Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain it seems that you have gingival recession in general known as Gum recession and as it is on one tooth it is most probably due to gum infection and as the lower teeth are more prone to accumulate more of plaque and tartar due to its location, therefore they are more prone to get infected and in your case also infection of gums leads to recession as the gum loses its attachment from its tooth. Depo provera injection that contains Medroxyprogesterone as active ingredient is a Hormone Replacement therapy and it does not seems to be a cause for gum recession and that too it is not generalized and confined to a single tooth.. I would suggest you to consult an Oral Physician and get evaluated and a thorough clinical evaluation can help in diagnosis and treated accordingly.. You can be advised scaling of teeth and gums followed by gum paint application and gargle with antiseptic mouthwash gargles to prevent further damage to gums as well as improve gum health.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.