Dental According to ADA specification of toothbrush width of brush head should be: A 5/8-3/8inches. B 5/16-3/8inches. C 5/8-3/16inches. D 5/16-3/16inches. 💡 Explanation According to ADA specification of toothbrush width of brush head should be: ✓ Correct Answer: B. 5/16-3/8inches.