The impact of zirconium oxide radiopacifier on the early hydration behaviour of white Portland cement

2013 ◽  
Vol 33 (1) ◽  
pp. 427-433 ◽  
Author(s):  
Nichola J. Coleman ◽  
Qiu Li
Keyword(s):  
Portland Cement ◽  
Zirconium Oxide ◽  
Early Hydration ◽  
Hydration Behaviour ◽  
The Impact ◽  
White Portland Cement

scholarly journals Impact of Bi2O3 and ZrO2 Radiopacifiers on the Early Hydration and C–S–H Gel Structure of White Portland Cement

2019 ◽  
Vol 10 (4) ◽  
pp. 46 ◽  
Author(s):  
Qiu Li ◽  
Nichola J. Coleman
Keyword(s):  
Portland Cement ◽  
Magic Angle Spinning ◽  
Cement Matrix ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Gel Structure ◽  
Early Hydration ◽  
Setting Times ◽  
The Impact ◽  
White Portland Cement

Bismuth oxide (monoclinic α-Bi2O3) and zirconium oxide (monoclinic ZrO2) are the most popular radiopacifiers in commercial Portland cement-based endodontic restoratives, yet their effects on the setting and hydration reactions are not fully understood. This study compares the impact of 20 wt.% of Bi2O3 or ZrO2 on the early hydration reactions and C–S–H gel structure of white Portland cement (WPC). Cement paste samples were hydrated at 37.5 °C prior to analysis by 29Si and 27Al magic angle spinning nuclear magnetic resonance spectroscopy at 3 h and 24 h, and transmission electron microscopy at 3 h. Initial and final setting times were determined using a Vicat apparatus and reaction kinetics were monitored by isothermal conduction calorimetry. Bi2O3 was found to prolong initial and final setting times and retard the degree of hydration by 32% at 24 h. Heat evolution during the acceleration and deceleration phases of the hydration process was reduced and the exotherm arising from renewed ettringite formation was delayed and diminished in the presence of Bi2O3. Conversely, ZrO2 had no significant impact on either setting time; although, it accelerated hydration by 23% within 24 h. Increases in the mean silicate chain length and the extent of aluminum substitution in the C–S–H gel were observed in the presence of both radiopacifying agents after 24 h relative to those of the unblended WPC. The Bi2O3 and ZrO2 particles remained intact within the cement matrix and neither bismuth nor zirconium was chemically incorporated in the hydration products.

scholarly journals The impact of lithium nitrate on the physical and mechanical properties of Portland cement)

2018 ◽  
Vol 163 ◽  
pp. 04002
Author(s):  
Justyna Zapała-Sławeta ◽  
Zdzisława Owsiak
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Portland Cement ◽  
Isothermal Calorimetry ◽  
Setting Time ◽  
Physical And Mechanical Properties ◽  
Strength Development ◽  
Lithium Nitrate ◽  
Early Hydration ◽  
The Impact

The effectiveness of lithium nitrate as a chemical additive which reduces the negative effects of alkali aggregate reaction was subject to research by scientists in many centres around the world. The literature data on the impact of lithium nitrate on the physical and mechanical properties of cements are rare. Without a precise definition of the impact of lithium nitrate on the cement properties, it is extremely hard to determine its real advantages in practical usage. In this paper, studies were undertaken to assess the impact of LiNO3 on the properties of pastes and mortars with Portland cement. The rate of hydration of the cement with lithium additive was examined by isothermal calorimetry, measurements of setting time and phase composition of cement pastes in the initial stages of hydration. The influence of the admixture on the compressive strength development of mortars after 2, 7 and 28 days of hardening was also researched. Results indicate that lithium nitrate accelerates the early hydration of Portland cement, affecting the precipitation of hydration products. The compressive strength of mortars with lithium admixture decrease after 28 days, although 2 an 7-day strength were greater than the control mortars.

scholarly journals Experimental Calcium Silicate-Based Cement with and without Zirconium Oxide Modulates Fibroblasts Viability

2015 ◽  
Vol 26 (6) ◽  
pp. 587-591 ◽  
Author(s):  
Camila Slompo ◽  
Camila Peres-Buzalaf ◽  
Kellen Cristina da Silva Gasque ◽  
Carla Andreotti Damante ◽  
Ronald Ordinola-Zapata ◽  
...  
Keyword(s):  
Portland Cement ◽  
Calcium Silicate ◽  
Zirconium Oxide ◽  
Mineral Trioxide Aggregate ◽  
The Other ◽  
Control Group ◽  
Mitochondrial Activity ◽  
Low Cytotoxicity ◽  
White Portland Cement ◽  
White Mineral

The aim of this study was to verify whether the use of zirconium oxide as a radiopacifier of an experimental calcium silicate-based cement (WPCZO) leads to cytotoxicity. Fibroblasts were treated with different concentrations (10 mg/mL, 1 mg/mL, and 0.1 mg/mL) of the cements diluted in Dulbecco's modified Eagle's medium (DMEM) for periods of 12, 24, and 48 h. Groups tested were white Portland cement (WPC), white Portland cement with zirconium oxide (WPCZO), and white mineral trioxide aggregate Angelus (MTA). Control group cells were not treated. The cytotoxicity was evaluated through mitochondrial-activity (MTT) and cell-density (crystal violet) assays. All cements showed low cytotoxicity. In general, at the concentration of 10 mg/mL there was an increase in viability of those groups treated with WPC and WPCZO when compared to the control group (p<0.05). A similar profile for the absorbance values was noted among the groups: 10 mg/mL presented an increase in viability compared to the control group. On the other hand, smaller concentrations presented a similar or lower viability compared to the control group, in general. A new dental material composed of calcium silicate-based cement with 20% zirconium oxide as the radiopacifier showed low cytotoxicity as a promising material to be exploited for root-end filling.

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