Dr. MH. Nekoofar

DDS, MSc, DoIBoE, PhD

Tag: MTA

  • The Effect of Operator-Induced Variability on the Physical Properties of ProRoot MTA

    Abstract

    Aims: The aim of this study was to compare the influence of operators on the microhardness and compressive strength of mineral trioxide aggregate (MTA). Materials and Methods: Forty dental specialists were asked to prepare a series of MTA samples. The tested material was ProRoot MTA (DentsplyMaillefer, Switzerland). Each participant prepared one sample to a consistency they considered acceptable for use in practice(improvised group) and another one according to the manufacturer’s recommended water‑to‑powder(WP) ratio(pre‑weighed group). The samples were incubated at 37°C and 95% humidity for 4days. Parameters evaluated in this study were microhardness and compressive strength. Results: Operators mixed MTA samples with varying WP ratios. However, there was no significant difference between the microhardness and compressive strength values of MTA samples between the improvised, the pre‑weighed and the control groups. MTA was mixed in a thicker consistency than the manufacturers recommended ratio (0.33) by 62.5% of the operators. Conclusion: According to the results of this study, even though the WP ratios that were utilized in the clinical setting vary, microhardness and compressive strength values of MTA was not significantly affected.

    Keywords: Compressive Strength, Microhardness, MTA, Surface Microhardness, Water-to-Powder Ratio

  • Microstructure and Chemical Analysis of Four Calcium Silicate-Based Cements in Different Environmental Conditions

    Abstract

    Objective The objective of this study was to analyze the microstructure and crystalline structures of ProRoot MTA, Biodentine, CEM Cement, and Retro MTA when exposed to phosphate-buffered saline, butyric acid, and blood.

    Methods and materials Mixed samples of ProRoot MTA, Biodentine, CEM Cement, and Retro MTA were exposed to either phosphate-buffered saline, butyric acid, or blood. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopic (EDX) evaluations were conducted of specimens. X-ray diffraction (XRD) analysis was also performed for both hydrated and powder forms of evaluated calcium silicate cements.

    Results The peak of tricalcium silicate and dicalcium silicate detected in all hydrated cements was smaller than that seen in their unhydrated powders. The peak of calcium hydroxide (Ca(OH)2) in blood- and acid-exposed ProRoot MTA, CEM Cement, and Retro MTA specimens were smaller than that of specimens exposed to PBS. The peak of Ca(OH)2 seen in Biodentine™ specimens exposed to blood was similar to that of PBS-exposed specimens. On the other hand, those exposed to acid exhibited smaller peaks of Ca(OH)2.

    Conclusion Exposure to blood or acidic pH decreased Ca(OH)2 crystalline formation in ProRoot MTA, CEM Cement and Retro MTA. However, a decrease in Ca(OH)2 was only seen when Biodentine™ exposed to acid.

    Clinical relevance The formation of Ca(OH)2 which influences the biological properties of calcium silicate cements was impaired by blood and acid exposures in ProRoot MTA, CEM Cement, and Retro MTA; however, in the case of Biodentine, only exposure to acid had this detrimental effect.

    Keywords: Biodentine, Calcium Silicate Cement, CEM Cement, EDX, MTA, SEM, XRD.

  • Does the mixing and placement regime affect the pH of Mineral Trioxide Aggregate?

    Abstract

    Aim: The objective of this study was to measure in a laboratory setting the pH of tooth coloured ProRoot MTA and MTA Angelus following various mixing and placement techniques, including mechanical mixing, manual mixing and indirect ultrasonic activation.

    Materials and Method: Tooth coloured ProRoot MTA and White MTA Angelus were used. One gram of each powder was mixed with a 0.34 g of distilled water that were allocated to eight experimental groups, each containing three specimens. Four groups were prepared by mechanical mixing of capsules for 30 s at 4500 rpm the other four were mixed manually. Half of the specimens in each group were placed in moulds using indirect ultrasonic activation. pH values were recorded directly from within the freshly mixed material and were analyzed using one-way ANOVA at a 0.05 level of significance.

    Results: No significant difference in pH was found between the mixing and placement techniques or the materials tested. The highest pH value recorded was in the ProRoot group that was mixed manually and placed ultrasonically (11.64). The Angelus group, which was mixed manually without an ultra-sonic agitation, had the lowest pH values (10.42).

    Conclusion: Mechanical mixing and ultrasonication confer-red no significant disadvantage in terms of the initial pH of the material. Since mechanical agitation of encapsulated cements provides more consistent mixes, it might be possible to use this technique combined with ultrasonic agitation as an alternative to manual mixing, both in clinical and in laboratory conditions, in order to achieve standardization of the material so as to enhance its properties.

    Keywords: PH, Placement, MTA, Mixing.

     Does the mixing and placement regime affect the pH of Mineral Trioxide Aggregate.pdf

  • X-Ray Diffraction Analysis of MTA Mixed and Placed with Various Techniques

    Abstract

    Objectives The aim of this study was to evaluate the effect of various mixing techniques as well as the effect of ultrasonic placement on hydration of mineral trioxide aggregate (MTA) using X-ray diffraction (XRD) analysis.

    Materials and Methods One gram of ProRoot MTA and MTA Angelus powder was mixed with a 0.34-g of distilled water. Specimens were mixed either by mechanical mixing of capsules for 30 s at 4500 rpm or by manual mixing followed by application of a compaction pressure of 3.22 MPa for 1 min. The mixtures were transferred into the XRD sample holder with minimum pressure. Indirect ultrasonic activation was applied to half of the specimens. All specimens were incubated at 37 °C and 100% humidity for 4 days. Samples were analyzed by XRD. Phase identification was accomplished by use of search-match software utilizing International Centre for Diffraction Data (ICDD).

    Results All specimens comprised tricalcium silicate, calcium carbonate, and bismuth oxide. A calcium hydroxide phase was formed in all ProRoot specimens whereas among MTA Angelus groups, it was found only in the sample mixed mechanically and placed by ultrasonication.

    Conclusions Mechanical mixing followed by ultrasonication did not confer a significant disadvantage in terms of hydration characteristics of MTA.

    Clinical Relevance Clinicians vary in the way they mix and place MTA. These variations might affect their physical characteristics and clinical performance. For ProRoot MTA, the mixing and placement methods did not affect its rheological properties, whereas for MTA Angelus, mechanical mixing combined with ultrasonic placement enhanced the calcium hydroxide phase formation.

    Keywords: Calcium Hydroxide, MTA, Mechanical Mixing, Ultrasonic Agitation, X-ray diffraction Analysis, XRD.

     X-Ray Diffraction Analysis of MTA Mixed and Placed with Various Techniques.pdf

  • Acid and Microhardness of Mineral Trioxide Aggregate and Mineral Trioxide Aggregate–like Materials

    The aim of this study was to compare the surface microhardness of BioAggregate, ProRoot MTA, and CEMCement when exposed to an acidic environment or phosphate-buffered saline (PBS) as a synthetic tissue fluid. Methods: Ninety cylindrical molds made of polymethyl methacrylate with an internal diameter of 6 mm and height of 4 mm (according to ASTM E384 standard for microhardness tests) were fabricated and filled with BioAggregate (n = 30), tooth-colored ProRoot MTA (n = 30), or CEM Cement (n = 30). Each group was then divided into 3 subgroups of 10 specimens consisting of those exposed to distilled water, exposed to PBS (pH = 7.4), or exposed to butyric acid (pH = 5.4). After 1 week the Vickers surface microhardness test was performed. Statistical analysis included 2-way analysis of variance, followed by post hoc Dunnett T3 in cases with lack of homoscedasticity and Tukey honestly significant difference in cases with homoscedasticity. 
    Results: The indentations obtained from the CEM Cement specimens exposed to an acidic pH were not readable because of incomplete setting. There was a significant difference between the microhardness of the materials regardless of the environmental conditions (P < .001). In all the environmental conditions, MTA had significantly higher and CEM Cement had significantly lower microhardness values (P < .001). All experimental cements had significantly higher microhardness values when exposed to PBS (P < .001) and had significantly lower microhardness values when exposed to butyric acid (P < .001). Conclusions: The surface microhardness of BioAggregate, ProRoot MTA, and CEM Cement was reduced significantly by exposure to butyric acid and increased significantly by exposure to PBS. In all environmental conditions, MTA had significantly higher microhardness values. (J Endod 2014;40:432–435)

     Acid and Microhardness of Mineral Trioxide Aggregate.pdf

  • Effect of Various Mixing and Placement Techniques on the Flexural Strength and Porosity of Mineral Trioxide Aggregate

    The aim of this study was to evaluate the effect of mechanical and manual mixing as well as the effect of ultrasonic agitation during placement on the flexural strength and porosity of mineral trioxide aggregate (MTA). Methods White ProRoot MTA and white MTA Angelus were used. One gram of each powder was mixed with a 0.34-g aliquot of distilled water. Specimens were mixed either by mechanical mixing of capsules for 30 seconds at 4500 rpm or by a saturation technique and application of a condensation pressure of 3.22 MPa for 1 minute. The mixed slurries of all materials were loaded into 2  2  25 mm molds for testing flexural strength and 3  4 mm molds for evaluation of porosity. Half of the specimens were placed in the stainless steel molds by using indirect ultrasonic activation. All specimens were incubated for 4 days. Micro–computed tomography was used to determine the porosity of each specimen, and a 3-point bending test was used to evaluate flexural strength. Tukey honestly significant difference and independent t tests were carried out to compare the means at a significance level of P < .05. Results: Irrespective of mixing and placement techniques applied, the flexural strength values of ProRoot MTA were significantly greater than those of MTA Angelus (P < .05). A medium negative correlation was found between flexural strength values and total porosity percentage. Conclusions: Although mechanical mixing of encapsulated cements was quicker and provided more consistent mixes, this technique along with ultrasonic agitation was not associated with a significant advantage in terms of flexural strength and total porosity over manual mixing. (J Endod 2014;40:441–445)

     Effect of Various Mixing and Placement Techniques on the.pdf

  • The Effect of Blood Contamination on the Compressive Strength and Surface Microstructure of Mineral Trioxide Aggregate

    Aim: To investigate the effects of whole, fresh human blood contamination on compressive strength and surface microstructure of grey and tooth-coloured mineral trioxide aggregate (MTA). Methodology The materials investigated were grey ProRoot MTA Original (Dentsply Tulsa Dental, Johnson City, TN, USA) and tooth-coloured ProRoot MTA (Dentsply Tulsa Dental). Three groups of 10 custommade cylindrical moulds (internal dimensions 6 ± 0.1 mm length and 4 ± 0.1 mm diameter) were filled with tooth-coloured MTA. In the control group, MTA was mixed with water and exposed to water. In the second group, MTA was mixed with water and exposed to whole, fresh human blood. In the third group, MTA was mixed with and exposed to whole, fresh human blood. These three groups were then duplicated using grey MTA, creating a total of 60 samples. A predetermined amount of MTA and appropriate liquid were
    triturated in a plastic mixing capsule then subjected to ultrasonic energy after placement in the moulds. After 4 days of incubation, specimens were subjected to compressive strength testing. The surface microstructure of one extra specimen in each group was examined using scanning electron microscopy. Data were subjected to a two-way anova.
    Results: Regardless of MTA type, the mean compressive strength values of both experimental groups, which were in contact with blood, were significantly less than that of the control groups (P < 0.0001). In experimental groups in which MTA was mixed with water and exposed to blood, there was a significant difference (P < 0.0001) in compressive strength between tooth-coloured MTA (30.37 ± 10.16 MPa) and grey MTA (13.92 ± 3.80 MPa).
    Conclusion: When blood becomes incorporated into MTA, its compressive strength is reduced. In clinical situations in which blood becomes mixed with MTA, its physical properties are likely to be compromised.

     The effect of blood contamination on the.pdf

  • Effect of Acidic Environment on the Push-out Bond Strength of Mineral Trioxide Aggregate

    Reduced surface microhardness and decreased sealing ability have been shown after the placement of mineral trioxide aggregate (MTA) in an acidic environment. In this study, the effect of an acidic environment on the push-out strength of MTA was evaluated.
    Methods: Eighty root dentin slices from freshly extracted single-rooted human teeth were sectioned and their lumen instrumented to achieve a diameter of 1.3 mm. One gram of tooth-colored ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN) was mixed with 0.33 g of distilled water and introduced into the canals of the root-dentin slices and treated with ultrasonic energy. The specimens were then randomly divided into four groups (n = 20) and wrapped in pieces of gauze soaked in phosphate buffer saline solution (pH = 7.4) and butyric acid buffered at pH values of 4.4, 5.4, or 6.4, respectively. They were then incubated for 4 days at 37C. The push-out bond strengths were then measured using a universal testing machine. The slices were examined under a light microscope at 40 magnification to determine the nature of the bond failure. The data were analyzed using one-way analysis of variance and the Tamhane post hoc test. Results: The greatest mean push-out bond strength (7.28  2.28 MPa) was observed after exposure to a pH value of 7.4. The values decreased to 2.47  0.61 MPa after exposure to a pH value of 4.4. There were significant differences between the groups (p < 0.001). Inspection of the samples revealed the bond failure to be predominantly adhesive.
    Conclusion: The force needed for displacement of MTA was significantly lower in samples stored at lower pH values. (J Endod 2010;36:871–874)

     Effect of Acidic Environment on the Push-out Bond Strength.pdf