Abstract :
The aim of this research is to study the fracture resistance of metal-ceramic crowns that have a ceramic margin in comparison with metal-ceramic crowns (Metal feather edge). The research sample consisted of 3 groups: The first group (G1) (n=10) is metal-ceramic crowns (Metal feather edge). The second group (G2) (n=10) is metal-ceramic crowns with ceramic margins 1 mm from the axial cervical line angle towards the middle of the mesial and distal surfaces. The third group (G3) (n=10) metal-ceramic crowns with ceramic margins 2 mm from the axial cervical line angle towards the middle of the mesial and distal surfaces. Prepared upper central was designed on Meshmixar program to get metal dies, then the metal framework for crowns was designed on Exocad program and the designs were printed with Direct Laser Metal Sintering (DLMS). The porcelain Ips d.SIGN – Ivoclar Vivadent was used and built using direct lift technique. The crown's resistance has been tasted using mechanical test machine by applying load on the palatal surface of the crowns 135° with tooth axis till the failure occurs within the porcelain. There was a significant difference (P≤0.05) between G1, G3 groups and between G2, G3 groups while there was no significant difference (P≥0.05) between G1, G2 groups. It was concluded from this study that the more the cut increased from the metal structure, the more the force needed to cause the failure within the metal-ceramic crowns decreased.
