The aim of this paper is to analyze the influence of the nature of the orthodontic archwires on the friction coefficient and wear rate against materials used commonly as brackets (Ti-6Al-4V and 316L Stainless Steel). The materials selected as orthodontic archwires were ASI304 stainless steel, NiTi, Ti, TiMo and NiTiCu. The array archwire's materials selected presented very similar roughness but different hardness. Materials were chosen from lower and higher hardness degrees than that of the brackets. Wear tests were carried out at in artificial saliva at 37 °C. Results show a linear relationship between the hardness of the materials and the friction coefficients. The material that showed lower wear rate was the ASI304 stainless steel. To prevent wear, the wire and the brackets have high hardness values and in the same order of magnitude.

The anatomy of dental compensation curve in the frontal plane described by George H. Wilson is one of the occlusal determinants of orthodontic treatment. However, there is few published comparing malocclusion and normocclusion individuals. Objectives: The aim of this study is to compare the curve of Wilson at first and second maxillary molars, normocclusion pattern and malocclusion pattern, with and without bilateral posterior crossbite, using angular references in CBCT studies. Material and Methods: We analyzed 10 cases of malocclusion with bilateral posterior crossbite, 10 cases of malocclusion without bilateral posterior crossbite and 10 cases with non orthodontic normocclusion (patients who underwent cone beam study for other reasons than orthodontic). All of them were adults, more than 19 years. Angular variables from left and right axis (line connecting the occlusal and furcation groove) of first and second molars towards a perpendicular to the frontal palate were measured. There was carried out an Anova test, Bonferroni analysis and Levene´s statistics. Results: The descriptive analysis of the results shows an average values of total maxillary curve of Wilson for first molars (sum of left and right angle) of 8.1° for normocclusion group, 0.4° for the malocclusion pattern with bilateral posterior crossbite and 16.9° for the malocclusion pattern without this alteration. The mean differences was statistical significant (P<0,042) between between malocclusion pattern groups with and without crossbite . Conclusion: The curve of Wilson, measured at maxillary first molars in patients with bilateral posterior crossbite is more concave than the other groups, suggesting no dentoalveolar compensations. Key words:Wilson curve, CBCT, buccal posterior occlusion, posterior crossbite.

Thermo-chemical treatment is an excellent compromise between the improvement of bioactive and mechanical long-life behaviors.

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This work studies NiTi orthodontic archwires that have been treated using a new oxidation treatment for obtaining Ni-free surfaces. The titanium oxide on the surface significantly improves corrosion resistance and decreases nickel ion release, while barely affecting transformation temperatures. This oxidation treatment avoids the allergic reactions or toxicity in the surrounding tissues produced by the chemical degradation of the NiTi. In the other hand, the lack of low friction coefficient for the NiTi superelastic archwires makes difficult the optimal use of these materials in Orthodontic applications. In this study, the decrease of this friction coefficient has been achieved by means of oxidation treatment. Transformation temperatures, friction coefficient and ion release have been determined.