Search

Objective: To evaluate the surgical technique and clinical effect of less invasive intrame-dullary nail fixation combined with titanium cable cerclage in the treatment of subtrochanteric fractures., Methods: A retrospective study was performed in 46 cases of subtrochanteric fractures in Peking University People's Hospital from January 2015 to December 2017. Among them, there were 14 males and 32 females, with an average age of (77.83±10.66) years (44-92 years); 17 cases on the left side and 29 cases on the right side. The causes of injury included crash from a height, traffic accident and accidental fall. According to Seinsheimer classification, there were 26 cases of type Ⅱ, 11 cases of type Ⅲ, 9 cases of type Ⅳ, and these cases were all closed injury. After admission, these patients underwent continuous tibial tuberosity bone traction to maintain the length and force line of the lower extremity, so as to reduce the difficulty of intraoperative fracture reduction. Anticoagulant therapy was given before operation to reduce perioperative thrombotic complications. All the patients were treated with less invasive intramedullary nail fixation combined with titanium cable cerclage. Operation time, blood loss during surgery, time of fracture healing were recorded, Harris and Sanders scoring system were used to assess hip function after operation at each follow-up time point., Results: All the included patients underwent surgery successfully. Average operative time and intraoperative blood loss of these patients were (131.09 ± 20.06) min and (191.96±111.03) mL, respectively. All the patients were followed up satisfactorily, with an average follow-up time of 28 months. The fractures received bone healing within 3-6 months, average hospital stay was (10.61±2.85) days. The Sanders score was excellent in 3 cases, good in 37 cases and common in 6 cases, with an excellent and good rate of 86.96%. The Harris score was excellent in 6 cases, good in 36 cases, with an excellent and good rate of 91.30%. There were no cases of wound infection, loss of reduction, nonunion of fracture or internal fixation failure. Hip pain symptoms were effectively relieved in most patients., Conclusion: Less invasive intramedullary nail fixation combined with titanium cable cerclage can obtain good alignment and stability of fracture ends, which is an effective method for the treatment of subtrochanteric fractures.

Objective: To investigate the clinical effect of a modified arthroscopic outside-in suture technique in the treatment of meniscus tear using a spinal needle., Methods: From January 2015 to October 2017, 95 patients treated with this method were followed-up. Among these cases, there were 36 males and 59 females. The age of the patients ranged from 16 to 77 years, (46.79±18.07) years in average. Among them, there were 28 patieats aged 16-35, 53 patients aged 36-65, and 14 patients aged over 65 years old. 28 cases were diagnosed with medial meniscus tear, 43 cases with lateral meniscus tear and 24 cases with both medial and lateral meniscus tear. Causes of the injury included sports, sprain, etc. According to Barrett standard, the clinical healing of meniscus tear was judged. Lysholm score, knee range of motion, visual simulation score (VAS) and magnetic resonance imaging (MRI) were used to evaluate the postoperative knee function and recovery of the patients., Results: The 95 patients were followed up for 22 to 36 months, with an average of (28.32±3.98) months. According to Barrett standard, 90 patients (94.7%) obtained meniscus clinical healing. Meniscal healing rates were 96.43%, 96.23% and 85.71% in the three age groups, respectively. The meniscal healing rate was lower in the elderly group, but there was no significant difference in statistical results ( P =0.262). Five patients had deep tenderness in the joint space of the injured side, and the overstretch test was positive. The preoperative and postoperative VAS scores, Lysholm scores and knee motion were compared in each group, and the differences were statistically significant ( P < 0.01). At the end of the last follow-up, there were no cases of knee joint effusion, swelling and interlocking, and the joint function was effectively improved in most patients. No surgical site infection, periarticular vascular/nerve injury or knotting reaction was found during the follow-up., Conclusion: This modified arthroscopic outside-in suture technique using a spinal needle has the characteristics of simple operation, small trauma and rapid recovery, and the mid-term follow-up results were satisfactory. Therefore, we consider this method to be a safe and efficient method for the treatment of meniscus anterior horn and body tear.

Objective: To investigate and analyze the complications of penile augmentation with acellular dermal matrix (ADM) and following management., Methods: This was a retrospective review of all patients who received penile augmentation with ADM between June 2016 and January 2019. The patients were evaluated with outpatient physical examination. Related complications and following management were summarized and analyzed., Results: Between June 2016 and January 2019, ADM was used as filling material on 78 patients (mean age: 31.14 years, range: 21-66 years), who were successfully received penile augmentation surgery. In the follow-up three months, the penile circumference was increased by 1.1 cm (0.5-2.1 cm) on average. The mean follow-up time was 12.20 months. In this study, there were 47 (60.26%, 47/78) patients with erectile discomfort, 91.49% (43/47) of whom manifested as erectile traction. There were 12 (15.38%, 12/78) patients with delayed healing, improved by daily regular dressing change. There were 10 (12.82%, 10/78) patients with unobvious augmentation effect. There were 9 (11.54%, 9/78) patients with stamp-like changes of ADM. There were 8 (10.26%, 8/78) patients with wound hematoma and 7 (8.97%, 7/78) patients with foreskin edema, relieved by compression with wrap. There were 4 (5.13%, 4/78) patients with wound infection and 3 (3.85%, 3/78) patients with skin necrosis of the dorsal side, which could be treated with ADM removal and repair surgery with bipedicle scrotal flap. And there were 2 (2.56%, 2/78) patients suffering psychological influence. Finally, most patients with various complications recovered successfully, however 7 patients (8.97%, 7/78) underwent ADM removal surgery., Conclusion: Using ADM as filling material could achieve positive effect in penile augmentation but the complications are common and cannot be neglected. Standardized surgical methods, rigorous postoperative care, and adequate notification with patients can effectively reduce the complications of penile augmentation with ADM. To treat properly and timely for complications can obtain satisfactory results.

Objective: To explore a cone beam computed tomography (CBCT)-independent method for mandibular digital dental cast superimposition to evaluate three-dimensional (3D) mandibular tooth movement after orthodontic treatment in adults, and to evaluate the accuracy of this method., Methods: Fifteen post-extraction orthodontic treatment adults from the Department of Orthodontics, Peking University School and Hospital of Stomatology were included. All the patients had four first premolars extracted, and were treated with straight wire appliance. The pre- and post-treatment plaster dental casts and craniofacial CBCT scans were obtained. The plaster dental casts were transferred to digital dental casts by 3D laser scanning, and lateral cephalograms were created from the craniofacial CBCT scans by orthogonal projection. The lateral cephalogram-based mandibular digital dental cast superimposition was achieved by sequential maxillary dental cast superimposition registered on the palatal stable region, occlusal transfer, and adjustment of mandibular rotation and translation obtained from lateral cephalogram superimposition. The accuracy of the lateral cephalogram-based mandibular digital dental cast superimposition method was evaluated with the CBCT-based mandibular digital dental cast superimposition method as the standard reference. After mandibular digital dental cast superimposition using both methods, 3D coordinate system was established, and 3D displacements of the lower bilateral first molars, canines and central incisors were measured. Differences between the two superimposition methods in tooth displacement measurements were assessed using the paired t-test with the level of statistical significance set at P<0.05., Results: No significant differences were found between the lateral cephalogram-based and CBCT-based mandibular digital dental cast superimposition methods in 3D displacements of the lower first molars, and sagittal and vertical displacements of the canines and central incisors; transverse displacements of the canines and central incisors differed by (0.3±0.5) mm with statistical significance., Conclusion: The lateral cephalogram-based mandibular digital dental cast superimposition method has the similar accuracy as the CBCT-based mandibular digital dental cast superimposition method in 3D evaluation of mandibular orthodontic tooth displacement, except for minor differences for the transverse displacements of anterior teeth. This method is applicable to adult patients with conventional orthodontic treatment records, especially the previous precious orthodontic data in the absence of CBCT scans.

Objective: To measure the resting pressure of the tongue body on the sagittal and vertical dimensions of the tongue anchorage pad (TAP), and to investigate the proper position of TAP as an anchorage., Methods: Nineteen volunteers with individual normal occlusion (4 males and 15 females, age 23-33 years) were recruited in the study. Individualized TAP was designed and made for each subject. On the sagittal dimension, the pressure along the midline at the level of the distal of the second premolar (PM2), the first molar (M1) and the second molar (M2) were measured. On the vertical dimension, pressures on TAPs with height of -3 mm, 0 mm, and 3 mm were measured, with 0 mm standing for the reference point recorded by the tongue position record. The tongue resting pressure of the volunteers in the upright position was measured by miniature sensors (FSS1500NS, Honeywell, USA) embedded in TAP. Nonparametric analysis was applied with the significant level of 0.05., Results: On the vertical dimension, the pressure obtained at the height of -3 mm, 0 mm, and 3 mm were 105.83 Pa, 167.75 Pa, and 254.25 Pa, respectively (P<0.001). On the sagittal dimension, the pressure detected at the level of PM2, M1, and M2 were 177.64 Pa, 126.72 Pa, and 109.37 Pa, respectively (P<0.001)., Conclusion: Tongue pressure rises significantly with the increase of TAP height. On the sagittal dimension, pressure decreases along the palatal midline in an anteroposterior direction. But in the clinical practice, we should also put comfort into consideration.

Objective: To assess the repeatability(intraobserver comparison)and reproducibility(interobserver comparison)of two different methods for establishing the occlusal plane on digital dental models., Methods: With Angle's classification as a stratification factor,48 cases were randomly extracted from 806 ones which had integrated clinical data and had their orthodontic treatment from July 2004 to August 2008 in Department of Orthodontics ,Peking University School and Hospital of Stomatology.Post-treatment plaster casts of 48 cases were scanned by Roland LPX-1200 3D laser scanner to generate geometry data as research subjects.In a locally developed software package,one observer repeated 5 times at intervals of at least one week to localize prescriptive landmarks on each digital model to establish a group of functional occlusal planes and a group of anatomic occlusal planes, while 6 observers established two other groups of functional and anatomic occlusal planes independently.Standard deviations of dihedral angles of each group on each model were calculated and compared between the related groups.The models with the five largest standard deviations of each group were studied to explore possible factors that might influence the identification of the landmarks on the digital models., Results: Significant difference of intraobserver variability was not detected between the functional occlusal plane and the anatomic occlusal plane (P>0.1), while that of interobserver variability was detected (P<0.001). The pooled experimental standard deviation the 6 observers established for the functional occlusal plane was 0.2° smaller than that of the anatomic occlusal plane.The functional occlusal plane's variability of intraobserver and interobsever did not differ significantly (P>0.1), while the anatomic occlusal plane's variability of the intraobserver was significantly smaller than that of the interobserver (P<0.001), with a 0.12° difference value of the pooled experimental standard deviation., Conclusion: When one observer measures a number of digital models,both the functional and the anatomic occlusal planes are suitable as a conference plane with equal repeatability. When several observers measure a large number of digital models,the functional occlusal plane is more reproducible than the anatomic occlusal plane ,but the difference is small.

Objective: To assess the correlations between objective measurements of 108 finished orthodontic cases and subjective assessments made by 69 orthodontic specialists, to explore the statistically significant measuring categories of cast and cephalogram and to validate the regression model., Methods: A stratified random sample of 108 cases was drawn from the large sample of 2 383 patients who finished orthodontic treatment between July 2006 and August 2008 in six orthodontic treatment centers around China. For each patient, the post-treatment information sources evaluated in this study included standardized plaster study casts and a lateral cephalometric X-ray image. These information sources were evaluated both singly and in combination by a panel of 69 orthodontic specialists. The average subjective grading scores of 69 orthodontists were regarded as the gold standard. Six examiners used the peer assessment rating (PAR) index and American board of orthodontics-objective grading system (ABO-OGS) to measure all the study casts respectively and three other examiners measured all the lateral cephalometric X-ray images by using customized software. The objective measuring data were correlated with the gold standard. The correlations between the objective measurement and the subjective evaluation were assessed, the statistically significant measuring categories of cast and cephalogram were explored and the regression model was validated., Results: The ABO-OGS scores of "occlusal relationship" correlated most strongly with the subjective scores of cast (r=0.655, P<0.01), and the secondarily correlated category with those were the PAR scores of "overjet" (r=0.525, P<0.01). The proclination of the lower incisors correlated most strongly with the subjective scores of cephalogram (r=0.446, P<0.01), and the secondarily correlated category with those was the protrusion of the lower lips (r=0.436, P<0.01). Nine components were predictive for the post-treatment model and lateral ephalometric film (Post-M+C) outcome: alignment (ABO-OGS), occlusal relationship (ABO-OGS), interproximal contact(ABO-OGS), L1/NB°, overjet (PAR), SNB°, occlusal contacts (ABO-OGS), U1/SN2° and centerline (PAR). These 9 components accounted for 72% of the variability in the average subjective grading scores., Conclusion: The objective regression model could replace the averaged opinion of Chinese orthodontic experts effectively, making objective assessment of orthodontic treatment outcome for Chinese patients.

Cone-beam CT (CBCT) was developed for the three-dimensional (3D) imaging of the maxillofacial area and has become popular in dentistry, orthodontics, and maxillofacial surgery. The advantages of CBCT include less radiation exposure (than conventional CT), less artifacts, and submillimeter spatial resolution. CBCT has been shown to produce accurate 3D images of the craniofacial region and a 1-to-1 image-to-reality ratio, which has greatly reduced errors of frontal cephalometry and improved our ability to diagnose asymmetry. Several new analyses to diagnose asymmetries on 3D images described in recent literature were reviewed, including 3D linear and angular measurements, mirror-image analysis (superimposition of the mirror image of the anatomically correct part of the anatomy over the deformity), 3D cephalometric analysis based on constructing an individual coordinate system for each facial unit or element (local coordinate systems) to differentiate them from the world coordinate system (whole head orientation), and method of application of asymmetry indices.

Objective: To investigate the agreement of subjective evaluation of orthodontic treatment outcome and to analyze possible factors that may be related to it., Methods: As a randomized clinical trial, with Angle's classification as a stratification factor, our study contained 48 cases with integrity data, which were randomly extracted from 806 orthodontic treatment cases in Peking University School and Hospital of Stomatology during July 2004 and August 2008, and gathered post-treatment study casts, cephalometrics and photographs of the 48 cases as the research subjects. Similarly with Angle's classification as a stratification factor, the 48 cases were randomly divided into 4 groups. According to the monomial and combined subjects, 12 clinicians were asked to act as the raters to rank the 12 cases in each group., Results: Overall, there were 1 584 pairings between the raters in the examination of evaluation. The mean Spearman r was 0.565 3 ± 0.239 9. Grouping factor was related to the agreement of subjective evaluation (P<0.05). In the third trial item-Post-M+P, the correlations were the greatest among the judge-pairs (P<0.001). The other five items were at the same agreement level. The level of orthodontic treatment outcome was a factor that influenced the agreement level of subjective evaluation (P<0.05). The score stability of the patients, whose treatment duration was longer than 2.5 years, was significantly higher than that of the patients whose treatment duration was between 1.5 years and 2.5 years (P<0.05). The following factors, such as Angle's classification, age of patients and whether the teeth was extracted or not, were the insignificant factors (P>0.05)., Conclusion: The average correlations present a moderate agreement level. Grouping, experimental item, the length of treatment duration and the level of orthodontic treatment outcome are the factors that affect the agreement of subjective evaluation. Several factors including Angle's classification, age of patients and whether the teeth is extracted or not, do not affect the agreement of subjective evaluation.

Objective: To assess the consistency of the subjective evaluation of malocclusion severity by the Chinese orthodontic experts., Methods: Sixty-nine Chinese orthodontic experts subjectively evaluated the malocclusion severity for 120 cases which were selected randomly from 6 University orthodontic clinics by checking each case's pretreatment records including study cast, lateral head film, panoramic radiograph, facial photographs and patient chart. Each orthodontist was asked to independently rate the severity of every case into five grades: mild, mildly moderate, moderate, severely moderate and severe. Rating data was finally gathered to evaluate the intra-judge's reliability and the inter-judges' consistency., Results: Weighted Kappa test revealed that 8.33% orthodontists showed excellent intra-judge's reliability (Kappa ≥ 0.81), 78.33% orthodontists showed good intra-judge's reliability (Kappa ≥ 0.61) and 96.67% specialists displayed general intra-judge's reliability (Kappa ≥ 0.41). And intra-class correlation coefficient demonstrated a high level of inter-judges' consistency (r=0.989, P<0.01)., Conclusion: Good intra-judge's reliability and inter-judges' consistency can be demonstrated in the subjective evaluation of malocclusion severity by the Chinese orthodontic experts, which could the basis for establishing the objective grading system of malocclusion severity.

Objective: To determine the accuracy of volumetric analysis of teeth in vivo using cone beam computed tomography (CBCT)., Methods: The physical volume (Vw) of 24 bicuspids extracted for orthodontic purposes (16 were imaged with the i-CAT and 8 with the CB MercuRay before extraction) was determined using water displacement technique. Corresponding pre-treatment CBCT image data were uploaded into Amira 4.0 for segmentation and radiographic volume (Va). All measurements were performed twice by two observers. The statistical difference between Vw and Va was assessed using a paired t-test. The intra- and inter-observer reliability was determined by calculating Pearson correlation coefficients and intraclass correlation coefficients (ICC)., Results: The overall mean Vw of teeth specimens was (0.553 + or - 0.082) cm(3), while the mean Va was (0.548 + or - 0.079) cm(3), (0.529 + or - 0.078) cm(3) for observer 1, and (0.567 + or - 0.085) cm(3) for observer 2. There were statistically significant differences between Va and Vw (P<0.05). Between two observers, Va had statistically significant difference (P<0.05). The inter- and intra-observers correlation coefficient for Vw was high. Lastly, surface smoothing reduced the volume by 3%-12%., Conclusion: In vivo determination of tooth volumes from CBCT data is feasible. The measurements slightly deviate from the physical volumes within -4% to 7%. Smoothing operations reduce volume measurements.

Objective: Cluster and discriminant analysis of the morphological characters of Angle's Class II malocclusion was performed using Procrusts standardization. The classification of craniofacial morphology with the help of morphometry and multivariate statistics was also discussed., Methods: A total of 894 class II patients were collected from the department of orthodontic, Peking University School and Hospital of Stomatology during 1997-2000. Using Procrusts standardization and cluster analysis, the samples were divided into different groups, discrimination equations were then established., Results: The samples were divided into 11 subdivisions by Procrusts superimposition and cluster analysis. Three discrimination equations were established. The accuracy rate of cross-validated grouped cases was 80.17%., Conclusion: Procrusts standardization had certain advantages in morphological classification; cluster analysis could be used in classification of Angle class II malocclusion; For different types, the differentiate rate was not the same; the discrimination equations was the foundation for future research.

Objective: To investigate hard-tissue changes in borderline cases with extraction and non-extraction during treatment and follow-up stages., Methods: Five associate professors, who were from Peking University School and Hospital of Stomatology, were asked to make judgment on the cases with full pre-treatment records for discriminating the borderline cases from extraction and non-extraction cases. Fifty-four borderline cases with full treatment records which had been out of treatment for at least 2 years were followed. Twenty-one cases with follow-up records were collected including 8 extraction cases and 13 non-extraction cases. Cephalometric measurements were preceded in IDAS (Image and Database Analysis System) software program., Results: In extraction group, significant changes of SNB, SNPg in A-P direction and that of ArGo/ANSMe, MP/SN in vertical direction were present during the follow-up stage, while the overjet was stable. In non-extraction group, only decrease of proclination of lower incisor and increase of overjet were present without any skeletal changes during the follow-up stage. In comparison of the two groups, no skeletal and dental changes showed statistically significant difference except for MP/SN and ArGoGn in pre-treatment stage, while dental characteristics in relation to upper and lower incisor (L1/NB, L1-NB, L1-AP, U1-AP, U1/L1) showed statistically significant difference between the two groups after treatment. But in follow-up stage, the skeletal and dental pattern tended to be similar for both groups only except for the proclination of lower incisor., Conclusion: The similarities of skeletal and dental pattern are demonstrated in extraction and non-extraction group before treatment. Dental changes are the major post-treatment changes in the two groups. In follow-up stage, counter-clockwise rotation of mandible is unique in extraction group, which is likely a helpful factor for stability of overjet, while lingual tipping of lower incisor in non-extraction group without skeletal changes may contribute to overjet relapse.

Orthodontics in China has experienced two important stages. At its early stage from 1950's to 1970's orthodontics was a division of prosthodontic department in China. There were 3 top professors in this field, who got partly training at one time or another in USA and returned to China working in Beijing Medical College, the Fourth Military Medical University and Shanghai Second Medical College. Among them, Professor Mao of Beijing Medical College was regarded as the father of Chinese Orthodontics. Removable appliance was the main tool at that stage and Prof.Mao brought forward Mao's Classification of Malocclusion which is still used in China. The rapid developing stage began in the 1980's when China opened its door to the world. More and more orthodontists got further training abroad and brought back advanced techniques since then. Up to now, we have already had more than one thousand of orthodontic specialists and established its own organization--the Chinese Orthodontic Society (COS), which holds domestic orthodontic meetings and organize its members to attend international meetings. Right now, almost all advanced techniques in diagnosis and treatment are adopted in China, including 3D imaging, self-ligating bracket appliance, and implant anchorage. Chinese orthodontists have started to present or publish papers in international meetings and journals and more than that, started to develop new appliances, such as Driving-Force Straight Wire Appliance, which has shown advantages in treating skeletal Class III malocclusion.

Objective: To classify the Angle I malocclusion subgroups using lateral radiographic films according to their ordinary coordinates and standardized coordinates converted by general procrusts analysis (GPA), and to compare the two kinds of classifications and their valne in diagnosis of malocclusion., Methods: 946 pretreatment lateral radiographic films of patients with Angle I malocclusion were chosen and their ordinary coordinates were acquired via soft ware. The ordinary coordinates were then converted into standardized coordinates by GPA. All of the films were classified by cluster analysis and discrimination analysis applying the upper two kinds of coordinates respectively., Results: (1) Twenty one subgroups were identified according to the ordinary coordinates of the chosen films with the total differentiate rate of 92.7% and leave-one-out differentiate rate of 68.4% (Classification A). Correspondingly, 20 subgroups were identified according to the standardized coordinates with the two differentiate rates of 87.8% and 71.9% (Classification B). (2) If the ordinary coordinates were discriminated by Classification B, the total differentiate rate and leave-one- out differentiate rate were 79.8% and 60.2 % respectively. If the standardized coordinates were discriminated by Classification A, the two differentiate rates were 79.8% and 60.2 % respectively. (3) There were some subgroups having the similar form in Classification A and their difference mainly arose from the difference of the patient age, while there were no such subgroups like that in Classification B. (4)The proportion of the largest subgroup in total subjects is 15.9% and there were 8 subgroups having the number of subjects over 40 in Classification A, while the corresponding proportion and number of subgroups were 74.7% and 2 in Classification B. (5)Classification A and Classification B were both suitable to classify a new subject, but Classification B was required to standalize all of the subjects onc again, which was very complex, while Classification A was more simplified., Conclusion: Classification A and Classification B are interrelated. GPA could concentrate the subjects in cluster analysis, which reduces some influence of the age to the classification, but the process to classify a new subject is very complex. Thus if quick diagnosis is needed in clinics, Classification A should be recommended, but the influence of the age should be noted.

Objective: Comparison of structural characteristic changes between deep overbite malocclusions with hyper- and hypodivergent skeletal pattern during treatment and follow-up stages. To discuss the difference between both in treatment mechanism and characteristic of relapse., Methods: 59 cases out of 162 finished patients with deep overbite malocclusion followed for more than 2 years, selected from orthodontic clinic in school of stomatology Peking University, were filtered by cephalometrics (MP-SN>40 degrees or <29 degrees)and then two groups were formed. The hyperdivergent group (MP-SN>40 degrees) comprised 10 cases and the hypodivergent group (MP-SN<29 degrees) comprised 9 cases. Measurements and statistics were performed upon the two groups., Results: After orthodontic treatment, the hyperdivergent group exhibited the extrusions of upper and lower molars [U6-PP increased from (10.69+/- 2.10)mm to (12.91+/-2.19)mm; L6-MP increased from (17.34+/-2.73)mm to (20.86+/-3.08)mm]. As to the skeletal change, a decrease of ANB angle from (5.86+/- 1.34) degrees to (4.62+/-1.67) degrees and NA-PA angle from (11.99+/-3.74) degrees to (8.76+/-4.45) degrees reflecting the sagittal change tendency from skeletal Class II to Class I. In vertical direction, the ratio of Ar-Go/ANS-Me increased from (0.58+/-0.03) to (0.62+/-0.05). Compared with the hyperdivergent group, the hypodivergent one only showed the extrusion of lower molars after treatment. The stability of overbite didn't show any statistically significant difference between two groups during the follow-up stage. Also in this stage the change of overbite in the hyperdivergent group was mainly due to the lingual inclination of upper incisors during the treatment stage and in the hypodivergent group it was due to the molar extrusion during treatment., Conclusion: The ramus showed great potential of growth in the hyperdivergent group during the treatment stage, which maintained the inclination of mandibular plane. The relapse of overbite was correlated with the changes of teeth during the treatment and follow-up stages.

Objective: To compare soft-tissue morphology changes by cephalometric measurements between extraction and non-extraction orthodontic treatment in borderline cases., Methods: The samples consisted of 33 cases selected as borderline cases by 5 orthodontic specialists. They were divided into 21 extraction cases (including 13 four first premolar extraction cases and 8 four second premolar extraction cases) and 12 non-extraction cases by checking patients' treatment records. Conventional cephalometric analysis was made to compare soft tissue structures before and after orthodontic treatments and the same comparison was made between two different extraction patterns., Results: No statistical difference was found in pretreatment soft-tissue morphology between extraction and non-extraction groups divided from borderline cases. The PosBs/FH of the four first premolars extraction group was smaller than that of non-extraction group, and the Ns-Sn-Pos of the four first premolars extraction group was smaller than that of four second premolar extraction group. None of the post-treatment soft-tissue measures showed significant statistical differences between four first premolars extraction group and non-extraction group, but there were 6 items showed significant statistical differences between four second premolars extraction group and non-extraction group. Compared with extraction and non-extraction treatments, the most significant soft-tissue changes were: PosBs/FH, LL-SnPos, and Bs-EP ., Conclusion: Although pre-treatment soft-tissue morphology of second premolar extraction group was close to that of non-extraction group, the post-treatment soft-tissue morphology of first premolar extraction group became closer to that of non-extraction group. Compared with non-extraction treatment, the more significant changes caused by extraction treatment were located in the lower lip and chin, but not the upper lips.

Objective: To study the 3D positional changes occurring to anchor molars of 37 patients treated with MBT appliance., Methods: Thirty-seven patients who needed maximum upper molar anchorage were divided into two treatment groups at random, group I was comprised of 19 patients whose anterior teeth were retracted en masse, and group II included 18 patients whose anterior teeth were retracted by two step. All the patients were treated with MBT appliance and headgear. Dental casts recorded before and after treatment were analyzed by YM-2115 three-dimensional digitizer and related software. The changes of anchor molar tip,torque and rotation were compared between the two groups., Results: During the treatment, average anterior movement of the upper first molars was 4.53 mm, average extrusion of the upper first molars was 1.53 mm; the crown of the upper first molar tipped forward (6+/-4) degrees,torque buccally (3+/-6) degrees,and mesiolingually rotated 3.15 degrees; In en mass group, the crown of the upper first molar tipped more mesially than the two-step group, and the difference was statistically significant., Conclusion: Almost all the upper first molars showed the tendency to rotate and tip mesially and torque bucally; there was no statistically significant difference between the two treatment groups when upper molar positional changes were concerned except for the mesial tip of the crown.