A posterior crossbite is a common malocclusion among patients. This means that the upper jaw is too narrow, lower jaw is too wide or both. An orthodontist is a specialist with 2 years of additional training over a general dentist and has the skills needed to determine the correct mechanics to correct this problem. Many orthodontists use a rapid palatal expander (RPE) to correct crossbites on many of their cases. These work well but are very bulky appliances which split the palatal bone and need to remain in place for six to twelve months. Although this appliance works, there are other ways to correct crossbites in many patients using braces alone with the knowledge of moments, forces and vectors. Remember physics? This is a patient that I treated back in 2010 without an expander. Notice how much wider his upper jaw is. Also his midlines are now perfect. If you have been told that you or your child need an expander you may be able to be treated without one. Let us know if we can help.