Wire Load-Deflection Characteristics Relative to Defferent Types of Brackets

抄録

OBJECTIVE. To test the hypothesis that the dimension of the bracket, both in labial and in lingual orthodontics, is a relevant parameter to determinate the forces that act on the teeth, and that some wires commonly used in labial orthodontics (0.016'-diameter SS, TMA and Nitinol) are not suitable for the first phase of lingual treatment.
MATERIALS AND METHODS. An ideal dental cast was bonded with eight different brackets (Damon 3MX, Ovation, Time 2, Innovation and Smart Clip Clarity for the vestibular face; STB, A Denta Time and Innovation-L for the lingual one). After photographic documentation, the interbracket distance was calculated for every type of bracket, using ImageJ software. The mean elasticity modulus of the tested wires was obtained from the review of the available Literature. With mathematic computation the theoretical wire load on every tooth was calculated at three different levels of deflection (0.5 mm; 1.0 mm and 1.5 mm), both on the labial and on the lingual side, for every type of bracket.
RESULTS. Lingual arch in the anterior sector is always shorter than vestibular arch. The different brackets, having different dimensions, have an influence on the interbracket distance, and as a consequence on the wire load. At large deflection, Superelastic NiTi expresses light and continuous forces which are significantly lower than the other examined alloy.
CONCLUSION. The initial hypothesis was supported. Because of the reduced interbracket distance, the adoption of superelastic wires is required in lingual mechanics and with lower diameter compared to labial mechanotherapy, in particular during the first phases of therapy. The use of a bracket with reduced medial-distal dimensions can contribute to reduce the load on the teeth.
KEY WORDS. Interbracket distance, superelasticity, lingual mechanotherapy