Introduction:Various components of fixed orthodontic appliances are continuously interacting with saliva and other fluids in the mouth releasing various metal ions including nickel and chromium that can cause damaging effects if their concentration exceeds above the toxic dose.Aim:To determine and compare the level of nickel and chromium in the saliva of patients undergoing fixed orthodontic treatment at different time periods.Materials and Methods:The sample of saliva of 13 patients was taken at different time periods that is: Group 1 (before appliance placement), Group II, III, and IV (after 1-week, 1-month, and 3 months of appliance placement respectively). The fixed appliance comprised of brackets, bands, buccal tubes, lingual sheath, transpalatal arch and wires composed of Ni-Ti and stainless steel. The level of ions was determined using graphite furnace atomic absorption spectro-photometry. The data thus obtained were statistically analyzed using SPSS Statistical Analysis Software (Version 15.0).Results:Level of nickel and chromium in saliva was highest in Group II and lowest in Groups I for both the ions. On comparison among different Groups, it was statistically significant for all the groups (<0.001) except between Group III and Group IV.Conclusion:The release of nickel and chromium was maximum at 1-week and then the level gradually declined. These values were well below the toxic dose of these ions. The results should be viewed with caution in subjects with Ni hypersensitivity.

a b s t r a c tObjective: The aim of this study was to evaluate and compare the cephalometric measurements obtained from computerized tracing of direct digital radiographs and hand tracing of their digital radiographic printouts. Material and methods: The soft-and hard-copies of pre-treatment lateral cephalograms of 40 subjects (both males and females) within the age group of 10e30 years, irrespective of the type of malocclusion were taken. Total 26 measurements (13 linear and 13 angular) were obtained using both the manual and the digital technique. for angular measurements). While amongst the angular measurements, only occlusal plane angle showed statistically significant difference between the two techniques that was not clinically acceptable.

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BackgroundRetraction in lingual orthodontics has biomechanical differences when compared to labial orthodontics, which is not yet established. Thus, we have intended to compare the biomechanical characteristics of closed helical loop and T-loop on 1 mm activation with 30° of compensatory curvatures during retraction in lingual orthodontics.MethodsSTb lingual brackets were indirectly bonded to maxillary typhodont model that was scanned to obtain FEM model. Closed helical loop (2 × 7 mm) and T-loop (6 × 2 × 7 mm) of 0.016″ × 0.016″ TMA wire were modeled without preactivation bends. Preactivation bends at 30° were given in the software. Boundary conditions were set. The force (F) and moment (M) of both the loops were determined on 1 mm activation, using ANSYS software. M/F ratio was also calculated for both the loops.ResultsT-loop exerted less force, thus increased M/F ratio as compared to closed helical loop on 1 mm activation.ConclusionsWhen torque has to be preserved in the anterior segment during retraction in lingual orthodontics, T-loop can be preferred over closed helical loop.

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