Journal of Dental School
Year:2010 | Volume:28 | Issue:1 (83)|Papers Count:10

Background and Aim: With the increase of laser application in different fields of dentistry, further research is required to evaluate its efficiency in dental therapy. This study evaluated the effect of Er,Cr:YSGG laser conditioning of enamel on micro shear bond strength of composite resin of human enamel following two different tooth preparation methods (Diamond disk versus Er,Cr:YSGG laser).Materials & Methods: In this invitro study, 125 human third molars were randomly assigned into 5 groups. Buccal and lingual enamel slices were prepared as below: A) laser-ablated without etching, B) laser-ablated and laser-etched, C) laser-ablated and acid-etched, D) cut by diamond disk and laser-etched and E) cut by diamond disk and acidetched. Tubs of Z100 composite resin (3M, Dental Product/ USA) were bonded to conditioned enamel surfaces after applying two layers of Single Bond (3M ESPE, Dental product! USA) Shear bond strength was measured by Micro- Tensile tester (Bisco Inc/USA) at a cross-head speed of 0.5 mm/min. Data were analyzed by one-way ANOV A, and Tukey tests.Results: Mean shear bond strengths in groups were: A=23.14±6.53 MPa, B=23.77±5.56MPa, C=23.5±4.89MPa, D=19.30±5.56MPa and E=28.99±6.40 MPa respectively. The differences between (E,A), (E,B), (D,B), (C,D) and (D,E) were significant (P<0.05).Conclusion: Micro shear bond strength of groups prepared by diamond disk and acid-etched were higher than groups prepared and etched by Er,Cr:YSGG laser. Therefore, re-etching with acid phosphoric is necessary if laser is used for tooth preparation or etching. Etching with acid phosphoric is recommended when laser is to used for tooth preparation or etching.

Background and Aim: Presence of Haller cells with or without disease can narrow the ethmoid infundibulum or ostium of maxillary antrum and result in persistent rhinosinusitis, recurrent sinusitis, and other clinical symptoms, so detection ofhaller cells in common panoramic radiographs can be useful in diagnosis of the origin of these problems. The purpose of the present study was to determine the prevalence of infraorbital ethmoid cells on panoramic radiographs.Methods and Subjects: Panoramic radiographs of 310 patients were evaluated according to the method of Ahmad et al. to detect infraorbital ethmoid cells. A well defined radiolucency was located medial to infraorbital foramen, wherever most of its border was visible and caused lack of cortication in inferior border of the orbit in the superimposition areas, was interpreted as infraorbital ethmoid cell. The radiographs were interpreted by three observers. the data were analyzed by Binary logistic regression test in SPSS software. Results: Data from 310 panoramic radiographs were analyzed. 37% of radiographs were interpreted as to show infraorbital ethmoid cells.Conclusion: Infraorbital ethmoid cell might be considered as a quite common anatomic landmark, visible on panoramic radiographs. From a clinical point of view, this may be of diagnostic importance, because it has been stated that detection of haller cells may lead to detection of the origin of a number of sinus problems.

Background and Aim: The present study aimed at determination of the fatigue resistance and failure mode of cuspreplacing onlays in endodontically treated premolars using indirect composite resin restorations. Materials and Method: In this experimental study, 84 human premolars were randomly divided into 7 groups of 12. These groups were prepared as follows: Intact teeth used in groupl as control, the second group covers the endodontically treated teeth, restored with indirect onlays using Z-250 composite resin, the next two groups (i.e. 3,4) were similar to the second group, but subjected to 1 and 2 million fatigue load cycles, respectively. Groups 5, 6, 7 were similar to groups 2, 3, 4, respectively, however, in these groups Tetric Ceram used as the restorative material. All specimens were loaded using a Universal Testing Machine until fracture occurred and the mode of failure observed with naked eye. Kruskal-Wallis and Chi-Square tests were used to analyze the data (a=.05). Results: All specimens withstood the masticating simulation. The mean fracture strength for groups 1 to 7 were: 1276.92, 1269.05, 1217.80, 1188.13, 1228.97, 1127.86, 1105.58, respectively. No statistically significant differences were found between the groups in fracture strength and failure mode. There was no statistically significant difference between two types of resin composite (P=0.203) and load cycles (P=0.298) after zero, 4 and 8 years aging. Conclusion: Within the limitation of this study, restored premolars with indirect composite onlays show fatigue resistance equal to natural tooth up to 8 years after restoration. Furthermore, no statistically significant differences were found between 4 and 8 years of load cycles. Tetric Ceram Z-250 restoration agent showed no effect on the tooth fracture resistance with the most observed fractures to be occur under CEJ with no capability to be restored.

Background and Aim: The effect of smear layer on dentinal tubules is remarkable in endodontic treatments. The aim of this study was measuring the range of dye penetration in dentinal tubules with and without smear layer. Materials & Methods: Thirty extracted human teeth used in this study. At first, segments e prepared with 5 mm length from each tooth's root and then their canals widened by a 1/4mm diameter bur, so that the smear layer appeared. The external, superior and inferior surfaces of the segments covered by 2 layers of nail varnish. The segments divided to 2 groups of 15 samples. The first group samples immersed in 17%EDTA for 2 minutes and then in 5.25% NaOCl for 20 minutes to remove the smear layer. After that the samples immersed in 2% basic fushin for 24 hours, the second group samples immersed in 2% basic fushin without removing the smear layer. After water rinse, all samples sectioned horizontally from middle of the root and photographs was taken of each samples surfaces. After transmitting the photographs to a computer, the percentage of the dye penetration into dentinal tubules of each sample calculated by Photoshop software.Results: Due to results, the range of dye penetration in dentine tubules of the teeth with and without smear layer had no statistically significant difference (P-Value=0.120).Conclusion: According to the result, smear layer removal have no effect on dentin permeability to dye penetration and dentin sclerosis is an important factor in this subject. Performing studies on the teeth with certain age and using other methods such as microbial permeability evaluation are needed.

Background and Aim: Choosing appropriate disinfectants has become confusing for many dental professionals because of exaggerated manufacturer claims and misleading assays reported in the literature. Dentists should be aware of guidelines that assist in the selection of appropriate chemicals. To evaluate the level of knowledge and attitude of General Dental Practitioners (GDP) who work in private clinics in the Great Tehran in 2006 about chemical disinfectants.Methods and Materials: This study was a cross-sectional descriptive study. 446 GDPs (317 (71.1%) male, 129 (28.9%) female) were selected by a random cluster sampling method and evaluated by using a questionnaire consisting of 20 knowledge and 14 attitude questions content validity was confirmed by 4 specialists in oral medicine and 6 general practitioners. Spearman-Brown's reliability for the questionnaire was 0.66. Chi-square test and SPSS -9 software were used for statistical analysis. Results: The mean correct answers were 8.6±3.0 (95% Cl: 8.3 to 8.9, ranged from 2 to 17) of maximum 20. Using multilinear regression fonnula showed that only age had negative relation with correct answers. The most difficult question was concerned with provision of and of particulars.Conclusion: Knowledge level of GDPs about chemical Disinfection was low. It seems that traditional educational methods should be changed to new methods (Reform). 60.5% of the population was keep to receive. Information from programs and 46% wished to use educational leaflets.

Background and Aim: Regarding the importance and prevalence of lichen planus among patients and rarity of Oro- Vulval-Vaginal and Peno-Gingival syndromes, that need more attention for diagnosis because of simultaneous oral and genital involvement, we are going to review the symptoms and early diagnosis of these patients. The aim of this article is to report two patients with Oro-Vulval-Vaginal syndrome and two patients with Peno- Gingival syndrome with a short review on these syndromes and their treatments. Case Report: This study is a case report four patients with these syndromes who attended oral medicine department. For each patient a complete document consisting of demographic information, medical, dental, familial and social history was prepared and a photograph was taken from the oral lesions at the first visit and for definite diagnosis of genital lesions consultation with Dermatologist and OB &GYN Surgeon was done. After biopsy and definite diagnosis simultaneous treatment for oral and genital lesions started.Regarding the severity of lesions and acceptable response to the primary treatment, type and dose of the drug was changed and finally the patients were placed in follow up phase.Conclusion: Regarding the outcome of neglecting Lichen Planus in other organs and delay in accurate diagnosis and lack of receiving enough and on time treatment, performing an exact examination and taking a complete history with attention to other organ's symptoms is of great importance. More over malignant changes in even asymptomatic oral and genital lesions is probable.

Background and Aim: Since early 1990's, internet has been used to train medical and dental students and practitioners. The aim of this study was to evaluate attitudes and believes of dental students and academic staffs towards internet usage in dental training in Shahid Beheshti University of Medical Sciences.Methods and Materials: In this cross-sectional study, 305 dental students and 79 academic staffs were evaluated. The questionnaire consisted of some questions to record the demographic data, along with 14 close-ended 3 open-ended and 1 composed questions. The scales of questions were nominal or ordinal, as indicated. Results: Ninety-two percent of students had access to computer and 93.4% to internet. These rates were 98.7% and 97.5% respectively among academic staff. Both groups frequently accessed the internet at university and home. Only 15.1% of students and 6.3% of academic staff were unsatisfied regarding the accuracy of information on the internet about dentistry. The academic staffs were believed more strongly in favor of the possible usefulness of access to lecture notes on the dental school website than students. Nevertheless this group more strongly believed that this possibility may reduce student attendance at lecture.Conclusion: Access rate to internet is satisfactory among both dental students and their teachers. Also, both groups had relatively positive attitude towards using internet for dental training.

Background & Aim: This survey has been done to show the rate of using Vancouver style as bibliographies presented in doctoral theses and post graduate theses of dentistry in Shahid Beheshti University of medical science between 2004-2009. Purpose of the research is to study usage rate of Vancouver style in bibliographies of doctoral theses of dentistry in Shahid Beheshti University of Medical Sciences between 2004-2009.Method &Materials: Present information within theses was gathered, compared and analyzed with Vancouver style, having used descriptive surveying research method. Target community has been selected from among doctoral theses and specialized doctoral theses of dental school in Shahid Beheshti University of Medical Science between 2004 till 2009, with course stratified random sampling, so that we were chosen among 463 doctoral theses, 132 theses, and among 155 post graduate doctoral theses, were chosen 50, therefore, total 192 theses had chosen. Results: The research results indicated that rate of Vancouver style in bibliographies in target community, is lower than medium level and Vancouver style in bibliographies have not been signification in theses.Conclusion: The results of the present study showed inadequate knowledge of correct referencing suggesting more stresses to be paid on the standardized Vancouver reference system.