[The effect of Frankel Ⅲ orthodontic appliance combined with lip muscle training in the treatment of malocclusion during mixed dentition].

Purpose: To exploring the clinical effect of lip muscle training combined with Frankel Ⅲ orthodontic appliances in correcting Class Ⅲ malocclusion during the mixed dentition period.

Methods: One hundred children with Class Ⅲ malocclusion during the mixed dentition period admitted to Hangzhou Greentown Stomatological Hospital from June 2018 to December 2022 were selected. The children were randomly divided into a combination group (treated with lip muscle training and Frankel Ⅲ orthodontic appliance) and a control group (treated with Frankel Ⅲ orthodontic appliance), with 50 cases in each group. X-ray cephalometric indicators, temporomandibular joint parameters, upper airway measurement parameters and 12 month follow-up of the two groups of children were compared before and after treatment. SPSS 21.0 software package was used for statistical analysis.

Results: Before treatment, there was no significant difference of SNA, SNB, ANB, U1-NA, L1-NB, ANS-Ptm, S-Ptm, Co Po, Co-S, MP-SN, MP-FH and NP-FH between the combination group and the control group (P＞0.05). After treatment, ANB, U1-NA, L1-NB and MP-SN in the combination group were significantly higher than those in the control group, while NP-FH were significantly lower than that in the control group(P＜0.05). Before treatment, there was no significant difference of the joint space, anterior joint space and posterior joint space between the combination group and the control group patients(P＞0.05); after treatment, the joint space and the joint space in the combination group were significantly higher than those in the control group(P＜0.05). Before treatment, there was no significant difference of Ba PNS, Ad1 PNS, Ad2 PNS, Mc1 Mc2, SPP-SPPW, U-MPW, PAS and V-LPW between the combination group and the control group(P＞0.05); after treatment, Ad2-PNS in the combination group was significantly higher than that in the control group(P＜0.05). After 12 months of follow-up, the recurrence rate of the combination group was 2.00%, which was significantly lower than that (16.00%) of the control group (P＜0.05).

Conclusions: The combination of lip muscle training and Frankel III orthodontic appliances is more conducive to correcting Class III malocclusion during the replacement period, improving upper airway morphology, and reducing the recurrence rate after treatment.