مجله دانشکده دندانپزشکی مشهد
سال چهل و دوم شماره 1 (پیاپی 104، بهار 1397)

Radiography plays a key role in the diagnosis, planning, and efficacy of treatment. Dentists with various levels of knowledge and conduct use intraoral radiography devices. The present study aimed to examine the radiography equipment and evaluate the compliance with the principles of radiation protection in the dental offices in Mashhad, Iran.
This cross-sectional, descriptive-analytical study was conducted in 232 dental offices employing intraoral radiographic devices in 2015. Demographic data of the dentists, participation in educational courses, application of dosimeters, protection methods for patients and personnel, and the device features were recorded. Data analysis was performed in SPSS version 19.
In this study, 22.9% of the radiography devices were equipped with digital systems. The application of the E-speed film and angle bisector technique was estimated at 77.1% and 79.7%, respectively. Most dental offices did not use thyroid shields (61.6%) and lead aprons (54.7%). Among the methods of personnel protection, lead screen (47.4%) and maintaining distance (30.2%) were used more frequently compared to the other approaches. In 65% of the dental offices, quality control of the devices was performed every year. Mean score of compliance with the principles of protection was 42.9%, and radiation protection was at a moderate level in 77% of the dental offices. Additionally, no significant association was observed between the observance of protection principles with gender and work experience of the dentists.
Several radiographic devices are used for improving imaging quality and reducing the absorbed radiation dose in patients. Considering the moderate level of compliance with the principles of radiation protection in most of the studied dental offices in Mashhad, it is recommended that training courses be offered in this regard for the accurate monitoring of these principles in the application radiography devices in dental offices.

Fissure sealant is used to reduce the incidence of occlusal decays. Recently, resin substances have been significantly developed, one of which is infiltrating resin Icon .This study aimed to compare fissure sealant from 3M ESPE and infiltrating resin in terms of microleakage.
This experimental study was conducted on 40 extracted premolars with no decay and crack. These teeth were divided into two groups. The striae of occlusal surfaces of the teeth were covered by fissure sealant from 3M ESPE and infiltrating Icon resin according to the manufacturer’s recommendation. Thereafter, the teeth were thermocycled 500 times between 5°C to 55°C and finally placed in distilled water. The apex of all the teeth and divergence of the roots were sealed by sealing wax. The whole surfaces of dental root and crown were coated with two layers of nail varnish 1 mm from the sealant margin. The teeth were put in 0.5% volatile fuchsine at the temperature of 37°C to allow the coloring agent to penetrate to possible gaps between enamel and sealant. Then, the teeth were washed and cut off parallel to linear axis. The samples were studied in order to assess the amount of microleakage under the stereomicroscope with 36× magnification. The leakage was scored from 0 to 3. Data analysis was performed using Mann-Whitney U test.
There was no significant difference between fissure sealant from 3M ESPE and infiltrating resin in terms of microleakage (P=0.512).
According to the results, the use of fissure sealant was more cost-effective and less time-consuming than the Icon material.

Given the importance of randomized clinical trials (RCTs) in the evidence-based approach in dentistry, the study aimed to conduct critical appraisal of dentistry RCTs of Iran published in English from 1999 until 2012.
In total, databases of PubMED, ISI web of science and Scopus were searched using specific keywords (i.e., dental, dentistry, critical appraisal, clinical trial, evidence-based RCT, randomized clinical trial, Iran). After the elimination of duplicate articles, the 433 remaining articles were assessed, which led to the selection of 86 studies by employing the inclusion and exclusion criteria. Following that, the articles were evaluated using the revised version of Jadad scale.
In this research, mean jadad score was 5.33±1.73, and articles were at a moderate level (4 According to the results of the study, the methodological quality of the Iranian English dentistry articles was generally at a medium level, which requires improvement. Emphasis on standard instructions in designing the studies and using review checklists during the complication of a research, along with holding educational relevant workshops, can considerably improve the quality of Iranian articles.

This descriptive study aimed to evaluate root canal morphology of maxillary first premolars using cone beam computed tomography (CBCT).
Data were collected and registered using CBCT images of a maxillofacial imaging center that were simultaneously evaluated by a radiologist and an endodontist. The assessed variables included the number of roots and their morphology, number of canals, and direction of root curvature and canals in buccolingual and mesiodistal directions. Data analysis was performed using Chi-squared, exact Fischer’s, and Cohen's kappa coefficient tests. In all the measurements, P-value less than 0.05 was considered statistically significant.
In this study, 106 eligible CBCT showing 106 maxillary first premolars were evaluated, out of which, 34.5% of them were from male and 65.5% were from female individuals. Moreover, 67 teeth (57.8%) had only one root, and 48 teeth (41.4%) had two roots, and only 1 tooth (0.9%) had three roots. According to Vertucci et al. classification, out of 67 first premolars with one root, 19.4% (n=13), 56.7% (n=38), 11.9% (n=8), 1.5% (n=1), 7.5% (n=5), and 3% (n=2) of them were type I, II, III, IV, V, and VI, respectively.
Regarding the results, the majority of maxillary first premolars had one root with type II canals. Furthermore, maxillary first premolar might have curvature in any direction.

Methacrylate composite resins are widely used in restorative dentistry. The greatest disadvantage of these materials is polymerization shrinkage. The recent innovations include making silorane-based composites with the least amount of shrinkage. Herein, we sought to investigate micro-shear bond strength between the former and new composites using both bonding and composite systems.
Seventy-eight cylindrical methacrylate- and silorane-based composites with the height and diameter of 2 mm and 5 mm, respectively, were prepared and thermocycled for 1000 cycles for aging.Then, the blocks were divided into six subgroups: 1) Z250, after freshening and P90bonding, the new silorane layer was placed on them; 2) Z250, after freshening, acid etching, and P90bonding, the new silorane layer was attached; 3) Z250, after freshening, acid etching, and single bonding, the new Z250 layer was attached; 4) P90 composite, after freshening and P90bonding, the new silorane layer was attached; 5) P90, after freshening, acid etching, and P90bonding, the new silorane layer was attached; and 6) P90, after freshening, acid etching, and single bonding, the new Z250composite was attached. Then, all the bonded samples were tested for micro-shear bond strength by Instron machine at the speed of 1 mm/min; the samples were loaded until reaching the breaking point. To analyze the data, Kolmogorov–Smirnov test, one-way analysis of variance, and Tukey’s post hoc test were run in SPSS, version 17.
There was a significant difference in micro-shear bond strength between the groups (P=0.0001). The mean of micro-shear bond strength in the silorane-based composite group was significantly higher than that of the methacrylate-based composites (36.62±5.97 vs. 26.12±5.97; P=0.0001).
Acid etching does not significantly affect shear bond strength, but applying P90 bonding in silorane composites increases the shear bond strength. The greatest bond strength was observed in restoring the P90 silorane composite with a similar silorane composite and the least strength was found in restoring the Z250 methacrylate composite with a similar methacrylate composite. In general, the micro-shear bond strength of silorane-based composites was greater than that of the metacrylate-based composites.

Vitamin D is a secosteroid (pro)-hormone with multiple systematic effects, including the regulation of the immune system. Serum vitamin D level affects the progression of some diseases, such as psoriasis and oral cancer. The study aimed to measure the serum vitamin D level in patients with oral lichen planus (OLP), which is an autoimmune and precancerous disease.
This cross-sectional study was conducted on 66 patients with OLP and 30 healthy individuals. In addition, serum vitamin D level was measured by ELISA method, and data analysis was performed using Mann–Whitney U and t-test.
In this research, 26 (39.4%) patients with OLP had vitamin D deficiency and 31 (47.0%) subjects had an insufficient vitamin D level. On the other hand, 9 (30.0%) and 15 (50%) of the participants in the control group had vitamin D deficiency and insufficient vitamin D level, respectively. According to the results, no significant relationship was observed in the study groups regarding serum vitamin D levels. However, a reverse and significant correlation was found between age and vitamin D deficiency in the subjects (P=0.015).
According to the results of the study, low serum vitamin D levels were observed in a high percentage of patients with OLP. Given the prevalence of vitamin D deficiency in the society, extended research is required to evaluate the impact of this deficiency on pathogenesis of the disease.

CD44 is a cell surface adhesion glycoprotein found in various cells. The present study aimed to evaluate the immunohistochemical expression of CD44 in the erosive lichen planus (ELP), epithelial dysplasia (ED), and oral squamous cell carcinoma (OSCC) to compare the expression in a possible premalignant lesion, a definite premalignant lesion, and a malignancy.
In this descriptive-analytical study, immunohistochemical staining was performed on 10 ELP cases (without dysplasia), five ED cases, and 20 OSCC cases using the standard Envision technique. In addition, the extent and intensity of CD44 staining and thickness of the stained epithelium were assessed. Data analysis was performed in SPSS using Kruskal-Wallis test.
60% of OSCC samples had moderate membranous and cytoplasmic staining, in which more than two-thirds of the epithelium was stained. Moreover, moderate to severe, and mostly membranous immunostaining were observed in all ELP cases, while two-thirds of the epithelium showed immunostaining in all the samples. In the ED samples, staining intensity was reduced in more severe cases, and the staining pattern changed from membranous to cytoplasmic and membranous. Furthermore, in 80% of the ED cases, two-thirds of the epithelium was stained. Comparison of the immunostaining in ELP, ED, and OSCC samples indicated no significant differences between these lesions
According to the results, CD44 expression in ELP, ED, and OSCC had no statistically significant difference. Therefore, this protein might not be an appropriate marker to confirm the premalignancy of ELP or predict the invasion in OSCC and premalignant lesions.

Using scientific texts and new contents requires proper skills and experience in reading, evaluation, data analysis, and interpretation of valid findings. The present study aimed to assess the cognition of the postgraduate dental students, at Mashhad University of Medical Sciences (Iran) in the evaluation, data analysis, and interpretation of the findings of evidence-based studies.
This cross-sectional study was conducted on the postgraduate dental assistants at Mashhad University of Medical Sciences. Research instrument was a questionnaire consisting of four main sections, including the personal data of the participants, attitude toward statistics, ability to apply the results of studies, and cognition. Data analysis was performed in SPSS using independent t-test at the significance level of 0.05.
Out of 96 dental assistants, 62 cases were enrolled in the research. Among the participants, 42 cases (66.7%) were female, and 14 assistants (22.6%) had prior experience of participating in research, statistics, and epidemiology workshops. Mean score of attitude was 20.4±2.9 (out of 30), and the mean score of ability was 8.40±3.1 (out of 20). The frequency of correct answers to the items in the cognition section of the questionnaire was 36.4%, and no correlations were observed between the student's cognition, gender, and participation in statistics and research methodology workshops.
According to the results, cognition and ability of the students in identifying statistical methods and interpreting statistical analysis were poor. Therefore, it is recommended that the educational curriculum and teaching methods be revised in order to enhance the knowledge and ability of the students in this regard.

Viridnas streptococciare among the factors involved in dental caries and the subsequent diseases due to their ability in biofilm formation and the synthesis of extracellular polymers. Considering the difference in the resistance of biofilm forms and plankton pathogenic bacteria to bactericide agents, we aimed to compare the effect of chlorhexidine mouthwash and eugenol on planktonic and biofilm forms of viridnas streptococcito find the effective concentrations of the two products.
Viridans streptococci were isolated from 20 human dental plaque samples using biochemical tests. The strain with the highest biofilm formation activity was identified more precisely using 16SrRNA gene analysis. The effects of chlorhexidine (0.06-0.2 w/v%) and eugenol (29.7-99 w/v%) were assessed on the planktonic and biofilm cells of the isolated viridans streptococciusing macrodilution broth and polystyrene microplates, respectively. In addition, the minimum inhibitory concentration (MIC) of these antiseptics on the isolated viridans streptococci was determined.
Strain UTMC 2446 with 98.04% similarity to Streptococcus sanguinis had the highest biofilm production ability. The 0.2% and 99% concentrations of chlorhexidine and eugenol inhibited biofilm formation, respectively, while these compounds could effectively inhibit planktonic cell growth at the 0.14% and 79.2% concentrations, respectively.
For the tested compounds, the effective concentrations needed to inhibit biofilm formation were higher than those required for planktonic growth arrest. Moreover, due the possibility of emergence of resistant strains, as well as the fact that the required concentration is equal to the maximum concentration of the compounds in commercial products, their antimicrobial potential must be regularly monitored. Our findings can be beneficial for manufacturing and quality control facilities.

Oral malignant melanoma is a rare malignancy with a higher tendency to metastasize and locally invade tissues compared to the other malignant tumors of the oral cavity. Malignant melanoma of the oral cavity accounts for 0.2-8% of all the reported melanomas. The malignancy is approximately four times more frequent in the oral mucosa of the maxilla and normally occurs on the palate or alveolar gingiva. Malignant melanomas are often asymptomatic in the early stages and present as a pigmented patch or mass, delaying the diagnosis until the manifestation of symptoms such as swelling, ulceration, bleeding or the loosening of the teeth. The prognosis of the tumors is extremely poor, especially in the advanced stages.
Case Report: A 35-year-old female patient presented with chief complaint of a lesion on the posterior region of the right mandible for four months. Intraoral examination revealed a gray-black sessile exophytic buccolingual mass. Incisional biopsy of the lesion confirmed the histopathological diagnosis of an oral malignant melanoma.
Obtaining an accurate medical history and performing a thorough examination of the oral cavity are considered essential to the diagnosis of pigmented lesions. Meticulous assessment of the pigmented lesions in the oral cavity result in the early diagnosis, prompt treatment, and better prognosis of the possible malignancies.