The appearance of a visible edge on the crown and the yellowish discoloration of the underlying tooth root can be related to both physiological aging and dental errors. Physiologically, gums can recede slowly by an average of 0.1 mm per year in everyone as they age; this is a normal process. However, if this edge becomes visible just a few months after a crown is placed, two main errors should be sought: Firstly, the gum line (step) was left too high during tooth preparation; secondly, the gum retracts to protect itself due to excessive pressure from the crown (biological width violation or overhanging edge). In other words, early exposures are entirely due to mechanical reasons and a failure to adhere to periodontal principles.
