Abstract: Objective： To retrospectively evaluate clinical and radiographic records of chronic periodontitis patients who underwent extraction-orthodontic treatment, in order to determine the effect of the treatment on probing depth, alveolar bone height of teeth adjacent to the extraction sites. Methods: In the study, 33 chronic periodontitis patients who had finished extraction-orthodontic treatment were selec-ted, the periodontal examination system tables and panoramic tomography were recorded before treatment (T0) and after treatment (T1), and  the periodontal probing depth (PD), residual alveolar bone height(RBH) of the teeth adjacent to extraction sites (TAES) and the non-teeth adjacent to extraction sites (NTAES) were measured at T0 and T1. Results: There was insignificant difference in PD of TAES and NTAES at T0 ［(2.40±0.51) mm vs. (2.42±0.55) mm，P>0.05］, neither was that at T1 ［(2.70±0.67) mm vs. (2.67±0.64) mm， P>0.05］; From T0 to T1, PD of TAES and NTAES had mean increases of 0.3 mm ［(2.40±0.51) mm vs. (2.70±0.67) mm，P<0.01］ and 0.25 mm ［(2.42±0.55 mm vs. (2.67±0.64) mm， P<0.01］, respectively. And PD of TAES and NTAES increased from T0 to T1 statistically in the same degree ［(0.30±0.64) mm vs. (0.25±0.58) mm，P>0.05］; at T0, RBH of TAES was 0.024 smaller than that of NTAES (0.74±0.16 vs. 0.76±0.16，P<0.05), but there was no difference in RBH between the TAES and NTAES at T1 (0.78±0.14 vs. 0.79±0.12，P>0.05); From T0 to T1, RBH of TAES and NTAES had mean increases of 0.04 (0.74±0.16 vs.0.78±0.14，P<0.05) and 0.02 (0.76±0.16 vs. 0.79±0.12，P<0.05), respectively. And the change of RBH between TAES and NTAES from T0 to T1 had no statistical difference (0.04±0.11 vs. 0.02±0.08，P>0.05)RBH of TAES in the side close to extraction sites was as the same as that of TAES in the side away from the extraction sites at T0 (0.73±0.17 vs. 0.74±0.16，P>0.05). From T0 to T1, RBH of both sides of TAES had mean increases of 0.04 (0.73±0.11 vs. 0.77±0.11，P<0.05) and 0.04 (0.74±0.11 vs. 0.78±0.11，P<0.05), respectively. But for both sides of TAES, from T0 to T1, there was no significant difference in change of RBH (0.04±0.11 vs. 0.04±0.11，P>0.05). Conclusions: With strict control of periodontal inflammation and maintenance of oral hygiene, orthodontic treatment preserves the periodontal conditions in patients with chronic periodontitis, and the extraction-orthodontic treatment can preserve the bone height of the teeth adjacent to extraction sites.

Key words: Chronic periodontitis, Extraction-orthodontic treatment, Alveolar bone height, Probing depth