What is the ruling on filing down healthy teeth to fit a bridge over them for the purpose of bringing them closer together, and is this considered among the forbidden "Al-Washirah"?

It is permissible to bring teeth closer together and fill gaps with crowns if their spacing is a defect. However, if it is merely for beautification and enhancing appearance without an existing flaw, then it falls under prohibited cosmetic alterations. This is based on the Prophet's (peace be upon him) saying: "May Allah curse the women who tattoo and those who have themselves tattooed, those who pluck their eyebrows, and those who separate their teeth for beauty, altering Allah's creation."

Scholars have agreed that what is prohibited is that which is permanent and constitutes an alteration of Allah's creation. As for what is done for treatment or to correct a defect, there is no harm in it.