Maxillary incisor retraction: evaluation of different mechanisms

Abstract

Objective:To mechanically evaluate different systems used for incisors retraction. Methods: Three different methods for incisors retraction using 0.019 x 0.025-in stainless steel wire were evaluated. The samples were divided into three groups: Group A (retraction arch with 7-mm high vertical hooks); Group G3 (elastic chain attached to the miniimplant and to the 3-mm stainless steel hook soldered to the retraction arch); Group G6 (elastic chain attached to the mini-implant and to the 6-mm stainless steel hook soldered to the retraction arch). A dental mannequin was used for evaluation in order to simulate the desired movements when the device was exposed to a heat source. The analysis of variance (ANOVA) and the Tukey test were used (p < 0.05). Results: The results demonstrated that Groups G3 and G6 exhibited less extrusion and less incisor inclination during the retraction phase (p < 0.05). With regard to incisor extrusion, statistically significant differences were observed between Groups A and G3, and between Groups A and G6 (p < 0.05). Regarding incisor inclination, statistically significant differences were observed between the three systems evaluated (p < 0.05). Conclusions: Arches with 6-mm vertical hooks allow the force to be applied on the center of resistance of the incisors, thus improving mechanical control when compared with the other two systems. original article Objetivo: avaliar mecanicamente diferentes sistemas utilizados para retração de incisivos. Métodos: três diferentes métodos de retração dos incisivos foram avaliados, utilizando arco ortodôntico de retração confeccionado com fio de aço inoxidável 0,019" x 0,025" de espessura. Os grupos foram divididos em: Grupo A (arco de retração com alças verticais de 7mm de altura), Grupo G3 (elástico em cadeia ligado do mini-implante ao gancho de aço inoxidável com 3mm de altura soldado no arco de retração) e Grupo G6 (elástico em cadeia ligado do mini-implante ao gancho de aço inoxidável com 6mm de altura soldado no arco de retração). Para essa avaliação, adequou-se um manequim odontológico de tal forma que possibilitasse simular os movimentos desejados, quando fosse exposto a uma fonte de calor. Após obtenção das medidas dos movimentos, realizou-se análise estatística. Resultados: os resultados demonstraram que os grupos G3 e G6 propiciaram menor extrusão e menor inclinação palatina dos incisivos na fase de retração (p<0,05). Quanto à extrusão dos incisivos, houve diferença estatisticamente significativa entre os grupos A e G3, e A e G6 (p<0,05). Em relação à inclinação, ocorreu diferença estatisticamente significativa entre os três sistemas avaliados (p<0,05). Conclusão: arcos com ganchos verticais de 6mm soldados permitem aproximar a linha de ação da força ao centro de resistência dos incisivos, proporcionando melhor controle mecânico, se comparado aos outros dois sistemas.Palavras-chave: Ortodontia corretiva. Má oclusão. Mecânica.

Evaluation of Risk Factors for Severe Apical Root Resorption in the Maxillary Incisors Following Fixed Orthodontic Treatment

“…Consequently, retraction of incisors result in uprighting and relative extrusion as the crown was retracted below the center of rotation (Kuhlberg and Nanda, 2005). The same extrusive effect was also seen with sliding mechanics; as incisors are pulled below the center of rotation, and torque loss occur (Jayaratne et al, 2017;Ruellas et al, 2013). This extrusive movement results in worsening any deep bite present before retraction, and maxillary or mandibular incisors should be intruded to compensate this effect.…”

“…This finding is contradicted by many authors, who reported that intrusion is most likely to be a risk factor for root resorption when compared to extrusion; intrusion of teeth causes about four times more root resorption than extrusion (Han et al, 2005;Parker and Harris, 1998). This finding can be justified because the extractions of premolars, space closure, and retractions of incisors result in controlled and uncontrolled tipping of these teeth, which affect the incisors angulation and have extrusive forces (Jayaratne et al, 2017;Luiz et al, 2016;Ruellas et al, 2013;Sarver and Weissman, 1995). In Orthodontics department, Marmara University, two space closure mechanics are applied; sliding mechanics and closing loops.…”

Dental arch and Smile Changes Following Miniscrew Anchored En-masse Retraction of Anterior Teeth in Class II Division 1 Malocclusion

“…Anterior teeth were retracted sequentially; A force of 100-g was applied to retract maxillary canine by Ni-Ti closed coil spring ligated with a wire to the canine bracket hook [15] . After canine retraction, the maxillary incisors were retracted by 130-g force using Ni-Ti closed coil spring extending from the hook of the buccal tube on the first molar band to helices placed distal to lateral incisors [16] (Figure 2).…”

Change in crown inclination accompanying initial tooth alignment with round archwires

“… 10 This action requires full-size archwires to avoid play between the archwire and the slot walls. 11 , 12 However, archwire of a round cross-section is the standard choice for initial leveling and alignment. 13 Round archwires produce tipping movement, thus changing crown inclination, which may be or may not be desired.…”