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 evaluate the effects of fixed inclined bite plate on jaw bone and dentition in juveniles with Class Ⅱ division 1 malocclusion.Methods: Eighteen patients(10 male and 8 female aged 11.5～13.8 years old) were treated with fixed inclined bite plate for bite-opening, twelve patients(6 male and 6 female) were involved as the control. Cephalograms were taken before and after the treatment.Results: After treatment ANB was significantly reduced and mandibular development was improved; AFH and PFH were significantly increased; the first molar in mandible was siginificantly elongated.Conclusion: Fixed inclined bite plate is effective in the improvement of sagittal skeletal relationship and in the orthodontic treatment in the juveniles with Class Ⅱ division 1 malocclusion.

Objective:To study the effects of unilateral posterior crossbite on masticatory muscle functions pattern by using electromyography(EMG).Methods:20 subjects(11 males and 9 females)with unilateral posterior crossbite were selected.Subjects were instructed to stay mandibular postural position and to make maximum bite in intercuspal position(ICP)and bilateral chewing.EMG data of the left and right masseter and anterior temporalis muscles were recorded.Asymmetry index of masseter muscles(ASMM) and asymmetry index of temporalis muscles(ASTA)were calculated and compared.20 subjects with individual normal occlusion were used as control.Results:Compared to control group,masseter and temporal muscle activities in unilateral posterior crossbite group were lower in maximum bite and bilateral chewing;The activities of two muscles at crossbite side were lower than that at noncrossbite side.Under maximum bite and bilateral chewing,ASMM and ASTA in unilateral posterior crossbite group were significantly higher than those in control group;ASMM and ASTA in Subjects with one posterior tooth crossbite is lower than subjects with several teeth crossbite.Conclusion:It can be suggested that unilateral posterior crossbite may damage the function of mastication muscle.

Implant anchorage depressed the elongated opposed teeth to prepare enough space for the mandibular dentition.Finally,a better dental implant prosthesis can be achieved.

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