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.
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.
Subject(s)
Humans , Dental Implants , Incisor/pathology , Malocclusion/therapy , Maxilla/pathology , Orthodontic Wires , Orthodontic Anchorage Procedures/instrumentation , Tooth Movement Techniques/instrumentation , Analysis of Variance , Manikins , Orthodontic Anchorage Procedures/methods , Tooth Movement Techniques/methodsABSTRACT
Objective: To investigate the effects of surface sealing on the shear bond strength(SBS) of the brackets. Methods: Twenty extracted premolars for orthodontics were cut into the buccofacial teeth pieces and etched by Transbond~TM Plus self-etching primers for 30 seconds firstly, then divided into two groups with 10 teeth pieces in each group randomly. ① experiment group, the buccal surface of the enamel was sealed with Filtek Flow 1400A3 flowable composite resin before bracket bonding;②control group, the bracket was bonded to the buccal surface of the enamel directly. All specimens were stored in deionized water at 37 ℃ for 48 h, thermocycled for 1 000 times at 30-second intervals between 5 ℃ and 55 ℃ water baths, and debonded with a universal testing machine. The amounts of resin remaining on the teeth pieces after debonding by using the resin remnant index (RRI), which were examined under 10×magnification stereo-microscope. Results: The SBS(MPa) between experiment group and control group was 8.08±1.38, 8.34±1.37 respectively, whereas the RRI was 2.80±1.03, 3.20±1.03 respectively. The SBS, RRI between experimental group and control group revealed no statistically significant differences. Conclusion: Surface sealing shows adequate bond strength, which is considered a clinically acceptable bond strength. The debonding of bracket is not affected by the surface sealing.