Extensive carious lesions in primary molars often confront the dentist with a dilemma: extraction or restoration. The primary molar constitutes an important element in the development of the dentition. If extraction is considered, the dentist should be aware of the possible risks towards malocclusion or malposition. In order to understand these consequences a brief summary of normal dentition development is given, followed by a description of factors influencing development of dentition after premature extraction of a second primary molar. Premature extraction causes a disturbance in the eruption of the successor and migration of the neighbouring teeth. The eruption of the bicuspid can be delayed or accelerated according to the stage of root formation. The rate, amount and direction of migration depends on the extracted element, time of loss, spacing or crowding, eruption sequence, dental relationship, intercuspation, interaction of soft tissues and dental arch, supra-occlusion and the leeway space. To conclude the treatment modalities of pulp pathologies in primary molars are outlined. In children with deep carious lesions a treatment plan involves the child's medical history and social development as well as orthodontic, preventive and restorative aspects.