Journal of Dental School
Year:2011 | Volume:29 | Issue:2 (88)|Papers Count:8

Background and Aim: Gutta-percha is shown to be the most widely used root canal filing material due to its well-known low toxicity potential. A new kind of gutta-percha with nanosilver coating has synthesized by Iranian researchers and claimed to have antibacterial an antifungal properties. The aim of this study was to compare the cyotoxicity of nanosilver coated gutta-percha, GuttaFlow (GF), with normal gutta-percha (GP) on mouse fibroblast cell line L929. Materials & Methods: In this in vitro study, cytotoxicity was evaluated by fibroblast cell culture and its direct contact with the test materials. 30 specimens inserted in test tubes and cell survival fraction was estimated by MTT test after 1hour, 24 hour, and 1 week. Two way ANOVA, one way ANOVA and Tukey HSD were used for statistical analysis.Results: After 1 hour, cytotoxicity among three 3 test materials was significantly different. Nanosilver coated gutta-percha had the highest cytotoxicity and GuttaFlow the lowest one (P<0.01). After 24 hour, no significant differences were observed (P=0.37). After 1 week, GuttaFlow showed significantly higher cytotoxicity than normal gutta-percha and nanosilver gutta-percha (P<0.001). However, this difference was not significant between nanosilver and normal gutta-percha (P>0.05).Conclusion: In nanosilver gutta-percha group, the most cytotoxicity was observed after 1 hour while it was decreased with time and became equal to normal gutta-percha after 24 hours and after 1 week, it reached the lowest level among 3 test materials.

Background and Aim: Perforation is one of the most important causes of failure of endodontics treatment. Several materials have been proposed for a non surgical repair of furcal perforation and MTA is one of them. The aim of this study was to evaluate repairing of furcal perforation of primary molars with Root MTA and ProRoot MTA. Materials & Methods: This in vitro study was conducted on 54 teeth that were randomly divided into four groups: Root MTA (n=24), Pro Root MTA (n=24), positive and negative controls (n=6). After preparation of access cavity, perforations were made and the perforation areas were repaired with Root MTA and ProRoot MTA. After staining and preparation of mesiodistel longitudinal section, die leakage was measured with stereomicroscope. The data was analyzed with Mann Whitney test. P<0.05 was considered as significant level.Results: The data showed that ability of sealing of ProRoot MTA is more than Root MTA. Conclusion: Based on the results of this study Root MTA is not a suitable substitute for ProRoot in repairing of furcal perforation of primary molars.

Background and Aim: The aim of this study was to evaluate the accuracy of cephalometric measurements using computerized tracing in comparison with hand tracing of radiographic printouts.Method & Materials: A sample was used, consisting of 90 standardized lateral cephalometric radiographs, obtaining from 10 years old male and female patients with normal skeletal and dental components. The radiographs were analyzed by two different observers. the first observes performed the manual and computerized tracings and then the procedure randomly rechecked by the second observer. A total of 13 anatomical landmarks of McNamara analysis were located and angular and linear measurements were obtained. Measurement reproducibility was evaluated by calculating intraclass correlation coefficients (ICC). Differences greater than 0.05 were considered to be statistically significant.Results: Significant differences were found between the methods for “Inferior Airway Space” in females. Cephalometric measurements of most parameters were reproducible for both methods.Conclusion: The study showed that confidence can be increased in tracings obtained from computer-assisted cephalometric analysis. as the discrepancies found between both manual and computerized, were mostly not statistically significant, any differences were minimal and clinically acceptable.

Background and Aim: Evaluating of academic members on students assessment is a common kind of educational evaluation in most countries such as Iran. Since recognition of the strengths and weaknesses of this evaluation method has important role in educational promotion, the present study was designed to assess the reliability of post graduate students’ in faculty evaluation.Materials & Methods: this is descriptive study which is routinely used in dental school, consisted of 10 questions with 4 point Likert scale was completed twice by students with one week interval. For intraobserver reliability determination, Weighted kappa and to determine interobserver reliability, generalized Weighted kappa were used. The reliability of total students in all fields was assessed using intra class coefficient. The data were analyzed through SPSS 11.5. Results: Reliability of students in different departments showed no significant statistical difference (p=0.569). The mean intraobserver reliability was 0.414 & the mean interobserver reliability was 0.297. The results showed that intraobserver reliability in cases were the initial score was best or worst was significantly higher than the cases were the initial score was good or moderate (p=0.034). The highest intraobserver reliability was in the field of “creating motivation for further study & research” and the lowest reliability belonged to the field of “tolerance to critics & suggestions”.Conclusion: The results of this study showed that the reliability of post graduate students’ ratings for faculty evaluation was not high.

Background and Aim: Millions of teeth are saved each year by root canal therapy. Although current treatment modalities offer high levels of success for many condition, an ideal form of therapy might consist of regenerative approach in which a biologically based procedures designed to replace damaged structures, including dentin, root structure and pulp-dentin complex. The aim of this study was to collect information about the stem cell and their role in new regeneration therapies in endodontics. Literature review: Data was collected by searching Pubmed and Cochrane data bases using key words such as stem cell, regenerative endodontics, pulp revascularization and tissue engineering. Selected reference text books were searched using the same search strategy. The search results was categorized according to methodological strength; they also selected only if qualified for our inclusion criteria. Although regenerative endodontic procedures are much more effective in regeneration of pulp-like tissue, (pulp-dentin complex), but despite these applications and considerable evolution of certain medical procedures of tissue regeneration, there has not been significant translation of any these therapies into clinical endodontic practice. Conclusion: More studies are required to overcome technical and clinical limitation of pulp and dentin tissue regeneration both to result in pulp-dentin tissue regeneration, and to form the functional structure of the tooth from stem cells.

Background and Aim: Simultaneous formation of third molar crown with second molar eruption may possibly cause to second molar impaction due to third molar bud intervention. A tooth impaction leads to numerous clinical problems for the patient and the present study assessed the effect of third molar size, axis angulation, developmental stage and its bud position with possibility of mandibular second molar impaction in patients with doubtful impaction of lower second molars. Materials & Methods: In this descriptive-analytical study, 5420 records of 10-12 years old patients underwent orthodontic treatments in Tehran and Shahid Beheshti Dental Schools and private clinics were assessed and 38 patients (26 females and 12 males) were selected with possible impaction of lower second molars forming case group. 38 control patients with no prospective possibility for impaction of second molars were selected from the same centers and matched with the cases. The third molar axis angulation towards second molar, first molar and mandible base, mesiodistal width of wisdom teeth relative to second molar, Nolla developmental stage and third molar bud position regarding second molars were calculated and analyzed by student t, chi-square and mann-whitney U tests in both groups.Results: The mean value of third molar angulation towards second molar, first molar and mandibular base were 24.16, 49.26 and 54.42 degrees in case group and 14.42, 39.39 and 45.0 degrees in control group respectively with significant differences (P<0.001 in three variables). The mean mesiodistal width of third molar relative to second molar was 0.9903 in case Group and 0.9695 in control Group with no significant differences. Nolla developmental stage and marginal ridge of third molar bud towards second molar showed no definite effect on second molar impaction. Conclusion: The results suggest third molar angulation towards second molar, first molar and mandibular jaw base to be significantly higher in patients with possible mandibular second molar impaction than those without prospective possibility for second molar impaction. Although, no significant differences in mesiodistal width of third molar relative to second molars, developmental stage and marginal ridge of third molar bud regarding second molar were observed between the two groups.

Background and Aim: Patients’ levels of knowledge and expectations for treatment with dental implants have increased tremendously in recent years. Also treatment with dental implants has proven to be a predictable modality for replacing missing or failing teeth with various types of fixed or removable dental prosthesis. It was traditionally thought that the healing period of 3 to 6 months is necessary. Recent studies show high level of survival rates with immediate and early loading. The object of this study was to evaluate current evidence for evaluating recommended loading protocols for dental implants. Method & Materials: A comprehensive systematic review of the literature was conducted by using Pubmed and Science Direct by the end of September 2010. The selection of publications reporting on human clinical studies was based on predetermined inclusion criteria. Results: One hundred thirty eight out of 971 papers were approved for inclusion criteria. 39 were discussing early loading. 40 were discussing immediate loading and 57 were discussing conventional loading and 7 were discussing fresh socket implant placements. Conclusion: Existing literature supports loading of micro roughened implants in edentulous and partially edentulous maxilla and mandible between six and eight weeks subsequent to implant placement with fix or removable prosthesis, it’s also possible to load dental implants in mandible in less than one week after placement with fix and removable prosthesis. But current evidence does not support loading edentulous and partially edentulous maxilla in less than eight weeks and recommends conventional loading (after three months). Special considition such as lack of primary stability, alveolar ridge augmentation, sinus floor elevation, presence of parafunction, compromised host status and dental complication should be considered as risk factors for immediate and early loading. In these situations conventional loading is recommended. Loading between two and six weeks are not recommended.

Background and Aim: Premature contact of teeth in posterior crossbite may be associated with facial asymmetry. To describe the surgical treatment of mandibular deviation associated with a marked facial asymmetry, and build up the two upper lateral incisors in place of the two upper central incisors.Case Report: A 20 year-old boy with a unilateral posterior crossbite, noticeable facial asymmetry, and anterior crossbite is presented. He had a history of head injury in mixed dentition period. The upper central incisors were lost during trauma and the created space was replaced by the two upper lateral incisors. A removable appliance was used to correct the crossbite and it was followed by fixed appliances. Orthognathic surgery was done to complete the treatment .After that the two upper lateral incisors were built up and reshaped. Treatment resulted in a marked improvement in facial symmetry, elimination of the mandibular displacement and a stable occlusion. Conclusion: A patient with mandibular deviation and marked facial asymmetry was successfully treated surgically and two upper lateral incisors were built up and reshaped in place of the two upper central incisors.