Histopathologic study of squamous cell carcinoma of the gingiva in edentulous and dentulous jaws of hamsters treated with N-methylnitrosourea.

Unilateral maxillary or mandibular molars were extracted from twenty-four, 25-day-old male syrian golden hamsters; 25 days after extraction, 20 received MNU intragastrically twice a week for 3 months. All animals were killed 1 month later. High degrees and incidence of invasion of gingival SCC were observed in dentulous jaws without functional occlusion, followed by dentulous jaws with functional occlusion and edentulous jaws. Invasion of carcinomas with extensive bone destruction was observed commonly in the gingiva of dentulous maxillary jaws without functional occlusion, but was scarcely observed in the gingiva of edentulous jaws. By analogy, disuse atrophy of the periodontium due to loss of functional occlusion may result in early deeper invasion, while loss of periodontal ligament due to tooth extraction and disappearance of so-called inner gingival epithelium may result in less invasive carcinomas.