Enamel loss and superficial aspect during bonding and debonding of metallic brackets / Perda de esmalte e aspecto superficial durante colagem e descolagem de bráquetes metálicos

To evaluate the cumulative enamel loss during bonding and debonding procedures of orthodontic metallic brackets and to analyze the enamel superficial roughness. Forty-seven maxillary first premolars were obtained for quantitative and qualitative analysis. For quantitative analysis, forty premolars were weighed at each stage of treatment and the equivalent thickness of enamel loss was measured. The amount of tooth mass loss in each stage was divided by the density value to obtain the corresponding enamel volume lost. Subsequently, these volumes were divided by a circular area with a diameter of 7 mm, thus obtaining the equivalent thickness of enamel loss. They were assessed under the following conditions: as sound enamel, after acid conditioning, following the removal of residual resin composite, after final polishing with high or low-speed, and with or without water refrigeration. A rugosimeter was used to obtain a graphic registration of the enamel superficial roughness before and after acid conditioning. The data were analyzed with the Quantikov software and the Shapiro Wilk's and Wilcoxon statistical tests were used to evaluate enamel superficial roughness. The one-way ANOVA followed by Bonferroni Post-Hoc tests were used to analyze the amount of enamel loss. For qualitative analysis, scanning electron microscopy (SEM) of the enamel surfaces was performed on seven premolars, one in each step. Acid conditioning significantly increased enamel surface roughness (p<0.01). Based on the dental mass weighed after each stage of evaluation, enamel loss was statistically significant in all stages (p<0.01). However, when the 4 different final polishing methods were compared, no statistically significant differences were registered regarding loss of mineralized structure (p=0.72). The SEM analysis revealed that the tungsten-carbide bur with water refrigeration and lowspeed rubber points caused less damage to the enamel. The greatest amount of enamel loss was due to acid conditioning. The losses relative to abrasion with composite removal or after the 4 polishing protocols were similar. Finally, none of the enamel surfaces was restored to their original aspects after bonding and debonding metallic brackets.

Determinar a perda de esmalte durante os procedimentos de colagem e descolagem de bráquetes ortodônticos e analisar a rugosidade superficial do esmalte. Quarenta e sete primeiros pré-molares superiores foram obtidos para análise quantitativa e qualitativa. Para a análise quantitativa, quarenta pré-molares foram pesados em cada uma das etapas do tratamento e a espessura equivalente do esmalte foi medida. A perda de massa em cada fase foi dividida pelo valor de densidade do esmalte para obter o volume correspondente. Em seguida, o volume foi dividido pela área circular de 7 mm de diâmetro, obtendo-se assim a espessura equivalente da perda de esmalte. Os dentes foram avaliados nas seguintes condições: esmalte íntegro, após condicionamento ácido, depois da remoção da resina remanescente e após o polimento final em alta e baixa rotação, com e sem refrigeração. Ainda foi utilizado um rugosímetro para obtenção dos registros gráficos de perfis da rugosidade superficial do esmalte antes e após o condicionamento ácido. Os dados foram analisados utilizando-se o software Quantikov, para determinação e comparação dos comprimentos dos registros obtidos antes e após o condicionamento ácido, o teste Shapiro Wilk e o Wilcoxon para rugosidade superificial do esmalte e, por fim, o ANOVA um fator seguido pelo Bonferroni Post-Hoc para perda de esmalte. Para a análise qualitativa, foi empregada a microscopia eletrônica de varredura nas superfícies de esmalte de sete pré-molares, um dente para cada etapa. O condicionamento ácido promoveu o aumento do comprimento do perfil de superfície do esmalte, ou seja, o aumento da rugosidade (p<0,01). Na avaliação da massa dos elementos dentários, percebeu-se que a perda de esmalte foi estatisticamente significante em todas as etapas do experimento (p<0,01). Entretanto, ao comparar os diferentes métodos de polimentos, verificou-se que não há diferença estatisticamente significante na perda de estrutura mineralizada (p=0,72). Na análise da microscopia eletrônica de varredura, a remoção da resina com broca carbide de tungstênio multilaminada com refrigeração e o polimento em baixa rotação sob refrigeração apresentaram menos dano ao esmalte. A maior perda de esmalte foi devida ao condicionamento ácido. As perdas referentes ao desgaste com a broca e o polimento são semelhantes e os 4 protocolos de polimento testados resultaram em diminuições similares na espessura do esmalte. Nenhuma das superfícies de esmalte foi restaurada ao seu aspecto original após a colagem e descolagem de bráquetes metálicos.

Comparative Study of the Effect of Acid Etching on Enamel Surface Roughness between Pumiced and Non-pumiced Teeth.

BACKGROUND: The objective was to perform a comparative analysis of the effect of acid etching on enamel roughness between pumiced and non-pumiced teeth. MATERIALS AND METHODS: The sample was composed of 32 dental surfaces divided into two groups: Group 1-16 surfaces having received pumice prophylaxis; and Group 2-16 surfaces not having received pumice prophylaxis. The teeth were kept in saline until the first record of surface roughness prior to etching. For each surface, a roughness graph was obtained through trials using a surface roughness tester. This procedure was repeated two more times at different locations for a total of three readings which, later, were converted in a mean value. The teeth were then acid etched with a 37% phosphoric acid for 60 s, rinsed with water, air dried, and tested with the roughness tester again using the same protocol described for baseline. The Quantikov image analysis program was used to measure the length of the graphs. The average value of the lengths was recorded for each surface before and after etching. The increase in roughness caused by acid etching was calculated and compared between groups. RESULTS: The mean increase in roughness caused by the etching was 301 µm (11.37%) in Group 1 and 214 µm (8.33%) in Group 2. No statistically significant difference was found between samples with and without pumice prophylaxis (P = 0.283). CONCLUSION: The present study showed that the effect of acid etching on enamel roughness was not significantly affected by prior pumice prophylaxis.

Physical and chemical properties of orthodontic brackets after 12 and 24 months: in situ study

Objective: The aim of this article was to assess how intraoral biodegradation influenced the surface characteristics and friction levels of metallic brackets used during 12 and 24 months of orthodontic treatment and also to compare the static friction generated in these brackets with four different methods of the ligation of orthodontic wires. Material and Methods: Seventy premolar brackets as received from the manufacturer and 224 brackets that were used in previous orthodontic treatments were evaluated in this experiment. The surface morphology and the composition of the deposits found in the brackets were evaluated with rugosimetry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Friction was analyzed by applying tensile tests simulating sliding mechanics with a 0.019x0.025" steel wire. The static friction levels produced by the following ligation methods were evaluated: loosely attached steel ligature around all four bracket wings, steel ligature attached to only two wings, conventional elastomeric ligation around all 4 bracket wings, and non-conventional Slide® elastomeric ligature. Results: The results demonstrated the presence of biodegradation effects such as corrosion pits, plastic deformation, cracks, and material deposits. The main chemical elements found on these deposits were Carbon and Oxygen. The maximum friction produced by each ligation method changed according to the time of intraoral use. The steel ligature loosely attached to all four bracket wings produced the lowest friction levels in the new brackets. The conventional elastic ligatures generated the highest friction levels. The metallic brackets underwent significant degradation during orthodontic treatment, showing an increase in surface roughness and the deposit of chemical elements on the surface. Conclusion: The levels of static friction decreased with use. The non-conventional elastic ligatures were the best alternative to ...

Avaliação das concentrações de zinco no aparelho reprodutor feminino por ativação neutrônica instrumental / Assessment of zinc concentration in the female reproductive system by instrumental neutron activation

A esterilização feminina não cirúrgica por meio da aplicação intracervical de pastilhas de cloridrato de quinacrina foi considerada um método contraceptivo definitivo de baixo custo, seguro e eficaz. O zinco, presente no útero e nas tubas uterinas, inibe a ação da quinacrina. A adição de cobre aumenta a eficácia da quinacrina, reduzindo o risco de gravidez devido às falhas de obstrução das tubas uterinas. O cobre neutraliza o efeito deletério do zinco, aumentando a eficácia do método. Para obter o mapeamento da concentração de zinco no aparelho reprodutor feminino, amostras de útero e de tubas uterinas foram analisadas por ativação neutrônica instrumental. Os resultados obtidos são apresentados neste trabalho.

Nonsurgical female sterilization through the transcervical insertion of quinacrine pellets was considered a definitive, low-cost, safe and effective contraceptive method. The zinc, present in both uterus and Fallopian tubes, inhibit the action of quinacrine. The addition of copper increases the efficacy of quinacrine, thus reducing the risk of pregnancy due to the failure to obstruct the Fallopian tubes. The copper neutralized the deleterious effect of the zinc and so the treatment efficacy is increased. In order to obtain a mapping to study the zinc concentration in the female reproductive system, samples of both uterus and Fallopian tubes were analyzed by neutron activation. The results are here reported.