Dr. MH. Nekoofar

DDS, MSc, DoIBoE, PhD

Tag: PH

  • 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

  • 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

  • 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

  • pH of Pus Collected from Periapical Abscesses

    Aim: To determine the pH of pus collected from periapical abscesses. Methodology Forty patients (Male = 17/Female = 23) between the ages 17 and 37 years, each with a periapical abscess and with no relevant medical history, were recruited. All the participants had moderate- to-severe pain on percussion accompanied by localized or generalized swelling. At least 1 mL of pus was aspirated from each participant using a No 20 gauge needle. A pH meter was used to define the pH of the pus immediately following aspiration.
    Result: The mean pH of pus from the periapical abscesses of patients was 6.68 ± 0.324 with a range between 6.0 and 7.3. There was no statistically significant difference in pH by gender or age.
    Conclusion: The mean pH of pus from periapical abscesses was generally acidic, but some samples (two female and three male) were neutral and some samples (four female and one male) were alkaline.

     pH of pus collected from periapical abscesses.pdf