modulus of elasticity
در نشریات گروه پزشکی-
Background
Nano-fluorohydroxyapatite (nano-FHA) is a caries preventive agent that is applied in many fields of dentistry and has the potential of being added to Essix retainers to create antibacterial properties.
ObjectivesThe purpose of this study was to investigate the effect of nano-fluorohydroxyapatite addition on the tensile strength and modulus of elasticity of an Essix plate.
MethodsThe nano-fluorohydroxyapatite was synthesized and added to an Essix plate in various weight percentages: 0% (group 1), 0.1% (group 2) and 0.5% (group 3). We performed the measuring of flexural strength and modulus of elasticity for the experimented three groups using a universal testing machine. The data were analyzed through one-way ANOVA and Tukey’s test at the significance level of 0.05.
ResultsAccordingly, the obtained results were indicative of significant differences between the groups (P-value = 0.003); however, the difference between group 2 and control group was not statistically notable (P-value = 0.427). Furthermore, the tensile strength of group 3 significantly decreased (P-value = 0.04). In regards to the modulus of elasticity, the data were suggestive of significant differences between the groups (P-value = 0.002). Apparently, the modulus of elasticity of group 2 and group 3 decreased significantly compared to that of the control group (group 1).
ConclusionsWe can conclude that nano-FHA can be incorporated into Essix plates in concentrations of up to 0.1 wt% in order to create some caries preventing effects with no negative effects on tensile strength; however, adding nano-FHA to Essix plate will decrease modulus of elasticity.
Keywords: Tensile Strength, Essix, Nano-flourohydroxy Apatite, Modulus of Elasticity -
زمینه و هدف
زنجیره های الاستومریک (چین ها) یکی از ابزارهای رایج برای جابجایی های دندانی در درمان های ارتودنسی به شمار می روند. هدف از انجام این مطالعه مقایسه رفتار الاستومریک و میزان اضمحلال نیرو در چین های با برندهای تجاری مختلف موجود در ایران در بازه های زمانی مختلف است.
روش بررسییازده چین الاستومریک مورد استفاده در این مطالعه از برند های: ClassOne، ASTAR، G&H، TSNPT، MIB (چینی)، MIB(فرانسوی(، ultra chainو دو برند American و Orthotechnology در دو نوع ساده و حافظه دار انتخاب شده بودند. چین ها به طولی که در آن، قادر به اعمال 150 گرم نیرو باشند کشیده شده و سپس میزان اضمحلال نیرو در هر یک از گروه ها در بازه های زمانی 1، 3 و 24 ساعت و 3، 7 و 21 روز و ضریب الاستیسیته در اولین مرحله و در روز 21 مورد ارزیابی قرار گرفت. داده های به دست آمده با استفاده از آنالیزهای آماری ANOVA و Tukey و Games-Howel مورد تحلیل قرار گرفتند.
یافته هاتمام چین ها تا روز 21 افت معنی دار ضریب الاستیسیته (به جز G&H، Class One، Ortho Technology ساده) و اضمحلال معنی دار نیرو را (به جز گروه (memory chain) American) نشان دادند. بالاترین میزان اضمحلال معنادار نیرو در بازه 21 روزه مربوط به گروه ASTAR خاکستری (05/0<p) و کمترین آن در ultra chain و MIB (فرانسوی) و American بود (05/0<p).
نتیجه گیریهمه چین ها اضمحلال نیروی معنی دار وابسته به زمان (بیشتر در روز اول) را نشان می دهند. فقط در برند (memory) American این میزان در هیچ یک از بازه های زمانی از نظر آماری معنی دار نبود. در میان بقیه چین ها پس از روز 21 بیشترین اضمحلال نیرو به برند Astar خاکستری و کمترین به ultra chain، MIB (فرانسوی) تعلق داشت.
کلید واژگان: چین الاستومریک، اضمحلال نیرو، ضریب الاستیسیتهBackground and AimsElastomeric chains are known as a current device with the purpose of dental movement in orthodontic treatments. The aim of this study was to compare the elastomeric behavior and force degradation rate between different elastomeric chains existing in Iran in different time durations.
Materials and Methods11 different elastomeric chains used in this study were: Class One, ASTAR, G&H, TSNPT, MIB (French and Chinese type), Ultra Chain and both American, Ortho Technology (simple and memory type). All chains were stretched upon to exert 150 g force and then force degradation rate in 6 time duration (1, 3, 24 hours and 3, 7, 21 days) and modulus of elasticity (MOE) in 2 time duration (start and 21 days) were investigated. All Data were analyzed statistically by ANOVA, Tukey, Games-Howel tests.
ResultsAll chains up to the 21th day showed a significant decrease in MOE except for the G&H, ClassOne, simple orthotechnology and a significant force degradation except for the American (memory type). The most significant force degradation rate was in ASTAR gray (P<0.05) and the least in MIB (French), Ultra Chain, and American (P<0.05).
ConclusionAll chains showed significant time-dependent force degradation (mostly in the first day). Only, this rate was not significant in any time duration for the American (memory). In all groups, the most force degradation rate belonged to ASTAR gray and the least to Ultra Chain, MIB (French) and American after 21th day.
Keywords: Elastomeric chain, Force degradation, Modulus of elasticity -
Journal of Dental Research, Dental Clinics, Dental Prospects, Volume:14 Issue: 1, Winter 2020, PP 12 -18Background
This study evaluated the phase transformation of NiTi orthodontic wires and forces they release on deactivation.
MethodsThe structural phase transformations of the following five thermo-activated nickel-titanium (NiTi) wires were evaluated using differential scanning calorimetry (DSC): Flexy Thermal Sentalloy® (GAC International), NiTi (35ºC) (Eurodonto), Thermo-Plus® (Morelli), FlexyNiTi® Flexy Thermal (35ºC) (Orthometric) and Damon® CuNiTi (35ºC) (ORMCO Corp.). The wires had a cross-section of 0.40 mm (0.016”). In addition, the forces they released were investigated using the three-point bending test. Five arches of each wire were tested using DSC (-20/80ºC at 10ºC/min), and six arches from each wire were sectioned for bending tests. The data were analyzed with ANOVA and post hoc Tukey tests. Pearson’s correlation test was performed between the results yielded by the DSC tests and those by three-point analyses (P=0.05).
ResultsThe DSC analysis showed differences between the NiTi alloys from all the manufacturers, with no differences between the lots of the same brand. ORMCO and Orthometric wires exhibited similar TTR values in cooling (P=0.49), and statistically similar TTR values in heating (P=0.056). The three-point bending test showed different patterns in releasing forces. A correlation was found between the DSC analysis and the three-point bending test results. Conclusion. The higher the temperature transformation was, the larger was the variation of force. All the wires presented higher forces at 3-mm deflection from 155 (±12.3) to 168.1 (±8) cN. The DSC analysis and the three-point bending test showed differences between the NiTi alloys from all the manufacturers.
Keywords: Calorimetry, differential scanning, modulus of elasticity, nickel, Orthodontics, orthodontic wires -
Journal of Dental Research, Dental Clinics, Dental Prospects, Volume:14 Issue: 1, Winter 2020, PP 41 -47Background
This in vitro study aimed to evaluate biofilm accumulation on and deactivation force of orthodontic nickeltitanium (NiTi) archwires before and after exposure to an oral medium.
MethodsFour commercial brands of orthodontic NiTi 0.016” archwires were examined before and after exposure to the oral medium for 4 weeks. Six archwire segments, 30 mm in length, from each manufacturer were tested in a device with four selfligating brackets, channel 0.022”, adapted to a universal test machine to evaluate the deactivation force between 0.5 and 3 mm of deflection. The presence of biofilm on the archwire surfaces was evaluated by scanning electron microscopy, before and after exposure to the oral medium. The Wilcoxon and kappa tests were applied to the biofilm scores, three-way ANOVA for repeated measures (Bonferroni post-test), and linear regression between biofilm and deactivation force.
ResultsThe exposure to the oral medium promoted moderate to severe presence of debris on the archwire surfaces and caused a reduction in deactivation force for the Ormco and GAC brands, while maintaining them with adequate force levels. The MORELLI and ORTHOMETRIC archwires underwent no significant reduction in deactivation force; moreover, these maintained elevated levels of force after exposure to the oral medium. The Spearman test indicated a low correlation between biofilm accumulation and deflection force for the Morelli (R2=0.132 and P=0.683) and Orthometric (R2=0.308 and P=0.330) brands. On the other hand, the GAC (R=0.767 and P=0.004) and ORMCO (R=0.725 and P=0.008) brands exhibited statistically significant correlation between these variables. Conclusion. Exposure to the oral medium for one month might give rise to significant changes in the dissipation of forces of orthodontic NiTi archwires, resulting from biofilm accumulation.
Keywords: Modulus of elasticity, nickel, orthodontics, orthodontic wires, surface properties -
IntroductionThe purpose of this study was to examine the microhardness and modulus of elasticity (MOE) of White ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK) after setting in moist or dry intracanal conditions.
Methods and Materials: To simulate root canal system, 14 polyethylen molds with internal diameter of 1 mm and height of 12 mm were used. These molds were filled with 9-mm thick layers of White ProRoot Mineral Trioxide Aggregate (MTA; Dentsply Tulsa Dental, Tulsa, OK). The experimental group (n=7) had a damp cotton pellet with 1.5 mm height and a 1.5 mm layer of resin composite placed on it. In control group (n=7) the whole 3 mm above MTA were filled with resin composite. The specimens were kept in 37°C and relative humidity of 80% for 4 days in order to simulate physiological conditions. Specimens were longitudinally sectioned and nanoindentation tests were carried out using Berkovich indenter at loading rate of 2 mN/s at 4×5 matrices of indents which were located in the coronal, middle and apical thirds of the specimens cross section, to evaluate the microhardness and modulus of elasticity of the specimen to appraise the progression of the setting process. Differences were assessed using nonparametric generalized Friedman rank sum and Wilcoxon Rank-Sum tests.ResultsStatistical analysis showed that there was a significant difference in microhardness and MOE between control and experimental groups at coronal (PConclusionWithin limitations of this in vitro study, it seems that moist intracanal environment improves setting of MTA in various depths.Keywords: Microhardness, Mineral Trioxide Aggregate, Modulus of Elasticity, Nanoindentation -
IntroductionResin composites are an important part of restorative treatment in modern dentistry. There are many trademarks available in Iran market and physico-chemical properties of many of these resin composites are not evaluated yet. This study was carried out to evaluate the physico-chemical properties of four available resin composites and also to assess the effect of aging on their properties. The findings of this study help clinicians to choose the best materials available.MethodsFour types of resin composites available in Iran market including Filtek Z350 XT, Filtek Z250, Herculite XRV Ultra and Herculite XRV were evaluated. Five samples were made of each composite using a metal mold (2* 10 * 10 mm). Two areas of each sample were light cured for 40 seconds. Samples were kept in saline for 24h and then underwent polishing process. Samples of each group were randomly allocated to five groups held in different conditions as follows: room temperature, distilled water in 37˚C, Distilled water plus hydrochloric acid, distilled water and thermocycling (5000 rounds of 5-55˚C), distilled water, thermocycling, and hydrochloric acid. At the end of one month, indentation was applied on each sample using nano-indentation technology (TriboIndenter, Hysitron, Minneapolis,MN).ResultsThe results of this study revealed that the type of composite and the environmental conditions affect elasticity and nano-hardness.Conclusionstorage conditions affected the elasticity of Filtek Z350XT, Herculite XRV Ultra and Herculite XRV and the hardness of Filtek Z350 XT and Herculite XRV Ultra.Keywords: resin composite aging, nanoindentation, nano, hardness, modulus of elasticity
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