A Study On The Curative Effect Of Twin Block Appliance In The Treatment Of Angle's Ⅱ~1 Malocclusion

Objective To study the effect of orthopedic treatment and the changes of dentition in the maxillary and mandible in patients with Class Ⅱ division 1malocclusion after treatment of Twin block appliance by cone-beam computed tomography and discuss the treatment mechanism of the Twin-block appliance from three-dimensional direction.Methods 31 patients with the average or low-angle Angle Class Ⅱ division1 patients in Pre-peak and peak period of growth and development in the orthodontic department of the Affiliated Stomatological Hospital of Nanjing Medical University were treated with Twin-Block appliances,including 17 males and 14 females,mean age 11.6 years old,which met the inclusion criteria.They were treated with Twin-block appliance.CBCT was taken before(T1)and after treatment(T2).Three-dimensional reconstruction of bone tissue and teeth,establishment of three-dimensional coordinate system,positioning of 22 landmarks,measurement of relevant indicators were performed using Dolphin 11.0.A paired t-test was performed on the indicators before and after treatment.P<0.05 was considered statistically significant.Data were statistically analyzed using SPSS 17.0 statistical software.Results : After the treatment of Twin-block appliance,the length of the mandibular ascending branch(Co-Go),the length of the mandibular body(Pog-Co),the anteroposterior diameter and the Internal and external diameter of the condyle in the largest interception area were significantly increased(P<0.01).The distance of B-coronal plane and the B-horizon plane increased and there was significantly different(P < 0.01),Pog-Id increased(P<0.05),suggesting that the growth of the mandible is forward and downward.The distance of the maxillary first molar root canal base to sagittal plane distance was increased in the left and right sides and theresults were significantly different(P<0.01).There was a significant difference in the decrease of ANB,U1/SN and the increase of MP/SN and L1/MP(P<0.01).Changes in the rest of the measurement items before and after treating with Twin-block appliance were not statistically significant.Conclusions After the treatment of patients with Class Ⅱ division 1malocclusion at the peak of growth and development with Twin-block appliance,CBCT three-dimensional measurement and Dolphin software three-dimensional reconstruction confirmed that it can effectively promote the growth and development of mandible,the proclination of lower anterior teeth.However,the inhibition of the maxillary is not obvious.It can only increase the width of the maxillary and retrocline the upper anterior teeth.