Reza Jelodar; Farhad Shafiei; Angela Yalda Rezaei
Abstract
Background: In the oral environment orthodontic wires will be subjected to thermal fluctuations and repeated loading (fatigue).
Objectives: The aim of this study is to evaluate the thermocycling and fatigue effect on the CuNiti wires. Materials and Methods: Samples of CuNiti wires, 0.014 round, were ...
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Background: In the oral environment orthodontic wires will be subjected to thermal fluctuations and repeated loading (fatigue).
Objectives: The aim of this study is to evaluate the thermocycling and fatigue effect on the CuNiti wires. Materials and Methods: Samples of CuNiti wires, 0.014 round, were divided into four groups: 1, Fatigue loading; 2, Fatigue and thermocycling; 3, thermocycling; 4, control. The groups involved in fatigue loading by determined protocol (0.5 mm deflection, 1Hz frequency) also thermocycling performed by this method: bath time (90 seconds), transfer time (15 seconds) and temperature range: 5 - 55C.after these procedure, fatigue and thermocycling effects on the maximum loading force (MLF) and maximum unloading force (MULF) assessed with a 3-point bending test. Results: In this study, the amounts of MLF in group 1 and 2 were significantly different with themselves and control group, but in the control group, the results were not significantly different with thermocycling group. Also the amounts of MLF in the group 3 were not different by the group 1 and 2. For the MULF, the results of group 1 and 2 were significantly different with the control and thermocycling group. Difference between fatigue and control groups for hysteresis loading (difference between MLF and MULF) variable was not significant while other two by two comparisons were significant.
Conclusions: The fatigue loading increased MLF and MULF, but the effect of thermocycling was complicated on the MLF. Thermocycling also did not affect the MULF, but decreased hysteresis loading.
Mojgan Kachoei; Faranak Eskandarinejad; Mahsa Eskandarinejad
Abstract
Aim: Friction accompanies all sliding techniques. Sliding is in the manner of tipping and uprighting with increasing angle between bracket and wire. Recently, wire coating with the different nanoparticles has been proposed to decrease the frictional forces. The present study was done to coat the stainless ...
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Aim: Friction accompanies all sliding techniques. Sliding is in the manner of tipping and uprighting with increasing angle between bracket and wire. Recently, wire coating with the different nanoparticles has been proposed to decrease the frictional forces. The present study was done to coat the stainless steel wires with the ZnO nanoparticles and determine the effect of this coating on friction reduction during different angle between the wires and brackets.
Materials and Methods: Eighty pieces of 0.016 stainless steel wires with and without zinc oxide nanoparticles were used in 80 pieces of orthodontic brackets (0.018). The coated wires analyzed by the SEM and XRD observations. Friction between the wires and orthodontic brackets at 0,5,10 degree angle were calculated using universal testing machine. Two and three group comparisons were done by means of Student t and one-way ANOVA respectively and Tukey post hoc test was used to assess the paired comparisons. Results: Frictional values were significantly increased with the increased angles between the wire and bracket. The increased friction force from 0 to 10 degree in uncoated wires were Statistically more significant than increased friction force from 0 to 10 degree in coated wires (p<0.005).Conclusion: considering the positive effects of zinc oxide nanoparticles coating in decreasing frictional forces, they might offer a novel opportunity to significantly reduce friction during sliding and consequent better anchorage control, reduced risk of root resorption.
Mojgan Kachoei; Ahmad Behroozian
Abstract
Aim: Sliding a tooth along an archwire involves a frictional force, causing a number of adverse effects like anchorage loss, excessive orthodontic forces, prolonged treatment time and damage to the roots. This is especially true in ceramic brackets where the friction is notoriously higher.Recently, wire ...
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Aim: Sliding a tooth along an archwire involves a frictional force, causing a number of adverse effects like anchorage loss, excessive orthodontic forces, prolonged treatment time and damage to the roots. This is especially true in ceramic brackets where the friction is notoriously higher.Recently, wire coating with the different nanoparticles has been proposed to decrease the frictional forces. This study evaluated the friction force created between stainless steel
archwires coated with ZnO nanoparticles and ceramic brackets in vitro.Materials and Methods: Friction tests simulating archwire functioning of the coated and uncoated wires and ceramic brackets were carried out by an Instron machine.Control and case groups included uncoated and coated 0.019×0.025 stainless steel wires respectively. Coating was preformed by inserting stainless steel (SS) wires into solutions of ethanol + zinc oxide. The adhesion properties of the coated wires after friction were analyzed by SEM (scanning electron microscope).The frictional forces were compared usingMann-Whitney test.Results: In the control group (porcelain brackets + uncoated stainless steel wires) the mean friction force was 2.59 ± 0.37N whereas in case group (porcelain brackets + coated stainless steel wires) the mean friction force was 2.54 ±0.32 N. Although the friction force in coated wires was lower than uncoated wires; the difference between two groups was not statistically significant. (p=0.62). Conclusion: coating of stainless steel archwires with ZnO nanoparticles did notcause significant reduction in frictional forces between stainless steel arch wires and ceramic brackets.
