Three-dimensional finite element study of mandibular first molar distalization with clear aligner / 华西口腔医学杂志

OBJECTIVES@#This study aimed to construct the finite element model of the mandibular first molar with the invisible appliance and explore the dentition movement characteristics of the mandibular first molar when using micro-implant anchorage and different initial positions of the first molar.@*METHODS@#Models of the mandible, tooth, periodontal membrane, and invisible appliance were constructed using cone beam computed tomography (CBCT) data. The two groups were divided into the non-anchorage group and the micro-implant group (between the roots of the first molar and the second molar) based on whether the elastic traction of the micro-implant was assisted or not. The two groups were divided into the following conditions based on the starting position of the first molar: Working condition 1: the distance between the first molar and the second premolar was 0 mm; working condition 2: the distance between the first molar and the second premolar was 1 mm; working condition 3: the distance between the first molar and the second premolar was 2 mm; working condition 4: the distance between the first molar and the second premolar was 3 mm. The data characte-ristics of total displacement and displacement in each direction of dentition were analyzed.@*RESULTS@#In the non-ancho-rage group, all the other teeth showed reverse movement except for the first molar which was moved distally. Meanwhile, in the micro-implant group, except for a small amount of mesial movement of the second molar in wor-king condition 1, the whole dentition in other working conditions presented distal movement and anterior teeth showed lingual movement, among which the distal displacement of the first molar in working condition 4 was the largest. With the change of the initial position of the first molar to the distal, the movement of the first molar to the distal, the premolar to the mesial, and the anterior to the lip increased, while the movement of the second molar to the mesial decreased.@*CONCLUSIONS@#The micro-implant can effectively protect the anterior anchorage, increase the expression rate of molar distancing, and avoid the round-trip movement of the second molar. The initial position of the first molar movement is related to the amount of distancing and the remaining tooth movement.

Optimal microimplant sites in the mandibular retromolar area: mesh analysis of cortical bone thickness and density in CBCT images / Sitios de microimplantes óptimos en el área retromolar mandibular: análisis de malla del grosor y densidad del hueso cortical en imágenes CBCT

SUMMARY: This study was performed to identify optimal microimplant sites in the mandibular retromolar area by measurement and analysis of cortical bone thickness and density. Forty-nine records of cone-beam computed tomography were selected from 173 patients. Invivo 5.2 software was used to measure the thickness and density of 25 sites on a mesh in the mandibular retromolar area. Pearson correlation, Spearman correlation, and binary logistic regression analyses were performed to explore correlations between retromolar measurements and patient characteristics. The LSD test was used to identify optimal microimplant sites in this area. One-way ANOVA, with post hoc SNK test, was used to compare optimal microimplant sites among the retromolar area, the distobuccal bone of the second molar, and a location between the first and second molars. The mean thickness and density of mandibular retromolar cortical bone were 2.35 ± 0.76 mm and 530.49 ± 188.83 HU, respectively. In the mandibular retromolar area, the thickness and density of cortical bone increased from the lingual to buccal sides, and from the distal to mesial. Among 25 sites, S5C1 had the greatest thickness and density; it exhibited greater thickness and density, compared with the distobuccal bone of the second molar and the site between the first and second molars. For distal uprighting of mesially tipped molars, we recommend placement of microimplants into the retromolar distobuccal site; for distalization of mandibular dentition, we recommend placement of microimplants into the retromolar mesiobuccal site (S5C1) or 2 mm from the mesial direction of the second molar distobuccal site (B).

RESUMEN: Este estudio se realizó para identificar los sitios óptimos de microimplantes en el área retromolar mandibular mediante la medición y el análisis del grosor y la densidad del hueso cortical. Se seleccionaron 49 registros de tomografía computarizada de haz cónico de 173 pacientes. Se utilizó el software Invivo 5.2 para medir el grosor y la densidad de 25 sitios en una malla en el área retromolar mandibular. Se realizaron análisis de correlación de Pearson, correlación de Spearman y regresión logística binaria para explorar las correlaciones entre las mediciones retromolares y las características del paciente. La prueba de LSD se utilizó para identificar los sitios óptimos de microimplantes en esta área. Se utilizó ANOVA unidireccional, con prueba SNK post hoc, para comparar los sitios óptimos de microimplante entre el área retromolar, el hueso distobucal del segundo molar y una ubicación entre el primer y el segundo molar. El grosor y la densidad medios del hueso cortical retromolar mandibular fueron 2,35 ± 0,76 mm y 530,49 ± 188,83 HU, respectivamente. En el área retromolar mandibular, el grosor y la densidad del hueso cortical aumentaron desde el lado lingual al bucal y desde el distal al mesial. Entre los 25 sitios, S5C1 se determinó el mayor espesor y densidad; presentó mayor grosor y densidad, en comparación con el hueso distobucal del segundo molar y el sitio entre el primero y el segundo molar. Para rectificación distal de molares con punta mesial, recomendamos la colocación de microimplantes en el sitio retromolar bucal; para la distalización de la dentición mandibular, recomendamos la colocación de microimplantes en el sitio retromolar mesiobucal (S5C1) o 2 mm desde la dirección mesial del sitio distobucal del segundo molar (B).

Two methods of treatment for skeletal Class Ⅲ malocclusion on airway changes before and after clinical research / 口腔疾病防治

Objective @# To investigate the changes in the sagittal diameter of the upper airway before and after the treatment of skeletal Class Ⅲ malocclusion in adults with microimplant anchorage and class Ⅲ intermaxillary elastics and to provide a reference for clinical treatment. @*Methods @#A total of 35 adult patients with skeletal Class Ⅲ malocclusion were selected to be treated with the straight-wire technique. Microimplant group, 15 cases (group A): patients with severe skeletal Class Ⅲ malocclusion (vertical high angle) were treated with the straight-wire technique combined with microimplant anchorage; class Ⅲ intermaxillary elastics group, 20 cases (group B): Patients with mild or moderate skeletal Class Ⅲ malocclusion (vertical low angle and average angle) were treated with the straight-wire technique combined with class Ⅲ intermaxillary elastics, and cephalometric radiographs obtained before and after treatment in the upper airway in the two groups were measured and analyzed.@*Results @#Changes in cranial and maxillofacial measurements after correction: in group A, (sella-nasion-supramental angle) the SNB angle decreased significantly (P < 0.05), and (subspinale-nasion-supramental angle) the ANB angle increased significantly (P < 0.05). In group B, the SNB angle decreased significantly (P < 0.05), while (subspinale-nasion-subspinale angle) the SNA angle、ANB angle and anterior skull base plane-mandibular plane angle (Sn-MP) angle increased significantly (P < 0.05). Changes in sagittal diameter of the upper airway measurements after corrections: In group A, the width of the glossopharyngeal segment of the upper airway (TB-TPPW) decreased significantly (P < 0.05). In group B, first segment width of the upper airway behind the hard palate (PNS-R) increased significantly (P < 0.05). After correction, the decreased SNB and increased ANB in group A was higher than that in group B, and the difference was statistically significant （P < 0.05）. The decreased of TB-TPPW in upper airway of group A was greater than that of group B, and the difference was statistically significant （P < 0.05）.@* Conclusions @#In the treatment of skeletal class Ⅲ malocclusion with microimplant anchorage, the sagittal diameter of the glossopharyngeal segment of the upper airway has a negative impact.

Clinical efficacy of counterclockwise rotating the functional occlusal plane using micro-implant anchorage / 浙江大学学报·医学版

To evaluate the therapeutic effect of using micro-implant anchorage (MIA) to rotate the functional occlusal plane (FOP) counterclockwise. Forty skeletal class Ⅱ high-angle patients who had completed orthodontic treatment were enrolled, including 20 patients treated with MIA orthodontic system (MIA group) and the other 20 patients treated with traditional sliding straight wire appliance (control group). Cephalometric measurements on the lateral cranial radiographs before and after treatment were performed, all acquired data were statistically analyzed with SPSS 26.0. At the end of treatment, MIA group obtained better effect of FOP and mandibular plane counter-clockwise rotation than the control group. In the MIA group, the average change of FOP-frankfort horizontal plane (FH), FOP-SN and mandibular plane angle (MP-FH) angle was -4.5(-7.3, -3.7)°, (3.3)° and -1.7(-3.0, -0.9)°, respectively. In the control group, the average change of FOP-FH, FOP-SN and MP-FH angle was -0.1(-4.1, 3.0)°, (-0.1±5.1)° and -0.4(-2.4, 0.7)°, respectively. There was significant difference between the change of the two groups (all <0.05). Compared with the traditional sliding straight wire appliance, counterclockwise rotation of FOP can be more effectively reversed by using MIA orthodontic system, and the MP-FH can be reduced as well.

The Role of Power Arm by Combined Use of Clear Aligner and Miniscrew in En-Masse Retraction of Maxillary Anterior Teeth / 医用生物力学

Objective To investigate the role of Power Arm in en-masse retraction of maxillary anterior teeth using clear aligner (CA) and micro-implant anchorage (MIA). Methods The three-dimensional (3D) model of maxillary anterior teeth by combined use of CA and MIA was established, and the 6 mm-height Power Arm, was attached to the canine or appliance. The initial displacement and the maximum von Mises stress of periodontal ligament under three loading conditions were analyzed, namely the force was loaded by CA+150 g retraction force at canine, CA+150 g retraction force on Power Arm at appliance, CA+150 g retraction force on Power Arm at canine. Results In sagittal direction, the crown and root displacement difference of maxillary central incisor was 129, 129, 133 μm，respectively. The crown displacement of the maxillary first molar was -23.3, -23.5, -26.8 μm, respectively. The maximum von Mises stress of periodontal ligament in central incisor was 48.4, 72.6, 40.0 kPa, respectively, and that of the first molar was 5.3, 10.5, 5.8 kPa, respectively. Conclusions It can not be testified that retraction of the 6 mm-height Power Arm at canine or appliance with 5 mm-height mini-screw has more advantages than retraction of the canine directly for more favorably controlling the torque of incisors, saving anchorage of posterior teeth and decreasing von Mises stress of the periodontal ligament.

Maxillary skeletal expander for maxillary transverse deficiency: Application and strengths / 中国组织工程研究

BACKGROUND: Maxillary skeletal expander is a non-surgical expansion technique of the maxilla. It is different from the traditional maxillary rapid expander, micro-implant assisted rapid palatal expansion, and surgically assisted rapid palatal expansion. It provides new ideas and methods for the correction of maxillary transverse deficiency, and especially for adult patients with the growth finished, provides an efficient and minimally invasive bone expansion. OBJECTIVE: To review the application and advantage of the maxillary skeletal expander in the treatment of maxillary transverse deficiency, providing scientific reference for the clinical therapeutic schedule in such patients. METHODS: A computer search for Cochrane Library, PubMed, Embase, Web of Science, CNKI, WanFang Database, and CBM databases was performed for Chinese and English literature related to the maxillary expansion device published before May 31st, 2019. RESULTS AND CONCLUSION: The maxillary skeletal expander is an effective method for correcting the maxillary transverse deficiency, and the expansion of the arch is not limited by age. This device also has a good outcome in bone expansion for adults. The maxillary skeletal expander expands the entire mid-face structure, causing the mid-sacral suture to be parallel, followed by ruptured palatine suture, increased width between the zygomatic bones, as well as the entire nasal cavity involving the upper nasal bone area is widened. This device also causes less adverse reactions, for example, the teeth are inclined buccally and the height of the alveolar bone is reduced.

Establishing the Finite Element Model of Mid-Palatal Suture Fracture by Microimplant-Assisted Palatal Expansion / 医用生物力学

Objective To analyze mechanical characteristics for stress accumulation of the maxillary complex during expansion until complete fracture of the mid-palatal suture by using the three-dimensional (3D) finite element method, and verify validity of the model. Methods The finite element maxillary complex model containing the microimplants was established. The yield strength of the mid-palatal suture was set, and the transverse displacement of 0.25 mm was loaded every 5 ms as the load until the suture was completely fractured. The CT images of one clinical patient before and after expansion were compared and verified. Results During 0-17 ms, the stress was mainly concentrated around the microimplants, the middle of the mid-palatal suture and the zygomatico-maxillary sutures. During 18-60 ms, cracks began to occur in the mid-palatal suture, and expanded forward and backward. During 61-71 ms, the rupture path was followed by posterior part of the mid, palatal suture-the front part and the back part. Conclusions The 3D finite element model of microimplant-assisted expansion based on fracture mechanics was effective and the calculated fracture process result were more consistent with clinical practice. The research findings provide the mechanical reference model for more effective research on microimplant-assisted palatal expansion in the future.

Combined use of miniscrews and clear aligner for en-mass retraction of maxillary anterior teeth: A finite element analysis / 实用口腔医学杂志

Objective: To evaluate the biomechanical effects of combined use of miniscrew and clear aligner in different kinds of loading condition on the en-mass retraction of maxillary anterior teeth. Methods: 3 D finite element models of the maxillary bone with miniscrews and clear aligner were reconstructed using the method of reverse engineering with CBCT data of an adult patient who had maxillary first premolars extracted. The orthodontic force was loaded by (1) clear aligner, (2) clear aligner and 1. 47 N force of retraction at appliance and (3) clear aligner and 1. 47 N force of retraction at canine, respectively. Results: Under the working condition of (1), (2) and (3), in sagittal direction, the displacement difference of crown and root of the maxillary central incisor was 1. 12 E-02 mm, 1. 29 E-02 mm and 9. 62 E-03 mm respectively, the displacement of the first molar crown was-2. 49 E-02 mm, -2. 09 E-02 mm and-2. 00 E-02 mm respectively; in vertical direction, extrusion of the maxillary central incisor was 1. 77 E-03 mm, 2. 93 E-03 mm and 6. 53 E-04 mm respectively. Conclusion: The working condition (3) is more advantageous to control the torque of incisors and to save the anchorage of posterior teeth, and more effective to control the extrusion of the incisors.

CBCT study of the alveolar bone remodeling after retraction of the maxillary incisors assisting with micro-implant anchorage in maxillary protrusion adults / 口腔疾病防治

Objective@# To study the remodeling of alveolar bone after retraction of the maxillary incisors assisting with micro-implant anchorage in adult patients with maxillary protrusion by CBCT.@*Methods@#Forty patients who were treated with extraction of the maxillary first premolars with microimplant anchorage meeting the inclusion criteria were selected. The CBCT data before and after treatment were collected, and the Dolphin Imaging 3D measurement software was used to measure and analyze the height and thickness of the alveolar bone of the 80 upper central incisors and the 80 lateral incisors.@*Results @#After retraction of the incisors assisting with microimplant anchorage, the labial alveolar bone height of the maxillary central incisors decreased (0.11 ± 0.33) mm, and the lingual alveolar bone height of the maxillary central incisors decreased (0.85 ± 1.23) mm. The labial alveolar bone height of the maxillary lateral incisors decreased (0.18 ± 0.42) mm, and the lingual alveolar bone height of the maxillary lateral incisors decreased (1.13 ± 1.14 ) mm. The reduction in the lingual alveolar bone height was greater than that of the labial side, and the difference was statistically significant (P < 0.05). The labial alveolar bone thickness of the maxillary central incisors increased (the root cervix, the root media and the root apex), and the difference was statistically significant (P < 0.001). The labial alveolar bone thickness of the maxillary lateral incisors also increased (P < 0.05), while the lingual alveolar bone thickness and the total alveolar bone thickness of the maxillary central and lateral incisors decreased (P < 0.001). @*Conclusion@#In adults with maxillary protrusion, the microimplant was used to assist the reduction of the anterior teeth. The alveolar bone height of the maxillary incisors was reduced, and the palatal alveolar bone height decreased more than that of the labial side. The alveolar bone of the labrum was thickened, and the palatal alveolar bone thickness and the total alveolar bone thickness of the maxillary incisors were reduced after treatment.

Study on the morphology of micro-implant-bone interface cells and bone histomorphology under different implantation / Estudio sobre la morfología de las células de la interfaz microscópica implante-hueso y la histomorfología ósea bajo diferentes implantaciones

SUMMARY: Micro-implant stability has always been the focus of orthodontic clinical research.In the experiment, the morphological changes of bone tissue around the micro-implants in self-tapping and assisting implantation were investigated to explore the effect of different implantation on the osseointegration of micro-implants in order to provide some theoretical basis for clinical practice. Six adult male Beagle dogs were selected,three implants were implanted into the left and right maxillary bone of Beagle dogs at the 0th, 4th and 6th week, respectively. One side to self-tapping implantation, the opposite side to assisting implantation. At the 8th week of the experiment, the animals were sacrificed and the micro-implant-bone tissue specimens with the healing time of 8w, 4w and 2w were obtained.The specimens were stained with Toluidine Blue (TB) and photographed under 100X, 200X microscope. Morphology of microimplant- bone interface cells was observed under light microscope. In self-tapping group, there were some fibrous tissues surrounding the micro-implants at the 2th week, the formation of osteoblasts and osteoid was observed at the 4th week, the wavy and lamellar bone tissues were seen at the 8th week.In assisting group,more collagen fibers were deposited around the micro-implant at the 2th week, there were a large number of osteoid-like cells, and the collagen was gradually replaced by the bone tissue at the 4th week, the osteoblasts were active and the osteoblasts were linear arrange and form a laminate bone at the 8th week.Whether implanted self-tapping or assisted implantation, micro-implant-bone interface reconstruction can occur. If the clinical need for early loading force, micro-implant try to choose selftapping implantation. By appropriately prolonging the healing time, the initial stability of the micro-implant under assistive implantation can be improved.

RESUMEN: La estabilidad del microimplante siempre ha sido el foco de la investigación clínica en ortodoncia. En este trabajo se investigaron los cambios morfológicos del tejido óseo alrededor de los microimplantes autorroscantes y se ayudó a la implantación para explorar el efecto de diferentes implantes en la osteointegración de microimplantes con el fin de proporcionar alguna base teórica para la práctica clínica. Se seleccionaron seis perros Beagle machos adultos, y se colocaron tres implantes en los huesos maxilares izquierdo y derecho en la 0ª, 4ª y 6ª semana, respectivamente. De un lado se colocó el implante autorroscante, y del otro lado el implante asistido. En la octava semana, se sacrificaron los animales y se obtuvieron las muestras de microimplante-hueso con el tiempo de cicatrización de 8, 4 y 2 semanas. Las muestras fueron teñidas con azul de toluidina (TB) y fotografiadas bajo aumento de 100X, y microscopio de 200X. La morfología de las células de la interfaz microimplante-hueso se observó bajo microscopio óptico. En el grupo autorroscante, había tejido fibroso que rodeaba los microimplantes a la 2ª semana, se observó la formación de osteoblastos y osteoide a la 4ª semana y de tejido óseo ondulado y lamelar a la 8ª semana. En el grupo asistido, se depositaron más fibras de colágeno alrededor del microimplante en la 2ª semana, hubo un gran número de células similares a osteoide, y el colágeno fue reemplazado gradualmente por el tejido óseo en la 4ª semana; los osteoblastos estaban activos y se ubicaron linealmente formando un hueso laminado en la 8ª semana. Ya sea que el implante sea con autoasistencia o con implantación asistida, puede ocurrir la reconstrucción de la interfaz microimplante-hueso. Si existe la necesidad clínica de una fuerza de carga temprana, el microimplante de elección sería la implantación autorroscante. Al prolongar apropiadamente el tiempo de curación, se puede mejorar la estabilidad inicial del microimplante bajo implantación asistida.

Surface characteristics and mechanical behavior of retrieved orthodontic microimplants / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

OBJECTIVES@#To observe the surface characteristics and mechanical behavior of retrieved microimplants under clinically simulating experimental conditions and to investigate the feasibility of reuse of microimplants.@*MATERIALS AND METHODS@#The microimplants, inserted at different angles, were retrieved from the patients (RMIP) and the artificial bone (RMIA). Surface characteristics, including morphologic changes of tips and thread edges, length reduction, and surface compositional variation, were evaluated using a field emission scanning electron microscope, a stereoscopic microscope, and energy-dispersive X-ray spectroscopy, respectively. Mechanical behavior comprising maximum insertion torque (MIT) and insertion time was tested with the artificial bone under clinically simulating conditions.@*RESULTS@#The tips and thread edges were worn out to various degrees in retrieved microimplants and thin deposits were observed on the surface in the RMIP group. Traces of foreign elements, such as iron, sulphur, and calcium, were detected on the surface of RMIP. Both MIT and insertion time of retrieved microimplants were increased compared to their initial use, and were much greater in RMIP. The increases of MIT were seen in all groups inserted at the insertion angle of 45° compared with 90°, although the differences were not statistically significant.@*CONCLUSIONS@#Retrieved microimplants exhibited different degrees of changes on surface characteristics and mechanical behavior, with more changes in RMIP. The reuse of microimplants for immediate relocation in the same patient may be acceptable; however, postponed relocation and allogeneic reuse of microimplants are not recommended in clinical practice.

Assessment of cortical bone microdamage following insertion of microimplants using optical coherence tomography: a preliminary study / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

OBJECTIVES@#The study was done to evaluate the efficacy of optical coherence tomography (OCT), to detect and analyze the microdamage occurring around the microimplant immediately following its placement, and to compare the findings with micro-computed tomography (μCT) images of the samples to validate the result of the present study.@*METHODS@#Microimplants were inserted into bovine bone samples. Images of the samples were obtained using OCT and μCT. Visual comparisons of the images were made to evaluate whether anatomical details and microdamage induced by microimplant insertion were accurately revealed by OCT.@*RESULTS@#The surface of the cortical bone with its anatomical variations is visualized on the OCT images. Microdamage occurring on the surface of the cortical bone around the microimplant can be appreciated in OCT images. The resulting OCT images were compared with the μCT images. A high correlation regarding the visualization of individual microcracks was observed. The depth penetration of OCT is limited when compared to μCT.@*CONCLUSIONS@#OCT in the present study was able to generate high-resolution images of the microdamage occurring around the microimplant. Image quality at the surface of the cortical bone is above par when compared with μCT imaging, because of the inherent high contrast and high-resolution quality of OCT systems. Improvements in the imaging depth and development of intraoral sensors are vital for developing a real-time imaging system and integrating the system into orthodontic practice.

Towards a multidimensional scientific approach to improve clinical practices for infertility treatment / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Polycystic ovary syndrome (PCOS) is the most common metabolic and endocrine disorder in women, leading to infertility. However, there is no general agreement concerning how to diagnose and treat PCOS. The Rotterdam consensus statement from the European Society of Human Reproduction and Embryology/American Society for Reproductive Medicine, the Chinese diagnostic criteria and consensus statement, and the clinical practice guideline from the Endocrine Society in the USA are widely recognized. Guidance has been provided for clinical practice based on a comparative analysis of the above three practice guidelines or consensus statements (Wang et al., 2018a). High body mass index (BMI) has no negative effect on the outcome of in vitro fertilization (IVF) in Chinese patients with PCOS; however, the conclusion may be limited by the retrospective design and potential bias (Pan et al., 2018). Neonatal birth weight is positively affected by both maternal pre-pregnancy body mass index (pre-BMI) and gestational weight gain (Du et al., 2017). Normal body weight is very important for conception. Women with PCOS are almost 3 times more likely to be obese than those without PCOS; however, no specific interventions are available to induce weight loss, and drugs are used to treat other symptoms of the syndrome or obesity in the general population. A network meta-analysis found that the amount of weight loss differed significantly according to the choice of drugs (in descending order): liraglutide, orlistat, and metformin. Liraglutide alone, liraglutide/metformin, and metformin alone significantly reduced waist circumference, but no change was found with orlistat, indicating liraglutide appears superior to the other drugs in reducing weight and waist circumference (Wang et al., 2018b). IVF, as a choice for more than 1 000 000 infertile couples each year, gives rise to the birth of over 3 000 000 babies worldwide.

Tratamiento ortodóncico en pacientes adultos combinando CA Clear Aligner con brackets linguales y microimplantes / Orthodontic treatment in adult patients combining CA Clear Aligner with lingual brackets and microimplants

Los pacientes adultos normalmente prefieren tratamiento ortodóncico invisible. La ortodoncia puedemejorar la estética, alinear y nivelar los dientes mejorando la salud periodontal, y también la posiciónde los dientes para recibir tratamiento protésico con un mejor pronóstico.

Adult patients normally prefer invisible orthodontic treatment. Orthodontics can improvethe aesthetics, align and level the teeth improvingthe periodontal health and also position the teeth to receive the prosthetic treatmentwith a better prognosis.

Non-surgical treatment of transverse deficiency in adults using Microimplant-assisted Rapid Palatal Expansion (MARPE)

ABSTRACT Introduction: Maxillary transverse deficiency is a highly prevalent malocclusion present in all age groups, from primary to permanent dentition. If not treated on time, it can aggravate and evolve to a more complex malocclusion, hindering facial growth and development. Aside from the occlusal consequences, the deficiency can bring about serious respiratory problems as well, due to the consequent nasal constriction usually associated. In growing patients, this condition can be easily handled with a conventional rapid palatal expansion. However, mature patients are frequently subjected to a more invasive procedure, the surgically-assisted rapid palatal expansion (SARPE). More recently, researches have demonstrated that it is possible to expand the maxilla in grown patients without performing osteotomies, but using microimplants anchorage instead. This novel technique is called microimplant-assisted rapid palatal expansion (MARPE). Objective: The aim of the present article was to demonstrate and discuss a MARPE technique developed by Dr. Won Moon and colleagues at University of California - Los Angeles (UCLA). Methods: All laboratory and clinical steps needed for its correct execution are thoroughly described. For better comprehension, a mature patient case is reported, detailing all the treatment progress and results obtained. Conclusion: It was concluded that the demonstrated technique could be an interesting alternative to SARPE in the majority of non-growing patients with maxillary transverse deficiency. The present patient showed important occlusal and respiratory benefits following the procedure, without requiring any surgical intervention.

RESUMO Introdução: a deficiência transversa da maxila é uma má oclusão com alta prevalência em todas as faixas etárias, da dentição decídua à permanente. Se não for corrigida, pode agravar-se com o passar do tempo, prejudicando o crescimento e desenvolvimento facial. Além dos prejuízos oclusais, essa deficiência pode trazer problemas respiratórios também severos, devido à consequente constrição da cavidade nasal. Em pacientes em crescimento, a sua resolução é relativamente simples, por meio da expansão rápida convencional da maxila. Porém, os pacientes já maduros geralmente são encaminhados para um procedimento mais invasivo, a expansão rápida de maxila assistida cirurgicamente (SARPE). Mais recentemente, pesquisadores têm demonstrado que é possível executar a expansão palatal esquelética em pacientes adultos sem auxílio de osteotomias, mas sim com auxílio de mini-implantes. Essa técnica é denominada Microimplant-Assisted Rapid Palatal Expansion, ou MARPE. Objetivo: o objetivo do presente artigo é demonstrar e discutir uma das técnicas disponíveis de MARPE, desenvolvida por Won Moon e colaboradores, na University of California, Los Angeles (UCLA). Métodos: a técnica encontra-se detalhadamente descrita, com as etapas laboratoriais e clínicas que devem ser seguidas para sua correta execução. Para descrevê-la, é apresentado o caso clínico de uma paciente adulta, detalhando toda a sequência do tratamento e os resultados obtidos. Conclusão: a técnica apresentada pode ser uma alternativa não invasiva à SARPE na resolução da deficiência transversa de maxila, podendo ser empregada na maioria dos pacientes com crescimento facial finalizado. A paciente apresentada demonstrou benefícios significativos nos aspectos oclusal e respiratório, sem a necessidade de intervenção cirúrgica.

Incorporation of silver nanoparticles on the surface of orthodontic microimplants to achieve antimicrobial properties / 대한치과교정학회지

OBJECTIVE: Microbial aggregation around dental implants can lead to loss/loosening of the implants. This study was aimed at surface treating titanium microimplants with silver nanoparticles (AgNPs) to achieve antibacterial properties. METHODS: AgNP-modified titanium microimplants (Ti-nAg) were prepared using two methods. The first method involved coating the microimplants with regular AgNPs (Ti-AgNP) and the second involved coating them with a AgNP-coated biopolymer (Ti-BP-AgNP). The topologies, microstructures, and chemical compositions of the surfaces of the Ti-nAg were characterized by scanning electron microscopy (SEM) equipped with energy-dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). Disk diffusion tests using Streptococcus mutans, Streptococcus sanguinis, and Aggregatibacter actinomycetemcomitans were performed to test the antibacterial activity of the Ti-nAg microimplants. RESULTS: SEM revealed that only a meager amount of AgNPs was sparsely deposited on the Ti-AgNP surface with the first method, while a layer of AgNP-coated biopolymer extended along the Ti-BP-AgNP surface in the second method. The diameters of the coated nanoparticles were in the range of 10 to 30 nm. EDS revealed 1.05 atomic % of Ag on the surface of the Ti-AgNP and an astounding 21.2 atomic % on the surface of the Ti-BP-AgNP. XPS confirmed the metallic state of silver on the Ti-BP-AgNP surface. After 24 hours of incubation, clear zones of inhibition were seen around the Ti-BP-AgNP microimplants in all three test bacterial culture plates, whereas no antibacterial effect was observed with the Ti-AgNP microimplants. CONCLUSIONS: Titanium microimplants modified with Ti-BP-AgNP exhibit excellent antibacterial properties, making them a promising implantable biomaterial.

Comparison of mechanical and biological properties of zirconia and titanium alloy orthodontic micro-implants / 대한치과교정학회지

OBJECTIVE: The aim of this study was to compare the initial stability as insertion and removal torque and the clinical applicability of novel orthodontic zirconia micro-implants made using a powder injection molding (PIM) technique with those parameters in conventional titanium micro-implants. METHODS: Sixty zirconia and 60 titanium micro-implants of similar design (diameter, 1.6 mm; length, 8.0 mm) were inserted perpendicularly in solid polyurethane foam with varying densities of 20 pounds per cubic foot (pcf), 30 pcf, and 40 pcf. Primary stability was measured as maximum insertion torque (MIT) and maximum removal torque (MRT). To investigate clinical applicability, compressive and tensile forces were recorded at 0.01, 0.02, and 0.03 mm displacement of the implants at angles of 0°, 10°, 20°, 30°, and 40°. The biocompatibility of zirconia micro-implants was assessed via an experimental animal study. RESULTS: There were no statistically significant differences between zirconia micro-implants and titanium alloy implants with regard to MIT, MRT, or the amount of movement in the angulated lateral displacement test. As angulation increased, the mean compressive and tensile forces required to displace both types of micro-implants increased substantially at all distances. The average bone-to-implant contact ratio of prototype zirconia micro-implants was 56.88 ± 6.72%. CONCLUSIONS: Zirconia micro-implants showed initial stability and clinical applicability for diverse orthodontic treatments comparable to that of titanium micro-implants under compressive and tensile forces.

Control of the maxillary occlusal plane by micro-implant in the process of en-mass retraction:A finite element analysis / 实用口腔医学杂志

Objective:To investigate the changes of occlusal plane in the process of retracting maxillary anterior teeth with different vertical traction force.Methods:The three dimensional finite element model of maxillary anterior teeth en-masse retraction by micro-implant was constructed with cone beam CT scanning and MIMICS and ANSYS software.Then the movement tendency of tooth and the changes of the maxillary occlusal plane was calculated when the vertical traction force was 0,0.5,0.75 and 1 N in the process of en-mass retraction,respectively.Results:Lingual tipping of anterior teeth,distal tipping of the first molar and the maxillary occlusal plane clockwise rotation by the retraction forces were observed.With the vertical traction force increasing,lingual tipping of anterior teeth and distal tipping of the first molar were decreased,and the occlusal plane clockwise rotation was prevented.Conclusion:The upper dentition movement and occlusal plane rotation can be changed effectively by the vertical traction with different force.When retract anterior teeth,0.5-0.75 N vertical traction force is beneficial to prevent clockwise rotation of the maxillary occlusal plane.

Treatment of an adult patient with skeletal crossbite and mandibular deviation by distalization of the mandibu-lar molar / 实用口腔医学杂志

An adult patient with skeletal crossbite and mandibular deviation was treated by mandibular molar distalization using micro-im-plant and intermaxillary traction.After treatment,the facial contour of the patient was improved,the Class Ⅰ molar and cuspid relationship was achieved.

The effects of fluor-hydroxyapatite coating on the osseointegration and peri-implantitis of orthodontic micro-implants / 实用口腔医学杂志

Objective:To study the effects of fluor-hydroxyapatite (FHA) coating titanium alloy on the osseointegration and peri-implantitis of orthodontic micro-implant.Methods:Titanium of FHA alloy (FHA group) and titanium alloy(control group) orthodontic micro-implants were respectively planted into buccal alveolar bone in mandibular premolar area of rabbits.Scanning electron microscope was used to observe the osseointegration around the micro-implants.ELISA was employed to detect TNF-α in the gingival crevicular fluid around the implants.Results:The FHA-coating titanium alloy orthodontic micro-implants led to higher bone density,smaller marrow cavity,and lower TNF-α level and shorter lasting period of TNF-α over-expression than the controls (P ＜ 0.05).Conclusion:The FHA-coating titanium alloy orthodontic micro-implant has better histocompatibility and may inhibit peri-implantitis.