Three dimensional finite element analysis of continuous and segmented arches with use of orthodontic miniscrews / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to compare the displacement patterns shown by finite element analysis when the maxillary anterior segment was retracted from different orthodontic miniscrew positions and different lengths of lever arms in lingual continuous and segmented arch techniques. METHODS: A three dimensional model was produced, the translation of teeth in both models was measured and individual displacement was calculated. RESULTS: When traction was carried out from miniscrews in the palatal slope, lingual tipping of crowns and extrusion of the maxillary anterior segment were found in both continuous and segmented arches as the lever arms were made shorter. With miniscrews in the midpalatal suture area, the displacement patterns were similar to the palatal slope, but bodily movement of the upper incisors was observed in both continuous and segmented arches with the lever arm at 20 mm. When lever arms were longer, there was less extrusion of the incisors and more buccal displacement of the canines. Such displacement was shown less in the continuous arch than the segmented arch. The second premolar showed crown mesial tipping and intrusion, and the molars showed distal tipping in the continuous arch. The posterior segment was displaced three dimensionally in the segmented arch, but the amount of displacement was less than the continuous arch. CONCLUSIONS: It is recommended that lever arms of 20 mm in length be used for bodily movement of the anterior segment. Use of continuous or segmented arches affect the displacement patterns and induce differences in the amount of displacement.

Tratamento ortodôntico do sorriso gengival utilizando-se mini-implantes (parte I): tratamento do crescimento vertical do complexo dentoalveolar anterossuperior / Orthodontic treatment of gummy smile by using mini-implants (part I): treatment of vertical growth of upper anterior dentoalveolar complex

Os mini-implantes ortodônticos têm revolucionado a biomecânica, bem como a ancoragem ortodôntica, a qual pode ser conseguida de maneira perfeitamente estável. Na primeira parte desse estudo, o sorriso gengival é definido e classificado de acordo com suas etiologias. Entre eles, o tipo dentoalveolar, uma boa indicação para tratamento com mini-implantes foi dividido em três categorias: (1) casos com crescimento vertical do complexo dentoalveolar anterior superior (casos 1, 2 e 3); (2) casos com protrusão do complexo dentoalveolar anterior (casos 4 e 5); e (3) casos com protrusão do complexo dentoalveolar anterossuperior e extrusão dos dentes posterossuperiores (casos 6 e 7). Três casos com excessivo crescimento vertical do complexo dentoalveolar anterossuperior são apresentados. Eles foram caracterizados com extrusão e lingualização dos incisivos superiores, sobremordida profunda e sorriso gengival. O objetivo desse artigo é mostrar o uso de mini-implantes na região anterior para intrusão de incisivos e correção do sorriso gengival. Foram utilizados mini-implantes nas regiões anterior e superior (1,6 x 6,0mm) e mola fechada de NiTi para intruir e vestibularizar os incisivos extruídos e lingualizados. Os mini-implantes podem ser utilizados com sucesso como ancoragem para intrusão de dentes anteriores.

Orthodontic mini-implants have revolutionized orthodontic anchorage and biomechanics by making anchorage perfectly stable. In this Part I, 'gummy smile' was defined and classified according to the etiologies. Among them, dentoalveolar type, a good indication of mini-implant treatment, was divided into three categories: (1) Cases with vertical growth of upper anterior dentoalveolar complex (Cases 1, 2, and 3), (2) Cases with protrusion of anterior dentoalveolar complex (Cases 4, and 5), and (3) Cases with protrusion of upper anterior dentoalveolar complex and extrusion of upper posterior teeth (Cases 6, and 7). Three cases with excessive vertical growth of the upper anterior dentoalveolar complex were presented. They were characterized with extruded and retroclined upper incisors, deep overbite, and gummy smile. The aim of this paper is to show that mini-implants are useful in the anterior area to intrude incisors and correct the gummy smile. An upper anterior mini-implant (1.6 x 6.0 mm) and a NiTi closed coil spring were used to intrude and procline the retroclined extruded incisors. Mini-implants can be used successfully as orthodontic anchorage to intrude anterior teeth.

Estudo laboratorial do tempo de fechamento das alças e do grau de inclinação do canino, durante o procedimento de retração, empregando mecânica de arco segmentado / Laboratorial study of the cuspid's retraction timing and tipping effects during space closure, using the segmented arch technique

OBJETIVO: avaliar o tempo de retração e o grau da inclinação sofrida pelo canino empregando três tipos de molas ortodônticas para retração - a alça em "T", a alça em "L" e a alça em forma de gota. MÉTODOS: foram utilizados três tipos de fio - aço inoxidável da marca comercial Morelli, aço inoxidável da marca comercial 3M Unitek e liga de beta-titânio da marca comercial Ormco; todos de calibre 0,019" x 0,025". A amostra resultante da combinação dos fatores mola e fio foi submetida à avaliação em modelo de typodont específico para essa finalidade. RESULTADOS: com relação ao tempo de fechamento das alças, verificou-se que um fechamento mais lento, e consequentemente com menor liberação de forças, foi obtido com o desenho de alça em "T" e, ainda, empregando-se a liga de beta-titânio para sua confecção. No que diz respeito à inclinação gerada pelas alças, as alças em forma de gota promoveram uma inclinação dentária maior do que as demais avaliadas. As alças em "T", por outro lado, mantiveram-se relacionadas estatisticamente aos menores valores de inclinação. Porém, quando se empregou o fio de aço inoxidável da marca comercial 3M Unitek para sua confecção, os três tipos de alça não apresentaram diferença estatisticamente significante. CONCLUSÃO: independentemente do desenho de alça empregado, aquelas construídas com liga de beta-titânio mantiveram-se relacionadas estatisticamente aos menores valores de inclinação observados para o elemento dentário movimentado.

OBJETIVE: Evaluate the cuspid's retraction time and tipping effects, after submitting it to three different orthodontic retraction loops: the "T" loop, the "boot" loop, and the "tear drop" loop. METHODS: It was used the following orthodontic wires: Morelli 0.019" x 0.025" stainless steel, 3M Unitek 0.019" x 0.025" stainless steel and Ormco 0.019" x 0.025" beta-titanium (TMAÕ). The resulting sample from the combination of these variables was submitted to a test developed on a typodont simulator used specifically for this purpose. RESULTS: As the closure timing concerns, it was verified that a slower closure and therefore, a smaller releasing force system was achieved by the "T" loop design and still, by employing the beta-titanium alloy on its construction. As to the tipping effects generated by the retraction device, the "tear drop" loop caused greater tipping effects than the other loops evaluated. The "T" loop, on the other hand, showed itself statistically related to the lowest tipping numerical values. However, when the 3M Unitek stainless steel wire was used to produce the device, all of the types of loops evaluated were considered statistically similar. CONCLUSION: Regardless of the loop design, the ones built out of beta-titanium alloy kept them statistically related to the lowest tipping numerical values observed for the retracted dental element.

A three-dimensional finite element analysis on the location of center of resistance during intrusion of upper anterior teeth / 대한치과교정학회지

This study was performed to locate the anteroposterior position of the center of resistance of upper anterior teeth when intrusive forces are acted on them by applying segmented arch mechanics. Three-dimensional finite elernent model of upper six anterior teeth, periodontal ligament and alveolar bone was constructed The locations of the center of resistance were compared according to the three variables, which are number of teeth contained in anterior segment, axial inclination of anterior teeth, and degree of alveolar bone loss. The following conclusions were drawn from this study; 1. When the axial inclination and alveolar bone height were normal, the locations of center of resistance of anterior segment according to the number of teeth contained were as follows; 1). In 2 teeth segment, the center of resistance was located in the distal area of lateral incisor bracket 2) In 4 teeth segment, the center of resistance was located in the distal 2/3 of the distance between the brackets of lateral incisor and canine. 3) In 6 teeth segment, the center of resistance was located in 3mm distal of canine bracket, which is interproxirnal area. between canine and 1st premolar. 4) As the number of teeth contained in anterior segment increased, the center of resistance shifted to the distal side. 2. As the labial inclination of incisors increased, the center of resistance shifted to the distal side. 3. As the alveolar bone loss increased, the center of resistance shifted to the distal side.