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Physical and mechanical properties of lithium disilicate ceramics subjected to simplified protocols of burning and surface characterization

Grant number: 20/12756-6
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): August 01, 2021
Effective date (End): July 31, 2022
Field of knowledge:Health Sciences - Dentistry - Dental Materials
Principal researcher:Fernanda de Carvalho Panzeri Pires de Souza
Grantee:Kaíssa da Cunha Lima
Home Institution: Faculdade de Odontologia de Ribeirão Preto (FORP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

In view of the current reality in restorative dentistry, it has become necessary to use materials and technologies that associate speed, aesthetics, durability, and naturalness. In this scenario, the CAD/CAM system has shown a fundamental role and has gained increasing clinical importance. Lithium disilicate ceramic blocks are one of the materials used in this method of manufacture because they have excellent characteristics and properties similar to the dental structure. However, the ceramic is pre-crystallized, requiring crystallization in high temperature; and because it is presented in monoblocks without stratification, they must undergo a process of pigmentation. This study aims to evaluate the effect of different protocols currently used for crystallization and pigmentation of lithium disilicate ceramics on roughness and flexural strength when subjected to aging. Bars (14 x 3 x 2 mm) of lithium disilicate ceramic (IPS e-max CAD, Ivoclar Vivadent) will be obtained and polished with 600, 1200, and 200-grit silicon carbide abrasive papers. Then, they will be randomly separated into two groups and subjected to different pigmentation and crystallization protocols: Group A (Single-step) - Layer of stain + Layer of glaze (Ivoclar Vivadent) + Crystallization. Group B (Multiple steps) - Crystallization + First layer of stain + Stain firing + Second layer of stain + Stain firing + Layer of Glaze + Glaze firing. After the described protocols, initial roughness (Surfcorder SE 1700, Kosakalab) readings will be performed. Then, the samples will be randomly separated into three groups, according to the aging method to which they will be submitted: Thermomechanical cycling (ER system, Eros, 1,200,000 cycles, 2 Hz of frequency and 5 °C/37 °C/55 °C, 30 s of immersion), Simulated toothbrushing (Pepsodent, MAVTEC, 73,000 cycles) and Control (without aging). New roughness readings will be taken and the samples will be submitted to the three-point flexural strength test (EMIC-DL, São José dos Pinhais, PR, Brazil). The data obtained will be submitted to statistical analysis according to the most appropriate statistical test. Finally, fractographic analysis of the samples will be performed by scanning electron microscopy (JSM 5410, Sony) for fracture surface analysis. (AU)

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