Immunopathological Study of the Gingival Tissue after Setting Full Cast Crowns

In order to investigate the effects of the location of the crown margin on the gingival tissues, full cast crowns were set in 20 adult canines with the crown margin set at 1mm above, even with, and 0.5mm below the gingival crest. The crowns were retained for 2 weeks, 3 weeks, 1 month, or 3 months. Their effects on the gingival tissues were examined by chronological histopathological investigation and the movement of localization of immunoglobulin (IgG) by fluorescent antibody technique. Marginal fit also was examined. The results were as follows : 1. Histopathological findings a. In the setting at 1mm above the gingival crest, slight inflammatory changes limited to the subepithelial connective tissues in the upper border of the sulcular epithelium were observed. No significant changes were observed in others. b. In the setting at the gingival crest, inflammatory changes in the upper border of the sulcular epithelium, as compared with the setting 1mm-above, became more extensive with a longer setting period. c. In the setting at 0.5mm below the gingival crest, inflammatory changes in the subepithelial connective tissues increased, as compared with the other two settings. The changes near the crown margin in the sulcular epithelium were especially significant and cellular infiltration was observed in the whole lamina propria at the site. 2. Findings by the fluorescent antibody technique a. In the setting at 1mm above the gingival crest, parakeratinized layers of the oral epithelium, slight fluorescence only in the sulcular epithelium, and localization of IgG and the cells containing IgG were observed. No other significant changes were observed. b. In the setting at the gingival crest, granular fluorescence in the perivascular and intravascular areas as well as in the sulcular epithelium were observed with a longer setting period, in comparison with the setting 1mm-above. Localization of IgG and the cells containing IgG expanded in areas. c. In the setting at 0.5mm below the gingival crest, fluorescence was intense in the sulcular epithelium, particularly near the crown margin, as compared with the other two settings. Diffused fluorescence also was observed in the whole lamina propria. Granular fluorescence was observed in the perivascular and intravascular areas in the lamina propria. IgG and the cells containing IgG increased as compared with the other two settings. 3. Film thickness of cement layer of the experimental crown was 37.9μm for the cases above,