JOURNAL OF ISLAMIC DENTAL ASSOCIATION OF IRAN (MAJALLAH-I-DANDANPIZISHKI)
Year:2009 | Volume:21 | Issue:1 (70)|Papers Count:12

Background and Aim: The ability to produce multiple accurate casts from a single impression has been evaluated in a few impression materials. The aim of this study was to evaluate the effect of multiple casting in specific time intervals with three different elastomeric impression materials, on the dimensional accuracy.Materials and Methods: A stainless steel model composed of two dies with precut molar and premolar teeth were used in this study. The bigger die had a notch to reproduce undercut in order to study the elastic recovery. Seven impressions were made from this model by each of the following impression materials: Correct plus, Panasil (addition-cured silicones) and Speedex (condensation-cured silicone) according to manufacturer's instructions. The 21 impressions were poured in 30, 90, 150 minutes and 24 hours after impression taking. The stone casts were measured in six dimensions by an optical traveling, high precision (0.001 millimeter) microscope. The mean dimensions were compared with each other and the stainless steel model. For statistical analysis, Two-way ANOVA and Post Hoc tests were used to determine the significance levels.Results: There were significant changes in most of the dimensions between the metal model and the first cast, but these changes were within the acceptable limits, according to ANSI/ADA Specification No.19 for impression materials. No significant difference was observed between almost all of the dimensions of the second, third and fourth casts when compared with the first cast of each impression material (P>0.05). The only significant difference was detected between the fourth cast and the first cast of Speedex in one dimension. Conclusion: Based on these results, four casts from correct plus and Panasil as well as three casts from Speedex could be considered as acceptable from clinical stand points.

Background and Aim: There is no bonding between amalgams and restored cavity walls. Therefore, these restorations are prone to leakage despite the deposition of corrosion products. The aim of this in vitro study was to evaluate the effectiveness of three cavity liners in reducing micro leakage of class V amalgam restorations. Materials and Methods: Sixty-eight extracted intact human molar teeth were selected. Class V cavity preparations were performed in all teeth and they were randomly divided into four groups. Group one was used as a control group (no liner), and the rest were Varnish, Resin Cement (Panavia F), and Light-cured dentin bonding agent (Single Bond) groups. Oralloy amalgam was condensed into the prepared CI V cavities. All teeth were immersed in distilled water at 37°C, for 24 hours. All restorations were subjected to 1000 thermal cycles at 5-55 degrees centigrade. For micro leakage test, all teeth were immersed in 0.5% Basic Fuchsine and sectioned. Dye penetrations were evaluated by stereomicroscope. The collected data were analyzed statistically by Kruskal-Wallis and Bonferroni test. Results: The results showed significant differences between four groups (P< 0.05). Control group showed the maximum and Panavia group revealed the minimum micro leakage. There was no significant difference between Panavia and Single Bond groups. On the other hand, no significant difference (P>0.008) was observed between occlusal and gingival margins in the control, Single Bond and Panavia groups. Although, the difference was statistically significant in varnish group (P=0.002). When compared with control group, the dentin bonding agent, varnish and cement resin groups demonstrated significantly decreased micro leakage at the enamel margin (P=0.0001).However, when compared with varnish and control group, the dentin bonding agent and cement resin groups demonstrated significantly decreased micro leakage at the cementum margin (P<0.008).Conclusion: Findings of this investigation clearly demonstrate the advantage of using lining materials in amalgam restorations. Therefore, we can conclude that such materials may significantly increase the sealing ability and decrease the micro leakage in Class V amalgam restorations.

Background and Aim: The fiber diameter of fiber post used in reconstruction of endodontic ally treated teeth is one of the controversial factors in root fracture resistance. The aim of this study was to evaluate the effect of three different diameters of quartz fiber posts on root fracture resistance.Materials and Method: This in vitro study was conducted on 30 mandibular premolars that were sectioned from CEJ. They were endodontic ally treated and randomly assigned to 3 groups A, B, C (n=10). Post spaces were prepared and D.T Light-Post™ with three different diameters (0.8, 1, 1.2 mm) was cemented respectively in each group with dual cure resin bonding and resin cement Panavia F 2.0. Composite resin cores were built up using a preformed polyester matrix. Specimens were embedded in acrylic resin blocks with a layer of elastic polyether Impergum around roots as PDL. A compressive load at a crosshead speed of 1 mm/min was applied axially to the central fossa of each specimen using a Universal Testing Machine, until root fracture occurred. Data was analyzed using one-way analysis of variance (ANOVA).Results: Mean fracture load was 1010 ±250.95) N for group A with 0.8 mm post diameter and 934.4 (±95.18) N for group B with 1 mm post diameter and 1001 (±301.42) N for group C with 1.2 mm post diameter. We could not detect any statistically significant difference in root fracture resistance among the three groups. Conclusions: According to the findings of this study, with larger fiber posts the root fracture resistance is higher and they can provide more stability for core material, although, group differences in fracture resistance were not statistically significant.

Background and Aim: Topical and systemic antimicrobials are widely used in dental practice. Likewise, antimicrobials may be used in order to reduce the count of oral pathogens before oral surgery in immune compromised patients or other high risk patients as well.Propolis is a wax- or resin-like substance that is collected by bees from fresh flowers, or other botanical sources, and used to reinforce the structural stability of the hive, acting as a barrier in preventing diseases and parasites from entering the hive. Given that there are differences in Propolis property produced around the world, the aim of this study was to compare the antimicrobial effects of the Propolis produced in Hamedan province, Iran, with Nystatin (antifungal drug) and Chlorhexidine (antibacterial mouthwash).Materials and Methods: By using whole technique, the antimicrobial effect of 30% ethanol extract of Propolis was demonstrated against S. mutans, C. albicans and A.a.commitans. The antimicrobial effects of Ethanol-extract of Propolis and Chlorhexidine solution were evaluated at eight different times against S.mutans, C.albicans and A.a.commitans. The 70° ethanol was used as control.Results: The microorganisms under investigation in this study revealed close susceptibility to various concentrations of Propolis extract, and the complete clear zones revealed remarkable effect. For other bacteria, different degrees of susceptibility to Propolis were observed.Conclusions: Based on these findings we may conclude that 30% ethanol extract of Propolis is very effective on oral pathogenic microorganisms (such as Streptococcus mutants, Candida albicans and Actinobacillus a. commitans).

Background and Aim: Fixed splinting of abutment teeth can alter the stress distribution characteristics of removable partial denture (RPD). However, periodontally compromised abutments may complicate free end RPD treatment plans. The purpose of this study was to determine the effects of fixed splinting of periodontally compromised abutments on load distribution in free end RPD.Materials and Methods: Three-dimensional finite element models were designed for mandibular first and second premolars including their PDL and surrounding bony structures. In the first model the teeth had no periodontal involvement; in the second model, the first premolar was healthy, the second premolar had periodontal involvement (C/R=1); and, in the third model both teeth had periodontal involvement (C/R=1). Likewise, before and after fixed splinting, situations were defined for each model. The Von misses stress in surrounding bone was analyzed after applying 50 N loads on the specimens. Results: In all three models the maximum Von misses stress before splinting were found to be in the apical area of teeth and the minimum was detected near the mesial crest of first premolar and distal crest of second premolar. After splinting the teeth together, a stress reduction was observed in the interdental crest areas; while in model 1 and 2, increase in the stress was observed in apical areas. The greatest remedy was demonstrated in model 2 where a periodontally compromised tooth was splinted to a healthy one.Conclusion: Fixed splinting of periodontally compromised teeth can reduce the stress concentration in the interdental crest areas and it can improve the stress distribution in the surrounding bone.

Background and Aim: Elimination of root canal microorganisms is an important step in endodontic treatment. Each one of currently used medicaments has problems such as microbial resistance and tissue toxicity. Therefore, research is still needed to identify better alternatives. Propolis, as one of the honey bee products has been the focus of attention by many investigators in order to evaluate its biological properties. The aim of present study was to compare the activity of Calcium hydroxide and Propolis against lactobacillus, Enterococcus faecalis, Pepto-streptococcus and Candida albicans.Materials and Methods: This experimental study was conducted to evaluate antimicrobial activity of ethanol extract of Propolis and calcium hydroxide powder mixed with saline solution. Agar diffusion test and dilution methods were used to compare the results. There were separate plates to control diffusion of two substances in agar and antimicrobial activity of solvents. Figures about diameter of inhibition zone and minimal inhibitor concentration (MIC) and minimal bacterial concentration (MBC) were calculated using SPSS program. Paired T-test was used to compare the MIC experimental group differences.Results: Propolis was more effective against Lactobacillus, Enterococcus Faecalis and Pepto-streptococcus with 8.6984mm compared with 7.0833 mm mean diameter of inhibitory zone for Ca(OH)2. The difference was statistically significant (P<0.001) indicating that Ca(OH)2 was less effective against experimental microorganisms. The inhibitory zone of the two drugs demonstrated stronger effect of Propolis on contaminating microorganisms. On the other hand, the Minimal Inhibitory concentration of Propolis for all studied microorganisms was at least 4 times less than Calcium hydroxide.Conclusion: Propolis was more effective than calcium hydroxide against lactobacillus, Enterococcus faecalis and Pepto-streptococcus.

Background and Aim: Early diagnosis and treatment of TMD can significantly reduce future complications of this condition. General dental practitioners can play pivotal role in early detection of such patients by conducting careful initial evaluation. Therefore, this study was conducted in order to evaluate the TMD knowledge of general dentist practicing in Tehran, in 2005.Materials and Methods: Using cross-sectional study design, a total of 400 dentists practicing in the north, east, west and central parts of Tehran were randomly selected for participation in this investigation. A questionnaire was used to collect data on demographic information of dentist, including: age, sex, location of practice, type of services provided; as well as the name, location of dental school where one graduated from. The second part of the questionnaire asked about dentists' knowledge on TMD and related factors. The levels of reported dentists' knowledge were classified into four categories: excellent, good, moderate and low. The relationship between dentists' knowledge about TMD and relevant factors were analyzed using descriptive statistical methods as well as multiple regression analysis.Results: The study sample included 173 females and 227 males (n=400), with average age of 38.44 years. The level of TMD knowledge was excellent for 10 % of respondents, good for 38.75%, moderate for 38.75% and weak for 12.5%. The TMD related knowledge was excellent in 20.25%, good in 41%, moderate in 29%, and weak in 9.75%. In search of relationship between individual characteristics and knowledge of TMD and related factors, a significant relationship was detected between the educational institution (university) and the duration of study until graduation, (P<0.0001). Also, foreign graduates demonstrated the maximum TMD knowledge compared with provincial college graduates who had minimum knowledge.Conclusion: The TMD knowledge of dentist practicing in Tehran is adequate for early detection of abnormal conditions.

Background and Aim: Achieving apical seal in root canal therapy by Gutta-percha and sealer is an important factor in successful endodontic therapy. The purpose of this study was to investigate the effectiveness of post space preparation on apical seal of canals filled with two different obturation methods.Materials and Methods: A total of 56 maxillary molar teeth with normal roots were randomly selected in this experimental study. The palatal roots of all specimens were cut at CEJ in order to get the tooth length of 13 mm. The roots were then prepared by FlexMaster rotary system, using crown-down technique. All specimens were divided into four groups. Twenty four specimens in the first group were filled with tapered Gutta-percha 6% and 2SEAL sealer. Another 24 specimens in the second group were filled with lateral condensation technique and 2SEAL sealer. The third group (as positive control) was composed of four specimens; obturated without sealer and four specimens in the fourth group (as negative control) were covered with two layers of nail polish.All specimens were placed in Incubator with 100% humidity and the temperature of 37°C for 72 hours. The post space of 5 mm in length was then prepared by Gates Glidden number III in the first and second groups. Dye penetration technique was used to evaluate the apical seal quality. The groups were compared for differences in the amount of dye leakage using stereomicroscope. Student-T and Kolmogrov-Smirnovtests were used for statistical analysis. Results: The highest leakage was observed in the first group (single cone with Gutta-percha 6%), and the lowest leakage was seen in the second group (Lateral condensation technique with standard Gutta-percha) (P <0.05). Conclusion: Based on these findings, the lateral condensation technique has better apical seal after post space preparation than single cone technique. 

Background and Aim: The success rate of composite restorative materials depends very much on their color stability in the oral cavity. The purpose of this study was to investigate the color changes of four different brands of dental composite resin materials by using four staining solutions.Materials and Methods: A total of 128 disk-shaped specintens of 15. 2 mm were prepared out of 4 composite resin materials. Two nanocomposites: Filtek supreme, Tetric Evoceram and two micro hybrid composites: Filtek Z250 and Tetric ceram, were prepared. The specimens were then divided into 4 groups of 8 specimens each and they were immersed in 4 staining solutions (Coffee, Tea, Cola, and Artificial Saliva) for 3 hours daily over a 24 day testing period. The color of specimens was measured with a spectrophotometer using CIELab color space relative to illuminant D65 at baseline and after staining. The color differences (DE) were calculated. The DE =3.3 was used as an acceptable value in subjective visual evaluations. Data was analyzed using ANOVA and Post-hoc test at significance level of 0.05.Results: All tested materials showed unacceptable color change in coffee and tea groups (DE>3.3). The greatest color change was observed in Filtek supreme in coffee. The specimens in cola and artificial saliva didn't cause a notable color change clinically.Conclusion: Coffee and tea can significantly influence the discoloration of dental resin composite materials under investigation. The nanocomposite Filtek supreme color change was significantly more than other composites when exposed to coffee. Therefore, color stability of composite restorative materials depends very much on dietary habits.

Background and Aim: Conventional tomography is a cross sectional imaging modality that provides information about the width of the alveolar bone and the position of the critical anatomical structures such as mandibular canal in the lower jaw. In comparison with conventional CT, it is less expensive, more accessible and patients are exposed to much less radiation. The purpose of this study was to compare the accuracy and validity of spiral computed tomography and spiral conventional tomography. Materials and Methods: Ten fully or partially edentulous cadaver mandibles were selected. The specific points in anterior, canine, premolar, and molar regions were selected and imaging’s were performed with both radiographic systems. The distance between alveolar crest to superior border of mandibular canal, as well as mandibular height and width were measured by one oral and maxillofacial radiologist in two successive sessions. Results: The tomography and CT scan (as gold standard) measurements were compared. This evaluation revealed that the absolute mean differences in measuring the vertical dimension in the anterior, canine, premolar, and molar regions were 1.43, 0.74, 0.87, and 0.81 millimeters respectively. The horizontal dimension measurements were 1.21, 0.92, 0.76, and 0.82 millimeters respectively. The absolute mean differences in measuring the vertical and horizontal dimensions were 0.65 and 0.91 millimeters respectively. All these measurements were within limits of ±1mm error except in the anterior region. Both measurements of vertical and horizontal dimensions had the tendency to be underestimated in anterior region. In measuring the vertical and horizontal dimensions, the validity of spiral conventional tomography were 90.49% and 73.02% respectively, and both were statistically significant (P<0.001). Conclusion: From the results of present study it can be concluded that the spiral conventional tomography is an accurate and reliable technique for measuring the vertical and horizontal dimensions in mandible.