Journal of Dental Medicine

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Deep bite is a major clinical problem manifested as higher than normal overbite in anterior region of the jaws. Various studies were conducted to identify the effects of using bite plan and its results. 14 subjects with deep bite were selected out of 400 students of a school who had not proximal caries and had not lost any permanent teeth with healthy periodontal condition. 8 patients were considered as case group and the 6 other as the control group. In case group, a simple labial arc with acrylic palate that caused a gap in occlusion was placed. 2 lateral radiographs were obtained both pre and post 14 months treatment period. After cephalometric analysis, due to bite plane application significant intrusion in mandibular  incisors were observed as well as elongation in both maxillary and mandibular molars.

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Normal 0 false false false EN-US X-NONE AR-SA Canine retraction to the place of extracted premolar is a basic step in the majority of orthodontic treatments. This is performed frequently by incorrect axis change of canine which moves its root anteriorly. This study is aimed to evaluate canine bodily movements by removable orthodontic appliances and describing the steps of an ideal orthodontic treatment as well as discussing important points on canine retraction. 4 patients with treatment plan of extracting first premolar and replacing the space by canine movement were selected and simple orthodontic appliance were delivered to them. Radiographic analysis showed pdl increased continuously in the side of force application which confirms bodily movement of tooth. Besides, chair side time  is less for removable appliances. Therefore, removable systems are the most desirable orthodontic treatments although there are some limitations in their application.

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Statement of Problem: The main objective of endodontic therapy is chemomechanical cleansing of entire pulp cavity and its complete obturation with an inert material. During this procedure, the failure of detection and inadequate cleaning of a canal will result in failed endodontic therapy. Therefore, the dentist must have enough knowledge of root canal morphology to treat a tooth successfully.
Aim: The aim of this study was to determine the number and type of root canals of mandibular incisor teeth.
Materials and Methods: In order to do this in-vitro, descriptive study, 68 non-carious mandibular incisor teethj collected from different clinics in Yazd, were immersed in indian ink, decalcified and cleared.

Results: It was found that 55.9% of the teeth had two separate canals that in 5.5% of them, the canals merged before' apical foramen. In 4.4% of these samples, two separate canals existed along the whole root.
Conclusion: Considering high percentage of two canals in lower mandibular incisors, during access preparation, more attempts in detection of the second canal, is emphasized.

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Statement of Problem: Radiography is the most common technique in working length determination, however, because of its limitations is not considered as an ideal technique. Its application, particularly for children due to radiation hazards, technical problems in young and unco-operative children and the superimposition of permanent teeth bud on primary teeth root, lead to numerous problems.
Purpose: The goal of this study was to evaluate the accuracy of an electronic apex locator (EAL) in working length determination of primary teeth.
Materials and Methods: In this in-vitro study 96 canals of the extracted primary teeth, with at least 2/3 of the root length remained, were investigated. There were no obstructed canal, previous root canal therapy and perforation of pulp chamber floor. All working lengths were also measured by radiography. The results of Raypex 4 and radiography were compared with actual root canal lengths determined by direct observation. The applied EAL, in this study was called Raypex 4, a new device belonged to the fourth generation (Ratio Type). The results were analyzed by Chi-Square and Pearson correlation statistical tests.
Results: The accuracy of Raypex and radiography were 61.5% and 63.5%, respectively. The differences between Reypex 4 root canal length measurements and those of direct observation were not significant (P=0.08), but such difference between radiography and direct observation was statistically significant (P=0.01). The diameter of the apical foramen (the site of canal opening) did not affect on Raypex 4 accuray (P>0.05).
Conclusion: Considering the acceptable safetyness, Painlessness, simple and rapid application and an accuracy comparable to that of radiography, the use of Raypex4 EAL for the measurement of primary teeth length is suggested.

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Statement of Problem: Porcelain restorations are susceptible to fracture and a common method for repairing is the use of silane and composite on etched porcelain. Although HF is very effective in porcelain etching but has detrimental effects on tissues.

Purpose: In this study, the effect of APF and PHA was compared with HF in porcelain etching. Also the role of silane, unfilled resin and dentin bonding in bond strength of composite- porcelain was evaluated.

Methods and Materials: In this experimental in-vitro study, one-hundred twenty porcelain square blocks (552 mm) were prepared and bonding surfaces of each sandblasted. Samples were divided into three groups. The first group (n=40) were etched with buffered HF 9.5% (Ultradent) for 1 min., the second group (n=40) were etched with Iranian APF 1.23% (Kimia) for 10 minutes and the third group (n=40) were etched with Iranian PHA 37% (Kimia) for 1 min. Ultradent silane was applied on the surfaces of half of cases in each group. On the surfaces of half of silane-treated samples unfilled resin was applied and dentin bonding was used on the surfaces of the remaining. Samples without silane were treated in a similar manner. Composite cylinder with 4mm diameter and 2 mm height was bonded to porcelain. Specimens were stored in 37°C distilled water for 24 hours and subjected to 500 cycles. Shear bond strength was measured with an Instron machine and type of fracture was evaluated using a stereomicroscope. Results were analyzed using 3 way ANOVA, Kaplan- Maier and Tukey HSD tests.

Results: Findings showed that PHA and APF roughened the porcelain surface without creating retentive micro undercuts but HF etches porcelain and creates retentive microundercuts. Ultradent silane had no significant effect on bond strength of porcelain- composite. Unfilled resin with Ultradent silane compared with dentin bonding with the same silane is more effective in bond strength of composite- porcelain.

Conclusion: Based on present study, application of Ultradent silane on sandblasted and etched porcelain with PHA or APF cannot be used as an alternative to this silane on sandblasted and etched porcelain with HF.

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Background and Aim: Determining correct working length in root canal therapy is of great importance in successful treatment. The purpose of this study was to compare the accuracy of two electronic apex locators of fourth generation, Raypex4 and Apit7, in determining working length in vivo.

Materials and Methods: In this test evaluation study performed at Dental School of Tehran University, a total of 32 single canal vital teeth planned for extraction because of orthodontic and prosthetic reasons were selected. Working length determination by each of the two electronic apex locators was performed by two different dentists. These measurements were compared with direct visual measurement after tooth extraction. The dentists working with devices and the endodontist who determined the working length of the extracted teeth as well as the statistician, all were blind regarding the results. The data were compared using binominal distribution test with P<0.05 as the limit of significance.

Results: The accuracy of actual length determination of Raypex4 was 68.8% in the limit of ± 0.5 and 83.3% in the limit of ±1. From the actual length measurements, 75.1% were within the tolerance of +0.5 to-1. The accuracy of the working length determination by Raypex4 was 68.8% within the tolerance of ± 0.5 and 84.3% within the tolerance of ± 1. Taking the tolerance of + 0.5 to -1 mm into account, the accuracy of the instrument was about 78.8%. The accuracy of actual length determination of Apit7 was 65.7% in the limit of ±0.5 and 78.3% in the limit of ±1. Compared to the visual length determination, 78.8% of the actual length measurements were within the tolerance of +0.5 to-1. The accuracy of the working length determination was 62.6% within the tolerance of ±0.5 and 81.3% within the tolerance of ±1. Taking the tolerance of + 0.5 to -1 mm into account, the accuracy of the instrument was about 75.1%.

Conclusion: Raypex4 and Apit7 had similar accuracy in determining the actual length. However, they still can not replace the routine methods of actual length determination.

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Background and Aim: Mineral Trioxide Aggregate (MTA) is a material used in many endodontic problems. Recently a number of studies, have reported that Portland Cement (PC) and MTA have similar physical, chemical and biologic properties. In addition, a material known as Root MTA which is produced in Iran has been claimed to have similar properties to Pro Root MTA. If these claims are true, possible use of PC and Root MTA in clinic instead of Pro Root MTA will be quite cost effective. The aim of this study was to investigate the toxicity of Pro Root MTA, Root MTA and Portland Cement on L929 mouse fibroblasts.

Materials and Methods: In this experimental study 0, 4, 24 hours and 7 days' extracts of materials were transferred to cell culture plates containing L929 fibroblasts. After 24 hours incubation, cells were stained by Neutral Red (NR), and optical density (OD) of each cell was read with ELISA reader. Data were analyzed using Tukey HSD and one way analysis of variance. P<0.05 was considered as the level of significance.

Results: In all surveyed groups and negative control group, at all time points separated cells from the base of the well were round. Refraction which is a characteristic of cellular death was not observed, whereas the separated cells from the base of well in positive control group showed refractional characteristic.

Conclusion: Based on the findings of this study Pro Root MTA, PC and Root MTA have the same biocompatibility. PC seems to have the potential to be used in the same clinical situation as MTA. However in order to replace MTA with these less expensive materials more in vitro and in vivo studies are suggested.

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Background and Aim: Image distortion is one of the major problems in panoramic radiography. Horizontal and vertical correction factors could be determined for more efficient clinical applications. The purpose of this study was to determine horizontal and vertical correction factors in panoramic radiography.

Materials and Methods: In this test evaluation study in which an asymetric mandibular phantom was constructed by plexiglass and aluminium as soft and hard tissue equivalents. The right half was slightly shorter than the left half. Steel markers were installed to make vertical and horizontal measurments possible.The length of the markers as well as the intermarker distances were measured by Mitutoyo digital micrometer which was accurate within ±0.05mm. The phantom was then positioned in PM 2002 cc proline (Planmeca, Finland) panoramic machine and panoramic images were obtained. 8 times for each half of the phan. The same length and inter marker distances were measured on digitized panoramic images by Cygnus software, which was accurate whitin ±0.01 mm. Magnification and correction factors were determined for the vertical and horizontal dimensions in each region of pantomograms.

Results: The mean vertical correction factor was 0.77±0.02 (range: 0.75-0.80) in the right and 0.77±0.05 (range: 0.75-0.85) in the left half jaw. The mean horizontal correction factor was calculated as 0.98±0.15 (range: 0.76-1.18) in the right and 1.02±0.14 (range: 0.90-1.25) in the left half jaw.

Conclusion: Dissimilarity of vertical and horizontal correction factors among left and right half jaws and also in different regions of a half jaw is relatively considerable. However, a constant correction factor, specialy in horizontal aspect, could not be applicable. Comparing with horizontal correction factors the vertical correction factors showed less variations between different regions as well as different samples.

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Background and Aims: Root canal obturation is of great importance in root canal treatment. Its purpose is to eliminate microleakage, re-entry and growth of micro-organisms in the root canal system. The aim of this study was to compare coronal salivary microleakage in obturated root canals using lateral compaction, single cone gutta-percha and System B vertical compaction methods.

Materials and Methods: In this in-vitro study, 80 single rooted, human extracted teeth were randomly divided into 3 experimental groups (n=20) and 2 positive and negative control groups (n=10). The specimens in each experimental group were obturated by using cold lateral compaction, single cone obturation, or continuous wave of condensation (system B). After that, coronal saliva leakage was evaluated. Data were analyzed using Survival analysis and Log-rank test.

Results: The results showed that all the specimens in the positive control group showed evidences of leakage during the first 7 days of study. None of the specimens in negative control group showed leakage during the 30-days period of the experiment. Survival test and log-rank test showed that at the end of the 30 days, there was significantly less resistance to coronal salivary leakage in single cone method compared with lateral compaction (P=0.039) and continuous wave of condensation (P=0.019) groups. No significant difference was observed between lateral compaction and System B vertical continuous method (P=0.564).

Conclusion: Based on the results of this study, lateral compaction and system B groups showed higher resistance against the coronal leakage compared with single cone group.

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Background and Aims: The present study was designed for evaluation of bovine demineralized bone matrix (DBM) in healing process of bone defects and comparison of bovine DBM (xenograft) and human DBM (allograft) which is used clinically.

Materials and Methods: Seven male white New Zealand rabbits were used in this study. The incision was made directly over the midsagital suture of the parietal bone. Then 3 bicortical defects were created with trephine bur No.8 (8mm diameter). The defects were randomly filled with graft materials. One of the defects was left without any graft in all samples (as a control defect). The amount of bone formation was evaluated 3 months after surgery histopathologically. The data were analyzed using Friedman test, and when P-value was less than 0.05, the pair wise group comparison were performed by Wilcoxon (Boneferroni adjusted) test.

Results: Statistical analysis showed that there was a significant difference between bovine DBM group with control group (P=0.03). Furthermore, human DBM group was significantly different from control group (P=0.02). However, the difference between bovine DBM group and human DBM group was not statistically significant (P=0.87).

Conclusion: The results of this study showed the satisfactory bone healing in rabbit parietal bone defects filled with bovine DBM. The amount of healing in these defects was similar to bone defects which were filled with human DBM that is used clinically.

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Background and Aims: Evaluation is a continuous process which is necessary for improvement of students learning and planning for required changes to obtain the educational objectives. The aim of the present study was to assess students' perspective on the achievement of the educational objectives of the Community Oral Health and Periodontology Departments using the CIPP model of evaluation.
Materials and Methods: A cross-sectional survey has been conducted using a questionnaire consists of four domains as introduced in the CIPP model of evaluation (Context, Input, Process and Product). Two groups of senior dental students of the dental school of Tehran University of Medical Sciences were approached. Data was collected anonymously and was analyzed with non-parametric Mann-Whitney test using the SPSS statistical package.
Results: The response rate was 67.7% for year 6 and 87.5% for the year 5 students. Respondents considered material presented in Periodontology Department more relevant and in need for their future career. However, teaching skills and motivation of the educators in Periodontology Department was considered inadequate. 67% of students reported having problem with material taught in Periodontology Department. Overall, significant difference in domains of Context and Process was observed between two departments (p<0.05). In the output domain students rated their clinical and theoretical ability "weak" in relation to splint, implant, management of acute gingivitis and electrosurgery compared with other topics which rated "good". Students considered their ability in using the principals of Evidence-Based Dentistry moderate.
Conclusion: The evaluation of the educational achievements of the two departments (COH and Periodontics) using CIPP model of evaluation showed that there is significant difference in two domains (Context and Process). In those topics which achievement was reported weak the revision of teaching methods is recommended.
Key Words: Education dental Program evaluation Self-evaluation

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Background and Aims: Marginal seal in class V cavity and determination of the best restorative material in reducing microleakage is of great concern in operative dentistry. The aim of this study was to evaluate the effect of load cycling on the microleakage of low shrinkage composites compared with methacrylate-based composites with low shirinkage rate in class V cavity preparation. Marginal integrity of these materials was assessed using scanning electron microscope (SEM).

Materials and Methods: In this in vitro study, class V cavity preparations were made on the buccal and lingual surfaces of 48 human premolars and molars (96 cavities). The specimens were divided into four groups each containing 12 teeth (24 cavities): group 1 (Kalore-GC+ G-Bond) , group 2 (Futurabond NR+Grandio), group 3 (All Bond SE+ Aelite LS Posterior), group 4 (LS System Adhesive Primer & Bond+Filtek P90). All the specimens were thermocycled for 2000 cycles (5-50^oC). In each group, half of the specimens (n=12) were subjected to 200,000 cycles of loading at 80 N. Epoxy resin replicas of 32 specimens (4 restorations in each subgroup) were evaluated using SEM and the interfacial gaps were measured. Finally, the teeth were immersed in 0.5% basic fuchsin dye for 24 hours at 37⁰C, then sectioned and observed under stereomicroscope. The data were analyzed using Kruskal-Wallis and Mann-Whitney U tests and the comparison between occlusal and gingival microleakage was made with Wilcoxon test.

Results: Within unloaded or loaded specimens, there were no significant differences in microleakage among four groups on the occlusal margins (P>0.05). But there were statistically significant differences in microleakage between silorane and Aelite on the gingival margins (P<0.05). No statistically significant differences were found between the microleakage of the loaded and unloaded groups on both occlusal and gingival margins for all materials (P>0.05).

Conclusion: Silorane did not perform better than the conventional low shrinkage methacrylate-based composite in terms of sealing ability (except Aelite). Cyclic loading did not increase the extent of leakage in any groups.

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  Background and Aims: Along with the advances in dental materials and invention of new techniques for ceramic producion, the demand for the beauty and matching restoration’s color with patient’s natural teeth is growing. Nowadays, zirconia systems are the focus of attention. Despite their strength, one of the problems with such systems is the high opacity and failing to provide the favored color. Considering few studies about the influence of shading on Zirconia, the purpose of this in vitro study was to evaluate the effect of different shading of zirconia-based ceramics on the biaxial flexural strength .

  Materials and Methods: In this in vitro experimental study, Rainbow (Dentium, Korea) zirconia-based ceramics (the diameter of 15mm and 1mm in thick) were divided into four groups of 10 specimens. According to Vita shade guide system and manufacturer’s time recommendations (3 seconds), three groups of disc specimens were shaded to A3, B3 and D3 colors and other ten specimens remained uncolored as control group. The biaxial flexural strength test of discs was evaluated and the elements’ composition of colors was detected by Energy Dispersiue X-ray Microanalysisd (EDX). Finally, data were analyzed using one-way ANOVA and Post-hoc tests.

  Results: The biaxial flexural strength in non colored specimens, A3 shaded discs, B3 shaded, and D3 shaded specimens were determined 1061.93, 819.16, 1100.10, and 825.48 MPa respectively which was statistically significant among groups (P<0.001). The statistical analysis revealed that the highest strength in B3 and non colored groups which were significantly higher than A3 and D3. EDX analysis showed significant differences among different colored compositions.

  Conclusion: The biaxial flexural strength of zirconia cores are affected by shading and the specific selected color.

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  Background and Aims : According to the common application of non-metal prefabricated posts in dentistry and lack of enough information about the stress distribution in the root canal walls by these posts, this study was performed to compare the effect of two simple taper and double taper posts on the stress distribution on root canal walls by photo elastic method .

  Materials and Methods: The design of this study was experimental in photoelastic system. The posts, used in this investigation, were double taper and simple taper fiber posts with 0.9 mm diameter and 20 mm length and epoxy resin. First two photo elastic models with tooth dimensions were fabricated and the posts were placed inside the model. Then the core of the each post was fabricated on the model. Each models were loaded in polariscope and the formed fringe order colored ring were photographed.

  Results: In 100 N, 90 degree angle loading in cervical and apical fringe order showed 2.50 and 1.39 in simple taper posts and 1.39 and 2.35 in double taper post. In 150 N, 30 degree angle loading in cervical and apical fringe order showed 4 and 2.65 in simple taper posts, and 4 and 2.5 in double taper post.

  Conclusion: In the vertical and oblique loads, double taper fiber post showed better stress distribution than that of simple tapered posts.

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  Background and Aims: Hydroxyapatite coating has allocated a special place in dentistry due to its biocompatibility and bioactivity. The purpose of this study was to evaluate the relation between the hydroxyapatite thickness and stress distribution by using finite element method.

  Materials and Methods: In this paper, the effect of hydroxyapatite coating thickness on dental implants was studied using finite element method in the range between 0 to 200 microns. A 3D model including one section of mandible bone was modeled by a thick layer of cortical surrounding dense cancellous and a Nobel Biocare commercial brand dental implant was simulated and analyzed under static load in the Abaqus software.

  Results The diagram of maximum von Mises stress versus coating thickness was plotted for the cancellous and cortical bones in the range between 0 to 200 microns. The obtained results showed that the magnitude of maximum von Mises stress of bone decreased as the hydroxyapatite coating thickness increased. Also, the thickness of coating exhibited smoother stress distribution and milder variations of maximum von Mises stress in a range between 60 to 120 microns.

  Conclusion: In present study, the stress was decreased in the mandible bone where hydroxyapatite coating was used. This stress reduction leads to a faster stabilization and fixation of implant in the mandible bone. Using hydroxyapatite coating as a biocompatible and bioactive material could play an important role in bone formation of implant- bone interface.

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  The need to identify and determine the age of the unidentified dead person s or accident victims of natural disasters is clear. Also, some remedial measures in the field of orthodontics and pediatric dentistry depend on knowing the patient’s physiological age. Previous studies suggested that dental age have a good correlation with physiological age more than skeletal or o ther common methods of age determination. Among the various methods used to determine dental age , dental radiography provides wide facilities for clinicians. Being noninvasive and the ability of performing the technique on live subjects as well as simplicity and low cost and reliable results , have led researchers to investigate further on that . The formation and calcification process of teeth and changes during aging has been regarded by many, leading to introduce various methods in which the field. In this study, 36 related articles were achieved by searching PUBMED, Science Direct and Google Scholar resources and discussed. Provided what diversified means of determining age using dental radiographs is encouraged , it is recommended to be not restricted to use only one of the methods because the multilateral approach is more reliable.

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  Tehran University of Medical Sciences, Tehran, Iran ( mirahashemi@tums.ac.ir )

  Background and Aims: Nowadays patients refer to orthodontist for issue such as dental crowding and other aesthetic problems. The aims of this study were to evaluate the relationship between some of mandibular anatomical landmarks and dental crowding in the patient with skeletal Cl II due to mandibular deficiency.

  Materials and Methods: 108 cases have been randomly selected out of patients with mandibular related Cl II problem associated with lower incisor crowding, out of orthodontic patient department of Tehran university of medical sciences. ANB, SNB, mandibular discrepancy, gonial angle, Sn-Go-Gn and IMPA was evaluated out of the data. Lateral cephalograms were used for this matter. The correlation between variables was evaluated by correlation test and after reviewing the data was analyzed using Normality test, the Pearson correlation coefficient was used for normally distributed variables.

  Results: Corpus-ramus length ratio had a significant relationship with dental crowding (P≤0.05) but there was no meaningful and significant relationship between other facial landmarks ( P = 0.26 ).

  Conclusion: there seems to be a slight relationship between facial landmarks and dental crowding in lower incisors. But further case control and clinical studies may be helpful in achieving more reliable data.

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  Background and Aims: Porcelain restorations are often ground for clinical adjustment and this removes the surface glaze layer and introduces flaws that can grow in wet environments due to stress-corrosion, reduce the strength of porcelain and limit restoration lifetime. The aim of this study was to introduce some surface treatment methods to control the flaws of ceramic restorations external surface and improve their strength.

  Materials and Methods: 40 feldspathic discs were prepared and divided into 4 groups (n=10): not indented (group 1) and others indented by vickers with 29.4 N and received different treatments: no treatment (group 2), polished (group 3) and polished-silane-resin (group 4). Biaxial flexural strength of discs was tested after water storage. Data were analyzed using one-way ANOVA .

  Results: The mean flexural strength of specimens in group 1 (134.49±12.60), 2 (94.81±15.41), 3 (89.20±16.22) and 4 (80.67±12.01) were measured. Group 1 (not indented) revealed significantly higher strength (P<0.001) than that of indented groups (2, 3 and 4) . There was no significant difference between group 2 (no treatment) and 3 or 4 (treated) and between treatment methods (3 and 4) (P=0.136).

  Conclusion: The strength of porcelains is dependent on presence of cracks. With the limitations of this study, none of the treatment methods could strengthen the cracked ceramic.

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