Vertical position, rotation, and tipping of molars without antagonists

There has been a general belief that permanent teeth without antagonists overerupt, creating, after some time, considerable clinical problems. However, very few studies in the literature support this statement. The purpose of this investigation was to examine the position of molars that had been unopposed for a long period and to test the hypothesis that overeruption does affect every tooth without an antagonist.

Fifty-three individuals were examined clinically, and dental casts were taken to evaluate the position of unopposed molars. There were 84 molars (61 in the maxilla and 23 in the mandible) with a documented period of at least 10 years without antagonists. Among these teeth, 25 molars had neither an antagonist nor a mesially adjacent tooth. A qualitative method was used to evaluate the position of the molars in the vertical direction: (1) teeth with no sign of overeruption, (2) teeth with slight overeruption (< 2 mm), and (3) teeth with moderate to severe overeruption (> or = 2 mm).

Of the 84 molars examined, 15 teeth (18%) revealed no signs of overeruption, 49 teeth (58%) displayed overeruption of less than 2 mm, and 20 teeth (24%) showed moderate to severe overeruption. Individuals with molars that had lost their antagonists in adult age had a lower risk for overeruption than the other subjects examined. The existence of adjacent teeth was important for the position of the unopposed molar in a mesiodistal or buccolingual direction. Molar rotation was more frequent in the maxilla, whereas tipping was more common in the mandible.

It is concluded that not all molars without antagonists overerupt, not even in a long-term perspective.