but after some time, patients suffer tooth discoloration due to the use of bismuth oxide (Bi₂O₃) as a radiopacifier. Replacement of Bi₂O₃ with high energy ball-milled single (zirconia ZrO₂; hafnia, HfO₂; or tantalum pentoxide, Ta₂O₅) or binary oxide powder was attempted, and corresponding discoloration improvement was investigated in the present study. Bi₂O₃-free MTA is expected to exhibit superior discoloration. The radiopacity, diametral tensile strength, and discoloration of MTA-like cements prepared from the as-milled powder were investigated. Experimental results showed that MTA-like cements prepared using Ta₂O₅ exhibited a slightly higher radiopacity than that of HfO₂ but had a much higher radiopacity than ZrO₂. Milling treatment (30 min to 3 h) did not affect the radiopacities significantly. These MTA-like cements exhibited superior color stability (all measured ΔE₀₀ < 1.0) without any perceptible differences after UV irradiation. MTA-like cements prepared using ZrO₂ exhibited the best color stability but the lowest radiopacity, which can be improved by introducing binary oxide. Among the investigated samples, MTA-like cement using (ZrO₂)₅₀(Ta₂O₅)₅₀ exhibited excellent color stability and the best overall performance with a radiopacity of 3.25 mmAl and a diametral tensile strength of 4.39 MPa.

Among the various phases of bismuth oxide, the high temperature metastable face-centered cubic δ phase attracts great attention due to its unique properties. It can be used as an ionic conductor or an endodontic radiopacifying material. However, no reports concerning tantalum and bismuth binary oxide prepared by high energy ball milling and serving as a dental radiopacifier can be found. In the present study, Ta₂O₅-added Bi₂O₃ composite powders were mechanically milled to investigate the formation of these metastable phases. The as-milled powders were examined by X-ray diffraction and scanning electron microscopy to reveal the structural evolution. The as-milled composite powders then served as the radiopacifier within mineral trioxide aggregates (i.e., MTA). Radiopacity performance, diametral tensile strength, setting times, and biocompatibility of MTA-like cements solidified by deionized water, saline, or 10% calcium chloride solution were investigated. The experimental results showed that subsequent formation of high temperature metastable β-Bi_7.8Ta_0.2O_12.2, δ-Bi₂O₃, and δ-Bi₃TaO₇ phases can be observed after mechanical milling of (Bi₂O₃)₉₅(Ta₂O₅)₅ or (Bi₂O₃)₈₀(Ta₂O₅)₂₀ powder mixtures. Compared to its pristine Bi₂O₃ counterpart with a radiopacity of 4.42 mmAl, long setting times (60 and 120 min for initial and final setting times) and 84% MG-63 cell viability, MTA-like cement prepared from (Bi₂O₃)₉₅(Ta₂O₅)₅ powder exhibited superior performance with a radiopacity of 5.92 mmAl (the highest in the present work), accelerated setting times (the initial and final setting time can be shortened to 25 and 40 min, respectively), and biocompatibility (94% cell viability).

Barium zirconate (BaZrO₃, BZO), which exhibits superior mechanical, thermal, and chemical stability, has been widely used in many applications. In dentistry, BZO is used as a radiopacifier in mineral trioxide aggregates (MTAs) for endodontic filling applications. In the present study, BZO was prepared using the sol–gel process, followed by calcination at 700–1000 °C. The calcined BZO powders were investigated using X-ray diffraction and scanning electron microscopy. Thereafter, MTA-like cements with the addition of calcined BZO powder were evaluated to determine the optimal composition based on radiopacity, diametral tensile strength (DTS), and setting times. The experimental results showed that calcined BZO exhibited a majority BZO phase with minor zirconia crystals. The crystallinity, the percentage, and the average crystalline size of BZO increased with the increasing calcination temperature. The optimal MTA-like cement was obtained by adding 20% of the 700 °C-calcined BZO powder. The initial and final setting times were 25 and 32 min, respectively. They were significantly shorter than those (70 and 56 min, respectively) prepared with commercial BZO powder. It exhibited a radiopacity of 3.60 ± 0.22 mmAl and a DTS of 3.02 ± 0.18 MPa. After 28 days of simulated oral environment storage, the radiopacity and DTS decreased to 3.36 ± 0.53 mmAl and 2.84 ± 0.27 MPa, respectively. This suggests that 700 °C-calcined BZO powder has potential as a novel radiopacifier for MTAs.

Carburized steel shafts are commonly used in industry due to their good wear resistance and fatigue life. If the surface of carburized shafts exhibits an undesired tensile stress, shot peening treatment may be required to alter the stress condition on the surface. In the present study, the effects of shot peening pressure (3–5 kg/cm²), time (32–64 s), and material (stainless steel, carbon steel, and glass) on the residual stress, retained austenite, microhardness, and surface roughness of the carburized shafts were investigated. The experimental results showed that the surface residual tensile stress was changed into compressive stress after the shot peening treatment. The shot peening effects increased with the increasing peening pressure and time. In addition, a significant decrease in the amount of retained austenite in the subsurface region was observed. Peening with different materials can affect the peening effect. Using glass pellets exhibited the best shot peening effect but suffered massive pellet fracture during processing. In overall consideration, the optimal peening parameters for carburized steel shafts for practical industrial applications involved using the stainless-steel pellets with a peening pressure of 5 kg/cm² and a peening time of 64 s. The maximum residual stress was −779 MPa at a depth of 0.02 mm, while the highest surface microhardness was 827 HV_0.1.

Mineral trioxide aggregates (MTA) are commonly used as endodontic filling materials but suffer from a long setting time and tooth discoloration. In the present study, the feasibility of using barium titanate (BTO) for discoloration and a calcium chloride (CaCl₂) solution to shorten the setting time was investigated. BTO powder was prepared using high-energy ball milling for 3 h, followed by sintering at 700–1300 °C for 2 h. X-ray diffraction was used to examine the crystallinity and crystalline size of the as-milled and heat-treated powders. MTA-like cements were then prepared using 20–40 wt.% BTO as a radiopacifier and solidified using a 0–30% CaCl₂ solution. The corresponding radiopacity, diametral tensile strength (DTS), initial and final setting times, and discoloration performance were examined. The experimental results showed that for the BTO powder prepared using a combination of mechanical milling and heat treatment, the crystallinity and crystalline size increased with the increasing sintering temperature. The BTO sintered at 1300 °C (i.e., BTO-13) exhibited the best radiopacity and DTS. The MTA-like cement supplemented with 30% BTO-13 and solidified with a 10% CaCl₂ solution exhibited a radiopacity of 3.68 ± 0.24 mmAl and a DTS of 2.54 ± 0.28 MPa, respectively. In the accelerated discoloration examination using UV irradiation, the color difference was less than 1.6 and significantly lower than the clinically perceptible level (3.7). This novel MTA exhibiting a superior color stability, shortened setting time, and excellent biocompatibility has potential for use in endodontic applications.