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In dentistry, a furcation defect is bone loss, usually a result of periodontal disease, affecting the base of the root trunk of a tooth where two or more roots meet (''bifurcation'' or ''trifurcation''). The extent and configuration of the defect are factors in both diagnosis and treatment planning.〔Ammons WF, Harrington GW: Furcation, The Problem and Its Management. In Newman, Takei, Carranza, editors: ''Carranza's Clinical Periodontology'', 9th Edition. Philadelphia: W.B. Saunders Co. 2002. page 826-7.〕 A tooth with a furcation defect typically possessed a more diminished prognosis owing to the difficulty of rendering the furcation area free from periodontal pathogens. For this reason, surgical periodontal treatment may be considered to either close the furcation defect with grafting procedures or allow greater access to the furcation defect for improved oral hygiene. ==Root trunk length== The distance between the cementoenamel junction (CEJ) and the furcation entrance is called the ''root trunk length''. This distance plays an important role in furcation defects because the deeper the furcation entrance is within the bone, the more bone loss necessary before the furcation becomes exposed. For mandibular first molars, the mean root trunk length is 3 mm on the buccal aspect and 4 mm on the lingual aspect.〔Carnavale F, Pontoriero R, Lindhe, J: Treatment of Furcation-Involved Teeth. In Lindhe, Karring, Lang, editors: ''Clinical Periodontology and Implant Dentistry'', 4th Edition. London: Blackwell Munksgaard. 2003. pages 707-8.〕 The root trunk lengths for mandibular second and third molars are either the same or slightly greater than for first molars, although the roots may be fused. For maxillary first molars, the mean root trunk length is 3-4 mm on the buccal aspect, and 4-5 mm on the mesial aspect and 5-6 mm on the distal aspect.〔 As with mandibular molars, the root trunk lengths for maxillary second and third molars are either the same or slightly greater than for first molars, although the roots may be fused. For maxillary first premolars, there is a bifurcation 40% of the time and the mean root trunk length is 8 mm from both mesial and distal.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「furcation defect」の詳細全文を読む スポンサード リンク
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