Aim of the present study is the comparison of fracture-strength (FS) of posterior zirconia-based-FDPs and LS2-FDPs before and after aging.
Methods: 16 three-unit LS2-FDPs (e.max CAD, Ivoclar Vivadent) and 32 three-unit ZD-frameworks (Organic Zirkon, R+K CAD/CAM Technology) were fabricated by using computer-aided design and manufacturing (CAD/CAM). 16 ZD-frameworks were conventionally veneered (VZ) with low fusing veneering porcelain (IPS e.max Ceram, Ivoclar Vivadent) and 16 overpressed (OZ; IPS e.max ZirPress, Ivoclar Vivadent). All FDPs were cemented using glass ionomer cement (Ketac cem Aplicap, 3M Espe). 8 FDPs per group were artificially aged (mastication simulation: 1.2 mill. cyclesx50N, thermal cycling 10000x5°/55°C). FS of all FDPs were tested in an universal testing machine until fracturing at a test speed of v=1mm/min (Zwick 010, Zwick) and statistically analyzed (ANOVA, T-Test, p<0.05).
Results: FS of OZ before aging was 1609N±427N and after aging 1685N±480N, followed by VZ (1541N±438N/1557N±643N) and LS2 (1293N±237N/1131N±374N). After aging one LS2-abutment coping and 2 pontic-cusps fractured. 2 ZD-frameworks with OZ and 3 with VZ only showed superficial cracks. There were no significant differences between FS before and after aging, as well as between the different materials.
Conclusion: All FS were above 1000N before and 900N after aging. LS2-FDPs showed acceptable results compared to ZD based FDPs. Chipping of veneered porcelain on ZD-frameworks did not appear. Further clinical tests are required.