Clinically called Tooth Mobility. It is the movement of a tooth within its socket greater than the normal physiological limit (0.25mm). It is classified from Grade I (slight) to Grade III (severe/vertical movement).
In adults, a loose tooth is a red flag. It usually signals advanced Periodontitis (bone loss), trauma (from grinding or a hit), or an abscess. Without treatment, the tooth will fall out.
A tooth that wiggles because the bone or ligaments holding it are damaged.
The most common cause is bone loss from gum disease. Heavy grinding (bruxism) can also "rock" a tooth loose.
How to fix a loose tooth?
Deep Cleaning: To heal gums and tighten the pocket.
Splinting: Bonding the loose tooth to stable neighbors.
Occlusal Adjustment: Grinding the bite so the tooth isn't hit as hard.