Effect of antioxidant on orthodontic bracket bond strength after vital bleaching

The objective of this study is to compare the neutralization effect of various antioxidant agents on the bond strength of composite resins on stainless steel and ceramic brackets immediately bonded to previously bleached teeth. Materials and Methods: One hundred and sixty human maxillary premolars were used for the study. Teeth were divided into four groups (n = 40): Group 1 (control), Group 2 (bleached), Group 3 (sodium ascorbate), and Group 4 (tocopherol acetate). Each group was divided into two subgroups, one was bonded with stainless steel and other with ceramic brackets using 3M Transbond XT. Universal testing machine was used to determine the shear bond strength (SBS). Results: Among the metal brackets, Group 1A had the highest SBS (12.18 + 1.41 MPa) and Group 2A had the least SBS (6.18 + 1.49 MPa). Weibull analysis indicated that bond strength for a 90% probability of failure was highest for Group 1A (13.99 MPa) and lowest for Group 2A (8.49 MPa). For ceramic brackets, Group 1B had the highest SBS (13.80 + 1.69 MPa) and Group 2B had the least SBS (8.05 + 1.85 MPa). Weibull analysis indicated that bond strength for a 90% probability of failure was highest for Group 1B (14.61 MPa) and lowest for Group 2B (8.85MPa). Conclusion: The in vitro study showed that bleaching reduced the SBS significantly, and this could be effectively reversed by the application of antioxidants in both metal and ceramic brackets.

A CBCT evaluation of molar uprighting by conventional versus microimplant-assisted methods: an in-vivo study

ABSTRACT Objective: The aim of this prospective study was to compare the three-dimensional effects of the conventional helical uprighting spring (CA) and the mini-implant assisted helical uprighting spring (MIA), using CBCT scans. Methods: Twenty patients with mesially tipped second mandibular molars were divided into two groups: CA group, in which 10 patients were treated using a conventional helical uprighting spring with conventional anchorage; and MIA group, in which 10 patients were treated using a mini-implant supported uprighting spring. Molar uprighting was observed in both groups for a period of four months. Two standardized 11×5-cm CBCT sections of the mandible were taken, being one prior to uprighting and one at the end of the four month follow-up. Statistical analyses at the beginning of treatment and after a 4 month follow-up were performed, with a significance level of p< 0.05. Results: The mean amount of change in mesiodistal angulation in the MIA group was 8.53 ± 2.13o (p< 0.001) and in the CA group was 9.8 ± 0.5o (p< 0 .001). Statistically significant differences were found between the two groups with regard to buccolingual inclination of canine, first and second premolars (p< 0.05), second molar (p< 0.001) and extrusion of second molar (p< 0.05). Conclusions: The mean amount of change in the mesial angulation of the second molar in the CA as well as the MIA groups was similar. MIA, which used mini-implant as a source of anchorage, was more effective in preventing movement of the anchorage teeth as well as preventing extrusion of the second molar in the vertical plane, when compared to the CA group, which used dental units as a source of anchorage.

RESUMO Objetivo: o objetivo deste estudo prospectivo foi comparar, usando imagens de TCFC, os efeitos tridimensionais da mola convencional de verticalização (CA) e da mola de verticalização com ancoragem em mini-implantes (MIA). Métodos: vinte pacientes com segundos molares inferiores inclinados mesialmente foram divididos em dois grupos: grupo CA, no qual 10 pacientes foram tratados usando mola helicoidal de verticalização com ancoragem convencional; e grupo MIA, com 10 pacientes tratados usando mola de verticalização ancorada em mini-implantes. A verticalização dos molares foi observada nos dois grupos por um período de quatro meses. Foram obtidas duas secções tomográficas da mandíbula, com dimensões padronizadas de 11 x 5 cm, uma antes da verticalização e outra ao fim dos quatro meses de acompanhamento. As análises estatísticas ao início do tratamento e após os quatro meses de acompanhamento foram realizadas a um nível de significância de p< 0,05. Resultados: a média das alterações na angulação mesiodistal do grupo MIA foi de 8,53 ± 2,13o (p< 0,001), e do grupo CA foi de 9,8 ± 0,5o (p< 0,001). Diferenças estatisticamente significativas foram encontradas entre os dois grupos em relação à inclinação vestibulolingual do canino, do primeiro e segundo pré-molares (p< 0,05) e do segundo molar (p< 0,001), bem como para a extrusão do segundo molar (p< 0,05). Conclusões: a alteração média na angulação mesial do segundo molar nos grupos CA e MIA foi semelhante. O método MIA, que usou mini-implantes como ancoragem, foi mais efetivo na prevenção da movimentação dos dentes de ancoragem, bem como na prevenção da extrusão do segundo molar no plano vertical, quando comparado com o grupo CA, em que dentes foram usados como fonte de ancoragem.

Effect of fluoride mouth rinses on various orthodontic archwire alloys tested by modified bending test: An in vitro study.

Objective: Fluorides can cause corrosion and degradation in mechanical properties of commonly used archwires by forming hydrofluoric acid HF and causing disruption of protective titanium oxide layer. Hence, the aim of this study was to assess the change in load deflection characteristics of Ni-Ti, Cu Ni-Ti, S.S, and β-Ti wires on immersing in fluoride mouth rinses of two types- Phosflur and neutral NaF mouth rinse utilizing a modified bending test and comparing it to control. Materials and Methods: Round preformed wires were immersed in 10 ml of control and test solution (Phosflur and S-Flo mouth rinse) for 1.5 hours and incubated at 37°C. Modified bending test was carried out to evaluate load-deflection characteristics of different wires using Instron. Analysis of variance (ANOVA) was applied to determine if statistically significant difference exist among the mean load values obtained at various deflections in control and test solutions. Results: There was no statistically significant reduction in load deflection characteristics of Ni-Ti, copper Ni-Ti, β-Ti, and S.S wires on immersing in Phosflur mouth rinse and neutral sodium fluoride mouth rinses as compared to control at 2.5 and 1 mm of deflection in unloading phase. Conclusion: Phosflur and a neutral sodium fluoride mouth rinse did not affect the mechanical bending properties of Ni-Ti, copper Ni-Ti, B-Ti, and SS wires in in vitro conditions.