A cross bite is when the top teeth bite inside (right side of image) the bottom teeth. This is a good indicator that the upper jaw is not wide enough to allow for the proper eruption of permanent teeth. In most cases an expanded is need to help create space for the eruption of permanent teeth. If this condition is left untreated the treatment plan may require the removal of permanent teeth in order to achieve a desired treatment result. Early treatment can prevent the need of extractions and in the majority of cases make the second phase proceed much easier.