When some children smile, they may show an excessive amount of gum tissue. This is called a gummy smile and may be due to a few different problems:

Gum irritation and overgrowth from braces. This is more likely to happen if the teeth appear shortly before the braces are placed on the teeth. This problem results not from the quality of the orthodontic care but is a result of pre-treatment gum and bone thickness. Altered passive eruption. The gum and bone [...]