Vol 2, No 3 (2005)
Proceeding Abstracts
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Statement of Problem: Since the fluoride releases from materials with the property of releasing fluoride are decreasing gradually, it seems that probably the material rechargeability is more important than their long-term fluoride release. Purpose: the objective of this study was to asses the fluoride release and rechargeability of 2 types of fluoride releasing restorative materials, a resin modified glass ionomer (Vitremer) and a compomer (Compoglass F), after exposure to daily NaF solutions containing 1000 ppm F, for 1 minute. Materials and Methods: Twelve discs ( 8 mm ×2 mm) of each of the materials were fabricated, and divided into 2 groups (test and control). All discs were stored in 4 mL artificial saliva at 37C. In group 1 (N=6), the specimens were immersed in artificial saliva which was changed daily for 25 days. In group 2 (N=6), in addition to receiving the same treatment as group 1, the specimens were immersed in NaF solution (1000ppm F, ph=6.9) for 1 minute before daily saliva change. A potentiometer was used to determine the amount of fluoride released on days 1, 2, 3, 5, 10, 15, 20 and 25, after the daily saliva change, in all study groups. Data were analyzed by the t-student test after confirmation of the equality of variances by Leven’s test. Results: Both materials continued releasing fluoride throughout the whole study period. For each material, the release was highest on day one. During the first 3 days, glass ionomer released significantly higher amounts of fluoride as compared to compomer (p<0.05); but afterwards, there was no significant difference between the 2 materials (p>0.05). After exposure to NaF solution, none of the materials showed statistically significant rechargeability (p>0.05) and the amount of fluoride-release continued to drop during the study period in similar patterns for both the test and the control groups. Conclusion: It may be concluded that rechargeability of glass ionomer and compomer, using daily neutral fluoride mouth rinses and toothpastes does not occur in reliable amounts.
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Statement of Problem: Some vertical changes might be observed during the first stage of orthodontic treatment, aligning and leveling. Purpose: The aim of this study was to evaluate dental and/or skeletal vertical changes occurring in the first stage of preadjusted orthodontic treatment. Materials and Methods: Fourteen patients with an average age of 14.1 years were selected for this study. Preadjusted appliances were used and a lateral cephalogram was taken, subsequently. All patients were treated with four first premolar extractions. After 8 weeks of aligning and leveling, a second cephalogram was obtained. Results: No statistically significant changes including extrusion of all teeth except maxillary incisors were observed during this phase. Skeletal vertical changes also showed a slight non-significant decrease. Conclusion: The results of this study showed minimal vertical changes during the first stage of fixed orthodontic treatment with preadjusted appliances; therefore use of such appliances in patients with a tendency towards increased vertical dimensions could be justified.
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Comparison of Extraction and Non-extraction Orthodontic Treatment using the Objective Grading SystemStatement of Problem: The extraction versus non-extraction debate is almost as old as the advent of orthodontic practice and up to now, this dilemma remains. Recently, the American Board of Orthodontics (ABO) has developed a method by the name of Objective Grading System (OGS) in order to evaluate the results of orthodontic treatment. Aim: The aim of the present study was to evaluate and compare the patients’ final occlusion after extraction and non-extraction therapy using the OGS. Materials and Methods: Sixty sex-matched cases with an age range of 15-20 year old were selected and evenly divided into 2 groups as follows: 30 patients were treated by extraction of 4 premolars and 30 received a non-extraction treatment. All patients had class 1 malocclusion before treatment and were well treated with the standard edgewise system in a private clinic. With the aid of an ABO measuring gauge, 8 parameters of occlusion were measured 3 times, each. Reproducibility of the measurements were evaluated by use of the Phi correlation coefficient and the total OGS scores between the two groups were compared using Levene`s test and Student t- test with the significant level at 95%. Results: The mean OSG scores were significantly more negative in the non–extraction group (-6.58 8.63) as compared to the extraction group (-28.65 6.67, p < 0.004). Acceptable occlusion was observed in 73.4% of the extraction and 43.4% of the non-extraction cases. Conclusion: In this study according to the ABO grading system (OGS), the final occlusion of patients treated with extraction seemed more acceptable than non-extracted cases.
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Statement of Problem: Recurrent aphthous stomatitis (RAS) is one of the most common inflammatory diseases encountered in dental practice, but the precise etiology and pathogenesis of the disease is not fully understood. Vascular endothelial growth factor (VEGF) is a multifunctional angiogenic cytokine involved in angiogenesis and wound healing. There is evidence that VEGF could play an important role in recruiting inflammatory infiltrates like those in RAS. Purpose: The aim of this study was to investigate salivary levels of VEGF in various stages of RAS. Materials and Methods: In a case/crossover study, salivary VEGF levels were determined in 31 patients with RAS. Their saliva was collected by the spitting method in specially prepared tubes in two stages; the active phase (first week) and the remission phase. Salivary levels were then determined using the Sandwich ELISA technique and the data were analyzed by the Wilcoxon test. Results: Patients in the remission period had increased VEGF values, 571.774 (347.5499) pq/ml, as compared to the acute stage, 424.758 (235.1474), and the difference was significant (P< 0.05). Conclusion: Salivary VEGF levels seem to be associated with ulcer development in RAS, supporting the concept of a potential association between RAS and VEGF.
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Statement of Problem: Early diagnoses of oral malignancies and pre-malignancies have direct effect in the outcome of these lesions. Therefore the techniques for early diagnosis have been considered as useful method in practice. Purpose: The aim of this study was to evaluate the reliability of Oratest and Generic Toluidine Blue (GTB) in the detection of oral malignancy and premalignancy. Materials and Methods: The study group consisted of 30 patients with potentially malignant epithelial lesions and superficial oral ulcerations suggestive of malignancy; of these, 7 patients with oral squamous cell carcinomas (OSCCs) were considered as positive controls and 7 patients with benign epithelial lesions as negative controls. These cases were selected from patients who were referred to the Cancer Institute, Tehran University of Medical Science (TUMS), Department of Oral Medicine, Faculty of Dentistry, TUMS and Department of Oral Medicine, School of Dentistry, Azad University of Medical Science. All lesions (n=49) submitted to both rinses (with intervals of at least 24 hours), followed by biopsy and histological analysis. Results: The sensitivity of Oratest was 93.6%, the specificity 80%, the positive predictive value 76.6% and the negative predictive value 94.7%. These results for GTB were 84.8%, 81%, 77.7% and 86.3% respectively. Conclusion: Staining with Oratest and GTB is highly reliable for the detection of insitu and invasive carcinomas and as an adjunct to clinical judgment and not a substitute for biopsy. The results of Oratest are more reliable than GTB especially in the detection of dysplastic lesions
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Statement of Problem: Mechanical failure of ceramic materials is controlled by brittle fracture, mostly occurred in tension. In 3-unit all-ceramic FPDs the connector area is considered to be at fracture risk because of tensile stress concentrations. Purpose: The aim of this FE analysis was to evaluate the effect of taper on stress distribution in all-ceramic FPDs. Materials and Methods: In this experimental study two 3-D finite element models of thee-unit IPS-Empress 2 FPDs replacing mandible second premolar were created by means of finite element software. The digital images were obtained from CT scan of human skull. Abutment was reduced with 12 and 22 degrees of taper. The cement layer, PDL, cancellous bone and cortical bone were also modeled. Frameworks of core material were fabricated. A static load of 100 N was applied at mid pontic area. Resolved stresses were calculated according to the Von Mises criterion and principal stresses. Results: In both models stresses were concentrated at the connectors. The maximum stresses were lower in the model with larger taper. The maximum Von Mises stress was recorded at the connector region of the premolar and the pontic. In model with larger taper the patterns of stresses were also more distributed and less concentrated. Conclusion: The highest Von Mises and principal stress were recorded at the connectors. Tensile stresses developed at the gingival connector of premolar and pontic was higher than molar. The stress level in model with 22-degree taper was lower compare to 12-degree and the stress pattern was more distributed, lowered the risk of concentrations.
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Statement of Problem: Snoring is the most common sleep disorder which in itself may only be viewed as an obnoxious disturbance in human society; however it must be considered a potential indicator of significant medical problems such as: hypertension, obstructive sleep apnea, cerebrovascular infarction and ischemic heart disease. Purpose: The purpose of this study was to evaluate the effectiveness of a modified type of Mandibular Repositioning Device (MRD splint) on the treatment of snoring. Materials and Methods: This before and after interventional study was carried out on 15 patients (4 females and 11 males) who suffered from snoring. All subjects had no upper airway obstruction. Maxillary and mandibular splints were made by clear heat-cured acrylic resin. A special screw connected to the anterior portion of the maxillary splint and an orthodontic wire No 1 positioned on the lower splint. The devices were tried in the mouth and relined with a softliner. This appliance was designed to protrude the mandible by use of a screw system. Snoring grades were detemined before, and 3 weeks after treatment with the MRD. Data were analyzed by the Wilcoxon test. Results: A significant difference was observed between the snoring severity, before and after using the splints (P = 0.001). Conclusion: The present study showed this modified type of splint can be effective in decreasing or eliminating snoring. The effectiveness of the splint in the treatment of snoring could be related to its role of widening the upper airway.
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A new design for replacing a missing anterior tooth is described. In this article, a lingually fixed partial denture, its advantages, disadvantages, indication and contraindications have been explained. The ability of this design to replace a single missing central or lateral incisor is discussed.
