• Pawarisa Thomvanich DDS.
• Prarom Salimee DDS., Ph.D.
• Mansuang Arksornnukit DDS., MSc., Ph.D.

Objective To investigate the strength of two all ceramic systems; In-Ceram and IPS Empress 2 at
different thicknesses of core and veneer ratio by means of biaxial flexural strength (BFS).

Material and methods Fifty disc samples of each all ceramic system, 15 mm. in diameter and
1.2 mm. in thickness, were fabricated following manufacturerûs recommendations. The samples
were divided into five groups (n=10 each) depending on different core and veneer thickness ratio
1:0, 2:1, 1:1, 1:2 and 0:1, respectively. All samples were subjected to BFS testing following
ISO 6872(1995) on the universal testing machine with crosshead speed of 1.0 mm/min.

Results The means + standard deviation of BFS of In-Ceram in group 1 - 5 were 433.1 + 68.4,
338.9 + 22.6, 294.4 + 15.2, 259.9 + 14.5 and 56.6 + 10.5 MPa, respectively. For IPS Empress 2 in
group 6 - 10 were 288.3 + 44.6, 246.3 + 28.2, 266.73 + 23.22, 226.6 + 2.4 and 68.6 + 5.5 MPa,
respectively. ANOVA and Tamhaneûs test revealed that the BFS of In-Ceram alone was significantly
higher than In-Ceram combined with veneer porcelain as well as the decreasing of BFS when the
thickness of core was decreased respectively (p<0.05). For IPS Empress 2, the BFS of IPS Empress 2
alone was not significantly different from IPS Empress 2 combined with veneer porcelain with any
core to veneer ratio as well as the BFS among the group combined with veneer porcelain (p>0.05).

Conclusion The core and veneer thickness ratio affects the BFS of In-Ceram but not for that of
IPS Empress 2.

(CU Dent J. 2007;30:141-56)