What was the idea of extension for prevention?

• A. Extending margins to obtain esthetic alignment
• B. Extending margins to include root surfaces regardless of cleanliness
• C. Placing the margins of restorations at areas that would be cleaned by the excursions of food during chewing
• D. Narrowing margins to reduce preparation

Answer: (C)

Extension for prevention is about shaping cavity margins so the patient can keep the area clean during normal function, using natural chewing and routine hygiene to remove plaque and prevent recurrent decay. The best way to achieve this is to place margins where food and saliva movement will naturally help cleanse the area, meaning margins lie where excursions of food during chewing will aid cleaning.

That’s why placing the restoration margins at locations that would be cleaned by the food bolus during chewing fits this concept best. It leverages the patient’s own functional cleansing to maintain the restoration and surrounding tooth.

The other ideas don’t fit as well: extending for esthetics focuses on appearance rather than maintainable cleanliness; including root surfaces regardless of cleanliness ignores whether those areas can be effectively cleaned by the patient; narrowing margins to reduce preparation moves away from preserving tooth structure through preventive design.