Three-dimensional changes in the position of unopposed molars in adults

The aim of this study was to longitudinally examine, in adults, changes of position in the three dimensions of maxillary molars unopposed for more than 10 years. Twelve healthy mature adults (six males, six females; mean age 45 years 11 months) with unopposed molars were followed-up for a mean period of 10 years 7 months. Plaster casts were made at the first and last examination. The patients presented 22 unopposed maxillary molars at both recordings and 14 posterior teeth with antagonists, at least one in each subject, without significant modifications during the study period. On three-dimensional scanned plaster casts, changes in the centroid of the occlusal surface were measured in the three dimensions. The changes observed on both occasions were compared with a t-test. Vertical displacement of unopposed molars [0.8 mm, standard deviation (SD) 0.65 mm] and controls (0.4 mm, SD 0.2 mm) was noted. The unopposed teeth overerupted more than the controls (P <= 0.06); periodontally affected molars erupted more than periodontally healthy molars ( P <= 0.01). There was significant mesial displacement of unopposed molars without mesially adjacent teeth when compared with their respective controls ( P <= 0.04). Palatal movement was observed in the unopposed teeth (0.9 mm, SD 0.6 mm) and was significantly greater than that in the controls (0.5 mm, SD 0.3 mm; P <= 0.02). There is displacement of unopposed teeth in the three dimensions in the long term, although this is clinically insignificant in periodontally healthy adults. The observed changes are either the result of late growth remodelling or a consequence of altered dental equilibrium following antagonist tooth loss.