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Effect of endodontic instrumentation and restorative strategy on the fatigue and stress distribution of anterior teeth; and evaluation of cementation load on cement layer thickness and bonding between ceramic and dentin

Grant number: 19/20801-4
Support type:Regular Research Grants
Duration: September 01, 2020 - August 31, 2022
Field of knowledge:Health Sciences - Dentistry - Dental Materials
Principal researcher:Marina Amaral
Grantee:Marina Amaral
Home Institution: Pró-Reitoria de Pesquisa e Pós-Graduação. Universidade de Taubaté (UNITAU). Taubaté , SP, Brazil
Assoc. researchers: Kusai Baroudi ; Laís Regiane da Silva Concilio ; Luiz Felipe Valandro ; Susana María Salazar Marocho

Abstract

The aims of this study are (Part I) to evaluate the fatigue life of endodontically treated teeth using rotatory or reciprocating systems, restored with intraradicular fiber posts; (Parte II) to evaluate the fatigue life and stress distribution of endodontically treated teeth restored with (1) fiber post and full crown; (2) feldspathic ceramic post/core and full crown, or endocrowns, and the material for fabrication of endocrowns: lithium disilicate (LD) or polymer infiltrated ceramic (PIC); and (Part III) to evaluate the cementation load on the thickness of resin cement and on bond strength between dentin and lithium disilicate ceramic without and with storage. (Part I) bovine roots will be endodontically treated with rotatory or reciprocant system and included into acrylic resin base. Roots will receive the cementation of glass fiber posts/composite resin cores and will be subjected to mechanical fatigue (n=12, 2x106 cycles, 100 N). Two samples will be sectioned for evaluations of crack formation in intraradicular dentin and remaining samples will be subjected to load-to-failure. (Part II) The endodontic treatment with the best performance in Part I will be performed in 60 bovine roots. After treatment, roots will be restored with glass fiber post-composite resin core + full crown; feldspathic ceramic post-core + full crown or endocrown. Endocrowns will be fabricated into LD or PIC (n=15). Samples will be subjected to mechanical fatigue (n=15, 2x106 cycles, 100 N), with load application at lingual side of the teeth. Samples will be evaluated for fracture or cracks each 200 thousand cycles, and a survival plot will be generated. Remaining samples will be subjected to load-to-failure. A finite element analysis will be added, simulating the assemblies tested in 3D, and verifying the stress distribution to the root in each restoration strategy (Part III) A LD block (6 x 6 x 7 mm) will be adhesively cemented on the dentin of human molars, using a load for flowing of resin cement excess(n=6). The load will vary in 500 g, 1000 g or 3000 g. the assemblies will be sectioned into non-trimmed bar-shaped specimens, with adhesive interface of 1 mm2. Cement layer thickness will be measured in stereomicroscope in each sample. Half of the samples will be immediately tested into microtensile bond strength test and the other half will be stored into water during 180 days. Samples will be tested in microtensile bond strength test after storage. The correlation between cementation load and cement layer thickness and between cement layer thickness and bond strength before and after storage. (AU)

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