Original Research Article
Year: 2019 | Month: November | Volume: 9 | Issue: 11 | Pages: 159-167
Hardness and Fracture Toughness of Heat Pressable and Machinable Dental All- Ceramics
Abdullaziz M. Alzhrani1, Nadia Badr2
1Graduated students, Faculty of Dentistry, Umm Al-Qura University, KSA.
2Professor of Dental Biomaterials, Faculty of Oral & Dental Medicine, Cairo University Affiliated to Umm Al-Qura University, KSA
Corresponding Author: Nadia Badr
ABSTRACT
All-ceramic restorations are one of the most esthetically pleasing prosthodontics restorations. Because there is no metal to block light transmission, they can resemble natural tooth structure better in terms of color and translucency. Their chief disadvantages are high hardness that adversely affects the natural teeth and brittleness that affect susceptibility to fracture.
The aim of this study was to evaluate the hardness and calculate the fracture toughness of the most commonly used All-ceramic materials fabricated by different techniques and compared them with conventional feldspathic porcelain.
Heat pressing and CAD/CAM All-ceramic materials are used to fabricate eight disc-shaped samples of each material. The hardness of the samples was determined and their fracture toughness was calculated. Feldspathic porcelain fabricated by powder compaction technique served as control.
The results of hardness showed that Control Group A (sintered) exhibited slightly higher significant VHN value when compared to Group B (heat pressed). Group C (CAD/CAM) recorded the highest significant VHN hardness value. Regarding fracture toughness, Groups A and B showed comparable values with no significant difference. Again, Group C recorded the highest significant KC1 value when compared to A and B groups.
It could be concluded that the sintered dental porcelain has VHN and KC1 values comparable to those of heat pressable ceramic and this attributed to quitting of veneering procedure during preparation of in-vitro lab specimens. Meanwhile, CAD/CAM ceramic has the highest significant VHN as well as KC1 values in comparison to other groups.
Key words: MHardness, Fracture toughness, Heat pressable ceramics, Machinable ceramics.