Synthesis and Characterization of Sol-Gelled Barium Zirconate as Novel MTA Radiopacifiers.

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.

Endodontic Radiopacifying Application of Barium Titanate Prepared through a Combination of Mechanical Milling and Heat Treatment.

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.

Discoloration Improvement by Mechanically-Milled Binary Oxides as Radiopacifier for Mineral Trioxide Aggregates.

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.

Effect of Tantalum Pentoxide Addition on the Radiopacity Performance of Bi2O3/Ta2O5 Composite Powders Prepared by Mechanical Milling.

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 ß-Bi7.8Ta0.2O12.2, 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).

Effects of Milling Time, Zirconia Addition, and Storage Environment on the Radiopacity Performance of Mechanically Milled Bi2O3/ZrO2 Composite Powders.

Mineral trioxide aggregate (MTA) typically consists of Portland cement (75 wt.%), bismuth oxide (20 wt.%), and gypsum (5 wt.%) and is commonly used as endodontic cement. Bismuth oxide serving as the radiopacifying material reveals the canal filling effect after clinical treatment. In the present study, bismuth/zirconium oxide composite powder was prepared by high energy ball milling of (Bi2O3)100-x (ZrO2)x (x = 5, 10, 15, and 20 wt.%) powder mixture and used as the radiopacifiers within MTA. The crystalline phases of the as-milled powders were examined by the X-ray diffraction technique. The radiopacities of MTA-like cements prepared by using as-milled composite powders (at various milling stages or different amount of zirconia addition) were examined. In addition, the stability of the as-milled powders stored in an ambient environment, an electronic dry box, or a glove box was investigated. The experimental results show that the as-milled powder exhibited the starting powder phases of Bi2O3 and ZrO2 and the newly formed δ-Bi7.38Zr0.62O2.31 phase. The longer the milling time or the larger the amount of the zirconia addition, the higher the percentage of the δ-Bi7.38Zr0.62O2.31 phase in the composite powder. All the MTA-like cements prepared by the as-milled powder exhibited a radiopacity higher than 4 mmAl that is better than the 3 mmAl ISO standard requirement. The 30 min as-milled (Bi2O3)95(ZrO2)5 composite powder exhibited a radiopacity of 5.82 ± 0.33 mmAl and degraded significantly in the ambient environment. However, storing under an oxygen- and humidity-controlled glove box can prolong a high radiopacity performance. The radiopacity was 5.76 ± 0.08 mmAl after 28 days in a glove box that was statistically the same as the original composite powder.

An 8-year retrospective survey of assessment in postgraduate dental training in complicated tooth extraction competency.

BACKGROUND/PURPOSE: Direct observation of procedural skills (DOPS) has been increasingly used in health education in recent years. This study evaluated the effect of education and trainees' perception of assessment on the clinical skills of postgraduate dental trainees in complicated tooth extraction. MATERIALS AND METHODS: This study was conducted as a retrospective survey among postgraduate dental trainees learning complicated tooth extraction in Taipei and Linkou Chang Gung Memorial Hospital from 2012 to 2019. Practical skills were assessed using DOPS by trainees and faculty members. Each clinical case included a complicated extraction of a permanent tooth. RESULTS: A total of 69 participants (26 men and 43 women, average age = 26.49 years, range = 24-34 years) were included in this study. Within the survey cohort, faculty assessments scored significantly higher than did trainees' self-assessments in each complicated tooth extraction procedure, with no difference between both sexes. The higher-performing trainees tended to underrate their performance much more than did the lower-performing trainees. More than 40% of the trainees evaluated themselves as having "poor capability" in some invasive surgical procedures, even though their actual performance was not lower than that of those who evaluated themselves as having adequate or good capability. CONCLUSION: Self-assessment skills should be developed with more practice and experience. We hope that these findings can guide the planning of faculty development programs for clinical instructors, particularly the new cohort of faculty who will succeed the rapidly retiring boomer generation in the next 10 years.

Effect of Oxygen Concentration and Tantalum Addition on the Formation of High Temperature Bismuth Oxide Phase by Mechanochemical Reaction.

High-temperature face-centered cubic bismuth oxide phase is a material of great interest given its unique properties. In the present study, α-Bi2O3 and tantalum powders were used as the starting powders for the formation of high-temperature bismuth oxide phase via mechanochemical synthesis by high energy ball milling. (Bi2O3)80(Ta)20 and (Bi2O3)95(Ta)5 in weight concentrations were milled in either an oxygen-free argon-filled glove box environment or an ambient atmosphere to investigate the effects of oxygen concentration and tantalum addition. The as-milled powders were examined using X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, and differential scanning calorimetry to reveal the structural evolution. The experimental results showed that for (Bi2O3)95(Ta)5 powder mixtures milled within the glove box, tantalum gradually reacted with the α-Bi2O3 phase and formed a ß-Bi7.8Ta0.2O12.2 phase. For (Bi2O3)80(Ta)20 milled under the same conditions, Ta and α-Bi2O3 mechanochemically reacted to form δ-Bi3TaO7 and bismuth after 10 min of high energy ball milling, whereas milling (Bi2O3)80(Ta)20 under the ambient atmosphere with a much higher oxygen concentration accelerated the mechanochemical reaction to less than five minutes of milling and resulted in the formation of high-temperature δ-Bi3TaO7 phase.

Evaluation of the root and canal systems of maxillary molars in Taiwanese patients: A cone beam computed tomography study.

BACKGROUND: This study evaluated variations in root canal configuration in the maxillary permanent molars of Taiwanese patients by analyzing patients' cone beam computed tomography (CBCT) images. Comparisons were made among these configurations and those previously reported. This information may serve as a basis for improving the success rate of endodontic treatment. METHODS: The root canal systems of 114 Taiwanese patients with bilateral maxillary first or second molars were examined using CBCT images. The number of roots, canals per root, and additional mesiobuccal (MB) canals, as well as the canal configuration were enumerated and recorded. RESULTS: Of the 196 maxillary first molars examined, three (1.5%) had a single root, two (1.0%) had two roots, and 191 (97.5%) had three separate roots. Out of all first molar roots examined, 44% of mesiobuccal (MB) roots had a single canal and the remainder had a second MB (MB2) canal. Of the 212 maxillary second molars examined, 16 (7.1%) had a single root, 51 (24.2%) had two roots, 143 (67.8%) had three roots, and two (0.9%) had four separate roots. For the MB roots, 92.3% of three-rooted maxillary second molars had a single canal and the remainder had an MB2 canal. In all three-rooted maxillary first and second molars, each of the distal and palatal roots had one canal. CONCLUSIONS: The root canal configurations of the MB roots of maxillary molars were more varied than those of the distobuccal and palatal roots, and the root canal configurations of maxillary second molars were more varied than those of the first molars. These findings demonstrate CBCT as a useful clinical tool for endodontic diagnosis and treatment planning.

Maxillary reconstruction with a fibula osteoseptocutaneous free flap and simultaneous insertion of osseointegrated dental implants.

The fibula osteoseptocutaneous flap is a good option for reconstruction of three-dimensional composite maxillary defects. This flap provides both bone and soft-tissue reconstruction and allows osseointegrated dental implantation, either simultaneously or in a second-stage procedure. Simultaneous placement of osseointegrated dental implants reduces operative sessions and allows faster oral rehabilitation for properly selected patients. The defects may result from trauma or resection of benign tumors or low-grade malignancies. Between August of 1999 and July of 2001, three patients underwent maxillary reconstruction with the fibula osteoseptocutaneous flap and simultaneous osseointegrated dental implants. The cause of the defect was trauma in two cases and resection of an adenoid cystic carcinoma in the other. The mean length of the fibula used for bony reconstruction was 4.7 cm. One osteotomy was performed in one case and no osteotomy was necessary in the other two. Skin islands of 8 x 2.5 cm and 16 x 3.5 cm were used for two patients. For the other patient, a double skin island was used for both nasal (6 x 4 cm) and oral (6 x 5 cm) reconstructions. Two osseointegrated implants were inserted into the fibular bone for each patient. Six months after the first-stage procedure, palatal rotation flaps or mucosa grafts were used to cover the exposed implant necks and prepare the implants for prostheses. One month after the second-stage procedure, prostheses were placed. An implant-supported prosthesis was used for one patient and implant/tissue-supported prostheses were used for the others. At a mean follow-up time of 30 months (range, 16 to 38 months), all patients were able to use the dental prosthesis for chewing (beginning 6 weeks after the final procedure) and all patients were satisfied with the cosmetic results.

Segmental mandibulectomy and immediate free fibula osteoseptocutaneous flap reconstruction with endosteal implants: an ideal treatment method for mandibular ameloblastoma.

Thirteen patients with large ameloblastomas of the mandible underwent segmental mandibulectomy and immediate reconstruction, with simultaneous placement of osseointegrated implants. All patients received palatal mucosal grafts around the dental implants 6 to 10 months after surgical treatment and received implant-supported prostheses another 1 to 2 months later. There were five female and eight male patients, with a mean age of 32 years (range, 17 to 50 years). The mean length of the mandibular defect was 8.8 cm (range, 5 to 13 cm). All free fibula flap procedures were successful, with no reexplorations or partial flap losses. There was no clinical or radiographic evidence of failure during the osseointegration process for any implant. With functional occlusal loading, the marginal bone loss around the implants was less than 1.5 mm in a mean follow-up period of 40 months (range, 18 to 70 months). There were no recurrences during that time. The technique described allows improved access to the bone at the time of reconstruction, immediate assessment of alveolar ridge relationships, and accurate fixation of the implant-fibula construct. The advantages of this procedure include a reduced risk of recurrence with segmental resection, reliable mandibular reconstruction, and reduction of the number of surgical procedures, allowing full oral rehabilitation in a shorter time. It is concluded that segmental mandibulectomy and immediate vascularized fibula osteoseptocutaneous flap reconstruction, with simultaneous placement of osseointegrated implants, represent an ideal treatment method for large ameloblastomas of the mandible.