| ObjectiveIt was well acknowledged that using maxillary protraction face mask treat the skeletal class III malocclusion with a retruded maxilla in the pubertal period. This study was conducted to examine the effect of maxillary protraction treatment with the intraoral appliance rapid maxillary expansion or labiolingual appliances on the development of the skeletal-dental structures and the soft tissue profile, and to evaluate the differences between the two groups.Material and Methods33 subjects from the Orthodontics department of Jilin University Dental Hospital were diagnosed as skeletal Class III malocclusions with maxillary retrognathism and anterior teeth crossbite ,absence of width deficiency , in the second or third stage according to the cervical vertebral maturation(CVM)method which means all the subjects in the peak of the skeletal maturity .They were treated by maxillary protraction face mask and divided into two groups according to the intraoral appliances used. Group I consisted of 14 subjects with rapid maxillary expansion appliances (RME) and group II consisted of 19 subjects with labiolingual appliances (La/Li). The RME group were told to activate the screw twice a day during the first week (one quarter one time), after then to use the protraction face mask. The La/Li appliance was constructed with a 1mm stainless steel arch (buccal and lingual), with two hooks in the maxillary canine region to attach the elastics, and the arch was soldered to the bands placed on the maxillary first molar and first premolar. The face mask was used for 12-14 hours with 400-450 gm force with a direction of downward and forward pull of 20-30°downward to the occlusal plane.Cephalometric radiographs were taken before treatment and just after correction of the anterior crossbite, and traced by one author to avoid interoperate errors. The reference points and reference lines are shown in Figure 3.1,The hard tissue measurements are shown in Figure 3.2,3.3,and soft tissue measurements in Figure 3.4,3.5. We also use the Holdaway soft tissue measurements to analyze the profile. The means and standard deviations of the changes in various measurements were obtained with SPSS 11.5 software. Paired-sample-T test was used to compare values at T1 and T2.Independent-sample- T-test was carried out to compare the treatment effects between two groups.Results1. The changes in RME appliance group I were statistically significant. For the skeletal effect, SNA, ANB,MP/SN,PP/FH,S-A,A-NFH,ANS-ME and Wits increased significantly, and PP /SN decreased significantly. For the dental effect, not only UIE-PTV,UM-PTV and U1/SN increased ,but also L1/MP decreased significantly; The ratio between upper incisor and A point mesial movement amount was 1.25,and the ratio between upper molar mesial movement amount and A point mesial movement amount was 0.45, respectively. For soft tissue effect , the Holdaway analysis showed the H angle increased and nose prominence decreased significantly; The conventional soft tissue measurements UL-EP,Ns-Sn-Pos increased obviously. There were no significant changes in the other measurements.2. The changes in La/Li appliance group II were statistically significant .For the skeletal effect, all the measurements showed the obvious change(p<0.001), SNA,ANB,MP/SN,PP /SN,S-A,A-NFH,A- PTV,Ptm-S,ANS-ME,Wits value increased significantly, and SNB , PP/FH decreased significantly. For the dental effect, not only U1-NA,UIE-PTV,UM-PTV,U1-PP increased, but also L1/MP decreased significantly; The ratio between upper incisor and A point mesial movement amount was 0.58,and the ratio between upper molar mesial movement amount and A point mesial movement amount was 0.28. For soft tissue effect, the Holdaway analysis showed nose prominence,Superior sulcus depth,upper lip thikness UL-UI decreased ,and the H angle,Sn-H,LL-H and Soft tissue chin thickness increased significantly ; The conventional soft tissue measurements LL-LI,UL-EP,LL-EP,Ns-Sn-Pos increased obviously. There were no significant changes in the other measurements.3.To compare changes of the treatment effect of maxillary protraction with RME and La/Li appliances, we found the skeletal-dental measurements ANB,S-A,A-PTV,ANS-Ptm,Wits,ANS-ME,UM-PTV,U1-PP changed more significantly in the La/Li group, and except the changes of superior sulcus depth in the soft tissue measurements was smaller in the La/Li group .There were no other differences.Conclusion1. The using of RME and La/Li appliances both could achieve the Maxillary Protraction effect to treat the patients with the skeletal class III malocclusion with a retruded maxilla. After maxillary protraction, the maxilla moves forward significantly, and the mandibular growth was restricted with clockwise rotation. The anteroposterior relationship was improved, and the class III concave profile turned to straight.2. The labiolingual appliance could induce more significant skeletal effect than the rapid maxillary expansion appliance, and less dental effect. The two appliances have no significant difference in the soft tissue profile. The labiolingual appliance is beneficial to maxillary protraction in the condition without width deficiency. 3. The use of the Holdaway analysis method could estimate relationship of the upper lip, lower lip, pronasale, subnasale and the changes of the soft tissue thickness. In this study, we found the superior labiale sulcus moved forward following the A point, the upper lip soft tissue was more sensitive than the nasal soft tissue, and the superior labiale sulcus was more sensitive than the labiale superius. Holdaway analysis method is helpful to evaluate the treatment effect of the soft tissue, which is a simple and effective analysis method in the cephalometrics .It could be widely used for the clinical application.4. The structure of the labiolingual appliance is simple, which promotes the comfort in the mouth and the oral health. The manufacture of the labiolingual appliance is also simple, and the cost is cheap, so the labiolingual appliance is fit to apply in the clinic. |
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