Research On The Effect Of Modified Twin-block Appliance Combined With High Pull On The Occlusal Plane Of Skeletal â…¡ High Angle Cases

ObjectiveWith cephalometric analysis, compared with traditional Twin-Block appliance, this research aims to analyze the impact of modified Twin-bloc k appliance(MTBA) combined high-pull on the occlusal plane of patients with skeletal class Ⅱ high-angle malocclusion, further more,to discuss the impact of occlusal plane change on the appearance and function of patients and skeletal class Ⅱ high-angle malocclusion.MethodsClinical data of 30 patients with skeletal Ⅱ high-angle malocclusion during 05/2013-02/2015 in our hospital were collected. According to the order of admission, the patients were randomly divided into experimental group and control group,15 cases in each group. Control group (15 cases) patients used traditional twin-block appliance 24h/day (Adams-clasps were designed on maxillary first molars,mandibular first premolars and first molars.resin cap covered 1/3 height of mandibular incisors, double-bend labial arch was designed on maxillary anterior teeth.). The experimental group of 15 patients used the modified Twin-Block appliances (Adams-clasps were designed on maxillary first molars, mandibular first premolars and first molars, resin cap covered 1/3 height of mandibular incisors and 1/2 height of maxillary incisors, or root-control loops were designed on maxillary incisors, double-bend labial arch was canceled), with high pull on the maxillary anterior teeth (ring loops were designed for J-hook and high pull between maxillary lateral incisors and canines), with forces of 350g per side, applied 12-14h/day.Both groups got continuous treatment for 8 months. Pre-treatment and post-treatment X-ray cephalometric images were collected and analyzed. Using SPSS 19.0 software for all the data processing and comparison of experimental group and control group, to analyze the differences of occlusal plane change between two groups.ResultsAfter 8 months of orthopedic treatment, both experimental and control group have got obvious hard and soft tissue changes, and the appearance of patients have got improved.1. The comparison of pre-treatment and post-treatment cephalometric shows:SNB of control group increased 1.52° (P<0.05);SNB of experimental group increased 2.18° (P< 0.05).there was no significant difference between the two groups(P>0.05).2. SN-MP and OP-SN of experimental group decreased 1.18° and 4.74° on average(P <0.05), whereas the change of control group was not obvious, (P<0.05), The difference between two groups were statistically significant (P<0.05)3. U1-SN° of experimental group decreased 1.42° while IMPA increased 2.1 ° (P <0.05), Ul-SN° of control group decreased 2.86°and IMPA increased 1.86° (P<0.05).But the difference between two groups were not statistically significant (P>0.05)Conclusion1. Both the Modified Twin-block appliances and the traditional Twin-block appliances can promote the growth of the mandible.2. The modified Twin-block appliances can attain good vertical control of anterior maxilla. As the position of maxillary molars and anterior teeth were controlled, OP-SN and SN-MP decreased.furthermore, the profiles of patients with skeletal Class Ⅱ high-angle malocclusion were obviously improved.3. The upper incisors become slightly upright and the lower incisors get labial inclined after orthopedic treatment,no matter how we control.