Degradation kinetics of high-translucency dental zirconias: Mechanical properties and in-depth analysis of phase transformation

Autor(es)

Conde Oliveira Prado, Pedro Henrique ^[1] ; Monteiro, Jaiane Bandoli ^[1] ; Bastos Campos, Tiago Moreira ^[2] ; Thim, Gilmar Patrocinio ^[2] ; de Melo, Renata Marques ^[3]

Afiliação do(s) autor(es)

^[1] Sao Paulo State Univ, Sci & Technol Inst, Dept Dent Mat & Prosthodont, UNESP, Sao Jose Dos Campos, SP - Brazil

^[2] Aeronaut Technol Inst ITA, Phys Dept, 50 Marechal Eduardo Gomes Sq, BR-12228900 Sao Jose Dos Campos, SP - Brazil

^[3] Sao Paulo State Univ, Inst Sci & Technol, Dept Dent Mat & Prosthodont, UNESP, Eng Francisco Jose Longo Ave 777, BR-12245000 Sao Paulo, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS; v. 102, FEB 2020.
• Citações Web of Science: 0

Resumo

This study aimed to evaluate the effects of low temperature degradation (LTD) on commercial dental zirconias (conventional and high-translucent - HT) with different microstructures, as well as on their mechanical properties and t-m phase transformation. The amount of monoclinic zirconia in different depths was quantified using X-ray diffraction (XRD) with different anode tubes (Cr, Co and Cu). XRD was also used to measure the residual stress of the materials at 0 h, 26 h and 140 h aging times. Vickers microhardness and biaxial flexural strength tests were performed. Data were subjected to two-way ANOVA and Tukey's post-hoc test, both with alpha = 0.05 for means comparisons. Weibull parameters were calculated and compared based on the overlapping of confidence intervals (CI = 95%). HT Zirconia presented smaller grain sizes and had a higher rate of t-m transformation over time. The microstructure of the conventional zirconia showed an expressive increase of the grain size and consequently greater morphological variation with the LTD. The non-aged samples (control) did not present any residual stress and the aged ones presented compression stress, All zirconia showed a residual stress increase with the increase of LTD time, but the conventional one showed a decrease after 140 h. HT zirconia showed no significant change in flexural strength over LTD time, but the conventional one showed a strength decrease after 140 h (681.78 +/- 121.18 MPa). Vickers hardness decreased for all zirconia samples after 26 h. The mechanics of LTD is significantly altered in different zirconia microstructures. Zirconias with smaller grains are more prone to t-m phase transformation, but present lower variation of residual stress, while larger grains zirconias have a lower surface area and therefore a more pronounced increase in stress over LTD time. Stress values close to the maximum compression stress generates ejection of the zirconia grains, producing defects and causing reduction of the compression stress and consequently decrease of flexural strength. (AU)

• Processo FAPESP: 16/03688-1 - Cinética de degradação de zircônias odontológicas com alta translucidez
• Beneficiário: Pedro Henrique Condé Oliveira Prado
• Modalidade de apoio: Bolsas no Brasil - Mestrado