Journal of Dental Medicine

Background and Aims: The purpose of the present study was to investigate the relationship between study skills and academic performance of dental students in Tehran University of Medical Sciences.

Materials and Methods: 195 dental students at dental faculty of Tehran University of Medical Sciences in 2013 participated in this descriptive-analytical study. Data were collected using Congos´ Study Skills Inventory including six subscales. Grade Point Average (GPA) indicated their academic performance. Data were analyzed using ANOVA and Tukey test.

Results: The mean score of students’ study skills were 108 out of 200 with standard deviation of 22.06±0.7. Note taking had a significant correlation with GPA (P=0.015).

Conclusion: Since no significant correlation between study skills and academic performance of the students was observed, it seems that there are other dynamics involved in their academic performance which have to be examined.

Background and Aims: Choosing an appropriate style of teaching-learning by educators is a way to reach high quality education. The objective of this study conducted in Babol Dental School was to compare dental students^, satisfaction of teaching theoretical general pathology course by means of a combination of lecture and work in small groups with their satisfaction of teaching the course by means of only lecture.

Materials and Methods: This study was performed in the second semester of school year 2011-12 and 2012-13. In 2012 (intervention group, response rate=92%), the teaching of theoretical general pathology course was implemented by means of a combination of lecture and work in small groups, but in 2013 (control group, response rate=81%) by means of only lecture. An anonymous self-administered questionnaire was used to assess students^, satisfaction of the teaching methods. To compare the mean total score of satisfaction (ranging from 18 through 90) between the two groups, T-test was used.

Results: Comparing the mean total scores between the two groups revealed that students^, satisfaction of the combined teaching method was significantly higher (P<0.001). The difference of satisfaction between genders (separately for each group) was not significant in combination group and lecture group (P=0.63 and P=0.87,   respectively).

Conclusion: Regarding learning, combining lecture with other teaching methods such as work in small groups may increase health sciences students' satisfaction. In regard to teaching theoretical general pathology course, our findings could confirm this hypothesis.

Background and Aims: In response to esthetic demand and use of zirconia abutments; detection of implant-abutment connection misfit is so important. The purpose of this study was to evaluate the sensitivity and specificity of radiographic images in the detection of abutment-implant connection misfit in zirconia and titanium abutments of three different implant connections.

Materials and Methods: One regular implant fixture of Branemark, Noble active and Replace systems were mount in acrylic models. Two pieces titanium and zirconium abutments were attached to the implants, once with correct adaptation and once with 0.5 mm spacer. Digital radiographic images were taken of 12 created states with zero degree vertical and horizontal inclination and evaluated by 10 specialists in implant treatment in two different time penods. Data were analyzed using Kappa analysis.

Results: Interclass Correlation Coefficients (ICC) of the agreement of answers in the first and second times were 97.4 and 97.5, respectively (P<0/001). Sensitivity of detecting gap in all groups was acceptable (95-100%) except titanium abutment in Noble active which was the lowest value (35%). Specificity of all groups were acceptable (80-95%) except zirconia abutments in Noble active and Replace with 45% and 30% values, respectively, and titanium abutments in Branemark had the highest value (95%).

Conclusion: The sensitivity of radiographic images in detection of abutment-implant connection misfit only in Noble active with titanium abutment was not acceptable. Specificity of radiographic images in the absence of gap in titanium abutments was more favorable.

Background and Aims: Improving dental implantation conditions in order to reduce the failure is always desirable for researchers. The aim of this study was to compare two different materials of dental implants from the viewpoint of biomechanical effect after placement and loading in the mandible.

Materials and Methods: A 3D model of mandible was designed in the MIMICS 10.01 software. Then, by using the obtained model, the end part of the mandible was designed in CATIA V5 software and a drilling operation was performed on the cortical bone of mandible by finite element analysis simulation method in DEFORM-3D V6.1 software. Thereafter, the 3D model of created hole was extract from the drilled site and an ITI dental implant model designed in the CATIA V5 software, was placed in the hole. The space remained between the implant and cavity was considered as a newly-formed cortical bone in drilled site after 6 weeks of dental implant placement and the mechanical properties of newly-formed bone were entered to DEFORM-3D V6.1 software. Then, a load was applied on the top surfaces of two dental implant models with the materials titanium and zirconium-2.5% niobium.

Results: The emerged volume changes in newly formed cortical bone around Ti and Zr-2.5 Nb dental implants were measured 0.238 and 0.242 percent, respectively. Furthermore, micro-motion of Ti and Zr-2.5 Nb dental implants were measured 0.00514 and 0.00538 mm, respectively.

Conclusion: The results of this study showed that Ti dental implant created better conditions than Zr-2.5 Nb dental implant in the mandible.

Background and Aims: This study aimed to assess the severity of tooth decay and related factors in children 5-7 years old, in 2016, in Tehran.

Materials and Methods: A descriptive and cross-sectional study was performed on 572 children aged 5-7 years old (300 girls and 272 boys) in public schools in Tehran, Iran. Severity of dental caries (number of decayed, missing, filled surfaces) recorded for C, D and E teeth according to WHO criteria. Data analysis was performed by Backward Linear Regression Analyses using SPSS 20 (P≤0.05).

Results: Assessment of dental caries severity according to the number of decayed surfaces showed generally higher figures in upper jaw. The order of average severity of carious teeth was C, E and D from low to high in both jaws. According to the results of Linear Regression Analysis, severity of dental caries was more than other children in boys (OR=1.83, 95%CI: 0.81-2.8), those visited dentist due to dental problems associated with pain (OR=1.17, 95%CI: 0.73-1.6), and those without fluoride therapy (OR=1.64, 95%CI: 0.58-2.6) in C, D and E teeth.

Conclusion: Flow the results, it was concluded that gender, level of mother's education, type of snack consumption, start age of tooth brushing, reason for dental visit and fluoride therapy affected severity of tooth decay.

Background and Aims: Nowadays, oral cancer is considered one of the most important diseases related to oral health. The objective of the present study was to determine the dental students’ knowledge in Isfahan about oral cancer and the comparison of the level of students' knowledge in different years of education.

Materials and Methods: The present study was a cross-sectional-analytical one conducted in 2013. The population of study included the dental students of private and state University of Isfahan which 255 students were randomly selected. The data were collected using questionnaire and were then analyzed using SPSS software program and Kruskal-Wallis and Mann-Whitney.

Results: From private and public dental schools in Isfahan, 56% and 44% of dental students were involved. Regarding performing routine clinical oral examination, 81% of the participants answered positively, which showed no significant difference among the years of education of the participants (P=0.116). Regarding the examination of patients with oral lesions, 46% of them answered positively, which the difference between the years of education was highly significant (P≤0.001).

Conclusion: The findings of the research indicated that the level of knowledge of dental students of Isfahan city regarding the detection of oral lesions was not sufficient. Although, the students did not perform common examinations for exploring oral cancer, they did not have sufficient knowledge regarding some of the risk factors and oral lesions related to cancer. Therefore, it is necessary that a comprehensive curriculum be developed in this regard for their education.

Background and Aims: Dental caries is the most common infectious diseases. Among the oral bacteria, Streptococcus mutans and Streptococcus sobrinus are considered as the main causes of tooth decay. The aim of this study was to evaluate the production of hyperimmune bovine colostrum containing specific antibodies against cariogenic bacteria and its antimicrobial effects on the growth and adhesion of Streptococcus mutans and Streptococcus sobrinus in the laboratory.

Materials and Methods: In this experimental study, three pregnant bovine immunized with killed antigens of strains of Streptococcus mutans, Streptococcus mutans with Streptococcus Sobrinus and Streptococcus sobrinus through intramuscular injections. After delivery, The colostrum samples were collected, and the changes of anti-streptococci antibodies titers in colostrum and serum were determined by agglutination. Also,their antimicrobial effects against the growth and adhesion of oral streptococci were surveyed by the microtiter plate method. Data were analysed by One-Wey ANOVA in SPSS software.

Results: The results showed that in hyperimmunized bovine , the antibodies titers against injected bacteria were from 1.1000 to 1.3000 in sera samples and from 1.320 to 1.1280 in whey of colostrum samples. Colostrum of hyperimmune cows reduced the attachment of Streptococcus mutans and Streptococcus Sobrinus about 69 and 43 percents, respectively and also, the low dilutions of it reduced bacterial growth.

Conclusion:  According to the antibacterial effect immune colostrum on two strains of cariogenic bacteria in vitro, It appears that this material could be useful in the prevention and control of dental caries.

Background and Aims: Taking impression from angulated implants has always been a great challenge in clinic. In this regard, studies on sectional trays are very few. The aim of this study was to evaluate and compare the dimensional and angular accuracy of impressions using full arch and sectional trays.

Materials and Methods: Four implants (4.3 × 12 mm) (Implantium, Dentium) were placed in the first premolar and molar regions of a Kennedy class I mandibular acrylic model with 30° lingual angulation. Twenty open special trays (Full arch & Sectional) were made on the primary cast. The impressions were taken using vinyl polysiloxane (VPS) and were poured with type IV dental stone. The coordinate measuring machine (CMM) was used to measure the dimensional (Z, Y, X) and angular (θ) coordinates of implants. The data were analyzed using and t-test and SPSS 22. Software.

Results: The type of tray had no significant effect on the dimensional accuracy in X, Y and Z axes (P>0.05) and total linear displacement (r); However, it significantly affected the angular accuracy (∆q) (P<0.05).

Conclusion: Sectional tray yields less rotational displacement in impressions made of angulated implants.

Background and Aims: Tooth decay has high prevalence in the world. The use of plant material for the prevention and treatment of this disease for various reasons is considered, due to the increasing resistance of bacteria to antibiotics, the high cost and adverse effects of some chemicals used in dentistry. This study was aimed to determine the antimicrobial effect of alcoholic extract of Pepper (Capsicum annuum) and eggplant skin and cap on the cariogenic streptococci.

Materials and Methods: In this study, the antimicrobial activity of ethanol extract of Capsicum annuum and eggplant skin and cap on the cariogenic streptococci, including Streptococcus mutans, Streptococcus sobrinus, and Streptococcus sanguis by microtitre plate method for MIC (Minimum Inhibitor Concentration) was performed. Data were analyzed by one-way analysis of variance using Prism 5 Graph Pad software.

Results: MIC for the Capsicum annuum and eggplant skin for Streptococcus mutans was 250 mg/ml (SD=0.052), and for the Streptococcus sobrinus and Streptococcus sanguis was 125 mg/ml (SD=0.027). The MIC for the cap eggplant for Streptococcus mutans and Streptococcus sobrinus was 500 mg/ml (SD=0) and for S. sanguis was getting 125 mg/ml (SD=0.159).

Conclusion: This study showed that the herbal extracts of Capsicum annuum and eggplant skin and cap had beneficially antimicrobial effects on all three strains of cariogenic streptococci.

Background and Aims: The exact placement of impression copings in making accurate prosthesis is very important. In some cases, the implants need to be placed deeply subgingival, which could reduce the direct vision and ultimately reduce the precision of impression copings and subsequently, delivered prosthesis. This would be the cause of multiple complications such as delivery of ill-fitting prosthesis. The aim of this study was to evaluate the effect of the dental implant placement depth on the accuracy of impression coping connection by students.

Materials and Methods: This in-vitro and experimental study was conducted by 50 senior dental students. Four implants at different depths (0, 2, 4 and 6 mm) were placed in a model. After learning how to mount impression coping on implants, the students were asked to mount impression copings on all four implants. The samples were examined by an experienced prosthodontist using a magnifier with 4x magnification. Data were analyzed by statistical Cochran test (P<0.05(.

Results: The proper adapting rate of transfer copings, in subgingival implants with the depth of 0, 2, 4 and 6 mm were 100%, 62%, 58% and 20%, respectively. Statistically significant differences were observed between all groups (P<0.001).

Conclusion: The results showed that there was an inverse relationship between the increasing depth of the implants in the gingiva and the dentist’s ability to connect the impression copings properly.

Background and Aims: Opinion of students regarding the content, structure and quality of their training is a fundamental part of holistic evaluation of curriculum, and serves as an important information resource in policy making. In the present study, we aimed to contribute to the development, assessment and evaluation of the new national dental curriculum through evaluation of last-year dental students’ opinions regarding undergraduate dental curriculum.

Materials and Methods: This cross sectional questionnaire survey was done in 2010-2011 academic year. The target population was last-year dental students in 15 Iranian state dental schools. In these schools, all last-year dental students were invited to participate in the study. The chi-square test served for statistical analyses.

Results: In total, 432 students (68.4% female) participated in the study. Of the respondents, 72.4% (60.7% of male and 77.6% of female, P=0.001) believed that their undergraduate dental training had been completely inadequate or inadequate. Only about one third of students believed that educational methods during their undergraduate dental training had been appropriate or completely appropriate.

Conclusion: In general, it seems that undergraduate dental training from students’ view point has not been appropriate in terms of both content and method. The results show the necessity of revision of national undergraduate dental curriculum.

Background and Aims: Trauma to the permanent and deciduous incisors is an undesirable common event in childhood. Proper immediate management of injured teeth is depended on the knowledge of unprofessional people, including teachers, who are usually present at the scene prior to dental treatment. The aim of this study was to assess the knowledge and self-reported practice of primary school teachers on the emergency management of traumatic dental injuries (TDIs) in Arak.

Materials and Methods: In this cross-sectional study, 624 primary school teachers were enrolled in census in Arak. An anonymous questionnaire containing demographic data, the history of previous exposure to traumatic dental injuries, teachers’ knowledge regarding emergency management of TDIs and their practice towards TDIs was used. Questionnaires were distributed among all participants and then were collected on the same day. Descriptive statistics and linear regression were performed to analyze the data.

Results: A total of 292 completed questionnaires (response rate 46.8%) were collected. The mean score of knowledge was 2.65±1.69 out of 10. The mean score of self-reported practice was 3.46±2.04 out of 8. Regarding the demographic variables, knowledge had a significant relationship with the education (P<0.001). No significant relationships were observed between the self-reported practice and demographic variables. The correlation coefficients between the knowledge scores and the practice scores of teachers was 0.2.

Conclusion: This study revealed that insufficient knowledge exists among primary school teachers on emergency management of TDIs. Furthermore, a high percentage of respondents enjoy a significant deficiency regarding favorable practice encountering TDIs.

Background and Aims: Dental caries is an infectious disease transmitted by multiple factors in the mouth and one of the most common chronic diseases in the world that requires a lot of treatment expenses. The aim of this study was to evaluate the effect of fluoride 0.2% and Fuchs mouthwash (a combination of xylitol and fluoride 920 ppm) against two bacterial growths (Streptococcus mutans and Lactobacillus acidophilus).

Materials and Methods: In this in vitro study, first the well diffusion method and then MIC method (minimum inhibitory concentration) were used. Data were analyzed with Excell (2016).

Results: The results of the MIC method showed inhibitory effect of both mouthwashes in pure concentration (128 μg/ml). However, fluoride was effective in concentration higher than 32 μg/ml for Streptococcus mutans and higher than 2 μg/ml for lactobacillus acidophilus. Fuchs was effective for both bacteria at concentration higher than 64 μg/ml and in lower concentration it was ineffective. The results of the well diffusion test showed the inhibition of fluoride mouthwash in pure concentration on the Streptococcus mutans was (17 mm) and on the lactobacillus acidophilus 24 mm was obtained. In Fuchs mouthwash was zero and it represented effectiveness of fluoride on bacteria and ineffectiveness of Fuchs.

Conclusion: The fluoride mouthrinse in different concentrations, because of having a good inhibitory effect in both methods on Streptococcus mutans and Lactobacillus acidophilus was more effective compared with that of Fuchs mouthrinse.

Background and Aims: Increase of esthetic demands among dental patients has led to development and wide spread use of tooth colored ceramic systems for fabricating fixed restorations. However, they do not have same capability of matching the target color. The aim of this study was to compare the color coordinates of three widely used systems with A2 tab from a Vita Lumin Classic shade guide.
Materials and Methods: In this study, three ceramic systems were tested. The metal-ceramic(MCR) with 0.5 mm core and 1 mm Ceramco lll veneering layer; the all ceramic (CE) with 0.5 mm Cercon core and 1 mm Cercon Ceram veneering layer, and the all porcelain (VM7) with 1.5 mm Vita VM7. For each system, 15 disks (1.5mm×10mm) were made in Vita A2 shade. L*a*b* coordinates of the samples were measured by spectrophotometer and the color difference with Vita A2 shade was calculated. The data were analyzed using one way ANOVA and multiple Tukey tests.
Results: The color coordinates of the target shade was L*=72.45, a=1.59 and b*=14.11. The mean L*a*b* values for MCR were 72.61±0.38, 2.88±0.24, 15.51±0.64, for CE were 76.42±0.46, 2.77±0.14, 17.51±0.61, and for VM7 were 75.13±0.6, 2.15±0.19, 17.9±0.61, respectively. The difference between coordinates of each system with target shade was significant. Only for MCR group, ΔE was in acceptable range (1.98). For CE (Δ=5.38) and VM7 (Δ=4.72) groups, the difference was unacceptable.
Conclusion: Under the condition of this study, the metal-ceramic system had the best and acceptable match to the target shade.
 

Background and Aims: In recent years, dental implants have received special attention in dentistry. Due to the remarkable success of predictable dental implants, there is growing interests in the scientific community from descriptions of implant success toward identify factors associated with implant failure. The purpose of this study was to identify the risk factors associated with implant failure in an objective and statistically valid manner.
Materials and Methods: To address the research purposes, we used a cohort study in which a total of 2368 implants were placed on 1011 patient in the Clinic of Tehran University of Medical Sciences. The predictor variables included demographic variables, the health status and variables are related to implants. The outcome variable of interest was implant failure. The overall implant survival was estimated using the Kaplan-Meier analysis. First, risk factors were identified using Chi-square test and Fisher's exact test and then the Cox proportional hazard regression models were used for more analysis.
Results: The overall 39 month implant survival using the Kaplan-Meier function was 0.99±0.002. The implant location (jaws) (P=0.049) and type of teeth (P=0.011) were found to have significant relation with failure times in Cox proportional hazard model.
Conclusion: According to result of this study, both implant location and type of teeth had effection the failure times so that, the survival in mandible was higher than maxilla. The failure rate was higher in anterior teeth than that of others (molar, premolar, canine and primary).
 

Background and Aims: First molar has an important role at individual’s dental health. Among the known risk factors, the experience of previous caries is of the best predictors for future caries. The aim of this study was to examine the association of primary teeth caries and other risk factors with the incidence of permanent teeth caries by considering the caries extent and severity.
Materials and Methods: This case-control study was done on 150 students from second and third grade with 9 years old. Cases included children with at least one carious permanent molar. Caries-free students who were matched based on the gender and mother education was considered as control group. Examination was done on dental unit under the unit light with blunt explorer and mirror for visual assessment. DMFT, dmft and caries severity (D1-D3) were recorded based on WHO standards. Data were calculated using SPSS18, Correlation, Chi Square Analysis, Odds ratio and Logistic regression.
Results: Linear correlation between dmft in primary teeth and DMFT in permanent molars was obtained with r:0.34 (P<0.001). Decay in permanent molars in students with active caries in primary molars was 3.3 times more probable than others. In regression model, the other risk factors such as cariogenic diet, mother`s education, brushing with toothpaste, flossing, using flouride, and regular dental visiting were not significant (P>0.05).
Conclusion: Caries-free primary teeth predicts permanent teeth without decay with a high possibility. It could be helpful in caries risk assessments.
 

Background and Aims: Poor adhesion between porcelain and some of the dental alloys is one of the most challenges to select the desirable alloy in dental restorations. Therefore, the aim of this study was to evaluate the bond strength of porcelain to some of the commercial alloys. This can help in selection of desirable alloy.
Materials and Methods: The shear bond strength of porcelain to the three of the most widely used nickel-base dental alloys commercially named as: Verabond, Damcast and Noritake were evaluated according to standard ASTM E4. The results were analyzed based on the statistical method of independent t with the meaningful level of P<0.05. Then, the bonding interface of the fired samples was evaluated using SEM equipped with EDX analyzer and X-ray diffractometry.
Results: The average bonding strength of porcelain to each of the above mentioned alloys were determined as: 27.54±5.48, 22.46±4.99 and 26.18±4.27 MPa, respectively. Due to the existence of Be and Al in the chemical composition of Verabond and Damcast and their higher appetencies to form the different surface oxides in preference to Cr₂O_3, not only the bond strength of porcelain to two these alloys was increased about 20 percent (compared with the Noritake), but also the color of their porcelain was not changed.
Conclusion: To replace the replacing of deleterious elements from the chemical composition of dental alloys. The added new elements should control through the oxide layer and the formation of Cr₂O₃ in porcelain-alloy interfaces for adequate bond strength.

Background and Aims: For the clinical success of implant-retained prostheses, fitness of matching components and stability of the applied torque to the implant-abutment assembly under dynamic occlusal loading is essential. The aim of this study was to evaluate the torque loss in Co-Cr castable abutments after cyclic loading.
Materials and Methods: 10 castable abutments were cast in Co-Cr alloy with similar size and height. Each specimen was mounted vertically on a separated implant using a 30 Ncm tightening torque. The detorque values of the abutments were evaluated after 10 min. The same tightening torque was applied to the abutments on their corresponding implants and cyclic loading was applied for 500,000 cycles to the implant-abutment assembly. The torque values after cyclic loading were recorded for each specimen. T-test analysis was conducted on scores from the groups.
Resultes: The results of this study showed that the percentage of torque loss in castable abutments was significantly increased after cyclic loading (P<0.001).
Conclusion: Misfit between the castable implant components can cause torque loss before and after cyclic loading. However, it is more appropriate to relate the results of this study to the screw loosening of the above mentioned abutments than judging their clinical performance.