Abstract Calcium aluminate cement (CAC) has been highlighted as a promising alternative for endodontic use aiming at periapical tissue repair. However, its effects on dental pulp cells have been poorly explored. Objective: This study assessed the impact of calcium chloride (CaCl2) and bismuth oxide (Bi2O3) or zinc oxide (ZnO) additives on odontoblast cell response to CAC. Methodology: MDPC-23 cells were exposed for up to 14 d: 1) CAC with 2.8% CaCl2 and 25% ZnO (CACz); 2) CAC with 2.8% CaCl2 and 25% Bi2O3 (CACb); 3) CAC with 10% CaCl2 and 25% Bi2O3 (CACb+); or 4) mineral trioxide aggregate (MTA), placed on inserts. Non-exposed cultures served as control. Cell morphology, cell viability, gene expression of alkaline phosphatase (ALP), bone sialoprotein (BSP), and dentin matrix protein 1 (DMP-1), ALP activity, and extracellular matrix mineralization were evaluated. Data were compared using ANOVA (α=5%). Results: Lower cell density was detected only for MTA and CACb+ compared with Control, with areas showing reduced cell spreading. Cell viability was similar among groups at days one and three (p>0.05). CACb+ and MTA showed the lowest cell viability values at day seven (p>0.05). CACb and CACb+ promoted higher ALP and BSP expression compared with CACz (p<0.05); despite that, all cements supported ALP activity. Matrix mineralization were enhanced in CACb+ and MTA. Conclusion: In conclusion, CAC with Bi2O3, but not with ZnO, supported the expression of odontoblastic phenotype, but only the composition with 10% CaCl2 promoted mineralized matrix formation, rendering it suitable for dentin-pulp complex repair.

The radiopacity of CAC-based compositions containing additives (ZnO, Ag and Bi2O3) was evaluated by optical density measurements, cold crushing strength, apparent porosity, pore size distribution, in vitro apatite-formation ability (bioactivity) and cell viability. The bioactivity was assessed via pH and calcium concentration measurements in simulated body fluid (SBF) for samples previously treated or not with sodium silicate (SS) solution. The surface of the samples after treatment was analyzed by scanning electron microscopy, energy dispersive X-ray analysis and confocal Raman spectroscopy. Cell viability was evaluated by MTT and alkaline phosphatase (ALP) activity. Radiopacity results confirmed that compositions containing ZnO-Ag (25:1 wt%) and ZnO-Bi2O3 (15:10 wt%) presented suitable values of radiopacity (> 3 mmAl). The identification of calcium and mainly phosphorus by EDX, highlighted the generation of an apatite-like layer on the compositions' surface after immersion in SBF or SBF/SS. CAC-blend containing 25 wt% ZnO, ZnO-Ag and ZnO-Bi2O3 presented slightly lower cell viability compared to the positive control.

ABSTRACTNumerous papers and publications report the use of microporous calcium hexaluminate (CaO.6Al2O3; CA6) as a key raw material for high temperature insulating materials. This material has unique properties with respect to chemical purity and mineral composition. Another important property of CA6 is its structure, which consists of platelet-shaped crystals that interlock. The free distance between the crystals defines the microporous structure. The low density in combination with the micropores hampers heat transfer by radiation at temperatures exceeding 1000 oC and results in a low thermal conductivity. Given the advantages presented by this material, it is necessary to understand the formation mechanism of CA6 grains in order to better develop the potential applications of this material. CA6 can be fabricated using organic binders to consolidate the Al2O3-CaCO3 powder mixture and to provide green strength so that a green body can be formed and retains the desired shape before heating. However, these organic binders must be completely thermally decomposed so that they do not remain in the sintered body as carbon or ash. Moreover, the use of organic binders releases large volumes of gases such as carbon dioxide from the green body during heating. Therefore, an eco-friendly ceramic fabrication process has been developed that employs an inorganic binder (hydraulic alumina). The aim of the present work was to study the synthesis of porous calcium-hexaluminate ceramics using calcined alumina or hydraulic alumina combined with different sources of calcia (CaCO3 and Ca(OH)2) at different temperatures. The materials produced were characterized by X-ray diffraction, scanning electron microscopy, apparent porosity and mercury intrusion porosimetry. The materials produced by hydraulic alumina presented higher porosity and larger pores compared to those produced from calcined alumina

Recent studies involving the use of calcium aluminate cement (CAC) as a biomaterial are based on commercial products. Improvements can be attained by investigating the properties of their crystalline phases in order to better design the material's composition. Therefore, calcium aluminate phase samples immersed in simulated body fluid (SBF) solutions prepared according to Kokubo’s (KSBF) and Rigo’s (RSBF) methodology had their pH evaluated. The surfaces of these samples were analyzed by SEM, EDX and XRD techniques. The treatment with KSBF did not favor the precipitation of calcium phosphate phases on the surface of CAC phases. On the other hand, in RSBF solution, the pH value attained was higher than for the KSBF one and magnesium phosphate was identified on the surface of CA, C3A and C12A7 samples. Only for CA2, the optimal precipitation condition was attained in RSBF and a surface layer of the hydroxyapatite was detected. Based on its ability of stimulating hydroxyapatite deposition in SBF and other properties, CA2 can be eligible as the most suitable composition for biomedical purposes.

The aim of this study was to determine the best radiopaque additive to be incorporated to calcium aluminate cement (CAC) to promote radiopacity. Measurements of optical density were carried out on white MTA and CAC with and without additives such as: polymeric dispersant, plasticizer and various radiopacifiers. The effects of the radiopacifying addition on some properties of CAC were also evaluated. The radiopacity value for CAC-Bi2O3 (25%) was higher than the other radiopacifying agents tested. The addition of ZnO (25%) and 15%ZnO:10%Bi2O3 increased the compressive strength of CAC, whereas for Bi2O3 (25%) containing samples the strength was lower than for the CAC. The ZnO (25%) and 15%ZnO:10%Bi2O3 additions also reduced the apparent porosity. CAC does not have sufficient radiopacity to be distinguished from adjacent anatomic structures, such as dental tissues and bone. The addition of 15%ZnO:10%Bi2O3 can be suggested as the most suitable one to obtain the best compromise between good physical and mechanical properties and ideal radiopacity for clinical purposes.

O objetivo do presente estudo foi avaliar a progressão de cultura de células osteogênicas expostas a um novo cimento de aluminato de cálcio (CAC+) em comparação ao agregado de trióxido mineral (MTA). As células foram obtidas por digestão enzimática de calvária de ratos recém-nascidos, plaqueadas sobre lamínulas de vidro contendo em sua área central discos de CAC+ ou MTA e crescidas em condições osteogênicas por até 10 dias. Durante a cultura primária, observou-se o arredondamento das bordas das amostras de cimento apenas para MTA. Embora ambos os cimentos tenham permitido a adesão, o espraiamento e a proliferação celulares, as culturas crescidas em contato com CAC+ exibiram valores maiores de número total de células em 3 e 7 dias, e de conteúdo de proteína total e atividade de fosfatase alcalina em 10 dias. Os resultados indicam que a exposição ao CAC+ permite o desenvolvimento de uma proporção maior de células em estágios mais avançados da diferenciação osteoblástica, quando comparado ao MTA. Deve-se considerar em futuros estudos experimentais a utilização do CAC+ como um material alternativo ao MTA especialmente quando um dos objetivos do tratamento endodôntico é o de reparação dos tecidos mineralizados da região periapical.

The present study evaluated the progression of osteogenic cell cultures exposed to a novel calcium aluminate cement (CAC+) in comparison with the gold standard mineral trioxide aggregate (MTA). Cells were enzimatically isolated from newborn rat calvarial bone, plated on glass coverslips containing either CAC+ or a control MTA samples in the center, and grown under standard osteogenic conditions. Over the 10-day culture period, roundening of sample edges was clearly noticed only for MTA group. Although both cements supported osteogenic cell adhesion, spreading, and proliferation, CAC+-exposed cultures showed significantly higher values in terms of total cell number at days 3 and 7, and total protein content and alkaline phosphatase activity at day 10. The present in vitro results indicate that the exposure to CAC+ supports a higher differentiation of osteogenic cells compared with the ones exposed to MTA. Further experimental studies should consider CAC+ as a potential alternative to MTA when the repair of mineralized tissues is one of the desired outcomes in endodontic therapy.