Journal of Dental School, Shahid Beheshti University of Medical Sciences

Objectives Considering the growing knowledge about stem cells and the role of cell-based therapies in the future, dentists should have adequate knowledge about oral stem cell sources and their applications in dentistry. The present study assessed the knowledge and attitude of dental students and recent dental graduates towards dental pulp stem cells (DPSCs) in Iran.

Methods This descriptive cross-sectional study was performed in 2021 on 175 participants, including 86 dental students and 89 recent dental graduates from the Dental School of Rafsanjan University of Medical Sciences (RUMS), Rafsanjan, Iran and Dental School of Shahid Beheshti University of Medical Sciences (SBMU), Tehran, Iran. A researcher-designed questionnaire was used to collect data. The validity and reliability of the questionnaire were assessed. The data were analyzed by SPSS version 21 using the Kolmogorov-Smirnov test, independent t-test, and ANOVA.

Results The mean knowledge and attitude scores of the participants were 66.16±8.51% and 68.65±11.87%, respectively. The mean attitude score was significantly correlated with “interest in participating in the courses related to stem cells” and “scientific journal review rate”. The level of knowledge of the participants from SBMU was significantly higher than that of participants from RUMS (P<0.05). Other variables did not had a significant effect on the mean score of knowledge or attitude (P>0.05).

Conclusion Dental students had a positive attitude towards the application of stem cells; however, their knowledge was inadequate. Therefore, some appropriate measures must be adopted to enhance the knowledge of dental students about DPSCs, especially in universities with lower ranks.

Objectives The hyoid bone has a strategic position in the craniofacial region and has numerous vital functions. This study aimed to assess the hyoid bone position in patients with skeletal class I and class III malocclusion with cone-beam computed tomography (CBCT).

Methods The CBCT images of 30 patients with skeletal class I malocclusion and 30 patients with skeletal class III malocclusion were evaluated. The skeletal malocclusion pattern was determined based on the ANB angle. Horizontal, vertical, and angular measurements were made to determine the hyoid bone position on the CBCT images. Independent samples t-test, Mann Whitney U test, and Chi-square test were used for statistical analysis (alpha=0.05).

Results While the distances between the hyoid bone and the genial tubercles and the horizontal distance between the hyoid bone and the roof of the nasopharynx were found to be high in class III patients, the angle between the spina nasalis anterior, sella, and hyoid bone (ASH) was observed to be low in class III patients. The distance of the hyoid bone to the posterior nasal spine, its vertical distance from the roof of the nasopharynx, and the length and width of the hyoid bone did not show any significant difference between class I and class III patients.

Conclusion The hyoid bone position changed horizontally but not vertically in class III patients. It was also concluded that the hyoid bone dimensions were not affected by skeletal malocclusion.

Objectives Providing a reliable attachment between the bracket base and zirconia surface is a prerequisite for exertion of orthodontic forces. The purpose of the present study was to evaluate the effect of two surface treatment methods and three primers on shear bond strength (SBS) of orthodontic brackets to zirconia surface.

Methods Zirconia blocks were milled and embedded in acrylic resin. The polished zirconia surfaces were randomly prepared with sandblasting (SB) and Er:YAG laser application (LA). Each group of 45 (SB and LA) was further divided into 3 subgroups of 15.  The subgroups received different primers namely Z-Prime Plus, MKZ primer and Clearfil SE Bond Primer. The SBS values were measured and compared using two-way ANOVA. SPSS 21 for Macintosh was used for all statistical analyses. Level of significance was set at P<0.05.

Results The SB group exhibited a mean SBS of 14.393 MPa, which was significantly higher than the mean SBS recorded for LA group (5.683 MPa; P<0.05). In SB subgroups, there was no significant difference among the primers in SBS (P= 0.391), but this was not the case for laser subgroups (P< 0.05) and the subgroups that received Clearfil SE and Z-Prime Plus had higher SBS than the MKZ primer subgroup.

Conclusion This study suggests that simultaneous use of sandblasting and primers containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) monomer can result in acceptable SBS of brackets to zirconia surfaces.

Objectives This study sought to assess the cytotoxicity of zirconomer and conventional glass ionomer (CGI) for L929 murine fibroblasts over time.

Methods In this in vitro, experimental study, 48 discs were fabricated from FX-II CGI and Shofu zirconomer and divided into three groups (n=16) for assessment of extracts obtained after 15 minutes (group 1), 24 hours (group 2) and seven days (group 3) of incubation following their initial polymerization. L929 murine fibroblasts were cultured and after 24 hours, they were exposed to extracts of the 48 discs in 144 wells. Cell-culture plates were incubated for 24, 48 and 72 hours. Cytotoxicity was evaluated using the methyl thiazolyl tetrazolium (MTT) assay. Data were analyzed by one-way and two-way ANOVA, Tukey’s test and independent sample t-test (P<0.05).

Results At 24 hours, the 15-minute extract of both materials showed the highest cytotoxicity while the 7-day extract of the materials showed the lowest cytotoxicity. The 15-minute extract of zirconomer showed significantly higher cytotoxicity than CGI (P<0.05). At 48 hours, the cytotoxicity of 15-minute, 24-hour and 7-day extracts of zirconomer decreased. The results for CGI at 48 hours were similar to those at 24 hours. The 15-minute extract of zirconomer had significantly higher cytotoxicity than that of CGI (P<0.05). At 72 hours, the results in both groups were the same as those at 24 hours, and all zirconomer extracts showed significantly higher cytotoxicity than CGI extracts.

Conclusion The cytotoxicity of both materials decreased over time. Zirconomer showed higher cytotoxicity than CGI at all time points.

Objectives Drug abuse is a critical health problem in human societies. This study aimed to evaluate the prevalence and determinants of drug abuse among students in a medical university in Iran.

Methods This cross-sectional study was performed in 2016 on a convenient sample of 800 undergraduate students in a medical university in Tehran, Iran. Data were gathered by means of a self-administered questionnaire inquiring the students’ age, gender, marital status, home city, living status, smoking, and drug abuse including history, frequency and type. Statistical analyses were performed by the Chi-square test and logistic regression models. 

Results The mean age of the respondents was 23.5 years; 67% were males, and 70% were single. Totally, 15% of the students reported cigarette smoking and ≤ 6% used other drugs. The frequency of substance abuse by male students was significantly higher than that by female students (P<0.01). Alcohol consumption was reported by 7% of the students, and had a significantly higher frequency among females (P=0.02). Older students, those spending their free time alone, and those without a job had higher frequency of drug abuse (P≤0.001).

Conclusion Prevalence of drug abuse was low among medical students evaluated in this study, and most of them reported no smoking. Some demographic and lifestyle factors may predispose students to smoking and drug abuse. Provision of preventive programs including surveillance, consultation and treatment will help university students avoid such risky behaviors.

Objectives Hepatitis B is a life-threatening disease that affects the liver. Despite the availability of vaccines and drugs, the disease remains a major human health problem worldwide. The aim of this study was to evaluate the serum level of anti-HBs in dental students of Urmia Dental School.

Methods This descriptive study was performed on 72 (38 males, 34 females) dental students vaccinated against hepatitis B. Totally, 5 cc of venous blood was taken from each student and sent to a laboratory. In the laboratory, after serum separation, HBs antibody titer was measured by Bind Mono kit by ELISA. Data were analyzed using SPSS 21 by the Chi-square test.

Results The minimum and maximum antibody titers were zero and 1000 IU/mg, respectively. Assessment of the frequency of HBs-Ab adequacy showed that 7 (9.7%) students had no immune response, 23 (31.9%) had low safety level, and 42 (58.3%) had good and acceptable safety levels. There was no significant difference between males and females in this regard (P>0.05)..

Conclusion Most of the students were immune to the virus, although about 32% of them showed low immunity, indicating the need for re-vaccination. Seven out of 72 students were not immune to the disease.

Objectives This study assessed the dimensional distortion of four types of intracanal posts on cone-beam computed tomography (CBCT) scans with two different fields of view (FOV) in high and standard resolution modes.

Methods This in vitro study evaluated 40 extracted single-rooted maxillary central incisors that underwent root canal treatment. The teeth were randomly assigned to 4 groups (n=10) for placement of non-tapered brass, silver, titanium and stainless steel (SS) intracanal posts. The diameter of the posts was measured at two reference points by a digital caliper (gold standard). The teeth underwent CBCT with 8 x 8 and 8 x 12 cm FOV with high and standard resolution modes. The post diameters were measured on axial CBCT images at the same reference points and compared with the gold standard. Data were analyzed by ANOVA, and paired and independent sample t-test.

Results Significant differences were noted between the radiographic diameter of the posts and their actual size (P<0.05). Titanium posts (40.25%) showed minimum percentage of dimensional distortion followed by brass (54%), silver (62.5%) and SS (70.17%) posts. High-resolution images with 8 x 8 cm FOV yielded minimum dimensional distortion (40.6%) followed by high-resolution images with 8 x 12 cm FOV (45.75%), standard-resolution images with 8 x 8 cm FOV (68.75%), and standard-resolution images with 8 x 12 cm FOV (72.1%).

Conclusion All metal posts showed significant dimensional distortion on CBCT scans, irrespective of the FOV size and resolution mode. SS posts yielded maximum, and titanium posts showed minimum dimensional distortion.

Objectives Different root canal filling materials show different clinical and radiographic success rates. Since there is controversy on the best root canal filling material in primary dentition, the aim of this study was to summarize information about root canal filling materials for primary teeth in terms of biocompatibility, cytotoxicity, resorption rate, and survival rate.

Methods By searching online databases, studies that addressed biocompatibility, cytotoxicity, resorption, and survival rates of different root filling materials in primary teeth from 1985 to 2020 were evaluated and the required data were extracted. The results were tabulated and compared.

Results Due to methodological discrepancies, different studies show different and sometimes inconsistent results, which make it hard to reach a final conclusion; but it seems that Vitapex and Maisto's paste are more biocompatible and have a good survival rate. Zinc oxide eugenol (ZOE) and calcium hydroxide have lower cytotoxicity among different filling materials. However, due to low resorption rate, ZOE can affect permanent successors.

Conclusion Based on the unique characteristics of each patient, different filling materials may be used for a clinically optimal dental treatment.