Effect of fiber addition on slow crack growth of a dental porcelain

Author(s)

de Araujo, Maico Dutra ^[1] ; de Paula Miranda, Ranulfo Benedito ^[1] ; Fredericci, Catia ^[2] ; Yoshimura, Humberto Naoyuki ^[3] ; Cesar, Paulo Francisco ^[1]

Affiliation

^[1] Univ Sao Paulo, Fac Odontol, Dept Biomat & Biol Oral, BR-05508900 Sao Paulo, SP - Brazil

^[2] Inst Pesquisas Tecnol, Sao Paulo, SP - Brazil

^[3] Univ Fed ABC, Ctr Engn Modelagem & Ciencias Sociais Aplicadas, Santo Andre, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS; v. 44, p. 85-95, APR 2015.
• Web of Science Citations: 1

Abstract

Aims: To evaluate the effect of the processing method (conventional sintering, S, and heat-pressing, HP) and addition of potassium titanate fibers, PTF, on the microstructure, mechanical properties (flexural strength, sigma(f), Weibull parameters, m and sigma(5%)), slow crack growth parameters n (stress corrosion susceptibility coefficient), and optical properties (translucency parameter, TP, and opalescence index, 01) of a feldsphatic dental porcelain. Methods: Disks (n=240, O12 x 1 mm) of porcelain (Vintage-Halo, Shofu) were produced using S and HP methods with and without addition of 10 wt% (conventional sintering) or 5 wt% (heat-pressing) of PTF. For the S method, porcelain was sintered in a conventional furnace. In the HP technique, refractory molds were produced by lost wax technique. The porcelain slurry was dry-pressed (3 t/30 s) to form a cylinder with 12 mm (diameter) and 20 mm (height), which was heat-pressed for 5 min/3.5 bar into the mold. Specimens were tested for biaxial flexural strength in artificial saliva at 37 degrees C. Weibull analysis was used to determine m and sigma(5%). Slow crack growth (SCG) parameters were determined by the dynamic fatigue test, and specimens were tested in biaxial flexure at five stress rates: 10(-2), 10(-1), 10(0), 10(1) and 10(2) MPa/s (n=10), immersed in artificial saliva at 37 degrees C. Parameter n was calculated and statistically analyzed according to ASTM F394-78. Optical properties were determined in a spectrophotometer in the diffuse reflectance mode. Results: The highest n value was obtained by the combination of heat-pressing with fiber addition (37.1) and this value was significantly higher than those obtained by both sintered groups (26.2 for control group and 27.7 for sintered with fiber). Although heat-pressing alone also resulted in higher n values compared to the sintered groups, there were no significant differences among them. Fiber addition had no effect on mechanical strength, but it resulted in decreased TP values and increased OI values for both processing methods. Heat-pressing alone was able to reduce the porosity level of the porcelain. Conclusions: Addition of PTF combined with heat-pressing can reduce strength degradation of a dental porcelain compared to sintered materials with or without fibers. Heat-pressing (HP) alone should be considered as a good alternative for clinical cases where high translucency is required. (C) 2014 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 09/00100-0 - Optical properties and microstructure of dental ceramics
• Grantee: Paulo Francisco Cesar
• Support Opportunities: Regular Research Grants