Lubricating conditions: effects on friction between orthodontic brackets and archwires with different cross-sections.

OBJECTIVE: This study investigated the effect of the condition of lubrication on the friction between brackets and NiTi archwires of different rounded cross-sections. METHODS: Brackets (Roth, GAC) were affixed to a device connected to a universal testing machine into which segments of archwire were placed (NiTi, Nitinol, GAC) with cross-sections of 0.012-in, 0.016-in and 0.020-in. Once the wire was in the bracket slot, the following lubricants were applied: human saliva (HS: positive control), distilled water (DI), mucin-based (MUC) or carboxymethylcellulose-based (CMC) artificial saliva. In the negative control group, no lubricant was used. The combination between the wire cross-sections and the lubrication condition generated 15 groups with 15 samples each. Data were submitted to two-way analysis of variance and Tukey's test. RESULTS: There was no significant interaction between the wire cross-section and the condition of lubrication (p= 0.901). Irrespective of whether lubricants were used or not, there was a significant increase in friction with an increase in the cross-section of the wire (p< 0.001). For any wire, the group tested in the presence of MUC was not different from that in which HS was applied. On the other hand, when the application of lubricants was suppressed, significantly higher friction values were observed. The CMC group and the DI group demonstrated intermediate behavior. CONCLUSIONS: Friction increased with the increase of the cross-section of the NiTi archwire, but regardless of the archwire, friction with MUC artificial saliva was similar to that of HS and lower than in dry conditions.

Análise comparativa da relação carga/deflexão entre fios de níquel-titânio convencionais e estéticos / Comparative study of load/deflection property between regular nickel-titanium wires and aesthetic wires

O objetivo deste estudo foi avaliar, comparativamente, a relação carga/deflexão dos fios ortodônticos de níquel-titânio superelásticos metálicos e estéticos, das marcas Orthometric® e GAC-Dentsply®. Foram avaliados fios ortodônticos 0,016” de níquel-titânio em arcos pré-contornados, com e sem revestimento. As amostras totalizaram 20 segmentos de fios de 28 mm, divididos em 4 grupos: Grupo 1 - Orthometric – Marília/SP/Brasil – estético, Grupo 2 - Orthometric - metálico superelásticos, Grupo 3 - GAC / Dentsply – New York/NY/USA – estético e Grupo 4 - GAC – Dentsply - metálico superelástico. Foi utilizado como corpo de prova um dispositivo em acrílico com bráquetes metálicos Edgewise slot .022” (Dental Morelli Ltda., Sorocaba/SP/Brasil). O teste de deflexão foi realizado na máquina de ensaio universal Kratos a uma velocidade de 0,5 mm/min, com célula de carga de cinco Newtons, utilizando-se uma ponta com extremidade cônica de 8 mm de diâmetro. A análise da relação carga/deflexão foi mensurada a cada 0,5 mm, entre 0 e 3 mm de deflexão do fio. Os resultados deste estudo demonstraram que não houve diferença estatisticamente significante entre os grupos de acordo com o Teste ANOVA, para a ativação (p= 0,774) e desativação (p=0,367), considerando a = 0,05. Concluí-se que todos os grupos possuem valores da proporção carga/deflexão semelhantes.

The aim of this study was to perform a comparative analysis of the load-deflection relation between coated (aesthetic) and uncoated nickel-titanium orthodontic wires from two different brands: Orthometric® (Marília/SP/Brazil) and GAC-Dentsply® (NewYork/NY/USA). An assessment of nickel-titanium orthodontic wires of 0.016” on pre-countered arches was performed. The sample was composed of 20 segments of 0.016” nickel-titanium orthodontic arches divided into 4 groups: Group 1 - Orthometric® – aesthetic; Group 2 - Orthometric® -superelastic alloy, Group 3 - GAC/ Dentsply – aesthetic; Group 4 - GAC – Dentsply - superelastic alloy. An acrylic device with metal brackets was used as specimen. The deflection test was carried out in a Kratos universal testing machine, at a 0.5 mm/min speed with a 5 Newtons load cell using a 8mm tapered tip. The analysis of the load/deflection relation was measured every 0.5 mm between 0 and 3 mm of wire deflection. The results of this study showed no statistically significant difference between groups according to ANOVA test for the activation (p = 0.774) and deactivation (p = 0.367), considering a = 0.05. It was concluded that all groups have similar values for load/deflection ratio

Transforming growth factor ß and apoptosis in leprosy skin lesions: possible relationship with the control of the tissue immune response in the Mycobacterium leprae infection.

The course of leprosy depends of the host immune response which ranges from the lepromatous pole (LL) to the tuberculoid pole (TT). A comparative study was conducted in 60 patients with the LL and TT. The results showed a mean expression of TGF-ß of 339 ± 99.4 cells/field for TT and of 519.2 ± 68.2 cells/field for LL. Frequency of apoptosis was 6.3 ± 1.8 in TT and 14.0 ± 6.1 in LL. A correlation (p = 0.0251) between TGF-ß and caspase-3 in the LL was found. This finding indicates a role of TGF-ß and apoptosis in the immune response in leprosy.