Abstract: Objective：To compare the periodontal condition of 61 patients before and after orthodontic extrusion treatment．Methods：32 \ anterior teeth and 29\ premolars were selected to be extruded by orthodontic treatment,then we observed and compared their clinical parameters, including the tooth mobility, probing depth (PD) and bleeding index (BI) of the residual roots before orthodontic extrusion, 2 weeks after applying orthodontic force, before the end of orthodontic extrusion, after prosthodontic treatment and 3 months after prosthodontic treatment. The differences of clinical indicators in different periods were compared by statistic methods. Results: 1. Tooth mobility: The mean of tooth mobility increased to 1.50 after two weeks after applying orthodontic force and 1.14 before the end of orthodontic extrusion, both of which were statistically significant (P < 0.05). 2. Probing depth (PD) : The mean value of PD was 2.34 before the end of orthodontic extrusion treatment and after prosthodontic treatment , it decreased to 2.57, which had statistical significance compared with that before orthodontic extrusion treatment (P < 0.05). 3. Bleeding index (BI): The mean value of BI increased to 2.18 2 weeks after applying orthodontic force, and after 3 months of prosthodontic treatment, it decreased to 1.05, both of which were statistically significant (P < 0.05) compared with that before orthodontic extrusion treatment. Conclusion: The periodontal condition may change temporarily during orthodontic tooth root extrusion, but there is no permanent damage to the periodontal tissue after root extrusion.

Key words: Orthodontics, root extrusion, periodontal condition