Replacing an Old Metal Crown with All-Ceramic: Colour Is Not the Only Consideration｜證據鏈

A dark margin or unnatural colour around an old metal crown may understandably make you want to replace it with an all-ceramic crown. Whether the new crown can be built on a stable foundation, however, cannot be decided with a shade guide alone. Before replacement, it is necessary to determine whether the abutment tooth still has restorable tooth structure, whether the pulp or periapical tissues show any abnormality, whether the old crown margin fits and can be cleaned, and whether gingival inflammation, recession, or periodontal pockets need to be treated first. A systematic review shows that plaque, bleeding, pocket depth, and attachment status around fixed crowns may differ from those of unrestored control teeth, but the studies do not prove that replacing metal with all-ceramic alone improves periodontal health. The marginal fit of ceramic crowns is also affected by the preparation finish line, the cement space allowed, veneering ceramic, and bonding procedures; it is not determined by the material name alone. The more cautious commitment, therefore, is not “once the old crown is removed, an all-ceramic crown can definitely be made”.