Dr. MH. Nekoofar

DDS, MSc, DoIBoE, PhD

Category: Publications

  • The Effect of Various Mixing Techniques on Some Physical Properties of Mineral Trioxide Aggregate

  • Microstructure and Chemical Analysis of Blood‐Contaminated Mineral Trioxide Aggregate

    Aim: To test the hypothesis that blood contamination has a detrimental effect on the chemical properties of Mineral trioxide aggregate (MTA). Methodology The effects ofwhole, freshhuman blood on the microstructure and elemental chemistry of MTA were evaluated using scanning electron microscopy and energy-dispersive X-ray analysis, respectively. The phase compositions of contaminated and uncontaminatedMTA were also analysed using X-ray diffraction analysis.
    Results: The hydration state of specimens partially mixed with blood were more complete than those mixed entirely with blood and less than those entirely mixed with water. Acicular crystals, characteristic of ettringite, were abundant in specimens mixed entirely with water and absent from specimens mixed partially or entirely with blood. Calcium hydroxide crystals were absent in specimens contaminated entirely with blood and the unhydrated MTA powder, but present in the other groups.
    Conclusion: Mixing MTA with blood resulted in the lack of formation of the crystalline calcium hydroxide in the early stage of the hydration process.

     Microstructure and chemical analysis of.pdf

  • The Effect of Contamination on Selected Physical and Chemical Characteristics of Mineral Trioxide Aggregate

    Aim: To evaluate the effect of various environmental (clinical) conditions on the physical and chemical characteristics of Mineral Trioxide Aggregate (MTA).
    Methodology: Initially preparation of specimens was standardised. Moreover, a novel mixing technique, trituration of encapsulated MTA, was developed. The effects of acid and blood contamination on various characteristics of MTA including compressive strength, surface microhardness, push-out bond strength and total porosity were then evaluated. Furthermore, by using X-ray diffraction analysis the hydration process of blood contaminated MTA was studied. In addition, the microstructure of contaminated MTA specimens was compared with control groups.
    Results: Methods of mixing and placing MTA significantly affected the hydration process and consequently the physical properties of the material. The lowest and greatest compressive strength, Vickers surface microhardness, and push-out strength values of MTA were found after exposure to pH levels of 4.4 and 7.4, respectively. In addition, scanning electron microscopy revealed a lack of needle-like crystals when the material was in contact with more acidic solutions. The hydration state of specimens partially mixed with blood was more complete than those mixed entirely with blood and less than specimens that were hydrated only with water.
    Conclusion: In experimental investigations, use of controlled mixing and placement techniques when using MTA is essential in order to standardise specimen preparation. Delaying the placement of the final coronal restoration i clinical situations when MTA is contaminated is recommended so that the material can acquire sufficient physical properties to withstand the acid-etch procedure and the condensation pressures that occur during the placement of a restoration and/or produced through indirect masticatory forces.
    The full text is available at:  http://orca.cf.ac.uk/14248/

  • SEM Analysis of MTAD Efficacy for Smear Layer Removal from Periodontally Affected Root Surfaces

    Objective: Biopure® MTAD (Dentsply Tulsa Dental, USA) has been developed as a final irrigant following root canal shaping to remove intracanal smear layer. Many of the unique properties of MTAD potentially transfer to the conditioning process of tooth roots during periodontal therapy. The aim of this ex vivo study was to evaluate the effect of MTAD on the removal of smear layer from root surfaces. Materials and Methods: Thirty two longitudinally sectioned specimens from 16 freshly extracted teeth diagnosed with advanced periodontal disease were divided into four groups. In group 1 and 2, the root surfaces were scaled using Gracey curettes. In group 3 and 4, 0.5 mm of the root surface was removed using a fissure bur. The specimens in group 1 and 3 were then irrigated by normal saline. The specimens in groups 2 and 4 were irrigated with Biopure MTAD. All specimens were prepared for SEM and scored according to the presence of smear layer.
    Results: MTAD significantly increased (P=0.001) the smear layer removal in both groups 2 and 4 compared to the associated control groups, in which only saline was used. Conclusion: MTAD increased the removal of the smear layer from periodontally affected root surfaces. Use of MTAD as a periodontal conditioner may be suggested.

     SEM Analysis of MTAD Efficacy for Smear Layer Removal.pdf

  • An Evaluation of the Effect of Blood and Human Serum on the Surface Microhardness and Surface Microstructure of Mineral Trioxide Aggregate

    Aim: Short-term and long-term evaluation of the effect of whole human blood or serum contamination on the surface microhardness value and microstructure of white and grey mineral trioxide aggregate (MTA). Methodology Three groups of 10 samples for each type of MTA were prepared. The first group was mixed with and exposed to fresh whole human blood. The second and third groups were mixed with distilled water and exposed to fresh whole human blood or human serum, respectively. The control group samples were mixed with and exposed to distilled water. During preparation, 1 g of MTA was triturated with 0.33 g of the selected liquid using an amalgamator and placed inside borosilicate cylindrical moulds. The samples were treated with ultrasonic energy. Vickers surface microhardness values were compared after 4 and 180 days. Scanning electron microscopy (SEM) analysis was performed after 4 days.
    Results: White MTA had a greater microhardness value than grey MTA in all groups. There was a significant difference between the control and the experimental groups (P < 0.00001). There was no significant difference between the microhardness values obtained after 4 and 180 days, apart from grey MTA mixed with blood or exposed to serum (P < 0.00001). SEM analysis showed the contaminated samples were devoid of acicular crystals that were prominent in the control groups.
    Conclusion: Blood contamination had a detrimental effect on the surface microhardness of MTA in the short and long term. If blood or serum contamination is unavoidable under clinical conditions, it might be preferable to use white MTA.

     An evaluation of the effect of blood and human.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

  • The Sealing Ability of Resilon and Gutta-Parcha Following Different Smear Layer Removal Methods: An Ex Vivo Study

    Objective. The objective of this study was to compare the ex-vivo sealing ability of Resilon/new Epiphany (SE) sealer to that of gutta-percha/AH-Plus following smear layer removal with EDTA or MTAD. Study design. One hundred extracted single-rooted human teeth were divided into 4 experimental groups and 2 positive and negative control groups. EDTA was used in groups 1 and 2. In groups 3 and 4 MTAD was used. The root canals were then obturated with gutta-percha/AH-Plus in groups 1 and 3 and Resilon/Epiphany (SE) in groups 2 and 4. After sterilization, the samples were coronally exposed to human saliva and monitored every 24 hours for 60 days.
    Results: In groups 1, 2, 3, and 4, 45%, 65%, 90%, and 65% of specimens leaked within 60 days, respectively. There were statistically significant differences between group 1 and 3 (P  .05).
    Conclusions:  Resilon/Epiphany (SE) system is as effective as gutta-percha/AH-Plus in preventing saliva leakage. MTAD did not adversely affect the sealing ability of Resilon/Epiphany (SE).

     The sealing ability of resilon and gutta-parcha following.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

  • The Effect of Various Mixing Techniques on the Surface Microhardness of Mineral Trioxide Aggregate

    Aim To evaluate the influence of various mixing procedures including ultrasonic vibration, trituration of customized encapsulated mineral trioxide aggregate (MTA) and condensation on the Vickers surface microhardness of MTA.
    Methodology ProRoot MTA Original, ProRoot MTA (white), MTA-Angelus (grey) and MTA White Angelus (white) were prepared using several mixing techniques including ultrasonic vibration, trituration of customized encapsulated MTA and conventional condensation. Twelve experimental groups (four materials: three techniques) were evaluated, each with 35 samples. All samples were incubated after preparation and subjected to Vickers surface microhardness testing after 4 and 28 days. Data was were subjected to a two-way anova.
    Result: At 28 days, the surface microhardness value was significantly greater for all experimental groups compared to 4 days after mixing (P < 0.00001). The application of ultrasonic energy to MTA produced significantly higher surface microhardness values compared to the other mixing techniques at both 4 and 28 days (P < 0.0001). However, no significant difference existed between condensation and trituration techniques at both time intervals. Regardless of the mixing technique employed, a significant difference (P < 0.0001) was observed in surface microhardness value between all types of MTA apart from between Angelus grey and ProRoot white at both 4 and 28 days, both of which produced the highest values.
    Conclusion: Compared to trituration and condensation techniques, the application of ultrasonic energy to MTA produced a significantly higher surface microhardness value at both 4 and 28 days. Irrespective of mixing technique, ProRoot white and Angelus grey had the highest surface microhardness values. Trituration of encapsulated, premeasured MTA and water provides a standardiszed method of mixing that produces MTA slurries with more controllable handling characteristics.

     The effect of various mixing techniques on the.pdf

  • Effect of Acid‐Etching Procedure on Selected Physical Properties of Mineral Trioxide Aggregate

    Aim: To evaluate the effect of acid-etch procedures on the compressive strength and surface microhardness of tooth-coloured mineral trioxide aggregate (MTA). Methodology White ProRoot MTA (Dentsply Tulsa Dental) was mixed and packed into cylindrical tubes of 4 mm in diameter and 6 mm in height. Three groups, each of 15 specimens were subjected to an acid-etch procedure either 4, 24 or 96 h after mixing. The compressive strength was measured and compared with unetched control groups. Differences between groups were analysed using the Kruskall–Wallis test. A further batch of cylindrical specimens of 6 mm in diameter and 12 mm in height were prepared for testing surface microhardness. Three groups of 15 specimens were subjected to the acid-etch procedure at either 4, 24 or 96 h following mixing. Data were subjected to one-way anova. Changes in the surface microstructure before and  after the acid-etch procedures were analysed using a scanning electron microscope (SEM).
    Results: There was a general trend for the compressive strength and surface microhardness of specimens to increase with time. In terms of compressive strength, the increase was significant between 4 h and the other time periods for both experimental and control groups (P < 0.0001); however, there was no significant difference between 24 and 96 h. The increase in surface microhardness was significant between 4, 24 and 96 h (P < 0.0001). In addition, there was a significant difference between experimental and control groups at all time periods (P < 0.0001). SEM examination revealed morphological differences between the intact and the etched MTA surfaces.
    Conclusions : Acid-etch procedures affected the compressive strength and surface microhardness of ProRoot MTA. This indicates that it may be better to postpone restorative procedures for at least 96 h after mixing MTA. Etching created surface changes that might have the potential to enhance bonding of resinous materials.

     Effect of acid-etching procedure on selected.pdf