The effect of surface treatment and thermocycling on the shear bond strength of orthodontic brackets to the Y-TZP zirconia ceramics: A systematic review

ABSTRACT Introduction: Various surface pre-treatment methods have been adapted to optimize the bonding between the zirconia ceramics and the orthodontic brackets. Objective: This review is aimed at systematically analyzing the relevant data available in the literature, to find out the most effective and durable bonding protocol. Methods: Database search was conducted in PubMed, Scopus, and ScienceDirect, during September 2020. The review was conducted according to the PRISMA guidelines. Results: Based on the inclusion criteria, 19 articles were selected for qualitative analysis. Meta-analysis could not be performed due to the heterogeneity of the methodology among the studies. Most of the studies scored medium risk of bias. Compared to the untreated surface, surface pretreatments like sandblasting and lasers were advantageous. Primers and universal adhesive were mostly used as an adjunct to the mechanical pretreatment of the zirconia surface. In most studies, thermocycling seemed to lower the shear bond strength (SBS) of the orthodontic brackets. Conclusion: Based on this qualitative review, surface pretreatments with lasers and sandblasting can be suggested to optimize the bracket bond strength. To clarify this finding, meta-analysis is anticipated. Hence, high heterogeneity of the included studies demands standardization of the methodology.

RESUMO Introdução: Diferentes métodos de pré-tratamento da superfície foram adaptados para otimizar a colagem entre os braquetes ortodônticos e as cerâmicas de zircônia. Objetivo: A presente revisão teve como objetivo analisar, de forma sistemática, os dados relevantes na literatura, para buscar o protocolo de colagem mais efetivo e duradouro. Métodos: As buscas foram feitas em setembro de 2020, nas seguintes bases de dados: PubMed, Scopus e ScienceDirect. A revisão foi feita de acordo com as diretrizes do PRISMA. Resultados: Com base nos critérios de inclusão, 19 artigos foram selecionados para análise qualitativa. A metanálise não pôde ser feita, devido à heterogeneidade na metodologia dos estudos incluídos. A maior parte dos estudos apresentou risco de viés moderado. Comparadas às superfícies não tratadas, as superfícies com pré-tratamento usando jateamento ou laser apresentaram vantagem. Primers e adesivos universais foram mais usados como adjuntos ao pré-tratamento mecânico da superfície de zircônia. Na maioria dos estudos, a termociclagem parece ter reduzido a resistência ao cisalhamento dos braquetes ortodônticos. Conclusões: Com base nessa revisão qualitativa, os pré-tratamentos de superfície com laser e jateamento podem ser sugeridos para otimizar a resistência ao cisalhamento dos braquetes. Para esclarecer esse achado, uma metanálise é necessária. Para isso, faz-se necessária a padronização da metodologia, para lidar com a alta heterogeneidade dos estudos incluídos.

Effect of PVA-PEG Binders on Surface Roughness of Y-TZP Zirconia

@#Introduction: Y-TZP Zirconia is a ceramic used for dental implants because it has good biocompatibility and aesthetic properties, and it is affordable. Y-TZP formed from powder using uniaxial pressing with some added binder. The binders used are PVA, PEG and a combination of both. This combination reduce hardness and improve plasticity properties. Significantly increasing of the binder concentration and the surface roughness of the implant increases the porosity of the material as a place for the osseointegration process. Thus, the purpose of this study was to examine the different effect of PVA-PEG binders on the surface roughness of Y-TZP zirconia. Methods: Twelve samples were divided into three treatment groups: 100% PVA, 100% PEG and 4% PVA-PEG added to Y-TZP powder at a ratio of 95:5 (wt.%). The mixture was pressed using a uniaxial pressing machine, sintered and measured: the data was then analyzed using one-way ANOVA and Post Hoc LSD. Results: The result of the ANOVA showed that there were significant differences in the surface roughness of the Y-TZP with three different binders (P<0.05). The average surface roughness of the three binders are as follows: PVA 100% (0.8025±0.23472), PEG 100% (1.2325±0.23866), 4% of PVA-PEG (1.3450±0.27695). The LSD showed that there was significant differences between PVA 100% and PEG 100% (P<0.05), PVA 100% and 4% PVA-PEG (P<0.05). There was no significant difference between PEG 100% and 4% PVA-PEG (P>0.05). Conclusion: 4% PVA-PEG binders combination has effects on the surface roughness of Y-TZP zirconia