JOURNAL OF DENTISTRY (SHIRAZ UNIVERSITY OF MEDICAL SCIENCES)
Year:2010 | Volume:10 | Issue:4 (25)|Papers Count:15

Statement of Problem: Understanding the effects of orthodontic force on the pulp is of particular interest, especially because altered pulpal respiration rate, secondary dentin formation, internal root resorption, and even pulpal necrosis have all been associated with orthodontic treatment.Purpose: The aim of this study was to evaluate and compare the effects of orthodontic extrusive and intrusive forces on the histologic changes of the human dental pulp after 3 days and 3 weeks.Materials and Method: In this study, 52 sound upper first premolars from 26 patients, scheduled for extraction for orthodontic reasons, were selected. The patients were divided randomly into 2 groups (3 days and 3 weeks). In each group, 10 teeth received orthodontic extrusive forces, 10 teeth underwent intrusive forces and 6 teeth served as controls. Histologic changes were evaluated and the data were statistically evaluated by nonparametric tests.Results: Vacuolization and disruption of the odontoblastic layer showed statistically significant differences between the control and either of the experimental groups in each test period. Furthermore, fibrous tissue formation in the extrusive group was significantly higher than the control group in the 3-week period. There was no significant difference between 3-day and 3-week intervals in each experimental group, except that fibrosis in the extrusive group was significantly increased after 3 weeks of force application. Comparison between extrusive and intrusive groups revealed no statistical significance in each test period.Conclusion: The results indicate that if orthodontic forces are applied in the optimal range and are not more intense than the physiological limit of tissue tolerance, irreversible injuries to the pulp can be prevented.

Statement of problem: Root perforation is a procedural error that can have a profound effect on treatment prognosis. Treatment prognosis is dependent on the prevention or the treatment of bacterial infection at the perforation site. Therefore, using a biocompatible material to completely seal the perforation is of paramount importance.Purpose: The purpose of this study was to evaluate and compare the ability of Pro Root MTA and Portland cement to seal furcal perforations in the extracted human molar using dye penetration.Materials and Method: In this experimental in vitro study, 70 human permanent mandibular molars with well developed, non-fused, minimum caries and without anomalies were used. Access openings and furcation perforations were prepared in the pulp chamber floor. Ten teeth were assigned as controls and divided into two groups of five teeth each as positive and negative control. The positive group was accessed and perforated similar to the experimental group while the negative controls were not prepared. The remained 60 teeth were divided into two groups of 30 teeth each. Group A1 was repaired with Pro Root MTA and group A2 was repaired with Portland cement. The teeth were submerged in Indian ink for 4 days. Finally, the samples were sectioned and evaluated for linear dye penetration at 6x magnification and then the data were statistically analyzed by Mann-Whitney test.Results: The result showed that the sealability of Pro Root MTA and Portland cement in furcation perforations was not statistically different (p>0.05).Conclusion: In accordance with high expenses of Pro Root MTA and the same ability of Portland cement and Pro Root MTA in sealing of furcation perforation, the Portland cement could be a good alternative for Pro Root MTA for this purpose.

Statement of problem: Autoploymerized acrylic resins are used for construction of fixed provisional restorations. The linear polymerization shrinkage and water absorption are the critical factors in the desired properties of such restorations.Purpose: The aim of the present study was to compare the dimensional changes and water absorption of three fixed provisional acrylic resins,Trim II, Tempron, and Acroprars TRII.Materials and Method: In this experimental study, 90 acrylic samples (20 mm × 12 mm × 3 mm) were made by a metal mold (30 samples in each group). Then, each group was randomly divided into two equal groups. Dimensional changes of the samples were measured immediately after polymerization and seven days post curing. The data were analyzed by one way ANOVA and T-test.Results: Acropars TRII resin exhibited the highest dimensional changes and water absorption. The lowest mean values were recorded for Tempron samples. One week after polymerization, no statistical difference was found between the dimensional changes of Trim II and Acropars TRII. Linear dimensional changes of all the used acrylic resins were less than 2%.Conclusion: It seems that water absorption of acrylic resins can compensate the polymerization shrinkage. This effect was more significant for samples made by Acropars TRII than the other tow groups. Clinically, linear dimensional changes of the three acrylic resins were acceptable.

Statement of Problem: Prefabricated posts have recently become more popular due to their satisfactory results while saving time and reducing costs. Glass-fiber prefabricated posts were paid more attention because of reducing the risk of root fracture as well as minimal allergic hypersensitivity and corrosion with satisfactory cosmetic results. Surface treatment is one of the various factors that might affect retention of a post.Purpose: The purpose of this study was to evaluate the effect of surface treatment on the retention of an Iranian Eglass fiber post.Materials and Method: Thirty two intact central maxillary incisors were selected. The coronal aspect of each tooth was removed and the remaining root received endodontic therapy. The specimens were then divided into 4 groups (n=8). Post spaces were prepared to a depth of 10mm.The posts (HtCo, Iran) received one of the surface treatments including cleaning with alcohol (Alc), air borne-particle abrasion and cleaning with alcohol (Air-Alc), cleaning with alcohol and conditioning with silane treatment (Alc-Sil) or airborne- particle abrasion, cleaning with alcohol and conditioning with silane treatment (Air-Sil). All the posts were luted with Panavia F after conditioning the canal dentin primer (ED-primer) according to the manufacturer's instructions. After cementation, the specimens were stored at 37oC for 30 days and subjected to simulated aging conditions, consisting of 7500 thermal cycles (5oC/55oC). Retention of the posts was measured with a universal testing machine with a crosshead speed of 2mm/min. The data were analyzed using one-way ANOVA and Duncan tests (a=0.05).Results: The mean retentive values (N) of the test groups were as follows: Alc=157.63±39.91, Air-Alc=171.53±47.80, Alc-Sil=167.87±42.49, Air-Sil=166.53±40.32. There was no significant difference between the mean values of the four groups.Conclusion: Treating the surface of HtCo Iranian post produced no significant improvement in the retention of the posts.

Statement of problem: The fracture resistance of the root canal is mainly associated to the kind of the post used for treatment, and studies indicate that there are still different opinions about the fracture resistance of root canals when Non-Metal posts are used.Purpose: The purpose of this study was to compare the fracture resistance of four adhesive non-metal posts with different MOEs against compressive load in endodontically treated teeth.Materials and Method: In this In-vitro experimental study, a total of 40 recently extracted mandibular premolars were selected, sectioned adjacent to the CEJ, and endodontically treated. The specimens were randomly assigned to four groups (n=10). Post spaces were prepared and the fiber D.T. Light posts, D.T. Composi post, D.T. white posts and Cosmopost were cemented. Composite resin (Lumiglass) cores were built up. After simulating the PDL, the specimens were embedded in acrylic resin, and then secured in a Universal Testing Machine. A compressive load was applied at a 45o angle to the long axis of the tooth until fracture, at a crosshead speed of 1mm/min. The data were analyzed, using one-way ANOVA and Tukey’s test (p<0.05).Results: The teeth restored with D.T. white fiber posts exhibited significantly higher resistance to fracture. Those restored with the other 3 groups were statistically similar (p>0.05). Fractures observed in the fiber groups would allow further restorations of the tooth, whereas unrestorable, catastrophic fractures were observed in the Zirconia (Composi) group.Conclusion: Since Zirconia post should be used catiously due to the unfavorable and unrestorable fractures created, fiber posts are indicated, in endodontically treated teeth.

Statement of Problems: Tooth size is correlated to gender, race, arch alignment, and malocclusion type. Correct tooth size relationship between the maxillary and mandibular teeth is an important factor to achieve a proper occlusal interdigitation during the final stages of orthodontic treatment.Purpose: The aim of this study was to compare the mesiodistal tooth size between cl III and cl I patients in an Iranian population.Materials and Method: In this cross- sectional study, 120 patients (50 cl I and 70 cl III malocclusion) were selected. The inclusion criteria for the subjects were complete permanent dentition with no caries, proximal restorations, attrition or dental anomalies. The greatest mesiodistal tooth width from the first molar to the other side was measured on the orthodontic models by digital caliper with 0.01 accuracy. The measurements were obtained by a single person twice. All the data were categorized in different malocclusion groups and sex differentiation and analysed by student’s t-test and one way ANOVA.Results: This study showed that a significant right to left side tooth size discrepancy was found in some of the teeth in cl I and cl III with maxillary deficiency. No significant tooth size differences were found between the two sides in the mandibular excess cl III. Females showed a tendency of having smaller teeth than males. In the maxillary deficient cl III malocclusion, the maxillary first molar, the first mandibular and maxillary premolars were larger than cl I malocclusions. The maxillary first molars were smaller in the mandibular excess cl III than cl I mal occlusions. Conclusion: Although this study showed some differences in the mesiodistal tooth size between cl I and cl III malocclusion, this difference was not for all the teeth.

Statement of problem: One of the major problems in composite restorations is polymerization shrinkage leading to microleakage, hypersensitivity, recurrent carries, pulpal inflammation, and later pulp necrosis. To overcome these problems, different photo-activation methods have been employed to prolong the plastic phase during polymerization.Purpose: To investigate the mircoleakage in 3 groups of Pulse, Ramp and conventional LED photo-polymerization methods in class V composite restorations.Materials and Method: Twenty one freshly extracted human premolars were categorized in 3 groups of 7 each. Slot shaped class V cavities (4×2×2 mm) were prepared on both buccal and lingual surfaces of the teeth, with occlusal margins on the enamel and gingival margins 1mm below the CEJ. The cavities were restored with single bond and Z100 composite (3M ESPE, USA) and cured in group A with Ramp, group B with Pulse mode, and group C with Conventional mode using Apoza LED Turbo light Curing unit. After one day storage in 37oC water and thermo cycling for 1000 cycles, the teeth were sealed with nail varnish 1 mm short of margins, immersed in AgNo3 50% W and then developed in solution. The specimens were cut and evaluated by Stereo microscope at 40 x magnification. The results were statistically analyzed by kruskal- Wallis test. Results: None of the specimens revealed microleakage at the occlusal margins but 69.2% of the specimens in Ramp group, 76.9% in the Pulse group and 61.5% in the conventional group showed score 1 gingival microleakage. Also, 30.8% in the Ramp and Conventional and 23.1% in the Pulse group showed score 2 gingival microleakage. Analysis of the data among the 3 groups revealed no statistically significant differences. (p=0.640) Conclusion: Based on the limitations of this study:1- All of LED photoactivation modes using Apoza LED turbo unit prevent microleakage in the enamel margins.2- None of the photoactivation modes can prevent microleakage in the gingival margins completely.3- For Z100 (microhybrid composite), all of the 3 employed methods were equally effective in microleakage reduction.

Statement of problem: Salivary gland neoplasms show varied histological and biological characteristics, and there may be difficulty in differentiating between low grade malignancies and benign tumors of the salivary glands.Purpose: The aim of this study was to investigate the diagnostic value of modified AgNOR technique in distinguishing between benign and malignant salivary gland tumors.Materials and Method: In this cross-sectional study, 40 benign salivary gland tumors (34 pleomorphic adenoma, 6 warthin tumor), 40 malignant neoplasms (26 adenoid cystic carcinoma, 14 mucoepidermoid carcinoma) and 10 chronic sialadenitis were stained with modified AgNOR technique. AgNOR counts, variation in size and dispersion of AgNOR dots in the cells were graded and compared in benign and malignant tumors. The data were statistically analyzed by ANOVA, Tukey, t-test and Kruskal-Wallis tests.Results: The mean AgNOR counts for the benign neoplasms (1.29±0.13) were less than those for the malignant neoplasms (2.87±0.25). Variation in AgNOR size and dispersion was of a higher grade in malignancy when compared with benign neoplasms (p<0.05).Conclusion: Our results suggest that modified AgNOR staining is useful for distinguishing benign from malignant tumors, but variation in AgNOR size and dispersion in addition to the count should also be considered.

Statement of Problem: One of the factors leading to failure of sealant therapy is microleakage. Various materials and methods have been recommended in order to reduce this phenomenon. They include the use of sealants with high and low filler content and the use of adhesives and other conditioning systems for preparation of etched enamel surface.Purpose: The aim of this experimental study was to assess the effect of one-bottle adhesive system on the marginal microleakage of the filled and unfilled fissure sealant.Materials and Method: Forty extracted human caries-free premolars were randomly assigned into 4 groups of 10. The teeth in each group were sealed according to the following protocols: 1) etching+unfilled sealant (clinpro) 2) etching+filled sealant (Delton Fs Å) 3) etching+single Bond+unfilled sealant 4) etching +single Bond+filled sealant. The teeth were then thermocycled (500 cycles between 5oC and 55oC) and immersed in 1% buffered methylene blue dye for 24h. Each tooth was divided into three sections, and each section was analyzed for microleakage, using a stereomicroscope. Kruskall-Wallis test was used for comparison of microleakage among the four groups.Results: The results showed that all the groups had some degree of microleakage and there was not any significant difference among them (p>0.05).Conclusion: The addition of filler particles to sealants and using a bonding agent system (Single Bond) had no effect on reduction of the microleakage.

Statement of Problems: Bleeding on probing is widely used for diagnosis and screening of periodontal diseases, evaluation of treatment outcome, and determination of the development of the disease. The presence of bleeding on probing (BOP) is considered as the sign of gingival inflammation, and lack of bleeding is the sign of the gingival health. Aspirin has been suggested as an effective factor on increasing the amount of BOP that may result in inappropriate clinical diagnosis.Purpose: The aim of this study was to evaluate the effect of aspirin on BOP in patients with gingivitis. Materials and Method: An experimental, double blind cross-over clinical trial was performed on 50 patients. The patients were divided into case and control groups. The amount of BOP was recorded on the first day in both groups. Coded capsules containing aspirin (100mg) or placebo were randomly given to the patients to be used one per day for one week. A wash out period of 7 days was allocated between the use of aspirin and placebo. The amount of BOP was recorded at the end of days 7 and 14 in each group. Results: The amount of BOP in the case and control groups at the base line was 49%±17 and 47%±15, (p=0.3) and on the 7th day, it was 49% ±18 and 50%±21 (p=0.7), respectively. On the 14th day the BOP in the case and control groups showed to be 46±19 and 49±17 (p=0.9) receptively. No statistically difference was found to be in different periods of the study.Conclusion: Intake of low dose aspirin (100mg) for 7 days in individuals with gingivitis does not increase the amount of BOP as compared with placebo.

Statement of Problem: Due to the significant correlation between salivary AST activity and periodontal disease, AST activity can be used as a useful marker for monitoring of the periodontal disease.Purpose: The aim of this study was to determine whether the initial phase of periodontal treatment could modify the salivary AST level in patients with moderate to severe periodontitis referred to Periodontics Department of Islamic Azad University, Dental school Tehran (1386). Materials and Method: In this clinical trial study (before & after), 33 patients (mean age of 45±9.75) with moderate to severe periodontitis were selected. Plaque index, pocket depth, clinical attachment level, bleeding on probing and salivary AST were determined before and two months after the initial phase of periodontal treatment for all patients. The effects of treatment were assessed by Paired-T and Wilcoxon Sign tests. Result: Following phase I periodontal treatment, plaque index, pocket depth, clinical attachment level and bleeding on probing decreased significantly (p<0.05). Salivary AST changed from 40.3±15.5 to 32±12.1 (p<0.01).Conclusion: Based on the statistically significant decrease in the salivary AST level after the initial phase of periodontal treatment, this biochemical marker may be used for evaluation of periodontal treatment.

Statement of Problems: Job burnout is a result of frequent and constant physical and mental stress in a long time. Dentistry is one of the most stressful jobs in the field of medicine. These stressful factors make dentists prone to burnout and psychological disorders such as depression and anxiety.Purpose: The aim of this study was to measure the relationship between demographic and personality characteristics and job satisfaction and burnout in dentists.Materials and Method: In this simple filter sampling study, 30 dentists as faculty members of the dental school of Shiraz University filled in questionnaires about job satisfaction, job burnout and general health. Statistical methods such as Pierson Correlation Coefficient, Multivariate Analysis and Chi-Square test were used. Results: In this study, 12 males (40%) and 18 females (60%) were involved. The mean occupation year for females were more than that of males. Meanwhile, men practice more hours a day. There was no significant difference between males and females regarding general heath and job satisfaction. Dental chair side hours and years of occupation had no effect on general health and job satisfaction. The results showed that NEO 5-personality factors, sex, occupation years and age did not have any meaningful effect on job burnout, but this study could predict 29% of the job dissatisfaction (p=45%; F=06%; R square=29%; R=54%). Conclusion: In this study, age, sex and occupation years did not have any effect on the job burnout, but with the increase in the volume of the sample, it would be meaningful. This study was conducted only on the faculty members; which makes it different from other studies.

Statement of problem: Awareness of clinical dental students’ points of view about the educational situation of different departments will help faculty members and those in charge of educational affairs to improve the students’ qualitative as well as quantitative scientific skills. Being so, to achieve such a goal, it seems necessary to conduct a research on evaluation of educational condition of different dental departments from students’ points of view.Purpose: The aim of this study was to evaluate the weak and strong points of different departments of Shiraz Dental School as determined by dental students’ points of view in order to present new methods to improve future educational policies of dental departments.Materials and Method: In this cross-sectional study, a questionnaire made of seventeen standard questions was used. After confirmation of the validity of the questions, the questionnaires were distributed among 43 fifth and sixth year students of Shiraz Dental School. After completion of the questionnaires, the data were analyzed by Kruskall- Wallis and Mann- Whitney tests, using SPSS software.Results: Based on the results of this study, although there was a low rate of fluctuation in the students’ rate of satisfaction from educational situation of different departments, the highest satisfaction rate was belonged to pedodontics and periodontics departments respectively , and the least satisfaction rate belonged to oral surgery department.Conclusion: In spite of the difference in answers given to similar questions such as scientific capability of faculty members, equipment of departments and behavior of personnel and faculty members to students, generally speaking, the rate of students’ satisfaction from different departments was almost similar to each other and had a low fluctuation rate (p>0.05).