Porcelain jacket crown and metal ceramic crown are representative esthetic restorations for full veneer crowns. Genarally, Porcelain jacket crown is more esthetic and closer to natural tooth appearance. However it is brittle and subject especially to tensile stress.
Recently, a new reinforced porcelain for substructure, In-Ceram(VITA Zahnfabrik, Germany) was developed. This new reinforced porcelain is stronger than all other existing porcelain material and, can be widely used as one of the substructure materials.
This study compared the deformation of In-Ceram and metal substructures for the stress of 5, 7 9, 11, 13, 15kg forced to the each lingual slope with 30 degree angle. Metal substructure was casted with 3 kinds of metals precious(Degudent H, Degussa, Germany), semiprecious(Degupal U, Degussa, Germany), nonprecious(Rexillum IQ, Rexillium, U.S.A.).
Real time holographic interferometry was used for analysing the stress of these samples. This holographic interferometric analysis can evaluate the whole aspect of deformation without any morphological limitations and analyze finite deformation of samples by um and can be used on the idential samples not on computer model nor any other simulations.
The results obtained were as follows
1. When the load by Max. 15kg was added to the lingual slope of each samples, in all cases of In-Ceram, Degudent H, Degupal U, Rexillium III substructures, tensile deformation on the labial aspect and compressive deformation on the lingual aspect were increaced from the cervical to incisal region.
2. When the surface deformation of each substructure was compared , In-Ceram showed uniform stress distribution without any flexion of its surface. In the metal substructures, Rexillium III on the labial aspect, Degupal U on the lingual aspect showed uniform surface deformation without any flexion.
3. In the case of Degudent H, severe changes of fringe patterns appeared at the incisal resion of labial aspect & whole lingual aspect, therfore interpretation of interferogram was not possible in this study:
4. When compared the Max. deformation of labial surfaces, In-Ceram showed least deformation in the load of 5,7,9kg and also in the load of 11,13,15kg except Rexillium M. When compared the Max. deformation of lingual surfaces, In-Ceram showed greatest deformation in all loading condition.
5. In the respect of stress distribution, In-Ceram was not disadvantageous.
Holographic interferometry has a few methodological limit for the small dental restoration anlysis relatively great dynamic force condition. But as noncontact and nondestructive stress analyzing method, it is valuable to analyze ´finite deformation and more studies needed to apply it.
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