1. Broken, misaligned or dislodged restorations
When biting down on something hard, during a habit of clenching the teeth, or when the restorations are very old, they tend to become damaged or mismatched.
2. Gum disease
It is known as gingivitis and in more advanced stages as periodontitis. This disease is the main cause of dental loss worldwide since it degenerates the bone that supports the teeth such that they become loose.