A 62-year-old man with bruxism is having tooth #19 restored with a newly patented zirconia. A flexural strain versus flexural strength diagram compares the new and old zirconia. What can be inferred from the diagram?

Correct answer: B. New zirconia is a less brittle material than old zirconia

• A. No statistics are presented at all — no p-value, no confidence interval, no error bars, no sample size. You cannot claim a difference is non-significant from a figure that reports no significance testing. And visually the two curves clearly diverge.
• B. CORRECT. Brittleness is the tendency to fracture with little deformation beforehand. The new zirconia curve continues to strain to about 3.0% and carries load out to roughly 450 MPa, while the old zirconia fails at around 2.25% strain and 350 MPa. Deforming further before failure and absorbing more energy along the way is precisely what it means to be LESS BRITTLE (tougher). That is a direct, legitimate reading of the curves.
• C. This overreaches. The diagram reports an in-vitro mechanical property under controlled loading. Long-term clinical success depends on cement selection, occlusal scheme, preparation design, parafunction, oral moisture and thermal cycling — none of which a laboratory stress–strain curve measures. Bench strength does not equal clinical longevity.
• D. The word 'predictable' is a clinical outcome claim, and no clinical outcome data appear anywhere in this figure. It also asserts something about both materials that the graph cannot support.

Note: How to read these curves: the SLOPE of the initial linear portion is the elastic modulus (stiffness); the PEAK is ultimate strength; the strain at failure indicates ductility; and the AREA UNDER the curve is toughness — total energy absorbed before fracture. Brittle materials have a steep slope and a short curve. Clinically relevant for this patient: bruxism argues for monolithic full-contour zirconia and a night guard.