Deep learning for virtual orthodontic bracket removal: tool establishment and application.

OBJECTIVE: We aimed to develop a tool for virtual orthodontic bracket removal based on deep learning algorithms for feature extraction from bonded teeth and to demonstrate its application in a bracket position assessment scenario. MATERIALS AND METHODS: Our segmentation network for virtual bracket removal was trained using dataset A, containing 978 bonded teeth, 20 original teeth, and 20 brackets generated by scanners. The accuracy and segmentation time of the network were tested by dataset B, which included an additional 118 bonded teeth without knowing the original tooth morphology. This tool was then applied for bracket position assessment. The clinical crown center, bracket center, and orientations of separated teeth and brackets were extracted for analyzing the linear distribution and angular deviation of bonded brackets. RESULTS: This tool performed virtual bracket removal in 2.9 ms per tooth with accuracies of 98.93% and 97.42% (P < 0.01) in datasets A and B, respectively. The tooth surface and bracket characteristics were extracted and used to evaluate the results of manually bonded brackets by 49 orthodontists. Personal preferences for bracket angulation and bracket distribution were displayed graphically and tabularly. CONCLUSIONS: The tool's efficiency and precision are satisfactory, and it can be operated without original tooth data. It can be used to display the bonding deviation in the bracket position assessment scenario. CLINICAL SIGNIFICANCE: With the aid of this tool, unnecessary bracket removal can be avoided when evaluating bracket positions and modifying treatment plans. It has the potential to produce retainers and orthodontic devices prior to tooth debonding.

A cone-beam computed tomographic study evaluating the efficacy of incisor movement with clear aligners: Assessment of incisor pure tipping, controlled tipping, translation, and torque.

INTRODUCTION: This retrospective clinical study aimed to evaluate the efficacy of different types of incisor movements with clear aligners in the sagittal plane. METHODS: Pretreatment and posttreatment cone-beam computed tomography (CBCT) scans were collected from 69 patients who underwent nonextraction treatment with clear aligners (Invisalign; Align Technology, San Jose, Calif). Integrated 3-dimensional models of the virtual incisor position (ClinCheck; Align Technology) and the posttreatment incisor position (from posttreatment CBCT scans) were superimposed over the pretreatment position (from pretreatment CBCT scans) using Mimics software (Materialise, Leuven, Belgium). On the basis of the location of the rotation center, incisors showing pure tipping (>10°), controlled tipping (>10°), translation (>1 mm), or torque (>10°) movements were selected. Efficacy was determined by comparing the predicted and achieved incisor movement, and differences with efficacy were analyzed using Kruskal-Wallis and Shapiro-Wilk tests (α = 0.05). RESULTS: In measurements for 231 incisors, the mean efficacy of incisor movements in the sagittal plane was 55.58%. The most and least predictable movements were pure tipping (72.48%) and torque (35.21%), respectively. Labial root movement was significantly more predictable than lingual root movement, and labial movement of the mandibular incisors was significantly easier than that of the maxillary incisors. The type of tooth movement achieved was different from the type designed. CONCLUSIONS: The efficacy of incisor movement in the sagittal plane using clear aligners varies with designed movement type, and labial root movement appears to be more accurate than the lingual root movement. The biomechanics of clear aligners remains to be further elucidated to achieve more predictable treatment results.

Cyclic tensile strain promotes the ECM synthesis of cranial base synchondrosis chondrocytes by upregulating miR-140-5p.

OBJECTIVE: This study aimed to explore the role of miR-140-5p in cranial base synchondrosis chondrocytes (CBSCs) under cyclic tensile strain (CTS). SETTING AND SAMPLE POPULATION: A total of 25 1-week-old Sprague Dawley rats from Shanghai Laboratory Animal Center, Chinese Academy of Sciences, were used. MATERIAL AND METHODS: The second passage of CBSCs was applied with CTS at 10% elongation (1 Hz) for 24 hours. MiR-140-5p levels in CBSCs were detected by qRT-PCR. The role of miR-140-5p in CBSCs was evaluated by transfection of mimics and inhibitor. RNA sequencing and online search of miRNA databases (TargetScan, miRDB and miRanda) were used in prediction of miR-140-5p targets. A luciferase reporter assay was applied to identify the target gene of miR-140-5p. RESULTS: Compared with the control, the expression of Col2a1 and Sox9 was significantly higher after CTS (P < .05). Also, CBSCs demonstrated higher expression of miR-140-5p after CTS loading for 24 hours (P < .05). Overexpression of miR-140-5p promoted ECM synthesis under CTS loading environment, while suppression of miR-140-5p inhibited the effect. Bloc1s2 was a putative target gene of miR-140-5p. CONCLUSIONS: The expression of ECM in CBSCs could be promoted by CTS and miR-140-5p might play a role in this process through targeting Bloc1s2.

Cone-beam CT evaluation of temporomandibular joint in permanent dentition according to Angle's classification.

OBJECTIVES: To compare characteristics of temporomandibular joint (TMJ) and related structures according to Angle class I, II1, II2, and III. METHODS: 123 Chinese patients (13-36 years old, 60 males, and 63 females) were classified in four groups according to Angle's classification: skeletal class I (31 patients), skeletal class II division 1 (30 patients), skeletal class II division 2 (30 patients), and skeletal class III (32 patients). Left and right TMJs of each subject were evaluated independently with cone-beam computed tomography (CBCT). The position of condyle in the joint fossa was analyzed according to Pullinger. RESULTS: There were significant differences between class III subjects and class I, II1, II2 in the superior joint space (p < 0.05). Compared with class II1, II2, and III subjects, the height and diameter of condyle in class I was significantly larger (p < 0.05). The width of joint fossa was significantly larger in Angle class III than in Angle class I, II1, and II2, while the depth was significantly smaller. The condyle position in class III subjects was more anteriorly displaced compared with that in class I subjects. In class II2 patients, the condyle position was mainly concentric and posterior. CONCLUSIONS: There are significant differences in condylar morphology, joint space, joint fossa morphology, and condylar position between different Angle classifications.

Influence of the three-dimensional printing technique and printing layer thickness on model accuracy.

OBJECTIVE: The accuracies of three-dimensional (3D) printed dental models using various digital light processing (DLP) and stereolithography (SLA) printers at different thicknesses were compared. MATERIALS AND METHODS: Based on digital dental models (originally digitized using R700; 3Shape, Copenhagen, Denmark), physical dental models were printed using three types of DLP printers: (1) EvoDent (UnionTec, Shanghai, China) with layer thicknesses of 50 µm and 100 µm; (2) EncaDent (Encashape, WuXi, China) with layer thicknesses of 20, 30, 50 and 100 µm; (3) Vida HD (Envisioned, Dearborn, MI, USA) with layer thicknesses of 50 and 100 µm. Models with the SLA printer Form 2 (Formlabs, Somerville, MA, USA) were printed with layer thicknesses of 25, 50 and 100 µm. All 22 printed models were converted to digital dental models using a D2000 model scanner (3 Shape, Copenhagen, Denmark) and compared three-dimensionally to the source files using Geomagic Qualify 12.0 (3D Systems, Rock Hill, SC, USA). RESULTS: The printing accuracy of all printers was higher at 50 µm. When the layer thickness was set at 100 µm, the printing speed and printing accuracy of DLP printer were both superior to those of the SLA printer. In all groups, the EvoDent 50 µm group had the highest consistency with the source files (mean absolute deviation of 0.0233 mm in the maxilla and 0.0301 mm in the mandible). While the accuracy of Form 2 100 µm group was the lowest (mean absolute deviation of 0.0511 mm in the maxilla and 0.0570 mm in the mandible). CONCLUSION: For the 3D printers studied, 50 µm was the optimum layer thickness for DLP technology, and the printing accuracy using SLA technology increased with decreasing layer thickness. The DLP technology also had higher printing accuracy at a layer thickness of 100 µm. EvoDent 50 µm had the highest and Form 2 100 µm the lowest printing accuracy.

[Effect of cyclic tensile stress on expression of type â ¡ collagen and Sox9 in rat cranial base synchondrosis].

PURPOSE: To establish an in vitro mechanical stimulation model of cranial base synchondrosis chondrocytes, and to study the effect of cyclic tensile stress on the main extracellular matrix of rat cranial base synchondrosis. METHODS: Cyclic tensile stress was imposed to the second passage of cranial base synchondrosis chondrocytes for 3, 6, 12 and 24 hours respectively by using a Flexcell Strain Unit-5000T(10% surface elongation, 1 Hz). After mechanical loading, the total RNA of the cells harvested from six-well BioFlex was extracted. Real-time quantitative RT-PCR was performed to quantify the mRNA levels of type Ⅱ collagen and Sox9. The data were analyzed with SPSS 17.0 software package. RESULTS: Compared with the control group(0 h group), the mRNA expression of type Ⅱ collagen was decreased after 3 hours of loading, but not statistically significant; While the expression of Sox9 decreased significantly (P<0.05). In the 6 h group, the expression of Col-Ⅱ and Sox9 decreased significantly (P<0.01 and 0.05, respectively). The expression of Col-Ⅱ and Sox9 increased in the 12 h group. The 24 h group showed significant increase in both type Ⅱ collagen and Sox9 (P<0.05). CONCLUSIONS: The results illustrate that cyclic tensile stress can affect the synthesis of the main extracellular matrix of cranial base synchondrosis in vitro. Expression of type Ⅱ collagen and Sox9 can be inhibited during early stage of mechanical loading. However, when loading time extends, the mechanical stimuli greatly promotes the expression of type Ⅱ collagen and Sox9. The reaction of Sox9 in this in vitro mechanical stimulation model happens earlier than that of type Ⅱ collagen.

Rapid maxillary expansion in alveolar cleft repaired with a tissue-engineered bone in a canine model.

This study aims to investigate the effects of orthodontic expansion on graft area of a tissue-engineered bone (TEB) BMSCs/ß-TCP, and to find an alternative strategy for the therapy of alveolar cleft. A unilateral alveolar cleft canine model was established and then treated with BMSCs/ß-TCP under rapid maxillary expansion (RME). Sequential fluorescent labeling, radiography and helical computed tomography were used to evaluate new bone formation and mineralization in the graft area. Hematoxylin-eosin staining and Van Gieson׳s picro fuchsin staining were performed for histological and histomorphometric observation. ALP activity, mineralization and the expression of osteogenic differentiation related genes of BMSCs that grew on the ß-TCP scaffold were promoted by their cultivation in osteogenic medium. Based on fact, TEB was constructed. After 8 weeks of treatment with BMSCs/ß-TCP followed by RME, new bone formation and mineralization of the dogs were markedly accelerated, and bone resorption was significantly reduced, compared with the untreated dogs, or those only treated with autogenous iliac bone. The treatment with both TEB and RME evidently made the bone trabecula more abundant and the area of bone formation larger. What is more, there were no significant differences between BMSCs/ß-TCP group and the group treated with autogenous bone and RME. This study further revealed that TEB was not only a feasible clinical approach for patients with alveolar cleft, but also a potential substituent of autogenous bone, and its combination with RME might be an alternative strategy for the therapy of alveolar cleft.

Amplification and up-regulation of microRNA-30b in oral squamous cell cancers.

OBJECTIVES: MicroRNAs (miRNAs) are negative regulators of protein coding genes which are frequently deregulated in mammary cancers. Over-expression of microRNA-30b (hsa-miR-30b) is implicated in tumour invasion and immunosuppression during metastasis. The chromosome locus of MIR30B gene, 8q24, is frequently amplified in oral squamous cell cancers (OSCCs). In the present study, we aimed to investigate the copy number variations as well as expression levels of MIR30B gene in OSCCs and analyse their correlation with tumour stage. DESIGN: Quantitative real-time PCR was performed to examine the copy number of MIR-30B gene as well as hsa-miR-30b expression in 107 OSCC samples with matched adjacent normal tissues. Proportional odds regression and two-way repeated measurement ANOVA were used to analyse the association between copy number variations (CNVs) and hsa-miR-30b expression. RESULTS: Copy number gains of MIR-30B gene were detected in a relatively large percentage of the OSCC samples (27.1%, 29 out of 107) and were correlated with tumour stages (p<0.001). MIR30B gene amplification also showed a close correlation with hsa-miR-30b over-expression in OSCCs (p<0.001). On the other hand, enhanced miR-30b expression was also detected in a group of OSCC samples with unaltered copy number of MIR30B gene. CONCLUSIONS: Copy number increase of MIR30B is frequent in advanced OSCC and is correlated with hsa-miR-30b over-expression. Sporadic OSCCs can exhibit different mechanisms of MIR30B regulation.

ERBB2 gene amplification in oral squamous cell malignancies: a correlation with tumor progression and gene expression.

OBJECTIVES: Chromosomal instability is hallmark of carcinoma. Amplification of chromosome 17q11-q12 is present in some oral squamous cell cancer (OSCC) cases. In this study, we investigated the copy number variations of ERBB2 gene, which is located at this locus in collected OSCC samples and their correlation with tumor progression and gene expression. STUDY DESIGN: Quantitative real-time polymerase chain reaction was performed to detect the copy number of ERBB2 gene and the mRNA expression in 92 OSCC samples with matched adjacent normal tissues (ANTs). Proportional odds regression and 2-way repeated measurement analysis of variance were used to analyze the association between copy number variations and mRNA expression of the targeted gene. RESULTS: Copy number gains of ERBB2 were detected in some of the OSCCs (19.6%, 18/92) and correlated with tumor stage (P < .001). Copy number gains of ERBB2 also showed a positive correlation with mRNA overexpression in OSCCs (P < .001). However, enhanced ERBB2 mRNA expression was also detected in a group of OSCC samples with unaltered copy number of ERBB2 gene (P < .05). CONCLUSIONS: Copy number increase of ERBB2 is observed in OSCCs and correlates with gene overexpression in these tumors. In addition, overexpression of ERBB2 is also observed in some OSCCs that lack copy number changes, indicating involvement of another mechanism.

Orthodontic tooth movement in alveolar cleft repaired with a tissue engineering bone: an experimental study in dogs.

Tissue engineering approaches have been successfully used in repairing bone defects and have become a viable alternative to autologous bone. The aim of the present study was to investigate if a construct of porous beta-tricalcium phosphate (ß-TCP) combined with osteogenically induced bone marrow stromal cells (bMSCs) could repair alveolar cleft, and allow for subsequent orthodontic tooth movement in a canine model. Twelve alveolar osteotomy surgeries in six animals were made bilaterally and randomly implanted by (1) tissue-engineered bone complex of bMSCs/ß-TCP (group A, n=4), (2) ß-TCP alone (group B, n=4), and (3) autologous bone obtained from iliac bone (group C, n=4). Contralateral alveolar defects were created in one animal and left untreated to serve as blank control to observe spontaneous healing of the defects. Sequential fluorescent labeling and radiographic observation was used to evaluate new bone formation and mineralization in each defect. Orthodontic tooth movement was initiated 8 weeks after surgical operation for 12 weeks, and then the dogs were sacrificed for histological and histomorphometric analysis. Results indicated that the tissue-engineered complex with bMSCs/ß-TCP dramatically promoted new bone formation and mineralization and achieved a favorable height of the repaired alveolar when compared with ß-TCP alone, which absorbed severely. The overall effect of the tissue-engineered bone was equivalent to autologous bone; the physiological function of the alveolar bone was restored by allowing the adjacent teeth to move into the newly formed bone in the grafted region. This study demonstrated that the tissue engineering bone from the combination of ß-TCP and bMSCs is a feasible clinical approach for patients with alveolar cleft and the subsequent orthodontic tooth movement.

[Morphological and histological adaptation after mandibular functional positioning only in vertical dimension].

PURPOSE: To elucidate the role of mandibular vertical functional positioning in condylar adaptive remodeling. METHODS: Forty female Sprague-Dawley rats at the age of 5 weeks were randomly divided into 4 control and experimental groups. All the animals were sacrificed on day 3, 6, 9 and 12 (n=5). Bite plates on upper posterior teeth were fitted on the experimental animals to induce functional repositioning of the mandible. Morphological and histological analysis was carried out to quantitatively analyze the amount of the adaptive changes of condylar cartilage. Independent-samples t test and One-Way ANOVA using SPSS11.0 software package were performed. RESULTS: Twelve days after mandibular vertical functional positioning the condylar height increased. Nine days after mandibular vertical functional positioning the thickness of prechondroblast layer and chondroblast layer increased significantly compared with control groups. However the thickness of hypertrophic layer decreased significantly after 6 days' mandibular repositioning. No change was found in the thickness of mesenchymal layer during the experimental period. CONCLUSIONS: Mandibular vertical functional positioning could enhance the growth of condyle. The resulted adaptive remodeling in condylar cartilage plays an important role in the treatment mechanism of mandibular deficiency via functional appliances.

[Bolton tooth-size discrepancy among different skeletal malocclusion groups].

PURPOSE: To evaluate the differences in tooth size ratios and distributions of Bolton anterior and overall ratios among different skeletal malocclusions. METHODS: 180 subjects were involved in this study, each malocclusion group consisted of 60 subjects(30 males and 30 females). The mesio-distal width from left first molar to right first molar was measured, Bolton anterior and overall ratios were calculated. Student's t test, ANOVA, LSD and chi2 test were performed for statistical analysis with SPSS15.0 software package. RESULTS: No statistically significant sex difference was found in anterior or overall ratio in any malocclusion. Significant difference was found for all ratios between skeletal Class III and skeletal Class I, so with skeletal Class II. No significant differences in all ratios between skeletal Class I and Class II were noted. Significant difference was found in the distribution of subjects with anterior and overall ratio discrepancies between skeletal Class III and skeletal Class II. CONCLUSIONS: The mean anterior and overall ratios for skeletal Class III malocclusions are significantly greater than those for skeletal Class I and Class II. The number of subjects with anterior ratio discrepancies for skeletal Class III malocclusions are larger than that for skeletal Class I and Class II malocclusion.

[Indications for non-extraction treatment of dental crowding with Damon appliance].

PURPOSE: To analyze the indications for successful non-extraction correction of dental crowding with Damon appliance. METHODSú 19 patients with non-extraction orthodontic treatment were reviewed. They had Class I skeletal pattern and both arches were treated with Damon 3 or Damon MX appliances. According to the initial diagnosis before treatment (T1), 7 cases needed extraction, but they rejected it. After correction of crowding (T2), they were allotted into either successful group or unsuccessful group. The successful group contained those subjects in whom the Z angle at T2 was no less than 70 degrees or that of T1. Others were allotted into the unsuccessful group. The dental casts and cephalometric radiophotographs were analyzed at T1 and T2. The difference between the two groups was analyzed with SPSS15.0 software package for Student's t test. RESULTS: There were 11 cases in successful group. All the 7 cases rejecting extraction were finally allotted into the unsuccessful group. No significant difference in upper arch perimeter and arch width was detected between the two groups at both T1 and T2. The upper and lower incisors and upper lip showed a more retruded position in successful group at T1, although they showed a similar amount of protrusion from T1 to T2 in both groups. The forward movement of lower lip was 3.4mm in the unsuccessful group, which was significantly larger than that of 1.6mm in successful group(P<0.05). Z angle decreased 10.7 degrees in the unsuccessful group, while no significant change was detected in the successful group. The Holdaway upper lip strain was comparable in two groups, but the successful group showed significantly less soft chin strain than unsuccessful group (P<0.05). CONCLUSIONS: Damon appliance can not rescue extraction cases. Straight soft tissue profile and upright incisor position are prerequisite for non-extraction treatment. And a harmonious chin and lip position is the key leading to the successful non-extraction treatment with Damon appliance.

[Evaluations of self-perceived orthodontic treatment need using 2 different scales in adolescents].

PURPOSE: To evaluate the self-perceived dental aesthetics through visualized analogue scale (VAS) and aesthetic component (AC) of index of orthodontic treatment (IOTN) among adolescents in Shanghai area. METHODS: The investigation was carried out among 302 students (148 boys and 144 girls) aged 11-13 years. Self-perception of the dental aesthetic appearance was evaluated through VAS and AC. Additionally, the objective dental aesthetics were scored by orthodontists using AC and the actual dental attractiveness satisfaction was determined by a simple question. The data was analyzed using SPSS11.0 software package for Spearman correlation analysis. RESULTS: Generally, no statistically significant sex differences were found in relation to the VAS score and SAC degree (P > 0.05). No correlation was found between actual dental attractiveness satisfaction and self-perceived AC grade (r = 0.04. P = 0.441). However, statistically significant, positive, strong correlations were found between the actual dental attractiveness satisfaction and VAS score (r = 0.80, P = 0.000). And meaningful relation between the AC and VAS score was found. CONCLUSIONS: VAS showed high ability to predict the self-perceived dental aesthetics and act as a simple and useful tool, which can be used in further investigations.