Evaluation of frictional resistance between monocrystalline (ICE) brakcets and Stainless Steel, Beta TMA and NiTiarch wires

Introduction: When using sliding mechanics for space closure during orthodontic treatment, friction occurs at the bracket-wire interface. The aim of this study was to evaluate the frictional resistance between monocrystalline (ICE) brackets and Stainless Steel, Beta TMA and NiTi wires. Methods: In this experimental study, we used 5 different types of orthodontic wires. Brackets and wires were divided in to 5 groups: 1-(monocrystalline+stainless steel 18) 2–(monocrystalline+stainless steel 19×25) 3-(monocrystalline+Beta-TMA) 4–(monocrystalline+Beta TMA 19×25) 5-(monocrystalline+NiTi 18). Instron Universal Testing Machine was used to investigate the static frictional resistance. The angulation between bracket and wire was 0 and the wires were pulled through the slots at a speed of 10 mm/min. Tests were performed 10 times for each group in artificial saliva. The average of 10 forces recorded was considered as static friction. One-way ANOVA and SPSS Version 18 and LSD post hoc test were used to evaluate the results of the study. Results: The mean static frictional force for each group was: group1: 0.82±0.14, group 2: 1.09±0.30, group 3: 0.87±0.53, group 4: 1.9±1.16, group 5: 1.42±0.30. There was a significant difference when comparing the two groups of similar wires in terms of shape (round or rectangular cross-section) as when comparing Beta TMA 18 and 19×25 arch wires with each other, the obtained p-value was 0.023, while the obtained p-value for the comparison of stainles steel arch wires was 0.034. Conclusions: The result of this study shows that Stainless Steel 18 wires generate the least amount of friction and round wires produce less friction than the rectangular wires. Beta TMA wires generate the highest amount of friction

Evaluation of frictional resistance between monocrystalline (ICE) brakcets and Stainless Steel, Beta TMA and NiTi arch wires

Introduction: When using sliding mechanics for space closure during orthodontic treatment, friction occurs at the bracket-wire interface. The aim of this study was to evaluate the frictional resistance between monocrystalline (ICE) brackets and Stainless Steel, Beta TMA and NiTi wires. Methods: In this experimental study, we used 5 different types of orthodontic wires. Brackets and wires were divided in to 5 groups: 1-(monocrystalline+stainless steel 18) 2–(monocrystalline+stainless steel 19×25) 3-(monocrystalline+Beta-TMA) 4–(monocrystalline+Beta TMA 19×25) 5-(monocrystalline+NiTi 18). Instron Universal Testing Machine was used to investigate the static frictional resistance. The angulation between bracket and wire was 0 and the wires were pulled through the slots at a speed of 10 mm/min. Tests were performed 10 times for each group in artificial saliva. The average of 10 forces recorded was considered as static friction. One-way ANOVA and SPSS Version 18 and LSD post hoc test were used to evaluate the results of the study. Results: The mean static frictional force for each group was: group1: 0.82±0.14, group 2: 1.09±0.30, group 3: 0.87±0.53, group 4: 1.9±1.16, group 5: 1.42±0.30. There was a significant difference when comparing the two groups of similar wires in terms of shape (round or rectangular cross-section) as when comparing Beta TMA 18 and 19×25 arch wires with each other, the obtained p-value was 0.023, while the obtained p-value for the comparison of stainles steel arch wires was 0.034. Conclusions: The result of this study shows that Stainless Steel 18 wires generate the least amount of friction and round wires produce less friction than the rectangular wires. Beta TMA wires generate the highest amount of friction

Ethological Factors of Chronic Back Pain in MRI of a Group of Military Personnel

Background and Aim: Chronic low back pain is one of the most common debilitating occupational diseases. It seems that the frequency of this type of back pain is increasing, especially among young military staff. The aim of this study was to evaluate the causes of chronic low back pain according to interpretation of MRI reports in military personnel of army land forces of the Islamic Republic of Iran. Materials and Methods: In this descriptive cross-sectional study, the data of military personnel with chronic low back pain, referring to the Neurosurgery Council of Khanevadeh Hospital, Tehran in 2016 were extracted. The information included demographic and occupational characteristics of the patients, clinical findings, and MRI reports. We used chi-square and Fischer exact tests for data analysis at the significance level of 95%. Results: 326 male military personnel with chronic low back pain were evaluated. The mean age of the subjects was 37.3 ± 0.6 years. The most common MRI finding was disc herniation which was detected in 174 cases (53.3%). low back pain was most frequent in the combat branch, which included 114 cases (34.9%). There was no statistically significant correlation between MRI findings and types of military branches (P=0.071). The highest frequency of disc herniation belonged to the patients between 20 and 29 years of age (p=0.002) and the highest frequency of degenerative changes was seen in the patients over 50 years of age (p=0.005). Conclusion: The most important finding of this study was the low mean age of the patients with chronic low back pain who were in their active working years. We suggest revision of the trend of periodic examinations of military personnel, ergonomics of the work environment and military training