Light Activation and Thermocycling Methods on the Shear Bond Strength of Brackets Bonded to Porcelain Surfaces.

The present study was evaluated the effect of different light activation and thermocycling methods on the shear bond strength (SBS) and on the adhesive remnant index (ARI) of metal brackets bonded to feldspathic ceramic. Hundred metal brackets were bonded to 20 porcelain cylinders, divided into four groups (n=25) based on light activation and thermocycling processes. The cylinders were etched with 10% hydrofluoric acid for 60 s and coated with two layers of silane. The brackets were bonded with Transbond XT composite resin. Light activation in Groups 1 and 3 was performed during 3 s using the VALO Ortho Cordless appliance with irradiance 3,200 mW/cm2 and in Groups 2 and 4 for 40 s using Optilight Max appliance with irradiance 1,200 mW/cm². The samples were stored in deionized water at 37°C for 24 h and the samples from Groups 1 and 2 were submitted to the SBS test at a rate of 1 mm/min, whereas the samples from Groups 3 and 4 were submitted to 7,000 thermal cycles (5°/55°C) before to the SBS test. The data were assessed by two-way analysis of variance and by Tukey's test (a=0.05). No significant difference was observed between SBS means in the different light activation devices used. The samples subjected to thermocycling revealed lower SBS values (p≤0.05). There was predominance of score 0 for ARI in all groups. Therefore, the different light activation methods did not interfere in SBS, but thermocycling reduced SBS.

Aplicações clínicas da barra transpalatina removível / Clinical applications of the removable transpalatal arch

O presente artigo tem por objetivo discorrer sobre o emprego da barra transpalatina removível naprática ortodôntica. A ativação do arco transpalatino gera uma série de forças e binários clinicamenteúteis para mover os molares superiores nos três planos espaciais. Este dispositivo de fácil confecçãoapresenta importantes funções tais como: auxiliar na ancoragem, expansão e contração dos arcos,correção das rotações de molares, controle do torque e inclinações de molares, controle da extrusão demolares, correção da mordida cruzada unilateral e auxiliar no movimento de distalização dos molaresno arco superior. O conhecimento das possibilidades de emprego da barra transpalatina constitui umimportante recurso auxiliar na terapia ortodôntica.

The present article has for objective to discourse the use of the removable transpalatal arch inorthodontic treatment. The activation of the transpalatal arch generates a series of forces and binary clinically useful to move the maxillary molars in the three space plans. This device of easy making presents important such functions as: to aid in the anchorage, expansion and contraction of the arches,correction of the rotations of molars, control of the torque and inclinations of molars, control of theextrusion of molars, correction of the unilateral upper crossbite and auxiliary in the movement of distalization of maxillary molars. The knowledge of the possibilities of use the transpalatal arch constitutes an important auxiliary resource in the orthodontic therapy.