Methods: Using the Straumann CARES CAD/CAM technology, two groups of implant abutments were fabricated for the Straumann implant system (n=30): zirconia abutments (Z), and titanium abutments (T). All abutments were generated from the same STL file. Standardized maxillary central incisor all-ceramic crowns (n=10) were fabricated for the zirconia and titanium abutments using the following systems: heat-pressable lithium disilicate glass-ceramic (IPS e.max Press) (Zp and Tp), machinable lithium disilicate glass-ceramic (IPS e.max CAD) (Zc and Tc), and zirconia based-ceramic (IPS e.max ZirCAD) (Zz and Tz). The crowns were cemented to the implant abutments with a resin luting agent (Multilink Implant). Afterwards, all specimens were tested for fracture resistance according to the ISO norm 14801. Data were analyzed using two-way ANOVA and Tukey post hoc tests (α = .05).
Results: The mean fracture load values were 363 ± 50.5 N for group Zp, 482.2 ± 58.4 N for group Tp, 392.9 ± 55.3 N for group Zc, 558.5 ± 35.2 N for group Tc, 340.3 ± 61.8 N for group Zz, and 495.9 ± 53.4 N for group Tz. ANOVA detected significant differences with respect to implant abutment, all-ceramic restoration, and the interaction of the two factors (p = .0001). Titanium abutments showed significantly higher fracture loads than zirconia abutments (p = .0001). Zirconia ceramic crowns presented the lowest fracture resistance, revealing significant differences with respect to the glass-ceramic crowns (p = .0001).
Conclusions: The type of abutment and all-ceramic crown system significantly influenced the strength of single-tooth implant-supported all-ceramic restorations. Titanium abutments restored with machinable lithium disilicate exhibited the highest fracture load values.