Vol 3, No 3 (2006)
Proceeding Abstracts
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Statement of the problem: Various methods such as light emitting diode (LED) have been used to enhance the polymerization of resin-based orthodontic adhesives. There is a lack of information on the advantages and disadvantages of different light curing systems. Purpose: The aim of this study was to compare the effect of LED and halogen light curing systems on the shear bond strength of orthodontic brackets. Materials and Methods: Forty extracted human premolars were etched with 37% phosphoric acid and cleansed with water spray and air dried. The sealant was applied on the tooth surface and the brackets were bonded using Transbond adhesive (3M Unitek, Monrovia, Calif). Adhesives were cured for 40 and 20 seconds with halogen (Blue Light, APOZA, Taiwan) and LED (Blue dent, Smart, Yugoslavia) light-curing systems, respectively. Specimens were thermocycled 2500 times (from 5 to 55 C) and the shear bond strength of the adhesive system was evaluated with an Universal testing machine (Zwick GmbH, Ulm, Germany) at a crosshead speed of 1 mm/min until the brackets were detached from the tooth. Adhesive remnant index (ARI) scores were determined after bracket failure. The data were submitted to statistical analysis, using Mann-Whitney analysis and t-test. Results: No significant difference was found in bond strength between the LED and halogen groups (P=0.12). A significant difference was not observed in the adhesive remnant index scores between the two groups (P=0.97). Conclusion: Within the limitations of this in vitro study, the shear bond strength of resin-based orthodontic adhesives cured with a LED was statistically equivalent to those cured with a conventional halogen-based unit. LED light-curing units can be suggested for the polymerization of orthodontic bonding adhesives.
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Statement of Problem: It has been established that successful root canal treatment depends on the quality of obturation. Deeper penetration of spreaders can improve the apical seal and the quality of the obturation. Purpose: The aim of this study was to compare the initial penetration depth of spreaders during lateral condensation of 0.04 and 0.02 tapered gutta-percha master cones. Materials and Methods: In this study, sixty two freshly extracted single canal teeth were selected. The crowns were removed and the canals were prepared using the step-back technique. Patency of the apical foramens was maintained. The teeth were divided into 2 experimental groups of 31 teeth each. 0.02 and 0.04 tapered gutta-percha were inserted in the root canals of the first and second groups, respectively. A spreader was then placed next to the master cone and a digital scale was used to measure the force that was applied during spreader placement. An apical force of 1.5kg was employed to place the spreaders. The penetration depth was measured, subtracted from the working length, and recorded. Statistical analysis was performed using t-test. Results: The mean spreader penetration depth, recorded as distance from working length, was 2.16 (1.03) mm when using 0.02 tapered master cones and 3.52 (1.88) mm following insertion of 0.04 tapered master cones. The difference between the two penetration depths was statistically significant (P<0.01). Conclusion: The results of this study showed that the spreader penetration using 0.02 tapered master cones was significantly larger than the 0.04 master cones.
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Statement of problem: Recurrent aphthous stomatitis (RAS) is one of the most common diseases affecting human oral mucosa. The etiology of this disease remains unclear; therefore a definitive treatment has not yet been established and corticosteroids might be prescribed to reduce the symptoms associated with RAS. Purpose: The aim of this study was to determine the effects of a mouthwash containing 0.05% clobetasol and nystatin on aphthous ulcers. Materials and Methods: Forty patients with RAS, 18 males and 22 females with an age range of 11-50 years, participated in this double-blind placebo-controlled clinical trial. The subjects were randomly divided into two equal groups. Group A received a mouthwash containing 0.05% clobetasol and 100,000 IU/cc nystatin with instructions to rinse with 20 drops for 5 minutes, 3 times daily. Group B (control) received placebo and was asked to follow the same instructions. All symptoms along with possible adverse effects were measured and recorded during the 2-week study period. Statistical analysis was performed using chi-square and independent paired t-tests. Results: Complete resolution of the lesions and their symptoms was observed in 85% of the participants in group A. Two (10%) patients showed no response to treatment and the symptoms increased in 5% (1 patient). There were no measurable changes in pain or healing time of the ulcers in the control group. Conclusion: The use of the tested mouthwash was found to be a safe and efficacious treatment for RAS of the oral mucosa.
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Statement of problem: It is not known whether endochondral and intramembranous bones have distinct biological characteristics. Octacalcium Phosphate (OCP), a hydroxyapatite precursor, has been reported to stimulate bone formation after being implanted in parietal bone defects of rats. Purpose: The present study was designed to investigate the response of endochondral and intramembranous bones to OCP implantation and to compare their biological characteristics Materials and Methods: Full-thickness standardized trephine defects were made in rat tibiae and mandibles and synthetic OCP was implanted into the defects. The biologic response was examined histologically to identify bone and cartilage formation. Results: Both chondrogenesis and osteogenesis were initiated in the tibia, 1 week after implantation of OCP and most of the cartilage was replaced by bone at week 2. However, the mandible only showed osteogenesis in response to OCP implantation at week 2, and no cartilage formation was associated with the osteogenesis. Conclusions: According to the results obtained in the present study, endochondral and intramembranous bones exhibit different biological responses to OCP implantation in rats.
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Statement of problem: Periodontal disease (PD) has been linked to adverse cardiovascular events by unknown mechanisms. C-reactive protein (CRP) is a prognostic marker for cardiovascular disease, with reported elevated serum levels during PD. Purpose: The aim of the present study was to evaluate the association between PD and higher CRP levels in the serum of acute myocardial infarction (AMI) patients. Materials and Methods: In this cross-sectional study, periodontal examinations and CRP serum levels were measured in 51 Q-wave and non-Q-wave AMI patients. All assessments were made during index hospitalization and within 72 hours of symptom onset. The patients were divided into two groups based on the presence or absence of PD and were frequency matched for sex, body mass index, smoking and traditional risk factors of cardiovascular disease. Using t-test, the results were compared between the two groups. Results: The prevalence of PD was high in patients with AMI (70.5%). AMI cases who had PD, showed significantly (P<0.05) higher CRP levels (21.88 mg/l) than AMI patients without PD (9.26 mg/l). A positive relationship was observed between PD and serum CRP levels, and after matching all the potential confounders, PD emerged as a strong and independent predictor of elevated CRP levels. Conclusion: Under the limitations of this study, periodontal disease was found to be common in patients with AMI and was associated with an enhanced inflammatory response, expressed by higher CRP levels. The relationship between PD and CRP levels in AMI patients appears to be independent of other contributing factors.
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Statement of problem: The effectiveness of fluoride dentifrices in reducing dental caries is well documented. However, not all fluoride dentifrices are equally effective Purpose: The objective of this experimental study was to compare fluoride uptake from Pooneh pediatric toothpaste and an ADA-approved pediatric dentifrice, in sound enamel of primary teeth. Materials and Methods: In an in vitro randomized controlled trial, 20 sound primary canines were divided into 2 groups according to the experimental dentifrices. Each tooth was sectioned longitudinally into experimental and control halves. The test groups were treated with dentifrice slurries for 1 hour. All specimens were then suspended in 5ml artificial saliva for 24 hours at 37˚C and were etched twice for 30 seconds with a 1ml solution of 0.5M percholoric acid. Fluoride and calcium concentrations were measured by a potentiometer and an atomic absorption spectrophotometer, respectively. The collected data were analyzed using repeated measurement ANOVA and Tukey's test. Results: The mean fluoride concentrations in the Aqua fresh group (4098.44 and 3755.25 ppm in first and both layers respectively) were higher than Pooneh (first layer 2420.51 ppm and both layers 2242.73 ppm), and both were higher than the controls (P<0.05). No significant difference was observed between the control groups. The enamel thickness in Aqua fresh cases was less than the teeth treated with Pooneh (first layer 3.09 vs. 3.85 µm, both layers 4.98 vs. 6.09 µm) and both were less than the controls (P<0.05). There was no significant difference between the control groups. Conclusion: Fluoride uptake was lower in Pooneh pediatric toothpaste as compared to the tested ADA-approved dentifrice, but considerably higher than the control group.
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The presence of supernumerary teeth is not uncommon in the general population. They occur more frequently in patients with a family history of such teeth but it is rare to find multiple supernumeraries in individuals with no other associated disease or syndrome. There have been very few documented cases of bilateral maxillary and mandibular supernumeraries, distal to the third molars. Supernumerary teeth may affect the permanent dentition if not removed. A 24 year-old male with five distomolars and a complete dentition is presented.
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The fracture resistance of all-ceramic restorations is one of the major concerns in clinical applications of these materials. Before initiating a time-consuming and costly clinical investigation, an in vitro study can help to estimate the in vivo usability of a new dental material. Mechanical properties of all-ceramic materials are frequently evaluated to predict their clinical performance. Since the test methods have influences on the obtained results and mechanical behavior of ceramic materials, the differences between different methods and techniques should be well recognized. The aim of this review article was to briefly appraise mechanical test methods usually use to evaluate dental ceramic materials, and to discuss their clinical implication and limits in dentistry. The search was limited to PubMed and only available and the most relevant sources were included.
