[A study on the extraoral cervical traction in the treatment of skeletal Class II division 1 malocclusion in mixed dentition].

PURPOSE: To evaluate the effects of extraoral cervical traction on skeletal Class II division 1 malocclusion of early or late mixed dentition and discuss the optimal treatment timing. METHODS: The sample consisted of two groups of skeletal Class II division 1 malocclusion. One group with 11 cases was treated started in early mixed dentition while the other with 15 cases in late mixed dentition. All cases were treated with extraoral cervical traction headgear. Cephalometric analysis was conducted to evaluate the treatment effects. Student's t test was applied for statistical analysis. RESULTS: SNA, ANB and the length of maxilla (A-Ptm) were reduced and the inclination of maxillary incisor was decreased in both two groups. When comparing the two groups, it was found that the reduction of SNA was more notable, which means the inhibition of the maxilla was more evident in late mixed dentition. The difference was statistically significant (P<0.01). There was no significant difference on the distalization of the first upper molar between two groups (P<0.01). CONCLUSIONS: The extraoral cervical traction might be more effective in late mixed dentition to restrain maxillary growth in the treatment of skeletal Class II division 1 malocclusion.

[Timing of treatment with bite-jumping appliance in orthodontics].

Bite-jumping appliance is a rational appliance for patients with severe overjet and retrusive mandible. In the pubertal growth spurt of patient, the appliance has good effect on skeletal or dental Angle class II malocclusions. After functional treatment, the probability of orthodontic treatment and orthopedic surgery in adult can be reduced. However, the most suitable time to use the bite-jumping appliance has been discussed continuously in various studies. According to many studies related, this paper summarized the treatment time of the fixed and the removable bite-jumping appliances, and compared the advantages and disadvantages between them.

[Morphologic characteristics of anterior crossbite in early permanent dentition reviewed by superimposition on the template].

PURPOSE: To establish a computer-processing module to first, eliminate the factors which mislead the diagnosis of anterior crossbite and second, superimpose the individual tracing on the template to review the patient's morphologic characteristics. METHODS: First, the module would process the following steps:1.to create three templates; 2.to move the functional-shift-mandible posteriorly; 3.to standardize the potential of vertical dimension;4.to select a suitable template for superimposition; 5.to standardize the sizes of individual graph and template. Second, the module would process the five-step superimpositions: 1. X axis was superimposed and S were registered to measure the distances between Ptm points and Ar points on X axis; 2. X axis was paralleled and Ptm were registered to measure the distance between A points on X axis; 3. X axis was paralleled and A points were registered to measure the difference of anterior area between the mandibular graphs; 4.mandibular planes were superimposed and Po was registered to show the mandibular form variation; 5. Ar-Gn lines were superimposed and Ar was registered to measure the difference between the mandibular graphs. RESULTS: The module which could complete these steps was produced. With its help, the individual graph could be diagnosed with the position of maxilla and mandible, the amounts of maxillary discrepancy and jaws' dysplasia, the mandibular form and size variation. CONCLUSIONS: The module could eliminate the factors which mislead the diagnosis and review the morphologic characteristics of anterior crossbite in early permanent dentition.

[A clinical study of the changes of condylar position in class division 2 deep-bite patients after orthodontic treatment].

OBJECTIVE: To observe the effects of orthodontic treatment on the changes of condylar position in Class division 2 deep-bite patients. METHODS: 11 patients with Class division 2 deep-bite malocclusion were orthodontically treated, the changes of condylar position were evaluated by means of 3D-CT and Sam-diagnostic articulator. RESULTS: With the increase of inclination of upper incisors and opening bite, there were statistically significant changes of condylar longitudinal distance and condylar height in both sides, and retruded contact position-intercuspal position(RCP-ICP) discrepancy was significantly reduced. CONCLUSION: The condylar position in division 2 deep-bite patients could be orthodontically changed, moving anterior-inferiorly and approaching RCP.

[Agenesis and the morphology and site of other teeth in the permanent dentition].

OBJECTIVE: To Investigate the relationship among anodontia, anomalously shaped teeth and reduction of teeth crown. METHODS: The position and the number of congenitally absent teeth of 79 patients were analysed, as well as the abnormal morphology of other teeth. The width of the remained teeth was measured and compared with that of normal on base of patients being divided into four groups by the number and the position of agenesis. RESULTS: (1)Most of the congenitally absent teeth were upper lateral incisors and lower central incisors. (2) The congenitally absent teeth of upper central incisors, upper and lower first molars were rare. While in several cases, the central incisors were lightly pet-shaped. (3) There was no significant difference in teeth size between mild hypodontia groups and normal. As the incremental degree of hypodontia, anterior teeth tended to reduce, while the size of posterior teeth was relatively stable. Upper lateral incisors, lower canines, upper second premolars, upper and lower second molars accounted most in the anomalously shaped teeth which could be often found in patients with hypodontia. CONCLUSION: (1) number during evolution. (2) The developmental anomaly of teeth size, teeth morphology and teeth number might be a procedure of continuous variation and it might be different manifestation of the same mechanism.

[A cephalometric study of natural head posture and spinal position in malocclusions].

OBJECTIVE: The purpose of this cephalometric study was to compare the difference of NHP (natural head posture) and spinal position among malocclusions with different skeletal patterns. METHODS: 79 malocclusions aged from 12 to 16 were divided to several groups according ANB and NSL-MP. The features of head posture and spinal position were examined by comparing the groups and the statistical significant correlation among NHP, spinal position and craniofacial morphology was sought. RESULTS: NHP and spinal position was not the same in malocclusions with different NSL-MP, while was identical in malocclusions with different ANB. CONCLUSION: It is believed that there was correlation among NHP, spinal position and vertical, sagittal development of face rather than anteroposterior relationship between maxilla and mandible.

[A Study On Dental and Craniofacial Structure of Normal Shanghai Adults Occlusion-III The Analysis of Dental Capacity and Craniofacial Structure]

OBJECTIVE:To examine the relationships between dental capacity and cranioficial structures.METHODS:Models, posterioanterior and lateral cephalometric films of 90 adults with normal occlusion in Shanghai area were measured and analyzed.RESULTS:The canine width of lower arch extended an important influence on the upper and lower arch. The dental capacity was highly correlated not only with the width and depth of cranioficial structure but with the height as well. The database of Coben analysis for normal Shanghai adults occlusion was established.CONCLUSION:The growth between dental and cranioficial structure was harmonized in three dimensions.