Kristin has had braces applied to her teeth. The pink and blue traintracks will remain in place for six to eight months and are intended to remove the famous inherited GAP from her smile. The gap between the two front teeth showed up with both Kristin and Jakob, and was inherited from Mom, whose gap closed up in later years.
Kristin decided that she didn't want to have the gap any more, so she went for the braces. She can't chew gum, or eat really chewy stuff, but apparently it is okay to still eat chocolate.