Journal of Dentistry, Shiraz University of Medical Sciences
Volume:8 Issue: 1, 2007

Statement of Problem: Cleaning and shaping of the root canal system is an important objective of root canal therapy. Many automatic devices have been produced to simplify the preparation, and to decrease instrumentation time. One of these automatic devices with the general name of Endogripper is the new reciprocal handpiece called TEP-E10R. The purpose of this study was to compare hand and rotary reciprocal techniques in incidence of change in canal centring of the root canal. In this invitro study, 60 extracted mesial roots (120 canals) of human mandibular first and second molars were selected. The mesial roots were mounted in a metallic muffle. Sixty specimens were divided into four groups, (each group consisted of 30 canals). Each root was sectioned in two horizontal directions, the first cut was made five mm from the apical and the latter cut was made in the middle area of the root. The sections were photographed before instrumentation and then were reassembled in the metallic muffle and instrumented. In group one the preparations were made by NiTi files with hand instrumentation. In group two the preparations were made by stainless steel files with hand instrumentation, while in group three the preparations were made by Ni Ti files with use of TEP-E10R reciprocal handpiece, and in group four the preparations were made by stainless steel files and use of the same handpiece as in group three. After instrumentation, the metallic muffle was disassembled and the sections were photographed for the second time after preparation. The pre and post instrumentation photographs were superimposed using Adobe Photoshop and the canal center displacement in each section was measured. The collected data were analyzed with ANOVA and Tukey statistical tests. All specimens in the four groups showed canal center displacement. Group two had the most mean of canal center displacement in coronal sections which was significantly different from group one (p=0.008). In the middle sections, the highest mean of canal center displacement was seen in group four and it was significantly different from group one (p=0.001). In the apical sections, group two had the highest mean of canal center displacement which was significantly different from other three groups (p<0.001). Canal preparation with reciprocal handpiece (TEP-E10R) was similar to hand preparation technique with Ni Ti files in shaping of the root canal system.

Statement of problem: For reducing light exposure time of tooth-colored restorations, and chair time reduction, different experiments have been conducted. The purpose of this study was to determine the effect of different light exposure times to adhesive layers (Excite and Prompt L-pop) on the shear bond strength of dentin- composite interface. In this in-vitro study, 72 human intact premolar teeth were mounted in acrylic casts and enamel buccal surfaces were removed. The bonding surfaces were equalized using a surface index. Teeth were divided into six equal groups each of 12 (A, B, C, D, E, and F). According to the manufacturer instructions, Excite adhesive in groups A, B and C, and prompt L-pop in groups D, E and F was used. A and D groups were not exposed to light, but the exposure time in groups B, E and C, F was 20s, and 40s respectively. After one week of storage in 37°C water, synergy composite resin was applied and then was exposed to light. The specimens were loaded by shear force with 1 mm/min cross head speed. Data were analyzed by two-way analysis of variance (ANOVA). The means shear bond strength of groups A,B,C,D,E, and F were 3.9, 13.45, 18.1, 8.3, 24.81, 24.99 Mpa, respectively. The differences between shear bond strength of groups A, B and C and between groups B, D were statistically significant (p=0.0001). However, the differences between groups E, F were not statistically significant. In all exposure times, the bond strength of Prompt L-pop was significantly higher than that of Excite. According to the results of this study, increase in the light exposure led to the higher bond strengths in Excite groups. In Prompt L-pop groups, 20s exposure time was adequate and by increasing the light exposure time, shear bond strength was not affected. Without light exposure in both materials, the least bond strength for the composite resins was not attainable.

Statement of problem: In designing extension type removable partial denture (R.P.D), there is lots of controversy regarding the suitable location of rest seat of the terminal abutment. Discussions and Controversies are, mostly focused on minimizing lateral stress placed on terminal abutments. The purpose of this study was to assess the rate of stress placed on abutment teeth with different rest seat placements by a finite element method analysis. The skull of a 60 years old man was CT-Scanned with 0.5mm sections and data were used to make a 3.D model of the mandible. Then a partial denture was designed on this model, once with a distal rest on terminal abutment, and then with a mesial rest. Occlusal force was applied on the saddle, and stress was measured with a finite element method using "cosmos works 2003" soft ware. In both conditions, the highest stress concentration was observed on the distal surfaces of the abutment teeth, and the lowest stress on buccal cusps and roots of the teeth. The rest seat itself was the only place in which the observed stress was different in two conditions. The distal rest seat received more stress than the mesial rest seat. In both conditions the underlying bone received a moderate amount of stress, increasing in the distal part. Displacing the rest did not alter the stress applied on the abutment teeth. So it may be claimed that this factor could be neglected when determining the place of terminal rest of extension type RPD.

Statement of Problem: The main goal of endodontic treatment is eradication of microorganisms and their byproducts from the root canal system. The use of chemical irrigants during chemo-mechanical canal preparation is important for disinfection and cleaning of the canal system. The aim of this in vitro study was the assessment of bacterial growth after contact with several concentrations of essential oil of Zataria multiflora in varying time intervals. The essential oil of Zataria multiflora were serially diluted 8 folds and a fixed volume of the stationary phase culture of E.faecalis was added to each diluted solution, for varying intervals of 1, 5 and 15 minutes. 100µl of the contents of each tube were transferred to SF broth and incubated for 48h at 370c. Results of bacterial growth were recorded at the end of the incubation period. 2% solution of essential oil of Zataria multiflora at all intervals inhibits growth of E.feacalis. 1% solution of it showed antibacterial effect in 5, and 15 minutes. The concentrations under 0.5% dilution of Zataria multiflora did not eliminate E.faecalis at any time intervals. It seems that 1% and 2% solutions of essential oil of Zataria multiflora were effective at destroying E.faecalis. Application of this plant essential oil may be recommended for root canal irrigant following extensive ex-vivo and in-vivo experiments.

Statement of problem: Tooth extraction is one of the most controversial subjects in orthodontics due to its inevitable effects on facial esthetics, and smile characteristics. The aim of this study was to evaluate lip position in relation to S-line and Sn-pog', Merrifield Z angle, as evaluating well as upper and lower arch widths in canine, premolar, and molar regions following four premolar extraction in class I malocclusion patients. Pre and post lateral cephalograms and dental casts of 47 class I malocclusion patients including 43 girls and four boys with the mean age of 12.7±1.86, treated by the same practitioner were used in this study. All patients had four first premolar extraction, and orthodontic treatment was performed with 0.22 slot standard edgewise appliance. Convenient improbable sampling was used in this cross sectional study. The distance of the most prominent points of lips from S-line and Sn-Pog', and Z-angle values were measured on lateral cephalograms. Upper and lower arch widths in canine, premolar and molar regions were also measured by a digital caliper on dental casts before and after treatment. To compare the changes, paired t-test with 0.05 significance level was used. Following orthodontic treatment with four premolar extraction, dental arch widths in upper and lower arch increased in canine region (p<0.001), but it was decreased in premolar and molar regions significantly (p<0.001). It was also observed that, the lips were retracted significantly with reference to S-line and Sn-Pog' (p<0.001), and Z-angle was also increased (p<0.05). Orthodontic treatment with four first premolar extractions in class I malocclusion patients resulted in: 1.Increase in upper and lower arch width in anterior region, and decrease in posterior region. This means that, first premolars extraction in Class I malocclusions does not increase buccal corridor width, and consequently have no adverse effects on smile esthetics.2.More posterior position of the lips related to S-line and Sn-Pog' as well as increase in Z-angle leading to more straight profiles in patients.

Statement of Problems: Bacterial endocarditis is a rare disease that resulted to the death and morbidity in children and young people about 55% to 65%. Since many dental treatments can create the bacterial endocarditis, thereby antibiotic prophylaxis with appropriate treatment modaliteis by dentist is very important and necessary for prevention. The purpose of this study was to investigate the knowledge of a group of Iranian dentists about antibiotic prophylaxis guidelines for bacterial endocarditis. In this descriptive and cross sectional study, the population under consideration were the dentists participated in the fifth International Congress of Pediatric Dentistry (summer 2006), selected with simple sampling methods. The data was collected by questionnaires completed by the selected dentists. For data analysis, t-test and spierman with the SPSS 13.5 program were used. Participted in this study were 85 dentists. The results showed that, previous bacterial endocarditis, rheumatic heart disease and mitral valve prolapse with valvular regurgitation, were diagnosed by the dentists to be the most common situations which need antibiotic prophylaxis. Also the most common treatment procedures for which antibiotic prophylaxy is needed, were tooth extraction and subginginval cord respectively. More than half of the dentists (68.3%) prefer use of amoxycillin as a prophylactic medicament. Overall mean knowledge score of the dentists was 37.4±14.3. Due to the present findings to improve knowledge and attitude, it seems necessary for dentists to take participate in educational programs on the bacterial endocarditis.

Statement of problem: New Ni-Ti rotary instrument systems have been designed for ease of canal preparation in permanent teeth. Evaluation of the ability and effectiveness of such newely introduced devices in pulp treatment of deciduous teeth seems to be logic and necessary approach as well. The purpose of this study was to compare the manual (K-file) and rotary (protaper) techniques on cleaning ability and instrumentation time in deciduous molar teeth. After injection of Indian ink into root canals of 49 teeth of 56 selected deciduous molars, the teeth were randomly devided into three experimental groups (14 teeth and 42 canals in each), and two control groups (each of 7 teeth and 21 canals). Canal preparations were done manually (K-files) in group I, and by protaper rotary files in group II. In group III canals were only irrigated with normal saline, but no cleaning or irrigation of the canals were done in groups IV and V (control groups). Instrumentation time was recorded for groups I and II. After clearing procedure, canals contents were observed with a stereomicroscope at X10 magnification, and results were analyzed using T-test, ANOVA and Tukey HSD test. Mean cleaning amount of apical, midle and coronal thirds of the canals for protaper rotary files group (II) was more than that of manual K-files group (I) and normal saline group (III). The differences between groups I and II and groups II and III were statistically significant (P<0.001). Mean cleaning amount of all parts of canals for K-file manual instrumentation group (I) was more than that of normal saline group (III). Statistical difference between groups I and III was also significant (p<0.001). mean recorded instrumentation time in group II (rotary protaper group) was 70 seconds, while it was 130 seconds for manual K-file instrumentation group (p<0.001). results suggest that rotary protaper can efficiently be used for endodontic treatment of deciduous teeth.

Statement of problem: Early Childhood Caries (ECC) is one of the most prevalent and chronic diseases in children which may cause pain and dental infection, and often requires dental treatment under general anesthesia. Most researchers emphasize on complex and unknown reasons for occurrence of ECC. Children’s diet analysis in each community can be useful in assessment of diet sufficiency and the potential of its cariogeniocity. The purpose of this study was to evaluate the relationship between prevalence of the ECC and diet in children in the city of Birjand. In this descriptive, and cross sectional study, 500 children aged 24-71 month-old from Birjand were selected. In order to analyze the diet regimen of samples, 7 day diet history was recorded and compared with the United States Department of Agriculture (USDA) diet model. The samples were examined for dental caries and the association between the severity of ECC and diet was evaluated. For analyzing the results of the study Mann-Whitney, Chi-Square and Spearman tests were used. 1. The prevalence of ECC and SECC (Sever Early Childhood Caries) were found to be 83.9% and 50.2% respectively. 2. The mean consumption of the snack category was greater in boys (p=0.01). 3. The mean dmft and dmfs scores were associated with an increase in the mean consumption serving of the snack category (p=0.001(. 4. In children with recommended consumption or more than the recommended consumption serving in milk and meat groups, the mean dmfs was less than the other samples (p<0.001). Most of children had not desirable diet and the prevalence of ECC showed to be high in them.

In this case report, dental status of a boy aged eight years, referred to the pediatric department of dental school of Shiraz University of Medical Sciences is presented and explained. His main chief complaint was reduced number of the teeth. During clinical evaluation, hypodontia, and in radiographic examination, congenital missing and rootlessness of many permanent teeth were evident. The patient did not have any evidence of systemic diseases, developmental anomalies and/or syndromic defects.