Overeruption of periodontally affected unopposed molars in adult rats

Fujita T, Montet X, Tanne K, Kiliaridis S. Overeruption of periodontally affected unopposed molars in adult rats. J Periodont Res 2009; doi: 10.1111/j.1600-0765.2009.01230.x © 2009 John Wiley & Sons A/S Background and Objective:  In clinical practice, anterior teeth with periodontal disease exhibiting signs of overeruption are occasionally encountered. However, the influence of periodontitis on unopposed teeth needs to be further elucidated. This study investigated, in rats, the overeruption pattern of unopposed mandibular molars with experimentally induced periodontitis. Material and Methods:  Sixty adult male rats were divided equally into four groups. In two groups, periodontitis was induced by a silk thread placed around the cervix of the right mandibular molar. In two groups with and without experimentally induced periodontitis, the crowns of the right maxillary molars were reduced occlusally by grinding to simulate unopposed teeth. After 4 wk, the animals were killed and scanned using micro-computed tomography to measure the vertical position of molars and the buccal and lingual alveolar bone levels. Results:  There were no significant differences in the overeruption of opposed molars with and without periodontitis. However, the alveolar bone level of opposed molars with periodontitis was lower than that of healthy molars. Healthy unopposed molars were extruded when compared to molars with an antagonist. The alveolar bone level of healthy unopposed molars was not influenced by molar overeruption. Unopposed molars with periodontitis exhibited significantly larger extrusion than healthy unopposed molars. The lingual alveolar bone level of unopposed molars with periodontitis was lower than that of other healthy and periodontally affected teeth. Conclusion:  The loss of antagonist causes overeruption of the unopposed tooth, which becomes more prominent in the presence of periodontitis.