[Periodontal aspects of cementation: materials, technics and their biologic reactions]

Cementation of crowns and bridges has an influence on the health of marginal periodontal structures. Ideally, the marginal discrepancy should be less than 50 microns which has been considered clinically acceptable. With discrepancies larger than 80 microns, the bleeding tendency and sulcus fluid flow rate increased. A shoulder-bevel preparation results in the smallest marginal discrepancy. Cytotoxicity of cements has been studied in cultures of gingival cells and fibroblasts. Composite has always a more pronounced cytotoxicity as compared to glass-ionomers and zinc phosphate cements. However, large differences exist in cytotoxicity between materials of the same group. Erosion of the cement leads to leakage of toxic materials and the formation of niches colonised by oral plaque bacteria. A number of clinical recommendations are made to minimize the effect of cements and cementation on the periodontal structures.