Although the purpose of orthodontic treatment is to increase the function and esthetics of the jaws along with increasing stability, there are many side effects during the treatment itself, such as root resorption and alveolar bone resorption. Such resorption of the apical root is unpredictable, and may even proceed into the dentin layer, Once the process has begun, it is irreversible. By evaluating the effect of many oral habits, especially that of nail biting, in correlation with the root and the periodontal tissues´, the appropriate biomechanics for orthodontic treatment can bee taken into consideration, along with the possibility of root resorption and alveolar bone loss during orthodontic treatment, and any legal problems that might occur
Among the male and female patients of the ages 10-15, without skeletal deformity, 63 were chosen as the experiment group with known nail biting habits at time of examination, and within the same age group without -nail biting habits as the -control, After the´orthodontic treatment, number of the experiment group was 31 and the control group was 22.
The periapical radiographies of anterior teeth were taken and the assesment of the root length and alveolar bone level were taken before(Tl) and after(T2) the orthodontic treatment.
The results from this study were as follows
1. Before the orthodontic treatment, average crown-to-root ratio of the experimental group showed noticeably high values in 4 maxillary incisors and mandibular right central incisor.
2. Before the orthodontic treatment, comparing the root length, maxillary and mandibular right central incisors and both mandibular incisors had a smaller value in the experimental group.
3. Before the orthodontic treatment, comparing and evaluating the alveolar bone loss measured from the cemento-enamel
junction to the alveolar bone crest; some crestal bone of the experiment group showed greater loss than the control. 4. After the orthodontic treatment, there was shortening of the root length and loss of the crestal bone in both groups. 5. After the orthodontic treatment, the changes of C/R ratio and the shortening of root length were significantly high in
the experimental group.
6. After the orthodontic treatment; the level of alveolar crestal bone showed greater loss in the experimental group.
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