Vol 1, No 1 (2004)
Proceeding Abstracts
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Statement of Problem: Biomechanics of the human dentition is inherently complex. Purpose: The aim of this study is to investigate, in vitro, the creep and the recovery of dentin under static uniaxial compressive stress conditions. Materials and Methods: Specimens of cylindrical morphology were prepared from recently extracted non-carious lower molar teeth, such that the average tubule orientation was axial. Slides of mid- coronal dentin (parallel surfaces, height 1.8 mm) were sectioned with a slow speed diamond saw and then cut into cylindrical discs. Specimens were stored at 4ºC for 24h to restabilize water content. Creep data were then measured by LVDT axially in water for periods of 2h load + 2h recovery on 4 separate groups (n=6): at two stresses (10 & 18 MPa) and at two temperatures: 37 & 60ºC. Maximum creep strain, permanent set, strain recovery and initial compressive modulus were reported. Results: Compliance values were also calculated and slight non-linearity found at 60ºC. Two-way ANOVA was performed on results. Dentin exhibited a linear viscoelastic response under 'clinical' compressive stress levels, with a maximum strain ~ 1% and high recoverability: permanent set<0.3%. Conclusion: This established a performance standard for viscoelastic stability of restorative biomaterials, replacing human dentin.
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Statement of Problem: Papillon Lefevre syndrome (PLS) is a rate autosomal recessive disorder, which is characterized by palmar- plantar hyperkeratosis and rapid periodontal destruction of primary and permanent dentitions. Purpose: The aim of the present study was to evaluate the peripheral blood neutrophil function including random locomotion, chemotaxis and oxidative mechanism of killing in a group of patients with PLS. Materials and Methods: Peripheral blood was obtained from 8 PLS patients and 92 healthy control subjects. PMN mobility was measured by a modification of the micromethod of Addison and Babbage. Latex-Stimulated NBT reduction test described by Park et al was followed. Data were analyzed by Mann Whitney U test. Results: The chemotactic activity in the PLS group was significantly lower than control group (89.5±21.6 vs 113±16 m, P<0.002). The rate of NBT reduction by PLS patients leukocytes was 50.614.9% in comparison with the control group (52.216.1%). The patients group showed a random locomotion rate of 46.510.4 m. This value for the control group was 43.913.6 m. Both oxidative mechanism of killing and random location were not significantly different from those of the healthy control subjects (P>0.05). Conclusion: The present study indicated an impaired neutrophil chemotaxis in PLS patients.
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Statement of Problem: Nowadays, evaluation of the development of occlusion in deciduous teeth for creating corrective occlusion in permanent teeth is one of the most important objectives of pediatric dentistry. In other countries, a vast number of researches have been accomplished on the details of occlusion in deciduous teeth. But, unfortunately, there is still no accurate information about this in IRAN. Purpose: The aim of this study was to evaluate the occlusion and interdental spaces of kindergarten children of Tehran. Materials and Methods: On this basis, some information were gathered by means of a cross-sectional, descriptive, analytic study on 248 children during their 4-5 years of age. All kinds of deciduous molar and canine occlusion were studied and registered. Anterior and posterior interdental spaces by means of a gauge with an accuracy of 0.05 mm were also measured. Collected data was analyzed by t-student and variance analysis. Results: In most children, the facial feature was mesoencephalic and the profile was convex. The incidence of occlusion was Fluch Terminal Plane (FTP), Distal Step (DS) and Mesial Step (MS), respectively. There was a statistical significant relationship between the FTP, DS and MS molar occlusion and the occlusion of Class I, II and III canine (P<0.05). The prevalence of maxillary and mandibular primate spaces were 95% and 90% respectively, without significant difference between the two sexes. The anterior and posterior interdental spaces in maxilla were more than in mandible without significant difference in two sexes. There wasn’t also a significant difference between the occlusion of deciduous molars and mandibular anterior dental spaces, maxillary and mandibular posterior dental spaces and the maxillary and mandibular primate spaces. Conclusion: Meanwhile, there was a significant difference between the occlusion of deciduous molars and the maxillary anterior dental spaces (P<0.05). The maxillary anterior interdental space was less the others in bilateral distal step occlusion.
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Statement of Problem: Esthetic materials undergo some physical and mechanical changes, during their service in oral cavity. Purpose: The aim of this study was the evaluation of the color and opacity stability of Ideal Makoo (IDM) composites and compare it with Tetric ceram. Material and methods: Fifteen disk shaped samples of each material was divided into three groups of five. Different aging treatments were applied to each group. The contrast ratio of 1mm thickness and E of the samples were evaluated at base line and after aging, using CIE system and Data Flash spectrophotometer. All the samples were kept at 37C. Results: Baseline opacity of IDM was relatively high (77.60%8.6). Both materials showed increased opacity after aging. The highest E belonged to IDM samples of B group, which was significantly more than Tetric Ceram (P<0.05). Tetric Ceram, also showed some degree of color change (E=4.60 and 5.79, on black and white background, respectively), which is noticeable clinically. Conclusion: The research showed that IDM can not be a reliable esthetic material, unless some improvements in the chemical composition will be achieved.
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Statement of Problem: In recent years, numerous reports have been presented in the literature, about gingival overgrowth induced by Nifedipine- a calcium antagonist- prescribed for hypertension and certain types of angina. Purpose: The purpose of the present study was to investigate the prevalence rate of Nifedipine induced gingival hyperplasia in patients and its probable relationship with age, gender, plaque score and drug consumption period. Materials and Methods: The study was on 200 patients with heart disease. The gingival condition of 100 patients under Nifedipine treatment was compared with 100 controls treated with other hypertension drugs. Comparison of variables in study and control groups and also between patients with and without gingival hyperplasia was done using 2 and t- student tests. Results: The prevalence rate of Nifedipine- induced gingival hyperplasia, among experimental patients, was 17%, while it was not observed among control ones. Oral examination revealed gingival overgrowth as a lobular or nodular enlargement on interdental papilla located on anterior interproximal regions. Conclusion: In this study, there was a significant relationship between gingival inflammation resulting from dental plaque and drug dosage, with hyperplasia.
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Statement of Problem: DMFT and OHI- S indices are two of the most important quantitative factors, measuring tooth health and oral hygiene, respectively. Propose: The aim of this study was to study of correlation between these indices in 12- year old school girls of Kashan. Materials and Methods: A cross sectional study on the correlation between these indices were carried out on 242, twelve year- old school girls in Kashan and the results, have been presented in this paper. Results: The findings were as follows: Average and standard deviation of decayed, missed and filled teeth were (1.12, 1.5), (0.05, 0.25) and (0.28, 0.92), respectively. Average and standard deviation of DMFT was 1.45 and 1.73, respectively, with 45.5 percent of the cases being caries free (DMFT= O). OHI- S index, on the other hand, showed an average of 1.46 with a standard deviation of 0.42. Conclusion: The result of the 2.test, carried out on the measured data, showed no correlation between the DMFT and OHI-S indices.
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Statement of Problem: Bacterial agents are the primary cause of pulpoperiapical diseases. Therefore, an irrigating solution with proper antibacterial ability should be used to eliminate the bacterial agents during canal instrumentation. Purpose: The aim of present study was to compare the antibacterial effect of 0.2% chlorhexidine to 0.5% sodium hypochlorite as canal irrigating solutions. Materials and Methods: In this study 20 single canal teeth with necrotic pulps were selected by vitality tests and divided in two groups each one consists of ten. Each canal irrigated with 12 ml of 0.2% chlorhexidine in the first group and 0.5% sodium hypochlorite in the second one. Each canal was instrumented by 6 k- type files by step back procedure (two minutes for each file). After canal instrumentation, sterile cotton pellet was placed on the pulp chamber and the canals were filled temporarily by cavit. Samples were selected by two strile paper points both before the canal instrumentation (after accessing the canal) and 48 hours later. Samples were cultured on Mitis salivarius agar and anaerobic blood agar and then, the colony counts were reported in terms of CFU/ml. Results: Elimination percent mean of streptococcus mutans and anaerobics with 0.2% chlorhexidine were 99.9 and 99.02 respectively and for 0.5% hypochlorite were 99.7, and 92.7 respectively. Conclusion: There was no significant difference between these two irrigating solutions by non parameteric Mann-Whitney test.
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Statement of Problem: Patients affected with “Early Onset Periodontitis” (EOP), are not similar regarding their neutrophil deficiency and researches have yielded contradictory results in this field. Purpose: The purpose of this study was to evaluate different aspects of neutrophils’ activities in peripheral blood of such patients, especially those affected with prepubertal periodontitis and juvenile periodontitis, in Iran. Materials and Methods: twenty patients, of periodontoloy department of dental faculty of Tehran University of Medical sciences, associated with 16 healthy subjects as controls, were referred to department of Immunon & Allergy Childrens Hospital, Medical Center Tehran University, in order to investigate the relationship between the rate of chemotaxis, phagocytosis and respiratory explosion of peripheral blood neutrophils, with EOP disease. In order to measure chemotaxis rate, Boyden Chamer method was used. Also, for evaluation phagocytosis, the percentage of neutrophils that ingested yeast was investigated microscopically. To measure NADPH oxidase enzyme activity, which acts at the beginning of neutrophils respiratory explosion pathway, slide method was used. Measurements of phagocytosis, NBT and chemotaxis in control and case groups were compared using one- sample t test. Results: Results showed that there was no significant difference between the mean of chemotaxis of patients (104.85)μ-and the control group (116.93) μ-. However, 15% of patients showed a significant decrease in chemotaxis that 33% of them were affected with prepubertal periodontitis and only one case was affected with juvenile periodontitis. The average rate of phagocytosis in patients and controls were 68.7% and 67.31%, respectively. No significant difference between the average of Nitro Blue Tetrazolium Test (NBT) positive neutrophils in patients (97. 45%) and the controls (97.62%) was observed. This study showed that females affected 3 times more than males. Conclusion: This study showed that there was not significant difference between the average of phagocytosis, NBT and chemotaxis in patients with EOP and controls and females.
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