Journal of Dental Medicine
Year:2006 | Volume:18 | Issue:4 (45)|Papers Count:14

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.

Background and Aim: External apical root resorption is a common iatrogenic consequence of orthodontic treatment. Much controversy exists in the literature about changes in root lengths at post treatment periods. Although many practitioners believe that resorption becomes stable after active treatment, quantitative data are scarce. The purpose of this study was to determine quantitative changes in root lengths of maxillary incisors during fixed orthodontic post treatment period, and to assess if it is influenced by gender and factors related to active treatment. Materials and Methods: This was a case cross over study, performed on 80 patients (52 females and 28 males) aged between 13 and 22 years. At debonding stage and beginning of retention phase of fixed orthodontic treatment, Hawley type retainer was fabricated for maxillary arch. Periapical radiographs of maxillary incisors using standard parallel technique were obtained immediately after debonding, and 3 and 7 months later. Crown and root lengths of maxillary incisors were measured using computer program. Changes in root lengths were calculated considering correction factors. Also associations between some factors and the change in root lengths during post treatment periods were assessed. These included gender, type of treatment plan (non extraction/extraction), technique (standard edgewise/straight-wire edgewise) and duration of active treatment (less than 2 years/2 years and more). T-test and 4-way ANOVA were used for statistical analysis with P<0.05 as the limit of significance. Results: No significant relation was found between apical root resorption of maxillary central incisors and time elapsed after treatment. Significant relation was observed between apical root resorption of maxillary lateral incisors and the length of post treatment period. No significant relation was found between root length changes of maxillary incisors during post treatment period and gender, type of treatment plan, technique, and the length of active treatment period (P> 0.05). Conclusion: Considering the general process of root length reduction in maxillary lateral incisors during post treatment period, establishment of preventive measures is emphasized.

Background and Aim: Aggressive periodontitis is one of the periodontal diseases, which affects systemically healthy individuals usually under the age of 30 years old. The disease is characterized by rapid bone destruction which is not in accordance with the quantity of bacterial plaque. The purpose of the present study was to determine the prevalence of aggressive periodontitis among 15-18 years old female students in Tehran high schools. Materials and Methods: In this cross sectional study, , 2870 students were selected from all educational areas of Tehran during 1382-83 based on systematic clustered random sampling .Probing pocket depth on 6 areas of incisors and first molars were examined in each subject. Students with pocket depth equal to or more than 4 mm on more than one tooth were referred to Shahed Dental School for radiographic examination. For cases in which the distance between the crest of interdental septa and CEJs were equal to or more than 2 mm, full clinical and radiographic examination was performed. Results: Among the subjects of study, only 4 fulfilled the diagnostic criteria of localized aggressive periodontitis. Nobody was diagnosed with generalized aggressive periodontitis. The prevalence of aggressive periodontitis among 15-18 years old schoolgirls was 0.14%. Conclusion: The results of the present study were similar to previous studies with the same age groups and diagnostic criteria in other countries. For determination of total prevalence in Tehran, similar studies in schoolboys are recommended.

Background and Aim: The bonding mechanisms of self etching primers, based upon the simultaneous etching and priming of dentin, simplifies the bonding technique, but the efficiency of these systems is still controversial. This study compared the shear bond strength of three self etch adhesive systems in dry and wet conditions. Materials and Method: In this experimental study, 77 intact bovine lower incisors with flat 600 grit sanded enamel surface were fixed in acrylic molds and divided into 7 groups, of 11 teeth. The enamel surfaces were treated according to a special procedure as follows: Group 1: Prompt L-Pop (PLP) in dry condition, Group 2: Prompt L-Pop in wet condition, Group 3: Clearfield SE Bond (CSEB) in dry condition, Group 4: Clearfield SE Bond in wet condition, Group 5: iBond (iB) in dry condition, Group 6: iBond in wet condition, Group 7: Margin Bond (Control) in dry condition. Surfaces were air dried for ten seconds, or blot dried in wet condition. Composite resin was bonded on the enamel and built up by applying a cylindric teflon split mold (4 mm height 2mm diameter). After 24 hours storage in dionized water at room temperature, all specimens were thermocycled and shear bond test was employed by a universal testing machine (Instron) with a cross-head speed of 1mm/min. The shear bond strength was recorded in MPa and data were analyzed with ANOVA and Scheffe statistical tests. P<0.05 was considered as statistically significant. The mode of failure was examined under a stereomicroscope. Results: 1- Shear bond strength of CSEB in dry condition (21.5 ± 4.8 MPa) was significantly higher than PLP and iB groups (p<0.0001). 2- Shear bond strength of iB and PLP groups in dry condition (9.60 ± 2.2, 9.49 ± 3 MPa) were significantly lower than CSEB and control (2.99 ± 5.1 MPa) (P<0.0001). 3- There was no significant difference between PLP and iB groups in dry condition (P=1). 4- Shear bond strength of CSEB in wet condition (21.8 ± 3 MPa) was significantly higher than PLP and iB groups (P=0.0). 5- Shear bond strength of CSEB (10.8 ± 3 MPa) and PLP (10.6 ± 4 MPa) in wet condition were significantly lower than CSEB and Control groups (P=0.0). 6- There was no significant difference between PLP and iB groups in wet condition (P=0.99). 7- Shear bond strength of the three adhesives had no significant difference in dry and wet conditions (PLP: P= 0.53, CSEB: P= 0.84, iB: P= 0.53). The mode of failure in two groups of PLP and two groups of iB was predominantly in the adhesive bond and in the two groups of CSEB, mixed failure (adhesive with cohesive in composite) was predominantly observed. Conclusion: CSEB had higher while iB and PLP showed lower bond strength to ground enamel. The three self-etch adhesives in this study did not show technique sensitivity to wet and dry enamel.  

Background and Aim: Recycling of brackets can significantly reduce the price of fixed orthodontic appliances but if the bond is more prone to failure during treatment, this potential benefit will disappear. The aim of this study was to investigate the effect of chemical recycling on bond strength of metal orthodontic brackets and failure pattern of recycled brackets. Material and Methods: In this experimental study Instron machine was used to measure shear bond strength (SBS) of brackets in two stages on 60 human maxillary first premolars using No-Mix composite. Shear bond strength and pattern of failure were compared between recycled and new brackets in two stages. Data were analyzed by ANOVA and Duncan tests. Adhesive Remnant Index was evaluated in different groups by Pearson Chi-square test. P<0.05 was considered as the limit of significance. Results: Statistical analysis showed that the mean values of SBS for new bracket group was 12.00 MPa and for recycled group and double recycled group, 9.94Mpa and 10.00 MPa respectively. A significant reduction (about 18%) in bond strengths of brackets was observed at the first time of recycling. Recycling at the second time had no significant influence on the bond strength. Pattern of bond failure of these brackets showed that a great amount of residual adhesive material was remained on the teeth surfaces after debonding of recycled brackets which indicates that cleaning the teeth surfaces after debonding of recycled brackets is more time consuming. Conclusion: Based on the results of this study, before using recycled brackets, several advantages and disadvantages must be considered.

Background and Aim: Care must be taken during root canal therapy to prevent contamination of filling materials and avoid root canal contamination. Gutta-percha cones are now widely used to fill root canals. However they are not resistant to conventional sterilization processes in moist or dry heat. To keep the aseptic chain, gutta-percha cones require rapid chair side decontamination before use. Considering different methods for rapid decontamination of gutta-percha cones, use of chemical agents is the best. The purpose of this study was to compare the effectiveness of three different disinfectant solutions in rapid decontamination of gutta-percha cones in one minute Materials and Methods: In this experimental study, 360 gutta-percha cones were placed in bacterial suspensions of Staphylococcus aurous, Escherichia coli and Bacillus subtilis spore for 30 minutes, and then immersed in disinfectant solutions (Micro-10, Deconex 53 Plus, 5.25% sodium hypocholorite) for 1 minute. After that, the cones were aseptically transferred to the test tubes containing sterile saline. This solution was diluted 10-fold and then cultured on in brain-heart-infusion agar and the number of colonies was estimated after 24 h incubation at 37°C. A series of 5 previously sterilized cones was used as negative control to check the sterility of gutta-percha cones directly from the manufacturer's box. Another series of gutta-percha cones were considered as positive control group. Results: No bacterial growth was seen in different test groups and negative control group. Conclusion: Analysis of disinfectant effects of sodium hypochlorite, Micro10 and Deconex 53 plus showed that all of these solutions have bactericidal and sporocidal effect and are very efficient in surface disinfection of gutta–percha cones in one minute. Because of irritative effects and unpleasant odor of sodium hypochlorite, Deconex 53 plus and Micro10 can be used for rapid decontamination of gutta-percha cones.

Background and Aim: Maintaining the original canal path and safety of canal preparation during instrumentation in curved canals have been subjected to many challenges. The aim of this study was to compare several parameters of root canal preparation using flexmaster rotary and hand used Nickel-Titanium instruments. Materials and Methods: In this experimental study, sixty extracted human teeth with root canal curvatures between 10 and 42 degress were divided into two similar groups with equal mean curvatures. Root canals in one group were prepared using flexmaster rotary instruments and the other with NiTi hand files. After canal preparation, different parameters such as straightening of curved root canal, loss of working length, fracture rate, perforation and working time, were evaluated and compared between the two groups. Data were analyzed by t student test with p<0.05 as the limit of significance. Results: Results showed that both instruments maintained the original canals' curvature. No loss of working length, instruments fracture or perforation was recorded. Working time was significantly shorter for flexmaster than hand files. Conclusion: Both systems under investigation respected original root canal curvature and were safe to use. Therefore the rotary techniques could be successfully introduced to undergraduate endodontic programmes.

Background and Aim: Geographic tongue (GT) is a relatively common lesion which is usually asymptomatic and found during routine examinations. Lesions may be single or multiple and frequently are confined to the dorsal surface and lateral borders of the tongue. Although the cause is unknown, zinc deficiency has been suggested as a possible etiologic factor. The purpose of the present study was to determine the therapeutic effect of zinc sulfate in patients with geographic tongue. Materials and Methods: This study was a randomized double blind clinical trial performed on 40 cases. 20 patients in experimental group were given zinc sulfate and 20 patients in control group took placebo. Slides were taken at the first day and healing was recorded after 10 days. Data were analyzed using chi-square test with P<0.05 as the limit of significance. Results: In 16 cases of the experimental group and in 3 cases of the control group signs of healing were observed. Conclusion: Regarding the role of zinc in epithelial tissues health and development of filliform papillas and in spite of the positive effect of zinc sulfate in treatment of geographic tongue, further investigations concerning its effects on other mucosal conditions are recommended.

Background and Aim: Chlorhexidine is a mouthwash with known antibacterial effect but its antifungal effect is not clear. The aim of this study was to compare the antimicrobial effects of nystatin and chlorhexidine mouthwashes (one Iranian product and the other, commercial) on Candida albicans under in vitro condition. Materials and Methods: In this experimental study, the strains of Candida albicans used consisted of one standard strain (PTCC 5027) and ten local isolates. The latter were obtained from patients referred to different dental clinics in Kerman city. The specimens were taken from the gum and palate area by sterile swabs and dipped into Stewards transport medium, transferred to the laboratory within one hour, and cultured on Sabauraud dextrose Agar. Colonies showing the characteristic appearance of Candida were further cultured and routine differential tests including germ tube formation were performed to confirm the diagnosis of C.albicans. These were used to prepare a microbial cell suspension of 0.5 Mc Farland concentrations. Each cell suspension was inoculated over duplicate plates of SDA and 4 wells of 5 mm diameter were made using sterile cork borers. Each previously coded mouthwash was placed in corresponding well and incubated for 24-48 hours and the diameter of inhibition zone was measured with ruler. The minimum inhibitory concentration (MIC) of each mouthwash for each isolate of Candida albicans was determined using dilution tube technique. Data were analyzed by SPSS package using proper statistical tests with P<0.05 as the limit of significance. Results: There was a significant difference between the antimicrobial effects of the four tested mouthwashes. The results indicated that Iranian nystatin mouthwash had the greatest effect and the average inhibition zone from the highest to the lowest was associated with Iranian nystatin, foreign nystatin, Iranian chlorhexidine and foreign chlorhexidine respectively. The MIC determination revealed that generally nystatin was more effective than chlorhexidine. No statistical difference was seen between the Iranian and foreign samples. Conclusions: Despite the antifungal effects of chlorhexidine, more investigations on different strains of C.albicans is required before recommending its cilinical application.

Background and Aim: The majority of commercial curing units in dentistry are of halogen lamp type. The new polymerizing units such as blue LED are introduced in recent years. One of the important side effects of light curing is the temperature rise in composite resin polymerization which can affect the vitality of tooth pulp. The purpose of this study was to evaluate the temperature rise in two different composite resins during polymerization with halogen lamps and blue LED. Materials and Methods: This experimental study investigated the temperature rise in two different composites (Hybrid, Tetric Ceram/Nanofilled, Filteke Supreme) of A2 shade polymerized with two halogen lamps (Coltolux 50, 350 mW/cm2 and Optilux 501 in standard, 820 mW/cm2 and Ramp, 100-1030 mW/cm2 operating modes) and one blue LED with the intensity of 620 mW/cm2. Five samples for each group were prepared and temperature rise was monitored using a k-type thermocouple. Data were analyzed by one-way ANOVA, two-way ANOVA and Tukey HSD tests with P<0.05 as the limit of significance. Results: Light curing units and composite resins had statistically significant influence on the temperature rise (p<0.05). Significantly, lower temperature rise occurred in case of illumination with Coltolux 50.There was no significant difference between Optilux 501 in standard curing mode and LED. Tetric Ceram showed higher temperature rise. Conclusion: According to the results of this study the high power halogen lamp and LED could produce significant heat which may be harmful to the dental pulp.

Background and Aim: Infection control is an integral part of dentistry and dental impressions are considered an important issue in cross contamination. The aim of this study was to investigate the dimensional stability of two irreversible hydrocolloid materials, Alginoplast and Iralgin after disinfection with 5.2% sodium hypochlorite, used with immersion and spraying methods. Material and Methods: In this experimental study, impressions were made of a master mandibular arch (Typodont) containing three stainless steel inserts on the occlucal surface of both mandibular first molars and in the lingual surface of the mandibular central incisors, which served as reference marks for making measurements. Two types of irreversible hydrocolloid (Iralgin and Alginoplast) were tested. 5.2% sodium hypochlorite was used in two methods of spraying and immersion to disinfect the samples. The control group was not disinfected. Casts were made of type III gypsum. Stone casts were measured with a Nikon profile projector.Kruskall-Wallis and Mann-Witney test were used for statistical analysis using p<0.05 as the limit of significance. Results: Casts prepared from Alginoplast disinfected by spraying method, were 0.38 % larger in anteroposterior and 0.06% smaller in cross arch dimensions, whereas those prepared from Alginoplast immersed in hypochlorite were 0.47% larger in anteroposterior and 0.11% smaller in cross arch dimensions. Casts made from Iralgin were smaller after both methods of disinfecting, (0.01% smaller in anteroposterior and 0.001% smaller in cross-arch dimensions after spraying and 0.04% smaller in anteroposterior and 0.03% smaller in cross-arch dimensions after immersing in sodium hypochlorite). Conclusion: Alginoplast and Iralgin impressions can be immersed or sprayed for disinfection without compromising the accuracy needed for diagnostic and opposing casts, as well as removable partial denture construction.

Background and Aim: Compared to the information about educational responsibilities, there is not much information about the research skills and activities of the academics in dental schools. The aim of this study was to evaluate the research performance of the academic staff of the dental schools and their educational needs to promote their research skills. Materials and Methods: This cross-sectional study was done by mailing a questionnaire to all of the members of Iran dental faculties. The questionnaires contained personal information like age, sex, place of employment, educational records, and additional questions like the workshops previously attended, and interests to attend certain workshops. To evaluate the research performance of the academic staff, the number of accomplished researches, the articles published in known national and international journals, their skills in using internet, and the number of attended workshops about research methodology were included in the questionnaire. The completed questionnaires were gathered and evaluated by descriptive statistics. Results: From the questionnaires gathered, 436 were eligible to be included in the study, which formed 58% of the academic staff of dental schools. The results showed that 7.4% of the staff had more than 10 researches conducted, 15% had 5-10, 49.9% had less than 5, and 27.7 had no researches done. Considering the articles published in known national journals, 28.2% had no papers, 51.8% had 1-5 papers, and 20% had more than 5 papers. Regarding the number of articles published in known international journals, 77.5% had no papers, and 20.2% had 1-3, and 2.3% and more than 3 papers. The "preliminary research methods" workshop had the highest percent of participation (71.6%), and "Stata acquaintance" workshop had the least (0.7%). The participants were mainly interested to participate in three workshops, "English scientific writing" (26.3%), "principles of scientific writing" (17.5%), and preparing research proposals" (16.2%), respectively. Conclusion we concluded that the research skills and performance of the academic staff, though improved in the recent years, is still unsatisfying. In order to promote it, it is recommended to organize workshops about "research methodology", "scientific writing" and "preparing of proposals"