JOURNAL OF ISFAHAN DENTAL SCHOOL
Year:2007 | Volume:3 | Issue:1|Papers Count:10

Introduction: Investment materials have been used to produce molds for casting of Inlays, Onlays, crowns and bridges. In this study, gypsum and investments routinely used in Iran, were evaluated and characterized, then α hemi hydrate calcium sulfate and a new dental investment with a gypsum-micro silica binder were fabricated. The purpose of this study was to produce and evaluate a new gypsum investment product in Iran. Using this production, it could be not necessary to import this material from other countries.Methods and Materials: Yellow, well-mixed, orthodontic gypsums and casting investments routinely used in Iran, were evaluated and characterized with scanning electron microscopy elemental analysis (SEM) and XRD phase analysis. The morphology of these materials also was evaluated. Gypsum mineral (CaSO4.2H2O) was fired at 3 atmosphere autoclave and dental stone produced, and evaluated. New dental investment was fabricated with fine silica, Alumina, Silicon Carbide, Micro Silica and Polypropylene. Cold crushing strength (CCS) and setting expansion tests were performed. Casting was done at new molds. Phase changing of investments was tested at high temperatures with x- ray diffraction phase analysis. Compressive strength of some samples was tested after firing.Results: Using above techniques showed that yellow and well-mixed gypsum are dental stones, orthodontic gypsum is high strength stone and investments have phosphate bonds. New investment has efficiency at 1000oC, and more. There isn't any decomposition in gypsums at these temperatures. Silicon Carbide and polypropylene increase CCS. Compressive Strength of these new investments increases 7 times after firing.Conclusion: Micro silica is used as a refractory and binder. Micro silica is very fine and has a large specific surface. So it is a good binder and it leads a smooth surface castings. Silicon Carbide increases investment strength and thermal resistance. Poly propylene increases spaces for escaping of gases during casting. New gypsum- micro silica investment can be used at temperatures more than 1000oC .There are other materials which were proposed before to increase thermal resistance of gypsum investments, but they are more expensive than micro silica based products.

Introduction: Gingivitis is the most common type of gum disease, mainly caused by microbial plaque. Therefore, the plaque control plays an important role in preventing the incidence of gingivitis and other periodontal diseases. There are various methods to control dental plaque and chemical and mechanical methods are very common. The most common chemical method of plaque control is using mouth-rinses. This study compared the effects of two mouth-rinses on reducing dental plaque: Irsha which is an Iranian mouth-rinse product; and chlorhexidine which is a standard mouth-rinse.Methods and Materials: In this cross-over clinical trial study, 14 volunteers in two groups (n=7) participated. One group started with rinsing twice a day with 10 cc of chlorhexidine for a week, followed by 10 days stop and then a week of rinsing with Irsha (anti plaque). The other group followed the same procedure except that started with Irsha (anti plaque) mouth-rinse. The subjects refrained from all mechanical oral hygiene procedures during the weeks of using mount-rinses. The subjects were examined twice during the study and the Sillnes-Loe Plaque Indices were recorded before and after mouthwash periods. Data were analyzed using paired t-test to compare the mean of plaque indices before and after using each mouth-rinse and t-test to compare the mean of plaque reduction in the two groups.Results: The results showed that the mean plaque index was significantly reduced after using chlorhexidine, but Irsha had no significant plaque reduction (p=0.917).Conclusion: In brief, the results showed that while chlorhexidine is very effective in controlling dental plaque, the anti-plaque effects of Irsha is not considerable at all.

Introduction: By increase of esthetic demand, application of resin composite as a posterior restoration is greater than before. Microleakage and post operative sensitivity are two challenges to the success of this filling material. To overcome these, the best selection of dentin bonding system and light curing units are important. This study evaluated the two above mentioned factors.Methods and Materials: In this experimental study class II cavities were prepared in both mesial and distal side of 30 healthy third molar teeth, and the samples randomly divided into 4 groups. Each group restored by use of one of these bonding system: total etch (Excite) or self etch (SE Bond) and one of light curing units: QTH or LED, and a similar restorative composite. After thermocycling, sealing and immersing the samples in dye, they sectioned and evaluated by steriomicroscope and analyzed by Mann-Whitney test.Results: LED light curing unit and self etch bonding agent had best result in controlling microleakage.Conclusion: LED depth of cure is more than that of QTH and the efficacy of self etch primer to infiltration etched dentin is greeter than total etch dentin bonding agents, because they do not dehydrate dentin and do not collapse collagen fibers.

Introduction: Responses of dental pulp in primary and permanent tooth are different to pulp therapy, trauma, caries, dehydration, pulp tester and dental materials. The reactions of primary dental pulp in compare with permanent dental pulp are different.Can these various reactions be attributed to different histological characteristics in two groups of teeth? The aim of this study is comparison of histological characteristics between dental pulps in two groups of teeth of dog.Methods and Materials: 20 primary and 20 permanent teeth of two dogs were selected. Forty teeth were extracted under general anesthesia. 1-2 millimeter of apices of roots were cut and immersed in 10% formaldehyde solution. Then the samples were sent to oral histological lab for staining and sliding. Oral pathologist examined the histology of dental pulps and reported the results. The data of study were analyzed by SPSS software 11.5. Then data were compared with Mann-Whitney and t-test. Finally findings were reported.Results: The relative frequency of fibroblasts, mesenchymal undifferentiating cells, blood vessels, collagen and nerve fibers and immune cells in primary and permanent dental pulp in dog had no significant difference (p value<0.05). The numbers of fibroblast, mesenchymal and immune cells in two groups of dental pulp had no significant difference (p value<0.05).Conclusion: According to the findings of this study, histological characteristics of primary and permanent teeth in dog are similar. It recommends studies using floucythometry, PCI, Electron microscopy and Immunohistochmical techniques in human and dog.

Introduction: External resorption of cervical area is one of the worst side effects of bleaching in non vital teeth. One method for inhibition is placing a coronal plug into the canal's entrance. Therefore sealing ability of 3 materials including Super EBA, MTA and Glass Ionomer were examined in this research as coronal plug before bleaching procedure.Methods and Materials: Seventy single canal anterior teeth were chosen by simple randomization. After access cavity preparation, the canals were cleaned and shaped. Five teeth were used as positive control and five as negative control. Other sixty teeth were filled with gutta-percha and sealer using lateral condensation method. In the next step, 3mm of gutta percha was removed from the coronal part and a thickness of 2mm of one of the materials (GI, Super EBA, MTA) was placed as coronal plug. Then the teeth were bleached 3 times with an interval of 72h, using Sodium Perborate and 3% H2O2.Then the access cavities were completely cleaned and filled with 2% methylene blue for 24h. The sample teeth were washed, dried and sectioned and dye penetration was measured using magnifying glass and cullies. Data was analyzed by ANOVA and LSD tests.Results: The average dye penetration was 3.23mm in MTA, 5.42mm in Super EBA and 1.76mm in GI group (p value = 0.018).Conclusion: Based on the results obtained from this study, glass ionomer was the best material for secondary seal before bleaching. Sealing ability of MTA was lower than GI, and of Super EBA was the least.

Introduction: Use of glass ionomer cement as pit and fissure sealant, has added benefit by its fluoride-releasing property. The efficacy of using invasive and non-invasive techniques was assessed by microleakage of Glass ionomer (Triage, G C Corporation, Tokyo, Japan) and Resin based sealants (Concise, 3M Dental Products, USA).Methods and Materials: In this in vitro experimental study, 80 sound premolars were divided into four groups of 20. In groups 1 and 2, Triage and in groups 3 and 4, Concise was used. In groups 1 and 3, fissures leaved intact (Noninvasive technique). In groups 2 and 4, fissures were prepared with tapered diamond bur (Invasive technique).The teeth were thermocycled at 5o-55oc for 250 cycles and immersed in 5% methylene blue solution for 24 hours. Sectioned samples were observed for the extent of dye penetration, and scores were based on established scoring criteria.0- Without dye penetration.1- Dye penetration restricted to the outer half of the sealant.2- Dye penetration restricted to the inner half of the sealant.3- Dye penetration into the underlying fissure. The data were analyzed using Kruskall-Wallis and Man-Whitney tests.Results: There were no statistically significant differences between invasive and noninvasive techniques; but microleakage of Triage was statistically more than Concise.Conclusion: Because there was no difference between the two techniques, invasive technique is not recommended. Considering the recent controversies, it can be said that Triage cannot be a viable alternative for resin based sealants.

Introduction: Chemical plaque control methods are recommended as adjunctive to mechanical plaque control methods. The aim of this study was to determine and compare periodontal probing depth (PPD) and bleeding on probing (BOP) indices with and without application of 25% metronidazol gel.Methods and Materials: 20 patients with chronic periodontitis were randomly selected. In each patient a quadrant with probing depth of 3-5 mm was randomly selected as test tooth and the symmetric tooth with the same condition in the contralateral quadrant was selected as control tooth.After scaling both the test and control teeth, the metronidazol gel (25%) was applied to the test tooth site. The patients were examined on days 0, 7 and 21 and PPD and BOP indices were measured.Results: The results showed a significant decrease in pocket depth and the absence of bleeding on probing on day 21 between the two groups of test and control (P<0.005).Conclusion: This study shows that using metronidazol gel is an effective adjunctive local therapy to mechanical treatments. This is due to the efficacy of metronidazol gel in decreasing anaerobic microorganisms and its effective delivery in periodontal pockets.

Introduction: Multiple myeloma is a malignancy of plasma cells which affect the jaws in 15-30% of the cases. This paper explains a case of the multiple myeloma and its diagnosis.Case Report: The patient was 70 years old; he complained from painful nodule in the mandible interfered in chewing. In clinical examination some nodules were seen in the skull and jaws. In radiographic examination multiple destructive lesions were seen in the skull and jaws. The differential blood count (CBC diff), the urine analyzes, and biopsy was done. The diagnosis was multiple myeloma. More examinations and treatment process were done by oncologist.Discussion: Although this is rare that the first signs of multiple myeloma are in the mouth and a patient comes to the dentist for diagnosis, but knowledge of the signs of this malignancy leads to fast diagnosis and treatment and improving the life time and the quality of life.