Metallographic structure and hardness of titanium orthodontic brackets.

Biomaterials Laboratory, Section of Basic Sciences and Oral Biology, School of Dentistry, University of Athens, Athens, Greece.
Journal of Orofacial Orthopedics / Fortschritte der Kieferorthop├Ądie (Impact Factor: 0.69). 12/2003; 64(6):426-33. DOI: 10.1007/s00056-003-0308-5
Source: PubMed

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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