Orthodontics
Behnaz Karimzadeh; Tannaz Abdollahzadeh; Ali Eidi; Mojgan Kachoei
Abstract
Objective: The aim of this study was to determine Bolton ratios in the Iranian orthodontically treated population of different malocclusions and compare these values among malocclusion groups and with Bolton reference values.Methods: Bolton ratios of 210 subjects were investigated in three groups of ...
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Objective: The aim of this study was to determine Bolton ratios in the Iranian orthodontically treated population of different malocclusions and compare these values among malocclusion groups and with Bolton reference values.Methods: Bolton ratios of 210 subjects were investigated in three groups of Class I, II, and III skeletal patterns. The measurement of mesiodistal width of teeth was made on post-treatment dental models using a digital caliper. One-way analysis of variance and one-sample t-test were used to compare obtained anterior values and overall ratios among studied groups and with reference values, respectively. P-value<0.05 was considered as significant.Results: The mean values of anterior ratio in total subjects were 76.77, and in the Class I skeletal pattern group was 76.51, which were significantly different from the reference value (p-value < 0.05). However, the differences in the mean anterior ratios of Class II and III groups and the mean overall ratios of three studied groups with reference values were not statistically significant. Furthermore, there was no significant difference between the anterior and overall Bolton ratios of the three studied groups (p-value>0.05).Conclusion: Since the obtained Bolton ratios in Class II and III groups were not significantly different from reference values, these values are also applicable for mild skeletal malocclusions. However, the difference in mean anterior ratios of the total 210 subjects and Class I group with Bolton reference values could be caused by racial differences or several factors related to orthodontic treatment, which can be investigated in subsequent studies.
Seyed Hosein Moslemzade; Mojgan Kachoei; Aydin Sohrabi; Ali Rafighi; S. Bahmani
Abstract
Background and aim: The frequency of exposure of dental personnel to infection and of patient to cross contaminated instruments has prompted concern about adequate sterilization of dental instruments. Aim of the present study was to evaluate the changes in the frictional properties of Ni-Ti orthodontic ...
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Background and aim: The frequency of exposure of dental personnel to infection and of patient to cross contaminated instruments has prompted concern about adequate sterilization of dental instruments. Aim of the present study was to evaluate the changes in the frictional properties of Ni-Ti orthodontic wires after sterilization with chemical agents.
Materials and methods: In the present study the friction between Ni-Ti wires measuring 16 mm in diameter and 18-slot stainless steel brackets were measured and compared in two groups as follows: 1) without sterilization (as received); 2) after chemical sterilization. Each group consisted of 30 specimens and friction was measured in a Universal testing machine.Results: Comparison of unsterilized samples with the group sterilized with chemical agents showed a significant difference (P=0.000) in shear stress.Conclusion: Based on the results of the present study, this sterilization techniques result in an increase in the friction of Ni-Ti orthodontic wires.
Mojgan Kachoei; Mohammad Hossein Ahangar Atashi; Amir Mohammadi; Sina BadamchiZadeh; Mehri Khobivand; Mahdieh Nourzadeh
Abstract
Introduction: Third molar impaction is usually related to lack of space for eruption. The aim of this study was to assess third molar angulation following extraction and non extraction orthodontic treatment.Methods: This study was carried out on pretreatment and post treatment panoramic and cephalometricradiographs ...
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Introduction: Third molar impaction is usually related to lack of space for eruption. The aim of this study was to assess third molar angulation following extraction and non extraction orthodontic treatment.Methods: This study was carried out on pretreatment and post treatment panoramic and cephalometricradiographs of 70 CL I malocclusion patients. Thirty-five patients (24 female and 11 male) with mean age of 16.3±1.8 years had been treated with extraction of four first premolars (extraction group) and thirty-five patients (27 female and 8 male) with mean age of 16.9±2.6 years had been treated without extraction (nonextraction group). In each group, upper and lower third molar angulation, on pre and post treatment radiographs were assessed. Changes in third molar angulations from pretreatment to post treatment in each group were assessed with Mann- Whiteny U test. Changes in two groups were compared with Wilcoxon test.Results: statistical analysis revealed some degree of improvement in third molar angulation in both groups. changes of upper left third molars in extraction group and upper right and lower left third molars in non extraction group were statistically significant. The changes of third molar angulation between two groups were not statistically significant.
Conclusion: Extraction of first premolars during orthodontic treatments does not influence unerupted third molar angulation.
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.
