CLINICAL AND STRUCTURAL CHARACTERISTICS OF PERIODONTAL TISSUES IN YOUNG AND OLD DOGS

The aim of this study was to examine some clinical and structural features of healthy periodontal tissues in young and old beagle dogs. The material consisted of 10 beagle dogs; group I (1-year old) and group II (8-9 years of age). All animals belonged to the same beagle dog colony and had been carefully monitored from birth. A given day was termed day 0 on which the teeth of all 10 dogs were scaled and polished and a 6-week period of enhanced plaque control was initiated. On day 42, clinical examinations were performed and biopsies obtained from the right mandibular 4th (4P) and 3rd (3P) premolar regions. The biopsies were prepared for histometric and morphometric analyses. Clinically, the lower premolars of the old but not the young dogs showed signs of marked wear. In the old dogs, the free gingival unit had a more curved and bulky appearance than in the young animals and in the old dogs, the free gingiva was consistently separated from the attached gingiva by a gingival groove. The histometrical dimensions of the free marginal gingiva and the width of the coronal portion of the periodontal ligament did not differ between the 2 groups of dogs. The apical cells of the junctional epithelium (aJE) in the young dogs were consistently located at the cemento-enamel junction (CEJ), whereas in the old dogs, aJE was consistently located apical to the CEJ. The width of the root cementum assessed at the level of the CEJ did not differ between the 2 dentitions, while the cementum layer, measured at the level of the bone crest (BC) and 1 mm apical to the BC, was about 5-10 times wider in the old than in the young dogs. The connective tissue occupying (i) the central portion of the free gingiva, (ii) the supracrestal area adjacent to the root cementum and (iii) the coronal portion of the periodontal ligament in young dogs, harbored a larger proportion of fibroblasts than in old dogs. The collagen content in the 2 latter compartments was larger in the old dogs. Consequently, the collagen-fibroblast ratio (Co/Fi) was significantly higher in the old than in the young dogs.