A loosening, that is to say a receding of the gum, can happen for traumatic reasons (poor brushing technique), or bacterial due to inflammation.
Healthy gums do not bleed, they are pale pink in appearance.
You should be aware of bleeding gums, which is a sign of inflammation.
At the beginning, the inflammation can be removed with a simple scaling.
In a more advanced stage, gingival pockets can develop, the inflammation starting to destroy some alveolar bone. Root planing is then necessary. It is a deep scaling to clean pockets, allowing the gum to attach to the tooth.
In very advanced cases, unfortunately the teeth can no longer be saved. Extractions should be carried out with the prosthetic reconstruction in mind.