There are two main reasons why your gums may have receded:
- Toothbrush Abrasion- 'brushing too hard and wearing your gum away'- this is becoming increasingly common.
- Periodontal Disease-'true loss of bony support for your teeth'- unlike toothbrush abrasion, if this is the problem, it is more common to see calculus, plaque, gingivitis and, the loss of the interdental papillae (or gum in-between the teeth).
On occasions recession may be a result of orthodontic treatment, where a tooth (most commonly your lower incisor) has been moved too far forward in the bone and the gum in that area isn’t thick enough to cover the whole tooth.
One other possibility is that you have had an extraction in which a lot of bone has been lost. As the gum heals, it can recede around the teeth on either side. This is much more likely if you have had a surgical extraction
where it had been necessary for the dentist to raise a flap (pull your gum back) and remove some bone in order to help remove a difficult tooth.
If you have stitches, then you have probably had a surgical extraction - though sometimes, if that was a particular problem we might just pop stitches in, to help stop bleeding. (Hopefully your dentist would have told you if he was going to have to use that approach).
Toothbrush abrasion happens over a long period of time- as a result of continuously over brushing- either brushing for too long with a toothbrush that is too hard, using the wrong technique or some combination of all of these.
Recession develops over a long time, so if caught early by yourself or your dentist, simply learning to brush correctly can stop it from progressing. Because there is no strong enamel covering the exposed root surface, it is a lot softer and therefore wears more quickly than the surrounding tooth. This leads to 'classic notching'; an appearance where wedges appear to have been cut out of teeth.
If your recession is brushing related it would look like this… and more commonly affect your canines, probably as far as your first molar teeth. We seem to be able to put more force here and interestingly recession is often worse on the opposite side to whichever hand you brush with. For example, if you are left-handed it is common to see slightly more wear on the right hand side.