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Objective: To get individualized facial three-dimensional finite element (FE) model from transformation of a generic one to assist orthodontic analysis and prediction of treatment-related morphological change of facial soft tissue., Methods: A generic three-dimensional FE model of craniofacial soft and hard tissue was constructed based on a volunteer's spiral CT data. Seven pairs of main peri-oral muscles were constructed based on a combination of CT image and anatomical method. Individualized model could be obtained through transformation of the generic model based on selection of corresponding anatomical landmarks and radial basis functions (RBF) method. Validation was analyzed through superimposition of the transformed model and cone-beam CT (CBCT) reconstruction data. Pre- and post-treatment CBCT data of two patients were collected, which were superimposed to gain the amount of anterior teeth retraction and anterior alveolar surface remodeling that could be used as boundary condition. Different values of Poisson ratio ν and Young's modulus E were tested during simulation., Results: Average deviation was 0.47 mm and 0.75 mm in the soft and hard tissue respectively. It could be decreased to a range of +0.29 mm and -0.21 mm after a second transformation at the lip-mouth region. The best correspondence between simulation and post-treatment result was found with elastic properties of soft tissues defined as follows. Poisson ratio ν for skin, muscle and fat being set as 0.45 while Young's modulus being set as 90.0 kPa, 6.2 kPa and 2.0 kPa respectively., Conclusions: Individualized three-dimensional facial FE model could be obtained through mathematical model transformation. With boundary condition defined according to treatment plan such FE model could be used to analyze the effect of orthodontic treatment on facial soft tissue.

Objective: To analyze the results of multiple Chinese orthodontic specialists' subjective evaluation of orthodontic treatment outcome, to investigate the relevance of different experiment items and to explore the weight of each monomial material., Methods: As a randomized clinical trial, with six orthodontic treatment centers and Angle's classification being regarded as two stratification factors, it contained 108 cases with integrity data, which was random extracted from 2383 cases that received orthodontic treatment in six orthodontic treatment centers during the past five years, gathering post-treatment study casts, cephalometrics and photographs of 48 cases as the research subject. Similarly taking Angle's classification as a stratification factor, 108 cases were randomly divided into 9 groups. The randomization of sampling and grouping were both generated by a pseudo-random number generator. According to the monomial and combined subjects, 69 orthodontic specialists were regarded as the raters to rank the 12 cases in each group, and to judge whether the case was qualified., Results: Correlation analysis: the Spearman r between Post-M + C and Post-M + C + P and the Spearman r between Post-M + P and Post-M + C + P were both greater than 0.950. The Spearman r between Post-M and Post-P and the Spearman r between Post-M and Post-C were about 0.300. The Spearman r between Post-P and Post-C was 0.505. Regression analysis: the linear regression results: M + C = 0.782M + 0.308C - 0.150, M + P = 0.804M + 0.233P - 0.091, M + C + P = 0.764M + 0.243P + 0.131C - 0.291. The r(2) of above three models was greater than 0.9., Conclusions: It was applicable to use M + C and M + P instead of M + C + P. Study casts could not replace cephalometrics or photographs when doing subjective evaluation. Cephalometrics and photographs could not substitute for each other either. In the combined materials evaluation, model accounted for the largest percentage. Based on the regression model, for the greater part, the integration of several monomial materials could replace the combined material assessment effectively.

Objective: To investigate three-dimensional imaging registration and superimposition techniques in measuring the tip and torque change of upper canine, premolar and first molar after orthodontic treatment., Methods: Twenty-eight subjects (14 extraction cases and 14 non-extraction cases) with full records were randomly selected from the Department of Orthodontics, Peking University School and Hospital of Stomatology. The pre-and post-treatment upper dental casts were digitized with three-dimensional spot laser scanner and superimposed with reverse engineering software. The facial axis of the clinical crown (FACC) was transferred from post-treatment teeth to the pre-treatment teeth using three-dimensional imaging registration. The occlusal plane was constructed on the post-treatment upper digital cast and the tip and torque values were measured., Results: In the non-extraction group, the tip of the second premolar decreased by 1.5° (P < 0.05). The buccal crown torque of the first and second premolars increased by 5.1° and 4.2° (P < 0.05), respectively. In the extraction group, the lingual crown torque of upper canine increased by 3.8° (P < 0.05)., Conclusions: Non-extraction orthodontic treatment tended to tip the upper second premolar distally and increased the buccal crown torque of the upper premolars while extraction treatment increased the lingual crown torque of the upper canine.

Objective: To investigate the craniofacial and occlusal changes of Class III cases treated with Tip-Edge Plus Technique., Methods: Thirteen Class III patients (6 girls and 7 boys, mean age 14.9 years) with mandibular protrusion were selected. All the patients were four premolar extraction cases and treated with Tip-Edge Plus technique. Cephalometric analysis was performed to evaluate the changes before and after treatment., Results: After treatment, Wits changed from (-2.50 +/- 1.40) mm to (-1.00 +/- 0.85) mm and ANB changed from (-0.61 +/- 1.41) degrees to (1.31 +/- 1.66) degrees (P < 0.05). UL-E and LL-E were decreased significantly from (7.55 +/- 1.24) mm to (4.82 +/- 1.05) mm and from (10.16 +/- 2.43) mm to (6.03 +/- 2.01) mm respectively (P < 0.01). The incisors were retracted. A remarkable soft tissue change was noted after the treatment. The difference between the distance of the upper lip and lower lip to SnPg' at the beginning of treatment changed from (-1.57 +/- 1.24) mm to (0.62 +/- 1.24) mm (P < 0.01). FCA changed from (2.62 +/- 1.53) degrees to (7.02 +/- 2.21) degrees ., Conclusions: With Tip-Edge Plus straight-wire technique and light continuous force, anterior teeth could be tipped distally and lingually quickly. The hard and soft tissues changed accordingly.

Objective: To evaluate the craniofacial and occlusional changes of Class II patients treated with Tip-Edge Plus technique., Methods: Twelve Class II patients (7 girls and 5 boys, mean age 14.3 years) with bimaxillary or maxillary protrusion were selected. All the patients were four first premolar extraction cases and treated with Tip-Edge Plus technique. Cephalometric analysis was performed to evaluate the changes before and after treatment., Results: After treatment, the profile was greatly improved. UL-E, LL-E were decreased significantly (P < 0.01) and incisors were retracted (P < 0.05). Upper molars moved forward slightly (P > 0.05)., Conclusions: The anchorage control in Tip-Edge Plus technique was effective without extraoral force, palatal arch and implants. Under very light force, the crown of anterior teeth tipped distally and lingually quickly. In the final stage, it was possible to achieve both desired root uprighting and crown torque.

Objective: To evaluate the effects of magnetic Twin-block appliance in the treatment of skeletal class II cases., Methods: The magnetic Twin-block appliance was embedded with two pairs of neodymium-iron-boron (Nd(2)Fe(14)B) rare earth permanent magnets in the upper and lower inclined planes of Twin-block appliance. The sample comprised of 13 skeletal class II patients in the late mixed or early permanent dentition treated by magnetic Twin-block appliance. Cephalometric films were taken before and after treatment. Helix CT images of the temporomandibular joint (TMJ) in all patients were examined before treatment (T1), during treatment (4 months after appliance placement, T2), after treatment (T3) and one year after treatment (T4)., Results: A double contour image was detected in the superior posterior part of the condylar head on the pseudo-sagittal reconstruction plane pictures of T2 in 11 patients. The double contour image could be observed in most patients as well. This image also exhibited on the pictures of T3 in several patients. On the pictures of T2 and T3 in some patients, interruption of cortical bone and "bifurcation phenomenon" of condyles were shown. Pictures of T1 and T4 were similar and no signs of remodeling of TMJ were observed. Cephalometric analysis revealed significant changes in the maxillofacial structure after treatment. The profile of patients improved., Conclusions: Bone remodeling of condyle occurred during the magnetic Twin-block treatment in class II patients. Magnetic Twin-block appliance was effective in the treatment of the growing skeletal class II patients.

Objective: To investigate the changes of available spaces of posterior arch segments in mandibular dentition from 13 to 18 years of age, which would provide information for space analysis of whole dental arch in adolescents., Methods: Twenty-six adolescents (12 males, 14 females) with normal occlusion were selected. All of the subjects had lateral cephalograms taken at the same time each year for 6 years. Longitudinal cephalometry and statistic analysis were conducted for all subjects., Results: Significant differences of available space were found between males and females. The growth of available space from 13 to 18 years of age was 5.12 mm in females and 5.79 mm in males. The completion of mandibular remodeling in males lagged behind females for about 1 year. No significant increase was found in girls beyond 16 years and in boys beyond 17 years. There was a 1.22 mm increase on each side per year in females until 16 years and a 1.45 mm increase in males until 17 years. The increase of available space was made partly by resorption of bone from the anterior border of the ramus and partly by mesial movement of the first molar. The mesial movement of dental arch was probably stimulated by the eruption of the third molars., Conclusions: The prediction of available space should be based on age and sex.

Objective: To investigate the longitudinal changes in crown inclination of permanent incisors and first molars in juveniles with normal occlusion., Methods: The untreated sample comprised 20 subjects (6 males and 14 females) with normal occlusion from the Research Centre for Craniofacial Growth and Development of Peking University School and Hospital of Stomatology. Crown inclination was evaluated with Biaggini Rayset in two stages, stage I with first molars and four incisors in occlusion (mean, 9.5 +/- 0.9 years) and stage II with the second molars in occlusion (mean, 13.7 +/- 1.3 years)., Results: No significant difference was found between sexual groups. The crown inclination of the upper central incisors decreased (P < 0.001). The crown inclination of the lower central and lateral incisors increased (P < 0.01 and P < 0.05, respectively). The crown inclination of maxillary molars decreased with growth (P < 0.001), whereas that of mandibular molars increased with growth (P < 0.001)., Conclusions: Maxillary molars tended to become upright lingually, whereas mandibular molars upright buccally with growth.

Objective: Three-dimensional (3-D) facial images are very useful for orthodontic diagnosis. Three-dimensional facial imaging system (DSC-2) based on phase measuring profilometry (PMP) was used to obtain images and tested for accuracy., Methods: Geometric strips (20 mm in width) was used to test the accuracy of the obtained images. Three-dimensional images of plaster head model with marker of 5 mm x 5 mm were taken by DSC-2 three-dimensional facial imaging system. The difference of measurements was compared between both methods. Measurements were repeated twice by three different doctors., Results: The average value of width in 3-D mode was 19.5 mm. No significant difference was found, compared with actual width (20 mm). There was no significant difference between computer measurement and manual measurement of the plaster head model (P > 0.05)., Conclusions: DSC-2 three-dimensional facial imaging system was accurate and reliable to obtain 3-D facial images.

Objective: To investigate the dental compensation in different sagittal jaw relationships., Methods: One hundred and fifty-seven post-treatment cases with satisfied outcome were chosen. Computerized cephalometric analysis was performed to evaluate the sagittal jaw relationship. Incisor torque were measured based on study models. Correlation analysis was performed., Results: Compared with skeletal class I cases, the upper incisors of skeletal class III cases were more proclined, and lower incisors were more retroclined; the opposite result was found in skeletal class II cases. Dental compensation in class I cases took place primarily at lower incisors., Conclusions: Incisor torque control was important in patients with various sagittal jaw relationships.

Objective: To establish the normal MESH diagrams of Chinese in Beijing, and to build a computerized MESH analysis system for orthodontic practice., Methods: Twenty-eight subjects with normal occlusion were selected in Beijing and their lateral cephalograms were taken at the age of thirteen and eighteen, respectively. Individual MESH diagrams were then established for each subject mainly according to Moorrees' method from the cephalograms orientated in estimated natural head position. Male and female normal MESH diagrams were created. A computerized MESH analysis system was also developed., Results: The normal MESH diagrams of Chinese in Beijing, thirteen and eighteen years old respective, were established. The computerized MESH analysis system was constructed and used in orthodontic patients., Conclusions: MESH analysis is a proportional analysis method. It can show the results directly, succinctly and holistically. It is also a favorable complement and amendment to the commonly used angle and linear X-ray analysis methods.

Objective: To investigate the relapse of incisor alignment after orthodontic treatment and possible factors which may related to its stability., Methods: 72 finished cases with full records selected from orthodontic clinic of Peking University School of Stomatology composed the sample. The follow-up lateral head films and study casts were taken at least 2 years after orthodontic treatment. The cephalograms were measured by computerized program and the study casts measured by caliper., Results: The upper Irregularity Index decreased from (11.5 +/- 5.02) mm before treatment to (2.01 +/- 1.39) mm after treatment and then increased to (3.46 +/- 1.69) mm in the follow-up stage. The lower Irregularity Index decreased from (7.24 +/- 44.35) mm before treatment to (1.75 +/- 1.04) mm after treatment and then increased to (3.39 +/- 1.78) mm in the follow-up stage. The changes are significant statistically. The changes of jaw in the sagittal and vertical directions as well as the related changes of the position of lower incisors, the decrease of the lower canine arch width, Bolton Index and sex all have statistically significant relation with the changes of the lower Irregularity Index after retention., Conclusions: Compared with lower arch, the alignment in upper arch is more stable in the follow-up stage. The results suggest that some possible factors may have correlations with the change of lower arch crowding during the follow-up stage.

The authors made a thorough and careful study on the Begg Stage I appliance and established a model of mechanics in accordance with the actual situation of arch wire being activated and derived a mathematical formula based on the elastic small deflection theory. This study provides not only the basis of choosing intrusive-force value for individual arches, but also the possibility of analysing dynamically the changes of intrusive- force value in the process of bite opening.