Vol 9, No 4 (2012)
Proceeding Abstracts
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Most published results about the characteristics of NiTi wires are based on the mechanical laboratory tests on the as-received wires.The purpose of this study was to investigate the effect of saliva on load-deflection characteristics of superelastic NiTi wires.In this experimental study, 15 wires of three kinds of superelastic NiTi wires (Sentalloy, Force I and Truflex) were prepared. Five specimens of each wire were tested in the as-received condition (T0) to provide baseline information and the remaining wires were divided into two groups of five. Half of them were kept inside artificial saliva for one month (T1), while the others were kept in air (T2). After 30 days, three-point bending test was done in a dental arch model and data from selected points on the unloading phase of the generated graphs were used for statistical analysis.Force I and Truflex showed significantly greater force than Sentalloy. The load values of Truflex and Force I after one month exposed to artificial saliva (T1) decreased significantly, but Sentalloy was not affected significantly. The plateau gap values were not considerably different among T0, T1 and T2.Saliva decreased the load of Force I and Truflex significantly, but it did not have a statistically significant effect on Sentalloy.
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This study aimed to evaluate the cellular toxicity of two newly-released acrylic resins (Futura Gen and GC Reline Hard) in comparison with the conventional heat-cure resin (Meliodent).Sample discs from each acrylic resin were placed in 24-well culture plates along with L929 mouse fibroblast cell line. A mixture of the RPMI 1640 medium, antibiotics and 10% FBS was added to the plates and the specimens were incubated in a CO(2) incubator. The amount of light absorption by each plate was determined after 1 hour, 24 hours and 1 week by the MTT assay and ELISA. The cytotoxic effect of the resins was compared among groups using the two-way ANOVA and further paired comparison was performed using the post-hoc Tukey's test.After 1 hour, Futura Gen displayed a significantly lower level of light absorption in comparison with Meliodent (P=0.03). After 24 hours, GC Reline Hard rendered a significantly lower level of light absorption compared to Meliodent (P=0.02). After one-week of incubation, the mean absorption rates for GC Reline Hard, Meliodent and Futura Gen were relatively similar (P>0.05). The lowest and highest level of cytotoxicity among all resins were observed after one week and 1 hour of immersion in water, respectively.All the tested resins induced some degree of cytotoxicity. Cytotoxicity of Futura Gen, GC Reline Hard and Meliodent resins failed to show any significant reduction from 24 hours to one week. Thus, it is recommended to immerse the dentures in water for 24 hours prior to delivery to the patient.
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To investigate attitudes of Iranian senior dental students towards preventive dentistry in relation to their background factors and self-perceived competency in providing preventive care.In spring 2008, a questionnaire survey was conducted with all the senior dental students of seven randomly selected state dental schools in Iran. In addition to the respondents' age and gender, the voluntary questionnaire assessed the students' attitudes towards preventive dentistry by means of a seven-point semantic differential scale of nine qualities and their opposites, and their self-perceived competency in providing preventive care by five separate questions. To identify the underlying dimensions for attitude, a factor analysis with principle component method and varimax rotation was applied. Independent sample t-test served for statistical analysis. Of the 242 students receiving the questionnaire, 182 students (75%) responded. The mean age of the participants was 26 years and 42% of them were men.Based on the factor analysis, which explained 60% of the total variance, two attitude dimensions were identified; the profession-related dimension and the health service-related dimension. Competency in giving preventive care in all the five specified areas was reported by 44% of the students with no significant gender differences. The mean for the dentist-related dimension was significantly higher among the students who reported competency in giving preventive care (P=0.005).There is room for improvement in senior dental students' attitudes towards preventive dentistry. In order to create more positive attitudes for future dental professionals, there should be an early and sufficient exposure to preventive aspects of dentistry in the dental curricula.
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The aim of this study was to determine the effect of trenched zirconia bar on the von Mises stress distribution of IPS -Empress II core ceramics.The three-dimensional model including a three-unit bridge from the second premolar to the second molar was designed. The model was reinforced with zirconia bar (ZB), zirconia bar with vertical trench (VZB) and zirconia bar with horizontal trench (HZB) (cross sections of these bars were circular). The model without zirconia bar was designed as the control. The bridges were loaded by 200 N and 500 N on the occlusal surface at the middle of the pontic component and von Mises stresses were evaluated along a defined path.IN THE CONNECTOR AREA, VON MISES STRESS IN MPA WERE APPROXIMATELY IDENTICAL IN THE SPECIMENS WITH ZB (AT MOLAR CONNECTOR (MC): 4.75 and at premolar connector (PC): 6.40) and without ZB (MC: 5.50, PC: 6.68), and considerable differences were not recognized. Whereas, Von-Mises stress (MPa) in the specimens with horizontal trenched Zirconia bar (HZB) (MC: 3.91, PC: 2.44) and Vertical trenched Zirconia bar (VZB) (MC: 2.53, PC: 2.56) was decreased considerably.Embeded trenched zirconia bar could reinforce IPS-Empress II at the connector area which is a main failure region in all ceramic fixed partial dentures.
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An ideal orthodontic force system should exert continuous light force. Thus, many efforts have been made to improve the memory characteristics of elastomeric chains. The aim of this study was to compare elastomeric chains (ECs) claimed by their manufacturers to offer high memory with traditional ones according to their force-extension diagrams.In this in-vitro study, ECs were divided into six groups, each containing 40 pieces of chain, from three brands (American Orthodontics, GAC and Ortho-Technology). Each brand was divided into two groups with respect to their claimed characteristics (with or without memory). Each sample was stretched to twice its original length and kept constant in 37°C distilled water. Force-extension diagrams were drawn by universal testing machine at 0,1,8,24,72 hours and 1, 2, 4-week intervals. Additionally, the amounts of elongation required to deliver 200 g force were calculated. To compare the results, ANOVA and Tukey tests were performed.Force-decay rate was significantly different between traditional and memory chains (p<0.05). For traditional chains, there was a substantial decay in force in the first hour and 30-40% of the force was retained at 4 weeeks. The memory chains demonstrated more constant force and retained 60% of the force. The maximum amount of elongation required to deliver 200 g force belonged to American Orthodontics memory chains (61.9% after 24hr) and the minimum to Ortho-Technology ECs (23.4% initially).Memory chains exhibited superior mechanical properties compared to traditional ones. For delivering the same force, memory chains required more elongation. Memory chains of GAC and American Orthodontics showed better characteristics among all chains.
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Dental caries, periodontitis and other mucosal diseases are caused by a complex community of microorganisms. This study aimed to investigate the antimicrobial properties of saponins of four important oil yielding medicinal plant extracts on selected oral pathogens that are involved in such diseases.Saponins were extracted from Bauhinia purpurea, Madhuca longifolia, Celastrus paniculatus and Semecarpus anacardium and purified. Antimicrobial properties of these saponins against Streptococcus mutans, Streptococcus mitis, Streptococcus salivarius, Staphylococcus aureus and Lactobacillus acidophilus were determined using well diffusion method. The minimum inhibitory concentration (MIC) was determined as the lowest concentration of saponins inhibiting bacterial growth after 14 h of incubation at 37°C. The bactericidal activity was evaluated using the viable cell count method.The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Madhuca longifolia saponin on Streptococcus mutans MTCC 890, Streptococcus mitis and Staphylococcus aureus was 18.3 ± 0.15/34.4 ± 0.24 μg/ml, 19.0 ± 0.05/32.2 ± 0.0 μg/ml and 21.2 ± 0.35/39.0 ± 0.30 μg/ml, respectively and Bauhinia purpurea saponin on Streptococcus mutans MTCC 890, Staphylococcus aureus and Lactobacillus acidophilus was 26.4 ± 0.20/43.0 ± 0.40 μg/ml, 29.0 ± 0.30/39.6 ± 0.12 μg/ml and 20.2 ± 0.05/36.8 ± 0.23 μg/ml, respectively.The strong antimicrobial activity of Madhuca longifolia and Bauhinia purpurea may be due to the presence of complex triterpenoid saponins, oleanane type triterpenoid glycosides or atypical pentacyclic triterpenoid saponin. Hence, these extracted saponins may be used in food and oral products to prevent and control oral diseases.
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The aim of this study was to analyze the impact of green tea on dentin erosion.Twelve extracted sound human premolars were immersed in Coca Cola with a pH of 2.8 for 5 minutes. The surface microhardness was measured with a Knoop diamond under a load of 50gr/10s. The teeth were immersed in green tea (Camellia sinensis) solution for one minute. The microhardness values were measured again and compared with pretreatment values by the Wilcoxon test. Three eroded teeth, which were treated with green tea, were evaluated under scanning electron microscope.The mean ± SD of microhardness values before and after immersion in green tea were 46.5±2.79 and 54.5±4.4, respectively with statistically significant differences between the two measurements (P<0.01). In SEM evaluation there was an improvement in eroded dentin appearance and there were deposits on the dentin surface.Green tea (Camellia sinensis) increased the microhardness of eroded dentin and improved the eroded texture.
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Atraumatic Restorative Treatment (ART) is a minimal intervention technique in the management of carious lesions, which results in negligible discomfort to the patient. The aim of this study was to assess and compare the discomfort levels during Atraumatic Restorative Treatment and Minimal Cavity Preparation (MCP: a method using rotary instruments) treatment procedures in a sample of school children in Davangere city.An experimental study was performed aimed at comparing discomfort levels as measured by subjective (Venham index) and objective (Heart rate) methods at six specified moments during the treatment. A total of 200 children were randomly divided into two groups of 100 each. In each child, one class II restoration with GIC in a deciduous molar was performed. One group received treatment using rotary instruments (MCP) and the other group with ART. Discomfort levels were measured using Venham index (behavioural dimension) and heart rate (physiological dimension).The behavioural measurement revealed that in ART group the majority of the children(64%) showed an overall Venham score of '<1'(relaxed) as compared to MCP group in which the majority of children (76%) showed a Venham score of '1'(uneasy). The physiological measurement revealed that the children in ART group experienced less discomfort when compared to children in MCP group.The results of the study suggest that ART induces less discomfort; is patient friendly and has a higher extent of community acceptance when compared to MCP.
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Low-intensity laser therapy (LILT) is defined to supply direct biostimulative light energy to the cells. While several studies have demonstrated that LILT has stimulating effects on bone cells and can accelerate the repair process of the bone, others reported delayed fracture healing or no effects after LILT. The aim of this article was to review the studies evaluating the biomodulation effects of LILT on bone-derived stem cells.To access relevant articles, searching in three electronic databases including PubMed, Google Scholar and Science Direct was conducted until April 2012. The key words used were low-level laser, low-intensity laser, low-power laser therapy, stem cell, bone marrow stem cell, bone and osteoblast. The articles that met the eligibility criteria were included in this review of literature.Twenty-five relevant articles (13 in vitro and 12 animal studies) were included. Eleven in vitro studies showed positive results with regard to acceleration of cell proliferation and differentiation. All animal studies showed improved bone healing in sites irradiated with low-intensity laser.Based on the results of the reviewed articles, low intensity laser therapy can accelerate bone healing in extraction sites, bone fracture defects and distraction osteogenesis, provided proper parameters were applied.
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The aim of this study was to investigate the reproducibility of natural head position (NHP) at different times of the day and to compare the reproducibility of the initial photographs with 6-month repeat photographs.The participants in this prospective study were seventy 14 to 50-year-old individuals. Each participant was photographed with a digital camera twice, at three different times of the day (in the morning, at noon and in the evening) and after a 6-month interval. The reproducibility of head posture was assessed by comparing the angle between the true horizontal and the ala-tragus plane. Student's paired t-test and repeated measure analysis were used to analyze the results. To evaluate the differences between the first and second sets of photographs, Dahlberg's coefficient (method error) was also used.Repeated measure analysis did not reveal any statistically significant differences in NHP orientation at different times of the day in the initial measurements (p=0.15) or after a 6-month period (p=0.56). Dahlberg's coefficient for all the participants during the 6-month period was 3.14°. Paired t test showed significant differences in NHP orientation only in the morning.The time of the day during which the photograph is taken does not affect the reproducibility of NHP. However, this orientation was more stable in the evening and at noon than in the morning. No differences were found between genders. In conclusion, measurements of NHP with the ala-tragus plane were more stable than measurements based on intracranial reference planes.
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Osteoporosis is a skeletal disease characterized by reduction in bone mass and micro architectural changes in the bone, which leads to increased bone fragility. The gold standard for the diagnosis of osteoporosis is the measurement of bone mineral density (BMD) by dual energy x-ray absorptiometry (DXA). Periodontal disease is a chronic destructive disease which can occur in adults, young people and children. Periodontal pathogens cause inflammation of the gingiva which is called gingivitis. When periodontal tissue destruction and alveolar bone loss happen, it is called periodontitis. Since both osteoporosis and periodontal diseases are bone destructive diseases, it has been hypothesized that osteoporosis could be a risk factor for the progression of periodontal disease. The aim of this study is to review the articles assessing the relationship between osteoporosis and periodontitisIn this review, articles were selected from PubMed between January of 1998 and June 2010. Amongst 508 articles identified from the electronic search, 17 articles were selected for a full-text reading based on the inclusion and exclusion criteria.Among the 17 studies focused on, 11 studies showed a positive relation between osteoporosis and periodontal disease and the six remaining studies found no significant relation between osteoporosis and periodontal disease.These data indicate a greater propensity to lose alveolar bone in subjects with osteoporosis, especially in subjects with preexisting periodontitis. This would indicate that osteoporosis or low systemic BMD should be considered a risk factor for periodontal disease progression.
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The lateral periodontal cyst is an uncommon, but well-recognized type of developmental odontogenic cyst. Lateral periodontal cysts are defined as non-keratinized and non-inflammatory developmental cysts located adjacent or lateral to the root of a vital tooth. It is a relatively uncommon lesion found mostly in adults (5th to 7th decades) and it is rare in young people under 30 years of age. A common site of occurrence is the mandibular premolar region. It does not have a predilection for any race or sex. Histopathologically, the lateral periodontal cyst lining is characterized by a thin cuboidal to stratified squamous non-keratinizing epithelium, ranging from one to five cell layers and presence of one or more epithelial thickenings or plaques.The purpose of this article is to report a case of interradicular radiolucent cystic lesion in a thirteen-year-old girl, located in a rare site of the maxillary premolar area, mimicking clinical and radiographical features of a residual cyst, but histopathologically proven to be a lateral periodontal cyst.
