The preferred astringent agent for achieving hemostasis with minimal tissue toxicity is Ferric sulfate (15-20%).

- Hemostasis is a critical step in many dental and surgical procedures to control bleeding and provide a clear operative field.
- Astringent agents are used to constrict blood vessels and protein precipitation, which helps in stopping bleeding.
- Among the commonly used agents — Aluminum chloride, Zinc chloride, Ferric sulfate, and Tannic acid — the selection depends on efficacy and tissue compatibility.
- Aluminum chloride (20-25%) is effective but can cause moderate tissue irritation and discoloration.
- Zinc chloride is a potent astringent but has a higher risk of tissue damage and necrosis due to its aggressive nature.
- Tannic acid is a natural astringent but has limited hemostatic potency and is less frequently used in clinical practice today.
- Ferric sulfate (15-20%) offers a rapid and effective hemostatic action with minimal tissue toxicity and less postoperative inflammation, making it the preferred agent.
- It acts by forming a thin coagulum sealing capillary walls without causing extensive tissue damage.

Therefore, Ferric sulfate (15-20%) is the preferred choice because it balances hemostatic efficacy with biocompatibility and minimal adverse tissue effects.

Reference: Textbook of Oral Medicine and Surgery, Volume 1, Chapter on Hemostasis and Astringents, Page 152