Effect of Zirconia and Alumina Fillers on the Microstructure and Mechanical Strength of Dental Glass Ionomer Cements
Júlio C. M. Souza1, 2, *, Joel B. Silva3, Andrea Aladim4, Oscar Carvalho1, Rubens M. Nascimento2, Filipe S. Silva1, Antonio E. Martinelli4, Bruno Henriques1, 2, 5, *
1 Center for Microelectromechanical Systems (CMEMS)-Uminho, Universidade do Minho, P-4800-058, Guimarães, Portugal
2 Post-Graduation Program in Dentistry (PPGO), Edif. CCS, School of Dentistry, Universidade Federal de Santa Catarina (UFSC), 88040-900, Florianópolis/SC, Brazil
3 School of Dentistry, School of Health Sciences (FCS), Universidade Fernando Pessoa (UFP), Porto, Portugal
4 Department of Materials Engineering, Universidade Federal do Rio Grande do Norte (UFRN), 59072-970, Natal/RN, Brazil
5 Ceramic and Composite Materials Research Group (CERMAT), Universidade Federal de Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil
Glass-ionomer cements perform a protective effect on the dentin-pulp complex considering the F ions release and chemical bonding to the dental structures. On the other hand, those materials have poor physic-mechanical properties in comparison with the restorative resin composite. The main aim of this work was to evaluate the influence of zirconia and/or alumina fillers on the microstructure and strength of a resin modified glass-ionomer cement after thermal cycling.
An in vitro experimental study was carried out on 9
groups (n = 10) of cylindrical samples (6 x 4 mm) made from resin
modified glass-ionomer (Vitremer, 3M, USA) with different contents of alumina
and/or zirconia fillers. A nano-hybrid resin composite was tested as a control
group. Samples were mechanically characterized by axial compressive tests and
electron scanning microscopy (SEM) coupled to energy dispersive X-ray
spectrophotometry (EDS), before and after thermal cycling. Thermal cycling
procedures were performed at 3000, 6000 and 10000 cycles in Fusayama´s
artificial saliva at 5 and 60 oC.
An improvement of compressive strength was noticed on glass-ionomer reinforced with alumina fillers in comparison with the commercial glass ionomer. SEM images revealed the morphology and distribution of alumina or zirconia in the microstructure of glass-ionomers. Also, defects such as cracks and pores were detected on the glass-ionomer cements. The materials tested were not affected by thermal cycling in artificial saliva.
Addition of inorganic particles at nano-scale such as alumina can increase the mechanical properties of glass-ionomer cements. However, the presence of cracks and pores present in glass-ionomer can negatively affect the mechanical properties of the material because they are areas of stress concentration.
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* Address correspondence to these authors at the Post-Graduation Program in Dentistry (PPGO),
School of Dentistry
Universidade Federal de Santa Catarina (UFSC)
Campus Trindade, Edif. CCS, 88040-900