Finite element method analysis of the periodontal ligament in mandibular canine movement with transparent tooth correction treatment.

BACKGROUND: This study used the 3D finite element method to investigate canine's displacements and stresses in the canine's periodontal ligament (PDL) during canine's translation, inclination, and rotation with transparent tooth correction treatment. METHODS: Finite element models were developed to simulate dynamic orthodontic treatments of the translation, inclination, and rotation of the left mandibular canine with transparent tooth correction system. Piecewise static simulations were performed to replicate the dynamic process of orthodontic treatments. The distribution and change trends of canine's displacements and stresses in the canine's PDL during the three types of tooth movements were obtained. RESULTS: Maximum displacements were observed at the crown and middle part in the translation case, at the crown in the inclination case, and at the crown and root part in the rotation case. The relative maximum von Mises and principal stresses were mainly found at the cervix of the PDL in the translation and inclination cases. In the translation case, tensile stress was mainly observed on the mesial and distal surfaces near the lingual side and compressive stress was located at the bottom of the labial surface. In the inclination case, tensile stress was mainly observed at the labial cervix and lingual apex and compressive stress was located at the lingual cervix and labial apex. In the rotation case, von Mises stress was mainly located at the cervix and inside the lingual surface, tensile stress was located on the distal surface, and compressive stress was detected on the mesial surface. The stress and displacement value rapidly decreased in the first few steps and then reached a plateau. CONCLUSIONS: Canine's movement type significantly influences the distribution of canine's displacement and stresses in the canine's PDL. Changes in canine's displacement and stresses in the canine's PDL were exponential in transparent tooth correction treatment.

Efficient intraoral photogrammetry using self-identifying projective invariant marker.

PURPOSE: The re-measurement of full-arch implant digital impressions is an important step in denture restoration. This paper provides an efficient oral photogrammetry technology using projective invariant marker, applied in the re-measurement of full-arch implant digital impressions. METHODS: We have developed a self-recognizing marker with projection invariance, along with its detection code. The marker is installed on the scanning body and used for photogrammetric measurements. Triangulation is utilized to determine the 3D coordinates of the marker, followed by a series of post-processing steps to obtain more accurate 3D coordinates. RESULTS: The experimental data indicate that the optimal working distance is between 200 and 250 mm, with a minimum measurement error of less than 0.05 mm and an average measurement error of 0.10 mm. The measurement time is less than 2 min. CONCLUSIONS: The experimental results show that the photogrammetric system can obtain reliable positions of full-arch implants with efficient photogrammetry, without the need to enter the patient's oral cavity, and has potential clinical application value.

Application of an effective marker-less augmented reality image guidance method in dental implant surgery.

BACKGROUND: The existing augmented reality (AR) dental implant surgery navigation system usually uses markers to complete image guidance. However, markers often affect dentists' operations and make patients uncomfortable. METHODS: To solve the problems caused by markers, this paper proposes an effective marker-less image guidance method. After initialisation is completed by contour matching, the corresponding relationship is obtained by matching the feature points between the current frame and the preloaded initial frame. The camera pose is estimated by solving the Perspective-n-Point problem. RESULTS: The registration error of AR images is 0.731 ± 0.144 mm. The planting errors are 1.174 ± 0.241 mm at the neck, 1.433 ± 0.389 mm at the apex and 5.566 ± 2.102° for the angle. The maximum error and standard deviation meet the clinical requirements. CONCLUSIONS: We demonstrate that the proposed method can accurately guide dentists to perform dental implant surgery.

Mandibular resection and defect reconstruction guided by a contour registration-based augmented reality system: A preclinical trial.

The aim of this study was to verify the feasibility and accuracy of a contour registration-based augmented reality (AR) system in jaw surgery. An AR system was developed to display the interaction between virtual planning and images of the surgical site in real time. Several trials were performed with the guidance of the AR system and the surgical guide. The postoperative cone beam CT (CBCT) data were matched with the preoperatively planned data to evaluate the accuracy of the system by comparing the deviations in distance and angle. All procedures were performed successfully. In nine model trials, distance and angular deviations for the mandible, reconstructed fibula, and fixation screws were 1.62 ± 0.38 mm, 1.86 ± 0.43 mm, 1.67 ± 0.70 mm, and 3.68 ± 0.71°, 5.48 ± 2.06°, 7.50 ± 1.39°, respectively. In twelve animal trials, results of the AR system were compared with the surgical guide. Distance deviations for the bilateral condylar outer poles were 0.93 ± 0.63 mm and 0.81 ± 0.30 mm, respectively (p = 0.68). Distance deviations for the bilateral mandibular posterior angles were 2.01 ± 2.49 mm and 2.89 ± 1.83 mm, respectively (p = 0.50). Distance and angular deviations for the mandible were 1.41 ± 0.61 mm, 1.21 ± 0.18 mm (p = 0.45), and 6.81 ± 2.21°, 6.11 ± 2.93° (p = 0.65), respectively. Distance and angular deviations for the reconstructed tibiofibular bones were 0.88 ± 0.22 mm, 0.84 ± 0.18 mm (p = 0.70), and 6.47 ± 3.03°, 6.90 ± 4.01° (p = 0.84), respectively. This study proposed a contour registration-based AR system to assist surgeons in intuitively observing the surgical plan intraoperatively. The trial results indicated that this system had similar accuracy to the surgical guide.

Augmented reality for oral and maxillofacial surgery: The feasibility of a marker-free registration method.

BACKGROUND: Recognition of markers in the augmented reality system can reduce the additional cost of a guide plate required for the removal of benign tumours in oral and maxillofacial surgery, but the use of markers often has complex problems. METHOD: In order to avoid the complex problem of using markers, an augmented reality system based on a marker-free registration method was proposed to track the contour of the mandible edge. Use the computer to perform preoperative planning on the jaw model, select and mark the path of maxillofacial lesion resection. RESULTS: This method has an error of the surface matching was 0.6453 ± 0.2826 $0.6453\pm 0.2826$ mm, and an error of the surgical resection was 0.4858 ± 0.3712 $0.4858\pm 0.3712$ mm. CONCLUSIONS: We demonstrate that the system can accurately enhance the display of the surgical path and provide guidance for the tradition of maxillofacial surgery.

Application evaluation of virtual reality technology in dental implant training: a new dental implant training system: A CONSORT-compliant trial.

ABSTRACT: To evaluate the application of virtual reality technology in a dental implant training system.A 3-dimensional model of mandible was established by Mimics17.0 software based on the Digital Imaging and Communications in Medicine data obtained from cone beam computed tomography scanning of the patient in mandibular. Thirty physicians were divided into 2 groups. The virtual reality dental implant training system was used for group A, while conventional theoretical knowledge training and clinical demonstration were performed in group B. All young physicians have a 1-month study. After training, all the physicians in groups A and B would conduct a questionnaire survey according to the training situation, which was compared between the 2 groups. The success rate of the operation was also evaluated and compared.The median scores in the 5 dimensions of postoperative assessment of group A was 9/9/9/8/8, and of group B was 6/7/6/7/7. The scores of the 5 dimensions were significantly higher than those of group B (P < .05), indicating that group A has a better grasp of the simulator. After the training of simulated mandibular implants in group A, the deviations in the 4 dimensions of mesiodistal, buccal and tongue, depth, and angle were significantly lower than those of group B (P < .05). Group A has smaller deviations in each of the 4 dimensions than those in group B, indicating group A has a higher operation success rate.We independently develop a set of virtual surgery system for dental implant training, which can be used for teaching and training, with good operability and predictability, to achieve a breakthrough in dental implant surgery training.

Fluoropolymers for intracellular and in vivo protein delivery.

The design of efficient and universal carriers to transport proteins into cells is highly desirable in the development of biotherapeutics. However, intracellular protein delivery remains a major challenge owing to the multiple barriers in protein delivery process, such as protein encapsulation, endocytosis, endosomal escape and intracellular protein release. Recently, it was reported that fluorination on polymers is beneficial for their self-assembly and intracellular trafficking. We hypothesize the fluoropolymers can be used to encapsulate proteins and developed as a new class of carriers to break down the barriers during intracellular protein delivery. In this study, we successfully discovered an efficient and non-toxic polymer for protein delivery in a library of fluoropolymers. The lead material A6-2 in the library efficiently transported various proteins including bovine serum albumin, ß-galactosidase, saporin and a cyclic hendecapeptide into the cytosol of living cells with minimal cytotoxicity. More importantly, activities of delivered proteins and peptides were maintained after delivery. The A6-2/saporin complex was further coated with a hyaluronic acid shell, and the yielding nanoparticle efficiently suppressed tumor growth in a breast cancer model by targeted protein delivery. This study provides a new insight into the design of efficient and biocompatible polymers for protein delivery.

Optimization of configuration of attachment in tooth translation with transparent tooth correction by appropriate moment-to-force ratios: Biomechanical analysis.

Transparent tooth correction treatment is an esthetic alternative to traditional orthodontic treatment. Recently, attachments were introduced in transparent tooth correction treatments to improve the predictability of orthodontic movement. In order to optimize the attachment configuration, the force delivery system of attachments in orthodontic aligner treatment was analyzed. Based on mechanical principles, such as the synthesis theorem of force system, Varignon theorem, and the theorem of force translation, the force system of attachment was analyzed. How the attachments affected the orthodontic treatment was investigated. The attachments' force system Fr,Ft,Mr and Mt was determined. The optimum attachment for translation and controlled tipping movement was conceived. The attachments can be designed and placed appropriately to improve tooth movement.

Polymers modified with double-tailed fluorous compounds for efficient DNA and siRNA delivery.

Cationic polymers are widely used as gene carriers, however, these polymers are usually associated with low transfection efficacy and non-negligible toxicity. Fluorination on polymers significantly improves their performances in gene delivery, but a high density of fluorous chains must be conjugated on a single polymer. Here we present a new strategy to construct fluorinated polymers with minimal fluorous chains for efficient DNA and siRNA delivery. A double-tailed fluorous compound 2-chloro-4,6-bis[(perfluorohexyl)propyloxy]-1,3,5-triazine (CBT) was conjugated on dendrimers of different generations and low molecular weight polyethylenimine via a facile synthesis. The yielding products with average numbers of 1-2 conjugated CBT moieties showed much improved EGFP and luciferase transfection efficacy compared to unmodified polymers. In addition, these polymers show high siRNA delivery efficacy on different cell lines. Among the synthesized polymers, generation 1 (G1) dendrimer modified with an average number of 1.9 CBT moieties (G1-CBT1.9) shows the highest efficacy when delivering both DNA and siRNA and its efficacy approaches that of Lipofectamine 2000. G1-CBT1.9 also shows efficient gene silencing in vivo. All of the CBT-modified polymers exhibit minimal toxicity on the cells at their optimal transfection conditions. This study provides a new strategy to design efficient fluorous polymers for DNA and siRNA delivery.

Numerical analysis of tooth movement in different plans of transparent tooth correction therapies.

BACKGROUND: The objective of this study was to investigate how treatment strategies in the same treatment affected the canine's initial displacement and the stress in periodontal ligament using three-dimensional finite element analysis. And to find out the way to design an effective treatment plan. METHODS: Based on computed tomography images of the teeth and their supporting tissues, solid models were used to build finite element models. Three treatment plans of three different transparent tooth correction therapies finite element-analyses were operated. RESULTS: The canine's initial displacement and stresses' distribution in periodontal ligament were obtained. CONCLUSIONS: For rotation movement, the canine should rotate along tooth long axis, and not combine with other kinds of tooth movement as possible. For translation movement, the combination of translation and inclination movement is helpful for the treatment.

Hydrogen-bonding dramatically modulates the gene transfection efficacy of surface-engineered dendrimers.

Dendrimers have shown great promise in the design of efficient gene vectors. However, high transfection efficacy is usually associated with serious cytotoxicity for these cationic polymers. Here, we report a facile strategy to prepare surface-engineered dendrimers with a dramatic transfection efficacy and reduced cytotoxicity. Surface-engineered dendrimers with multiple hydrogen bonding ligands such as guanamine and nucleobase derivatives show superior efficacy and low cytotoxicity on commonly used cells as well as 3D tumor spheroids to representative transfection reagents such as Lipofectamine 2000. Complementary multiple hydrogen bonding interactions between the modified ligands and DNA nucleobases play essential roles in efficient gene transfection. The hydrogen-bond modulation strategy represents a promising tool in the design of highly efficient and less cytotoxic gene materials.

[Manufacture method and clinical application of minimally invasive dental implant guide template based on registration technology].

OBJECTIVE: To guide doctors in precisely positioning surgical operation, a new production method of minimally invasive implant guide template was presented. METHODS: The mandible of patient was scanned by CT scanner, and three-dimensional jaw bone model was constructed based on CT images data The professional dental implant software Simplant was used to simulate the plant based on the three-dimensional CT model to determine the location and depth of implants. In the same time, the dental plaster models were scanned by stereo vision system to build the oral mucosa model. Next, curvature registration technology was used to fuse the oral mucosa model and the CT model, then the designed position of implant in the oral mucosa could be determined. The minimally invasive implant guide template was designed in 3-Matic software according to the design position of implant and the oral mucosa model. Finally, the template was produced by rapid prototyping. RESULTS: The three-dimensional registration technology was useful to fuse the CT data and the dental plaster data, and the template was accurate that could provide the doctors a guidance in the actual planting without cut-off mucosa. CONCLUSION: The guide template which fabricated by comprehensive utilization of three-dimensional registration, Simplant simulation and rapid prototyping positioning are accurate and can achieve the minimally invasive and accuracy implant surgery, this technique is worthy of clinical use.