Histologic characteristics of experimental gingivitis in the juvenile and adult beagle dog.

An earlier study (Matsson & Attström 1979) revealed an unexplained difference between juvenile and adult dogs in the propensity to develop clinical signs of gingivitis. The aims of the present investigation were to depict the structural composition of clinically normal gingiva and to analyze the histologic changes in the gingiva during plaque development in juvenile and adult dogs. Six beagle dogs were used. Two periods of discontinued oral hygiene were studied, the first at 3 and the second at 12 months of age. Biopsies were sampled on days 0, 4, 7, 14, 21 and 28 of each period. Sections from the biopsies were analyzed at two levels of magnification. Compared to adult dog gingiva, juvenile gingiva seemed to display: 1) a thicker keratinized layer of the oral epithelium, 2) a junctional epithelium that structurally resembles the oral epithelium, 3) a cuticular structure at the surface of the junctional epithelium, 4) a limited mononuclear inflammatory cell response during experimental gingivitis, and 5) a delayed establishment of an infiltrated connective tissue portion during experimental gingivitis. In addition, during experimental gingivitis, subgingival plaque formed along the tooth surfaces to a lesser extent in the juvenile stage compared to adult dogs.