Gingival margins for crowns: a review and discussion. Part II: Discrepancies and configurations.

While there is variation regarding the maximum acceptable marginal discrepancy, there is little argument that poorly fitting margins are a frequent finding. Large discrepancies are clinically significant, since they facilitate plaque retention. Margins incorporating slip joint geometry have usually been favored as a method of minimizing seating and sealing discrepancies. However, many of these discussions largely ignored the effects of the cementing medium and the clinical applicability of slip joint geometry is based on questionable assumptions with regard to casting accuracy and seating. Greater understanding of the role of restorative margins and gingival health indicates the need for shallow margin placement within the crevice, which requires a reassessment of the use of long bevels. Horizontal margins can be made accurately and, when combined with procedures to maximize crown seating, may provide the best method of minimizing seating discrepancies and maximizing gingival health.