0.05). Conclusion: The measurements of molar distal movement on model are smilar to those on cephalometric radiograph.

Objective: To evaluate the effect of a new method to treat early primary crossbite . Methods: 20 cases (2.8～6.5 years old ) with anterior crossbite were treated by bonding appliance combined with protracting mask. Cephalometric radiographs were taken and analyzed before and after treatment. Results: On average,in all the 20 cases the maxilla were moved 2.06 mm forward ,mandibular were turned 2.45?downward and backward ,the anterior crossbite was corrected and the face profile was improved satisfactorily.The treatment was conducted for 1.7 months on average. Conclusion: Using bonding appliance combined with protracting mask to treat early primary crossbite can achieve good effects for young children .

objective: To evaluate the effect of Quad Helix appliance in expanding narrow dental arch. Methods: 12 cases were treated by Quad Helix appliance. The effect was evaluated by measurement of the dental arch. Results: The dental arch of all the patients was expanded in half a year.The width between the maxillary first molars increased by 8.95 mm, and the width between maxillary first premolars increased by 5.7 mm. The average time of expanding was 20.75 weeks, the expanding efficiency was 0.43 mm per week. Conclusion: Quad Helix is an effective orthodontic appliance for correction of narrow dental arch.

Objective:To study the technique of treatment of ma lo cclusion with congenital individual missing lower incisor . Method s: Ten cases of malocclusion(male 3, femal 7) with congenital missi ng lower incisor were selected. The casts and cephalograms of pretreatment and posttreatment were measured and analysed respectively. The malocclusions were corrected by changing the position of jaws and teeth. Stripping, extraction and so on were applied in the treatment for the achievement of normal overjet and ov erbite according to the Bolton index. Results: Intercusp al bite, normal overjet and overbite were achieved in the ten cases. The majorit y of lower anterior teeth were anteversion. The width between lower canines decr eased. Conclusion: Satisfactory occlusion can be achieve d by orthodontic treatment in the patients of malocclusion with congenital indiv idual lower incisor missing.

0.05) . Conclusion: Mini-implant can replace traditional anchorge composed of extraoral arch and Nance arch in the moving of cuspid distally.

Objective: To investigate the effect of orthodontic and surgical treatments of skeletal crossbite on the electromyographic activity of human masticatory muscles. Methods: Electromyogram was used to test the changes of the electromyographic activity of masseter muscles, temporal anterior and diagastric anterior in 20 patients with skeletal crossbite before and after treatments. Results: Orthodontic and surgical treatments showed different effect on the activity of masseter muscle, temporal anterior and diagastric anterior. The change of the activity of the masseter muscle was the most significant among them. But, during chewing the masseter muscle was less active after treatments. Conclusion: Abnormal activity of the masticatory muscles can be partly corrected by the orthodontic and surgical treatments. The treatments cannot fully recover the function of the masseter muscle.

Objective:To study the characters of perioral muscle p re ssure of the adult patients with skeletal crossbite. Methods:20 patients were diagnosed to be with skeletal crossbite. The perioral muscle press ures on upper and lower central incisors, first molars and cuspids were measured buccally and lingually at rest position. 10 health adults were served as the co ntrols. Results:The perioral force in skeletal crossbite group was larger than that in the control group on the correspondence area(P0.05). In the skeletal cross bite group, the perioral force on the mandibular area was larger than that on th e correspondence maxillary area(P0.05). The muscle pressure on the labial side was larger than that on t he lingual correspondence side in both groups(P

Objective: To evaluate the effects of the modified fixed r everse Twin-block appliance(TBA) combined with maxillary protraction appliance( MPA) in the treatment of early Angle Ⅲ skeletal anterior crossbite. Met hods:TBA combined with MPA was used in 15 growing subjects with early An gle Ⅲskeletal malocclusion (group TBA-MPA). Another 15 subjects with the same type of malocclusion were treated by MPA(group MPA). The effects of treatment we re studied by cephalometric measurments.Results:3-5 months afte r treatment SNB, B-Vert T, Po-Vert T,NPo-FH,Co-Po and 1-NB in group 1 were decreased more than those in group 2 (P0.05).Conclusion:Angle Ⅲ skeletal ante rior crossbite can be corrected successfully with reverse TBA combined with maxi llary protraction appliance by mandible retrusion and maxilla forward growth.

Objective:To evaluate the influence on root resorption after distalizing molars with face bow.Methods:15 cases whose molars were distalized with face bow were selected in present research. Root lengths were measured on pre-treatment and post-treatment dental films taken with the oral positioner. The distances of molar distalization were measured on cephalometric radiographs.The differences of the pre-treatment and post-treatment root lengths were evaluated by the Paired t-test.The correlation between the distance of molars distalization and the root resorption of the maxillary molars was analyzed with Pearson's correlation coefficients.Results:The root lengths between the pre-treatment and post-treatment showed a statistically significant difference(P

Objective:To investigate the indications of lower incisor extraction in orthodontic treatment of malocclusions. Methods:42 patients (males 16,females 26) were divided into four groups: abnormal Bolton index; class III malocclusions with anterior teeth cross bite; one congenital lower incisor losing; and anterior teeth area periodontal disease.One lower incisor extraction, one lower incisor and other teeth extraction and other accessorial therapy were used in the treatment. Results:According to these four different conditions, alternative treatment plans of lower incisor extraction should be determined. For the former two conditions, one lower incisor was extracted; A lower incisor and two maxillary first premolars were extracted in the third condition, in which lower canines and first premolars should be grinded to improve esthetics; In the last condition, some maxillary teeth need stripping besides extracting one lower incisor. All of the 42 cases achieved satisfactory results, normal overbite and overjet and stable occlusal relationship. Conclusion:To be well acquainted with the indications of the extraction of the lower incisor in orthodontic treatment of malocclusions can help to achieve satisfactory clinical effect.