A distal step in the primary dentition indicates that the mandibular second primary molar is positioned more posteriorly relative to the maxillary second primary molar. This relationship often predicts a Class II molar relationship in the permanent dentition, where the lower jaw is relatively retruded compared to the upper jaw. The distal step disrupts normal mesial shift of the mandibular molars during growth, leading to an increased overjet characteristic of Class II malocclusion. Early identification helps in planning interceptive orthodontic treatment to prevent worsening of the malocclusion.

Reference: Pediatric Dentistry: Infancy through Adolescence, Pinkham, 6th Edition.