Complications
Recurrence of gingivitis
Periodontitis
Infection or abscess of the gingiva or the jaw bones
Trench mouth (bacterial infection and ulceration of the gums)
Swollen lymph nodes
Associated with premature birth and low birth weight

Alzheimers and dementia
A new study from 2018 found evidence that gingivitis bacteria may be linked to Alzheimers disease. Scientists agree that more research is needed to prove a cause and effect link. "Studies have also found that the bacteria P. gingivalis – which are responsible for many forms of gum disease – can migrate from the mouth to the brain in mice. And on entry to the brain, P. gingivalis can reproduce all of the characteristic features of Alzheimer’s disease." Cause
The cause of plaque-induced gingivitis is bacterial plaque, which acts to initiate the bodys host response. This, in turn, can lead to destruction of the gingival tissues, which may progress to destruction of the periodontal attachment apparatus. The plaque accumulates in the small gaps between teeth, in the gingival grooves and in areas known as plaque traps: locations that serve to accumulate and maintain plaque. Examples of plaque traps include bulky and overhanging restorative margins, clasps of removable partial dentures and calculus (tartar) that forms on teeth. Although these accumulations may be tiny, the bacteria in them produce chemicals, such as degradative enzymes, and toxins, such as lipopolysaccharide (LPS, otherwise known as endotoxin) or lipoteichoic acid (LTA), that promote an inflammatory response in the gum tissue. This inflammation can cause an enlargement of the gingiva and subsequent formation.
In 2017 the FDA banned triclosan in many consumer products but allowed it to remain in toothpaste because of its effectiveness against gingivitis. In 2019, Colgate, under pressure from health advocates, removed triclosan from the last toothpaste on the market containing it, Colgate Total. Treatment
The focus of treatment is to remove plaque. Therapy is aimed at the reduction of oral bacteria and may take the form of regular periodic visits to a dental professional together with adequate oral hygiene home care. Thus, several of the methods used in the prevention of gingivitis can also be used for the treatment of manifest gingivitis, such as scaling, root planing, curettage, mouth washes containing chlorhexidine or hydrogen peroxide, and flossing. Interdental brushes also help remove any causative agents. Powered toothbrushes work better than manual toothbrushes in reducing the disease.The active ingredients that "reduce plaque and demonstrate effective reduction of gingival inflammation over a period of time" are triclosan, chlorhexidine digluconate, and a combination of thymol, menthol, eucalyptol, and methyl salicylate. These ingredients are found in toothpaste and mouthwash. Hydrogen peroxide was long considered a suitable over-the-counter agent to treat gingivitis. There has been evidence to show the positive effect on controlling gingivitis in short-term use.