Bahram Ranjkesh

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).

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).

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.

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.

Comparison of two histopathologic methods for evaluating subcutaneous reaction to mineral trioxide aggregate

Objectives: One of the most important factors for suitable materials for pulp therapy is biocompatibility. Two histopathologic methods of Cox and Federation Dentaire International (FDI) were used to evaluate inflammation. In Cox method, density of inflammatory cells, tissue reactions like fibrosis, vascular responses like congestion and fibrin extravasation have been used to evaluate inflammatory reactions. The aim of this study was to compare the accuracy of pathologists’ interpretations using two different methods. Study design: Three pathologists observed the degree of inflammation in 225 histopathologic sections. These sections showed inflammation in subcutaneous connective tissue of rats adjacent to polyethylene tubes, filled with white or gray mineral trioxide aggregate. Empty tubes served as controls. Samples were harvested after 7-, 15-, 30-, 60-, and 90-days. All pathologists examined the sections under a light microscope (Carl Zeiss, Oberkochen, Germany) at ×400 magnifications. Chi-Square test was used to evaluate the difference between inflammation grades when one pathologist used two methods. Cohen’s Kappa value was used to measure agreement of three pathologists to recognize the degrees of inflammations when using one of the methods. Results: There were no significant differences between the two methods when one of the pathologist used these methods to report the degree of inflammation (p=0.054). However, two other pathologists reported significant differences between two methods (p=0.005, p=0.001). In the FDI method, there was an acceptable agreement between first and second, and first and third pathologist in terms of the degree of inflammation, and intermediate agreement existed between the second and third pathologist. With the Cox method, no agreement among the pathologists could be found. Conclusion: The results of three pathologists in terms of rating inflammation with the FDI method showed better agreement than with the Cox method. Therefore, FDI method is more reliable than the Cox method to evaluate inflammation. Key words: Biocompatibility, connective tissue, infammation, mineral trioxide aggregate.