Effect Of Twin-block Combining Maxillary Expander On The Sagittal Direction Of Adolescent Class Ⅱ Patients

Background:Among oral and maxillofacial malocclusions,the incidence of Class Ⅱmalocclusion is higher.The main etiological mechanism is normal maxillary protrusion and mandibular retraction.Relative to the position of the skull base,the mandible is usually positioned posteriorly.When the mandible is retracted,the space between the cervical spine and the mandibular body will be reduced,causing the tongue and soft palate to tilt backward,increasing the chance of impaired respiratory function during the day,and can lead to snoring and obstructive sleep apnea syndrome(OSAS)),resulting in varying degrees of maxillofacial appearance and masticatory function etc.Therefore,it is necessary to use Twin-Block(TB)combined with maxillary expansion for early functional correction of adolescent patients with mandibular retraction and maxillary stenosis.Objective: To explore the effect of Twin-Block(TB)combined with maxillary expansion appliance on the changes of upper airway width and hyoid bone position for patients in Class Ⅱ Division 1 who are caused by mandibular recession and upper arch stenosis.Methods :22 adolescent patients with Class II 1 malocclusion who were treated in the Orthodontics Department of the Affiliated Stomatological Hospital of Anhui Medical University from January 2018 to October 2020 were selected,including 9 males and 13 females,aged(10.2-11.8 years old),average age(11±0.8 years old).The treatment time was 10-12 months with TB combined with an palatal expander.Observe and compare the changes of the upper airway and the position of the hyoid bone through the cephalometric lateral film before and after the correction,and perform statistical analysis.Results: After treatment,the upper airway changes,PNS-R,PNS-UPW were not statistically significant(P>0.05),and SPP-SPPW,U-MPW,PAS,and V-LPW increased significantly(P<0.05).Changes in the position of the hyoid bone,H-MP,H-FH,H-PNS,H-CVP were not statistically significant(P>0.05),H-RGn,[H-Or(hor)] were statistically significant(P<0.05).Conclusions :When using TB combined with an arch expander to treat patients in the Class Ⅱ Division 1 dentition stage with mandibular recession and upper arch stenosis,the upper airway can be significantly expanded at the level of the oropharynx and laryngopharyngeal,but in the expansion of the nasopharynx is not obvious.The position of the hyoid bone has an obvious tendency to move forward,but it does not move upward.