Mechanical properties of dental ceramics for fixed partial dentures

• Grant number: 06/03182-9
• Support Opportunities: Regular Research Grants
• Start date: September 01, 2006
• End date: February 28, 2009
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Paulo Francisco Cesar
• Grantee: Paulo Francisco Cesar
• Host Institution: Faculdade de Odontologia (FO). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The objectives of this project are: a) to analyze the microstructure of three ceramics used as core materials in partial fixed dentures - FPDs (yttrium oxide partially-stabilized tetragonal zirconia polycrystals, glass-infiltrated alumina/zirconia reinforced, and polycrystalline alumina) and correlate it with results obtained in the mechanical tests; b) to determine the stress corrosion coefficient (n) of these materials; c) to evaluate the effect of two types of aging (mechanical cycling and autoclave cycle) on the flexural strength of these materials; d) to evaluate the effect of the structure design (one, two or three layers) on their strength and mode of fracture; and e) to evaluate the effect of mechanical cycling on the fracture strength of FPDs built with the different core materials. All specimens will be produced using the CAD-CAM technology (Cerec inLab, Sirona), and some of them will be veneered with porcelain. Firing schedules will be carried out in the specific ovens of each ceramic system following manufacturers’ recommendations. The stress corrosion coefficient will be determined by means of the dynamic fatigue technique, breaking the specimens in a biaxial flexural strength device using 5 different constant stress rates. Two types of aging will be carried out: a) using a chewing simulator, and b) using autoclave cycles (134oC for 2 hours, in order to simulate 8 years in vivo at 37oC). Mechanical testing will be carried out using a “piston on three balls” apparatus. The FPDs will be loaded after luting them over steel master dies with the shape of prepared teeth. The load will be applied until fracture with a steel ball. Microstructural and fractographic analysis will be performed using SEM, OM, EDS, and XRD. (AU)