Maria Cristina Figueiredo Pollmann

Effect of activation and preactivation on the mechanical behavior and neutral position of stainless steel and beta-titanium T-loops

Objective To quantify, for each activation, the effect of preactivations of differing distribution and intensity on the neutral position of T-loops (7-mm height), specifically the horizontal force, moment to force (M/F) ratio, and load to deflection ratio. Methods A total 100 loops measuring 0.017 × 0.025 inches in cross-section were divided into two groups (n = 50 each) according to composition, either stainless steel or beta-titanium. The two groups were further divided into five subgroups, 10 loops each, corresponding to the five preactivations tested: preactivations with occlusal distribution (0°, 20°, and 40°), gingival distribution (20°), and occlusal-gingival distribution (40°). The loops were subjected to a total activation of 6-mm with 0.5-mm iterations. Statistical analysis was performed using comprised ANOVA and Bonferoni multiple comparison tests, with a significance level of 5%. Results The location and intensity of preactivation influenced the force intensity. For the M/F ratio, the highest value achieved without preactivation was lower than the height of the loop. Without preactivation, the M/F ratio increased with activation, while the opposite effect was observed with preactivation. The increase in the M/F ratio was greater when the preactivation distribution was partially or fully gingival. Conclusions Depending on the preactivation distribution, displacement of uprights is higher or lower than the activation, which is a factor to consider in clinical practice.

Correcção de uma Má-Oclusão de Classe Ii Divisão 1 em Duas Fases de Tratamento☆

The influence of functional appliances on craniofacial growth as well as the two-phase orthodontic treat- ment philosophy are still controversial subjects. The main purpose of the two-phase treatment involving activators is to promote dento-alveolar changes. The goal of the second phase is creating an occlusion according to function- al occlusion patterns. The aim of this article is to present the sequence of a Class II Division 1 treatment case in two phases, in which a Teuscher activator appliance is used in the first phase.