Mohammad Ali Saghiri

Effect of pH on Sealing Ability of White Mineral Trioxide Aggregate as a Root-end Filling Material

The aim of the present study was to evaluate microleakage of mineral trioxide aggregate (MTA) used as a root-end filling material after its exposure to a range of acidic environments during hydration. Seventy single-rooted teeth were divided into 4 experimental and 2 control groups. All the teeth were instrumented, and their apices were resected. Root-end cavities were filled with white MTA in the experimental groups. In the control groups root-end cavities were not filled. Root-end fillings were exposed to acidic environments with pH values of 4.4, 5.4, 6.4, or 7.4 for 3 days in the experimental groups. Microleakage was evaluated by using bovine serum albumin. The evaluation was conducted at 24-hour intervals for 80 days. Data were analyzed by using one-way analysis of variance and a post hoc Tukey test. The earliest bovine serum albumin microleakage was observed in a pH value of 4.4 followed by pH values of 5.4, 6.4, and 7.4, respectively. There was a significantly longer time necessary for leakage to occur in samples stored in higher pH values (P < .000).

Push-out bond strength of mineral trioxide aggregate in the presence of alkaline pH.

INTRODUCTION The aim of this study was to evaluate the effect of a range of alkaline pH values on the push-out strength of white mineral trioxide aggregate (WMTA). METHODS The standardized lumens of root slices prepared from extracted single-rooted human teeth were filled with white ProRoot MTA. The specimens were then randomly divided into 4 groups (n = 20) and wrapped in pieces of gauze soaked in synthetic tissue fluid (STF) (pH, 7.4) and STF buffered in potassium hydroxide at pH values of 8.4, 9.4, or 10.4. The samples were incubated for 3 days at 37 °C. The push-out bond strengths were then measured by using a universal testing machine. Failure modes after the push-out test were examined under a light microscope at ×40 magnification. The data were analyzed by using one-way analysis of variance and Tukey post hoc tests. RESULTS The greatest (9.46 ± 0.63 MPa) and lowest (5.68 ± 0.83 MPa) mean push-out bond strengths were observed after exposure to pH values of 8.4 and 10.4, respectively. There were significant differences between the groups (P = .001). The bond failure was adhesive for all experimental groups. CONCLUSIONS Push-out bond strength of WMTA could be influenced by different alkaline pH values.

Influence of White versus Gray Mineral Trioxide Aggregate on Inflammatory Cells

The aim of this investigation was to compare the quantity of inflammatory cells in response to white and gray mineral trioxide aggregate (MTA) in subcutaneous connective tissue of rats. Fifty Wistar rats were used in this study. Polyethylene tubes were filled with gray or white MTA and empty ones serving as the control group were implanted into subcutaneous tissue and harvested after 7-, 15-, 30-, 60-, and 90-day intervals. Sections of 5 microm were stained with hematoxylin and eosin and observed under a light microscope. Inflammatory reactions were categorized as 0, none (without inflammatory cells); 1, mild (inflammatory cells < or = 25); 2, moderate (25-125 inflammatory cells); and 3, severe (more than 125 inflammatory cells). Statistical analysis was performed with the Kruskal-Wallis test. Both kinds of MTA provoked severe inflammatory reaction after 7 days, which significantly differed from control group (p < 0.05). However, there were no significant differences at any time period beyond 15 days (p > 0.05).

Nanomodification of mineral trioxide aggregate for enhanced physiochemical properties

AIM To analyse the physicochemical properties of a Nano white mineral trioxide aggregate (NWMTA) and compare it with white mineral trioxide aggregate (WMTA). METHODOLOGY White mineral trioxide aggregate and NWMTA were prepared and mixed according to the manufacturers instructions. Surface area of powder before hydration, setting time, X-ray diffraction and microhardness at pH values of 4.4 and 7.4 were evaluated by Brunauer-Emmett-Teller, ISO Specification no.6876, Vickers microhardness, and energy-dispersive X-ray spectroscopy equipped with X-ray colour (dot) map for both cements. anova and Mann-Whitney were used for statistical analysis at a significance level of 0.5. RESULTS The mean ± SD of surface area and setting time were 1.8 ± 0.2 m(2) g(-1) and 43 ± 2 min for WMTA and 7.8 ± 1.2 m(2) g(-1) and 6 ± 1 min for NWMTA, respectively. Mean ± SD of Microhardness were 16 ± 2, 51 ± 1, 69 ± 1 and 81 ± 2 for WMTA at pH values of 4.4 and 7.4 and for NWMTA correspondingly. Numbers of open porosity over the surface were 88 ± 24 and 44 ± 13 for WMTA and NWMTA, respectively. Statistical tests revealed significant differences between the groups (P < 0.001) in surface area, setting time and surface hardness for both cements. Uniform distribution of strontium was only observed in NWMTA. However, other compounds were not significantly different. CONCLUSION Increasing surface area of powder can reduce setting time and increase microhardness even at lower pH values after hydration.

Scanning Electron Micrograph and Surface Hardness of Mineral Trioxide Aggregate in the Presence of Alkaline pH

INTRODUCTION The aim of this study was to evaluate morphologic microstructure and surface hardness of white mineral trioxide aggregate (WMTA) after exposure to a range of alkaline environments during hydration. METHODS WMTA was mixed and packed into 60 glass tubes. Four groups, each containing 15 tubes, were exposed to pH values of 7.4, 8.4, 9.4, and 10.4, respectively, for 3 days. In 12 tubes in each group, Vickers surface hardness was measured after exposure to alkaline environments. Data were subjected to one-way analysis of variance and a post hoc Tukey test. Three specimens in each group were prepared to be evaluated under a scanning electron microscope using scattered electron (SE) and backscattered electron (BSE) detectors. RESULTS The mean surface hardness values +/- standard deviation after exposure to pH values of 7.4, 8.4, 9.4, and 10.4 were 58.28 +/- 8.21, 68.84 +/- 7.19, 67.32 +/- 7.22, and 59.22 +/- 9.14, respectively. The difference between these values was statistically significant (p = 0.000). There were statistically significant differences between pH values of 8.4 and 9.4 and pH values of 7.4 and 10.4 (p > 0.05). The SE detector revealed needle-shaped crystals at pH values of 7.4 and 8.4 and an amorphous microstructure at pH values of 9.4 and 10.4 on WMTA surface. The BSE detector showed more unhydrated structure and pores at pH values of 7.4 and 10.4 compared with pH values of 8.4 and 9.4. CONCLUSIONS Surface hardness can be influenced by different alkaline pH values. The BSE detector can reveal more microstructure details of WMTA in conjunction with the SE detector. More porosity and unhydrated structure are observed in WMTA exposed to pH values of 7.4 and 10.4.

Functional role of inorganic trace elements in angiogenesis—Part II: Cr, Si, Zn, Cu, and S

Trace elements play critical roles in angiogenesis events. The effects of nitrogen, iron, selenium, phosphorus, gold, and calcium were discussed in part I. In part II, we evaluated the effect of chromium, silicon, zinc, copper, and sulfur on different aspects of angiogenesis, with critical roles in healing and regeneration processes, and undeniable roles in tumor growth and cancer therapy. This review is the second of series that serves as an overview of the role of inorganic elements in regulation of angiogenesis and vascular function. The methods of exposure, structure, mechanism, and potential activity of these trace elements are briefly discussed. An electronic search was performed on the role of these trace elements in angiogenesis from January 2005 to April 2014. The recent aspects of the relationship between five different trace elements and their role in regulation of angiogenesis, and homeostasis of pro- and anti-angiogenic factors were assessed. Many studies have investigated the effects and importance of these elements in angiogenesis events. Both stimulatory and inhibitory effects on angiogenesis are observed for the evaluated elements. Chromium can promote angiogenesis in pathological manners. Silicon as silica nanoparticles is anti-angiogenic, while in calcium silicate extracts and bioactive silicate glasses promote angiogenesis. Zinc is an anti-angiogenic agent acting on important genes and growth factors. Copper and sulfur compositions have pro-angiogenic functions by activating pro-angiogenic growth factors and promoting endothelial cells migration, growth, and tube formation. Thus, utilization of these elements may provide a unique opportunity to modulate angiogenesis under various setting.

Effect of White Mineral Trioxide Aggregate Mixed With Disodium Hydrogen Phosphate on Inflammatory Cells

INTRODUCTION The aim of this study was subjective evaluation of inflammatory cells subsequent to subcutaneous implantation of white mineral trioxide aggregate (WMTA) mixed with disodium hydrogen phosphate (Na(2)HPO(4)) in rats. METHODS Forty Wistar rats were used in this study. Polyethylene tubes filled with WMTA mixed with Na(2)HPO(4) and WMTA alone and also empty tubes serving as control were implanted into subcutaneous tissue and harvested after 7, 15, 30, and 90 days. Histologic sections were stained with hematoxylin-eosin and observed under a light microscope. Inflammatory reactions were categorized as 0 or none (without inflammatory cells), 1 or mild (inflammatory cells < 25), 2 or moderate (25-125 inflammatory cells), and 3 or severe (more than 125 inflammatory cells). Statistical analyses were performed with the Kruskal-Wallis and Mann-Whitney tests. RESULTS WMTA alone provoked a moderate inflammatory reaction after 7 and 15 days, which significantly differed from WMTA mixed with Na(2)HPO(4) and the control group, which provoked a mild inflammatory reaction (P < .05). However, there were no significant differences at any period beyond 30 days. CONCLUSIONS This study indicates that adding Na(2)HPO(4) to WMTA creates a more biocompatible material than WMTA alone.

Role of Angiogenesis in Endodontics: Contributions of Stem Cells and Proangiogenic and Antiangiogenic Factors to Dental Pulp Regeneration

INTRODUCTION Dental pulp regeneration is a part of regenerative endodontics, which includes isolation, propagation, and re-transplantation of stem cells inside the prepared root canal space. The formation of new blood vessels through angiogenesis is mandatory to increase the survival rate of re-transplanted tissues. Angiogenesis is defined as the formation of new blood vessels from preexisting capillaries, which has great importance in pulp regeneration and homeostasis. Here the contribution of human dental pulp stem cells and proangiogenic and antiangiogenic factors to angiogenesis process and regeneration of dental pulp is reviewed. METHODS A search was performed on the role of angiogenesis in dental pulp regeneration from January 2005 through April 2014. The recent aspects of the relationship between angiogenesis, human dental pulp stem cells, and proangiogenic and antiangiogenic factors in regeneration of dental pulp were assessed. RESULTS Many studies have indicated an intimate relationship between angiogenesis and dental pulp regeneration. The contribution of stem cells and mechanical and chemical factors to dental pulp regeneration has been previously discussed. CONCLUSIONS Angiogenesis is an indispensable process during dental pulp regeneration. The survival of inflamed vital pulp and engineered transplanted pulp tissue are closely linked to the process of angiogenesis at sites of application. However, the detailed regulatory mechanisms involved in initiation and progression of angiogenesis in pulp tissue require investigation.

Push‐out bond strength of a nano‐modified mineral trioxide aggregate

INTRODUCTION To analyze the push-out bond strength of Angelus WMTA (Angelus Dental Products), a nano-modification of WMTA (Kamal Asgar Research Center) and Bioaggregate (Innovative Bioceramix). METHODS Sixty 2-mm-thick root sections were prepared from 60 single-rooted human teeth. The dentin disks were randomly divided into three groups (n = 20) and filled with Angelus WMTA, Nano-WMTA, or Bioaggregate, respectively. Push-out bond strength values of the specimens were measured by a universal testing machine and examined under scanning electron microscope at × 40 magnification to determine the nature of the bond failure. The data were analyzed with a Kruskal-Wallis test. RESULTS The greatest mean for push-out bond strength (138.48 ± 11.43 MPa) was observed for the nano-modification of WMTA. The values decreased to 110.73 ± 11.19 and 25.64 ± 5.27 MPa for Angelus WMTA and Bioaggregate, respectively. There were significant differences between the groups (P < 0.001). Inspection of the samples revealed the bond failure to be predominantly adhesive type except for the nano-modification group, as some samples also exhibited cohesive failures. CONCLUSIONS It is concluded that the force needed for the displacement of the nano-modification of WMTA (NWMTA) was significantly higher than for Angelus WMTA and Bioaggregate.

Functional role of inorganic trace elements in angiogenesis—Part I: N, Fe, Se, P, Au, and Ca

Many inorganic elements are recognized as being essential for the growth of all living organisms. Transfer of nutrients and waste material from cells and tissues in the biological systems are accomplished through a functional vasculature network. Maintenance of the vascular system is vital to the wellbeing of organisms, and its alterations contribute to pathogenesis of many diseases. This article is the first part of a review on the functional role of inorganic elements including nitrogen, iron, selenium, phosphorus, gold, and calcium in angiogenesis. The methods of exposure, structure, mechanisms, and potential activity of these elements are briefly summarized. An electronic search was performed on the role of these elements in angiogenesis from January 2005 to April 2014. The recent aspects of the relationship between different elements and their role in angiogenesis, and production of pro- and anti-angiogenic factors were assessed. Several studies emphasized the role of these elements on the different phases of angiogenesis process in vivo. These elements can either enhance or inhibit angiogenesis events. Nitrogen in combination with bisphosphonates has antiangiogenic effects, while nitric oxide promotes the production of angiogenic growth factors. Iron deficiency can stimulate angiogenesis, but its excess suppresses angiogenesis events. Gold nanoparticles and selenium agents have therapeutic effects due to their anti-angiogenic characteristics, while phosphorus and calcium ions are regarded as pro-angiogenic elements. Understanding how these elements impact angiogenesis may provide new strategies for treatment of many diseases with neovascular component.