Abstract: PURPOSE: To explore the effects of different orthodontic appliances on the clarity of Mandarin speech and the error rate of consonants in orthodontic patients. METHODS: A total of 89 orthodontic patients treated in Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine from January 2024 to September 2024 were included. According to the type of appliance, the patients were divided into three groups: metallic appliance group, ceramic appliance group and invisible aligner group. Speech assessment was performed before, immediately after appliance placement and 1 month after appliance placement, respectively, and the speech clarity and consonant error rate of the three groups were compared. RESULTS: An immediate decrease in speech clarity was observed with all three types of appliances(P<0.001). However, there was no significant difference between the three groups of patients in the changes of speech clarity, both immediately after wearing and one month after wearing the appliances. The error rates for /j/, /x/, /s/, /zh/, /ch/ and /sh/ in the metallic appliance group were higher immediately after wearing the appliance than before wearing them, but returned to baseline after 1 month; the error rates of /q/, /z/ and /c/ had not returned to baseline levels even after one month. In ceramic appliance group, the error rates for /j/, /q/, /x/, /c/, /zh/, /ch/ and /sh/ were higher immediately after wearing the appliance than before wearing them, but returned to baseline after one month. The error rate for /z/ had not returned to baseline levels even after one month. The error rates for /j/, /q/, /zh/, /ch/ and /sh/ in the invisible aligner group were higher immediately after wearing the appliance than before wearing them, but returned to baseline at one month. The error rates for /x/, /z/, /c/, and /s/ had not returned to baseline levels even after one month. The incidence of new speech errors for /z/ immediately after wearing the invisible appliance was higher than that of the metal and ceramic appliance groups(P<0.05), but there was no significant difference in other consonant error rates among the three groups(P>0.05). CONCLUSIONS: The placement of metal, ceramic and invisible aligner can all lead to an immediate decrease in speech clarity for patients, with no significant differences among the three types of appliances. After wearing for one month, speech clarity of the three groups showed improvement. In terms of the incidence of newly occurring consonant errors, only the /z/ sound demonstrated a significant difference immediately after wearing, with the invisible aligner group exhibiting a higher error rate compared to the metallic and ceramic group.

Key words: Phonetic function, Speech clarity, Orthodontics, Appliance