JOURNAL OF DENTAL RESEARCH, DENTAL CLINICS, DENTAL PROSPECTS
Year:2011 | Volume:5 | Issue:3|Papers Count:8

Background and aims: In order to fabricate prostheses with high accuracy and durability, soldering techniques have been introduced to clinical dentistry. However, these prostheses always fail at their solder joints. The purpose of this study was to evaluate the effect of gap distance on the tensile strength of base metal solder joints.Materials and methods: Based on ADA/ISO 9693 specifications for tensile test, 40 specimens were fabricated from a Ni-Cr alloy and cut at the midpoint of 3-mm diameter bar and placed at desired positions by a specially designed device. The specimens were divided into four groups of 10 samples according to the desired solder gap distance: Group1: 0.1mm, Group2: 0.25mm, Group3: 0.5mm, and Group4: 0.75mm. After soldering, specimens were tested for tensile strength by a universal testing machine at a cross-head speed of 0.5mm/min with a preload of 10N.Results: The mean tensile strength values of the groups were 162, 307.8, 206.1 and 336.7 MPa, respectively. The group with 0.75-mm gap had the highest and the group with 0.1-mm gap had the lowest tensile strength. Bonferroni test showed that Group1 and Group4 had statistically different values (P=0.023), but the differences between other groups were not significant at a significance level of 0.05.Conclusion: There was no direct relationship between increasing soldering gap distance and tensile strength of the solder joints.

Background and aims: Marginal seal of the material is extremely important in fissure sealant therapy. The aim of this study was to investigate microleakage of flowable composite resins and conventional fissure sealants with or without dentin bonding agent.Materials and methods: The occlusal surface of 60 intact extracted human premolars, divided into four groups, were cleaned with pumice/slurry, etched with 37% phosphoric acid for 15 seconds, rinsed and dried. Groups were treated differ-ently: Excite bonding agent followed by Helioseal F fissure sealant in group1, Helioseal F alone in group 2, Excite bonding agent followed by Tetric Flow in group 3, and Tetric Flow alone in group 4. Light-curing was done after each application. After thermocycling, the whole surface of each specimen was coated with nail varnish except for one millimeter around the fissure sealant. The teeth were immersed in 2% basic fuchsin for 24 hours and then sectioned buccolingually. The sections were analyzed for leakage under a stereomicroscope. Data was analyzed by Kruskal-Wallis and Mann-Whitney tests at a significance level of P<0.05.Results: There were no statistically significant differences between the study groups in terms of the mean microleakage scores (P>0.05), except for groups 2 and 4 (P=0.002) and groups 3 and 4 (P=0.033).Conclusion: Use of a flowable composite with bonding agent is a good alternative for sealing pits and fissures, however, further in vitro and in vivo studies are necessary.

Background and aims: The purpose of this investigation was to assess the placement and replacement of resin-based composite restorations and related factors in a private practice in Greece.Materials and methods: The study included 1500 subjects, 720 males and 780 females, aged 18 to 52 years old. The clinical examination involved calculation of the number of teeth with primary caries and failed-restored teeth. In addition the relationship between placed and replaced composite restorations and the following aspects was assessed: gender, cavity type, tooth type and evaluation of longevity of the replaced composite restorations. Statistical analysis performed using the chi-square test. A p value less than 5% was considered statistically significant.Results: The total number of restorations placed were 1940, 1202 of those (62%) were placed for first time while 738 (38%) were replaced. The main reason for the placement of new composite resin restorations was primary caries (60%), while secondary caries was the most frequent reason for the replacement (48%) of those. A statistically significant difference was recorded between males and females regarding the composite restorations placed and replaced (p=0.00082), the type of cavity of placed restorations (p=0.00062), and the type of cavity of replaced ones (p=0.00038). The median longevity of the replaced resin composite restorations was approximately 4 years (47%).Conclusion: Dental caries, primary and secondary, followed by tooth discoloration and loss of filling were the main reasons for placed and replaced composite restorations.

Background and aims: Bacterial contamination of dental unit water supplies (DUWS) has attracted a lot of attention in recent years due to the emergence of serious infections in susceptible dental patients. The aim of the present study was to evaluate the presence of gram-negative bacterial contamination in DUWS at Tabriz University of Medical Sciences Faculty of Dentistry.Materials and methods: This descriptive study was carried out on 51 active dental units in different departments. Contamination was determined by taking samples from the unit's water supply before dental procedures and the use of specific culture media. The cultures were evaluated after 48 hours.Results: Gram-negative bacterial contamination was identical in all the departments. In the departments on the ground floor, namely Departments of Periodontics and Oral and Maxillofacial Surgery, Pseudomonas contamination was observed in 71% of units, in the departments on the first floor, namely Departments of Prosthodontics, Orthodontics and Pedodontics, 46.8% of the units had Pseudomonas contamination, and in the departments on the second floor, namely Departments of Operative Dentistry and Endodontics, 37.7% of the units demonstrated Pseudomonas contamination.Conclusion: Gram-negative bacterial contamination was evident in the evaluated DUWS. The contamination type was identical but the number of contaminated units decreased with the increase in the height of the floors.

Background and aims: Well-differentiated chondrosarcoma and enchondroma are similar in histopathologic aspects, therefore, special methods should be used to make a distinction between these benign and malignant tumors. The aim of this study was to evaluate the efficacy of a histopathologic method in the long-term follow-up for differentiating these lesions.Materials and methods: The medical records of patients with histopathologic diagnosis of chondrosarcoma and enchondroma were retrieved from the Institute of Cancer, Department of Pathology from 1981 to 2007 in this retrospective study. A total of 14 patients with chondrosarcoma and 7 patients with enchondroma were included. Tumor lobulation pat-tern and fibrous tissue around the lesions were used for histopathologic differentiation between well-differentiated chondrosarcoma and enchondroma. Method accuracy was evaluated by tumor recurrence in the long-term follow-up.Results: In the well-differentiated chondrosarcoma group, the follow-up period was 97 months. All the patients (100%) experienced recurrence. In the enchondroma group, the follow-up period was 129 months. There was no recurrence in this group.Conclusion: Lobulation pattern and fibrous tissue formation around the tumor can be an effective and helpful indicator for histopathologic differentiation between enchondroma and well-differentiated chondrosarcoma.

Osteomyelitis is an inflammatory infectious condition of bones, occurring either acutely or chronically. The clinical course of the disease leads to destructive or sclerosing patterns of the involved bone. This report presents a case of chronic focal sclerosing osteomyelitis in a 19-year-old male with a history of an uncontrolled convulsive condition. The lesion was first diagnosed as an osteoblastoma. Chronic trauma or traumatic occlusion has the potential to induce osteomyelitis and should be considered a possible diagnosis in differentiating periapical radiopacities, even in relation with vital teeth.

In the article entitled "Two-year prevalence of minor aphtha in Tabriz, Northwest Iran" which was published in the winter issue of the third volume of the journal, a 0.3% prevalence rate for minor recur-rent aphthous stomatitis (RAS) was reported.1 We attempted to continue studying the archives of Tabriz University of Medical Sciences Faculty of Dentistry until June 2008, to allow for a consecutive 15000 records. In addition, the clear influence of involved factors in minor RAS was also assessed. The same methods were used in the assessments. Since the re-sponse variable of RAS is assumed to be categorical with two response levels, Yes and No, chi-square test was used to determine statistical association of lesions prevalence with gender, age decade, familial involvement, and cigarette smoking. Furthermore, logistic regression model was adapted to investigate the aggregate relationship of RAS with four independent covariates, gender, age decade, family his-tory, and cigarette smoking using stepwise selection method by SAS software (1998, SAS institute, Inc., Cary, USA). The confounding effect of gender was analyzed later by multivariate analysis to minimize selection bias...

We attempted to evaluate the researchers' behavior in using scientific resources in the Faculty of Dentistry at Tabriz University of Medical Sciences. The importance of such study is high-lighted when financial resources are limited and the scholarly publications are on an ever-increasing rate, necessitating the selection of the most efficient re-sources for the libraries. In Iran, 80.5% of the university central libraries depend on the policies of Ministry of Health and Medical Education for subscription to periodical publications on medical sci-ences.1 Since libraries serve as connection routes between previous knowledge and new information, their organizational needs should be analyzed by means of scientific methods as well as quantitative and statistical approaches...