Comparison Of Soft And Hard Tissue Changes By Three Kinds Of Extraction Treatment Patterns In Angle's Class Ⅱ Division 1 Malocclusion

Objective:To compare three treatment methods for dental or mild skeletal Angle's II1 patients with relative upright lower incisors , mild crowdity of lower arch but sever distal molar relationship and existence of third molars. Cephalometric evaluation is used to study the changes of soft and hard tissue and the position of lower third molars before and after three extraction pattern treatment.Methods:Select 45 dental or mild skeletal Angle's Class II division 1 patients with relative upright lower incisors , mild crowdity of lower arch but sever distal molar relationship and existence of third molars as A,B,C group. Group A contains 16 patients who extracted the upper first premolars and lower second premolars, Group B contains 14 patients who extracted the upper first premolars only, Group C contains 15 patients who extrated the upper first premolars and lower third molars. All groups were treated by Edgewise appliance, and maxillary headgear-facebow anchorage, while group C push molar distally by lip bumper. Cepholometric evaluation was used to assess the soft and hard tissue changes before and after the treatment. Then taking cephalmometric analysis and statistical analysis.Results: Three groups achieved normal overbite and overjet in anterior teeth; A group achieved neutral relationship in molars; B,C groups achieved totally distal relationship in molars, and had generated some changes as follow:1. After treatment group A U₁/NA,L₁/NB distance decrease 1.42mm,2.13mm more and U₁/SN,U₁/NA,L₁/NB,L₁/MP angle decrease 2.38°,2.81°,4.81°,5.56°more and UL/EP,LL/EP decrease more 1.29mm,1.30mm and nasolabial angle increase 2.46°more and LM₃-OP angle,LM₂-LM₃ angle decrease 7.22°,4.25°more relatively than group B.2. After treatment group A upper incisors retract 2.32mm more and lower incisors retract 1.96mm more and U₁/NA,L₁/NB distance,L₁/NB angle decrease 1.39mm,1.24mm,2.14°more than group C, but the soft tissue changes have no statistics sagnification. 3. After treatment group C the upper incisors retract(U₁/RL-A/RL)1.46mm(p<0.05) more,the lower first molar distal movement is 1.35mm more and UL/EP,LL/EP decrease 1.06mm,1.02mm(p<0.05) more and nasolabial angle increase 1.43°(p<0.05) more than group B relatively. In group B the L₁/RL-Pg/RL distance,L₁/NB angle,L₁/MP relatively increase 1.16mm,2.67°,2.25°more and than group C.Conclusion:1. After three kinds of extraction treatment, all patients can achieve normal occlusion and profile improvement.2.With only the maxillary first premolar extraction compared to extraction of maxillary first premolar and the mandibular second premolars and extraction of maxillary first premolar and the mandibular third molar after treatment, under the relatively more upright incisors, the incisors are more adduction and more, were to face more improvements. However, extraction of maxillary first premolar and the mandibular second premolar relatively longer treatment time.3.Compare to extraction of maxillary first premolar and the mandibular second premolar group, after the extraction of maxillary first premolar and lower third molar, the mandibular incisors retract less, but no difference in the face improvement, and the treatment time decrease.4. Compare to extraction of maxillary premolar, after the extraction of maxillary first premolar and lower third molar, lower anterior teeth are able to keep upright and upper incisors retract more, and would diminish the disvantage by lower third molar eruption.