ENHANCED GINGIVITIS IN THE DECIDUOUS AND PERMANENT DENTITION - AN EXPERIMENTAL-STUDY IN THE DOG

The aim of the experiment was to analyze the reaction of the marginal gingival tissues to 21 days of plaque formation on buccal tooth surfaces in the deciduous and permanent dentition of beagle dogs. In order to enhance the formation of plaque, the buccal surfaces of the experimental teeth were coated with a composite filling material. 5 beagle dogs were used. The animals were monitored during 2 periods, called period A (42 days during the deciduous dentition) and period B (42 days during the permanent dentition). The dogs were 10 weeks old at the initiation of period A. Following 3 weeks of plaque control, a groove was prepared into the enamel of the buccal surfaces of the mandibular right 3rd (03P) and 2nd (02P) premolars. A cotton ligature was subsequently attached to the groove using an enamel/etch-technique and a composite filling material. The groove and the ligature did not interfere with the gingival margin but the composite material extened into the subgingival niche. The plaque control measures were abandoned. The animals formed plaque during the following 21 days. A clinical examination was performed and subgingival bacteria sampled on day 21. Moreover, biopsies were harvested from the 03P and 02P tooth regions. The biopsies were prepared for histometric and morphometric analyses. A 2nd plaque control regimen was intiated. Period B started when the dogs were 15 months old. Following 3 weeks of enhanced plaque control, a cotton ligature was attached as described above at the buccal surfaces of the mandibular left 3rd (P3) and 4th (P4) premolars. The oral hygiene regimen was terminated and plaque allowed to accumulate. The clinical examination, bacterial sampling and biopsy were repeated after 21 days of plaque formation. It was observed that the height of the free marginal gingiva (hFG) was smaller in the deciduous than in the permanent dentition. The volume of the free gingival unit which was occupied by an infiltrated connective tissue (ICT) and the total portion of inflammatory cells residing in the dentogingival epithelium were similar in the 2 dentitions. In the apical 3rd of the dentogingival epithelium, the volume of leukocytes was significantly larger in the deciduous than in the permanent dentition. The proportion of plasma cells within the ICT was about 4-5 x larger in the permanent than in the deciduous dentition. Black-pigmented Bacteroides occurred in 3 out of 5 dogs in the subgingival microbiota, representing 21 days of plaque formation in the deciduous dentition, whereas in the permanent dentition, black-pigmented Bacteroides occurred in all and Porphyromonas (Bacteroides) gingivalis in 3 of the 5 dogs.