Estimation of the reproduction number and identification of periodicity for HFMD infections in northwest China.

Repeated outbreaks of Hand, foot and mouth disease (HFMD) infections have been observed in recent decades and dominated by various enteroviral serotypes. In particular, enterovirus 71 (EV-A71), coxsackievirus A16 (CV-A16) and coxsackievirus A6 (CV-A6) dominated the prevalence of HFMD infections alternatively in recent years with various outbreak sizes in Baoji, a city of Shaanxi Province in Northwest China. Estimating the reproduction number for various enteroviruses serotypes in northwest China (north temperate zone) and identification of cyclicity of HFMD infections are therefore an issue of great importance for future epidemics prediction and control. The basic/effective reproduction numbers for EV-A71, CV-A16 and CV-A6 were estimated based on daily new cases in 2010, 2011 and 2018, respectively, in which the corresponding pathogen dominated the epidemic. Two different methods based on serial interval were adopted and the basic reproduction number were estimated to be in the range of (1.33, 1.46) for CV-A16, (1.20, 1.29) for EV-A71, and (1.38, 1.59) for CV-A6, respectively. The estimated daily effective reproduction numbers significantly fluctuated before June or after July but varied mildly in (0.5,2) in around June to July for three serotypes. The weekly effective reproduction number for HFMD was estimated based on weekly new cases from year 2010 to 2018, and in most years it peaked in the range of (1.6,2.0) in February to March as well as in the range of (1.0,1.2) in September to October. The wavelet analysis based on the time series of HFMD cases from 2008 to 2018 showed obvious annual and semi-annual cyclicity, while the inter-annual cycles are infeasible. In this study we found that CV-A6 shows the greatest transmission ability among these three pathogens while EV-A71 exhibits the weakest ability of transmission, and moreover, the estimated values of basic reproduction number in northwest China are lower than those in Singapore, Hongkong and Guangdong, which may be due to different climatic circumstances.

PVP intercalated metallic WSe2 as NIR photothermal agents for efficient tumor ablation.

Transition metal dichalogenides (TMDCs) with unique layered structures hold promising potential as transducers for photothermal therapy. However, the low photothermal conversion efficiency and poor stability in some cases limit their practical applications. Herein, we demonstrate the fabrication of ultrathin homogeneous hybridized TMDC nanosheets and their use for highly efficient photothermal tumor ablation. In particular, the nanosheets were composed of metallic WSe2 intercalated with polyvinylpyrrolidone (PVP), which was facilely prepared through a solvothermal process from the mixture of selenourea crystals, WCl6 powder along with PVP polymeric nanogel. Our characterizations revealed that the obtained nanosheets exhibited excellent photothermal conversion efficiency, therapeutic demonstration with improved biocompatibility and physiological stability attributing to the combined merits of metallic phase of WSe2 and hydrophilic PVP insertion. Both the histological analysis of vital organs and in vitro/in vivo tests confirmed the nanosheets as actively effective and biologically safe in this phototherapeutic technique. Findings from this non-invasive experiment clearly emphasize the explorable therapeutic efficacy of the layered-based hybrid agents in future cancer treatment planning procedures.

Psychological well-being, dental esthetics, and psychosocial impacts in adolescent orthodontic patients: A prospective longitudinal study.

INTRODUCTION: We examined the role of adolescent orthodontic patients' psychological well-being attributes (self-esteem, general body image, and positive and negative affects) and the clinical indicators of dental esthetics (orthodontists' ratings on the Index of Orthodontic Treatment Need-Aesthetic Component [IOTN-AC]), and their changes from pretreatment to posttreatment as predictors of the psychosocial impact of dental esthetics. METHODS: In this prospective longitudinal study, 1090 adolescent orthodontic patients seeking treatment at the Stomatological Hospital of Chongqing Medical University in China (mean age, 14.25 years; SD, 2.03 years) were assessed before treatment, and 68.99% (n = 752) were assessed after treatment. All subjects completed a questionnaire measuring psychological well-being attributes and 3 components of the Psychosocial Impact of Dental Aesthetics (perceptive, cognitive-affective, and social-functional). Clinical indicators of dental esthetics were measured by 3 orthodontists using the IOTN-AC. RESULTS: Substantial enhancement from pretreatment to posttreatment was found in all 3 Psychosocial Impacts of Dental Aesthetics components, confirming the positive effects of orthodontic treatment on oral health-related quality of life. Psychosocial impact of dental esthetics at baseline and improvement from pretreatment to posttreatment were found to be predicted by the patients' psychological well-being attributes (self-esteem, general body image, and negative affect) and the clinical indicators (orthodontists' rating on the IOTN-AC) at baseline, as well as their pretreatment to posttreatment change. Psychological well-being attributes had comparable or greater contribution to the Psychosocial Impact of Dental Aesthetics at baseline as well as greater improvement after treatment than the clinical indicators. These biopsychological models explained 29% to 43% of the variances in psychosocial impacts of dental esthetics outcome at baseline and about 33% of the variance in pretreatment to posttreatment improvement. CONCLUSIONS: This study establishes a biopsychological model for understanding the psychosocial impact of dental esthetics and its improvement after orthodontic treatment among adolescent orthodontic patients. The findings highlight the importance of psychological parameters in orthodontic research and clinical practice.

Visualization and quantitation of fetal movements by real-time three-dimensional ultrasound with live xPlane imaging in the first trimester of pregnancy.

AIM: To prove whether real-time three-dimensional (3D) ultrasound with live xPlane imaging is better in observing fetal movements than standard ultrasound imaging. METHODS: 50 healthy women with singleton pregnancies (22-43 years old) at 11 to 14 weeks of gestation underwent real-time 3D ultrasound examination with live xPlane imaging from July 2014 to February 2015. The incidence and frequency of 10 fetal movement patterns in 10 minutes were evaluated, including general movements (GMs), isolated arm movements, isolated leg movements, hiccup, stretching, breathing, startle, jaw opening, isolated head retroflexion, and isolated head anteflexion. The correlation between gestational age and frequency of each fetal movement pattern was analyzed. RESULTS: GM had the highest incidence (100%), followed by startle (84%) and isolated arm movements (68%). Their median frequency was 5 (IQR 3-6), 5 (IQR 1.75-11.5), and 1 (IQR 0-2), respectively. GM (Z=5.875, P<0.001) and startle (Z=5.302, P<0.001) had significantly higher frequency than isolated arm movements. The other 7 fetal movement patterns had much lower incidence and frequency. The frequency of GM was positively correlated with gestational age (r=0.360, P=0.010). CONCLUSION: Real-time 3D ultrasound with live x Plane imaging was shown to be a feasible tool for observing fetal movements.

Biomechanical effects of corticotomy approaches on dentoalveolar structures during canine retraction: A 3-dimensional finite element analysis.

INTRODUCTION: Corticotomy has proven to be effective in facilitating orthodontic tooth movement. There is, however, no relevant study to compare the biomechanical effects of different corticotomy approaches on tooth movement. In this study, a series of corticotomy approaches was designed, and their impacts on dentoalveolar structures were evaluated during maxillary canine retraction with a 3-dimensional finite element method. METHODS: A basic 3-dimensional finite element model was constructed to simulate orthodontic retraction of the maxillary canines after extraction of the first premolars. Twenty-four corticotomy approach designs were simulated for variations of position and width of the corticotomy. Displacement of the canine, von Mises stresses in the canine root and trabecular bone, and strain in the canine periodontal ligament were calculated and compared under a distal retraction force directed to the miniscrew implants. RESULTS: A distal corticotomy cut and its combinations showed the most approximated biomechanical effects on dentoalveolar structures with a continuous circumscribing cut around the root of the canine. Mesiolabial and distopalatal cuts had a slight influence on dentoalveolar structures. Also, the effects decreased with the increase of distance between the corticotomy and the canine. No obvious alteration of displacement, von Mises stress, or strain could be observed among the models with different corticotomy widths. CONCLUSIONS: Corticotomies enable orthodontists to affect biomechanical responses of dentoalveolar structures during maxillary canine retraction. A distal corticotomy closer to the canine may be a better option in corticotomy-facilitated canine retraction.

Three-dimensional quantification of orthodontic root resorption with time-lapsed imaging of micro-computed tomography in a rodent model.

OBJECTIVE: Despite various X-ray approaches have been widely used to monitor root resorption after orthodontic treatment, a non-invasive and accurate method is highly desirable for long-term follow up. The aim of this study was to build a non-invasive method to quantify longitudinal orthodontic root resorption with time-lapsed images of micro-computed tomography (micro-CT) in a rodent model. MATERIALS AND METHODS: Twenty male Sprague Dawley (SD) rats (aged 6-8 weeks, weighing 180-220 g) were used in this study. A 25 g orthodontic force generated by nickel-titanium coil spring was applied to the right maxillary first molar for each rat, while contralateral first molar was severed as a control. Micro-CT scan was performed at day 0 (before orthodontic load) and days 3, 7, 14, and 28 after orthodontic load. Resorption of mesial root of maxillary first molars at bilateral sides was calculated from micro-CT images with registration algorithm via reconstruction, superimposition and partition operations. RESULTS: Obvious resorption of mesial root of maxillary first molar can be detected at day 14 and day 28 at orthodontic side. Most of the resorption occurred in the apical region at distal side and cervical region at mesiolingual side. Desirable development of molar root of rats was identified from day 0 to day 28 at control side. The development of root concentrated on apical region. CONCLUSIONS: This non-invasive 3D quantification method with registration algorithm can be used in longitudinal study of root resorption. Obvious root resorption in rat molar can be observed three-dimensionally at day 14 and day 28 after orthodontic load. This indicates that registration algorithm combined with time-lapsed images provides clinic potential application in detection and quantification of root contour.

Anesthesia for pediatric day-case dental surgery: a study comparing the classic laryngeal mask airway with nasal trachea intubation.

BACKGROUND: To study sevoflurane inhalation general anesthesia using the laryngeal mask airway (LMA) and nasal endotracheal (ET) intubation to maintain the airway in pediatric day-case dental surgery. METHODS: A total of 171 children aged 2 to 7 years received elective day-case dental surgical procedure under general anesthesia. Children were randomly grouped into LMA groups (L) and nasal ET intubation group (N). In L groups, LMA was inserted after induction of anesthesia using 8% sevoflurane and were allowed to breathe spontaneously. Rocuronium and remifentanil were given intravenously during 8% sevoflurane induction by nasal ET intubation in the N group . The time of anesthetic induction, maintenance, recovery, surgical access, and bispectral index score were recorded. Postoperative nausea and vomiting and the incidence of adverse events during induction and recovery period were also recorded. RESULTS: The insertion time of LMA was significantly shorter than nasal ET (P < 0.05). The incidence of airway complications, the surgeons' access, and bispectral index were not different between the 2 groups. However, recovery time was significantly shorter in group L (P < 0.05). The incidence of sore throat and postoperative nausea and vomiting (P < 0.01) were much less in group L as well. CONCLUSIONS: Sevoflurane inhalation anesthesia through LMA is a safe and reliable method for pediatric day-case dental surgery.

Early orthodontic intervention followed by fixed appliance therapy in a patient with a severe Class III malocclusion and cleft lip and palate.

This case report describes the treatment of a girl, age 11 years 10 months, with a cleft lip and palate and a postsurgical scar. The clinical examination showed a concave profile, a retrusive maxilla, an asymmetric face, severe dental crowding, a Class III dental relationship, and a complete dental crossbite. Maxillary expansion and distraction, chincap, and high-pull headgear were used to moderate the skeletal discrepancy. These approaches, combined with tooth extraction and fixed orthodontic appliances, finally established a functional and esthetic occlusal relationship, normal overjet and overbite, and a well-balanced facial appearance.

[A comparative study on three-dimensional movement of anterior teeth between applying MDD appliances and applying three common fixed appliances in the initial alignment stage].

Typodont models of bilateral canines gingival displaced vertically for 3 mm and bilateral lateral incisors palatal displaced horizontally for 3 mm are made and every kind of the two kind models was divided into four groups: MDD, MBT, self-ligating and Tip-Edge. Each group of the two kinds of models had 5 models, so a total of 40 models for the two kinds of models were set up. The experimental models were aligned with a 0.30 mm of nickel titanium round wire in a water-bath with constant temperature 45 degrees C for 30 minutes. The three-dimensional digital images of the experimental models before and after the water bath were obtained by scanning with the three dimensional optical scanner ATOS. Geomagic software was used to overlap the digital images taken before and after the water bath treatment. The vertical changes of sign points of canines, the movements of sign points of lateral incisors in the sagittal plane and the horizontal plane were quantified by using the Color map. The data was then processed by a two-factor analysis of variance by using SAS 9.2 software package. Analysis of the results shows that the vertical changes of sign points of canines , the movements of sign points of lateral incisors in the sagittal plane and the horizontal plane of MDD group are all less than those in the other three groups, a statistically significant difference (P < 0.0001). And the size of the teeth displacement is directly related to the size of orthodontic force on the typodont models. Thus the preliminary results suggest that MDD appliance might have advantages of light force in the alignment stage, and that the possible relevant factors are the improvement of its sub-slot and the single ligation wing design.

[Research on ultrasonic permeability of low intensity pulsed ultrasound through PTFE membrane and Bio-Gide collagen membrane].

The aim of the present study was to detect the transmission rate of ultrasonic low intensity pulsed ultrasound (LIPUS) through polytetrafluoroethylene (PTFE) membrane (Thickness: 0.01 mm) and Bio-Gide collagen membrane, and to provide the basis for the barrier membrane selection on the study of LIPUS combined with guided tissue regeneration (GTR). The ultrasonic (LIPUS, frequency 1.5 MHz, pulse width 200 micros, repetition rate 1.0 kHz) transmission coefficient of the two kinds of barrier membrane were detected respectively through setting ten groups from 10 to 100mW/cm2 every other 10 mW/cm2. We found in the study that the ultrasonic transmission coefficient through 0.01 mm PTFE membrane was 78.1% to 92.%, and the ultrasonic transmission coefficient through Bio-Gide collagen membrane was 43.9% to 55.8%. The ultrasonic transmission coefficient through PTFE membrane was obviously higher than that through Bio-Gide collagen membrane. The transmission coefficient of the same barrier membrane of the ultrasonic ion was statistically different under different powers (P < 0.05). The results showed that the ultrasonic transmittance rates through both the 0.01 mm PTFE membrane and Bio-Gide collagen membrane were relatively high. We should select barrier membranes based on different experimental needs, and exercise ultrasonic transmission coefficient experiments to ensure effective power.

Co-encapsulation of rutinoside and ß-carotene in liposomes modified by rhamnolipid: Antioxidant activity, antibacterial activity, storage stability, and in vitro gastrointestinal digestion.

The surfactant rhamnolipid (RL) was used to modify the liposomes. ß-carotene (ßC) and rutinoside (Rts) were utilized to generate co-encapsulated liposomes through an ethanol injection method that used both hydrophilic and hydrophobic cavities to fabricate a novel cholesterol-free composite delivery system. The RL complex-liposomes loaded with ßC and Rts (RL-ßC-Rts) showed higher loading efficiency and good physicochemical properties (size = 167.48 nm, zeta-potential = -5.71 mV, and polydispersity index = 0.23). Compared with other samples, the RL-ßC-Rts showed better antioxidant activities and antibacterial ability. Moreover, dependable stability was uncovered in RL-ßC-Rts with still 85.2% of ßC storage from nanoliposome after 30 days at 4°C. Furthermore, in simulated gastrointestinal digestion, ßC exhibited good release kinetic properties. The present study demonstrated that liposomes constructed from RLs offer a promising avenue for the design of multicomponent nutrient delivery systems using both hydrophilic.

Bone morphogenetic protein-9 induces osteogenic differentiation of rat dental follicle stem cells in P38 and ERK1/2 MAPK dependent manner.

Dental follicle stem cells are a group of cells possessing osteogenic, adipogenetic and neurogenic differentiations, but the specific mechanism underlying the multilineage differentiation remains still unclear. Great attention has been paid to bone morphogenetic protein-9 (BMP-9) due to its potent osteogenic activity. In the present study, rat dental follicle stem cells were isolated and purified, and cells of passage 3 underwent adenovirus mediated BMP-9 gene transfection to prepare dental follicle stem cells with stable BMP-9 expression. Detection of alkaline phosphatase (ALP) and calcium deposition showed dental follicle stem cells transfected with BMP-9 gene could significantly promote the osteogenesis. In addition, SB203580 and PD98059 were employed to block the p38 mitogen-activated protein kinase (p38MAPK) and extracellular signal-regulated kinase (ERK1/2), respectively. Detection of ALP and calcium deposition revealed the BMP-9 induced osteogenic differentiation of dental follicle stem cells depended on MAPK signaling pathway.

[Effect of low-intensity pulsed ultrasound on periodontitis in Beagle dogs].

OBJECTIVE: To investigate the effect of low intensity pulsed ultrasound (LIPUS) on periodontitis in Beagle dogs. METHODS: The animal model of chronic periodontitis was established with elastic ligature-induced alveolar bone defect in Beagle dogs. LIPUS with different intensity (50 mW/cm2, 100 mW/cm2) pulse wave and 50 mW/cm2 continuous wave, 1.5 MHz of frequency, 200 micros of pulse width modulated signal, and 1 kHz of repetition rate were applied to the dogs for 8 weeks (once a day and 20 minutes every time). The periodontal clinical examinations and histological biopsy were performed. RESULTS: With increased exposure to LIPUS, gum tissue swelling of the dogs was reduced. The plaque index (PLI), gingival index (GI), pocket depth (PD) of the treatment groups were lower than the control groups (P < 0.05). No significant gingival recession, attachment loss or furcation was found. The histological examination revealed that there was no obvious gingival hyperplasia in epithelial tissues, but there were significant activities in relation to collagen formation, decrease of bone resorption, and generation of active osteoblasts. CONCLUSION: LIPUS may help repair periodontal tissues and should be considered in guided tissue regeneration (GTR).

[Biomechanical study of "mandible-temporomandibular joint" under different loading angles with forsus].

OBJECTIVE: To identify the best loading angle with Forsus for mandible-temporomandibular joint. METHODS: The changes in stress, displacement and rotation of "mandible-temporomandibular joint" were tested under -30 degrees, -15 degrees, 0 degrees, 15 degrees and 25 degrees of loading angles using a primary three dimensional finite element model. RESULTS: From 0 degrees to 25 degrees, with the increases of loading angles the displacement gradually increased. The maximum displacement occurred at chin, with 1.692 mm, 3.456 mm and 4.630 mm displacement under 0 degrees, 15 degrees and 25 degrees respectively. The maximum displacement occurred at the alveolar ridge under -15 degrees loading, which was 0.069 mm. No special stress concentration region was identified. The displacements from infradentale to pogonion gradually increased under all conditions except for the -15 degrees loading. With the loading angles deviated from the baseline farther, the porrect displacements of chin and the counterclockwise rotation became more obvious. CONCLUSION: The loading angles of Forsus appliance should be controlled between 0 degrees and 25 degrees.

Tendon-inspired fibers from liquid crystalline collagen as the pre-oriented bioink.

Nature provides rich bionic resources for the construction of advanced materials with excellent mechanical properties. In this work, inspired by animal tendons, a bionic collagen fiber was developed using collagen liquid crystals as the pre-oriented bioink. The texture of liquid crystalline collagen observed from polarized optical microscopy (POM) showed the specific molecular pre-orientation. Meanwhile, the collagen spinning liquids exhibited a minimal rise in viscosity upon increasing concentration from 60 to 120 mg/mL, indicating the feasible processability. The collagen fiber, which was prepared via wet spinning without being denatured, exhibited the favorable orientation of fibrils along its axis as observed with FESEM and AFM. Thanks to the synergistic effects between pre-orientation and shearing orientation, the maximum tensile strength and Young's modulus of collagen fibers reached 9.98 cN/tex (219.29 ± 22.92 MPa) and 43.95 ± 1.11 cN/tex (966.20 ± 24.30 MPa), respectively, which were also analogous to those of tendon. In addition, the collagen fiber possessed a desirable wet strength. Benefiting from the natural tissue affinity of collagen, the as-prepared bionic collagen fiber possessed excellent wound suture performance and biodegradability in vivo, which offers a new perspective for the potential of widespread applications of collagen fibers in biomedical fields.

Intraocular Lens with Mussel-Inspired Coating for Preventing Posterior Capsule Opacification via Photothermal Effect.

Phacoemulsification with implantation of intraocular lens (IOLs) has been widely applied as a standard treatment for cataract, which is the leading cause of vision impairment. However, it still remains a critical challenge to prevent posterior capsule opacification (PCO) in terms of postoperative visual quality. Herein, we report IOLs with mussel-inspired coatings for inhibiting lens epithelial cells and then preventing PCO through photothermal conversion effect. The mussel-inspired coatings are deposited on the nonoptical surface areas of IOLs, endowing the modified IOLs with efficient photothermal conversion property. The temperature can be facilely raised to 50-60 °C for the photothermal IOLs (PT-IOLs) by near-infrared (NIR) laser irradiation at a safe intensity of 0.3 W/cm2. These PT-IOLs display high capability of inhibiting lens epithelial cells (LECs) in vitro. Therefore, under routine NIR laser irradiation, New Zealand white rabbits implanted with the PT-IOLs demonstrate significantly lower evaluation of PCO (EPCO) scores than the control groups. The overall results indicate that our PT-IOLs provide a promising choice for the clinical prevention of PCO, thus opening a way to maintain the postoperative visual qualities for cataract patients.

The three-dimension finite element analysis of stress in posterior tooth residual root restored with postcore crown.

OBJECTIVE: Teeth that have been endodontically treated and restored with postcore crown may experience fracture sometimes. Some researchers have analyzed the stress of the anterior teeth after postcore crown restoration, but the stress of the posterior teeth after such restoration has not been reported. We used three-dimension finite element methods to analyze the stress magnitude and distribution of remaining dentin in posterior tooth residual root restored with postcore crown. The binding material, loading direction, number, length and material of posts were studied. METHODS: The models of residual root of maxillary first molar restored with postcore crown were created by CT scanning, mimics software and abaqus software. Different number, length and material of posts were used in the modeling. The posts were cemented with zinc-phosphate cement or composited resin. A load of 240 N was applied to the occlusal surface in four directions and tensile, shear, and von Mises stresses were calculated. RESULT: (i) The maximum stress on remaining dentin changed irregularly as the number and length of posts changed. (ii) The maximum stress on remaining dentin decreased slightly as elastic modulus of the material of posts increased. (iii) The maximum stress on bonding layer and remaining dentin was lower when bonded with resin luting agent than with zinc-phosphate cement. (iv) The maximum stress on remaining dentin increased markedly as loading angle increased. CONCLUSION: The number, length, material of posts, bonding material and loading angle all have influence on the magnitude and distribution of stress. The influence of loading angle is most apparent.

Pullout strength of miniscrews placed in anterior mandibles of adult and adolescent dogs: a microcomputed tomographic analysis.

INTRODUCTION: Miniscrews often loosen during orthodontic treatment, especially in teenage patients. The purposes of this study were to explore the differences of the pullout strengths of miniscrews placed in the anterior mandibles of adolescent and adult dogs and the structural parameters of peri-miniscrew bone, and to analyze the correlation between the pullout strengths and the variables of the peri-miniscrew bone structure. METHODS: Eight adult beagles and 8 young beagles with early permanent dentitions were used as experimental subjects. Two miniscrews were symmetrically placed in the anterior mandible of each dog several minutes before death. The bone density, relative bone volume, and cortical bone thickness were evaluated by micro-computed tomography, and the pullout strength of the miniscrew was tested with a testing machine. Regression analyses were used to study the relationship between pullout strength and bone density, relative bone volume, and cortical bone thickness. RESULTS: The values of bone density, relative bone volume, cortical bone thickness, and pullout strength were 781.94 + or - 21.46 mg of hydroxyapatite per cubic centimeter, 0.62 + or - 0.33, 1.14 + or - 0.11 mm, and 218.40 + or - 24.50 N for the adult dogs; and 713.61 + or - 13.08 mg of hydroxyapatite per cubic centimeter, 0.57 + or - 0.20, 1.07 + or - 0.86 mm, and 130.82 + or - 2.20 N for the young dogs, respectively. All pairs of pullout force and bone structural parameters had significant correlation coefficients. The pullout force showed the strongest correlation with bone density and the weakest with cortical bone thickness. CONCLUSIONS: The values of bone density, relative bone volume, cortical bone thickness, and the pullout strength of the adult group were higher than those of the young group. Furthermore, bone density is more sensitive in terms of showing pullout force compared with relative bone volume and cortical bone thickness.

Preparation of Coralline Hydroxyapatite Implant with Recombinant Human Bone Morphogenetic Protein-2-Loaded Chitosan Nanospheres and Its Osteogenic Efficacy.

OBJECTIVE: Spinal fusion is one of the most common surgical interventions for spine reconstruction. Despite the efforts to promote osteogenesis after spinal fusion, osteogenesis after spinal fusion remains a clinical challenge and new methods are still needed. The bone morphogenetic protein-2 (BMP-2) is a widely reported factor that can facilitate the osteogenesis in spinal fusion. In previous research, we found that the delivery of chitosan nanospheres could promote the effects of BMP-2 on osteogenic activity. The coralline hydroxyapatite (CHA) is one of the most frequently used implants in bone fusion. However, up to now no study has focused on the osteogenic efficacy of the CHA composite with recombinant human BMP-2 (rhBMP-2)-loaded chitosan nanospheres. This study aimed to investigate the effects of the CHA implant with rhBMP-2-loaded chitosan nanospheres on osteogenesis in spinal fusion. METHODS: The rhBMP-2-loaded microspheres and CHA composite (rhBMP-2 microspheres/CHA) were prepared and were used for implantation of the rats. All SD rats were divided into four groups: the rhBMP-2 microspheres/CHA composite group (containing 0.5 mg rhBMP-2), the rhBMP-2-loaded CHA (rhBMP-2/CHA) composite group (containing 0.5 mg rhBMP-2), the blank CHA group, and the negative control group. The microsphere morphology was scanned and analyzed using a scanning electron microscope. Micro-computed tomography examination and three-dimensional reconstruction were performed 4 weeks after the surgery. Hematoxylin and eosin staining was conducted for histological analysis. Both alkaline phosphatase (ALP) and calcium content were measured. RESULTS: The rhBMP-2-loaded CHA (rhBMP-2/CHA) composite was successfully prepared. Spherical regularity and a smooth and unwrinkled surface of the spheres were observed in all chitosan (CS)/rhBMP-2 microspheres. No side effects, infections, or abnormal behaviors were found in the animals. After 4 weeks of surgery, obvious new bone formation and bone fusion could be observed around the implant in both the rhBMP-2 microspheres/CHA composite group and the rhBMP-2/CHA composite group. No ectopic osteogenesis was found in the vertebral canal or other muscle tissues. After 4 weeks of implantation, in both the rhBMP-2 microspheres/CHA composite group and the rhBMP-2/CHA composite group, osteoid tissues could be found, and bone cells, bone marrow, and trabecular bone turned into mature sclerotin, obvious bone tissue formation could be also seen. Both ALP activity and calcium content in the rhBMP-2 microspheres/CHA composite group (6.52 ± 0.50 kat/g and 17.54 ± 2.49 µg/mg) were significantly higher than in all other groups. CONCLUSION: The composite with rhBMP-2-loaded CS nanospheres could enhance osteogenic efficacy and increase the ALP activity and calcium content. These results might provide a novel method for osteogenesis in spinal fusion and offer new insight into the role of BMP-2 in osteogenesis.

The influence of extraction on the stability of implanted titanium microscrews: a biomechanical and histomorphometric study.

PURPOSE: The purpose of this study was to explore the influence of extraction on the stability of implanted titanium microscrews. MATERIALS AND METHODS: Six male beagle dogs received 96 microscrews between the mesial and distal roots of the second, third, and fourth premolars and the first molar in both maxillae and mandibles. The third and fourth premolars were extracted from each dog. Test implants were placed near the extraction sites, and control implants were placed at a distance from the extraction sites. The bone remodeling process at the interface was studied through biomechanical pull-out testing, histomorphologic observation, and histomorphometric assessment after different amounts of healing time (1, 3, or 8 weeks). RESULTS: Two microscrews were loose in the test group at week 1. Near the extraction regions, both the peak pullout force at extraction (Fmax) and the bone-implant contact (BIC) of the microscrews were lower than that seen in the control group at week 1, but quickly surpassed the control groups at week 3. After 8 weeks of healing time, Fmax and BIC values between test and control groups exhibited no differences. The lowest BIC value was 10.12%, and the corresponding pull-out force was 100.23 N. At week 1, the inflammatory reaction at the bone-implant interface in the test groups was stronger than in the control groups. At week 3, many active osteoblasts gathered along the interface and a bone matrix excreted by osteoblasts around the microscrew were observed in the test group. CONCLUSIONS: A BIC of at least 10% provided resistance to orthodontic forces. For microscrews placed near extraction regions, the risk of loosening was highest in the first week following implant placement. The most active bone remodeling at the implant-bone interface occurred 3 weeks after implantation, especially for screws near extraction regions.