Illustration #1 of 3: Full-Step Class II Molar Relationship
For the malocclusion to satisfy the ABO definition of a full-step Class II molar relationship, the mesiobuccal cusp of the maxillary permanent first molar must occlude, at least on one side, in the embrasure between the mandibular second premolar and the mandibular permanent first molar, or farther to the mesial. If the maxillary or mandibular permanent first molar is missing, the buccal cusp of the maxillary second premolar must occlude in the embrasure between the mandibular first and second premolars, or farther to the mesial. If the maxillary permanent first molar has drifted mesially due to premature loss of the deciduous second molar, that is not considered a full-step Class II molar relationship.
Illustration #2 of 3: End-to-End Class II Molar Relationship
This example demonstrates an end-to-end molar relationship which satisfies ABO criteria for Initial Certification only. It is to be distinguished from the full-step Class II of the preceding illustration.