Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 15 2 2018 02 27 69 78 EN Saied Nokar Associate Professor, Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Mehran Bahrami Assistant Professor, Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Azam Sadat Mostafavi Assistant Professor, Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran 2017 05 25 2017 12 08 Objectives: The aim of this study was to investigate the stress distribution of different post and core materials in radicular dentin by three-dimensional finite element analysis (3D FEA). Materials and Methods: Twelve 3D models of a maxillary central incisor were simulated in the ANSYS 5.4 software program. The models were divided into three groups; the first group included: 1-Gold post and core and 2-Nickel-chromium (Ni-Cr) post and core restored with metal-ceramic restorations (MCRs). The second group included: 1-Stainless steel post, 2-Titanium post, 3-Carbon fiber post, 4-Glass fiber post, and 5-Quartz fiber post with composite cores and MCRs. The third group included: 1-Zirconia post and core, 2-Zirconia post, 3-Carbon fiber post, 4-Glass fiber post, and 5-Quartz fiber post; the last four models had composite cores restored with all-ceramic restorations (ACRs). Each specimen was subjected to a compressive load at a 45-degree angle relative to its longitudinal axis at a constant intensity of 100 N. The models were analyzed with regard to the stress distribution in dentin. Results: Two stress concentration sites were detected in the models. The first group showed the lowest stress levels in the cervical region, while the stress levels detected in the second group were higher than those in the first group and lower than those found in the third group. Fiber-reinforced posts induced a higher stress concentration between the middle and cervical thirds of the root compared to other posts. Conclusions: According to the results, since cast posts induce lower stresses in dentin, they are recommended for clinical use. Fiber-reinforced posts and ACRs caused the maximum stresses in dentin. https://fid.tums.ac.ir/index.php/fid/article/view/1922 https://fid.tums.ac.ir/index.php/fid/article/download/1922/993

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 15 2 2018 02 27 79 85 EN Alireza Mahdavi Associate Professor, Department of Anesthesia, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Masoud Fallahinejad Ghajari Professor, Dental Research Center, Research Institute of Dental Sciences, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Ghassem Ansari Professor, Dental Research Center, Research Institute of Dental Sciences, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Leila Shafiei Assistant Professor, Department of Pediatric Dentistry, Kerman University of Medical Sciences, Kerman, Iran 2017 06 09 2017 11 11 Objectives: The aim of this study was to compare the intranasal premedication effect of newly introduced dexmedetomidine (DEX) versus midazolam on the behavior of uncooperative children in the dental clinic. Materials and Methods: This crossover double-blind clinical trial was conducted on 20 uncooperative children aged 2-6 years who required at least two similar dental treatment visits. The subjects were randomly given 1 µg/kg of DEX and 0.5 mg/kg of midazolam via the intranasal route. For the sedation protocol in the two groups, 0.25 mg/kg of atropine in combination with 0.5 mg/kg of midazolam added to 1-2 mg/kg of ketamine were used 30 minutes after premedication and transferring the patient to the operating room. Dental treatments were carried out by a pediatric dentist blinded to the type of the administered premedication. The sedative efficacy (overall success rate) of the agents was assessed by two independent pediatric dentists based on the Houpt scale. Data analyses were carried out according to Wilcoxon signed-rank test and paired t-test. Results: There were no significant differences in the premedication efficacy of intranasal DEX and midazolam according to the Houpt scale (P>0.05). Conclusions: Intranasal midazolam and DEX are satisfactory and effective premedication regimens for uncooperative children. https://fid.tums.ac.ir/index.php/fid/article/view/1948 https://fid.tums.ac.ir/index.php/fid/article/download/1948/994

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 15 2 2018 02 27 86 96 EN Fereydoon Sargolzaei Aval Associate Professor, Cellular and Molecular Research Center, Department of Anatomical Sciences, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran Mohammad Reza Arab Professor, Cellular and Molecular Research Center, Department of Anatomical Sciences, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran Narjes Sargolzaei Assistant Professor, Department of Community Medicine, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran Fateme Noushadi Lecturer, Department of Anatomical Sciences, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran Abdolsamad Eteghadi Lecturer, Department of Anatomical Sciences, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran Asadollah Keykhaei Lecturer, Department of Anatomical Sciences, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran Foroug Sargolzaei Aval General Practitioner, Private Practice, Seattle, Washington, USA Azim Hedayat Pour Assistant Professor, Department of Anatomical Sciences, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran 2017 09 11 2018 01 03 Objectives: The healing of bone defects in the craniofacial region is an important clinical issue. We aimed to compare the effects of octacalcium phosphate (OCP) and the combination of OCP/gelatin (OCP/Gel) on calvarial bone regeneration in rats. Materials and Methods: In this study, 72 male Sprague Dawley rats were randomly assigned to the OCP (n=24), OCP/Gel (n=24), and control groups (n=24). Lesions with a diameter of 9 mm were created in the parietal bone and were filled with 9-mg OCP and OCP/Gel disks. In the control group, no substance was implanted in the defect. Sampling was performed on days 10, 14, 21, and 28 after the implantation. After tissue processing, 5-µm sections were prepared and stained by hematoxylin and eosin (H&E) stain. The sections were studied, and the volume fraction of the newly formed bone was assessed by Kruskal-Wallis test at a significance level of 0.05. Results: In the experimental groups, new bone formation was detected at the margins of the defects 10 days after the implantation. With the progression of the healing process, the newly formed bone covered greater areas of the defects and developed a more mature structure. In the control group, the defects were primarily filled with a dense connective tissue with small islands of new bone. The results of histomorphometric assessments showed that the volume of the newly formed bone in the experimental groups had a significant statistical difference with that in the control group (P<0.001). Conclusions: The OCP/Gel composite can be useful in the healing process of calvarial bone defects. https://fid.tums.ac.ir/index.php/fid/article/view/2136 https://fid.tums.ac.ir/index.php/fid/article/download/2136/995

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 15 2 2018 02 27 97 105 EN Leyla Sadighpour Associate Professor, Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Farideh Geramipanah Professor, Dental Implant Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Akbar Fazel Professor, Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Mahdi Allahdadi Postgraduate Student, Department of Restorative Dentistry, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mohamad Javad KharaziFard PhD Candidate of Epidemiology, Department of Biostatistics and Epidemiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran 2017 06 21 2017 10 31 Objectives: The aim of this study was to evaluate the retention strength of zirconia crowns luted with two types of resin cement under environmental pressure changes. Materials and Methods: Thirty zirconia crowns were fabricated by using computer-aided design/computer-aided manufacturing (CAD/CAM) system and were cemented by Panavia F2.0 (PAN), hand-mixed RelyX Unicem (UNH), or auto-mix RelyX Unicem Aplicap (UNA) cements on the corresponding extracted human molars. The samples were randomly divided into three groups according to the cement type. After 3000 thermal cycles, the cemented crowns were subjected to 24 pressure cycles (0 to 5 atmospheres). The retention force (N) of the specimens was measured in a universal testing machine. To normalize the retentive force, the recorded force was divided by the surface area of each tooth for measuring the retentive strength (MPa). The mean retention strengths (and forces) of the groups were compared by using one-way analysis of variance (ANOVA) and Tukey’s honest significant difference (HSD) test (α=0.05). The failure modes were also examined by using a stereomicroscope. Results: The retention values related to the evaluated resin cements were significantly different; the UNA group showed the highest retention strength (6.45±0.35 MPa) followed by the UNH (4.99±0.47 MPa) and PAN (4.45±0.39 MPa, P<0.001) groups. The adhesive failure mode was predominant in all the groups. Conclusions: The choice of resin cements and their mixing methods, which lead to differences in porosity, may affect the retention strength of zirconia crowns. https://fid.tums.ac.ir/index.php/fid/article/view/2004 https://fid.tums.ac.ir/index.php/fid/article/download/2004/996

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 15 2 2018 02 27 106 115 EN Maryam Memarian Associate Professor, Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Simindokht Zarrati Assistant Professor, Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Sedigheh Karimi Prosthodontist, Private Practice, Tehran, Iran Mehran Bahrami Assistant Professor, Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran 2017 07 03 2017 11 23 Objectives: The retentive properties of implant-retained overdentures (IRO) may be influenced by the type of attachments. The aim of this research was to compare the retention of two dental implant systems with compatible ball attachments, namely Straumann® system (SS) and Rhein83 SRL system (RS) after fatigue testing. Materials and Methods: Two laboratory models consisting of two parallel Straumann® fixtures at a distance of 22 mm were prepared. Five pairs of each systems' ball attachments were examined (n=5). The samples were soaked in artificial saliva. The retention strength values (RSV) were recorded before the fatigue test and after 1100, 2200, 3300, 4400, and 5500 insertion and removal cycles at a speed of 51 mm/minute with a 50-N load cell in a universal testing machine. The data were analyzed by repeated measures analysis of variance (ANOVA) followed by independent sample t-test with Bonferroni corrections. Results: There was a decrease in the RSV in both systems after 5500 cycles of insertion and removal. There was a significant statistical difference between the RSV of the normal Sphero Block of the RS (17.52±0.68 N) and that of the Spare Lamella retention inserts of the SS (19.72±0.74 N, P=0.001). Conclusions: Although the RSVs of the RS and SS were almost similar before the fatigue test, as the number of insertion and removal cycles increased, the RSV decreased more significantly in the RS compared to the SS. https://fid.tums.ac.ir/index.php/fid/article/view/2024 https://fid.tums.ac.ir/index.php/fid/article/download/2024/997

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 15 2 2018 02 27 116 122 EN Maryam Kazemipoor Assistant Professor, Department of Endodontics, School of Dentistry, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Niloofar Azizi Dentist, Private Practice, Yazd, Iran Farnaz Farahat Assistant Professor, Department of Operative Dentistry, School of Dentistry, Shahid Sadoughi University of Medical Sciences, Yazd, Iran 2017 07 09 2017 12 04 Objectives: The purpose of this research was to evaluate the effect of immediate placement of different restorative materials in comparison with a temporary restoration on the surface microhardness of mineral trioxide aggregate (MTA). Materials and Methods: Access cavities were prepared in 40 extracted human molars, and a 3-mm layer of MTA was placed in the pulp chamber. The samples were divided into eight groups (n=5). Ten minutes after the MTA placement, two groups were restored with Zonalin temporary restoration, while the other six groups were restored with glass-ionomer cement (GIC), resin-modified glass-ionomer (RMGI), or resin-based composite. In each group, the Vickers microhardness (VMH) of MTA was determined after 7 and 21 days. Data were entered into SPSS 17 software program and were analyzed by two-way analysis of variance (ANOVA). The significance level was set at 5%. Results: The type of restorative materials had a statistically significant effect on the microhardness of MTA (P=0.002). However, the microhardness of MTA was neither significantly influenced by the timing of final restoration (P=0.246) nor by the time-material interaction (P=0.116). Conclusions: Based on the results of the present study and by considering the limitations of laboratory studies, it is recommended to postpone the placement of final restorations until the underlying MTA is completely set. Otherwise, in the clinical conditions in which early covering of MTA is recommended, sufficient moist-curing and hydration should be guaranteed by selecting a restorative material with the lowest hydrophilic interaction energy. https://fid.tums.ac.ir/index.php/fid/article/view/2040 https://fid.tums.ac.ir/index.php/fid/article/download/2040/998

Tehran University of Medical Sciences Frontiers itory of several surgical procedures and/or antibiotic therapy due to misdiagnosis. After comprehensive examinations, root canal treatment was performed. The resolution of signs and symptoms during the follow-up period confirmed the correct diagnosis. Dermatologists and other physicians should be aware of the possibility of the relationship of extraoral sinus tracts with dental infections. Precise examination and taking a comprehensive history can aid to prevent unnecessary and incorrect therapeutic and/or pharmaceutical interventions. Elimination of dental infection leads to complete recovery in such patients. https://fid.tums.ac.ir/index.php/fid/article/view/3499 https://fid.tums.ac.ir/index.php/fid/article/download/3499/1824

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 17 0 2021 01 06 3109 3109 Farahnaz Sharafeddin Department of Operative Dentistry, Biomaterials Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Somaye Bahrani Department of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran 2019 04 22 2020 11 10 Objectives: Glass ionomer cements (GICs) are among the most popular dental restorative materials, but their use is limited due to their clinical disadvantages. Many efforts have been made to improve the properties of these materials by adding various fillers. Incorporation of hydroxyapatite (HA) into the GICs is considered to improve the physical properties of restorations, and may prevent treatment failure. This study aimed to evaluate the surface roughness (Ra) of a conventional glass ionomer cement (CGIC), a resin-modified glass ionomer (RMGI) and a Zirconomer with and without micro-hydroxyapatite (µHA). Materials and Methods: This experimental study was conducted on 6 groups (n=10) including CGIC, CGIC + µHA, RMGI, RMGI + µHA, Zirconomer, and Zirconomer + µHA. A total of 60 disc-shaped samples (6 mm × 2 mm) were prepared in plastic molds and were stored in distilled water for 24 h. After polishing of the specimens, their Ra was measured by a profilometer in micrometers (µm). The data were analyzed using two and one-way ANOVA, Tukey's HSD test, and independent t-test. Results: Incorporation of µHA resulted in statistically significant differences in Ra between the study groups (P<0.05). Following the incorporation of µHA, the Ra significantly decreased in CGIC (P=0.013) and Zirconomer (P=0.003). However, addition of µHA to RMGI resulted in a significant increase in its Ra (P<0.001). Conclusion: Addition of µHA decreased the Ra of Zirconomer and CGIC, and increased the surface roughness of RMGI samples. https://fid.tums.ac.ir/index.php/fid/article/view/3109 https://fid.tums.ac.ir/index.php/fid/article/download/3109/1832

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 17 0 2020 11 09 2673 2673 EN Meisha Gul Department of Operative Dentistry, The Aga Khan University Hospital, Karachi, Pakistan AND Department of Pediatric Dentistry, Bahria University Medical and Dental College, Karachi, Pakistan Samira Adnan Department of Operative Dentistry, Jinnah Sindh Medical University, Karachi, Pakistan Fahad Umer Department of Operative Dentistry, The Aga Khan University Hospital, Karachi, Pakistan 2018 07 06 2018 11 08 Endodontic treatment of maxillary incisors may be considered straight forward. However, in some instances, they may exhibit aberrant morphology. One of these rare variations in tooth morphology is dens invaginatus. To improve the endodontic prognosis of such teeth, a detailed evaluation of the tooth under treatment is important, which requires comprehensive clinical and radiographic examinations, including periapical radiography and cone-beam computed tomography (CBCT), which is highly recommended whenever atypical root canal morphology is suspected on a periapical radiograph. The current case report discusses the diagnosis of type IV dens invaginatus in a maxillary lateral incisor using CBCT. https://fid.tums.ac.ir/index.php/fid/article/view/2673 https://fid.tums.ac.ir/index.php/fid/article/download/2673/1823

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 17 0 2021 01 06 3009 3009 Vandhana James Department of Conservative Dentistry and Endodontics, Tagore Dental College Melakkottaiyur Post, Rathinamangalam, Tamil Nadu, India Manavalan Madhubala Department of Conservative Dentistry and Endodontics, SRM Dental College, Ramapuram, Chennai, Tamil Nadu, India Shari Devarajan Department of Conserva