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.

Effect of Beta-Blockers on Number of Osteoblasts and Osteoclasts in Alveolar Socket Following Tooth Extraction in Wistar Rats.

STATEMENT OF THE PROBLEM: Various researchers have suggested the use of ß2-adrenergic receptor antagonists in prevention or treatment of bone resorption. PURPOSE: This study aimed to evaluate the effect of ß2-adrenergic receptor antagonists on number of osteoclasts and osteoblasts involved in the healing of extraction socket of maxillary first molar in rats. MATERIALS AND METHOD: Maxillary first molars of 40 rats were extracted and divided into two groups. The test group received 0.1 mg/kg propranolol intraperitoneally daily. The controls received normal saline. At days 7, 14, 21 and 28 post-extraction, 5 rats were euthanized from each group. Maxillary bone was resected and the mean number of osteoblasts and osteoclasts in tooth socket was measured. RESULTS: After 1 week, the number of osteoclasts in the controls was significantly higher than the test group. A significant increase in the number of osteoclasts in both groups at week 1 was observed compared to the following weeks (p< 0.05). The number of osteoblasts in the controls at second week reached its maximum rate but stayed constant in the 3rd and 4th weeks. Osteoblasts in the test group increased similar to the controls but reached its maximum at 3rd week and showed a significant increase compared to the controls (p< 0.05). CONCLUSION: ß2 adrenergic receptor antagonists decrease the number of osteoclasts and increase the number of osteoblasts during extraction socket healing.

Tissue Reaction and Biocompatibility of Implanted Mineral Trioxide Aggregate with Silver Nanoparticles in a Rat Model.

INTRODUCTION: Biocompatibility and antimicrobial activity of endodontic materials are of utmost importance. Considering the extensive applications of mineral trioxide aggregate (MTA) in dentistry and antimicrobial properties of silver nanoparticles, this study aimed to evaluate the subcutaneous inflammatory reaction of rat connective tissues to white MTA with and without nanosilver (NS) particles. METHODS AND MATERIALS: Polyethylene tubes (1.1×8 mm) containing experimental materials (MTA and MTA+NS and empty control tubes) were implanted in subcutaneous tissues of seventy-five male rats. Animals were divided into five groups (n=15) according to the time of evaluation: group 1; after 7 days, group 2; after 15 days, group 3; after 30 days, group 4; after 60 days and group 5; after 90 days. The inflammatory reaction was graded and data was analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Statistical significance was defined at 0.05. RESULTS: Comparison of cumulative inflammatory reaction at all intervals revealed that the mean grade of inflammatory reaction to MTA, MTA+NS and control samples were 3, 2 and 2, respectively. According to the Mann-Whitney analysis there were no significant differences between MTA+NS and MTA (P=0.42). CONCLUSION: Incorporation of 1% nanosilver to MTA does not affect the inflammatory reaction of subcutaneous tissue in rat models.

A review of antibacterial agents in endodontic treatment.

Microorganisms play a major role in initiation and perpetuation of pulpal and periapical diseases. Therefore, elimination of the microorganisms present in the root canal system is the fundamental objective of endodontic treatment. The use of mechanical debridement, chemical irrigation or other antimicrobial protocols and intra-canal medicaments are critical to attain this goal. The aim of this article was to review the antimicrobial agents and their properties in endodontics.

Effects of various mixing techniques on push-out bond strengths of white mineral trioxide aggregate.

INTRODUCTION: The aim of this study was to evaluate the effect of 3 different mixing methods on push-out bond strength of white tooth-colored mineral trioxide aggregate (MTA). METHODS: Sixty 2-mm-thick root sections were prepared from 60 single-rooted human teeth and filled with MTA. The samples were randomly divided into 3 groups (n = 20) of MTA mixed by ultrasonic, trituration, or conventional methods and then allowed to set for 72 hours in a synthetic tissue fluid environment. Push-out bond strength values of the specimens were measured by a universal testing machine and examined under a stereomicroscope at × 4 to determine the nature of the bond failure. RESULTS: The means of push-out bond strength values of white MTA in the ultrasonic, conventional, and trituration groups were 105.67 ± 12.79, 118.95 ± 12.76, and 99.60 ± 14.27 MPa, respectively. The differences between the 3 groups were not statistically significant. CONCLUSIONS: On the basis of the results of this study, it can be concluded that different mixing methods have no significant effect on push-out bond strength of white MTA.

Endodontic treatment of a hypertaurodont mandibular second molar: a case report.

A 28-year old patient was referred for endodontic treatment of his left mandibular second molar. The patient had no history of systemic diseases and his chief complaint was spontaneous pain in left posterior region of mandible. Clinically, there was a deep caries in the left mandibular second molar. Radiographic examination of this tooth revealed a long crown containing large pulp chamber and two short roots with a apically located furcation, indicating hypertaurodontism. After coronal access preparation, five orifices were found including mesiolingual, mesiobuccal, distobuccal, mid-distal and distolingual. Subsequent to root canal preparation, a modified filling technique was used for canal obturation. After one year the treated tooth was symptom free.