The number of specimens in a furnace affects the biaxial flexural strength of veneered zirconia specimens after sintering

Abstract

This study evaluated the effect of the number of specimens in a furnace during the firing of porcelain-zirconia (Y-TZP) discs on their biaxial flexural strength. Eighty bilayer disc-shaped specimens (∅: 15mm; thickness: 1.2 mm, ISO 6872) of zirconia (Vita In-Ceram YZ Cubes/Vita) and porcelain (Vita VM9) ceramics, were prepared and divided into four groups (n = 20) according to the number of specimens in a furnace for each porcelain sintering: G1- one disc/20 sintering cycles.; G2 – two discs/10 sintering cycles.; G5-five discs/4 sintering cycles; and G10 – ten discs/2 sintering cycles. Then, the specimens were submitted to biaxial flexure testing (BFS) (1 mm/min, water). The data (MPa) were analyzed with Kruskal-Wallis test followed by the Dunn's post hoc analysis at a 95% level of confidence (α = 0.05). Kruskal-Wallis showed that the number of samples in the furnace affected flexural strength (p < 0.0001). The highest BFS was observed for the G5 (132.3 MPa)^A, which was significantly higher than G1 (53.6 MPa)^B. No significant difference was observed for the Weibull moduli and characteristic strength among the groups. In terms of flexural strength, approximately five specimens at a time can be placed in a furnace for sintering.

Keywords:

• Porcelain firing
• heat distribution
• bilayer
• flexural strength
• zirconia
• dental ceramics

Disclosure statement

No potential conflict of interest was reported by the author(s).