مجله تحقیق در علوم دندانپزشکی
سال ششم شماره 1 (پیاپی 19، بهار 1388)

i ncreasing esthetic demands in patients have led to increasing use of ceramic as a restoration. Meanwhile the bond strength of ceramic to dention is a challenging factor. This study aimed to compare the effect of 3 different resin cements on shear bond strength of porcelin to dentin. Thirty freshly extracted bovine incisors were used for this investigation. Following extraction and cleaning, teeth were stored in a 0. 2% Thymol solution for 48 hours and then randomly divided in to 3 groups of 10 each. Teeth underwent a 2mm preparation on the buccal surface in order to expose fresh dentin. Porcelain tubes, 3mms in diameter and 3 milimeters in height, were then bonded to the dentin using RelyXARC, Nexus, and Punavia F2 samples were then light – cured for a total time of 120 seconds (40 seconds for each directions) using Coltolux 2/5 USA light-curing unit with an intensity of 400 mw/cm. Two Samples were then stored a temperature of 37ْC for 24 hours and finally thermocycled (500 times +5__+55). Then, They were for shear bond strength with Zwick with a chisel – like shearing device till fracture occurred at 0. 5 mm/min cross head speed. Shear bond strengths in Mpa was as follows’: Mean Standard deviationRelyX ARC 3. 56 ± 0. 82Panavia F2 6. 09 ± 0. 54Nexus 4. 46 ± 0. 59 Panavia F2 revealed a significantly higher shear bond strength compared to the other groups. Nexus demonstrated a higher shear bond strength compared to RelyX ARC but this difference was not statistically significant.

Calcium hydroxide plays an important role in endodontics by its ability to induce hard tissue formation, its antibacterial action, and its tissue dissolving capability. Different vehicles have been added to calcium hydroxide in an attempt to enhance its antimicrobial activity, biocompatibility, ionic dissociation, and diffusion. The purpose of this study was to investigate the efficacy of various calcium hydroxide pastes against enteroccocus faecalis in vitro.Method and Material:: A total of 20 blood agar plates were prepared for this experimental study. Five holes were made in each plate. Three experimental pastes (calcium hydroxide / chlorhexidine, calcium hydroxide / saline, calcium hydroxide / xylocaine) were placed in 3 holes. Ampicillin and distilled water were placed in the other 2 holes as positive and negative controls. Plates were stored room temperature for 2 hours and then were incubated at 37 degrees centigrade for 48 hours. The antimicrobial effect was determined by ADT method. Blood agar plates were infected with pure enteroccocus faecalis suspensions. The diameter of growth inhibition was measured and recorded after incubation. Statistical analysis was performed using the one-way ANOVA and LSD tests.In all plates all 3 experimental pastes and ampicillin showed growth inhibition. Mean diameter of growth inhibition was the greatest for The ampicillin group. The negative control showed no growth inhibition. The growth inhibition for calcium hydroxide / chlorhexidine was significantly more than the other two groups (P< 0.05).The growth inhibition between calcium hydroxide / saline and calcium hydroxide / xylocaine was not significant.The antimicrobial properties of calcium hydroxide can be influenced by the vehicles used to make the paste form. Based on the results of this study, calcium hydroxide / chlorhexidine is a better vehicle than calcium hydroxide / saline and calcium hydroxide / xylocaine to improve calcium hydroxide antimicrobial properties.

Canal preparation is one of the key steps in root canal therapy procedures.it requines accurate working length and initial file determination. The aim of this study was to detect the effect of preflaring usinvy Gates-Glidden drills on the working length changes in resin blocks and initial file size in mesio-buccal canals of mandibular molars in resin blocks Preparing standard access cavities were made in 30 molars with a curvature degree of 20-40 in the mesial roots. The largest k- file that could passively negotiate the apex while bound to The canal walls was selected as the initial file before and after performing preflaring with drills.A 25 mm k -file # 8 was inserted to its end in forty resin blocks with 30 Curvatures. The overextended segment was measured with stereomicroscope before and after preflaring and compared Adobe Photoshop 6 software.The paired t test and Willcoxon signed rank tests were the statistical analysis methods used respectively.Preflaring with Gates Glidden drills proved to significantly (p<0.001) decrease the working length, (abyrage 0.36 mm).Initial file size in 40% of the cases increased up 2 ISO sizes larger. With regard to advantages such as effective irrigation, elimination of coronal dentin, larger initial file size gaining straight. line access,and reduced extruded debris, routine preflaring is recommended.This study showed that SNA was decreased 0.38±0.77 (P<0.01), SNB was increased 1.64±1.38 (p<0.01). Nasolabial angle was decreased 2.63 ±8.06 (p<0.09), Mentolabial angle was increased 8.14±8.52(P<0.001) upper and lower lip length was increased 0.34±2/42 p<0.8, 3.59± 3.32 P<0.001 respectively.

This invitro study compared the effect of root canal irrigants on long _ term apical seal.Methods and Materials:First, freshly extracted human maxillary centrals and canines were irrigated with 1% Nacio.Then they were rinsed with distilled water. After that, their crowns were removed at the CEJ.Then the teeth were divided into two test and two control groups.Each test group had 30 teeth and each control group had 5 teeth.The first test group was instrumented to a # 40K MAF using the step back technique and irrigated with 2.5% sodium hypochlorite and Flared up to # 70.The second test group was instrumented to a # 40k MAF using stepback technique and irrigated with 0.2 % Chlorhexidine and shaped up to # 70.The positive control group was instrumented to a # 40 k MAF using stepback technique and irrigated with sterile saline and shaped up to # 70 All test groups were dried with paper points and were filled with AH26 sealer and gutta percha using lateral condenstion technique. and stored at 370 for 6 months in steile saline.The root surface was coated with nail varnish (except at the apex), the negative control group was coated completly. Then they were placed in 2% methylene blue dye solution and centrifuged.The roots were sectioned longitudinally to determine the mean levels of dye pentration in each group. Statistical analysis of the data showed that there significant differences between the test groups.(P<0/05). However, the leakage of chlorhexidine group was more than hypochlorite group.

Increased level of CRP which is one of the acute phase reactive proteins, besides increasing risk of cardiovascular disease can indicate extravascular inflammation. Decreasing the level of CRP and other inflammatory factors reduces the risk of cardiovascular disease. There are controversies about the effect of phase one periodontal treatment on serum CRP level. This study was aimed to ascertain if phase one periodontal treatment could modify serum CRP level in patients with moderate to severe periodontitis. In this clinical trial study(before & after treatment) 45 patients with moderate to severe periodontitis participated. Plaque index, pocket depth, attachment loss, bleeding on probing and serum CRP were determined. Then, phase one periodontal treatment were accomplished for all subjects. After 2 months, the patients were visited again and were rechecked. Effects of treatment were assessed by Paired-T test and Wilcoxon Sing Test. The study was performed on 30 patients in the age of 53.3±7.1.thirteen were males and 17 were females. Pocket depth was reduced %25.07 in control group and 16.26% in cases CAL was gained 20.9 % in control group and 21.42 % in cases, HbA1c in the control group was reduced from 6.2%±1.01 to 6.03%±0.92 (P<0.2). And changed from 6.3%±1.17 to 4.8%±0.92 in the case group, which means the reduction about 23.8% and was statistically significant (p<0.001).Despite effective phase one periodontal treatment and improvement of periodontal parameters, there was no influence on serum CRP level.

Most dentists extract wisdom teeth. The complications and costs of this procedures, different ideas concerning the need to remove of these teeth, was the purpose of this study. Methods and Materials: Two hundred patients had at least one impacted wisdom tooth in the mandible. After clinical and radiographic examination, factors such as: smoking, degree of eruption, type of impaction, periodontal pocket depth, history of pericoronitis were recorded. The results were analyzed with SPSS software and Chi square and odds ratio tests.

After 3 years follow - up, 58 teeth (29%) were extracted. No correlation between the history of pericoronitis at the start of the study and incidence of removal was seen.

the need for prophylactic removal of mandibular impactions is not warranted. We advise more research in this matter.

The purpose of this study was to evaluate and compare the cytotoxicity of three dentin bonding systems, (4 th, 5 th and 6 th generation of DBAs) on L929 cell line. Thirty human premolar teeth were included. Class I cavity preparations were cut on occlusal surfaces. After crown separation, a flat dentinal surface was provided and RDT (remaining dentinal thickness) was adjusted at 0.5 mm and 1.5 mm in half of the samples respectively. Then, cavities were treated in three groups with experimental DBAs: Group 1: Scotch Bond Multipurpose, Group 2: Excite, Group 3: AdheSE. Blue inlay wax sealed the cavities. Crowns were immersed in culture medium for 24 hours and the cytotoxicity of the resultant toxic medium was measured both quantitatively with MTT assay and qualitatively with an inverted light microscope in 4 serial dilutions. Data were analyzed with ANOVA and Tukey`s test at 95% significance level. Although morphologic cell changes were seen from mild to severe in serial dilutions, but MTT assay determined that only in neat dilution, cell changes were significantly different from controls. Besides, no significant differences were found between the three experimental DBAs regarding cytotoxic effect on L929 cell line. Considering the limitations of an in vitro study, if the RDT is less than 0.5 mm in Vivo, regardless of the type of DBA, destructive cellular changes in pulp tissue can be expected.

It is said that more than 70 percent of communication between people is non-verbal.This study was carried out to evaluate the non-verbal communication of dental students.Methods and Materials: A descriptive single blind study was designed in which 334 dental students in 8th and 12 th terms, participated. Sampling method was sequential and the questionnaire was composed of 10 standard items. The chi -square test was used for data analysis. Overall score of the students was 61.3+ 11.8. The highest score was related to eye-contact(%84.4) and the lowest one to chair level (%45.8) followed by acceptance(%48.8) and tilting toward the patient (%49.7).Non-verbal communication of the dental students is not enough for their profession and needs to be improved by related courses in that field.

Working length determination in endodontics is very important and conventional radiography is an essential auxillary tool. Because of its limittion such as the time taken for developling, the dose of radiation exposure and with regard to development of technology, in order to overcome these problems, the RVG has been introduced.The aim of this study is to compare the accuracy of conventional radiography and RVG for measuring working length in curved canals.Methods and Materials: In this study 45 extracted teeth with canal curvature ranging 250- 400 were selected. Teeth mounted and files 15 k – type Maillefer were placed in selected canals. Then RVG and conventional radiography were taken with parallel technique. File length was estimated in the image of conventional radiography and RVG with 2click, 5click, 6click and unlimited clicks. Then these values were compared with the true values. By analysis of pair samples, no signifant differences were seen between conventional radiography and RVG utilizing 5click and 6click with true canal length and with each other. But, RVG utilizing 2click and unlimited clicks show lower and greater values from true value respectively. The results of this study showed that, advantages such as low dose radiation exposure, less time taken for developing film, reduction of pollution, ability of image processing and also equivalence with conventional radiography, the use of RVG for working length determination is suggested.

The relation between tooth size and lower anterior crowding has been studied previously, but remains inconclusive. The aim of this study was to investigate the relation between tooth size and lower anterior crowding.: This case – control study was performed on dental casts of sixty 13 to 15 year –old school children divided in 2 groups. Group I consisted of 30 dental casts of patients with 5mm or more crowding in lower anterior region as the study group and group II consisted of 30 dental casts of subjects without crowding as controls. Maximum MD tooth size of four lower incisors were measured and recorded to nearest 0.1mm. Comparison between groups were performed using the T- test. The deviation of tooth size was 24.86± 1.77 mm and 23.16± 1.25 mm in crowded and non crowded subjects respectively. Statistically there was no a significant differences between two groups when comparedThis study shows that the tooth size is not the only determining factor in the origin of crowding. Other factors can be associated with malalignment

Today vaccination is considered an essential and mandatory method for preventing HBV infection and transmission. The aim of this study was to evaluate the prevalence of HBV and ness effective of hepatitis B vaccination in vaccinated dentists in Hamadan.In this descriptive, cross – sectional study 137 dentists in Hamadan were evaluated; 14 subjects were excluded due to incomplete vaccination. Five cc of venous blood was taken and the Elisa method was used for the evaluation of HBSAg and HBSAb titer Three point six percert of dentists were HBSAg positive. HBSAb was detectable (>10 IU/cc) in 91.1% of dentists.The low rate of HBSAg+ patients and high rate of HBSAb+ after complete vaccination (> 91.1%) was in with the global rate (90-95%) and shows that vaccination against HBV could have a significant role in prevention of disease and transmission of hepatitis B infection.]

According to the importance of the harmony of teeth size in establishing a correct occlusion with appropriate overjet, overbite and molar and canine class I relationship, also considering the insufficient and contradictory previous studies in such a field, the goal of the current study was comparing the Bolton ratio between different malocclusion groups. The Method of this study was descriptive and cross sectional. For this study 120 cast of orthodontic patients with permanent dentition were selected and divided to four equal malocclusion group (Cl I, Cl II div1, Cl II div 2, Cl III). There were 30 patients in each group. The largest mesiodistal width of the teeth of each cast was measurded by caliper accurate to 0.1 mm from first left molar of the upper jaw to the first right molar of the lower jaw and Bolton ratio were calculated for each specimen. Then ANOVA statical analysis and chi-square test were done on data. Bolton overall ratio in patients with class III malocclusion was greater than patients with class I and II malocclusion and this index in patients with class I malocclusion was greater than patients with class II malocclusion. But there were no significant differences between class II div1 and class II div2. Regarding the Bolton anterior ratio this index in patients with class III malocclusion was greater than class I and II, and in patients with class I malocclusion was greater than class II div1. But there were no significant differences between class II div1 and 2 and between class I and class II div2. The prevalence of discrepancies about Bolton overall ratio was 44.2% and about Bolton anterior ratio was 60% in sample population. Findings show highly prevalence of Bolton discrepancies in sample population. That means we should pay more attention on teeth size before orthodontic treatment