Therapeutic Efficacy of an Erythromycin-Loaded Coaxial Nanofiber Coating in a Rat Model of S. aureus-Induced Periprosthetic Joint Infection.

Implant surface nanofiber (NF) coatings represent an alternative way to prevent/treat periprosthetic joint infection (PJI) via local drug release. We developed and characterized a coaxial erythromycin (EM)-doped PLGA/PCL-PVA NF coating. The purpose of this study was to determine the efficacy of EM-NF coatings (EM0, no EM, EM100 (100 mg/mL), and EM1000 (1000 mg/mL) wt/wt) in a rat PJI model. A strong bond of the EM-NF coating to the surface of titanium (Ti) pins was confirmed by in vitro mechanical testing. Micro-computed tomography (mCT) analysis showed that both EM100 and EM1000 NF effectively reduced periprosthetic osteolysis compared to EM0 at 8 and 16 weeks after implantation. Histology showed that EM100 and EM1000 coatings effectively controlled infection and enhanced periprosthetic new bone formation. The bone implant contact (BIC) of EM100 (35.08%) was higher than negative controls and EM0 (3.43% and 0%, respectively). The bone area fraction occupancy (BAFO) of EM100 (0.63 mm2) was greater than controls and EM0 (0.390 mm2 and 0.0 mm2, respectively). The BAFO of EM100 was higher than that of EM1000 (0.3 mm2). These findings may provide a basis for a new implant surface fabrication strategy aimed at reducing the risks of defective osseointegration and PJI.

Repair of a rat calvaria defect with injectable strontium (Sr)-doped polyphosphate dicalcium phosphate dehydrate (P-DCPD) ceramic bone grafts.

The trace element strontium (Sr) enhances new bone formation. However, delivering Sr, like other materials, in a sustained manner from a ceramic bone graft substitute (BGS) is difficult. We developed a novel ceramic BGS, polyphosphate dicalcium phosphate dehydrate (P-DCPD), which delivers embedded drugs in a sustained pattern. This study assessed the in vitro and in vivo performance of Sr-doped P-DCPD. In vitro P-DCPD and 10%Sr-P-DCPD were nontoxic and eluents from 10%Sr-P-DCPD significantly enhanced osteoblastic MC3T3 cell differentiation. A sustained, zero-order Sr release was observed from 10%Sr-P-DCPD for up to 70 days. When using this BGS in a rat calvaria defect model, both P-DCPD and 10% Sr-P-DCPD were found to be biocompatible and biodegradable. Histologic data from decalcified and undecalcified tissue showed that 10%Sr-P-DCPD had more extensive new bone formation compared with P-DCPD 12-weeks after surgery and the 10%Sr-P-DCPD had more organized new bone and much less fibrous tissue at the defect margins. The new bone was formed on the surface of the degraded ceramic debris within the bone defect area. P-DCPD represented a promising drug-eluting BGS for repair of critical bone defects.

Electrospun polyvinyl alcohol-collagen-hydroxyapatite nanofibers: a biomimetic extracellular matrix for osteoblastic cells.

The failure of prosthesis after total joint replacement is due to the lack of early implant osseointegration. In this study polyvinyl alcohol-collagen-hydroxyapatite (PVA-Col-HA) electrospun nanofibrous meshes were fabricated as a biomimetic bone-like extracellular matrix for the modification of orthopedic prosthetic surfaces. In order to reinforce the PVA nanofibers, HA nanorods and Type I collagen were incorporated into the nanofibers. We investigated the morphology, biodegradability, mechanical properties and biocompatibility of the prepared nanofibers. Our results showed these inorganic-organic blended nanofibers to be degradable in vitro. The encapsulated nano-HA and collagen interacted with the PVA content, reinforcing the hydrolytic resistance and mechanical properties of nanofibers that provided longer lasting stability. The encapsulated nano-HA and collagen also enhanced the adhesion and proliferation of murine bone cells (MC3T3) in vitro. We propose the PVA-Col-HA nanofibers might be promising modifying materials on implant surfaces for orthopedic applications.

Poly(amidoamine) dendrimer-erythromycin conjugates for drug delivery to macrophages involved in periprosthetic inflammation.

Erythromycin (EM), an antibiotic that has been used for infectious diseases, is now gaining attention because of its novel anti-inflammatory effects. We explore a dendrimer-EM nanodevice for sustained treatment of orthopedic inflammation. To sustain pharmacological activity, EM was conjugated to poly(amidoamine) dendrimer (PAMAM) through an ester bond. A bifunctional PAMAM dendrimer was prepared having neutral hydroxy and reactive amine groups on the surface and was reacted with EM prodrug (EM-2'-glutarate). The cytotoxicity, efficacy and antibacterial properties were evaluated on macrophages (RAW 264.7 cells) associated with periprosthetic inflammation. The conjugate is noncytotoxic and showed significant reduction of nitrite level (by 42% as compared with untreated cells and free EM). The zone of inhibition of the conjugate on bacterial growth at different concentrations showed similar activity compared to free EM. The anti-inflammatory properties of EM combined with the targeting potential of the dendrimer can lead to sustained and targeted intracellular delivery. FROM THE CLINICAL EDITOR: In this study, a specific dendrimer-erythromycin conjugate nanodevice is investigated for the treatment of periprosthetic inflammation. The anti-inflammatory properties of erythromycin combined with the targeting potential of the dendrimer can lead to sustained and targeted intracellular delivery.

Properties of erythromycin-loaded polymeric dicalcium phosphate dehydrate bone graft substitute.

A self-setting, injectable polymeric dicalcium phosphate dehydrate bone graft substitute that is mechanically strong and has excellent cohesion was developed. We assessed the performance of erythromycin-loaded polymeric dicalcium phosphate dehydrate cement. Its properties include drug release, growth inhibition against Staphylococcus aureus and biocompatibility with osteoblastic MC3T3 cells. The impact of erythromycin loading on cement injectability, setting time, and mechanical strength were also evaluated. A sustained, low burst release of erythromycin was observed. Eluents collected from erythromycin-loaded cement showed a considerable zone of inhibition for up to 28 days. Direct contact of erythromycin-loaded cement discs with agar plate showed a similarly sizable zone of inhibition for up to 22 days. Degraded ceramic residues had strong zones of inhibition as well. While the erythromycin-loaded cement was injectable, a notable delay of the setting time was observed (49.2 ± 6.8 min) as compared with control (drug-free cement, 12.2 ± 2.6 min). A slight increase in compressive strength (60.83 ± 6.28 MPa) was observed in erythromycin-loaded cement as compared with control (59.41 ± 6.48 MPa). Erythromycin-loaded cement was biocompatible although reduced cell growth was observed in the presence of the cement eluent. We propose that the bactericidal efficacy of erythromycin-loaded cement was caused by the combined effects of erythromycin released and exposed on the contact surface of degrading ceramics. Our data may elucidate the future application of polymeric dicalcium phosphate dehydrate bone graft substitute for the treatment of orthopedic infections and opportunities to use other antibiotics and applications considering its comparable handling and mechanical strength to poly (methyl methacrylate) cements.

Efficacy of periprosthetic erythromycin delivery for wear debris-induced inflammation and osteolysis.

OBJECTIVES: We have reported that oral erythromycin (EM) inhibits periprosthetic tissue inflammation in a group of patients with aseptic loosening. The purpose of this study was to assess the efficacy of local, periprosthetic EM delivery in a rat model. METHODS: Uncoated Ti pins were press-fit into the right tibia of fourteen Sprague-Dawley rats following an intramedullar injection of UHMWPE (ultra high molecular weight polyethylene) particles. Revision surgeries were performed 2 months after the primary surgery. EM was applied to the Peri-Apatite™ (PA) layer of the titanium (Ti) pins. The previously implanted Ti pins were withdrawn and replaced with Ti pins coated either with (n = 7) or without (n = 7) EM. The rats were killed 1 month after "revision surgery". The EM efficacy was evaluated by (MicroCT) µCT and histology. RESULTS: µCT analysis showed that bone volume percentage (BV/TV) was significantly higher in the EM-treated group compared to the untreated group (p < 0.05). Histological analysis showed that EM treatment inhibits UHMWPE particle-induced periprosthetic tissue inflammation compared to the untreated group. CONCLUSION: This study demonstrated that periprosthetic EM delivery reduced periprosthetic inflammation and improved the quality of surrounding bone.

Comparing the release of erythromycin and vancomycin from calcium polyphosphate hydrogel using different drug loading methods.

Calcium polyphosphate (CPP) hydrogel is used to load erythromycin (EM) and vancomycin (VCM) by means of two loading methods: they are either added directly to the formed CPP hydrogel (Gel Mixture method) or mixed with CPP powders, followed by the formation of CPP-antibiotic hydrogel (Powder Mixture method). The release of loaded antibiotics from CPP hydrogel is measured up to 48 hr. Compared to Powder Mixture method, Gel Mixture method significantly reduced the burst release of embedded antibiotics. A significant change in CPP hydrogel Raman characteristic peaks is observed only in Gel Mixture method, indicating a close interaction between embedded antibiotics with CPP hydrogel matrix. In contrast, a similarity between characteristic peaks of CPP hydrogel and Powder Mixture method shows that antibiotic incorporation does not interfere with CPP gel formation, resulting in no ionic interaction between antibiotic and polyphosphate chains. Rheometer analysis further confirms that the hydrophobic nature of EM impacts the viscoelastic properties of CPP hydrogel, whereas the hydrophilic VCM exhibits a higher loading efficiency. The potential application of CPP hydrogel as a ceramic matrix for sustained drug release warrants further investigation.

Construction of Microunits by Adipose-Derived Mesenchymal Stem Cells Laden with Porous Microcryogels for Repairing an Acute Achilles Tendon Rupture in a Rat Model.

OBJECTIVE: Tissue engineering approaches seem to be an attractive therapy for tendon rupture. Novel injectable porous gelatin microcryogels (GMs) can promote cell attachment and proliferation, thus facilitating the repair potential for target tissue regeneration. The research objectives of this study were to assess the efficacy of tissue-like microunits constructed by multiple GMs laden with adipose-derived mesenchymal stem cells (ASCs) in accelerated tendon regeneration in a rat model. METHODS: Through a series of experiments, such as isolation and identification of ASCs, scanning electron microscopy, mercury intrusion porosimetry (MIP), laser scanning confocal microscopy and the CCK-8 test, the biocompatibility of GMs was evaluated. In an in vivo study, 64 rat right transected Achilles tendons were randomly divided into four groups: the ASCs+GMs group (microunits aggregated by multiple ASC-laden GMs injected into the gap), the ASCs group (ASCs injected into the gap), the GMs group (GMs injected into the gap) and the blank defect group (non-treated). At 2 and 4 weeks postoperatively, the healing tissue was harvested to evaluate the gross observation and scoring, biomechanical testing, histological staining and quantitative scoring. Gait analysis was performed over time. The 64 rats were randomly assigned into 4 groups: (1) micro-unit group (ASCs+GMs) containing ASC (105)-loaded 120 GMs in 60 µL DMEM; (2) cell control group (ASCs) containing 106 ASCs in 60 µL DMEM; (3) GM control group (GMs) containing 120 blank GMs in 60 µL DMEM; (4) blank defect group (Defect) containing 60 µL DMEM, which were injected into the defect sites. All animals were sacrificed at 2 and 4 weeks postsurgery (Table 1). RESULTS: In an in vitro study, GMs (from 126 µm to 348 µm) showed good porosities and a three-dimensional void structure with a good interpore connectivity of the micropores and exhibited excellent biocompatibility with ASCs. As the culture time elapsed, the extracellular matrix (ECM) secreted by ASCs encased the GMs, bound multiple microspheres together, and then formed active tendon tissue-engineering microunits. In animal experiments, the ASCs+GMs group and the ASCs group showed stimulatory effects on Achilles tendon healing. Moreover, the ASCs+GMs group was the best at improving the macroscopic appearance, histological morphology, Achilles functional index (AFI), and biomechanical properties of repair tissue without causing adverse immune reactions. CONCLUSION: Porous GMs were conducive to promoting cell proliferation and facilitating ECM secretion. The ASCs-GMs matrices showed an obvious therapeutic efficiency for Achilles tendon rupture in rats.

Inhibitory effects of erythromycin on wear debris-induced VEGF/Flt-1 gene production and osteolysis.

OBJECTIVES: A highly vascularized and inflammatory periprosthetic tissue augments the progress of aseptic loosening, a major clinical problem after total joint replacement. The purpose of this study is to investigate the effect of erythromycin (EM) on ultra high molecular weight polyethylene (UHMWPE) particle-induced VEGF/VEGF receptor 1 (Flt-1) gene production and inflammatory osteolysis in a mouse model. METHODS: UHMWPE particles were introduced into established air pouches on BALB/c mice, followed by implantation of calvaria bone from syngeneic littermates. EM treatment started 2 weeks after bone implantation (5 mg/kg day, i.p. injection). Mice without drug treatment as well as mice injected with saline alone were included. Pouch tissues were harvested 2 weeks after bone implantation. Expression of VEGF, Flt-1, RANKL, IL-1, TNF and CD68 was measured by immunostain and RT-PCR, and implanted bone resorption was analyzed by micro-CT (muCT). RESULTS: Exposure to UHMWPE induced pouch tissue inflammation, increase of VEGF/Flt-1 proteins, and increased bone resorption. EM treatment significantly improved UHMWPE particle-induced tissue inflammation, reduced VEGF/Flt-1 protein expression, and diminished the number of TRAP(+) cells, as well as the implanted bone resorption. CONCLUSION: This study demonstrated that EM inhibited VEGF and Flt-1 gene expression. The molecular mechanism of EM action on VEGF/Flt-1 signaling-mediated osteoclastogenesis warrants further investigation.

Airflow behavior changes in upper airway caused by different head and neck positions: Comparison by computational fluid dynamics.

The feasibility of computational fluid dynamics (CFD) to evaluate airflow characteristics in different head and neck positions has not been established. This study compared the changes in volume and airflow behavior of the upper airway by CFD simulation to predict the influence of anatomical and physiological airway changes due to different head-neck positions on mechanical ventilation. One awake volunteer with no risk of difficult airway underwent computed tomography in neutral position, extension position (both head and neck extended), and sniffing position (head extended and neck flexed). Three-dimensional airway models of the upper airway were reconstructed. The total volume (V) and narrowest area (Amin) of the airway models were measured. CFD simulation with an Spalart-Allmaras model was performed to characterize airflow behavior in neutral, extension, and sniffing positions of closed-mouth and open-mouth ventilation. The comparison result for V was neutral

Flow perfusion culture of MC3T3-E1 osteogenic cells on gradient calcium polyphosphate scaffolds with different pore sizes.

Calcium polyphosphate is a biodegradable bone substitute. It remains a challenge to prepare porous calcium polyphosphate with desired gradient porous structures. In this study, a modified one-step gravity sintering method was used to prepare calcium polyphosphate scaffolds with desired-gradient-pore-size distribution. The differences of porous structure, mechanical strength, and degradation rate between gradient and homogenous calcium polyphosphate scaffolds were evaluated by micro-computed tomography, scanning electron microscopy, and mechanical testing. Preosteoblastic MC3T3-E1 cells were seeded onto gradient and homogenous calcium polyphosphate scaffolds and cultured in a flow perfusion bioreactor. The distribution, proliferation, and differentiation of the MC3T3-E1 cells were compared to that of homogenous calcium polyphosphate scaffolds. Though no significant difference of cell proliferation was found between the gradient and the homogenous calcium polyphosphate scaffolds, a much higher cell differentiation and mineralization were observed in the gradient calcium polyphosphate scaffolds than that of the homogenous calcium polyphosphate scaffolds, as manifested by increased alkaline phosphatase activity (p < 0.05). The improved distribution and differentiation of cultured cells within gradient scaffolds were further supported by both (18)F-fluorine micro-positron emission tomography scanning and in vitro tetracycline labeling. We conclude that the calcium polyphosphate scaffold with gradient pore sizes enhances osteogenic cell differentiation as well as mineralization. The in vivo performance of gradient calcium polyphosphate scaffolds warrants further investigation in animal bone defect models.

Plasma-sprayed hydroxyapatite+titania composite bond coat for hydroxyapatite coating on titanium substrate.

A two-layer hydroxyapatite (HA)/HA+TiO(2) bond coat composite coating (HTH coating) on titanium was fabricated by plasma spraying. The HA+TiO(2) bond coat (HTBC) consists of 50 vol% HA and 50 vol% TiO(2) (HT). The microstructural characterization of the HTH coatings before and after heat treatment was conducted by using scanning electron microscopy (SEM), electron probe microanalyser (EPMA), X-ray diffractometer (XRD) and transmission electron microscopy (TEM), in comparison with that of HT coating and pure HA coating. The results revealed that HA and TiO(2) phases layered in an alternating pattern within the HTBC, and the HTBC bonded well to HA top coating (HAT coating) and Ti substrate. The as-sprayed HT coating consists mainly of crystalline HA, rutile TiO(2) and amorphous Ca-P phase. The post-spray heat treatment at 650 degrees C for 120 min effectively restores the structural integrity of HA by transforming non-HA phases into HA. It was found that there exists interdiffusion of the elements within the HTBC, but no chemical product between HA and TiO(2), such as CaTiO(3) was formed. The cross-sectional morphologies confirmed that there is a shift towards a relatively tighter bonding from the HAT coating/HTBC interface in the as-sprayed HTH coating to the HTBC/Ti substrate interface in the heat-treated HTH coating. On quenching the coatings into water, the surface cracking indicates more apparently the positive effect of the HTBC on the decrease of residual stress in HAT coating. The in situ surface cracking also suggests that the stress on the surface of the HTH coating is stable under subjection to a repetitious heat treatment. The toughening and strengthening of HTBC is thought to be mainly due to TiO(2) as obstacles embarrassing cracking, the reduction of the near-tip stresses resulting from stress-induced microcracking and the decrease of CTE mismatch. In the HTH composite coating, the HAT coating is toughened by the decreased CTE mismatch with Ti through the addition of HTBC, which bonds well to the Ti substrate via its TiO(2) hobnobbing with the Ti oxides formed on Ti substrate.

Implant wear induced inflammation is mitigated in CX3CR1(-/-) mice.

Wear debris-induced monocyte recruitment plays a key role in the formation of chronic periprosthetic tissue inflammation associated with aseptic loosening. The purpose of this study was to investigate the role(s) of chemokine receptor CX3CR1 in ultra high molecular weight polyethylene (UHMWPE) particle-induced tissue inflammation using a murine air pouch model developed in CX3CR1 knockout (CX3CR1(-/-) ) mice. UHMWPE debris or saline were introduced into established air pouches on CX3CR1(-/-) and CX3CR1(+/+) mice. Pouch tissues were collected 7 days after UHMWPE inoculation. Results showed that UHMWPE stimulation induced strong pouch tissue inflammation in CX3CR1(+/+) mice, as manifested by inflammatory cellular infiltration (mainly macrophages), pouch tissue proliferation, and increased gene expression of IL-1ß and TNFα. UHMWPE-induced inflammation was significantly mitigated in CX3CR1(-/-) mice, as manifested by reduction of tissue inflammation (pouch thickness and cell density), inflammatory cytokine production (IL-1ß and TNFα) and macrophage accumulation. The observations support the hypothesis that the activation of the CX3CR1 chemokine pathway contributes to the severity of UHMWPE particle-induced tissue inflammation, and suggests that CX3CR1 signaling is involved in the recruitment of monocytes to the wear debris-containing inflammatory tissues. Blocking of CX3CR1 pathway may represent a viable therapeutic approach to the prevention and treatment of patients with aseptic loosening.

Coaxial PCL/PVA electrospun nanofibers: osseointegration enhancer and controlled drug release device.

The failure of prosthesis after total joint replacement is mainly due to dysfunctional osseointegration and implant infection. There is a critical need for orthopedic implants that promote rapid osseointegration and prevent bacterial colonization, particularly when placed in bone compromised by disease or physiology of the patients. The aim of this study was to fabricate a novel coaxial electrospun polycaprolactone (PCL)/polyvinyl alcohol (PVA) core-sheath nanofiber (NF) blended with both hydroxyapatite nanorods (HA) and type I collagen (Col) (PCL(Col)/PVA(HA)). Doxycycline (Doxy) and dexamethasone (Dex) were successfully incorporated into the PCL(Col)/PVA(HA) NFs for controlled release. The morphology, surface hydrophilicity and mechanical properties of the PCL/PVA NF mats were analyzed by scanning electron microscopy, water contact angle and atomic force microscopy. The PCL(Col)/PVA(HA) NFs are biocompatible and enhance the adhesion and proliferation of murine pre-osteoblastic MC3T3 cells. The release of Doxy and Dex from coaxial PCL(Col)/PVA(HA) NFs showed more controlled release compared with the blended NFs. Using an ex vivo porcine bone implantation model we found that the PCL(Col)/PVA(HA) NFs bind firmly on the titanium rod surface and the NFs coating remained intact on the surface of titanium rods after pullout. No disruption or delamination was observed after the pullout test. These findings indicate that PCL(Col)/PVA(HA) NFs encapsulating drugs have great potential in enhancing implant osseointegration and preventing implant infection.

Poly(vinyl alcohol)/collagen/hydroxyapatite hydrogel: properties and in vitro cellular response.

The objective of this study was to develop "bone-like" poly(vinyl alcohol) (PVA)/hydroxyapatite (HA)/type I collagen (Col) hydrogel composites that stimulate adhesion, proliferation, and differentiation of osteoblastic cells. The hydrogel composites were prepared by mixing PVA with nanoscale HA and Col using a physical mixing method. The concentration of the components was optimized during formulation development. PVA/Col/HA hydrogels were characterized for viscoelasticity, degree of swelling, mechanical strength, embedded erythromycin drug release, and cellular response of both osteoblastic MC3T3 cells and RAW 264.7 macrophage cells. Compressive strength tests confirmed that the PVA coating possessed greater elasticity and was mechanically enhanced by the freeze-thaw treatment. PVA/Col/HA gel is biocompatible and nontoxic to MC3T3 preosteoblasts, and the reinforcement from HA and Col reduced the inflammatory response from macrophages. Our findings demonstrate that PVA composites are biocompatible, and enhance cell adhesion, proliferation, and differentiation in vitro. We propose that PVA/Col/HA hydrogels represent one of the promising implant surface coating matrices for the improvement of implant osseointegration.

A novel alkali metals/strontium co-substituted calcium polyphosphate scaffolds in bone tissue engineering.

Our purpose of this study is to develop potassium or sodium/strontium co-substituted calcium polyphosphate (K/Sr-CPP or Na/Sr-CPP) bioceramics in application of bone repairing scaffold. The incorporation of K, Na, and Sr into CPP substrate via a calcining-sintering process was confirmed by X-ray diffractometry and inductively coupled plasma atomic emission spectroscopy. In vitro degradation study of co-substituted CPP indicated the incorporation of alkali metal elements promoted the degradability of CPP, and the scanning electron microscope showed the apatite-like minerals were precipitated on the surface of co-substituted CPP. The compress resistant strength of co-substituted CPP was elevated by dopants. The MTT assay and confocal laser-scanning microscope on osteoblasts culturing with co-substituted CPP showed no cytotoxicity. The cell proliferation on co-substituted CPP was even better than others. Thus, this co-substituted CPP bioceramics might have potential of applications in orthopedic field.

A novel strontium-doped calcium polyphosphate/erythromycin/poly(vinyl alcohol) composite for bone tissue engineering.

It is our goal to develop bactericidal bone scaffolds with osteointegration potential. In this study, poly(vinyl alcohol) (PVA) coating (7%) was applied to an erythromycin (EM)-impregnated strontium-doped calcium polyphosphate (SCPP) scaffold using a simple slurry dipping method. MicroCT analysis showed that PVA coating reduced the average pore size and the percentage of pore interconnectivity to some extent. Compressive strength tests confirmed that the PVA coating significantly increased material elasticity and slightly enhanced the scaffold mechanical strength. It was also confirmed that the PVA coatings allowed a sustained EM release that is controlled by diffusion through the intact PVA hydrogel layer, irrespective of the drug solubility. PVA coating did not inhibit the EM bioactivity when the scaffolds were immersed in simulated body fluid for up to 4 weeks. EM released from SCPP-EM-PVA composite scaffolds maintained its capability of bacterial growth (S. aureus) inhibition. PVA coating is biocompatible and nontoxic to MC3T3 preosteoblast cells. Furthermore, we found that SCPP-EM-PVA composite scaffolds and their eluants remarkably inhibited RANKL-induced osteoclastogenesis in a murine RAW 264.7 macrophage cell line. Thus, this unique multifunctional bioactive composite scaffold has the potential to provide controlled delivery of relevant drugs for bone tissue engineering.

[Series orthodontic treatment on teeth transposition of maxillary canine and lateral incisor].

OBJECTIVE: To explore the treatment on teeth transposition of maxillary canine and lateral incisor in order to improve the clinical treatment effect. METHODS: Eleven patients with transposition maxillary canine and lateral incisor were treated with the method: Expand space, artificial reverse occlusion of transpositional lateral incisor to give way, transpositional lateral canine distalization and controlling root, mesial movement of lateral incisor with tongue arch, interactive controlling roots and retention with tongue fixed retaining appliance. RESULTS: Eleven patients had satisfactory treatment effect, with tidy dentition and parallel teeth roots of transpositional canine and lateral incisor. CONCLUSION: Series orthodontic treatment on teeth transposition of maxillary canine and lateral incisor can effectively improve the clinical treatment effect and shorten the treatment time.

[The fabrication and clinical application of semi-fixed mandibular lingual arch expansion appliance].

Semi-fixed mandibular lingual arch expansion appliance is composed of a mandibular molar band, a keyway and arch expansion spring. The arch expansion spring are used to expand maxillary arch symmetrically or asymmetrically when bolts of the two ends are inset into keyways. Dental arch expansion appliance for 25 patients with mandibular arch stenosis showed that semi-fixed mandibular lingual arch expansion had good effect and could be used to expand mandibular arch.

[Short-term outcome of the acellular dermal matrix in dental implant surgical sites].

OBJECTIVE: To evaluate the clinical short-term results of the acellular dermal matrix for guided bone regeneration. METHODS: Sixty-four patients with bone defect in anterior maxillary area (average bone width: 3 mm) were included. Ridge-splitting technique with simultaneous placement of implants and artificial bone material implantation was performed in 21 patients (non-membrane group). Forty-three patients received the same procedure but with acellular dermal matrix covering the surgical sites (membrane group). The patients were followed up for three months and the new bone formation was checked in clinic and by X-ray. RESULTS: Three months after operation, the membrane group showed good osseointegration and high bone density over the implant cover screws. In the second operation, the membranes became thinner and the new bone fully covered the implant in the membrane group. The labial bone exhibited slight absorption and labial surface of 7 implants in 7 patients was exposed in non-membrane group. The width and the height of the ridge in the second operation were greater in membrane group than in non-membrane group (P < 0.05). CONCLUSIONS: The acellular dermal matrix can effectively resist the growth of soft tissue to allow bone regeneration around the implant.