Influência do óxido de alumínio na colagem dos bráquetes linguais / The influence of the aluminun oxide on lingual brackets bonding

A descolagem acidental do bráquete é uma severa complicação no decorrer do tratamento ortodôntico, especialmente quando o tratamento é feito com bráquetes linguais. A força de adesão entre o bráquete e o dente é um importante requisito para o sucesso da Ortodontia Lingual na prática diária do consultório. O presente estudo analisou a influência do jateamento do óxido de alumínio na superfície lingual dos dentes antes do condicionamento do esmalte na colagem indireta do aparelho lingual. A força de cisalhamento foi medida 24 horas após a colagem dos bráquetes. Os dentes foram divididos em quatro grupos: G1 - 10 pré-molares com bráquetes da marca American Orthodontics com condicionamento de ácido ortofosfórico a 37%; G2 - 10 pré-molares com bráquetes da marca American Orthodontics com aplicação do jato de óxido de alumínio e ácido ortofosfórico a 37% no esmalte; G3 - 10 pré-molares com bráquetes da marca Ormco com condicionamento de ácido ortofosfórico a 37% e G4 - 10 pré-molares com bráquetes da marca Ormco com aplicação do jato de óxido de alumínio e ácido ortofosfórico a 37% no esmalte. Avaliou-se a resistência ao cisalhamento e observou-se que não ocorreu diferença estatisticamente significante entre os grupos quanto aos diferentes modos de preparo de esmalte. Com relação às marcas comerciais, os bráquetes da American Orthodontics apresentaram resistência à descolagem maior do que os bráquetes da marca Ormco. Concluindo, a resistência à descolagem dos bráquetes não foi aumentada com a aplicação prévia do jato de óxido de alumínio no esmalte hígido, nas duas marcas comerciais de bráquetes.

Accidental bracket debonding is a severe complication throughout orthodontic treatment, especially when using lingual brackets. The bond strength between the bracket and the tooth is an important requirement for the success of Lingual Orthodontics. This study has analyzed the influence of aluminum oxide blasting on the lingual surface of the teeth, before conditioning of the enamel, over indirect bonding of the lingual brace. Shear strength was measured 24 hours after brackets bonding. Teeth were divided into four groups: G1 - 10 premolar teeth with American Orthodontics brackets and 37% orthophosphoric acid conditioning; G2 - 10 premolar teeth with American Orthodontics brackets and application of aluminum oxide and 37% orthophosphoric acid blasting on the enamel; G3 - 10 premolar teeth with Ormco brackets and 37% orthophosphoric acid conditioning; G4 - 10 premolar teeth with Ormco brackets, application of aluminum oxide and 37% orthophosphoric acid blasting on the enamel. When evaluating the shear resistance through mechanical assay, it was not observed statistically significant difference between the groups regarding different enamel preparation modes. Concerning the different commercial brands, the American Orthodontics brackets showed higher debonding resistance than the Ormco brackets. It was concluded that, for both brands of brackets, the resistance to bracket debonding did not increase with the previous application of aluminum oxide blasting on the ename.

Interaction between staining and degradation of a composite resin in contact with colored foods

Composite resins might be susceptible to degradation and staining when in contact with some foods and drinks. This study evaluated color alteration and changes in microhardness of a microhybrid composite after immersion in different colored foods and determined whether there was a correlation between these two variables. Eighty composite disks were randomly divided into 8 experimental groups (n = 10): kept dry; deionized water; orange juice; passion fruit juice; grape juice; ketchup; mustard and soy sauce. The disks were individually immersed in their respective test substance at 37 ºC, for a period of 28 days. Superficial analysis of the disk specimens was performed by taking microhardness measurements (Vickers, 50 g load for 45 seconds) and color alterations were determined with a spectrophotometer (CINTRA 10- using a CIEL*a*b* system, 400-700 nm wavelength, illuminant d65 and standard observer of 2º) at the following times: baseline (before immersion), 1, 7, 14, 21 and 28 days. Results were analyzed by ANOVA and Tukey's test (p < 0.05). Both variables were also submitted to Pearson's correlation test (p < 0.05). The passion fruit group underwent the greatest microhardness change, while the mustard group suffered the greatest color alteration. Significant positive correlation was found between the two variables for the groups deionized water, grape juice, soy sauce and ketchup. Not all color alteration could be associated with surface degradation.

Avaliação, pelo método digital, da alteração de cor decorrente de ressecamento / Digital evaluation of color change caused by tooth desiccation

Durante alguns atos operatórios, quando se utiliza o isolamento absoluto ou relativo, o dente sofre desidratação e com ela pode haver uma alteração da sua cor, que é crítica para os procedimentos estéticos. Este estudo in vivo avaliou o efeito da desidratação na alteração de cor em incisivos centrais vitais hígidos. Participaram 20 pacientes, com idades entre 20 e 40 anos. Foram tiradas 11 fotografias com uma câmera digital Canon EOS 20D, com lentes de 18-55 mm e 58 mm de diâmetro. As imagens foram inseridas e normalizadas no software Adobe Photoshop. Observou-se alteração de cor em todas as amostras. No entanto, não se observou um padrão de alteração. Podemos concluir também que a máquina digital pode ser usada para avaliação da alteração de cor, desde que se use um padrão conhecido.

When using field isolation the teeth suffers desiccation that may lead to a color change that compromise the esthetic quality of restorative procedures. ln this in vivo study the effect of color change on maxillary central incisors was evaluated in 20 patients with age ranging from 20 to 40 years. Eleven pictures were taken. A digital camera Canon EOS 20D and lenses with 18-55 mm and 58 mm diameter were used. The software Adobe Photoshop was used for image acquisition and subsequent image processing. Color change was observed in all samples. However, a pattern was not observed. We can also conclude that the digital camera can be used to evaluate color change when a known standard is used.

Influence of the distance of the curing light source and composite shade on hardness of two composites

This study evaluated the influence of curing tip distance, shade and filler particle size on Vickers microhardness (VHN) of composite resins. Two composites were tested: Filtek Z250 microhybrid (3M ESPE; shades A1 and A3.5) and Filtek Supreme nanofilled (3M ESPE; shades A1B and A3.5B). For each resin, 42 specimens (5 mm in diameter and 2 mm height) were prepared being 21 for each shade. The specimens were exposed using a 20-second exposure to a quartz-tungsten-halogen light source with an irradiance of approximately 560 mW/cm², at the following distances: 0 mm (surface contact), 6 mm and 12 mm from composite surface. Effectiveness of cure of different resins, shades and curing distances was determined by measuring the top and bottom hardness (VHN) of specimens using a digital microhardness tester (load: 50 g; dwell time: 45 seconds) 24 hours following curing. The hardness ratio was calculated by dividing VHN of the bottom surface by VHN of top surface. Three-way ANOVA and Tukey's post-hoc test (p<0.05) revealed statistically significant differences for all analyzed factors. As for top hardness, as microhardness ratio (bottom/top), the factors shade, distance and composite filler particle size exerted influence on resin curing. Lighter shade composites (A1 and A1B) showed higher hardness values. At 6 and 12 mm curing tip distances, hardness was lower when compared to 0 mm. The microhybrid composite resin presented higheer hardness, being its microhardness ratio satisfactory only at 0 mm for both shades and at 6 mm for the lighter shade. The nanofilled composite resin did not present satisfactory microhardness at the bottom while the microhybrid composite resin had higher hardness than the nanofilled. Composite's curing tip distance and shade can influence hardness.

Desgaste dental causado por diferentes cerdas de escovas dentais / Dental wear caused by different toothbrush stiffness bristles

Introdução - O objetivo deste estudo foi comparar o desgaste dental produzido por três diferentes durezas de cerdas de escovas dentais, utilizando a dentina bovina como substrato. Métodos - Foram utilizadas 10 escovas, para cada tipo de cerda: Macia (G1), Média (G2) e Dura (G3). Trinta segmentos de raízes bovinas foram devidamente preparados. Os espécimes foram divididos, aleatoriamente, em 3 grupos (n=10). Em seguida, submetidos ao teste de escovação mecânica, empregando-se 20.000 ciclos. Para a análise do desgaste produzido, foram executadas medições do peso inicial e final utilizando uma balança analítica. Além disso, dados encontrados foram analisados por ANOVA e Teste de Tukey (p<0,05). Resultados - As médias das diferenças de peso encontradas foram: G1-0,00639a; G2-0,01149b; G3-0,01513c. As médias de perda de perfil foram: G1-0,1282a; G2-0,1789ab; G3-0,2146b. Conclusão - Conclui-se que as escovas dentais com cerdas duras promoveram maior desgaste da superfície dentária bovina.