When your treatment plan requires that a crown and loop space maintainer be used for an extended period of time, it is suggested that the appliance include a rest on the abutment tooth to prevent unwanted mesial movement and tipping. Sometimes it will be necessary to prepare a rest seat in the supporting tooth to keep the occlusion clear of any interference. Added retention can also be gained by bonding the rest into position with composite resin. Note: When taking an impression for this appliance, it is best to take the impression with the crown in place. Then, with the crown firmly seated, pour the impression.