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The extension of periodontitis or a periodontal pocket into an area where the tooth roots divide.
tri·fur·ca·tion in·volve·ment(trīfŭr-kāshŭn in-volvmĕnt)
Colloq. for dental decay or periodontal disease that affects the area of the tooth where the root separates into three parts. Maxillary molars have three roots and are most commonly affected.