– established periodontal disease with 25–50% attachment loss of the tooth from the alveolar bone. Treatment includes teeth extraction, closed or open root planing, or advanced periodontal treatment options like guided tissue regeneration. Stage 4 (PD4) – advanced periodontal disease with more than 50% attachment loss of the tooth from the alveolar bone. Extraction of teeth or periodontal surgery, including osseous resective or additive procedures, are necessary. The prognosis for this stage is guarded. The amount of calculus present is scored by using the Calculus Index (CI), which consists of four stages: Stage 0 (CI0) – no calculus is present. Stage 1 (CI1) – some calculus above the gum line that covers less than 1/3 of the tooth surface. Stage 2 (CI2) – moderate calculus covering 1/3 to 2/3 of the tooth surface with minimal calculus below the gum line. Stage 3 (CI3) – heavy calculus covering more than 2/3 of the tooth surface and extending below the gum line. See also Equine dentistry Horse teeth Dental health diets for dogs Dental health diets for cats References External links Organizations: Academy of Veterinary Dental Technicians Academy of Veterinary Dentistry American Society of Veterinary Dental Technicians American Veterinary Dental College American Veterinary Dental Society British Veterinary Dental Association European Veterinary Dental College European Veterinary Dental Society Veterinary Oral Health Council WikiVet Dentistry Guidelines: AAHA-AVMA canine preventive healthcare guidelines AAHA-AVMA feline preventive healthcare guidelines Veterinary professions