The Effect of Oral Hygiene Practice upon the Experimental Periodontitis Induced by the Crown Margin Extension

The effects of oral hygiene practices (careful cleaning with a toothbrush and application of 0.2 percent chlorhexidine once a day for 2 months) upon the gingival inflammation and the crown margin extension were studied. The cervical position of each crown was built up according to the following system: 1) 1mm above, 2) even with and 3) 0.5mm below the gingival margin. Twenty-four teeth in 3 adult dogs were examined. Four teeth of each dog had been used for oral hygiene areas, whereas an equal number of unilateral teeth in the same dogs served as non-oral hygiene areas. The gingival state and oral hygiene were recorded according to the index systems (Löe, 1967). Pocket depths were calculated. The gingival exudate measurements had been also assessed using the orifice method (Takayama et al, 1977). The animals were sacrificed 5 months following the placement of the crowns. The blood vessel topography at the dentogingival junction was studied, after perfusion with a carbon-gelatin mixture prior to the sacrifice. The tissues were dissected and fixed in 10 percent formalin. They were decalcified and embedded in paraffin. Bucco-lingual and horizontal serial sections 8 microns thick were made and stained with hematoxylin and eosin. The gingivae adjacent to the crowns were observed microscopically. The morphologic changes are described, based upon the clinical, the cellular inflammatory and the epithelial changes. The results indicate that the periodontal conditions were better in the areas with oral hygiene practice as compared with the non-cleaned areas.