Abstract: PURPOSE: To compare the orthodontic effects of physiological anchorage Spee's-wire system(PASS) appliance and Clear aligner in Angle Class Ⅱ malocclusion. METHODS: A total of 80 patients with Angle Class Ⅱ malocclusion admitted to Qinghai Provincial Communications Hospital from November 2023 to December 2024 were selected and randomly divided into PASS group and Clear aligner group, with 40 cases in each group. The orthodontic effects, imaging indicators of soft and hard tissues, periodontal indicators, complications, masticatory function and oral health of the patients were compared and analyzed. Results: At 6 months after orthodontic treatment, the peer assessment rating（PAR） score of the PASS group was lower than that of the Clear aligner group (P<0.05). After treatment, U1-NA angle decreased and L1-NB angle increased in both groups, the improvement in the PASS group was more significant than that in the Clear aligner group (P<0.05). There was no significant difference in SNA and SNB between the two groups before and after orthodontic treatment (P>0.05). After treatment,upper and lower lip protrusion (ULP, LLP) decreased, while the Z-angle increased in both groups, the improvement in the PASS group was more significant than that in the Clear aligner group(P<0.05). After treatment, the probing depth (PD), bleeding index (BI) and gingival index (GI) levels of the two groups were significantly higher than those before treatment (P<0.05). There was no significant difference in PD, BI and GI between the two groups after treatment (P>0.05). After treatment, the bite force and chewing efficiency of both groups were significantly increased compared to pre-treatment (P<0.05), and the increase was more significant in the PASS group (P<0.05). After orthodontic treatment, the scores of the Oral Health Impact Profile-5 (OHIP-5) in both groups decreased significantly, and the decrease was more significant in the PASS group(P<0.05). CONCLUSIONS: The clinical efficacy of PASS appliance in the treatment of Angle Class Ⅱ malocclusion is good, which can effectively improve the soft and hard tissue indexes and masticatory function of patients, while the Clear aligner has little side effect on the periodontal tissue of patients, and the degree of oral health is better.

Key words: Angle Class Ⅱ malocclusion, Clear aligner, PASS appliance, Periodontal health, Masticatory function