Abnormal eruption patterns can cause a single molar to end up in crossbite. Appliance selection to correct this problem is dependent upon the depth of the bite and the existence of adequate arch space to move the tooth back into position. Typically there is plenty of space to move the molar back into the arch. However, if clinical and model examination indicates a significantly deep bite and the tooth is locked lingually, a small anterior bite plane should be added to the appliance. Here a single expansion screw is used to exert pressure on the molar. With this expansion screw, you should expect to get both tipping and some bodily movement of the molar. Note: All expansion screws of this type are adjusted once a week, one-quarter turn. As with all crossbite cases, the lab must be supplied with upper and lower models and a wax bite -- this in the express interest of enabling a check for occlusal interference and assistance in selecting the right design.