The Effect Of Orthognathic Surgery On The Speech Of Patients With Skeletal Class Ⅲ Malocclusion

PURPOSE: To investigate the change of the anatomical structure of pharynx in patients with skeletal class Ⅲ malocclusion before and after orthognathic surgery due to the movement of maxilla and mandible,which changed the position of oral organs such as soft palate and tongue body.Changes in the anatomical structure of the pharynx have an impact on the patient’s voice.The in-depth study of the characteristics and influencing mechanisms of voice changes in patients with skeletal Class Ⅲ malocclusion before and after orthognathic surgery is to better restore the patient’s voice function and perform postoperative rehabilitation training.This research will positively help the design of orthognathic surgery and the treatment of postoperative pathological speech.METHODS: Craniofacial CT scan and speech data were collected from 31 patients with skeletal Class III malocclusion before and 3 months after surgery.The collected CT data were imported into Dolphin 11.95 software,and the three-dimensional reconstruction of the patient’s airway was carried out through the software reconstruction function.The items measured and analyzed by the software were the distance(L1)and cross-sectional area(S1)from the lower edge of the soft palate to the posterior pharynx wall,the distance(L2)and cross-sectional area(S2)of the airway marked by the upper margin of the epiglottis,and the volume of oropharynx and laryngopharynx.The lateral cephalogram was created by the Build X-Rays Tool function of Dolphin 11.95 software,and 9 landmarks were selected for cephalometric analysis.The nine landmarks are SNA,SNB,ANB,NA-PA,Y angle,OB,OJ,OBJ and NLA.Speech data were analyzed objectively and subjectively by Computerized Speech Lab 4500 b and professional speech doctors.The abnormal pronunciation of the patients was recorded by three professional doctors,and the average value of the listening results was taken as the subjective evaluation of the patients’ speech.The objective analysis is to analyze the frequency and bandwidth of the vowel formant(/a/,/i/,/u/),the lower limit frequency,the energy value and the spectrogram of the of the consonant(/x/,/s/,/z/,/c/,/zh/,/ch/)through the computer speech workstation.Statistical analysis was performed using SPSS 24.0 procedure.RESULTS: The distance from the lower edge of the soft palate to the posterior pharyngeal wall,the shortest distance from the posterior margin of the tongue to the posterior pharyngeal wall and its corresponding cross-sectional area were significantly different from those before surgery(P<0.05).The changes of SNA,SNB,ANB,OJ,and OBJ before and after surgery were significant in our patients.Importantly,the speech intelligibility of orthognathic patients before and after surgery changed significantly subjectively(P<0.05).Objectively,the postoperative vowels /a/B2,B3,B4,/i/B1,B2,/u/B1,B2 and B4 of the patients were significantly different from those before surgery.There was no significant difference in the lower limit frequency of the consonants /x/,/zh/,/s/,the energy value of/zh/ and the grammatical form of /z/ before and after surgery.The maxillary advancement distance is highly correlated or significantly correlated with △ S1,△ VOP,and voice changes(r=0.734;0.706;0.882).CONCLUSIONS: The orthognathic surgery restored the normal position of the upper and mandible of the patients with skeletal class III malocclusion,improved the anatomical structure of the vocal organs and the position of the tongue body,so as to improve the postoperative speech of the patients.