Objective:To evaluate the clinical effect of distalizing mandibular dentition with micro-implant in patients with skeletal classⅢmalocclusion.Methods: In the study, 20 patients with skeletal class Ⅲmalocclusion were selected.They are consist of 8 males and 12 female with an age range from 16 to 38 years old and an average age of (21.5±5.6) years.They were treated with straight wire technique and the implant were inserted into the mandibular external oblique line to distlize the lower dentition to a class Ⅰmolar relationships.Cephalometrics films were taken before and after treatment.The changes of hard tissue and soft tissue were analyzed by evaluating 26 measurement measurements.Results: ClassⅠmolar relationships were achieved, and the profile were improved after treatment.ANB increased by(0.80±1.02)°,Wits increased by (1.67±1.74) mm,after treatment(P<0.05).The lower dentition were significantly retracted after treatment with L1-NB distance decreased by(2.64±1.50) mm, P<0.05;the mesial buccal cusp and mesial root of the lower first molars were retracted by (3.26±1.95) mm and (0.79±1.27) mm respectively (P<0.05);the mesial buccal cusp of the lower second molars were retracted by (3.06±1.80) mm (P<0.05).After treatment, mandibular teeth got up-righted distally.From incisors to molar, L1/MP, L5/MP, L6/MP, L7/MP angle decreased by(6.37±8.53)°, (10.59±8.50)°, (11.48±7.22)°, (15.72±7.16)°on average respectively (P<0.05), all of those changes had the statically significant effects.Soft tissue change after treatment, the distance from lower lip to esthetic plane were decreased by (1.70±1.59) mm on average (P<0.05).Conclusion: Distalizing mandibular dentition with micro-implant can get an satisfying result in patients with skeletal class Ⅲmalocclusion, the lower teeth were retracted by controlled tipping movement.

Objective:To observed the longitudinal changes of the facial growth in vertical dimension in the Chinese adolescents with normal occlusion from 13 to 15 years old.Methods:The subjects were from Beijing area and consisted of 9 males and 14 females aged 12.5-13.5 years with Class I skeletal and dental pattern and without previous orthodontic treatment. Serial 2-year- annual cephalometric radiographs were taken and digitalized. Descriptive statistics for the absolute and incremental changes of the skeletal cephalometric measurements were conducted.Results:Significant gender differences in the changes of facial growth in vertical dimension from 13 to 15 years old were observed. Most of the skeletal measurements in males showed greater value than those in females. The number of the measurements which showed gender difference increased with age. The annual incremental changes of TAFH, TPFH, LAFH, U6-PP in males and those of TPFH and RH in females from 13 to 14 years old were greater than those from 14 to 15 years, However, the average increment of L6-MP in males and that of UI-PP, LI-MP, U6-PP and OB in females from 13 to 14 years old were smaller than those from 14 to 15 years old. There was no significant gender difference in TAFH/TPFH from 13 to 15 years of age. Gender difference from 14 to 15 years old was found in the growth of dental-alveolar height. The main dento-alveolar height changes happened in lower incisors and lower molars in males and in the region of upper molars and upper incisor in females.Conclusion:The skeletal facial growth in vertical dimension from 13 to 14 year old falls into the accelerating period. After 14 years old, the growth velocity is slowed down. There are significant gender differences in the skeletal changes of facial growth in vertical dimension from 13 to 15 years old. From 14 to 15 years old, the gender differences are mainly found in the growth of the dento-alveolar height.

Objective:To investigate whether the changes of anterior arch dimension have an impact on the precision of Bolton analysis. Methods:A mathematic-geometric model was used to evaluate the data. Results:The ideal anterior tooth size ratio may need adjustments, depending on the dimensions in radii of the upper and lower anterior dental arches. The ideal ratio is lower for dental arches with a high anterior curvature. There is a deficiency in the upper arch, a flatter anterior segment may compensate for some of the discrepancy and vice versa. Conclusion:An ideal Bolton value may not guarantee an ideal occlusion. Anterior tooth size ratio is not precise in predicting the anterior inter relationship post-treatment.

Objective:To design and assemble an orthodontic friction prototype testing apparatus and evaluate its performance.Methods: Simulating progressive tooth tipping movement,results of the opera-ting friction trials are reported at different archwire-bracket angulation.Results: An orthodontic friction testing apparatus was designed and developed,by which the complexity of tooth movements observed with in vivo sliding mechanics was simulated and a series of in vitro friction experiments were conducted.This friction testing apparatus enables previously unattainable testing of the orthodontic archwire-bracket-ligation interface.In the passive configuration or the active configuration with second-order angulation,the friction in sliding mechanics was measured.Conclusion: The apparatus presented has the ability to allow for a high standard of basic hypothesis testing,product development and performance evaluation with relative ease.Furthermore,it will be the prototype of a computer-controlled multifunctional friction testing device in the near future.

Objective:To evaluate evaluation of the changes of alveolar bone height in the periodontal patients with anterior teeth displacement before and after combined orthodontic periodontal treatment with circumferential fibrotomy. Methods: Totally 16 periodontal patients with anterior displaced teeth were analyzed after random clinical trialed as groups with and without circumferential fibrotomy of involving teeth followed by orthodontic intrusion. Evaluations of the changes of alveolar bone were given before and after treatment by means of periapical X ray film and CT scan of the involving teeth. Results: Orthodontic treatment with circumferential fibrotomy can increase the height of crest bone. Alveolar bone height was increased in the patients with circumferential fibrotomy followed by orthodontic intrusion of displaced anterior teeth. Alveolar bone height was increase by 1.2 mm on average in circumferential fibrotomy patient. In the patients with symmetric alveolar bone loss, 0.8 mm increase of alveolar bone height was observed following treatment. For the patients with asymmetric alveolar bone loss, 0.9 mm increase of alveolar bone height was detected in mild bone loss patients, but 1.4 mm and 2.2 mm increase of alveolar bone height were found in moderate and severe bone loss patients, respectively. For patients having the orthodontic treatment without circumferential fibrotomy, the alveolar bone height was increased by 0.1 mm only. Statistic significance was found between the circumferential fibrotomy group and non fibrotomy group. Conclusion: Combined orthodontic periodontal treatment with circumferential fibrotomy could correct the malpositioned teeth, and improve the periodontium conditions and gain the crest bone.

Objective:To evaluate the changes of different parts of upper airway after alternating rapid palatal expansion and constriction via three dimensional measurement, compared with the protocol of ra-pid palatal expansion alone.Methods: In the study, 36 patients with retrognathic maxilla were selected and randomized to either group A or group B.The patients in group A were treated with rapid palatal expansion alone.The patients in group B were treated with alternating rapid palatal expansion and constriction.Three dimensional analyses were performed on all pre-and post-treatment cone-beam computed tomography (CBCT) images with the software Dolphin.Results: Two subjects in group B were lost to follow up during the treatment.The gender distributions, ages and all measuring items before treatment had no significant difference between group A and group B (P>0.05).Nasal floor width, nasal lateral width, nasal volume, and nasopharynx volume increased significantly in each group after rapid palatal expansion alone or rapid palatal expansion and constriction (P<0.05).The variations of oropharyngeal volume and hypopharyngeal volume had no significant difference (P>0.05).No significant difference was observed in the nasal floor width and nasal lateral width increment among the anterior, median and posterior parts in each group either (P>0.05).No significant difference in all the measuring items was observed between the two groups (P>0.05).Conclusion:Alternating rapid palatal expansion and constriction could increase the volume of nasal and naopharynx cavities by the similar way of rapid palatal expansion alone, and had no obvious effect on oropharynx and hypopharynx cavities.

The level of serum soluble interleukin 2 receptor(sIL-2R)was studied in 29chronic persistent hepatitis (CPH) patients and in 18 normal individuals.It was found that sIL-2R level was significantly higher in the CPH patients than that in normal individuals(P

Objective: To evaluate the clinical application of MBT straight wire. Methods: 41 cases, 11 males and 30 famales aged 12-42 years old, with malocclusion were treated by MBT straight wire appliance in orthodontic clinics, follow-up was carried out. Results: Satisfactory effects were obtained in 11 completely treated cases, preliminary improvement of occlusion was observed in the other 30 cases being still in the treatment. Conclusion: MBT straight wire appliances may be used in the treatment of various malocclusion, but special consideration should be taken according to the type of occlusion in each case.

It is complicated to decide the treatment plan of hopeless anterior teeth in esthetic zone due to severe periodontitis, periodontal-endodontic combined lesion or teeth trauma.The optional treatment plan for this kind of teeth includes retention after periodontal treatment, extraction and implant treatment, extraction and prosthodontic treatment and so on.To make an appropriate treatment plan, patients'' periodontal conditions, periodontal biotype, local anatomy, esthetic demand, economic condition and social psychological status should be comprehensively considered.A combine of periodontal, endodontic and orthodontic therapy may achieve a good treatment effect in hopeless anterior teeth with severe periodontal destruction, tooth extrusion and occlusal trauma.In this case, a 20-year-old female who presented with symptoms of bleeding on brushing and upper incisors loosening for 1 month came to the Department of Periodontology, Peking University School and Hospital of Stomatology.The clinical examinations revealed that the patient''s right upper incisor had signs of mobility (Ⅲ°), intrusion of 1-2 mm, and probing depth (PD) of 9-10 mm.The periapical radiograph showed that the alveolar bone of right upper incisor absorbed horizontally to the apex.And the patients showed Angle Ⅱ° malocclusion with Ⅱ° overbite in anterior teeth and maxillary protrusion.A diagnosis of aggressive periodontitis and Angle Ⅱ° malocclusion was made.The treatment of this patient lasts for 5 years which include periodontal initial therapy, orthodontic therapy, guided tissue regeneration (GTR) of right upper incisor and supportive periodontal therapy and the clinical result is fine.A hopeless upper incisor was successfully retained and the longtime clinical condition was stable.The strategy of retention of hopeless upper anterior teeth, the relationship of periodontal treatment and orthodontic treatment, and the indications of periodontal and orthodontic combined therapy were also discussed on the basis of this case.Generally, the positive factors in retention of hopeless teeth includes young age, absence of systemic conditions, strong motivation for maintaining the tooth, single root anatomy, integrated dentition, good response to cause-related therapy, intrabony alveolar bone defect, thick periodontal biotype, and regular supportive periodontal therapy.And in the progress of orthodontic therapy, regular supportive periodontal therapy and good plaque control is extremely important.

Objective:This study was based on digital orthodontic diagnosis work flow for indirect bonding transfer tray model design and three-dimensional (3D) printing, and the aim of this paper was to inspect the dimensional accuracyof 3D printed brackets, which is the foundation of the follow up work and hoped that will illuminate the clinical application of the digital orthodontics work flow.Methods: The samples which consisted of 14 cases of patients with malocclusion from Department of Orthodontics Peking University were selected, including 8 cases with tooth extraction and 6 cases without tooth extraction.All the 14 patients were taken intra-oral scan (Trios 3Shape,Denmark)and cone-beam computed tomography (CBCT, NewTom 3G volumetric scanner, Aperio Service,Italy)shooting after periodontal treatment.STL data and DICOM data were obtained from intraoral scans and CBCT images.Data segmentation, registration, fusion, automatic tooth arrangement, virtual positioning of orthodontic appliance and conversion the coordinates of malocclusion model were all done with self-programming software.The data of 3D printing model with brackets on it were output finally and printed out with EDEN260V (Objet Geometries, Israel) to make indirect bonding transfer tray.Digital vernier caliper was used to measure the length and width of upper and lower left brackets and buccal tubes on those 3D models after removal of surrounding supporting material by ultrasonic vibration and water-spray.Intra-examiner reliability was assessed by using intra-class correlation coefficients (ICC), and one-sample T test was used to compare the measurements with the standard dimensional data of the brackets.Results: There were significant differences which range in 0.04-0.17 mm between the 13 items out of the 19 measurement items.Except for the length of the lower left premolars''brackets, mean values of the other items were greater than the test value.Conclusion: Although the measurement results in the width of brackets and the width and length of the buccal tubes obtained experimentally were slightly larger than the test value,this may not reduce the accuracy of indirect bonding procedure in clinic necessarily.Whether the differences which range in 0.04-0.17 mm would actually affect the retention and positioning of brackets needs to be confirmed by further studies.