Early loss of primary first molars. Early loss of primary first molars can cause distal drifting of the primary canine if the loss occurs during the active eruption of the permanent lateral incisors. Early loss of primary second molars is a problem because these teeth serve as a guide for the erupting permanent first molars. Early loss of a primary second molar, especially in the maxillary arch, results in arch length reduction due to mesial migration of permanent molars. If the first permanent molar has fully erupted, then a band and loop can be placed on either the first permanent molar running mesial to the primary first molar or on the primary first molar running distal to the mesial aspect of the first permanent molar.A distal shoe appliance should be used if the primary second molar is lost before the permanent first molar erupts (Figure 4). There are, however, some drawbacks to the use of this appliance. These complications include difficulty in the accurate construction of the appliance, the presence of a constant foreign body in a sensitive area in the mouth, and a pos-sible route of infection between intraoral and submucosal areas. If multiple primary posterior teeth are missing, the distal shoe should be incorporated in aremovable partial denture.