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Objective: To evaluate the effects of different concentrations of chlorhexidine on the decline in force of orthodontic elastics. Materials and Methods: In a laboratory study, five groups of samples were tested, with one control group represented by distilled water (group 1) and four experimental groups: 0.12% manipulated chlorhexidine (group 2), 0.2% manipulated chlorhexidine (group 3), 0.12% chlorhexidine gluconate-based oral solution (0.12% Periogard; group 4), and 0.2% Cleanform mouthwash (formula and action; group 5). The test groups were submersed in artificial saliva at 37uC. Templates were used and submerged in the chlorhexidine solutions for 30 seconds twice a day. Force was measured with a digital dynamometer at six different time intervals: 0, 1, 7, 14, 21, and 28 days. Results: No statistical differences were found among the groups in the initial period, at 24 hours, and at 7 days (P . .05). There were statistical differences between groups 2 and 5 at 14 days of the experiment and between group 1 and the others at 28 days. In the initial period, the force was statistically higher than it was at any of the other periods of the experiment (P , .05). Conclusion: In the present study, chlorhexidine showed no significant influence on the force degradation of the chain elastics tested. (Angle Orthod. 2013;83:313-318.)

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Objective: To test the hypothesis that treatment time, debris/biofilm, and oral pH have an influence on the physical-chemical properties of orthodontic brackets and arch wires. Materials and Methods: One hundred twenty metal brackets were evaluated. They were divided into four groups (n 5 30) according to treatment time: group C (control) and groups T12, T24, and T36 (brackets recovered after 12, 24, and 36 months of treatment, respectively). Rectangular stainless-steel arch wires that remained in the oral cavity for 12 to 24 months were also analyzed. Dimensional stability, surface morphology, composition of brackets, resistance to sliding of the bracket-wire set, surface roughness of wires, and oral pH were analyzed. One-way analysis of variance, followed by a Tukey multiple comparisons test, was used for statistical analysis (P , .05).Results: Carbon and oxygen were shown to be elements that increased expressively and in direct proportion to time, and there was a progressive increase in the coefficient of friction and roughness of wires as a function of time of clinical use after 36 months. Oral pH showed a significant difference between group T36 and its control (P 5 .014). Conclusions: The hypothesis was partially accepted: treatment time and biofilm and debris accumulation in bracket slots were shown to have more influence on the degradation process and frictional force of these devices than did oral pH. (Angle Orthod. 2015;85:298-304.)