Journal of Dental Medicine

Background and Aims: A suitable restorative material must have acceptable mechanical properties. The aim of this study was to evaluate the effect of conventional acidic drinks on the micro-hardness of two dental resins.
Materials and Methods: 48 samples of each of P60 and G-aenial composites were prepared and randomly divided into six groups: Coca-Cola, Fanta, yoghurt drinks, soft beer, Sprites and control groups. The study was in 3 steps: after one day in distilled water and after one day and one week of immersion in beverages per day
(6 hours). The Vickers micro-hardness was then evaluated. Finally, data were analyzed by, t-tests, ANOVA and Tukey tests.
Resultes: Comparing the results between the two groups, a significant difference between the two composite was found. After one day in the water, the average micro-hardness for P60 was of 27.12 (kgf/mm²) and 16.51 (kgf/mm²) for G-aenial amount and these differences were found statistically significant (P=0.0001). For the
6-hour maintenance interval, the average micro-hardness between P60 and G-aenial was statistically significant (P=0.0001). For 42 hours, the average micro-hardness ranged between P60 and G-aenial that were statistically significant (P=0.0004). The stiffness of the P60 composite after 42 hours’ storage in soft beer significantly decreased compared with the control group (P=0.03). G-aenial composite hardness after 42 hours of soaking in the Coca-Cola was reduced significantly compared to yogurt drinks (P=0.02).
Conclusion: As a result, the hardness of P60 composite was higher than that of G-aenial. The hardness of both composites reduced in acidic drinks after one week.

Background and Aims: Loss of retention is one of the main reasons of failure in teeth restored with post and core. Several factors, including the type of cement can influence the retention of the posts. As zinc phosphate cement is considered as the standard for comparison this study performed to review articles evaluating the retention of cast posts cemented with zinc phosphate.
Materials and Methods: This systematic review was performed based on the PRISMA (Transparent Reporting of Systematic Reviews and Meta-analyses) guide. The question of this study was that how much is the amount of retention of cast posts cemented with zinc phosphate. Hence, a literature search was done in PubMed and Medline databases as well as Google scholar search engine using relevant keywords until 2016 limited to the English language. Articles were selected based on the inclusion and exclusion criteria, and were evaluated qualitatively.
Resultes: Internet search resulted in 1141 articles. Following the application of inclusion and exclusion criteria, 6 studies were included in this systematic review. The most common post material was nickel-chromium alloy. Retention of casting posts cemented by zinc phosphate was from 8.76 to 34.2 Kg and from 91 to 192.2 N.
Conclusion: Our review showed that the retention of cast posts cemented with zinc phosphate in controlled condition is moderate and factors including post material and length could influence the retention of the post.

Background and Aims: Making dental prostheses is sensitive and accurate work and requires powerful and skilled hands. Because of this, the dental prosthesis technicians may suffer harmful effects such as stress and fatigue during the course. The aim of this study was to investigate fatigue, stress and job performance and their relationship with some demographic variables in this community.
Materials and Methods: The present study was cross-sectional and done in 2016. The study population was a group of dental prosthesis technicians that had participated in a national congress in Tehran. Sampling was done by census Two standardized questionnaires on the subjects of fatigue and stress which were distributed among 100 female and male participants and sampling was done by census. Then, the obtained data was analyzed using SPSS16 software and applying descriptive statistics, Pearson correlation test, and ANOVA, T-test.
Results: From the 100 samples, there were 16 females and 84 males with mean age 34.71±7.90 and average work experience of 10.82± 9.01 years. 82 percent of the subjects were married and 42 percent of them were smokers. The results showed that 100 percent of dental prostheses technicians were facing with moderate to severe stresses. The stress and fatigue scores in married ones were higher than the single ones. The results showed a significant relationship between smoking, stress, and fatigue scores (P<0.05).
Conclusion: According to the high level of job stress in the dental prostheses technicians, this problem must be considered, minimized, and more attention should be paid to their psychological and emotional problems.

Background and Aims: Children’s Fear Survey Schedule- Dental Subscale (CFSS-DS) is considered as the most popular instrument available to assess dental fear in children. The aim of this study was to develop a Persian version of the CFSS-DS among 8-12 year-old female children resident in Tehran.
Materials and Methods: At first, the questionnaire was translated in Farsi and  back translated in English afterwards. While, the back translated version was confirmed, we considered the Persian version as the final instrument. Content validity and reliability of the questionnaire was assessed. We used test-retest method to evaluate the reliability, 287 female students aged 8 to 12 from 7 schools in 6^th district of education ministry of Tehran were interviewed two times with interval of seven days. In addition, the infraclass correlation coefficient (ICC) and percentage of agreement were calculated. The score of dental fear was measured with range of 13 to 65 and changed to a number between 0 and 100. The relationship between dental fear score and the independent variables including age, history of hospitalization, last medical visit, and history of dental treatment were evaluated using the linear regression models.
Results: The mean score of dental fear was calculated 20.52. The score of dental fear was significantly associated with the last medical visit (P=0.04) and past dental history (P<0.001). The percentage of agreement was more than 80% for all the questions. In each question, Kappa was evaluated as moderate to good and ICC was good to very good (more than 0.4).
Conclusion: The findings of this study demonstrated that the Persian version of CFSS-DS was valid and reliable among 8-12 year-old children.

Background and Aims: In endodontically treated teeth, the fiber posts are used to retain a core restoration. The purpose of this study was to evaluate the effect of different resin cements on the bond strength of fiber reinforced composite posts to root canal dentin, and comparing the bond strength in different sections of root.
Materials and Methods: In this in-vitro experimental study, 48 extracted single-canal central incisors were endodontically treated. For the push out test, the posts were divided into 3 groups according to one of the following three different cement materials (n=16) (Bifix SE, Bifix QM, Rebilda). Three slices with a thickness of 2-mm were prepared of each root. The push-out tests were performed at a cross-head speed of 1 mm/minute using a universal testing machine. Data were analyzed by two-way and one-way ANOVA test followed by Tukey post hoc test (α=0.05).
Results: There was no significant differences between the mean push out bond strength of three experimental groups (P=0.650), but there were significant differences between the mean push out bond strength of root dentin regions (P<0.001).
Conclusion: Under the conditions of this study, there was no significant difference between the mean push out bond strength of 3 different resin cement systems. The coronal region of root dentin showed significantly higher mean bond strength values than that of the middle and apical thirds.

Background and Aims: The systemic and topical preventive effect of fluoride on tooth decay has been reported. The aim of the present study was to determine the fluoride level in imported and national fluoridated dentifrices in the Iranian market.
Materials and Methods: Sampling was randomly performed from the main market centers and pharmacies in Tehran. The total fluoride (TF) and total soluble fluoride (TSF) concentrations were determined by ion specific electrode potentiometer method. The samples were coded and one trained researcher performed the analysis. Descriptive statistics as percentage and analytical statistics reported as independent t-test were reported.
Results: In adults’ toothpastes, the total fluoride ranged from 191 to 1601.9 ppm with the mean of 911.2 (SD=331.4) ppm. The total soluble fluoride ranged from 322.8 to 1518.8 ppm with the mean of 1021 (SD=279.8) ppm. In children’s toothpaste total fluoride ranged from 236.3 to 1163.7 ppm and the total fluoride of 594 (SD=375). Total soluble fluoride in children’s toothpaste ranged 655.6-1102.6 with the mean of 879.1 (SD=316.07). Analysis of the total fluoride (TF) and total soluble fluoride (TSF) showed that there was no significant difference between the local and imported toothpastes (P>0.05).
Conclusion: The fluoride level of Iranian toothpaste was similar to that of the imported toothpastes, however there was variation in the level of fluoride in products.

Background and Aims: Color is the most important and complicated part of aesthetic dentistry. The tooth color matching of restorations is considered as one of the most difficult tasks in the restorative dentistry. The aim of this study to evaluate the effect of two training methods on the dental students’ ability in determining tooth color matching.
Materials and Methods: In this study, 40 dentistry students participated which randomly allocated into two groups. The first group consisted of students who learned teeth color matching methods practically. In the second group, training booklet was used for learning. Using Vita Classic shade guide series, 4 color samples were chosen and the students of each group were asked to determine samples’ color, before, after and one month after the training.
Results: Booklet learning group was more successful in determining fourth color sample. However, in no studied group and no used samples, the results of one month after learning were not better than that of before learning. Also generally, no significant relationship was found between the color matching accuracy, using glasses, and sex of participants.
Conclusion: The use of booklet learning was more effective than practical learning in color matching accuracy for dental students. Also, using glasses and sex were not effective on their color matching accuracy.

Background and Aims: Lichen planus is a chronic inflammatory mucocutaneous disease with unknown etiology. One of the most common manifestations of patients with oral lichen planus is gingival involvement in the form of generalized erythematous areas. The aim of this study was to review the articles evaluating the role of plaque control on the gingival manifestations of oral lichen planus.
Materials and Methods: Motor searches of Ovid Medline and EM base databases, PubMed, Google Scholar, and Science Direct were searched for article published between January 1990 and December 2017 using of relevant key words. After reviewing the abstracts of articles, 20 full articles were selected and among them, 7 relevant articles were reviewed in this study.
Conclusion: From the literature, it was concluded that effective plaque control is the main part of lesions treatment and improvement of symptoms and gingival manifestations of oral Lichen planus.

Background and Aims: Today, resin composites are one of the most commonly used materials in restorative dentistry. However, failure in resin treatments is also common due to its chemical nature and its high talent for decay recurrence. According to conservative approaches, "conservative" treatments are more likely to be considered than "Replacement" of damaged remedies. The purpose of this study was to compare different surface preparation methods on composite surfaces to achieve the highest bond strength between the old and new composites after accelerated aging.
Materials and Methods: First, composite cylinders with a diameter of 6 and a height of 5 mm were prepared using an incremental technique and a microhybrid resin composite. The specimens were stored in distilled water for 6 months at 37°C and then the surfaces of all aged compsites were roughened using diamond milling followed by phosphoric acid etching. The specimens were randomly subjected into five groups. Group 1: GC Composite Primer. Group 2: Universal bonding containing silane (Kuraray). Group 3: Self etching adhesive (SE bond; Kuraray) Group 4: silane (Ivoclar Vivadent) + Second bottle of SE bond bonding system (Kuraray). Group 5: control group with no treatment. Then, 5 mm incremental of new composite (similar to the aged composite with different color) were placed on the surfaces of specimens, sectioned, and thermocycled for 3000 cycles for the microtensile bond strength evaluation. The specimens were evaluated using a stereomicroscope after failure. Data were analyzed by one-way ANOVA and Post Hoc Tukey test.
Results: The specimens in which silane and SE bond were used showed the highest mean microtensile bond strength and those treated by universal bond showed the least bond strength which were significantly different (P=0.02). All samples had cohesive failure patterns in all groups and the percentage of failures in old and new composites did not differ significantly (P=0.69).
Conclusion: : Based on the results, all surface preparations used in this study could provide an appropriate bond strength for repair of old composite restorations. Also, the microtensile bond strength between the old and new composites was higher than the cohesive strength of resin composite itself. However, the mean microtensile bond strength value for the group treated by universal bond was significantly lower than those treated by silane and hydrophobic containing bonding system.

Background and Aims: Removable partial denture (RPDs) is a common therapy for rehabilitation of partialy edentulous patients while RPD causes a lot of periodontal problems. The purpose of this study was to investigate the effect of RPDs made in Babol dental school on the periodontal health of abutment and non-abutment teeth.
Materials and Methods: In this cross sectional study, 70 patients who were candidates for RPDs divided into four groups according to Kennedy classification. The following periodontal parameters were evaluated for abutment and non-abutment teeth, plaque index (PI), calculus index (CI), width of keratinized gingiva, bleeding on probing (BOP), periodontal pocket depth (PPD), tooth mobility (TM) and gingival recession. This clinical measurement was taken immediately before insertion of the RPD, then one, three, and six months later. These parameters were then analyzed using Mann-Whitney, Independent sample t-test, Covariance, Chi-square statistical tests.
Results: In Class I; the mean score for the width of keratnized gingiva (P<0.001), PPD (P=0.002), and BOP (P<0.001) of the abutment and non-abutment teeth were significantly different after 1 month. After 3 months there were significant differences with regard to the PI (P=0.01), width of keratnized gingiva (P<0.001), BOP (P<0.001) and PPD (P<0.001). After 6 months, only the PI, CI, and TM parameters were not statistically significant. In Class II; the mean score for width of keratnized gingiva (P<0.001) and PI (P=0.002) after 1 month, width of keratnized gingiva (P<0.001), BOP (P=0.02), PPD (P=0.05) and TM (P=0.03) after 3 months and width of keratnized gingiva (P<0.001), PI (P=0.04), BOP (P<0.001) and TM (P=0.03) after six months were statistically significant. In Class III; only gingival recession did not show any significant difference at 1 and 3 months later. The width of keratnized gingiva (P<0.001), PI (P=0.001), BOP (P<0.001) and TM (P=0.03) after 6 months were statistically significant.
Conclusion: This study showed that RPDs affect the periodontal condition of both abutment and non-abutment teeth, which can be reduced by more precise design of the prosthesis, periodontal follow ups and good oral hygiene.

Background and Aims: Use of computer and internet in our modern and digitalized society is an efficient tool to be up to date and fulfil the information gaps. The aim of this study was to evaluate the extent of computer and internet usage among dental students of Islamic Azad University, Tehran, in 2016.
Materials and Methods: This descriptive study for evaluating access and usage of computer and internet by dental students was done using a researcher-made questionnaire on 401 dental students. Validity and reliability (Kappa: 0.82) of the questionnaire was confirmed. Statistical analysis was done by SPSS22 using descriptive and Logistic regression analyses.
Results: More than 95% of the students had access to the computer and Internet. 45.6% of students reported their skills were in the basic level. The major use of computer among the students was internet but only 13.2% of students used Microsoft Office program. The students used the internet for dental subjects even monthly (34.9%) or weekly (29.4%). Only 9.7% of the students had participated in educational workshop for learning methods of research. The most limitation was internet velocity. Positive correlation was found among prospering ownership status (P<0.001), economic status (P=0.05), level of education semester (P=0.038) and the computer & internet usage (what’s more in terms of access and also in terms of improve information and knowledge).
Conclusion: Based on the results, a higher economic level, higher level of education, and property ownership made better access to the computer and Internet. However, computer skills should be more concerned in educational program.

Background and Aims: Due to high mortality rate and cost of smoking, WHO has emphasized on the role of dentists in smoking cessation among patients. The aim of the present study was to investigate the dental students, knowledge toward health consequences of smoking, their attitude towards smoking cessation activities, and their education programs in this field.
Materials and Methods: In this cross-sectional study, the target group was senior dental students at Tehran and Shahid Beheshti Universities of Medical Sciences, and Azad and Shahed Universities. A questionnaire was used to collect data in addition to background information, on the knowledge, attitudes, and education towards tobacco cessation counseling in dental practice was administered to the students. The sampling method was census. Data were analyzed using oneway Anova followed by Turkey HSD post-hoc test for pairwise comparison.
Results: Overall 138 students participated in this program (The response rate was 100%). Of the maximum achievable knowledge score (28), the average knowledge score in Tehran University was 22.8, in Shahid Beheshti University 20.31, in Azad University 22.31, and in Shahed University 22.16 (P=0.027) with significant statistical differences. However, But the average of attitude and education score of the students did not vary significantly (P>0.05).
Conclusion: Most of the students had sufficient knowledge about the risks of tobacco use and positive attitude toward tobacco cessation counseling. It was concluded that the students would only pay attention to the principals of smoking cessation counselling when they actually believe in them. Therefore, in order to improve the performance of students, training should be given on tobacco cessation techniques at the dental schools, thus, that students could play an effective role in tobacco cessation counseling for patients.

Background and Aims: One of the most important determinants of health is Oral Health Literacy (OHL). The aim of this study was to investigate the OHL among nomadic population in Kouhrang city as pristine society.
Materials and Methods: This was a  cross -sectional descriptive study among 200 nomadic population aged 18-60 years of Kouhrang city in 2018. Data were collected using a questionnaire and face-to-face interview, sampling method was performed by randomized cluster. The questionnaire consisted of 17 questions in 4 sections of reading comprehension, listening, perception of number, and decision making. According to the number of questions, the questionnaire score was formed 0 to 17 and the nomadic populations were categorized into three groups with inadequate OHL (0-9), borderline OHL (10-11), and adequate OHL (912-17).
Results: The mean and standard deviation of the participants in this study was 35.49±12.00. The results showed that 7.00% of participants had sufficient OHL (12-17), 21.51% borderline (10-11), and 71.50% had inadequate OHL
(0-9). The mean and standard deviation of OHL score in general was 7.65±2.80, and the mean DMFT index was 8.03±5.64 (P<0.001).
Conclusion: The results of this study showed that the OHL score in the nomadic population was low, and also the mean DMFT index was very high. It is necessary to pay attention to the timely prevention and treatment of the teeth, as well as serious attention to the health education in this population.

Background and Aims: One of the most important challenges for dentists is providing a crown with appropriate marginal fit and gap. The 135-degree tooth preparation found to have some advantages such as technical ease and appropriate finish line record. Despite the advantages of 135-degree tooth preparation, scant research has been done in this area. Therefore, the aim of this study was to compare 135-degree and deep chamfer tooth preparation on the marginal fit and marginal gap of posterior metal-ceramic crowns.
Materials and Methods: Deep chamfer and 135-degree tooth preparation were performed on the two first mandibular molars with healthy coronal tissue and similar size. Impression was taken from each tooth and 30 crowns were made on each die. The sample plastered with fit checkers were pressed under the force of 40 N for 3 min in a universal testing machine. They were measured and recorded under a loop with 40x power in three points on each aspect. Data were analyzed by Wilcoxon and Kolmogorov-Smirnov tests using SPSS version 24.
Results: The mean marginal fit values in deep chamfer and 135-degree were 48.5417µm and 55.3333 µm, respectively with no statistically significant difference (P>0.05). While the mean marginal gap in deep chamfer (2.4833 µm) was significantly higher (P<0.05) than 135-degree (1.0083).
Conclusion: It can be concluded that the marginal gap by 135-degree’s tooth preparation was lower than that of deep chamfer in metal-ceramic crowns. However, no significant difference in the marginal fit between the deep chamfer and 135-degree tooth preparation was found.

Background and Aims: Dental caries is a multifactorial and common disease that leads to a decrease in the quality of life of individuals. The aim of this study was to determine the relationship between serum vitamin D and dental caries in the third year-to-last year students of dental school of Tehran University of Medical Sciences.
Materials and Methods: This descriptive cross-sectional study was conducted on 123 dental students. Demographic and health information were completed through a checklist. The level of vitamin D in individuals was measured by blood sampling. We recorded caries by ICDAS (international caries detection and assessment system) in two levels of D(1-6)MFT (total of decayed, filled and missing tooth) and D(3-6)MFT (total of progressive decayed, filled and missing tooth). Data analysis was done by the SPSS package version 25 using statistical tests of correlation and regression.
Results: The results showed that the correlation coefficient between vitamin D and caries index D(1-6)MFT was -0.89 with a P-value of 0.3328 which was not statistically significant. Based on the backward logistic regression, there was a positive significant statistical association between the D(3-6)MFT with vitamin D deficiency (P<0.001), weight (P=0.012), dental visit (P=0.023) and frequency of sweet snack consumption (P=0.03). In addition a significant and inverse statistical association was reported between the D(3-6)MFT and milk consumption (P=0.026).
Conclusion: Among dentistry students, no relation between vitamin D deficiency and early stages of decay was seen, however this relation was statistically significant in regard with progressive dental caries.

Background and Aims: Due to the very high importance of assessing the clinical performance of students, choosing the best assessment tool and method is one of the most important goals and tasks in medical education. The objective of this study was the development of a checklist for the assessment of dental students’ clinical skills of Tehran University of Medical Sciences, in the clinical complete denture course. The second aim was to determine the validity and reliability of the checklist, and The third aim was the evaluation of raters’ and students’ satisfaction.
Materials and Methods: The checklist was developed in expert panel sessions, and the validity and reliability of the checklist were assessed with CVI (content validity index) test-retest and inter-rater reliability methods, respectively. Students (n=15) were evaluated with a developed checklist. At the end of the session, the satisfaction level of staff and students were assessed. The obtained information was reported descriptively with the expression of mean and standard deviation and in the form of relative and absolute frequencies.
Results: The content validity index (CVI) of the checklist was 0.96. The reliability of the checklist confirmed with a high Intraclass Correlation Coefficient (>0.8) (between 0.82-0.97) (P<0.05). The coefficient of agreement in inter-rater reliability was 0.99 (between 0.991-0.998). Raters’ and students’ satisfaction earned a high percentage of satisfaction.
Conclusion: The designed checklist has the optimal features of a good students’ clinical performance assessment tool; it seems that using this checklist can be an excellent alternative method to a global rating scale to assess the clinical skills of dental students in the complete denture courses.

Background and Aims: Dental anxiety and fear can act as a barrier to seek dental care leading to insufficient oral health in people. The aim of this study was to determine the relations between dental fear and anxiety with dental caries status (DMFT) and clinical consequences of untreated dental caries (PUFA) among the adult patients referred to the faculty dental clinic of Tehran University of Medical Sciences.
Materials and Methods: In this cross-sectional study in 2019, the patients above 18 years old were assessed. Two standard questionnaires, Dental Fear Scale (DFS) and Modified Dental Anxiety Scale (MDAS), were used to assess the scores of dental fear, and dental anxiety, respectively. The demographic data of the patients were recorded. Dental caries status and clinical consequences of untreated dental caries, using DMFT and PUFA, respectively, were measured. Pearson correlation coefficients and multiple linear regression model (Backward method) were used for statistical analysis.
Results: Totally, 283 patients with the mean age of 38.6±11.8 years old participated. The mean scores of MDAS, and DFS were 12.04±4.49, and 41.33±16.87, respectively. Educational level (P=0.03, β=-0.14) and marital status (P=0.01, β=0.17) had significant relationships with MDAS scores. Moreover, a significant relationship was found between marital status and DFS scores (P<0.001, β=0.25). Significant correlations were found between dental anxiety level and D (P<0.001, r=0.36) and M components (P=0.02, r=0.14) of DMFT index. Moreover, there was a significant correlation between dental anxiety and U components of PUFA index (P=0.045, r=-0.12). Furthermore, the correlations between dental fear and D and M component of DMFT were significant (P<0.001, r=0.36; P<0.001, r=0.23; respectively).
Conclusion: Dental anxiety and dental fear were infrequent in the studied population; however, significant relationships were found between dental anxiety and dental fear with dental caries indices. Therefore, it was concluded that the more MDAS and DFS scores, the worse dental caries status.

Background and Aims: With increasing age and inability to maintain good oral hygiene, the chances of tooth loss increase and the need for dental implants will increase in the future. It also increases the risk of developing peripheral implants, especially at older ages in the failure of implant treatments. Recently, the high prevalence of cardiovascular disease and peri-implantitis in the elderly has been reported. The aim of this study was to investigate the effect of cardiovascular disease on the peri-implantitis in people with failed dental implants.
Materials and Methods: In this retrospective study, the files of patients referred to Shahid Montazeri Dental Clinic from 2009 to 2018 whose their failed implants were extracted, were collected. There were a total of 793 people with failed dental implants. The variables of this study were demographic information including age and sex, health status in terms of cardiovascular disease and peri-implantitis, which were identified and then statistically analyzed by examining the files of patients with these two variables. Data were statistically analyzed by SPSS25 statistical software and Chi-square was used to determine the effective variables.
Results: A total of 793 patients had failed dental implants, including 368 women (46.4%) and 425 men (53.6%) with an average age of 50.79 years. 42 patients (5.3%) had heart disease and 44 (5.5%) had peri-implantitis. According to the Chi-squared test, the significance level was less than 0.05 (P=0.011).
Conclusion: The results of this study showed that the cardiovascular disease and peri-implantitis were significantly related.

Background and Aims: Radiography is one of the most important para-clinical methods in diagnosing and selecting treatment in dentistry. Due to the potential dangers of X-rays for patients, the professional responsibility of the dentist requires that unnecessary radiographs to be avoided. The aim of this study was to investigate the awareness of dentists in Zanjan about the principles of radiation protection in 2019.
Materials and Methods: This cross-sectional study was performed on 107 general dentists and specialists working in Zanjan and the questionnaires were distributed among them. The level of awareness of dentists in 27 questions of radiographic prescribing questionnaire was evaluated and in each of the mentioned questions, their gender, age, work experience, participation in retraining, having X-ray machine in the field of dentistry and type of activity were evaluated. Data were analyzed by Chi-square test, Independent T-test, and ANOVA using SPSS software version 22.
Results: The results showed that the level of knowledge of general dentists about the principles of radiation protection (14.35±3.08) was lower than that of specialized dentists (17.19±2.35). Those who participated in retraining workshops (13.85±2.99) had less knowledge than those who did not (15.97±3.97), which was statistically significant (P<0.05); However, there was no significant difference in the dentists' knowledge about the principles of radiation protection based on gender, age, type of activity, having an X-ray machine at the place of treatment, and history of clinical experience (P≥0.05).
Conclusion: Awareness of dentists at various levels was moderate. Therefore, designing and holding more purposeful retraining courses to maintain and improve the level of awareness of dentists according to the guidelines provided by the authorities, still seems to be necessary.

Background and Aims: Regarding the need for social accountability in dental education, community-based dental courses has been established to improve the oral health of the community and compensate the shortcomings of the health system. Due to the importance of evaluation, the aim of this study was to determine the dental students’ attitudes and believes in the last year of their study towards the community-based dental education.
Materials and Methods: This cross-sectional study was performed on 159 dental students in the sixth year (October and February, 2018) of Isfahan dental school by census. These students took the relevant questionnaire, which was developed by researchers in three sections of “attitudes toward field activities”, “lessons and experiences of field activities during dentistry training” and “barriers and problems of field activities”. Its content and face validity was confirmed. They completed it on their own and after collecting information and descriptive analyzes, the relationship between the gender and entry group with attitude scores was analyzed by Mann-Whitney U test.
Results: Out of a total of 102 questionnaires which were answered (response rate of 64%), half of the students believed in the need to provide dental services in the form of mobile/outreach services for the community. 90% of the students agreed with the combination of field education with routine education in the dental schools. They also considered these services as an opportunity to use their experiences and knowledge to promote oral health in the community. 84% of them believed that their self confidence improved while providing services outside the faculty. In many of the propositions in the field of attitude to provide service in the field, a significant percentage (50 to 60%) did not have an opinion.
Conclusion: There was a good and positive aspects in many areas of attitude toward providing services in social fields as well as attitude towards the lessons learned from community-based dental education. However, we should consider the attitude-emotional aspects of educational objectives in the community-based courses in dental schools.