Changes Of The Morphology And Function Of Tongue And Oropharyngeal Airway In Adult Patients With Skeletal Mandibular Prognathism After Combined Orthodontic And Orthognathic Treatment

Skeletal mandibular prognathism is reffered to Class III jaw deformity in most case. The Skeletal mandibular prognathism is a kind of malocclusion which is difficult to be treated orthodonticly and easy to relapse, and also its prevalence is high in Chinese population. Ofen it needs combined orthodontic and orthognathic treatment to achieve satisfactory appearance and occlusion. Sagittal split ramus osteotomy is commonly used in oral and maxillofacial surgery clinic. The surgery can quickly changed the jaw deformities by draw back the mandible. However, the oral cavity is a complicated functional enviroment which is adjacent to nasal cavity, pharyngeal cavity and the dental arch. So when the mandible is drawn back, the anatomic structure may be influenced at the same time, and also the function be. So , when the oral functional space and pharyngeal cavity and the tongue are changed after the sugery, these changes may react the jaw bones, dental arch and even may cause the relapse. This study was based on the argumentation and used the advanced cephalometric analysis software to investigate the four points as follows:1. Changes of the soft and hard tissue and oral functional space in patients with skeletal mandibular prognathism after combined orthodontic and orthognathic treatmentTo analyse changes of the soft and hard tissue and oral functional space in patients with skeletal mandibular prognathism after combined orthodontic and orthognathic treatment, first we imported the X-ray cephalograms to the"onyx-ceph"software. The results illustrated that the mandibular skeletal measure values all diminished, that meant the mandible were drawn back obviously with regard to cranial base. The relationship between the maxillo-mandible improved after surgery that meant the sagital jaw deformity can be improved by the surgery and also the mental region and the condyle were drawn back. The vertical face height diminished, because many skeletal ClassⅢdeformities were also with high vertical facial height and it can be corrected by the surgery. After the the SSRO the oral functional space decreased.2. Changes of position of tongue, hyoid bone and oropharyngeal airway in patients with skeletal mandibular prognathism after combined orthodontic and orthognathic treatmentTo investigate the Changes of position of tongue, hyoid bone and oropharyngeal airway in patients with skeletal mandibular prognathism after combined orthodontic and orthognathic treatment, morphologically, we analysed the X-ray cephalometric analysis; functiacally, we used polysomnography(PSG) to evaluate the respiratory function. The results illustrated that the mental region moved backwards and upwards. Hyoid bone moved backwards and downwards. Retroposition of the tongue root downsize the pharyngeal cavity and airway. The distance between pendulous palate and pharyng-posterior wall decreased. That demonstrated pendulous palate was forced to retrude which made the sagital space of oral pharynx contract. We made regression analysis between the values of mental region changes and hyoid bone, tongue and airway space. Then we found that the backway of the mandible positively correlated to PAS area. All of the 25 patients had no OSAS before the orthognathic treatment neither the snore. However, after the sugery only one obese male encountered apnea hyponea index 5～20 per hour which meant mild case of OSAS. And a year later the symptom relieved in this patient.Taken together, it seems that after the SSRO, which retrudes the mandible and results in pharyngeal cavity decrease and hyoid bone descending, it is possible to cause the OSAS. So the quantitative analysis of the glossopharyngeum condition should be involved in the examination and treatment plan analysis before the treatment.3. Localizating Measurement of Human Tongue by Ultrasonic Imaging and analysis of normal human tongueTo investigate the tongue size, first of all we should establish the measurement system. Formerly, the problems of the measurement system is not accurate and hard to locate. In this study we used ultrasonic imaging along with the locating device to make the three dimensional locating measurement come true. It had no harm to the subjects with good accuracy and reproducibility. We measured the normal human tongue by using the locating system we established and obtained the reference value of the normal human tongue. And also obtained the correlativity between the tongue sizes of different sections and the dental arch sizes, that meant the internal association of tongue size and dental arch size ensured the dynamic balance of the muscles. Besides that we found that the tongue size is correlated to the body height, weight and head circumference. The anterior tongue length is negative correlated to the body weight, while other measurements weres possitive to the body height, weight and head circumference. That meant the tongue of obese patients had bad mobility and retroposition and relatively thickening and short, which made the airway narrow. All of these demonstrated that the obesities were liable to OSAS. Based on this we introduced tongue/dental arch ratio, and gained the range of tongue/dental arch ratio of the normal persons, which had some significance to the investigation of etiology and prognosis.4. Research on tongue size feature of mandibular prognathism and the stability of combined orthodontic and orthognathic treatmentTo investigate the tongue effects on the etiology and development of jaw deformity and the concordance between the tongue and oral cavity, pharyngeal cavity and dental arch, and to investigate whether the glossectomy should be suggested as one of the effective choices for the acquisition of post-treatment occlusal stability. The tongue size of skeletal mandibular prognathism is measured by the ultrasonic imaging tongue measurement system founded in our study. And the mean values of the paraters were obtained for different sexual groups. We compared the tongue size between skeletal mandibular prognathism and the normal occlusion group by paired comparision, in order to eliminate the effect of the sex, height and weight which could cause the deviation in the comparison. And we found that the difference between the tongue size in skeletal mandibular protrusion and normal occlusion was significant during the paired comparison. Therefore we concluded that the tongue size in skeletal mandibular prognathism was larger than in normal occlusion. And these results were much the same as the dental arch difference between the skeletal mandibular protrusion and normal occlusion. Then we calculated the tongue/dental arch ratio of the skeletal mandibular prognathism and found it increased, compared with the tongue/dental arch ratio of normal occlusion as control group. However, the tongue/dental arch ratio of the skeletal mandibular prognathism is also relatively stable. That meant the tongue posture was more anteriorly in the rest position and it could bring about a slight continuous force to the dental arch and mandible, which would cause the mandibular prognathism, and the bigger dental arch and the protrusive mandible match the bigger tongue, so the tongue/dental arch ratio could be stable. In other word, the tongue/dental arch ratio could reflex the degree of inconsistence. By analysing the tongue/dental arch ratio pre and post treatment, we would find the degree of inconsistence between tongue and dental arch, which could give some information for the doctor to make decision whether we should or not do glossectomy along with the orthognathic. And this surgery can also relieve the pressure of the anterior dental arch and the posterior pharyngeal cavity, and also prevent the relapse of the jaw deformity and the malocclusion.In summary, the tongue, pharyngeal cavity and oral functional space could be influenced after the SSRO, morphologically and functionally. Although this influence may not definitely cause the functional disturbance, it should be an risk factor. So we should analyse each patient and have a good choice of the orthognathic surgery and even glossectomy if it is necessary. We should attain good appearance and also oral facial functional balance to prevent relapse and functional disturbance. The aim is balance, concordance, stability.