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Dentistry, Shiraz University of Medical Sciences - Volume:14 Issue: 3, Sep 2013

Journal of Dentistry, Shiraz University of Medical Sciences
Volume:14 Issue: 3, Sep 2013

  • تاریخ انتشار: 1392/06/12
  • تعداد عناوین: 10
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  • Aa. Haghnegahdar, P. Bronoosh, H. Jami Page 1
    Dear Sir Recently, all aspects of life have been changed & impressed by revolution of computer science. Education, as one of the most important part of life, is also affected by improvements such as Internet and E-books. Traditional books at least to some extent are slowly replaced by electronic and digital publications. These, could be produced massively in less time and lower price which means simple accessibility all around the word.Today, instead of participating in boring classes, students can play the digital manuscripts of lectures as many times as they want at any time of the day, without getting out of the home. This eliminates the time needed for transport and its fees and risks.In addition to potentials of multimedia used in these techniques which simplifies the process of learning, questions and tests may be applied in these digital lectures which give the user the choice to evaluate the learning process, so the student will play a more active role in process of education. Many advantages of electronic education make it desirable for most of titles. So, today, it is becoming a scale of evaluation of education institutes, i.e., the more the titles instructed by means of digital education, the higher the rank of the institute.Digital education, in our country, although not really new, comprises a very minor part of education. Tradition classes are still the most popular method for teaching, which imparts its fees.We have many things to do to benefit fully from potential advantage of digital education. Obviously preparing the needed hardware background is of utmost importance. Beside, lessons should be prepared in digital form and some percent of education assigned to E-learning.Regarding the need, software, for introducing the basics of radiology, is prepared in radiology department in Shiraz dental school as a student thesis. The composition of X-ray tube, the mechanism of X-ray production, the composition of radiographic film, latent image formation and film processing are described in this software, by means of video films, animations and photographs. This software can be used by dental students before entering radiology department, to simplify the understanding of basic principles of dental radiology. The software is presented in the website: http://hsoft.ir80.com as Review of Dental Radiology Basics Software and can be downloaded freely. Future revised forms also will be available.We hope that this software can help dental students to become familiar with some Far-fetched principles of radiology and acts as a starting point for developing E-learning in radiology department and other parts of our dental schools.
  • F. Sharafeddi, H. Yousefi, Sh. Modiri, A. Tondari, Sr. Safaee Jahromi Pages 90-95
    Statement of Problem: Microleakage is one of the most frequent problems associated with resin composites, especially at the gingival margin of posterior restorations. Insertion of fibers in composite restorations can reduce the total amount of composite and help to decrease the shrinkage.
    Purpose
    The aim of this study was to evaluate the effect of polyethylene fiber inserts on gingival microleakage of class II composite restorations using two different adhesive systems.
    Materials And Method
    In this experimental study, class II cavities were prepared on 60 premolars. The gingival floor was located 1.0 mm below the CEJ. Dimension of each cavity were 3 mm buccolingually and 1.5 mm in axial depth. The specimens were divided into 4 groups according to the adhesive type and fiber insert (n=4). Single bond and Clearfill SE bond and Filtek p60 were used to restore the cavities. In groups without fiber inserts composite was adapted onto cavities using layering technique. For cavities with fiber inserts, 3 mm piece of fiber insert was placed onto the composite increment and cured. The specimens were stored in distilled water at 37oC for 6 months. All specimens were subjected to 3000 thermo-cycling. The tooth surfaces except for 1 mm around the restoration margins covered with two layers of nail varnish. The teeth were immersed in 2% Basic Fuchsin for 24 hours, then rinsed and sectioned mesiodistally. The microleakage was determined under a stereomicroscope (40X). Data were statistically analyzed by Kruskal-wallis and Mann-Whitney U tests (p< 0.05).
    Results
    The Kruskal-Wallis test revealed no significant differences in mean microleakage scores among all groups (p= 0.281).
    Conclusion
    Use of polyethylene fiber inserts and etch-and-rinse and self-etch adhesives had no effect on microleakage in class II resin composite restorations with gingival margins below the CEJ after 6- month water storage.
  • F. Balouch, E. Jalalian, M. Nikkheslat, R. Ghavamian, Sh. Toopchi, F. Jallalian, S. Jalalian Pages 96-102
    Statement of Problem: Various impression techniques have different effects on the accuracy of final cast dimensions. Meanwhile; there are some controversies about the best technique.
    Purpose
    This study was performed to compare two kinds of implant impression methods (open tray and closed tray) on 15 degree angled implants.
    Materials And Method
    In this experimental study, a steel model with 8 cm in diameter and 3 cm in height were produced with 3 holes devised inside to stabilize 3 implants. The central implant was straight and the other two implants were 15° angled. The two angled implants had 5 cm distance from each other and 3.5 cm from the central implant. Dental stone, high strength (type IV) was used for the main casts. Impression trays were filled with poly ether, and then the two impression techniques (open tray and closed tray) were compared. To evaluate positions of the implants, each cast was analyzed by CMM device in 3 dimensions (x,y,z). Differences in the measurements obtained from final casts and laboratory model were analyzed using t-Test.
    Results
    The obtained results indicated that closed tray impression technique was significantly different in dimensional accuracy when compared with open tray method. Dimensional changes were 129 ± 37μ and 143.5 ± 43.67μ in closed tray and open tray, while coefficient of variation in closed- tray and open tray were reported to be 27.2% and 30.4%, respectively.
    Conclusion
    Closed impression technique had less dimensional changes in comparison with open tray method, so this study suggests that closed tray impression technique is more accurate.
  • Sm. Zahed Zahedani, M. Oshagh, Sh. Momeni Danaei, Smm. Roeinpeikar Pages 103-110
    Statement of Problem: One of the major outcomes of orthodontic treatment is the apical root resorption of teeth moved during the treatment. Identifying the possible risk factors, are necessary for every orthodontist.
    Purpose
    The aim of this study was to compare the rate of apical root resorption after fixed orthodontic treatment with standard edgewise and straight wire (MBT) method, and also to evaluate other factors effecting the rate of root resorption in orthodontic treatments.
    Materials And Method
    In this study, parallel periapical radiographs of 127 patients imaging a total of 737 individual teeth, were collected. A total of 76 patients were treated by standard edgewise and 51 patients by straight wire method. The periapical radiographs were scanned and then the percentage of root resorption was calculated by Photoshop software. The data were analyzed by Paired-Samples t-test and the Generalized Linear Model adopting the SPSS 15.0.
    Results
    In patients treated with straight wire method (MBT), mean root resorption was 18.26% compared to 14.82% in patients treated with standard edgewise technique (p<. 05). Male patients had higher rate of root resorption,statistically significant (p<. 05). Age at onset of treatment, duration of treatment, type of dental occlusion, premolar extractions and the use of intermaxillary elastics had no significant effect on the root resorption in this study.
    Conclusion
    Having more root resorption in the straight wire method and less in the standard edgewise technique can be attributed to more root movement in pre-adjusted MBT technique due to the brackets employed in this method.
  • F. Shafiei, S. Doustfatemeh Pages 111-117
    Statement of Problem: The use of tooth bleaching agents has been very popular treatment in dentistry. The bleaching agents have an inherent potential to impair surface properties of existing composite resin restorations.
    Purpose
    This study evaluated the effect of a combined bleaching regimen on the surface microhardness of a Silorane-based and a sealed methacrylate-based composite.
    Materials And Method
    Forty-five specimens of methacrylate-based composite (Ice) and 18 specimens of Silorane composite (Filtek Silorane, 3M ESPE; USA) were prepared and randomly divided into 5 (1-5) and 2 (6-7) groups (n=9), respectively. After 8-week aging, groups 1 and 6 were remained with no treatment. In groups 2, 4 and 5, the specimens were covered by a surface sealant and light cured. In groups 3, 4, 5 and 7, the specimens were bleached with hydrogen peroxide 40% and then carbamide peroxide 20% for seven days. In group 5, after bleaching, the sealant was removed by polishing. Surface microhardness was measured and the data were analyzed using one-way ANOVA and Tukey tests (α=0.05).
    Results
    The microhardness values of groups 2 to 4 were significantly lower than that of group1 (p <0.05). There was no significant difference among groups 1, 5, 6 and 7 (p> 0.05).
    Conclusion
    The combined bleaching regimen used in this study had a substantial negative effect on methacrylate and sealed methacrylate composites but not on Silorane composite. Polishing following the bleaching on the sealed composite yielded a hardness value similar to that of unsealed methacrylate composite (control).
  • M. Vojdani, K. Torabi, E. Farjood, Aar. Khaledi Pages 118-129
    Statement of Problem: Metal-ceramic crowns are most commonly used as the complete coverage restorations in clinical daily use. Disadvantages of conventional hand-made wax-patterns introduce some alternative ways by means of CAD/CAM technologies.
    Purpose
    This study compares the marginal and internal fit of copings cast from CAD/CAM and conventional fabricated wax-patterns.
    Materials And Method
    Twenty-four standardized brass dies were prepared and randomly divided into 2 groups according to the wax-patterns fabrication method (CAD/CAM technique and conventional method) (n=12). All the wax-patterns were fabricated in a standard fashion by means of contour, thickness and internal relief (M1-M12: representative of CAD/CAM group, C1-C12: representative of conventional group). CAD/CAM milling machine (Cori TEC 340i; imes-icore GmbH, Eiterfeld, Germany) was used to fabricate the CAD/CAM group wax-patterns. The copings cast from 24 wax-patterns were cemented to the corresponding dies. For all the coping-die assemblies cross-sectional technique was used to evaluate the marginal and internal fit at 15 points. The Student’s t- test was used for statistical analysis (α=0.05).
    Results
    The overall mean (SD) for absolute marginal discrepancy (AMD) was 254.46 (25.10) um for CAD/CAM group and 88.08(10.67) um for conventional group (control). The overall mean of internal gap total (IGT) was 110.77(5.92) um for CAD/CAM group and 76.90 (10.17) um for conventional group. The Student’s t-test revealed significant differences between 2 groups. Marginal and internal gaps were found to be significantly higher at all measured areas in CAD/CAM group than conventional group (p< 0.001).
    Conclusion
    Within limitations of this study, conventional method of wax-pattern fabrication produced copings with significantly better marginal and internal fit than CAD/CAM (machine-milled) technique. All the factors for 2 groups were standardized except wax pattern fabrication technique, therefore, only the conventional group results in copings with clinically acceptable margins of less than 120um.
  • M. Farzin, F. Bahrani, E. Adelpour Pages 130-135
    Statement of Problem: One of the most clinical challenging issues in prosthodontics is debonding of soft liners from the denture base.
    Purpose
    The aim of this study was to evaluate and compare tensile bond strength between soft liner and heat-cured acrylic resin when immersed in two different types of denture cleanser and distilled water, at different period of times.
    Materials And Method
    In this experimental in vivo study, 238 heat-cured acrylic blocks were made. A soft liner was embedded between the acrylic blocks. Samples were divided into four groups: 17 samples were in the control group and were not soaked in any solution. The remaining samples were divided into 3 groups (Distilled water, Calgon and Fittydent). Each group was then subdivided into two subcategories, regarding the immersion time variable; 15 and 45 minutes. All samples were placed in tension force and tensile bond strength was recorded with the testing machine. One- way ANOVA and Tucky HSD post-hoc test were adopted to analyze the yielded data (α> 0.05).
    Results
    Specimens which were immersed in two denture cleansers (Fittydent and Calgon) and in distilled water showed significant difference (p= 0.001) in bonding strength when compared to the control group. The subjects immersed in denture cleanser solutions and distilled water did not reveal any significant difference (p= 0.90). For all groups; most of the bonding failures (72%) were cohesive type.
    Conclusion
    The effect of the denture cleansers and distilled water on the bond strength was not statistically different; however, the difference was significant between the immersed groups with the non-immersed group. Moreover, type of the denture cleanser did not show any effect on the tensile strength. The tensile strength increases with time of immersion.
  • Ar. Davari, E. Ataei, H. Assarzadeh Pages 136-145
    The objective of this review is to inform practitioners about dentin hypersensitivity (DH); to provide a brief overview of the diagnosis, etiology and clinical management of dentin hypersensitivity and to discuss technical approaches to relieve sensitivity. This clinical information is described in the context of the underlying biology.The author used PUBMED to find relevant English-language literature published in the period 1999 to 2010. The author used combinations of the search terms “dentin*”, “tooth”, “teeth”, “hypersensit*”, “desensitiz*”. Abstracts and also full text articles to identify studies describing etiology, prevalence, clinical features, controlled clinical trials of treatments and relevant laboratory research on mechanisms of action were used.
  • A. Jafari, Sh. Najafi, F. Moradi, Mj. Kharazifard, Mr. Khami Pages 146-150
    Statement of Problem: Oral and pharyngeal cancer is one of the most mortal cancers; however, its quick diagnosis and referral is a crucial factor in enhancing the survival rate of the patients.
    Purpose
    The aim of this study was to inspect the referral conditions and the reasons for the delay in curing the patients referred to the educational hospitals in Tehran.
    Materials And Method
    In this retrospective -descriptive study, two hundred and fifty six files related to the oral and pharyngeal cancer were inspected. The documents were obtained from 5 educational hospitals specialized in the field of cancers. Eventually data related to the time difference between the first time of attending to lesion and diagnosing the cancer as patient’s delay and until the curing as professional’s delay were recorded.
    Results
    The majority of cancers were squamous cell carcinoma (SCC). The patient’s delay was recorded in 110 files among the whole files. The mean of the time between the patients’ first notice of the problem and the time visiting a primary care clinician was 270 days (range, 0-2520 days). The mean of the time from when the patient visited a primary- care clinician to the starting time of definitive treatment was 90 days (range, 0-270 days).
    Conclusion
    In this study, like other studies, SCC was the most common occurring cancer. Delays related to the patients were more than those related to the professionals. And at last, accuracy in recording the files and training the patients were recognized to be the most imperative factors to continue the treatment successfully.
  • N. Kargahi, M. Kalantari Pages 151-154
    Odontogenic keratocyst (OKC) is a common developmental odontogenic cyst affecting the maxillofacial region. Multiple OKCs are usually seen in association with nevoid basal cell carcinoma syndrome (NBCCS) but approximately 5% of patients with OKC have multiple cysts without concomitant syndromic presentation. This report represents a case of multiple OKCs in a non-syndromic patient.