Long Term Changes in the Molar Position in Adults

Unopposed molars in adults overerupt to a different extent and other movements like tipping and rotation may also occur.

Objectives: To examine longitudinally the changes in the three dimensions of the position of maxillary molars unopposed for more than ten years in adults and relate them to functional factors.

Subjects: Twelve healthy mature adults (6 males, 6 females, mean age: 45y 11 mo) with unopposed molars were followed-up for at least ten years (mean follow up time 10 years 7 months, SD: 16 months). Plaster casts existed in the beginning of the follow-up period and new casts were made at the last examination. In total the patients presented 22 unopposed maxillary molars and 14 posterior teeth with antagonists in both recordings. The later were used as controls and there was at least one in each subject.

Methods: On 3D images of the plaster casts, we measured the changes in the three dimensions of the centroid of the occlusal surface on the 3D model.

Results: We found vertical displacement in the 22 unopposed molars (median: 0.51mm, range:0.22-2.78mm) and the controls (median: 0.30mm, range:0.19-1.13). Unopposed teeth overerupted more than controls (p=0.03). Palatal movement of the centroid was observed in both groups. For the unopposed teeth (median:0.44mm, range: 0.21-2.37mm) it was significantly higher than in the control group (median:0.30 mm, range:0.19-0.73 mm) (p=0.03). All teeth moved mesially, nevertheless a significant mesial displacement of unopposed molars occurred in the absence of a mesially adjacent teeth when compared to the respective controls (p=0.02).

Conclusions: Displacement of unopposed molars in the three dimensions is observed in the long term, though clinically insignificant in periodontally healthy teeth. This may be the result of late “growth changes”, altered function of the stomatognathic system and a consequence of an altered dental equilibrium following the loss of an antagonist tooth.