The way the marginal edges of a dental crown (where it joins the gum) are prepared determines the future of the surrounding soft tissues. Chamfer preparation involves creating a shallow, slightly rounded step at the neck of the tooth, providing excellent marginal fit and thin material transition, especially in zirconium or metal-supported crowns; this prevents bacterial plaque accumulation and protects gum health. Shoulder preparation, on the other hand, involves creating a steep step at a 90° angle, providing sufficient material thickness for all-ceramic (E.max) crowns and preventing marginal fractures. If the step is not properly prepared, left rough, or extended too far below the gum (subgingival space), violating biological width, the crown edge will constantly irritate the gum, leading to chronic marginal gingivitis, gum discoloration, and eventually irreversible gum recession.
