They are concerned with the fact that these beads do not disintegrate and they are not biodegradable. This makes it easy for small beads to get stuck in between teeth and even become embedded in a person's gums.
According to dentist Justin Phillip "They'll trap bacteria in the gums which leads to gingivitis, and over time that infection moves from the gum into the bone that holds your teeth, and that becomes periodontal disease,"
Procter & Gamble, makers of Crest, say the beads are only put in the toothpaste to add color, and have been FDA approved, and that the ingredient is completely safe. Though, according to them the majority of Crest toothpaste will be microbead-free in about six months and the beads will be completely gone by 2016.