Long-term follow-up of tooth mobility in maxillary incisors with orthodontically induced apical root resorption

The aim of the study was to evaluate tooth mobility in relation to root length and alveolar bone support in maxillary incisors 10-25 years after orthodontic treatment, and to monitor the development during 5 years in a sub-sample. Thirty-six patients, seven males and 29 females with one or more severely resorbed maxillary incisors, a total of 139 teeth, were examined. At re-examination, 11 patients were older than 40 years, 20 were between 30 and 39, and five younger than 30 years. Root length, alveolar bone height, and crestal alveolar bone level were measured on standardized intraoral radiographs. Tooth mobility was registered using Miller's index and the periotest method. Statistical analysis was undertaken using a t-test for dependent and independent samples, and chi-square tests for comparison of the relationship between the periotest values (PTVs) and the variables periodontal pocket depth, gingival index, incisal facets, interferences, and anamnesis. The majority of the teeth were stable. The correlation between root length and alveolar bone height was high, with minimal changes of marginal bone support. Extremely resorbed incisors with a root length less than 10 mm had significantly higher PTV than teeth with longer roots and greater bone support. In the sub-sample, tooth mobility was followed in 16 patients, two males and 14 females, with 62 maxillary incisors over a 5-year period. The PTV increased significantly on average, particularly in teeth with extreme resorption. Increasing mobility can be expected with age in teeth with extremely resorbed roots. Teeth with a root length > or =10 mm and a healthy periodontium remain stable.