Gum infections are caused by bacteria in dental plaque triggering an inflammatory response in your gum tissue. Nearly half of all adults aged 30 and older have some form of periodontal disease, according to the CDC. But bacteria alone don’t tell the full story. Smoking, hormonal changes, genetics, certain medications, and chronic conditions like diabetes all influence whether plaque buildup tips into a full-blown infection.
How Bacteria Start the Process
Your mouth naturally contains hundreds of bacterial species. When you eat, bacteria combine with food particles and saliva to form a sticky film called plaque on your teeth and along the gumline. In healthy mouths, regular brushing and flossing remove most of this plaque before it causes problems. When plaque stays put, the bacterial community shifts. Early plaque is mostly harmless bacteria, but over time it becomes dominated by more aggressive species, including rod-shaped and spiral organisms that are strongly linked to severe gum disease.
Your immune system detects these bacteria and sends white blood cells to fight them off. That immune response is what causes the redness, swelling, and bleeding you notice when brushing. This early stage is gingivitis, and it’s reversible. If the bacteria remain, though, the ongoing inflammation starts breaking down the tissue and bone that hold your teeth in place. That deeper, more destructive stage is periodontitis.
Plaque that isn’t removed can harden into tartar (also called calculus) in as little as four to eight hours, though the average time is 10 to 12 days. Once plaque mineralizes into tartar, you can’t brush it away at home. It requires professional cleaning. Tartar below the gumline creates a rough surface where even more bacteria accumulate, pushing the infection deeper.
Pocket Depth and What It Means
Dentists measure gum health by checking the depth of the space between your gums and teeth using a small probe. Healthy gums have pockets between 1 and 3 millimeters deep. Pockets deeper than 4 millimeters suggest periodontitis has set in. Once pockets exceed 5 millimeters, normal brushing and flossing can no longer reach the bacteria trapped inside, and the infection tends to worsen without professional treatment.
Why Smoking Raises Your Risk
Smoking is one of the strongest risk factors for gum infection, and it works in a deceptive way. Nicotine constricts blood vessels in the gums, reducing blood flow, swelling, and redness. That means smokers often show less bleeding and fewer visible signs of inflammation, even when significant damage is happening underneath. The reduced blood flow also weakens your gums’ ability to fight bacteria and heal. Many smokers don’t realize they have gum disease until it’s already advanced, precisely because the early warning signs are suppressed.
Diabetes and Gum Disease Feed Each Other
Diabetes and gum infection have a two-way relationship. High blood sugar damages small blood vessels throughout the body, including those in your gums. It also impairs how your immune cells respond to bacteria, slowing wound healing and making gum tissue more vulnerable to infection. People with poorly controlled diabetes show higher levels of inflammatory molecules in their gum tissue, which accelerates the breakdown of supporting bone and tissue.
The relationship works in reverse too. Active gum infection pumps inflammatory molecules into your bloodstream, which contributes to insulin resistance. That makes blood sugar harder to control and can worsen diabetic complications. Treating gum disease in diabetic patients often improves their blood sugar management, and keeping blood sugar stable helps protect the gums.
Hormonal Changes
Shifts in estrogen and progesterone levels affect how your gums respond to plaque bacteria. During puberty, pregnancy, and menopause, these hormonal changes can alter the composition of bacteria in your mouth, amplify your body’s inflammatory response to plaque, and reduce bone density in the jaw. Pregnancy gingivitis is common enough that many women notice their gums bleed more during the second and third trimesters, even without changes in their brushing habits. The heightened sensitivity typically resolves after hormone levels stabilize, but untreated inflammation during these periods can progress to more serious disease.
Genetic Factors
Some people are more genetically prone to gum infections than others. The most studied genetic link involves variations in the genes that control production of a key inflammatory signaling molecule. In a landmark study of nonsmokers, people who carried a specific combination of two gene variants had nearly seven times the risk of developing severe chronic gum disease compared to those without the variants. Among study participants aged 40 to 60, 78% of those with severe periodontitis carried the high-risk gene combination, compared to just 16% of those with mild disease.
This doesn’t mean gum disease is inevitable if you carry these genes. It means your immune system may overreact to plaque bacteria, producing more inflammation than necessary and causing faster tissue breakdown. If you have a strong family history of gum problems despite good hygiene, genetics may be part of the picture.
Medications That Affect Your Gums
Several common drug classes can cause gum tissue to grow abnormally, a condition called gingival overgrowth. The three main categories are anticonvulsants used for epilepsy, immunosuppressants given to organ transplant recipients, and calcium channel blockers prescribed for high blood pressure. Despite doing very different things in the body, all three trigger similar changes at the cellular level in gum tissue, causing it to enlarge and create deeper pockets where bacteria can hide.
Other medications contribute indirectly. Drugs that reduce saliva production (including some antidepressants, antihistamines, and blood pressure medications) leave your mouth drier. Saliva helps wash away food particles and neutralize bacterial acids, so chronic dry mouth significantly raises your risk of plaque buildup and gum infection.
Nutritional Deficiencies
Vitamin C plays a direct role in gum health because it’s essential for producing collagen, the structural protein that holds gum tissue together. It also helps protect cells from oxidative damage and supports blood vessel function. Severe vitamin C deficiency causes scurvy, which produces swollen, bleeding gums as one of its hallmark symptoms. While full-blown scurvy is rare in developed countries, chronically low vitamin C intake weakens your gums’ ability to maintain and repair themselves, making infection more likely to take hold.
Poor Oral Hygiene Ties It All Together
Every risk factor on this list ultimately works through the same pathway: bacteria accumulating on your teeth and gums without being adequately removed. Smoking, diabetes, hormones, genetics, and medications all change the equation by either increasing bacterial growth, weakening your body’s defenses, or masking symptoms. But the foundation is always plaque. Brushing twice daily, flossing to clean between teeth where a brush can’t reach, and getting regular professional cleanings to remove hardened tartar are the most effective ways to prevent gum infections from developing or worsening, regardless of what other risk factors you carry.