An avulsed upper right central incisor is brought in by an 8-year-old. The tooth has an OPEN apex and was stored in Hank's Balanced Salt Solution (HBSS). What is another appropriate storage medium?

Correct answer: C. Milk (cold whole milk is the best readily available storage medium — maintains PDL cell viability)

• A. Dry storage kills PDL cells within 15-30 minutes — never recommended.
• B. Tap water is hypotonic and rapidly kills PDL cells through osmotic lysis — worst storage medium.
• C. Correct. For avulsed tooth storage (to maintain PDL cell viability for replantation): Best: HBSS (Hank's Balanced Salt Solution, e.g., 'Save-A-Tooth' kit) → maintains cells up to 24 hours. Second best: COLD WHOLE MILK → isotonic, nutrients, maintains viability up to 30-60 minutes. Third: Saline → isotonic but no nutrients, short viability. Never: DRY STORAGE (kills PDL cells within minutes), TAP WATER (hypotonic, causes cell lysis).
• D. Saline is acceptable but inferior to milk for storage viability.