Objective The use of a 30 µm alumina–silica coated particle sand (CoJet™ Sand, 3M Espe), has shown to enhance the adhesion of resin cements to Y-TZP. The question is whether or not sandblasting 30 µm particles does negatively affect the fatigue limit (S–N curves) and the cumulative survival of Y-TZP ceramics. Method Four zirconia materials tested were: Zeno (ZW) (Wieland), Everest ZS (KV) (KaVo), Lava white (LV) and Lava colored (LVB) (3M Espe). Fatigue testing (S–N) was performed on 66 bar of 3 mm × 5 mm × 40 mm with beveled edges for each zirconia material provided by the manufacturers. One half of the specimens were CoJet sandblasted in the middle of the tensile side on a surface of 5 mm × 6 mm. Cyclic fatigue (N = 30/group) (sinusoidal loading/unloading at 10 Hz between 10% and 100% load) was performed in 3-point-bending in a water tank. Stress levels were lowered from the initial static value (average of N = 3) until surviving 1 million cycles. Fatigue limits were determined from trend lines. Kaplan–Meier survival analysis was performed to determine the failure stress at the median percentile survival level for 1 million of cycles before and after sandblasting. The statistical analyses used the log-rank test. Characterization of the critical flaw was performed by SEM for the majority of the failed specimens. Results The fatigue limits “as received” (ctr) were: LV = 720 MPa, LVB = 600 MPa, KV = 560 MPa, ZW = 470 MPa. The fatigue limits “after CoJet sandblasting” were: LV = 840 MPa, LVB = 788 MPa, KV = 645 MPa, ZW = 540 MPa. The increase in fatigue limit after sandblasting was 15% for Zeno (ZW) and Everest (KV), 17% for Lava (LV) and 31% for Lava colored (LVB). The KM median survival stresses in MPa were: ZW(ctr) = 549 (543–555), ZW(s) = 587 (545–629), KV(ctr) = 593 (579–607), KV(s) = 676 (655–697), LVB(ctr) = 635 (578–692), LVB(s) = 809 (787–831), LV(ctr) = 743 (729–757), LV(s) = 908 (840–976). Log-rank tests were significantly different (p < 0.001) for all sandblasted groups vs. the “as received” except for Zeno (Wieland) (p = 0.295). Failures started from both intrinsic and machined flaws. Significance 30 µm particle sandblasting did significantly improve the fatigue behavior of three out of four Y-TZP ceramic materials and can therefore be recommended for adhesive cementation procedures. This study was supported in part by grants from the Swiss Society for Reconstructive Dentistry (SSRD) and 3M Espe.

In the ternary system TiB2-TiC-SiC, the different two-phase composites, TiC-TiB=, SiC-TiB2 and SiC-TiC exhibit remarkable mechanical properties in regard with the single phase ceramics. The evolution of those properties, i.e. modulus of rupture ~f, fracture toughness Klc, critical flaw size ac, hardness Hv, coefficient of thermal expansion 0~ and electrical resistivity 9, over the complete ternary diagram was investigated.A methodology of research using optimal design was used to minimize the number of composites to be elaborated. In this study, 16 samples were sufficient to empirically determine a provisional mathematical model for each property. A model, then, enables the plot of isoresponse curves in the ternary diagram. The samples were hot pressed and the optimal hot-pressing cycles were determined using densification rates against temperature curves. The concordance between computed and experimental values is excellent, e.g. a sample containing 20mo1% of TiB2, 55mo1% of TiC and 25mo1% of SiC has ~fexp= 1080MPa, O-fcom p = 1070 MPa; Klcex p = 6.7 MPam l/z, Klccorn p = 6 MPa mr/2; Hvex p = 16.6 GPa, Hvcomp = 17.3 GPa; and Pexp = 57.4 gf~ cm, 9comp = 55 I~s cm.Although titanium diboride does not react with silicon carbide, a strong interface bond is developed between titanium diboride and titanium carbide, and between titanium carbide and silicon carbide. This explains the bend strength evolution in the ternary system, and more particularly the fact that, in the area o-f > 1000 MPa and Klc > 6 MPam 1/2, to high SiC contents correspond to low TiB2 contents and conversely. The relevant microstructures will be discussed.

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