Psychological stress can alter the environment in favor of corrosion of orthodontic alloys by changing the properties of saliva. This study aimed to assess the effect of stress induction on salivary nickel and chromium content in fixed orthodontic patients. Thirty patients were enrolled in this experiment. Saliva sample collection was performed at four time points: T1, before insertion of orthodontic appliances; T2, 3 months after the initiation of orthodontic treatment, before induction of stress; T3, 15 min following the induction of stress by Trier Social Stress Test; and T4, 30 min following the induction of stress. Ion content was measured by atomic absorption spectrophotometry. The obtained data were analyzed by repeated measures analysis of variance (ANOVA) and post hoc Bonferroni test. The mean amount of salivary nickel increased from 11.9 ± 5.1 μg/L at T1 to 14.1 ± 5.3 μg/L at T4. This increase was found significant only at T4 comparing to T1. The average salivary chromium content changed from 4.1 ± 2.3 μg/L at T1 to 5.1 ± 3.3 μg/L at T4. None of the differences were significant for chromium. In conclusion, induction of stress in this study led to a significant increase in nickel release from orthodontic appliances into saliva. The salivary chromium content however was not significantly altered, yet gradually increased.
Background:Rapid palatal expansion is one of the most important orthopedic treatments that correct the dental and palatal constriction. Stability of the changes partly depend on the rapidity of new bone formation in affected sutures after expansion. The purpose of this study was to investigate the effect of laser irradiation on the healing of midpalatal suture concurrent to the expansion of midpalatal suture in rats.Materials and Methods:A total of 78 male Sprague rats in seven groups were evaluated: A control group of six rats without any treatments and three experimental groups of 24 which underwent palatal expansion for different time periods (7, 14, and 30 days), and each divided into two groups of with and without laser irradiation. Laser therapy was done by gallium-aluminum-arsenide diode laser with 810 nm wavelength and 4 J/cm2 irradiation in days 0, 2, 4, 6, 8, 10, 12, 14 in 4 points (1 labial and 3 palatal points). After sacrificing, the sections were evaluated by histomorphometric and quantitative analysis and results were statistically investigated by independent samples t-test.Results:The results in 7 days, 14 days, and 30 days show that laser therapy can increase the rate of osteogenesis in palatal suture during rapid palatal expansion but the differences in 7 days groups were not significant (P = 0.117) while in 14 days groups (P = 0.032) and 30 days groups were significant (P = 0.001). Most of effectiveness of low-power laser was seen between 14 and 30 days while the laser therapy was stopped.Conclusion:These findings suggest that low-level laser irradiation can increase and accelerate bone regeneration in the midpalatal suture after rapid palatal expansion, hence, reduce retention time.
Although nickel and chromium are known as allergen and cytotoxic orthodontic metals, very few and controversial studies have assessed the effect of orthodontic treatment on their systemic levels reflected by their best biomarker of exposure, hair. This prospective preliminary study was conducted to evaluate hair nickel and chromium levels in fixed orthodontic patients. Scalp hair nickel/chromium concentrations of 12 female and 12 male fixed orthodontic patients were measured before treatment and 6 months later, using atomic absorption spectrophotometry. The effects of treatment, gender, and age on hair ions were analyzed statistically (α = 0.05). The patients' mean age was 18.38 ± 3.98 years. The mean nickel levels were 0.1380 ± 0.0570 and 0.6715 ± 0.1785 μg/g dry hair mass, respectively, in the baseline and sixth month of treatment. Chromium concentrations were 0.1455 ± 0.0769 and 0.1683 ± 0.0707 μg/g dry hair mass, respectively. After 6 months, nickel increased for 387 % (paired t test P = 0.0000) and chromium increased for 16 % (P = 0.0002). No significant correlations were observed between any ion levels with age or gender (Spearman P > 0.2). Within the limitations of this preliminary study, it seems that 6 months of fixed orthodontic treatment might increase levels of hair nickel and chromium. Future larger studies are necessary to validate these results.
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