Effect of stress relaxation in two different preactivation methods of beta-titanium T-loops: bends vs. continuous curvature

Autor(es)

Fernandes Rabelo Caldas, Sergei Godeiro ^[1] ; Martins, Renato Parsekian ^[2] ; de Araujo, Marcela Emilio ^[1] ; Galvao, Marilia Regalado ^[1] ; dos Santos Nunes Reis, Jose Mauricio ^[3] ; Martins, Lidia Parsekian ^[4]

Afiliação do(s) autor(es)

^[1] UFRN Fed Univ Rio Grande Norte, Dept Dent, Natal, RN - Brazil

^[2] UNESP Univ Estadual Paulista, Araraquara Sch Dent, Orthodont Grad Program, Araraquara, SP - Brazil

^[3] UNESP Univ Estadual Paulista, Araraquara Sch Dent, Dept Dent Mat & Prosthesis, Araraquara, SP - Brazil

^[4] UNESP Univ Estadual Paulista, Araraquara Sch Dent, Dept Pediat Dent, Araraquara, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF THE WORLD FEDERATION OF ORTHODONTISTS; v. 6, n. 3, p. 98-104, SEP 2017.
• Citações Web of Science: 0

Resumo

Objective: Assess the changes in the force system of T-loop springs (TLSs) preactivated by bends and curvature, when secured in place with a constant strain over time. Materials and Methods: A total of 120 TLSs with dimensions 6 x 10 mm, produced out of 0.017 x 0.025-inch TMA, were randomly divided into two groups of 60 TLSs, each according to what preactivation was going to be used, concentrated bends or gradual curvature. Subgroup 1 was tested immediately and the remaining subgroups were tested after they were secured at 5-mm activation for different periods of time in an interbracket distance of 23mm. Subgroups 2, 3, 4, 5, and 6 were kept activated for 24, 48, and 72 hours, 1 and 2 weeks, respectively. Using a moment transducer coupled to a digital extensometer indicator adapted to a universal testing machine, the amount of horizontal force, moment, and moment-to-force (MF) ratios were recorded. Results: Both groups showed a decrease in force levels over time (P < 0.001 and 0.005 for bend and curvature preactivation, respectively), but with different behaviors. The group preactivated by bends showed a reduction in moments over time (P < 0.001), whereas the group preactivated by curvature did not (P = 0.410). The MF ratio has not changed over time in either group. Conclusions: The stress-relaxation effect is more evident on group preactivated by bends. (C) 2017 World Federation of Orthodontists. (AU)

• Processo FAPESP: 08/07258-5 - Avaliação da estabilidade das pré-ativações das molas "T" do Grupo B confeccionadas com fios de titânio-molibdênio ao longo de três meses
• Beneficiário: Lídia Parsekian Martins
• Modalidade de apoio: Auxílio à Pesquisa - Regular