Supraeruption of the unopposed maxillary first molar.

Supraeruption of the maxillary first molar in the absence of the mandibular first molar was observed in subjects with both normal and pathologic periodontics. Both the migration of the gingival margin and the increase in the crown height were evaluated in terms of the length of time the antagonist tooth had been missing. Values obtained were compared with those of a reference group with complete normal dentitions. The results show that in the first years following the loss of the opposing tooth, supraeruption is mainly due to growth of the periodontium. Later or in the case of periodontal pathosis, tooth movement beyond the occlusal plane is due principally to active eruption.