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[A cephalometric study on Twin-block appliance for treatment of early skeletal Class II malocclusion]
1Department of Orthodontics, School of Stomatology, Tongji University, Shanghai 200072, China.
Purpose:
To investigate the dentofacial morphological changes and the indication of Twin-block appliance for treatment of skeletal Class II malocclusion.
Methods:
Twenty-one patients (5 degrees < ANB < 10 degrees , 12 males,9 females) were recruited with an average age of 11.5 years.Lateral headfilm were performed for each patient before and after treatment with Twin-block appliance. Fifteen cephalometrics parameters were selected and measurement was performed. Paired t test and multiple regression analysis were used for statistical analysis.
Results:
After treatment SNB(degrees), (L1-MP) (degrees), (Co-Go) (mm),(Go-Gn) (mm),(Co-Gn) (mm),(Sn-A'-UL) (degrees), (LL-B'-Pos) (degrees) increased significantly(P<0.05) ; ANB(degrees), WITS, OJ(mm), (U1-SN)(degrees), (UL-E line)(mm), (LL-E line)(mm) decreased significantly(P<0.05). ANB(<) and (U1-SN)(<) before treatment were significantly related to reduction in overjet (y=-37.14+0.43 ANB+0.36 (U1-SN), r(2)=0.62); SNA( degrees ) and SNB( degrees ) before treatment were significantly related to reduction in (UL-E line) (mm) (y=-5.37+0.44SNA-0.37SNB, r(2)=0.53); (U1-SN) (degrees) and (L1-MP)(degrees) before treatment were significantly related to reduction in( LL-E line) (mm) (y=-7.65+0.18 (U1-SN )-0.09 (L1-MP), r(2)=0.58).
Conclusion:
Twin-block appliance can be used successfully for early treatment of skeletal Class II malocclusion. It is more indicated for patients with retruded mandible , more labially inclined upper incisors and more upright lower incisors.
