Research on multi-class orthodontic image recognition system based on deep learning network model / 中华口腔医学杂志

Objective: To develop a multi-classification orthodontic image recognition system using the SqueezeNet deep learning model for automatic classification of orthodontic image data. Methods: A total of 35 000 clinical orthodontic images were collected in the Department of Orthodontics, Capital Medical University School of Stomatology, from October to November 2020 and June to July 2021. The images were from 490 orthodontic patients with a male-to-female ratio of 49∶51 and the age range of 4 to 45 years. After data cleaning based on inclusion and exclusion criteria, the final image dataset included 17 453 face images (frontal, smiling, 90° right, 90° left, 45° right, and 45° left), 8 026 intraoral images [frontal occlusion, right occlusion, left occlusion, upper occlusal view (original and flipped), lower occlusal view (original and flipped) and coverage of occlusal relationship], 4 115 X-ray images [lateral skull X-ray from the left side, lateral skull X-ray from the right side, frontal skull X-ray, cone-beam CT (CBCT), and wrist bone X-ray] and 684 other non-orthodontic images. A labeling team composed of orthodontic doctoral students, associate professors, and professors used image labeling tools to classify the orthodontic images into 20 categories, including 6 face image categories, 8 intraoral image categories, 5 X-ray image categories, and other images. The data for each label were randomly divided into training, validation, and testing sets in an 8∶1∶1 ratio using the random function in the Python programming language. The improved SqueezeNet deep learning model was used for training, and 13 000 natural images from the ImageNet open-source dataset were used as additional non-orthodontic images for algorithm optimization of anomaly data processing. A multi-classification orthodontic image recognition system based on deep learning models was constructed. The accuracy of the orthodontic image classification was evaluated using precision, recall, F1 score, and confusion matrix based on the prediction results of the test set. The reliability of the model's image classification judgment logic was verified using the gradient-weighted class activation mapping (Grad-CAM) method to generate heat maps. Results: After data cleaning and labeling, a total of 30 278 orthodontic images were included in the dataset. The test set classification results showed that the precision, recall, and F1 scores of most classification labels were 100%, with only 5 misclassified images out of 3 047, resulting in a system accuracy of 99.84%(3 042/3 047). The precision of anomaly data processing was 100% (10 500/10 500). The heat map showed that the judgment basis of the SqueezeNet deep learning model in the image classification process was basically consistent with that of humans. Conclusions: This study developed a multi-classification orthodontic image recognition system for automatic classification of 20 types of orthodontic images based on the improved SqueezeNet deep learning model. The system exhibitted good accuracy in orthodontic image classification.

Ability and inability of artificial intelligence in orthodontics / 中华口腔医学杂志

With the development of artificial intelligence (AI) technology, it has a wide range of explorations in orthodontics. AI has greater application prospects in precise measurement, multidimensional diagnosis, treatment planning and efficacy prediction. At the same time, there are certain limitations in the application of AI, such as risks caused by individual variability, black box properties and unclear delineation of medical responsibilities. This paper summarized the history and current status of AI applications in orthodontics and discussed future development trends, to provide reference for clinical orthodontics.

Integrated three-dimensional digital assessment of accuracy of anterior tooth movement using clear aligners / 대한치과교정학회지

OBJECTIVE: To assess the accuracy of anterior tooth movement using clear aligners in integrated three-dimensional digital models. METHODS: Cone-beam computed tomography was performed before and after treatment with clear aligners in 32 patients. Plaster casts were laser-scanned for virtual setup and aligner fabrication. Differences in predicted and achieved root and crown positions of anterior teeth were compared on superimposed maxillofacial digital images and virtual models and analyzed by Student's t-test. RESULTS: The mean discrepancies in maxillary and mandibular crown positions were 0.376 +/- 0.041 mm and 0.398 +/- 0.037 mm, respectively. Maxillary and mandibular root positions differed by 2.062 +/- 0.128 mm and 1.941 +/- 0.154 mm, respectively. CONCLUSIONS: Crowns but not roots of anterior teeth can be moved to designated positions using clear aligners, because these appliances cause tooth movement by tilting motion.

A novel protein-repellent dental composite containing 2-methacryloyloxyethyl phosphorylcholine / 国际口腔科学杂志·英文版

Secondary caries due to biofilm acids is a primary cause of dental composite restoration failure. To date, there have been no reports of dental composites that can repel protein adsorption and inhibit bacteria attachment. The objectives of this study were to develop a protein-repellent dental composite by incorporating 2-methacryloyloxyethyl phosphorylcholine (MPC) and to investigate for the first time the effects of MPC mass fraction on protein adsorption, bacteria attachment, biofilm growth, and mechanical properties. Composites were synthesized with 0 (control), 0.75%, 1.5%, 2.25%, 3%, 4.5% and 6% of MPC by mass. A commercial composite was also tested as a control. Mechanical properties were measured in three-point flexure. Protein adsorption onto the composite was determined by the microbicinchoninic acid method. A human saliva microcosm biofilm model was used. Early attachment at 4 h, biofilm at 2 days, live/dead staining and colony-forming units (CFUs) of biofilms grown on the composites were investigated. Composites with MPC of up to 3% had mechanical properties similar to those without MPC and those of the commercial control, whereas 4.5% and 6% MPC decreased the mechanical properties (P<0.05). Increasing MPC from 0 to 3% reduced the protein adsorption on composites (P<0.05). The composite with 3% MPC had protein adsorption that was 1/12 that of the control (P<0.05). Oral bacteria early attachment and biofilm growth were also greatly reduced on the composite with 3% MPC, compared to the control (P<0.05). In conclusion, incorporation of MPC into composites at 3% greatly reduced protein adsorption, bacteria attachment and biofilm CFUs, without compromising mechanical properties. Protein-repellent composites could help to repel bacteria attachment and plaque build-up to reduce secondary caries. The protein-repellent method might be applicable to other dental materials.

Reliability assessment and correlation analysis of evaluating orthodontic treatment outcome in Chinese patients / 国际口腔科学杂志·英文版

This study aimed to assess the reliability of experienced Chinese orthodontists in evaluating treatment outcome and to determine the correlations between three diagnostic information sources. Sixty-nine experienced Chinese orthodontic specialists each evaluated the outcome of orthodontic treatment of 108 Chinese patients. Three different information sources: study casts (SC), lateral cephalometric X-ray images (LX) and facial photographs (PH) were generated at the end of treatment for 108 patients selected randomly from six orthodontic treatment centers throughout China. Six different assessments of treatment outcome were made by each orthodontist using data from the three information sources separately and in combination. Each assessment included both ranking and grading for each patient. The rankings of each of the 69 judges for the 108 patients were correlated with the rankings of each of the other judges yielding 13 873 Spearman rs values, ranging from -0.08 to +0.85. Of these, 90% were greater than 0.4, showing moderate-to-high consistency among the 69 orthodontists. In the combined evaluations, study casts were the most significant predictive component (R(2)=0.86, P<0.000 1), while the inclusion of lateral cephalometric films and facial photographs also contributed to a more comprehensive assessment (R(2)=0.96, P<0.000 1). Grading scores for SC+LX and SC+PH were highly significantly correlated with those for SC+LX+PH (r(SC+LX)vs.(SC+LX+PH)=0.96, r(SC+PH)vs.(SC+LX+PH)=0.97), showing that either SC+LX or SC+PH is an excellent substitute for all three combined assessment.

Effect of orthodontic force on expression of Asporin after tooth auto-transplantation: an experimental study in Beagle dogs / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effect of orthodontic light force on the expression of Asporin, bone morphogenetic proteins-2 (BMP-2) and alkaline phosphatase (ALP) after auto-transplantation.</p><p><b>METHODS</b>Thirty-two maxillary and mandibular incisors in four 13 month-old male Beagle dogs were auto-transplanted to the other side of the same jaw. The teeth were all endodontically treated and divided into four groups, control (group 1) and three experimental groups (groups 2, 3 and 4).In control group, the teeth were unloaded. In the other three experimental groups, continuous force was applied in the 1st week (group 2), 2nd week (group 3) and 4th week (group 4) after auto-transplantation, respectively. The dogs were sacrificed in the 8th week. The mRNA expressions of Asporin,BMP-2 and ALP were examined by real time PCR. The expression of periodontal ligament associated protein-1 (PLAP-1) was examined by Western blotting. The data were statistically analyzed using SPSS 17.0 and one-way analysis of variance (ANOVA).</p><p><b>RESULTS</b>In group 3, the expression of Asporin mRNA (2.047 ± 0.281) was higher than that in the other three groups, while the expression of BMP-2 (1.358 ± 0.095) was lower than that in group 2 and control group (P < 0.05). The expression of PLAP-1 (1.054 ± 0.113) in group 3 was higher than other groups, while significant difference was found between any two groups.</p><p><b>CONCLUSIONS</b>Orthodontic force could stimulate the expression of Asporin and PLAP-1. The orthodontic force applied in the 2nd week after the tooth auto-transplantation, the expression of Asporin and PLAP-1 reached the highest level.</p>

Repeatability of three-dimensional measurements based on cone-beam CT images / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the repeatability of three-dimensional (3-D) cephalometric measurements for the clinical application of 3-D cephalometry.</p><p><b>METHODS</b>Forty-nine measurements that widely used in traditional cephalometric analyses were defined in 3-D cone-beam CT (CBCT) images. Three examiners identified landmarks on CBCT images of 17 subjects with normal occlusion, respectively, and 3-D measurements were exported automatically by software SimPlant. Inter-examiner reliability correlation coefficients (ICC) were obtained for all measurements.</p><p><b>RESULTS</b>Repeatability of 36 measurements was high (ICC value greater than 0.9), including SNA, SNB. Repeatability of 11 measurements was moderate (ICC value between 0.8 and 0.9), including CoL-GoL, CoL-MSP. Repeatability of 2 measurements was low (ICC value lower than 0.8), including Gn-MSP and MPR-MSP.</p><p><b>CONCLUSIONS</b>Most 3-D cephalometric measurements based on CBCT had high repeatability. However, some 3-D cephalometric measurements had limited repeatability.</p>

Bond strengths of customized titanium brackets manufactured by selective laser melting / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the bond strengths of customized titanium bracket manufactured by selective laser melting.</p><p><b>METHODS</b>Eighty human premolars which had been extracted for orthodontic purpose were collected and divided randomly (by random table) into two groups (customized bracket group and 3M bracket group, 40 molars in each group). The 35% phosphoric acid was used for etching and the brackets were bonded with 3M Unitek bonding adhesive. All bonded specimens were placed in saline for 24 hours at room temperature and were tested on DWD3050 electronic testing machine to determine the shear bond strength and tensile bond strength. After debonding, the adhesive remnant indexes (ARI) were recorded.</p><p><b>RESULTS</b>The shear bond strengths of customized brackets was 6.80 (6.20, 8.32) MPa, which was significantly lower than that of the 3M brackets [10.46 (9.72, 11.48) MPa] (Z = -3.463, P < 0.05). And the tensile bond strengths of customized brackets was (6.93 ± 1.21) MPa, which was significantly higher than that of the 3M brackets [(5.88 ± 1.23) MPa] (t = 2.81, P < 0.05). No significant difference was found in the ARI between two different kinds of the brackets.</p><p><b>CONCLUSIONS</b>The shear bond strength and tensile bond strength of both kinds of brackets were enough for clinic application.</p>

Application of integrated digital maxillodental model in computer aided design of individualized lingual brackets / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To create an integrated digital maxillodental model and to apply it in computer aided design (CAD) of individualized lingual brackets in order to align both crowns and roots without fenestration and dehiscence.</p><p><b>METHODS</b>Cone-beam computerized tomography (CBCT)-based maxillodental model and laser-scanned dental model were integrated by auto registration in 10 patients with malocclusions. The registration error was calculated automatically. Three observers tested the method independently. The inter-observer difference was investigated. An integrated model was selected randomly and the setup was created with roots and jaws in good relationship without fenestration and dehiscence. The individualized lingual brackets were designed by CAD on the setup.</p><p><b>RESULTS</b>No significant difference was found in inter observers (P > 0.05). The registration errors of maxilla and mandible were (0.144 ± 0.020) mm and (0.141 ± 0.022) mm, respectively. The digital individualized lingual brackets based on the virtual treatment in integrated digital maxillodental model were produced.</p><p><b>CONCLUSIONS</b>An integrated digital maxillodental model was created in good accuracy. By applying the integrated model, individualized lingual brackets were designed.</p>

Effect of orthodontic force on periodontal healing after autotransplantation: an experimental study / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of the continuous light force to the donor teeth on the periodontal healing after transplantation.</p><p><b>METHODS</b>Thirty-two maxillary and mandibular incisors in four 10-month-old male Beagle dogs were autotransplanted. The pulps were removed in all teeth. The teeth were divided into four groups, one control and three experimental groups. In control group (group 1), the teeth were unloaded. In the other three experimental groups, continuous force (0.49 N) was applied in the 1st (group 2), 2nd (group 3) and 4th (group 4) week, respectively. The dogs were sacrificed in the 8th week. The tissue blocks were demineralized and sectioned perpendicular to the long axis of the teeth. The histological analysis was made.</p><p><b>RESULTS</b>Histomophometric analysis revealed a significantly lower occurrence of replacement root resorption in the group 3 (2.1%) than in the control group (12.5%, P < 0.05). The significant lower incidence of replacement root resorption, and a higher surface and inflammatory root resorption were found in group 2 (6.3% and 68.8%) than in the control group (12.5% and 41.7%, P < 0.05). No significant difference was found between group 4 and control group (P > 0.05).</p><p><b>CONCLUSIONS</b>The orthodontic force promoted the regeneration of the periodontal ligament and prevented dentoalveolar ankylosis, whereas excessive initial force might cause root and bone resorption.</p>

Three-dimensional analysis of craniofacial growth in adolescents with normal occlusion in Beijing / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To analyze craniofacial growth three-dimensionally for adolescents with normal occlusion in Beijing.</p><p><b>METHODS</b>One hundred and twenty-six adolescents with normal occlusion were selected according to the criteria. The sample was divided into four age groups (53 within 4 years, 30 within 7 years, 27 within 10 years and 16 within 13 years). Information of growth was collected. Three-dimensional cephalometric system based on cone-bean CT was established.</p><p><b>RESULTS</b>From 4 to 13 years Co-A increased (14.55 ± 1.15) mm on average on the left and (13.66 ± 1.14) mm on the right, and Co-Gn increased (22.89 ± 1.40) mm on the left and (22.82 ± 1.38) mm on the right; and U1-NA increased (2.20 ± 0.44) mm on the left and (1.60 ± 0.46) mm on the right; and CoL-CoR and GoL-GoR increased (13.31 ± 1.21) mm and (18.59 ± 1.40) mm, and N-Me increased (18.03 ± 1.32) mm.SN-PP and SN-MPL basically remained unchanged.</p><p><b>CONCLUSIONS</b>Adolescents with normal occlusion in Beijing grew obviously in three-dimensions and developed harmoniously.</p>

Research on Chinese orthodontic specialists' subjective evaluation of orthodontic treatment outcome / 中华口腔医学杂志

<p><b>OBJECTIVE</b>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.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSIONS</b>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.</p>

A comparative study of mechanical properties of commercialized dental thermoplastic materials / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To compare the mechanical properties of different dental optimal material selection for orthodontic appliance.</p><p><b>METHODS</b>Four commercialized thermoplastic products under different test conditions, and provide the suggestion of thermoplastic products were tested. The tear strength, elongation at break and stress relaxation of these materials were measured under different test conditions.</p><p><b>RESULTS</b>The tear strength declined after thermoforming, and rose again after 2 weeks of distilled water immersion. The elongation at break rose after thermoforming, and declined after 2 weeks of distilled water immersion. No significant changes were observed for brand A under different test conditions. Brand A showed the slowest stress relaxation of 0.0148 N/s.</p><p><b>CONCLUSIONS</b>The mechanical properties of thermoplastic materials were influenced by environmental factors. Brand A exhibited optimal comprehensive properties.</p>

Establishment of the micro-stress sensor measurement system for invisible aligner technique / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To design and build the micro-stress sensor measurement system for invisible aligner technique.</p><p><b>METHODS</b>A measurement system based on silicon-on-insulator piezoresistive stress sensor was developed. A four-point-bending based experimental apparatus was constructed to calibrate the piezoresistive coefficients of this stress sensor. A chemical-mechanical polishing process was developed for thinning the stress sensor dies. A packaging solution using flexible printed circuit to get signals out was designed.</p><p><b>RESULTS</b>The developed silicon stress sensor chip was 7.0 mm × 6.0 mm × 0.1 mm in size, and 13 sensor rosettes and 4 calibration rosettes were fabricated in one sensor. And a main testing PCB and a Lab View program were designed to carry out the automation measurement of the stress sensor. The stress state during the process was obtained through this test system. And measuered the stress of the 13 sensor unit.</p><p><b>CONCLUSIONS</b>A stress measurement system was established for measuring stress during orthodontic treatment with invisable aligner.</p>

Three-dimensional digital dental model based on micro-CT / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To establish a three-dimensional digital dental model through scanning dental impression directly with micro-CT.</p><p><b>METHODS</b>The polyvinyl siloxane (PVS) impression of the plaster model was taken and scanned with micro-CT. VGStudio MAX and Imageware softwares were used to obtain the digital dental model.</p><p><b>RESULTS</b>The three-dimensional digital model was established successfully. The scanning layer was 90 µm.</p><p><b>CONCLUSIONS</b>A new way of establishing the digital dental models could be achieved with micro-CT.</p>

Properties of NiTi wires with direct electric resistance heat treatment method in three-point bending tests / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the mechanical properties of Ni-Ti wires with direct electric resistance heat treatment (DERHT) method in three-point bending tests.</p><p><b>METHODS</b>Two superelastic Ni-Ti wires (wire A: Smart SE, wire B: SENTALLOY SE, 0.406 mm × 0.559 mm) and 2 heat-actived Ni-Ti wires (wire C: Smart SM, wire D: L&H TITAN, 0.406 mm × 0.559 mm) were selected. They were heat-treated using the DERHT method by a controlled electric current (6.36 A) applied for different period of time [0 (control), 1.0, 1.5, 2.0, 2.5 seconds). Then, a three-point bending test was performed under controlled temperature (37°C) to examine the relationships between the deflection and the load in the bending of wires.</p><p><b>RESULTS</b>After DERHT treatment, the plateau in the force-deflection curve of superelastic Ni-Ti wires and heat-activated Ni-Ti wires were increased. When the wires were heated for 2.0 seconds and deflected to 1.5 mm, the loading force of A, B, C and D Ni-Ti wires increased from (3.85 ± 0.11), (3.62 ± 0.07), (3.28 ± 0.09), (2.91 ± 0.23) N to (4.33 ± 0.07), (4.07 ± 0.05), (4.52 ± 0.08), (3.27 ± 0.15) N respectively.</p><p><b>CONCLUSIONS</b>DERHT method is very convenient for clinical use. It is possible to change the arch form and superelastic force of NiTi wires. The longer the heating time is, the more the superelastic characteristics of the wires are altered.</p>

Evaluation of periodontal tissue during orthodontic tooth movement in rats: a micro-computed tomography study / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To observe the microstructure changes of rat alveolar bone around tooth root under orthodontic force loading.</p><p><b>METHODS</b>Ten 10-week-old rats were included in the study. Upper first molars were moved mesially with 0.196 N of force. The alveolar bone around the root of upper first molar was scanned by a micro-computed tomography scan system (SkyScan-1076) in different period after the initiation of orthodontic force loading (on the 3rd, 7th, 14th day after force loading) and analyzed by a specially-designed software to measure the microstructure parameters of alveolar bone (bone volume fraction, bone surface to volume ratio, structure model index, trabecular thickness, trabecular separation, trabecular number).</p><p><b>RESULTS</b>From the 7th day, bone volume fraction [(41 ± 14)%], structure model index (1.51 ± 0.52) and trabecular separation [(90 ± 30) µm] changed significantly in the compressive area compared with those [(64 ± 15)%, (0.51 ± 0.85), (56 ± 10) µm] on the 3rd day. From the 14th day, bone volume fraction [(78 ± 14)%], structure model index (0.28 ± 0.20) and trabecular separation [(29 ± 13) µm] changed significantly in the tension area compared with those [(67 ± 14)%, (0.40 ± 0.41), (48 ± 15) µm] on the 7th day. No difference on trabecular number was found between the compressive area and tension area (P > 0.05).</p><p><b>CONCLUSIONS</b>The significant resorption of the alveolar bone was observed on the 7th days in the compressive area and the deposition of the alveolar bone was observed on the 14th day in the compressive area after orthodontic force loading.</p>

Study on the thickness-change of different thickness thermoplastic materials after thermoforming and saliva immersion / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To survey and compare the thickness-change of different thickness thermoplastic materials under different test condition and make sure the relationship between the thickness-change and the material initial thickness in order to provide a guide in selecting the suitable thickness thermoplastic in practice.</p><p><b>METHODS</b>To choose Biolon, the thickness include 1.0 mm, 0.75 mm, 0.5 mm. Used Electron Vernier caliper to measure the thickness-change of different thickness thermoplastic materials under different processing mode. The data was analyzed by SPSS 10.0.</p><p><b>RESULTS</b>After thermoforming the thickness of thermoplastic became thinner, the thickness of Biolon 0.75 mm decreased by 0.14 mm, Biolon 1.0 mm decreased by 0.22 mm and Biolon 0.5 mm decreased by 0.14 mm. After saliva immersion the thickness became thicker. The thickness of Biolon 0.75 mm increased by 0.02 mm, Biolon 1.0 mm increased by 0.03 mm and Biolon 0.5 mm increased by 0.02 mm.</p><p><b>CONCLUSION</b>1)The influence of different processing mode to the thickness-change had relation to the material initial thickness. 2)The Biolon 0.75 mm had certain superiority in thickness stability compared to the homogeneous brand through the above research.</p>

Relationship between condyle movement and disc position in patients with Class II division 1 malocclusion / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the relationship between condyle movement and temporomandibular disorders (TMD) in patients with Class II division 1 malocclusion.</p><p><b>METHODS</b>Twenty patients (from 11 to 12 years old) with Class II division 1 malocclusion before treatment were collected. Computer aided diagnosis axiograph (CADIAX) and magnetic resonance images (MRI) were used to analyze the condyle movement between disc displacement and normal groups.</p><p><b>RESULTS</b>The sensitive values were found in open/close process in patients with disc displacement: Y [Left: (0.32 +/- 0.10) mm, Right: (-0.91 +/- 0.49) mm ], Z [Left: (4.20 +/- 0.70) mm, Right: (3.44 +/- 0.21) mm], sagittal condylar inclination (SCI) [Left: (32.48 +/- 7.70) degrees , Right: (33.47 +/- 12.60) degrees ] and horizontal condylar inclination (TCI) [Left: (-2.60 +/- 2.02) degrees , R: (-9.23 +/- 5.58) degrees ], and those items showed significant difference between two groups.</p><p><b>CONCLUSIONS</b>The side shift of condyle movement in maximum open/close process might be the inducement of disc displacement. It was revealed that the changes in condyle movement could give useful information in early stage of functional treatment.</p>

Occlusal contacts in intercuspal position after orthodontic treatment / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To observe the occlusal contacts in intercuspal position(ICP) in adolescent patients after orthodontic treatment.</p><p><b>METHODS</b>Fourteen adolescent patients after orthodontic treatment were selected as experimental group and 17 healthy adolescents and young adults with normal occlusion were selected as control group. The occlusal contact in ICP in the two groups were recorded with T-Scan II system and compared.</p><p><b>RESULTS</b>When the total of force (TOF) were 1/10 TOFmax, 1/4 TOFmax, 1/2 TOFmax, 3/4 TOFmax and TOFmax, the number of occlusal contacts in the anterior segment in the experimental group were 1.5(1.0), 3.0(1.3), 4.5(3.3), 5.5(3.0), 5.5(3.3), which were significantly larger than that in control group [0.0(0.3), 0.0(0.6), 0.3(0.5), 0.3(1.0), 0.0(1.8), P < 0.05]. There were no significant difference in the area of occlusal contacts in the posterior segment between experimental group and control group (P > 0.05). The center of force (COF) in the experimental group located significantly more mesially than that in control group. The value of ICP contact time in experimental group was 0.192(0.141) s and no significant difference was found between experimental group and control group [0.163(0.200) s].</p><p><b>CONCLUSIONS</b>Although the patients achieved normal occlusion after orthodontic treatment, their anterior teeth received more occlusal force than those in healthy adolescents and young adults with normal occlusion.</p>