Fracture Toughness of All-Ceramic Crowns Luted with Different Cements.

Introduction: Computer-aided Design (CAD) computer-aided manufacturing (CAM) technology, all-ceramic systems, and high-strength ceramic materials have become integral parts of modern dentistry and laboratory technology.[1] Furthermore, metal-based crowns have other disadvantages, such as galvanic reaction, and the metal underlying the veneers porcelain can show through as a dark line.[2,3]
Several new all-ceramic systems, which offer comparable stability to porcelain-fused-to-metal (PFM) restorations, good esthetics, and simplified fabrication procedures, have been introduced. Recently, new dental materials and techniques have been introduced to fabricate esthetic ceramic restorations with improved strength and marginal adaptation.[4] This becomes more important for posterior areas, where forces are much higher than for the anterior region and can reach 522 N in the average person.[5,6]
In order to address to this problem, a new ceramic system with higher fracture strength (IPS e-max CAD, Ivoclar Vivadent) was launched recently on the marked.[7]
In addition to the fracture resistance of dental prostheses, luting materials are also important for the longevity of dental restorative materials.[8] The ability of the resin cement to provide a greater critical load for all-ceramic crowns than for conventional cements has been evaluated previously, and the fracture resistance was improved when the crowns were cemented with resin cement.[9]
Clinical studies have demonstrated excellent long-term clinical success of high-strength all-ceramic crowns (Procera Alunima, Nobel Biocare) using conventional cementation methods.[10,11] High success rate reposted in these studies indicate that the inherent fracture strength and fracture toughness of high-strength ceramic materials may allow for conventional cementation of full-coverage all-ceramic restorations.
Conventional cementation with zinc phosphate cement, glass ionomer, or resin-modifieed glass ionomer is simple and not as technique-sensitive or time consuming as adhesive bonding with composite resin luting agents and multiple-step priming agents.[1] Nowadays, a recently developed universal adhesive resin cement (SpeedCEM, Ivoclar/Vivadent) is used like a conventional cement, and it does not require application of additional bonding agents to the tooth or restoration.
As discussed previously, studies have demonstrated the possibility of conventional cementation techniques when using all-ceramic crowns with high-strength core material, but current guide-lines for an all-ceramic crown without reinforced core material recommend the use of adhesive cementation in order to provide the proper support for the restorations. It is required margins finishing at supra-gingival level in order to allow proper isolation and this is one of the limitations of the use of such crowns. When the margins are finished at sub-gingival level and moisture control is a factor, a porcelain-fused to metal (PFM) is indicated.
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