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The aim of this study was to investigate the effect of post-machining sintering on marginal and internal fit of CAD/CAMfabricated zirconia frameworks. Single crown copings (A: abutment), three-unit bridge frameworks (APA, P: pontic), four-unit bridge frameworks (APPA), and five-unit bridge frameworks (A1 P1 A2 P2 A3) were fabricated with raw-stage zirconia blanks using a commercial CAD/CAM system (KATANA®, Noritake Dental Supply Co. Ltd., Aichi, Japan). Crown copings and frameworks were cemented to their respective master abutment models, and thickness of the cement layer was measured at specific measuring points. Marginal and internal fit of both APA and APPA were within clinical acceptance. However, the marginal gap and thickness of the cement layer on the axial surface of the pontic side of APA and APPA were slightly higher than those of the non-pontic side. As for the marginal gap of A1 P1 A2 P2 A3 framework, it was superior to those of APA and APPA because the center abutment supported the framework to prevent distortion.

To increase the bond strength of CAD/CAM-fabricated, leucite-reinforced glass ceramics with a resin cement, the effects of the following were investigated: surface modification by tribochemical (TBC) treatment, followed by combined application of a silane coupling agent and a functional monomer as a primer. Bond strength was evaluated by a shear bond test. It was found that a silane coupling agent was useful for all the surfaces, particularly for the TBC-treated surface. This was because of the presence of a silica layer on the modified surface. The combination of a silane coupling agent and a functional monomer on the TBC surface allowed marked improvement in bonding, whereby the bonding endured 20,000 cycles of thermal cycling. Therefore, TBC treatment in combination with a silane coupling agent and a functional monomer as a primer substantially increased the bond strength of CAD/CAM-fabricated glass ceramics with resin cement, if the treatment conditions were appropriate.

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