RESUMO
Orthodontic treatment can cause resorptions on teeth. Factors causing resorptions are forces and moments. Other factors that cause resorptions are less influenced by an orthodontic treatment. By carrying out experiments and finite element calculations, it was possible to demonstrate that forces and moments will produce stress in certain parts of the periodontal ligament and the root. This stress reaches or exceeds the blood pressure in some areas. To avoid high pressure in those areas, new treatment devices were constructed consisting of NiTi wires or a combination of NiTi and stainless steel. In the levelling phase, the acting forces remained below 0.5 N using NiTi wire with a diameter of 0.012' (using elastic ligatures). With a NiTi stainless steel spring molars can be uprighted. The orthodontist can easily choose between an intrusive force, a very low intrusive force and an extrusive force. Because of the use of NiTi elements, there was acting an almost constant moment.
Assuntos
Desenho de Aparelho Ortodôntico , Fios Ortodônticos , Ligamento Periodontal/patologia , Reabsorção da Raiz/patologia , Animais , Análise de Elementos Finitos , Humanos , Níquel , Aço Inoxidável , Estresse Mecânico , Suínos , TitânioRESUMO
There are powerful non-rational forces in patients and therapists alike, and in the therapeutic context. These forces often determine whether individual or family therapy is chosen. Historical, cultural, and economic forces, patient and family motivations, and therapist preferences are all powerful determinants of modality choice. This is partly due to the newness of the field of family therapy, and will probably continue until we have a better conceptual grasp of family theory and nosology, the interrelation of individual and family pathology, and a clearer delineation of the criteria for these modalities.
