Healthy gums are firm and pale pink and fitted tightly around the teeth. Signs and symptoms of gingivitis include:

• Swollen or puffy gums
• Dusky red or dark red gums
• Gums that bleed easily when you brush or floss
• Bad breath
• Receding gums
• Tender gums

The most common cause of gingivitis is poor oral hygiene that encourages plaque to form on teeth, causing inflammation of the surrounding gum tissues. Here's how plaque can lead to gingivitis:

• Plaque forms on your teeth. Plaque is an invisible, sticky film composed mainly of bacteria that forms on your teeth when starches and sugars in food interact with bacteria normally found in your mouth. Plaque requires daily removal because it re-forms quickly.
• Plaque turns into tartar. Plaque that stays on your teeth can harden under your gumline into tartar (calculus), which collects bacteria. Tartar makes plaque more difficult to remove, creates a protective shield for bacteria and causes irritation along the gumline. You need professional dental cleaning to remove tartar.
• Gingiva become inflamed (gingivitis). The longer that plaque and tartar remain on your teeth, the more they irritate the gingiva, the part of your gum around the base of your teeth, causing inflammation. In time, your gums become swollen and bleed easily. Tooth decay (dental caries) also may result. If not treated, gingivitis can advance to periodontitis and eventual tooth loss.

Gingivitis is common, and anyone can develop it. Factors that can increase your risk of gingivitis include:

• Poor oral care habits
• Smoking or chewing tobacco
• Older age
• Dry mouth
• Poor nutrition, including vitamin C deficiency
• Dental restorations that don't fit properly or crooked teeth that are difficult to clean
• Conditions that decrease immunity such as leukemia, HIV/AIDS or cancer treatment
• Certain drugs, such as phenytoin (Dilantin, Phenytek) for epileptic seizures, and some calcium channel blockers, used for angina, high blood pressure and other conditions
• Hormonal changes, such as those related to pregnancy, menstrual cycle or use of birth control pills
• Genetics
• Medical conditions such as certain viral and fungal infections

Untreated gingivitis can progress to gum disease that spreads to underlying tissue and bone (periodontitis), a much more serious condition that can lead to tooth loss.

Chronic gingiva inflammation has been thought to be associated with some systemic diseases such as respiratory disease, diabetes, coronary artery disease, stroke and rheumatoid arthritis. Some research suggests that the bacteria responsible for periodontitis can enter your bloodstream through gum tissue, possibly affecting your heart, lungs and other parts of your body. But more studies are needed to confirm a link.

Trench mouth, also known as necrotizing ulcerative gingivitis (NUG), is a severe form of gingivitis that causes painful, infected, bleeding gums and ulcerations. Trench mouth is rare today in developed nations, though it's common in developing countries that have poor nutrition and poor living conditions.