Metallographic structure and hardness of titanium orthodontic brackets.
ABSTRACT To determine the elemental composition, microstructure, and hardness of two different brands of titanium (Ti) orthodontic brackets.
Four specimens of each brand were embedded in epoxy resin and, after metallographic grinding and polishing, were studied under a metallographic microscope. The bonding base morphology of each bracket was studied in as-received brackets by scanning electron microscopy. Energy dispersive x-ray microanalysis (EDS) was used on polished specimens to assess the elemental composition of base and wing bracket components, and the brackets were subjected to metallographic etching to reveal the metallurgical structure. The same specimen surfaces were used for assessment of the Vickers hardness. The results were statistically analyzed by two-way analysis of variance (ANOVA) with the bracket brand and bracket region (base, wing) serving as discriminating variables, whilst further group differences were investigated with Tukey's multiple comparison test at the alpha = 0.05 level of significance.
Metallographic imaging revealed that the Orthos2 brackets (Ormco, Glendora, CA, USA) consist of two parts joined together by laser welding, with large gaps along the base wing interface, whereas Rematitan brackets (Dentaurum, Ispringen, Germany) are single-piece appliances. Ti was the only element identified in Rematitan and Orthos2 base materials, while aluminium (Al) and vanadium (V) were also found in the Orthos2 wing component. Metallographic analysis showed the presence of a + b phase for Orthos2 and plate-like grains for Rematitan. The results of the Vickers hardness testing were: Orthos2 (wing): 371 +/- 22, Rematitan (wing): 272 +/- 4, Rematitan (base): 271 +/- 16, Orthos2 (base): 165 +/- 2.
The findings of the present study suggest that there are significant differences in composition, microstructure and hardness between the two commercial types of Ti brackets tested; the clinical implications of the findings are discussed.
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ABSTRACT: With the increased awareness of Ni allergies, alternative alloys for orthodontic products must be identified. The properties of these new products must be determined. Rectangular (0.017 x 0.025 in) stainless steel (SS) and beta-titanium (beta-Ti) archwires were tested against commercially pure titanium brackets (CP-Ti, 0.018-in slot) in the dry state and with whole human saliva. Resistance to sliding (RS) was measured as a function of 5 normal forces (N, 200 to 950 cN), 32 angles (theta, -12 degrees to +12 degrees), and 1 interbracket distance (IBD, 18 mm). With clearance between the archwire and the bracket (passive region, theta < or =theta(c)), the frictional coefficients (mu) of the SS archwire and the CP-Ti bracket couples were 0.12 and 0.13 for the dry and wet tests, respectively; for the beta-Ti archwire and the CP-Ti bracket couples, the mu values were 0.29 and 0.28 for the dry and wet tests, respectively. For an theta without clearance (active region, theta > or =theta(c)), RS increased as a function of theta and N. To examine the rates of binding (mu(BI)) in this active region, the value of classical friction (mean of the passive region data) was subtracted from RS to yield BI, and the value of theta(c) was subtracted from each theta to yield relative contact angles (theta(r)). Because of the unique relationship between the frictional and mechanical properties of these SS and beta-Ti archwires tested against the CP-Ti brackets at a large IBD, the mu(BI) values for these archwire-bracket couples were nominally equivalent (24 to 30 cN per degree). Clinical outcomes would be unaffected by this 6 cN per degree (approximately 0.2 oz-force per degree) difference. When all kinetic data in the elastic region (theta(r) < or =5 degrees ) were combined, mu(BI) equaled 28 cN per degree. Above this region (theta(r) > or =5 degrees ), the data for the SS archwire and CP-Ti bracket couples were less scattered than those for the beta-Ti archwire and the CP-Ti bracket couples. This demarcation from linearity was designated as theta(z) and indicated the end of the elastic region and the beginning of the plastic region, above which sliding can eventually cease. This region (theta > or =theta(z)), the binding region (theta(c) < or =theta < or =theta(z)), and the classical friction region (theta < or =theta(c)) were described in a model. This model explains, in part, the equivalent values of mu(BI) for SS and beta-Ti archwires tested against CP-Ti brackets.American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 03/2007; 131(3):400-11. · 1.33 Impact Factor
Conference Paper: Intemet QoS over passive optical networksAdvanced Communication Technology, 2004. The 6th International Conference on; 02/2004
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ABSTRACT: Fluoride ions, in long-term applications on titanium brackets, cause their corrosion. Fluoride gel used for caries prevention during orthodontic treatment has a very high concentration in fluoride ions, and therefore has the potential for causing bracket corrosion. The main aim of this study was to determine the effect of eliminating the residual fluoride gel, by rinsing it, on the corrosion of titanium brackets. The secondary aim was to evaluate the corrosion of titanium brackets in the presence of fluoride gel. One hundred titanium brackets were divided into five groups of 20 brackets each. Group 1 being the control group, the rest of the groups were immersed in fluoride gel: Group 2 for 4 minutes and kept for 30 minutes with the residual fluoride gel on; Group 3 for 4 minutes followed by immediate water rinsing; Group 4 for 12 minutes and kept for 90 minutes with the residual fluoride gel on and Group 5 for 12 minutes followed by immediate water rinsing. All groups were rinsed then dried, for 20 hours, using Silica gel in a desiccator maintained at 37°C before testing. Gravimetrical results and SEM analysis showed no significant difference between Groups 2, 3 and 5 compared to each other and to the control group. Only Group 4 showed significant weight loss and pitting corrosion in four of the 20 brackets. In sliding resistance, no significant difference was detected between any of the groups. Short time applications of fluoride gel do not affect sliding resistance of titanium brackets. No titanium corrosion was detected for one application of concentrated fluoride gel and some brackets showed pitting corrosion for three applications. The rinsing of residual fluoride gel eliminates completely the risk of bracket corrosion.International Orthodontics 09/2011; 9(3):298-315.