Chantana Tulapornchai. The effect of thermocycling on biaxial flexural strength of dental ceramics/dentine systems . Master's Degree(Prosthodontics). Mahidol University. : Mahidol University, 2003.
The effect of thermocycling on biaxial flexural strength of dental ceramics/dentine systems
Abstract:
The purpose of this study was to evaluate the biaxial flexural strength of two
dental ceramics, Feldspathic porcelain (VMK95, Vita Zahnfabrik, Germany) and
Pressable ceramic (IPS Empress, Ivoclar, Liechtenstein) bonded to dentine with a resin
cement (VariolinkÒ II , Ivoclar, Liechtenstein), both before and after thermocycling.
Thirteen disc-specimens were prepared for each test group. The biaxial flexural
strengths (piston-on-3-ball) were determined with an universal testing machine at a
crosshead speed of 1 mm./min. until broken.
The mean biaxial flexural strength of Vita VMK95, both before and after
thermocycling, was not significantly different from that of IPS Empress (p>0.05).
The mean biaxial flexural strength of Vita VMK95 was not significantly
different, when comparing results before and after thermocycling (p>0.05), while that
of IPS Empress after thermocycling was significantly lower than before thermocycling
(p<0.05). Delamination at resin cement/dentine interface of the ceramics/dentine
systems occurred in the 24 of 26 Vita VMK95 specimens and 22 of 26 IPS Empress
specimens. After thermocycling, the number of delaminations increased by 2 of the 13
specimens in both Vita VMK95 and IPS Empress groups. Furthermore, the number of
delaminations that occurred in Vita VMK95 and IPS Empress, both before and after
thermocycling was not significantly different.
This study suggests that both Vita VMK 95 and IPS Empress for bonding to
dentine with a resin cement may be the materials of choice for patients. However, IPS
Empress was susceptible to thermocycling and showed a lower biaxial flexural
strength after thermocycling, but it was not significantly different from Vita VMK 95.