Dr. MH. Nekoofar

DDS, MSc, DoIBoE, PhD

Tag: scanning electron microscopy

  • Marginal Adaptation of New Bioceramic Materials and Mineral Trioxide Aggregate: A Scanning Electron Microscopy Study

    This study aimed to compare the marginal adaptation of new bioceramic materials, Endosequence Root Repair Material (ERRM putty and ERRM paste), to that of mineral trioxide aggregate (MTA) as root end filling materials. 

    Materials and Methods : thirty six extracted human single-rooted teeth were prepared and obturated with gutta-percha and AH-26 sealer. the roots were resected 3 mm from the apex. Root-end cavities were then prepared with an ultrasonic retro-tip. the specimens were divided into three groups (n=12) and filled with MTA, ERRM putty or ERRM paste. Epoxy resin replicas from resected root-end surfaces and longitudinally sectioned roots were fabricated. The gaps at the material/dentin interface were measured using scanning electron microscope (SEM). Transversal, longitudinal and overall gap sized were measured for each specimen. The data were analyzed using the Kruskall-Wallis test. 
    Results: in transversal sections, no significant difference was found between MTA, ERRM putty and ERRM paste (P=0.31). However, in longitudinal sections, larger gaps were evident between the ERRM paste and dentinal walls compared to MTA and ERRM putty (P=0.002 and P=0.033, respectively). Considering the overall gap size values, the difference between three tested materials was not statistically significant (p=0.17). 
    Conculsion: within the limits of this study, the marginal adaptation of ERRM paste and putty was comparable to that of MTA. However, ERRM putty might be more suitable for filling the root-end cavities because of its superior adaption compared to ERRM paste in longitudinal sections 

     Marginal Adaptation of New Bioceramic Materials and Mineral Trioxide Aggregate A Scanning Electron Microscopy Study.pdf

  • 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

  • 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 pH on Surface Hardness and Microstructure of Mineral Trioxide Aggregate

    Aim: To evaluate the surface microhardness of mineral trioxide aggregate (MTA) specimens following exposure of their surface to a range of acidic environments during hydration. In addition, the morphological microstructure features of samples were studied by scanning electron microscopy (SEM). Methodology White ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed and packed into cylindrical polycarbonate tubes. Four groups, each of 10 specimens, were formed using a pressure of 3.22 MPa and exposed to pH 4.4, 5.4, 6.4 and 7.4, respectively, for 4 days. Vickers microhardness of the surface of each specimen was measured after exposure. Four groups of two specimens were prepared and treated in the same way prior to qualitative examination by SEM. Data were subjected to one-way anova and post hoc Tukey’s test.

    Result: The greatest mean surface hardness values (53.19 ± 4.124) were observed following exposure to pH 7.4 with the values decreasing to 14.34 ± 6.477 following exposure to pH 4.4. The difference between these values at the 95% CI (33.39–44.30) was statistically significant (P < 0.0001). There were no distinct morphological differences between groups in terms of the internal microstructure. However, a trend was observed that the more acidic the solution, the more extensive the porosity of the specimens.
    Conclusion: Under the conditions of this study, surface hardness of MTA was impaired in an acidic environment.

     The effect of pH on surface hardness and.pdf

  • The Effect of Condensation Pressure on Selected Physical Properties of Mineral Trioxide Aggregate

    Aim: To examine the effect of condensation pressure on surface hardness, microstructure and compressive strength of mineral trioxide aggregate (MTA). Methodology White ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed and packed into cylindrical polycarbonate tubes. Six groups each of 10 specimens were subjected to pressures of 0.06, 0.44, 1.68, 3.22, 4.46 and 8.88 MPa respectively. The surface hardness of each specimen was measured using Vickers microhardness. Cylindrical specimens of 4 mm in diameter and 6 mmin height were prepared in polycarbonate cylindrical moulds for testing the compressive strength. Five groups of 10 specimens were prepared using pressures of 0.06, 0.44, 1.68, 3.22 or 4.46 MPa. Data were subjected to one-way anova. The microstructure was analysed using a scanning electron microscope (SEM) after sectioning specimens with a scalpel.

     The effect of condensation pressure on selected.pdf