Iranian Endodontic Journal

INTRODUCTION: All instrumentation techniques have been reported to be associated with extrusion of infected debris. The aim of this study was to evaluate the number of bacteria extruded apically from extracted teeth ex vivo after canal instrumentation using the two engine-driven techniques utilizing nickel-titanium instruments (Flex Master and Mtwo). MATERIALS AND METHODS: Seventy extracted maxillary central incisor teeth were used. Access cavities were prepared and root canals were then contaminated with a suspension of Enterococcus faecalis and dried. The contaminated roots were divided into two experimental groups of 30 teeth each and one control group of 10 teeth. Group 1, Flex Master; Group2, Mtwo; Group 3, control group: no instrumentation was attempted. Bacteria extruded from the apical foramen during instrumentation were collected into vials. The microbiological samples from the vials were incubated in culture media for 24 h. Colonies of bacteria were counted and the results were given as number of colony-forming units. The obtained data were analyzed using the Kruskal-Wallis one-way analysis of variance and Mann-Whitney U-tests, with α = 0.05 as the level for statistical significance. RESULTS: Findings showed that there was no significant difference as to the number of extruded bacteria between two engine-driven systems (P>0.05). CONCLUSION: Both engine-driven Nickel-Titanium systems extruded bacteria through the apical foramen.

INTRODUCTION: To examine the long-term effects of normal saline and a synthetic tissue fluid (phosphate buffered saline, PBS) on mineral trioxide aggregate (MTA). MATERIALS AND METHODS: Root-ends of twelve extracted human teeth were resected; root-end cavities were prepared and filled with MTA. Samples were randomly divided into two groups of six each. Teeth in group I were placed in normal saline, whilst teeth in group II were placed in PBS. After five months, elemental analysis of the surface of the root-end filling was performed using electron probe microanalysis (EPMA). RESULTS: Results showed that all teeth kept in PBS formed crystal deposits. In contrast, no such crystal formation was observed in teeth kept in normal saline solution. The results of elemental analysis showed that the composition of the crystals observed for teeth kept in PBS was consistent with that of a mineral hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂. CONCLUSION: Based on these in vitro results, we suggest that the hydration of MTA surface and the release of calcium from MTA in contact with phosphorous of PBS produced hydroxyapatite crystals over MTA and it may be a mechanism which is responsible for cementum formation during in vivo studies.

INTRODUCTION: Osteoblasts and periodontal ligament cells are major cells for wound healing after root end resection. The interaction of osteoblasts with filling materials could play a critical role in healing of surgical lesion. Adhesion and spreading of cells on material surface are the initial phase for cellular function. The purpose of the present study was the evaluation of morphology and attachment of human osteoblasts in present of white MTA, Portland cement (PC) and IRM as root end filling and perforation repair materials. MATERIALS AND METHODS: The human osteoblasts (MG-63 cell line) were prepared from Iranian Pasteur Institute; Cellular Bank, were grown in RPMI 1640 medium. The testing materials were mixed according to the manufacture's instruction, inserted in to the wells of 24-well flat-bottomed plate, and condensed to disk of 1mm thickness and 1×1mm diameter. Cells were added to the materials after two weeks. During 1,3,7 days intervals, the disk of materials along with cells were grown on their surface, examined by a scanning electron microscope (SEM). We used of IRM as negative group. RESULTS: Results showed that after 7 days many of osteoblasts were attached on the surface of white MTA and PC and appeared partially round or flat. The cells appeared round with no attachment and spreading in conjunction with IRM. CONCLUSION: The results indicate that human osteoblasts have a favorable response to white MTA and Portland cement compared with IRM.

INTRODUCTION: The aim of this study was to compare the cytotoxicity of ProRoot MTA (PMTA), Root MTA (RMTA) and Portland cement (PC) on human gingival fibroblasts (HGFs). MATERIALS AND METHODS: The extracts of the test materials were placed close to human gingival fibroblasts (HGFs) within 96-well plates. Cellular viability was assessed using MTT assay in different intervals (freshly mixed, 4, 24, and 168 hours after mixing). The data were analyzed using the One-way ANOVA and Tukey’s test at 95% significance level. RESULTS: It was indicated that there was not a significant difference in cytotoxicity of test materials (P>0.05). In addition, there was not a statistically significant difference between different time intervals within each group (P>0.05). CONCLUSION: PMTA, RMTA and PC showed comparative biocompatibility while evaluated in-vitro.

MATERIALS AND METHODS: Eighty-four single rooted human teeth were randomly divided into 7 groups, 12 cases each, and canals were instrumented with Mtwo rotary systems. 5.25% sodium hypochlorite, Smear Clear and 17% EDTA were used for irrigation of the canal during and/ or after instrumentation. After completion of instrumentation, all canals were dried with paper points and prepared to examine by scanning electron microscope. All SEM photomicrographs were scored at the coronal, middle and apical thirds of canals in each group. The data were statistically analyzed using Mann-Whitney and Kruskal-Wallis tests. RESULTS: In the group irrigated with Smear Clear alone, the coronal thirds of the canals were significantly cleaner than middle thirds (P= 0.013) and apical thirds (P=0.028). There were less smear layer in the coronal thirds compared to apical thirds (P=0.047) in the group irrigated with Smear Clear and NaOCl alternately .There were significantly more smear layer in the apical thirds compared to coronal thirds (P<0.001) and middle thirds (P=0.007) in the group that Smear Clear and NaOCl were used as final irrigations. There was not any significant difference between three-thirds of the canals in other groups. Comparison of the all groups showed a statistically significant difference (P<0.001) in the amount of debris and smear layer remaining at all three levels of the canals. CONCLUSION: The findings of this study suggested that a final rinsing by combination of a chelating agent like EDTA or Smear Clear and NaOCl is necessary to obtain favorable clean wall of root canals.

INTRODUCTION: The purpose of this in vitro study was to compare the accuracy of the new electronic apex locator Raypex5 with radiography for working length determination of straight and curved root canals. MATERIALS AND METHODS: Twenty straight and single canals of maxillary central teeth and twenty curved mesiobuccal canals of mandibular molar teeth were used. Access cavities were prepared and working lengths were determined by means of Raypex5 and conventional radiography then compared with actual working lengths (AWL). Data were analyzed by ANOVA with repeated measurements and Least Significant Difference (LSD) test. RESULTS: There was no significant difference between electronic and actual working length determination for straight canals (p=0.74). For curved canals the difference between electronic and actual working length was significant (p<0.0001). There was a significant difference between radiographic and actual working length determination either for straight and curved canals (p=0.024, p<0.0001). The difference between radiographic and electronic working length determination was also significant for straight canals (p=0.006). The percentage of electronic measurements within ±0.5 of AWL was 70% for straight canals and 35% for curved root canals. The percentage of radiographic measurements within ± 0.5 of AWL was 50% for straight canals and 25% for curved root canals. CONCLUSION: Raypex 5 is an apex locator that measured the tooth length within a clinically acceptable range especially in anterior straight canals.

INTRODUCTION: The antibacterial effects of calcium hydroxide (CH), mineral trioxide aggregate (MTA), and calcium enriched mixture (CEM) cement against various spp. of microorganisms were assessed in-vitro using agar diffusion test. MATERIALS AND METHODS: A base layer of Petri plates was made using Muller-Hinton agar. Four cavities were made in agar and filled with freshly mixed materials after 24 h. The microorganisms were seeded by pour plate. The plates were pre-incubated for 2 h at room temperature followed by incubation at 37˚C for 24 h. The inhibition zones diameters were measured by an independent observer. RESULTS: The highest mean diameters of growth inhibition zones were founded around CH and CEM cement. According to One-way ANOVA there was a significant difference among test groups (p<0.001); Post Hoc test revealed no significant difference between the mean zones diameter of CH and CEM cement. However, there was significant difference among CH and CEM cement in comparison with MTA group (p<0.001). CONCLUSION: It appears that CEM cement is a potent antibacterial agent like CH.

A mandibular first molar requiring root canal therapy was found with five canals, three mesial canals, and two distal canals. Initially, four canals (mesiobuccal, mesiolingual, distobuccal, and distolingual) were identified. The mesiobuccal and mesiolingual canals were found in their normal locations, and a fifth canal was noted between these two. This case demonstrates a rare anatomical configuration and supplements previous reports of the existence of such configurations in mandibular first molars.