Dental Research Journal
Volume:3 Issue: 2, Mar 2006

Introduction
Various kinds of hand-held or rotary techniques are used for mechanical preparation of the canal. The purpose of this study was to assess the influence of the number of applications on apical extrusion of debris in conventional and two rotary instrumentation techniques (Profile, Flex Master).
Methods and Materials
In this in vitro study, 75 extracted single-rooted human mandibular premolars with curvature between 0-10 degrees were selected and divided into three groups of 25 teeth each. All teeth were shortened to length of 15 mm by cutting the crown. Group H was prepared by hand step back technique, group P was prepared by profile system and group F was prepared by Flex Master system. The number of applications was according to manufacturer recommendation. For collection of debris, vials of distilled water were used that were weighed before preparation by 0.0001 weighing machine. At the end of canal preparation, vials were completely dried and weighed again. The difference between the weights of vials in two stages was the weight of debris extruded from apical foramen. The mean weight of debris in various numbers of applications within each system was compared by one–way variance analysis.
Results
Comparing the various numbers of applications in each system, it was noted that only in profile group, with increasing the number of applications, the quantity of debris extrusion was reduced.
Discussion
Unused profile instruments induce more extrusion of debris from apical foramen, rather than used ones.

Introduction
Proper cleaning and shaping of the root canal system is one of the most important aspects of endodontic therapy. To estimate the canal length before instrumentation in endodontic treatment, traditionally, conventional radiographic techniques and, recently, Direct Digital Radiography (DDR) are applied. The application of computer technology in radiography has allowed less exposure time for image acquisition, better storage and retrieval, and transmission to remote sites in a digital format, elimination of processing, and a considerable time saving. The purpose of this study was to compare the accuracy of DDR and conventional radiography in determination of working lengths of curved canals in first mandibular molars.
Methods
Forty extracted human first mandibular molars with root curvature were selected. Samples were divided into two groups: With root curvatures less and more than 25°. The samples were mounted in plaster blocks and their canal lengths were estimated by using DDR and conventional radiographs. Regression analysis, correlation coefficient, and t test were used for statistical analysis.
Results
In spite of the greater accuracy of conventional radiography in canals with curvature 25°, the differences were not statistically significant.
Discussion
Both conventional radiographs and DDR can be used to determine working length during endodontic therapy.

Introduction
The aim of this study was to compare the characteristics of deflection load of three kinds of nickel titanium closed coil springs.
Methods and Materials
This research was an experimental study. Research sample contains three kinds of NiTi closed coiled springs (heavy, medium, light) from GAC, 3M, and RMO factories. 10 springs with 9 mm length for each group (totally 90 springs) were subjected to tensile test. They were pulled to 12 mm extension by Dartec machine and then were released. Our variables were maximum force at 12 mm extension, force at the start of the plateau, deflection at the start of plateau, mean force of plateau, plateau slope, force at the end of plateau, deflection at the end of plateau. For tensile test, we used DARTEC universal machine. The data were analyzed by ANOVA and Duncan tests.
Results
In comparision among identical coils from different factories, the deflection at the end of plateau hadn’t significant difference (P=0.107) but the other parameters had significant differences (P

Introduction
The application of immunohistochemical method has resulted in marked improvement of the microscopic diagnosis of neoplasms combined with H&E staining. Although unique cellular antigens have not been found in salivary gland neoplasms, multiple less specific immunomarkers have been used and may be helpful in elucidating the role of myoepithelial differentiation in those neoplasms. The aim of this study was to evaluate immunohistochemical myoepithelial markers (GFAP, actin, vimentin, and S100) in mucoepidermoid carcinoma and pleomorphic adenoma of salivary glands for differential diagnosis of these tumors and specification of their histogenesis.
Methods and Materials
Formalin-fixed and parafin embedded tissue sections of 25 pleomorphic adenoma and 25 mucoepidermoid carcinoma were immunohistochemically analyzed for the presence of actin, vimentin, GFAP, and S100 protein. A standard biotin-streptavidin procedure was used after antigen retrieval. Immunoreactivity of myoepithlial cells and chondromyxoid areas in pleomorphic adenoma and mucus cell, epidermoid cells, and intermediate cells in mucoepidermoid carcinoma were evaluated and immunoreactivity was scored on a scale of 0 to (Regezi method) with o as negative, 1 as scattered staining, 2 as 25% to 50% of positive tumoral cells, and 4 as more than 50% positive cells. The data were analyzed with chi-square test, and significance level was considered as 0.05 (P

Introduction
The materials used in sealing furcating perforation can have considerable effects on controlling the ensuing inflammation and periodontal repair. The objective of the present study was to carry out a histological comparison between the effects of pro-root, cold ceramic, glass-ionomer cement, and root MTA on the healing of periodontal tissues after furcal perforation in dog''s teeth.
Methods and Materials
One-hundred premolar teeth of one-year old dogs were used in this experimental/animal study. After anesthetizing the dogs and the premolar teeth, the access cavities were prepared at the occlusal level and the root canals were instrumented and filled with gutta percha and AH26 sealer, using the step-back technique. Furcations were perforated to a size of 3×3 mm2, using long burs. These areas were then randomly filled with aforementioned four test materials (a total number of 84 premolar teeth) while the access cavities were filled with amalgam. The remaining 16 teeth were selected to serve as positive and negative controls. Biopsy samples were taken from the perforated areas at 1, 2, and 3-month intervals and were transferred to laboratory for pathological examination. The results were statistically analyzed, using the Kruskal-Wallis and Mann Whitney tests.
Results
The statistical analysis revealed that under similar conditions, periodontal tissues surrounding Pro-root, show less inflammatory response than the other three materials. However, no significant differences were observed among the four studied materials during 1 and 2months as evidenced by the biopsy samples (P>0.05). For longer period (three month), however, samples surrounding cold ceramic and Root MTA showed decreasing inflammatory responses.

Discussion
From the findings of the present study, it may be concluded that although tissues adjacent to Pro-root showed less inflammatory response than other three test materials, all of them (Pro-root, Glass-ionomer cement, cold ceramic, and Root MTA) may be considered to be suitable materials for sealing furcal perforation providing. They receive approval by other tests including micro leakage, cytotoxicity, tissue analysis, and etc.

Introduction
Dentine hypersensitivity is a common clinical problem in dental practices. So several methods such as, Nd: YAG laser have been used to treat this problem. Previous studies reported that Nd:YAG laser irradiation on root surface makes some thermal changes, like dentine melting and some other side effects which are related to power of laser irradiation. The aim of our study was to compare two different settings of Nd: YAG laser to evaluate their efficacy in occluding dentinal tubules and their side effects by means of SEM.
Methods
15 newly extracted mandibular molars were selected and the specimens with certain dimensions from buccal surface and below CEJ were prepared. Specimens were divided in 3 groups: group 1 (control), were not irradiated by laser; group 2, irradiated by Nd:YAG laser (0.5w, 10Hz, 60Sec, 2 times); and Group 3, irradiated by Nd:YAG laser (1w, 10Hz, 60Sec, 2 times). After preparation and gold coating of specimens, the photomicrographs were seen by SEM in magnification of 100 and 1500. Finally, the number and diameter of dental tubules, crater and microcraks were determined in each group. After that, the data was analyzed using ANOVA test.
Results
Results of this study showed that diameter of dentinal tubules were reduced in Nd: YAG irradiated groups, compared with control group. Also there were no significant differences in the mean number of open dentinal tubules between Nd:YAG (0.5 watt) and control group. On the contrary, there were significant differences between Nd:YAG (1 watt) and the other groups . Meanwhile, no group showed micro cracks or craters.
Conclusion
The results of this study show that Nd:YAG laser irradiation can cause thermal effects such as decrease in dentinal tubules diameter or their occlusion. Also 1 watt power Nd:YAG laser is more effective than 0.5 watt power in tubules occlusion which is a necessary factor in dentine desensitization.

Introduction
Chronic periodontitis has been associated with cardiovascular diseases. The hypothesis that oral, especially periodontal, infections have potentially serious systemic implications, is now gaining credence.
Methods and Materials
Cases were 45-60 years old patients who had been hospitalized in one of cardiologic care units or emergency wards of Isfahan Medical University, for acute myocardial infarction (AMI). Controls had no evidence of acute myocardial infarction, all receiving comprehensive periodontal examination. Information such as age, socioeconomic state, smoking, and diabetes history were obtained from hospital records and direct interview. A total number of %6 people participated in our study, based on informed consent, were designated as two groups of case and control. The association between mean attachment level and number of missing teeth with studied groups were analyzed with SPSS statistical software.
Results
The association of the mean attachment level and also the number of missing teeth with case status were statically significant associated (P

Introduction
The maxillary sinuses are the first sinuses form in the embryonic period and begin to be pneumatized from 4 th year of life. Sinusitis is a common disease in children and its on–time diagnosis and treatment is very important to prevent relevant side effects. Unfortunately, in some medical centers Waters'' radiography is routinely prescribed for the diagnosis of sinusitis, regardless of the trend of sinuses evolution in children. The aim of this study was to evaluate the efficacy of Waters'' radiography in diagnosis of children''s sinusitis.
Methods and Materials
This study was an observational, cross- sectional, and retrospective study. The samples included 180 of 0-12 years old children with sinusitis who had referred to Isfahan city clinics and the physicians had prescribed Waters'' radiography for them. Required information was gathered via examination and enquiry into the patients'' records. The radiographs were blindly surveyed by two radiologists (an oral and a general radiologist) and the data were statistically analyzed using the Chi-square and Kruskal – Wallis statistical tests.
Results
The coefficient of agreement between clinical signs and Waters'' radiographic features in the samples was 52%.The greatest frequency rate of non – pneumatized sinuses was reported in the group of 3-years-olds and under. 30% of the maxillary sinuses were found to be normal in radiography (P=0.0005). No difference was observed between sinusitis radiographic results, based on the time of involvement (P=0.219) and sex (P=0.546).Cough (%89.4) and nasal purulent excretions (%53.2) were the most common clinical symptoms of sinusitis. However, clinical signs in 2 groups of with positive radiographic results and with normal sinuses showed no statistically significant difference (0.11