Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 6 2016 02 28 389 397 Simindokht Zarrati Mehran Bahrami Fatemeh Heidari Jamal Kashani 2015 11 28 2015 11 28 Objectives: This finite element method study aimed to compare the amount of stress on an isolated mandibular second premolar in two conventional reciprocal parallel interface designs of removable partial dentures (RPDs) and the same RPD abutment tooth (not isolated). Materials and Methods: A Kennedy Class 1, modification 1 RPD framework was simulated on a 3D model of mandible with three different designs: an isolated tooth with a mesial rest, an isolated tooth with mesial and distal rests and an abutment with a mesial rest (which was not isolated); 26 N occlusal forces were exerted bilaterally on the first molar sites. Stress on the abutment teeth was analyzed using Cosmos Works 2009 Software. Results: In all designs, the abutment tooth stress concentration was located in the buccal alveolar crest. In the first model, the von Mises stress distribution in the contact area of I-bar clasp and cervical portion of the tooth was 19 MPa and the maximum stress was 30 MPa. In the second model, the maximum von Mises stress distribution was 15 MPa in the cervical of the tooth. In the third model, the maximum von Mises stress was located in the cervical of the tooth and the distal proximal plate. Conclusion: We recommend using both mesial and distal rests on the distal abutment teeth of distal extension RPDs. The abutment of an extension base RPD, which is not isolated in presence of its neighboring more anterior tooth, may have a better biomechanical prognosis.        https://fid.tums.ac.ir/index.php/fid/article/view/905 https://fid.tums.ac.ir/index.php/fid/article/download/905/770

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 6 2016 02 28 456 459 Singh Shikha Prasad Guru R Pathak Ashutoshdutt Sood Meenakshi 2015 11 28 2015 11 28 Myiasis is a rare disease caused by infestation of tissue by larvae of flies. Oral myiasis is still “rare” and “unique” owing to the fact that oral cavity rarely provides the necessary habitat for a larval lifecycle. Herein, we present a case of extensive gingival myiasis in a 12-year-old mentally retarded, epileptic child as well as a literature review. https://fid.tums.ac.ir/index.php/fid/article/view/914 https://fid.tums.ac.ir/index.php/fid/article/download/914/778

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 6 2016 02 28 398 408 Gayatri Sheena Suvarna Ramesh Khandurao Nadiger Omkar Shetty 2015 11 28 2015 11 28 Objectives: The aim of this in-vitro study was to evaluate the effect of topical fluoride on surface of cast titanium and nickel-chromium. Materials and Methods: Thirty-nine rectangular specimens of titanium (grade 2) and 39 rectangular specimens of nickel-chromium were cast in equal dimensions and divided into three groups of 13 samples each. Group one specimens of titanium and nickel-chromium were placed in 2% neutral sodium fluoride (NaF) solution for 16 minutes. Group two specimens of titanium and nickel-chromium were immersed in 1.23% acidulated phosphate fluoride (APF) gel for eight minutes. Group three specimens of titanium and nickel-chromium were immersed in distilled water for 16 minutes. The surface roughness of the specimens was evaluated and the data were analyzed using two-way ANOVA and post-hoc comparison test with the level of significance set at 5% (P< 0.05). The surface of the specimens was further analyzed using a scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Results: Group two titanium specimens showed a statistically significant increase in surface roughness (P<0.05); but no statistically significant increase was noted in the surface roughness of nickel-chromium specimens in groups one, two and three (P>0.05). Qualitative SEM and EDS analyses further revealed the surface corrosion of titanium (group two) and localized mild corrosive pitting of nickel-chromium specimens (group two). Conclusion: Topical fluoride with acidic pH affects the surface roughness of titanium and to a certain extent, nickel-chromium. Neutral NaF solutions cause no significant change in corrosion resistance of titanium or nickel-chromium. https://fid.tums.ac.ir/index.php/fid/article/view/906 https://fid.tums.ac.ir/index.php/fid/article/download/906/771

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 6 2016 02 28 460 468 Mehrfam Khoshkhounejad Noushin Shokouhinejad Salma Pirmoazen 2015 11 28 2015 11 28 Endodontic intervention in necrotic immature permanent teeth is usually a clinical challenge. With appropriate case selection, regenerative treatment can be effective, providing a desirable outcome. However, there is still no consensus on the optimal disinfection protocol or the method to achieve predictable clinical outcome. This article presents two cases of regenerative treatment in necrotic immature teeth, using mineral trioxide aggregate (MTA) and BiodentineTM as coronal barriers and different irrigants, which led to different clinical outcomes. https://fid.tums.ac.ir/index.php/fid/article/view/915 https://fid.tums.ac.ir/index.php/fid/article/download/915/779

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 6 2016 02 28 409 413 Amirfarhang Miresmaeili Najmeh Mollaei Ramin Azar Nasrin Farhadian Khosrou Mani Kashani 2015 11 28 2015 11 28 Objectives: Bone remodeling occurs during orthodontic treatment; this process enables tooth movement. Many factors can affect bone remodeling at the cellular level, such as nutritional supplements that can affect tooth movement. The present study was designed to evaluate the effect of dietary vitamin C on orthodontic tooth movement in rats.  Materials and Methods: This study was carried out on 36 six-week male Wistar rats with a mean weight of 225+32 g, which were randomly allocated to two equal groups. Rats in the case group received 1wt% vitamin C in their daily water. Opening springs were placed on the incisor teeth of both case and control groups. After 17 days, rats were sacrificed; the distance between the mesio-incisal angles of these teeth was measured with a digital caliper. Histological sections were made containing incisor teeth and alveolar bone and stained by hematoxylin-eosin. The number of resorption lacunae was evaluated using light microscopy. Results: Our findings showed that the amount of tooth movement in the vitamin C group was significantly higher than that in the control group (P<0.001). The osteoclast counts were significantly higher in vitamin C group (P=0.036). Conclusion: Oral vitamin C can increase orthodontic tooth movement in rats with more osteoclast lacunae around root in the pressure area.  https://fid.tums.ac.ir/index.php/fid/article/view/907 https://fid.tums.ac.ir/index.php/fid/article/download/907/772

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 6 2016 02 28 414 423 Minoo Mahshid Naeem Berijani Seyed Jalil Sadr Farhad Tabatabaian Sepide Sorour Homayoon 2015 11 28 2015 11 28 Objectives: Studies on the effect of coloring procedures on the bond strength of zirconia to resin cement are lacking in the literature. This study evaluated the effect of dipping of zirconia ceramic in different liquid color shades on the microtensile bond strength (MTBS) of zirconia ceramic to resin cement. Materials and Methods: This in vitro study was conducted on 100 microbar specimens divided into five groups of B2, C1, D4, A3 and control (not colored). To prepare the microbars, 20 white zirconia ceramic blocks, measuring 5×11×11 mm, were dipped in A3, B2, C1 or D4 liquid color shades for 10 seconds (five blocks for each color shade) and five blocks were not colored as controls. All the zirconia blocks were sintered in a sintering furnace. Composite blocks of similar dimensions were fabricated and bonded to zirconia ceramic blocks using Panavia F 2.0 resin cement. Zirconia-cement-composite blocks were sectioned into microbars measuring 1×1×10 mm. The MTBS of microbars was measured by a testing machine. Data were analyzed using one-way ANOVA and Tukey’s test. All tests were carried out at 0.05 level of significance. Results: Statistically significant differences were found among the groups in MTBS (P<0.001). The D4 group had the highest MTBS value (39.16 ± 6.52 MPa). Conclusion: Dipping affected the MTBS of zirconia ceramic to Panavia F 2.0 resin cement; however, a similar pattern of change was not seen due to the different liquid color shades. https://fid.tums.ac.ir/index.php/fid/article/view/908 https://fid.tums.ac.ir/index.php/fid/article/download/908/773

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 6 2016 02 28 424 429 Neda Shams Mahmood Ghasemi Saeed Sadatmansouri Shahin Bonakdar 2015 11 28 2015 11 28 Objectives: Osteoblasts are the most important cells in the osseointegration process. Despite years of study on dental Implants, limited studies have discussed the effect of saliva on the adhesion process of osteoblasts to implant surfaces. The aim of this in vitro study was to evaluate the effect of saliva on morphology and differentiation of osteoblasts attached to implant surfaces. Materials and Methods: Twelve Axiom dental implants were divided into two groups. Implants of the case group were placed in containers, containing saliva, for 40 minutes. Then, all the implants were separately stored in a medium containing MG63 human osteoblasts for a week. Cell morphology and differentiation were assessed using a scanning electron microscope and their alkaline phosphatase (ALP) activity was determined. The t-test was used to compare the two groups. Results: Scanning electron microscopic observation of osteoblasts revealed round or square cells with fewer and shorter cellular processes in saliva contaminated samples, whereas elongated, fusiform and well-defined cell processes were seen in the control group. ALP level was significantly lower in case compared to control group (P<0.05). Conclusion: Saliva contamination alters osteoblast morphology and differentiation and may subsequently interfere with successful osseointegration. Thus, saliva contamination of bone and implant must be prevented or minimized. https://fid.tums.ac.ir/index.php/fid/article/view/909 https://fid.tums.ac.ir/index.php/fid/article/download/909/847

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 6 2016 02 28 430 435 Sara Rahimian-Imam Nahid Ramazani Mohammad Reza Fayazi 2015 11 28 2015 11 28 Objectives: Application of sealants is a safe and effective way to prevent occlusal caries in the posterior teeth. A successful sealant therapy depends on good isolation. Decreased steps of adhesive application may enable proper isolation and use of self-adhering flowable composites for sealant therapy. This study sought to compare the marginal microleakage of fissure sealants and self-adhering flowable composites in permanent teeth. Materials and Methods: This in vitro, experimental study was conducted on 60 extracted human premolar teeth. The teeth were divided randomly into two groups of 30. In the first group, fissure sealant (Clinpro, 3M ESPE, USA) was placed on the teeth. In the second group, self-adhering flowable composite (Vertise Flow, Kerr, USA) was applied as the sealant. Then, both groups were immersed in 0.5% fuchsin dye solution for 24 hours. Sectioned samples were observed with a stereomicroscope for the extent of dye penetration. Data were analyzed using SPSS 21 and the Mann-Whitney test (P<0.05). Results: Microleakage in the fissure sealant group was significantly higher than that in the self-adhering flowable composite group (P<0.001). Conclusion: Microleakage was less using self-adhering flowable composite compared to conventional fissure sealant; therefore, self-adhering flowable composite can be used as a suitable fissure sealant in permanent teeth. https://fid.tums.ac.ir/index.php/fid/article/view/910 https://fid.tums.ac.ir/index.php/fid/article/download/910/775

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 6 2016 02 28 436 446 Hamidreza Pakshir Shabnam Ajami 2015 11 28 2015 11 28 Objectives: This study aimed to compare the microleakage beneath metallic brackets following two different methods of enamel preparation and light curing. Materials and Methods: A total of 120 bovine deciduous lower incisors were randomly divided into four groups of 30 teeth. The preparations were as follows: Group I: Acid etching + Transbond XT primer + direct illumination, group II: acid etching + Transbond XT primer + transillumination, group III: Transbond XT self-etching primer + direct illumination and Group IV: Transbond XT self-etching primer + transillumination. Dye penetration was used as the method of microleakage evaluation. Sections made at the enamel-adhesive and adhesive-bracket interfaces were evaluated under a stereomicroscope. The Kruskal-Wallis and Mann-Whitney U tests were used for statistical analysis. The level of significance was set at P<0.05. Results: All groups showed greater microleakage at the gingival in comparison to the incisal margin and the differences were significant among groups with transillumination (P<0.001). No significant differences were observed in the microleakage scores at the gingival and incisal margins in any of the interfaces (P>0.05). Mesiodistal margins of the self-etching group with direct illumination showed sA;C, the swab samples were taken and cultured in blood agar. The S. mutans colonies were counted by unaided vision after 48 hours of incubation. The results were analyzed using ANOVA followed by the Tukey’s test. Results:The number of colonies attributed to enamel, GI, and BisCem blocks was 24±2, 24.2±2.7 and 14.8±1.7 colonies/mm2, respectively. There was no difference between enamel and GI in terms of adhesion of S. mutans (P=0.08 and P>0.001, respectively); however, the difference between these two and BisCem was statistically significant (P= 0.00075 and P<0.001, respectively). Conclusion:Within the limitations of this study, BisCem cement is superior to GI for the cementation of indirect restorations.   Objectives: Considering the adhesion of some microorganisms such as Streptococcus mutans (S. mutans) to restorative materials and the unrecognized consequences of this phenomenon, and due to the controversies in this regard, it is important to discover the materials to which the lowest adhesion of S. mutans occurs. The objective of this study was to assess the level of adhesion of S. mutans to glass ionomer (GI), BisCem Cement and enamel. Materials and Methods:In this in vitro experimental study, 12 specimens including five GI blocks (GC America Inc., Alsip, IL, USA), five BisCem blocks (Bisco Inc., Schaumburg, IL, USA) and two enamel blocks were exposed to a bacterial suspension (1×106 mg/mL). After incubation for one hour at 37˚C, the swab samples were taken and cultured in blood agar. The S. mutans colonies were counted by unaided vision after 48 hours of incubation. The results were analyzed using ANOVA followed by the Tukey’s test. Results:The number of colonies attributed to enamel, GI, and BisCem blocks was 24±2, 24.2±2.7 and 14.8±1.7 colonies/mm2, respectively. There was no difference between enamel and GI in terms of adhesion of S. mutans (P=0.08 and P>0.001, respectively); however, the difference between these two and BisCem was statistically significant (P= 0.00075 and P<0.001, respectively). Conclusion:Within the limitations of this study, BisCem cement is superior to GI for the cementation of indirect restorations. Keywords: Bacterial Adhesion; Streptococcus mutans; Glass Ionomer Cements; BisCem cement https://fid.tums.ac.ir/index.php/fid/article/view/1071 https://fid.tums.ac.ir/index.php/fid/article/download/1071/824

Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 9 2016 05 07 686 694 Shahin Kasraei Loghman Rezaei-Soufi Ebrahim Yarmohamadi Amanj Shabani 2016 02 16 Objectives: Because of poor bond between resin cement and zirconia ceramics, laser surface treatments have been suggested to improve adhesion. The present study evaluated the effect of CO2 and Nd:YAG lasers on the shear bond strength (SBS) of resin cement to zirconia ceramic. Materials and Metho