Internal line angles should be rounded to reduce stress concentration.

Internal line angles should be rounded to reduce stress concentration.

• A. True
• B. False
• C. Only for primary teeth
• D. Not important

Answer: (A)

Rounding internal line angles reduces stress concentration. Sharp corners act as notches where occlusal and functional forces concentrate, making cracks more likely to start and propagate in both tooth structure and restorative material. By smoothing these angles and increasing the radius of curvature, the forces are spread more evenly, lowering the local stress and improving resistance to fracture, especially under repetitive chewing. This principle applies broadly to tooth preparations and various restorative materials, and it also helps with better marginal adaptation and finishing.

Rounding internal line angles reduces stress concentration. Sharp corners act as notches where occlusal and functional forces concentrate, making cracks more likely to start and propagate in both tooth structure and restorative material. By smoothing these angles and increasing the radius of curvature, the forces are spread more evenly, lowering the local stress and improving resistance to fracture, especially under repetitive chewing. This principle applies broadly to tooth preparations and various restorative materials, and it also helps with better marginal adaptation and finishing.