title: Spontaneous gingivitis related to hair penetration in rats.
abstract: Maxillary gingivae from male and female Crl:CD(SD) rats at 12, 16, 21, and 34 weeks of age were examined histologically. The incidence of gingivitis was approximately 40%, with no age or sex predilection, and was most frequent between the first and second molar. Lesions were characterized by acute focal neutrophilic infiltration into the gingival mucosa, occasionally with inflammatory exudate. In severe cases, inflammation extended to the periodontal ligament with abscess formation, and adjacent alveolar bone destruction/resorption. The most characteristic finding was the presence of hair shafts associated with the lesion, which was observed in approximately 80% of the rats with gingivitis. These findings suggest that molar gingivitis occurs in rats from an early age and persists thereafter, and that the main cause of gingivitis in rats is hair penetration into the gingiva. It would be prudent to keep these background lesions in mind as potential modifiers in toxicity studies.
authors.affiliation: Tsukuba Drug Safety, Global Drug Safety, Biopharmaceutical Assessments Core Function Unit, Eisai Co., Ltd., 5-3-1 Tokodai, Tsukuba-shi, Ibaraki 300-2635, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Goto
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authors.lastname: Sonoda
authors.forename: Yuki
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authors.lastname: Seki
authors.forename: Yoshikazu
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authors.lastname: Taketa
authors.forename: Etsuko
authors.initials: E
authors.lastname: Ohta
authors.forename: Kyoko
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authors.lastname: Nakano
authors.forename: Akira
authors.initials: A
authors.lastname: Inomata
authors.forename: Kazuhiro
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authors.lastname: Hayakawa
authors.forename: Toyohiko
authors.initials: T
authors.lastname: Aoki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tsukidate
authors.forename: Satoru
authors.initials: S
authors.lastname: Hosokawa