There are many reasons gum tissue (or gingiva) bleeds upon brushing. The following list may help you determine why it’s happening to you:
- Poor or inadequate oral hygiene
- Lack of consistent brushing and flossing
- Lack of regular professional cleaning by a dentist or dental hygienist (every 3 to 6 months)
- Systemic diseases such as diabetes and cancer
- Medications that cause gum bleeding, such as high blood pressure meds
- Fillings, caps, or crowns that don't fit well and trap bacteria
- Orthodontic malocclusion — that is, misalignment, overlap, or overcrowding of the teeth.
- Active periodontal infection that causes pus and bleeding.
- A fractured tooth that allows bacteria to invade the area
As you can see, there are many reasons gums bleed. However, almost all these problems involve plaque or bacteria that mixes with food and settles around the gum line. In most cases, bleeding gums (whether because of poor oral hygiene or tooth positioning) are exacerbated by plaque.
My main advice is to see your dentist. General restorative dentists or specialists can take a set of dental X-rays and do a full examination to diagnose your problem. If you're cleaning your teeth thoroughly — brushing twice a day, flossing once a day, and using a mouth rinse — then your cleaning technique might be causing the bleeding, or you could have hardened plaque (calculus) on your teeth that should be cleaned out. A dental professional will advise you about regular cleaning appointments, and even special root-planing appointments that might be necessary to eliminate your gum bleeding.