Indirect Bonding Method: in vitro Comparison of the Shear Bond Strength between Metallic Orthodontic Brackets and Different Porcelain Surface Preparations

Introduction : La force d’adhésion à l'interface métal-céramique avec les résines auto-polymérisantes destinées au collage indirect des boîtiers orthodontiques n'a pas été évaluée à ce jour et un protocole clinique basé sur la littérature scientifique est inexistant. Objectifs : 1) Comparer la force de cisaillement maximale entre des boîtiers métalliques et des surfaces en porcelaine préparées selon différentes méthodes; 2) Suggérer un protocole clinique efficace et prévisible. Matériel et méthodes : Quatre-vingt-dix disques en leucite (6 groupes; n = 15/groupe) ont été préparés selon 6 combinaisons de traitements de surface : mécaniques (+ / - fraisage pour créer les rugosités) et chimiques (acide fluorhydrique, apprêt, silane). Des bases en résine composite Transbond XT (3M Unitek, Monrovia, California) faites sur mesure ont été collées avec le système de résine adhésive auto-polymérisante Sondhi A + B Rapid Set (3M Unitek, Monrovia, California). Les échantillons ont été préservés (H2O/24hrs), thermocyclés (500 cycles) et testés en cisaillement (Instron, Norwood, Massachusetts). Des mesures d’Index d’adhésif résiduel (IAR) ont été compilées. Des tests ANOVAs ont été réalisés sur les rangs étant donné que les données suivaient une distribution anormale et ont été ajustés selon Tukey. Un Kruskall-Wallis, U-Mann Whitney par comparaison pairée et une analyse de Weibull ont aussi été réalisés. Résultats : Les médianes des groupes varient entre 17.0 MPa (- fraisage + acide fluorhydrique) à 26.7 MPa (- fraisage + acide fluorhydrique + silane). Le fraisage en surface ne semble pas affecter l’adhésion. La combinaison chimique (- fraisage + silane + apprêt) a démontré des forces de cisaillement significativement plus élevées que le traitement avec (- fraisage + acide fluorhydrique), p<0,05, tout en possédant des forces similaires au protocole typiquement suggéré à l’acide fluorhydrique suivi d’une application de silane, l’équivalence de (- fraisage + acide fluorhydrique + silane). Les mesures d’IAR sont significativement plus basses dans le groupe (- fraisage + acide fluorhydrique) en comparaison avec celles des 5 autres groupes, avec p<0,05. Malheureusement, ces 5 groupes ont des taux de fracture élévés de 80 à 100% suite à la décimentation des boîtiers. Conclusion : Toutes les combinaisons de traitement de surface testées offrent une force d’adhésion cliniquement suffisante pour accomplir les mouvements dentaires en orthodontie. Une application de silane suivie d’un apprêt est forte intéressante, car elle est simple à appliquer cliniquement tout en permettant une excellente adhésion. Il faut cependant avertir les patients qu’il y a un risque de fracture des restorations en céramique lorsque vient le moment d’enlever les broches. Si la priorité est de diminuer le risque d’endommager la porcelaine, un mordançage seul à l’acide hydrofluorique sera suffisant.

Comparison surface characteristics and chemical composition of conventional metallic and Nickel-Free brackets

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análise comparativa in vitro da resistência friccional entre braquetes metálicos e estéticos

O presente estudo visou comparar in vitro o atrito produzido por braquetes convencionais metálicos e estéticos com canaleta metálica e vítrea quando inseridos fios de secções redonda e retangular de diferentes dimensões, simulando situações sem deslocamento, com deslocamento de 2 mm e com simulação do efeito binding 3º. Foram utilizados 125 braquetes de 5 marcas comerciais (Roth Standard, Composite, Elation, Invu e Radiance), sendo 25 braquetes para cada corpo de prova. Para os ensaios laboratoriais, foram colados 5 braquetes simulando uma hemi-arcada superior direita (incisivos central e lateral, canino, primeiro e segundo premolares) em um dispositivo para posicionamento dos braquetes, sendo este acoplado à máquina universal de ensaios EMIC DL2000. Foram empregados os fios 0,016 , 0,018 e 0,017 x 0,025 NiTi para realização dos ensaios sem deslocamento e com deslocamento de 2 mm e os fios de secção 0,017 x 0,025 , 0,019 x 0,025 e 0,021 x 0,025 CrNi para realização dos ensaios com angulação zero grau e 3º. Para a comparação entre os braquetes nos diferentes fios e angulações, foi utilizada a Análise de Variância e o teste de Tukey (p<0,05). Os resultados demonstraram que nos ensaios sem deslocamento o braquete estético de policarbonato Composite apresentou menor atrito em todos os fios avaliados, enquanto o maior atrito em todas as combinações realizadas foi observado no braquete estético cerâmico monocristalino Radiance em relação aos demais braquetes. Nos ensaios com deslocamento de 2 mm e simulação do efeito binding 3º, os resultados foram semelhantes aos observados nos ensaios sem deslocamento. Contudo, houve uma diferença estatisticamente significante entre os cinco corpos de prova, sendo o atrito verificado, respectivamente e de forma crescente, nos braquetes Composite, Roth Standard, Elation, Invu e Radiance. Pôde-se concluir que a resistência friccional teve influência da composição dos braquetes, diâmetro dos fios e tipo de ensaio realizado (deslocamento de 2 mm e angulação de 3º). Além disso, a inserção da canaleta metálica no braquete estético de policarbonato Elation reduziu de forma estatisticamente significante o atrito, porém esse foi maior do que o gerado por um braquete convencional metálico e, por fim, a incorporação da canaleta vítrea no braquete estético cerâmico policristalino Invu ofereceu uma maior lisura de superfície, reduzindo as irregularidades e imperfeições presentes na canaleta o que levou, consequentemente, a uma redução estatisticamente significante no atrito, o que demonstra que a modificação em sua canaleta favoreceu o deslocamento e reduziu de forma efetiva essa resistência à fricção.

Spectrophotometric evaluation of dental bleaching under orthodontic bracket in enamel and dentin

Aware of the diffusion capacity of bleaching in the dental tissues, many orthodontists are subjecting their patients to dental bleaching during orthodontic treatment for esthetic purposes or to anticipate the exchange of esthetic restorations after the orthodontic treatment. For this purpose specific products have been developed in pre-loaded whitening trays designed to fit over and around brackets and wires, with clinical efficacy proven. Objective: The objective of this study was to evaluate, through spectrophotometric reflectance, the effectiveness of dental bleaching under orthodontic bracket. Material and Methods: Thirty-two bovine incisors crown blocks of 8 mm x 8 mm height lengths were used. Staining of tooth blocks with black tea was performed for six days. They were distributed randomly into 4 groups (1-home bleaching with bracket, 2- home bleaching without bracket, 3- office bleaching with bracket, 4 office bleaching without bracket). The color evaluation was performed (CIE L * a * b *) using color reflectance spectrophotometer. Metal brackets were bonded in groups 1 and 3. The groups 1 and 2 samples were subjected to the carbamide peroxide at 15%, 4 hours daily for 21 days. Groups 3 and 4 were subjected to 3 in-office bleaching treatment sessions, hydrogen peroxide 38%. After removal of the brackets, the second color evaluation was performed in tooth block, difference between the area under the bracket and around it, and after 7 days to verified color stability. Data analysis was performed using the paired t-test and two-way variance analysis and Tukey’s. Results: The home bleaching technique proved to be more effective compared to the office bleaching. There was a significant difference between the margin and center color values of the specimens that were subjected to bracket bonding. Conclusions: The bracket bond presence affected the effectiveness of both the home and office bleaching treatments.

Gesturing elsewhere: the identity politics of the Balinese death/thrash metal scene

This essay explores the political significance of Balinese death/thrash fandom. In the early 1990s, the emergence of a death/thrash scene in Bali paralleled growing criticism of accelerated tourism development on the island. Specifically, locals protested the increasing ubiquity of Jakarta, 'the centre', cast as threatening to an authentically 'low', peripheral Balinese culture. Similarly, death/thrash enthusiasts also gravitated toward certain fringes, although they rejected dominant notions of Balinese-ness by gesturing elsewhere, toward a global scene. The essay explores the ways in which death/thrash enthusiasts engaged with local discourses by coveting their marginality, and aims to demonstrate how their articulations of 'alien-ness' contributed in important ways to a broader regionalism.