title: Morphological changes of epithelial rests of Malassez in rat molars induced by local administration of N-methylnitrosourea.
abstract: The objective was to examine the possibility that epithelial rests of Malassez can give origin to odontogenic tumours. A mixture of N-methylnitrosourea (MNU) and alginate impression material for dental use was injected onto the periosteum of the buccal side of the left mandible of 5-week-old, male Wistar rats (300 mg/kg body wt). The mixture was left at the site for several months. The rats were killed 1, 3, 5, and 8 months after the injection. After 5 and 8 months, the epithelial rests of Malassez in the cervical and bifurcational regions of the first, second, and third left mandibular molars were significantly enlarged and the alveolar bone around the lesion was resorbed by multinucleated cells in all rats. The epithelial masses were characterized by enamel organ-like structures, deposition of eosinophilic amorphous material, duct-like structures, and squamous metaplasia. In addition to these masses in the molar regions, odontogenic tumours were induced in the incisal region and carcinomas and sarcomas in the buccal region, knee, bladder, and skin. Local administration of a mixture of MNU and alginate impression material can induce odontogenic tumours from the epithelial rests of Malassez at high incidence.
authors.affiliation: First Department of Oral and Maxillofacial Surgery, School of Dentistry, Niigata University, Japan. hamamoto@dent.niigata-u.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Hamamoto
authors.forename: N
authors.initials: N
authors.lastname: Hamamoto
authors.forename: T
authors.initials: T
authors.lastname: Nakajima
authors.forename: H
authors.initials: H
authors.lastname: Ozawa
mesh_terms: D000464:Alginates; D000818:Animals; D002273:Carcinogens / Q000008:administration & dosage / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000139:chemically induced / Q000473:pathology; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000473:pathology; D003760:Dental Impression Materials; D004847:Epithelial Cells / Q000187:drug effects* / Q000473:pathology; D008297:Male; D008334:Mandible; D008339:Mandibular Neoplasms / Q000139:chemically induced / Q000473:pathology; D008770:Methylnitrosourea / Q000008:administration & dosage / Q000494:pharmacology*; D008963:Molar / Q000187:drug effects* / Q000473:pathology; D009808:Odontogenic Tumors / Q000139:chemically induced / Q000473:pathology; D010513:Periodontal Ligament / Q000187:drug effects* / Q000473:pathology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D000464:Alginates; D002273:Carcinogens; D003760:Dental Impression Materials; D008770:Methylnitrosourea