Which statement about rounding internal line angles is most accurate?

• A. Deepening the cavity is needed.
• B. Leaving sharp internal angles improves condensation.
• C. Increasing roughness of walls aids retention.
• D. Rounding internal line angles reduces stress concentrations and improves condensation.

Answer: (D)

Rounding internal line angles helps because it reduces stress concentrations in the set amalgam and makes condensation more effective. Sharp corners act as stress risers where biting forces concentrate, increasing the risk of microcracks and marginal breakdown over time. By smoothing these angles, the load is distributed more evenly, lowering the chance of fracture and leakage under functional use. At the same time, rounded corners give the condenser a smoother path to pack and adapt the material, reducing voids and improving the overall density and seal of the restoration. The result is a stronger, more durable amalgam that condenses more reliably.

Deepening the cavity changes geometry in ways that aren’t about stress distribution or condensation efficiency. Leaving sharp internal angles would preserve those stress risers and hinder condensation. Increasing roughness of walls isn’t the primary factor for condensation or reducing stress; it can actually complicate smooth adaptation of amalgam.