Dr. MH. Nekoofar

DDS, MSc, DoIBoE, PhD

Author: admin

  • 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

  • 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

  • Critical Requirements of Biomaterials Used in Challenging Endodontics and Vital Pulp Treatments

  • The Effect of Various Mixing and Placement Techniques on the Compressive Strength of Mineral Trioxide Aggregate: R113

  • Fractographic Analysis of ProTaper and Mtwo Systems: Breakage and Distortion in Severely Curved Roots of Molars

    Aim: This study evaluated the distortion and fracture mode of ProTaper and Mtwo rotary instruments following their use in severely curved root canals in extracted human teeth.
    Materials and Methods: A total of 30 mesial canals of mandibular molars were allocated into two groups that were balanced in terms of angle and radius of curvature. Canals were prepared by either ProTaper or Mtwo systems. Each set of instruments was changed after the third canal. Longitudinal and fractographic examinations of the instruments were carried out by scanning electron microscopy. Images were evaluated according to distortion and mode of fracture. Chi-square analysis and Fisher’s exact test were carried out at a significance level of P < 0.05.
    Results: No significant difference was found between fracture and distortion percentage of ProTaper and Mtwo rotary instruments (P > 0.05). Fractographic analysis revealed that all of the Mtwo instruments demonstrated torsional failure and all but one of the ProTaper instruments (S1) showed torsional failure.
    Conclusion: Fractographic examination of the fractured surface revealed shear fracture was the predominant mode of failure. Root canal curvature was an essential parameter influencing the susceptibility of instruments to fracture.

     Fractographic analysis of ProTaper and -december 2017.pdf

  • Effect of Acid Etching Procedures on the Compressive Strength of 4 Calcium Silicate–based Endodontic Cements

    The purpose of this study was to evaluate the effect of acid etching on the compressive strength of 4 calcium silicate–based cements. Methods: One gram of each corresponding powder of ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN), MTA Angelus (Angelus, Londrina, PR, Brazil), and CEM cement (BioniqueDent, Tehran, Iran) and a 0.33-g aliquot of liquid were placed in a plastic mixing capsule that was then mechanically mixed for 30 seconds at 4500 rpm in an amalgamator. For the preparation of Biodentine (Septodont, Saint Maur-des-Fosses, France), the liquid provided was added to the powder within the plastic capsule supplied by the manufacturer and then mechanically mixed for 30 seconds at 4500 rpm using the amalgamator. The resulting slurries were then placed incrementally into 40 cylindrical molds to give a total of 160 specimens that were incubated at 37C for a week. Twenty specimens of each material were then subjected to the acid etch procedure. The compressive strength of the samples was then calculated in megapascals using a universal testing machine. The results were then subjected to 2-way analysis of variance analysis of variance followed by the Tukey post hoc test.
    Results: The application of acid etch significantly reduced (P < .0001) the compressive strength of Angelus MTA and CEM cement; however, it did not reduce the compressive strength of ProRoot MTA or Biodentine. Regardless of the acid etch application, Biodentine showed significantly higher compressive strength values than the other materials (P < .0001), whereas CEM cement had the lowest compressive strength values. There was no significant differenc between CEM cement and MTA Angelus. The compressive strength of ProRoot MTA was significantly lower (P < .0001) than Biodentine but significantly higher (P <.0001) than MTA Angelus and CEM cement in both  the test and control groups. Conclusions: When the application of acid etchants is required, Biodentine and ProRoot MTA seem to be better options than MTA Angelus or CEM cement. (J Endod 2013;39:1646–1648)

     Effect of Acid Etching Procedures on the Compressive.pdf

  • Push-Out Bond Strength of Bioceramic Materials in a Synthetic Tissue Fluid

    Objective: This study compared the push-out bond strength of EndoSequence Root Repair Material (ERRM) and Bioaggregate (BA), new bioceramic materials, to that of mineral trioxide aggregate (MTA) after incubation in phosphate-buffered saline (PBS), a synthetic tissue fluid, for either 1 week or 2 months.
    Materials and Methods: One-hundred and twenty root sections were filled with ProRoot MTA, BA, or ERRM. Each tested material was then randomly divided into two subgroups (n = 20): root sections were immersed in PBS for 1 week or 2 months. The bond strengths were measured using a universal testing machine. Af-ter that, the failure modes were examined with stereomicroscopy and scanning electron microscopy (SEM). The push-out data and failure mode categories were analyzed by two-way ANOVA and chi-square tests, respectively.
    Results: The bond strength of ERRM was significantly higher than that of BA and MTA at both incubation periods. No significant difference was found between the bond strength of MTA and BA at either 1 week or 2 months. Increasing the incubation time to 2 months resulted in a significant increase in bond strength of all the materials. The failure mode was mainly mixed for MTA and BA, but cohe-sive for ERRM at both incubation periods.
    Conclusion: ERRM had significantly higher bond strength to root canal walls compared to MTA and BA. Increasing the incubation time significantly improved the bond strength and bioactive reaction products of all materials.

     Push-Out Bond Strength of Bioceramic Materials in a.pdf

  • Evaluation of the Effect of Blood Contamination on the Compressive Strength of MTA Modified with Hydration Accelerators

    This study was performed to evaluate the effect of blood contamination on the compressive strength (CS) of Root MTA (RMTA) modified with Calcium chloride (CaCl2) and Disodium hydrogen phosphate (Na2HPO4) as setting accelerators over time. Materials and Methods: A total of 110 cylindrical specimens of RMTA were divided into 6 experimental groups as follows: Group1, RMTA; Group 2, RMTA modified with CaCl2 (RMTA-C); Group 3, RMTA modified with Na2HPO4 (RMTA-N); Group 4, RMTA contaminated with blood; Group 5, RMTA-C contaminated with blood; Group 6, RMTA-N contaminated with blood. The CS of specimens in all groups was evaluated after 3 hr, 24 hr, and 1 wk. In the modified groups (groups 2, 3, 5, and 6) the CS of five specimens per group was also evaluated after 1 hr. Results: Blood contamination significantly reduced the CS of all materials at all time intervals (p < 0.05). After 3
    hr, the CS of specimens in the RMTA groups (with and without blood contamination) was significantly lower than those in the RMTA-C and RMTA-N groups (p < 0.05). The CS values were not significantly different at the other time intervals. In all groups, the CS of specimens significantly increased over time (p < 0.05). Conclusions: Blood contamination decreased the CS of both original and accelerated RMTA. (Restor Dent Endod 2013;38(3):128-133)

     Evaluation of the effect of blood contamination.pdf

  • The Effect of MTAD, an Endodontic Irrigant, on Fibroblast Attachment to Periodontally Affected Root Surfaces: A SEM Analysis

    Background: Root surface debridement (RSD) is necessary to create an environment suitable for reattachment of the periodontium. Root surface conditioning may aid the formation of a biocompatible surface suitable for cell reattachment. BioPure™ MTAD (mixture of Doxycycline, citric acid and a detergent) is an endodontic irrigant with antibacterial properties and the ability to remove smear layer. It was hypothesized that MTAD may be useful for root surface conditioning. The efficacy of MTAD as a conditioner was measured by examining fibroblast attachment to root surfaces. Materials and Methods: Thirty‑two specimens of human teeth with advanced periodontal disease were used. The surfaces were root planed until smooth. Half of the specimens were treated with 0.9% saline and the other samples with Biopure MTAD. As a negative control group, five further samples were left unscaled with surface calculus. Human gingival fibroblast cells HGF1‑PI1 were cultured and poured over the tooth specimens and incubated. After fixation, the samples were sputter‑coated with gold and examined with a SEM. The morphology and number of attached, fixed viable cells were examined. The data was analysed using the Mann‑Whitney‑U statistical test. Results: There was no significant difference between the numbers of attached cells in the experimental group treated with MTAD and the control group treated with saline. Little or no attached cells were seen in the negative control group. Conclusion: RSD created an environment suitable for cell growth and attachment in a laboratory setting. The use of  MTAD did not promote the attachment and growth of cells on the surface of human roots following RSD.

     The effect of MTAD, an endodontic.pdf