Objective: To evaluate the effect of different surface treatments on the retention between zirconia crowns and tooth structure after in vitro aging. Materials and methods: Human third molars (n = 44) received crown preparations and CAD/CAM zirconia crowns were manufactured. Specimens were divided into two groups: no aging, control (NAC, n = 11) or aging (A, n = 33). NAC were bonded with universal adhesive (UA). Aged specimens were divided into three subgroups (n = 11) according to surface treatment: Control: no abrasion + UA; Alumina: alumina abrasion + UA; Silica: tribochemical silica coating + UA. The crowns were cemented with dual-cure resin cement. Specimens in group A were aged by a combination of mechanical, thermal, and pH cycling. Retention strength values were obtained by tensile tests and results were analyzed by one-way analysis of variance (ANOVA) and Tukey test (P < .05). Results: Aging decreased the retention strength in control specimens (P < .001). Surface treatment improved the retention strength of aged specimens (P < .001), with similar results between alumina and tribochemical silica coating. Conclusion: The chemical interaction between the universal bonding system and zirconia's surface was not sufficient to withstand artificial aging. Tribochemical silica coating did not promote additional retention in comparison to alumina blasting. Clinical significance: The long-term retention of translucent zirconia crowns to tooth structure using phosphate-based materials is improved by means of mechanical surface treatments such as alumina blasting and tribochemical silica coating. K E Y W O R D S airborne particle abrasion, aging, translucent zirconia, universal adhesive, zirconia crown 1 | INTRODUCTION Polycrystalline tetragonal zirconia stabilized with 3 mol% of yttria (3Y-TZP) has been largely used for the restoration of heavily destroyed teeth. 1 In spite of having excellent mechanical properties and biocompatibility, 3Y-TZP exhibits a high level of opacity and needs to be veneered with porcelain to mimic the optical properties of the tooth structure. 2,3 One of the strategies to enhance translucency of zirconia is to increase the yttria content to 4 mol% (4Y-PSZ) or 5 mol % (5Y-PSZ), resulting in partially stabilized materials. 4 The higher yttria content introduces an optically isotropic cubic phase into the crystalline phase composition of zirconia, which minimizes opacity and makes zirconia more suitable for monolithic anterior restorations. 4-6

The aim of the study is to evaluate the influence of different thicknesses of bleaching gel on the efficacy of tooth bleaching. Seventy specimens in the form of standardized bovine enamel-dentin blocks were prepared, sequentially polished, and randomly divided into three groups, according to the bleaching agent used: CT (control-no bleaching; n=10) – Artificial saliva; HP (n=30) – 38% Hydrogen Peroxide and CP (n=30) – 10% Carbamide Peroxide. The HP and CP groups were divided into 3 subgroups according to the bleaching gel thickness: A – 0.5mm; B – 1.0mm and C – 2.0mm. The color was measured before and after (24 hours) of the bleaching treatment. Color difference (DE) and translucency (TP) were calculated. ΔE variations were statistically analyzed with two-way ANOVA. Translucency values were analyzed with the Student's T-test (p£0.05). Regarding, the DE and TP values, there were no significant differences between groups (p³0.05) for different thicknesses of bleaching gel. The thickness of the bleaching gel did not influence the effectiveness of bleaching, regardless of the bleaching agent used.

Introdução: Embora as restaurações diretas tenham boas propriedades mecânicas, quando utilizadas sem indicação em cavidades amplas ficam susceptíveis a fratura e ao desgaste. Nesses casos, o ideal é que sejam feitas restaurações indiretas do tipo inlay ou onlay, entretanto o custo da etapa laboratorial das restaurações indiretas limitam a realização dessa técnica. Para tentar minimizar o custo e melhorar as propriedades da técnica direta existe as restaurações semidiretas. Objetivo: Descrever na forma de um caso clínico a confecção de uma restauração do tipo onlay pela técnica semidireta. Relato de caso: Paciente compareceu a clínica odontológica para substituição de restauração insatisfatória no elemento 46. O tratamento de escolha foi substituição da restauração de resina composta por uma restauração do tipo onlay. A técnica semidireta foi eleita para confecção da restauração, uma vez que agrega as vantagens das técnicas direta e indireta, com um menor custo operacional e tempo de execução. Considerações finais: a técnica semidireta é uma opção de tratamento para restaurações em dentes posteriores, com menor custo para o paciente e pode ser seguramente indicada em cavidades amplas.

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