Orthodontic appliances usually require the joining of different stainless-steel parts in order to achieve adequate control over tooth movement during the active treatment. The aim of this study was to assess the tensile and shear breaking force of the joints between forty orthodontic bands and forty attachments (buccal tubes), joined by laser and TIG welding, without filler material. For the laser welding technique, we used an XXS Laser (OROTIG) welding unit and for the TIG welding technique, a PUK D2 (LAMPERT) welding unit. The tensile and shear breaking force of the welded joints was determined using the Z010 Zwick/Roell testing machine. The independent-samples t-test showed statistically significant differences between the laser and TIG groups for both the tensile and the shear breaking force tests, the laser welded samples having better mechanical strength than the TIG welded samples. For practical use, under normal loading forces, both techniques are suitable for this particular application in orthodontics. In patients with parafunctional habits, that could develop higher bite forces, the failure of the welded joints might occur if the welding surface is not increased, especially for the TIG welding technique.
The results are presented of the key comparison EURAMET 1031 (EURAMET.M.D-K1.1) that covered the measurements of density and volume of silicon spheres of three different masses at 20 °C and 101325 Pa. The volume and density determinations of 15 national metrology institutes (NMIs) were checked and linked to the CCM.D-K1 key comparison. The measurements were carried out near 20 °C and at atmospheric pressure by the hydrostatic method in the time interval from 16 May 2008 to 18 Jan 2011.
The comparison was performed in two petals with three spheres in each petal. The travelling standards of petal 1 have a mass of 1001 g, 200 g and 35 g (Petal 2: 984 g, 239 g, 35 g). Whereas the reference values of the 1 kg travelling standards could be determined by the link to the CCM.D-K1 comparison, the density reference values for the smaller spheres were determined by density comparison to the 1 kg spheres using the pressure-of-flotation method.
One result was wrong due to a mistake in the mass determination. Additionally, four of the 57 volume (or density) values were discrepant with En values larger than 1.1, 1.2, 1.3 and 1.6.
Five NMIs achieved density uncertainties of about 1 ppm (1 × 10−6 in relative terms) or less for the 1 kg spheres. This satisfies the needs of all customers who wish to calibrate solid density standards for other laboratories.
Volume determinations of mass standards, air density artefacts or sorption artefacts should reach an uncertainty of about 1 mm3 in order to reduce the effect on the mass uncertainty to about 1 μg. At least for silicon spheres this is reached by eight NMIs. Due to the higher density of stainless steel this may be different for weights and will be checked within the CCM.D-K3 comparison.
The results of the comparison can be used to submit new or improved entries in the calibration measurement capabilities table in the BIPM key comparison database.
Main text
To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.
The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
In order to demonstrate the equivalence in calibration of mass standards among National Metrology Institutes (NMIs) of EURAMET this key comparison (KC) on 1 kg stainless steel mass standards has been carried out under the auspices of EURAMET. The comparison was undertaken with reference to the International Prototype Kilogram (IPK) as the definition of the unit of mass. The overall result shows good consistency among the participants.
Main text
To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.
The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
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