Optimizing Strength in Full-Arch Restorations: Height Matters for Cantilevered Zirconia on Titanium Frameworks-An In Vitro Study.

PURPOSE: To investigate the compressive fracture resistance of zirconia superstructures with different occlusal-cervical heights (2, 4, and 6 mm) when bonded to rigid titanium (Ti) frameworks with cantilever extensions.

MATERIALS AND

METHODS

A total of 30 zirconia superstructures-Zirlux Transitions partially stabilized zirconia (35 × 10 mm; height: 2, 4, or 6 mm)-were bonded to standardized inverted T-shaped Ti frameworks (Grade 5, 35 × 10 × 6 mm) featuring a 10-mm cantilever. Each assembly was screw-retained on implant analogs and subjected to vertical load until failure using a universal testing machine (1 mm/minute crosshead speed, 3-mm hemispherical tip). Fracture characteristics were examined under 50× magnification. The study was limited to static vertical loading and did not assess fatigue or lateral forces.

RESULTS

Mean fracture loads were 2,809.45 ± 78.43 N (2 mm), 2,895.60 ± 104.49 N (4 mm), and 2,892.30 ± 76.54 N (6 mm), with no statistically significant differences (P > .05). The most frequent failure involved fracture of the prosthetic screw distal to the loading point. Two specimens in the 2-mm group showed superficial cracks, but no zirconia fractures or framework deformation occurred in any group.

CONCLUSIONS

Zirconia superstructures with reduced height (2 mm) demonstrated compressive strength comparable to thicker designs when supported by a rigid Ti framework. These findings support the potential clinical use of such restorations in space-limited scenarios. However, further studies involving fatigue and multidirectional loading are necessary to validate clinical relevance.