The aim of this study was to produce composites suitable for CAD/CAM applications by high-temperature high-pressure polymerisation of resin-infiltrated glass-ceramic networks. The mechanical properties and the effect of sintering and catalyst were determined and compared to those of Paradigm (3M ESPE. USA).
Method:
The networks were made from vitroceramic powder (VITA Zahnfabrik. Germany), formed by slip casting. and were sintered or not. They were then silanized and infiltrated by UDMA with or without catalyst and polymerized at high pressure (300 MPa), high temperature (180°C) (HT/HP) to obtain composite blocks (CB).Samples for mechanical characterizations were cut from Paradigm and HT/HP CB. Flexural strength (σf), fracture toughness (KIC) and Vickers hardness (VHN)were determined and compared by one way ANOVA followed by Scheffe post hoc tests (a = 0.05). Fractured surfaces were characterized with a scanning electron microscope (SEM).
Result:
The results are summarized in the Table. All HT/HP CB had significantly (p<0.05) higher σf, KIC and VHN relative to Paradigm.Sintering the network significantly increased sfand VHN. The catalyst significantly decreased VHN.
Conclusion:
The results of this study suggest that HT/HP polymerization could be used to obtain dental composite blocks with superior mechanical properties suitable for CAD/CAM processing.
Table. Mean and standard deviation of mechanical properties*
Composite$ |
ESC |
ES |
EC |
E |
Paradigm |
Property |
|||||
sf (in MPa) |
305.2±53.7a |
288.3±39.6ab |
256.1±40.3c |
270.9±26.1bc |
138.2±24.3d |
Hardness (in HVN) |
137.8±5.1b |
144.6±3.2a |
122.7±7.6c |
136.5±5.5b |
114.8±4.3d |
KIC (in MPa·m1/2) |
2.74±0.49a |
2.77±0.65a |
3.09±0.97a |
2.91±0.98a |
0.78±0.21b |
$ ESC =HP/HT CB sintered and with catalyst; ES =HP/HT CB sintered and without catalyst; EC =HP/HT CB not sintered and with catalyst; E = HP/HT CB not sintered and without catalyst