The seven categories are as follows:

Gingivitis
Chronic periodontitis
Aggressive periodontitis
Periodontitis as a manifestation of systemic disease
Necrotizing ulcerative gingivitis/periodontitis
Abscesses of the periodontium
Combined periodontic-endodontic lesionsMoreover, terminology expressing both the extent and severity of periodontal diseases are appended to the terms above to denote the specific diagnosis of a particular person or group of people. Severity
The "severity" of disease refers to the amount of periodontal ligament fibers that have been lost, termed "clinical attachment loss". According to the 1999 classification, the severity of chronic periodontitis is graded as follows:
Slight: 1–2 mm (0.039–0.079 in) of attachment loss
Moderate: 3–4 mm (0.12–0.16 in) of attachment loss
Severe: ≥ 5 mm (0.20 in) of attachment loss

Extent
The "extent" of disease refers to the proportion of the dentition affected by the disease in terms of percentage of sites. Sites are defined as the positions at which probing measurements are taken around each tooth and, generally, six probing sites around each tooth are recorded, as follows:

Mesiobuccal
Mid-buccal
Distobuccal
Mesiolingual
Mid-lingual
DistolingualIf up to 30% of sites in the mouth are affected, the manifestation is classified as "localized"; for more than 30%, the term "generalized" is used. 2017 classification
The 2017 classification of periodontal diseases is as follows:Periodontal health, gingival disease and conditions

Periodontal health and gingival health
Clinical gingival health on an intact periodontium
Clinical gingival health on an intact periodontium
Stable periodontitis
Non periodontitis person
Gingivitis - Dental biofilm induced
Associated with the dental biofilm alone
Mediated by systemic and local risk factors
Drug induced gingival enlargement.
For smaller spaces, products such as narrow picks with soft rubber bristles provide excellent manual cleaning. Persons with dexterity problems, such as with arthritis, may find oral hygiene to be difficult and may require more frequent professional care and/or the use of a powered toothbrush. Persons with periodontitis must realize it is a chronic inflammatory disease and a lifelong regimen of excellent hygiene and professional maintenance care with a dentist/hygienist or periodontist is required to maintain affected teeth. Initial therapy
Removal of microbial plaque and calculus is necessary to establish periodontal health. The first step in the treatment of periodontitis involves nonsurgical cleaning below the gum line with a procedure called "root surface instrumentation" or "RSI", this causes a mechanical disturbance to the bacterial biofilm below the gumline. This procedure involves the use of specialized curettes to mechanically remove plaque and calculus from below the gumline, and may require multiple visits and local anesthesia to adequately complete. In addition to initial RSI, it may also be necessary to adjust the occlusion (bite) to prevent excessive force on teeth that have reduced bone support. Also, it may be necessary to complete any other dental needs, such as replacement of rough, plaque-retentive restorations, closure of open contacts between teeth, and any other requirements diagnosed at the initial evaluation.