No long-term survival benefit with sustained-release 5-fluorouracil implants in patients with stages Ⅱ and Ⅲ gastric cancer

BACKGROUND The prognosis of gastric cancer in an advanced stage remains poor. The exact efficacy of the use of intraoperative sustained-release chemotherapy with 5-fluorouracil(5-FU) in advanced-stage gastric cancer is still unelucidated.AIM To explore the long-term survival benefit of using sustained-release 5-FU implants in stage Ⅱ and stage Ⅲ gastric cancer patients.METHODS Patients with gastric cancer in a locally advanced stage and who underwent an R0 radical resection between Jan 2014, to Dec 2016, in this single institution were included. Patients with pathological diagnoses other than adenocarcinoma were excluded. All included patients were grouped according to whether intraoperative sustained-release(SR) chemotherapy with 5-FU was used or not(NSR). The primary end-point was 5-year overall survival. Kaplan–Meier method with logrank test was used to analyze the overall survival of patients and Cox analysis was used to analyze prognosis factors of these patients.RESULTS In total, there were 563 patients with gastric cancer with locally advanced stage, who underwent an R0 radical resection. 309 patients were included in the final analysis. 219(70.9%) were men, with an average age of 58.25 years. Furthermore, 56(18.1%) received neoadjuvant chemotherapy, and 191(61.8%) were in TNM stage Ⅲ. In addition, 158 patients received intraoperative sustainedrelease chemotherapy with 5-FU and were included in the SR group, while the other 161 patients were included in the NSR group. The overall complication rate was 12.94% in the whole group and 10.81%, 16.46% in SR and NSR groups, respectively. There were no significant differences between the two groups in overall survival and complication rate(P > 0.05). The multivariate cox analysis indicated that only N Stage and neoadjuvant therapy were independent influencing factors of survival.CONCLUSION Intraoperative sustained-release chemotherapy usage with 5-FU, did not improve the survival of patients who underwent an R0 radical resection in locally advanced stage of gastric cancer.

Additively manufactured Ti–Ta–Cu alloys for the next-generation load-bearing implants

Bacterial colonization of orthopedic implants is one of the leading causes of failure and clinical complexities for load-bearing metallic implants. Topical or systemic administration of antibiotics may not offer the most efficient defense against colonization, especially in the case of secondary infection, leading to surgical removal of implants and in some cases even limbs. In this study, laser powder bed fusion was implemented to fabricate Ti3Al2V alloy by a 1:1 weight mixture of CpTi and Ti6Al4V powders. Ti-Tantalum(Ta)–Copper(Cu) alloys were further analyzed by the addition of Ta and Cu into the Ti3Al2V custom alloy. The biological,mechanical, and tribo-biocorrosion properties of Ti3Al2V alloy were evaluated. A 10 wt.% Ta(10Ta) and 3 wt.% Cu(3Cu) were added to the Ti3Al2V alloy to enhance biocompatibility and impart inherent bacterial resistance. Additively manufactured implants were investigated for resistance against Pseudomonas aeruginosa and Staphylococcus aureus strains of bacteria for up to 48 h. A 3 wt.% Cu addition to Ti3Al2V displayed improved antibacterial efficacy, i.e.78%–86% with respect to CpTi. Mechanical properties for Ti3Al2V–10Ta–3Cu alloy were evaluated, demonstrating excellent fatigue resistance, exceptional shear strength, and improved tribological and tribo-biocorrosion characteristics when compared to Ti6Al4V. In vivo studies using a rat distal femur model revealed improved early-stage osseointegration for alloys with10 wt.% Ta addition compared to CpTi and Ti6Al4V. The 3 wt.% Cu-added compositions displayed biocompatibility and no adverse infammatory response in vivo. Our results establish the Ti3Al2V–10Ta–3Cu alloy’s synergistic effect on improving both in vivo biocompatibility and microbial resistance for the next generation of load-bearing metallic implants.

HVOF-sprayed HAp/S53P4 BG composite coatings on an AZ31 alloy for potential applications in temporary implants

Bioactive thermal spray coatings produced via high-velocity oxygen fuel spray(HVOF)from hydroxyapatite(HAp)and bioactive glasses(BG)have the potential to be employed on temporary implants due to the ability of both HAp and BG to dissolve and promote osseointegration,considering that both phases have different reaction and dissolution rates under in-vitro conditions.In the present work,75%wt.HAp-25%wt.S53P4 bioactive glass powders were HVOF-sprayed to obtain HAp/S53P4 BG composite coatings on a bioresorbable AZ31 alloy.The study is focused on exploring the effect of the stand-off distance and fuel/oxygen ratio variation as HVOF parameters to obtain stable structural coatings and to establish their effect on the phases and microstructure produced in those coatings.Different characterization techniques,such as scanning electron microscopy,X-ray diffraction,and Fourier transform infrared spectroscopy,were employed to characterize relevant structural and microstructural properties of the composite coatings.The results showed that thermal gradients during coating deposition must be managed to avoid delamination due to the high temperature achieved(max 550℃)and the differences in coefficients of thermal expansion.It was also found that both spraying distance and oxygen/fuel ratio allowed to keep the hydroxyapatite as the main phase in the coatings.In addition,in-vitro electrochemical studies were performed on the obtained HAp/S53P4 BG composite coatings and compared against the uncoated AZ31 alloy.The results showed a significant decrease in hydrogen evolution(at least 98%)when the bioactive coating was applied on the Mg alloy during evaluation in simulated body fluid(SBF).

Review on the Fabrication of Surface Functional Structures for Enhancing Bioactivity of Titanium and Titanium Alloy Implants

Titanium and its alloys have been widely applied in many biomedical fields because of its excellent mechanical properties,corrosion resistance and good biocompatibility.However,problems such as rejection,shedding and infection will occur after titanium alloy implantation due to the low biological activity of titanium alloy surface.The structures with specific functions,which can enhance osseointegration and antibacterial properties,are fabricated on the surface of titanium implants to improve the biological activity between the titanium implants and human tissues.This paper presents a comprehensive review of recent developments and applications of surface functional structure in titanium and titanium alloy implants.The applications of surface functional structure on different titanium and titanium alloy implants are introduced,and their manufacturing technologies are summarized and compared.Furthermore,the fabrication of various surface functional structures used for titanium and titanium alloy implants is reviewed and analyzed in detail.Finally,the challenges affecting the development of surface functional structures applied in titanium and titanium alloy implants are outlined,and recommendations for future research are presented.

Complicated calcified alloplastic implants in the nasal dorsum:A clinical analysis

BACKGROUND In rhinoplasty,calcification around silicone implants is frequently observed in the tip dorsum(TD)area.Additionally,based on a review of various literature,it is presumed that calcification in silicone implants occurs due to both inflammatory chemical reactions and physical friction against the tissue.The calcification of nasal silicone implants not only results in the functional loss of the implants,but also leads to material deformation.However,there is a lack of research on calcification of nasal silicone implants in the current literature.AIM To elucidate various clinical characteristics of calcification around nasal silicone implants,using histological and radiological analysis.METHODS This study analyzed data from 16 patients of calcified nasal implants,who underwent revision rhinoplasty for various reasons after undergoing augmentation rhinoplasty with silicone implants.The collected data included information on implant duration,implant types,location of calcification,presence of inflammatory reactions,and computed tomography(CT)scans.RESULTS The most common location of calcification,as visually analyzed,was in the TD area,accounting for 56%.Additionally,the analysis of CT scans revealed a trend of increasing Hounsfield Unit values for calcification with the duration of implantation,although this trend was not statistically significant(P=0.139).CONCLUSION Our study shows that reducing the frequency of calcification may be achievable by using softer silicone implants and by minimizing the damage to perioperative tissues.

Digital manufacturing of personalized magnesium implants through binder jet additive manufacturing and automated post machining

While magnesium(Mg)is a promising material for personalized temporary implants,the lack of a digital manufacturing solution for Mg implants impedes its potential progress.This study introduces a hybrid manufacturing process that integrates binder jet additive manufacturing with automated dry post-machining to enable end-to-end digital manufacturing of personalized Mg implants.Spherical cap-shaped Mg implants were additively manufactured through binder jetting.These implants were placed on graphite flakes during sintering as a potential non-reactive support material,allowing unrestricted shrinkage of 15.2%to a relative density of 87%.Microstructural and dimensional analysis revealed consistent interconnected porous microstructures with a shrinkage distortion within±0.2 mm of the original digital drawing.High-speed dry milling of the sintered samples,assessed via an orthogonal cutting test,identified the optimized cutting parameters.A three-step machining process for automated 5-axis machining,along with clamping strategies,referencing,and an adaptive plug-in,were successfully implemented.The automated dry machining on binder-jet printed Mg implants resulted in an average roughness of<1.3μm with no defects.In summary,this work introduces a robust digital manufacturing solution to advance the transformative landscape of Mg implants and scaffolds.©2024 Chongqing University.Publishing services provided by Elsevier B.V.on behalf of KeAi Communications Co.Ltd.

Investigation of bioactivity and biodegradability of Mg-bioceramic implants:An in vitro study for biomedical applications

In this study,Mg-based composites,by the addition of ZnO,Ca_(2)ZnSi_(2)O_(7),Ca_(2)MgSi_(2)O_(7),and CaSiO_(3)as bioactive agents,were fabricated using friction stir processing.The microstructure and in vitro assessment of bioactivity,biodegradation rate,and corrosion behavior of the resultant composites were investigated in simulated body fluid(SBF).The results showed that during the immersion of composites in SBF for 28 d,due to the release of Ca^(2+)and PO_(4)^(3-)ions,hydroxyapatite(HA)crystals with cauliflower shaped morphology were deposited on the surface of composites,confirming good bioactivity of composites.In addition,due to the uniform distribution of bioceramic powders throughout Mg matrix,grain refinement of the Mg matrix,and uniform redistribution of secondary phase particles,the polarization resistance increased,and the biodegradation rate of composites significantly reduced compared to monolithic Mg matrix.The polarization corrosion resistance of Mg-ZnO increased from 0.216 to 2.499 kΩ/cm^(2)compared to monolithic Mg alloy.Additionally,Mg-ZnO composite with the weight loss of 0.0217 g after 28 d immersion showed lower weight loss compared to other samples with increasing immersion time.Moreover,Mg-ZnO composite with the biodegradation rate of 37.71 mm/a exhibited lower biodegradation rate compared to other samples with increasing immersion time.

Elimination of methicillin‑resistant Staphylococcus aureus biofilms on titanium implants via photothermally‑triggered nitric oxide and immunotherapy for enhanced osseointegration

Background:Treatment of methicillin-resistant Staphylococcus aureus(MRSA)biofilm infections in implant placement surgery is limited by the lack of antimicrobial activity of titanium(Ti)implants.There is a need to explore more effective approaches for the treatment of MRSA biofilm infections.Methods:Herein,an interfacial functionalization strategy is proposed by the integration of mesoporous polydopamine nanoparticles(PDA),nitric oxide(NO)release donor sodium nitroprusside(SNP)and osteogenic growth peptide(OGP)onto Ti implants,denoted as Ti-PDA@SNP-OGP.The physical and chemical properties of Ti-PDA@SNP-OGP were assessed by scanning electron microscopy,X-ray photoelectron spectroscope,water contact angle,photothermal property and NO release behavior.The synergistic antibacterial effect and elimination of the MRSA biofilms were evaluated by 2′,7′-dichlorofluorescein diacetate probe,1-N-phenylnaphthylamine assay,adenosine triphosphate intensity,O-nitrophenyl-β-D-galactopyranoside hydrolysis activity,bicinchoninic acid leakage.Fluorescence staining,assays for alkaline phosphatase activity,collagen secretion and extracellular matrix mineralization,quantitative real‑time reverse transcription‑polymerase chain reaction,and enzyme-linked immunosorbent assay(ELISA)were used to evaluate the inflammatory response and osteogenic ability in bone marrow stromal cells(MSCs),RAW264.7 cells and their co-culture system.Giemsa staining,ELISA,micro-CT,hematoxylin and eosin,Masson's trichrome and immunohistochemistry staining were used to evaluate the eradication of MRSA biofilms,inhibition of inflammatory response,and promotion of osseointegration of Ti-PDA@SNP-OGP in vivo.Results:Ti-PDA@SNP-OGP displayed a synergistic photothermal and NO-dependent antibacterial effect against MRSA following near-infrared light(NIR)irradiation,and effectively eliminated the formed MRSA biofilms by inducing reactive oxygen species(ROS)-mediated oxidative stress,destroying bacterial membrane integrity and causing leakage of intracellular components(P<0.01).In vitro experiments revealed that Ti-PDA@SNP-OGP not only facilitated osteogenic differentiation of MSCs,but also promoted the polarization of pro-inflammatory M1 macrophages to the anti-inflammatory M2-phenotype(P<0.05 or P<0.01).The favorable osteo-immune microenvironment further facilitated osteogenesis of MSCs and the anti-inflammation of RAW264.7 cells via multiple paracrine signaling pathways(P<0.01).In vivo evaluation confirmed the aforementioned results and revealed that Ti-PDA@SNP-OGP induced ameliorative osseointegration in an MRSA-infected femoral defect implantation model(P<0.01).Conclusions:Ti-PDA@SNP-OGP is a promising multi-functional material for the high-efficient treatment of MRSA infections in implant replacement surgeries.

In vivo and in vitro study of resorbable magnesium wires for medical implants:Mg purity,surface quality,Zn alloying and polymer coating

Magnesium is an excellent material in terms of biocompatibility and its corrosion products can serve as an active source for new bone formation.However,localized corrosion and H_(2)generation limit the potential of Mg-based implants.Utilizing low-alloyed Mg-Zn wires can strongly reduce problems with large H_(2)bubbles and improve the mechanical properties considerably while maintaining excellent long-term biocompatibility.Acidic pickling and a polymer coating can be effectively used to lower the rate of in vivo degradation.In this work,microstructural,mechanical,and in vitro characterization of 250μm and 300μm extruded wires made from ultra-pure Mg,commercially pure Mg,Mg-0.15Zn,Mg-0.4Zn and Mg-1Zn was performed.Additionally,Mg-0.4Zn wires together with a variant coated with a copolymer of L-lactide andε-caprolactone were tested in vivo on artificially damaged Wistar rat femurs.Based on the observed Mg-induced osteogenesis,polymer-coated Mg wires with a small addition of Zn are a perspective material for bone-support applications,such as cerclage and fixation wires.

Pharmacokinetics of nifedipine sustained-release tablets in healthy Chinese volunteers

Aim To establish a LC-MS method for determining the concentration of nifedipine in human plasma and to evaluate the pharmacokinetic characteristics of nifedipine sustained-release tablets. Methods A XB-C18 （5 μm, 4.6 mm ×150 mm） column and a mobile phase of methanol： 0.01 mol·L^-1ammonium acetate （60：40, V/V） were used to separate nifedipine, the detections was accuracy under atmosperic pressure electronic spray ionization （AP-ESI） mode and ion mass spectrum （m/z） of 314.9 [M＋H]^＋ for nifedipine, and 320.8 [M＋H]^＋ for lorazepam （Internal Standard, IS）. Results The linear range of nifedipine was 0.3 - 80 ng·mL^-1 （ r = 0.9997）, and the limit of quantitation （LOQ） was 0.3 ng·mL^-1. The nifedipine pharmacokinetic parameters after a single dose of 20 mg nifedipine sustained-release tablets test （T） or reference （R） were as the followings, t1/2 （6.73 ± 2.00） h and （7.04 ± 2.18） h, Tmax （4.28 ± 0.70） h and （4.48 ± 0.70） h, Cmax（39.66 ± 10.58） ng·mL^-1 and （40.19 ± 10.97） ng·mL^-1, AUC0-36 （391.63 ± 108.55） ng·mL^-1·h and （387.57 ± 121.51） ng·mL^-1·h, and AUC0-∞ （408.28 ± 121.16） ng·mL^-1·h and （406.15 ± 133.13） ng·mL^-1·h. The relative bioavailability of nifedipine sustained-release tablets （test） was （103.02 ± 13.93） %. Conclusion LC-MS method for the determination of concentrations of nifedipine in human plasma was sensitive and accurate, and could be used in nifedipine bioavailability and pharmacokinetic studies.

Finite element analysis of stress at implant-bone interface of dental implants with different structures

The effect of structure,elastic modulus and thickness of lower modulus layer in porous titanium implants on the stress distribution at the implant-bone interface was investigated.Three-dimensional finite element models of different titanium implants were constructed.The structures of the implants included the whole lower modulus style （No.1）,bio-mimetic style （No.2）,the whole lower modulus style in cancellous bone （No.3） and the whole dense style No.4.The stress distributions at bone-implant interface under static loading were analyzed using Ansys Workbench 10.0 software.The results indicated that the distribution of interface stress is strongly depended on the structure of the implants.The maximum stresses in cancellous bone and root region of implant No.2 are lower than those in the other three implants.A decrease in the modulus of the low modulus layer facilitates the interface stress transferring.Increasing the thickness of the low modulus layer can reduce the stress and induce a more uniform stress distribution at the interface.Among the four implants,biomimetic style implant No.2 is superior in transferring implant-bone interface stress to surrounding bones.

Preparation of Sustained-release Silybin Microspheres by Spherical Crystallization Technique

Aim To improve the dissolution rate and bioavailability of silybin. Methods Sustained-release silybin microspheres were prepared by the spherical crystallization technique with soliddispersing and release-retarding polymers. A differential scanning calorimeter and an X-ray diffractometer were used to investigate the dispersion state of silybin in the microspheres. The shape, surface morphology, and internal structure of the microspheres were observed using a scanning electron microscope. Characterization of the microspheres, such as average diameter, size distribution and bulk density of the microspheres was investigated. Results The particle size of the microspheres was determined mainly by the agitation speed. The dissolution rate of silybin from microspheres was enhanced by increasing the amount of the dispersing agents, and sustained by the retarding agents. The release rate of microspheres was controlled by adjusting the combination ratio of the dispersing agents to the retarding agents. The resuits of X-ray diffraction and differential scanning calorimetry analysis indicated that silybin was highly dispersed in the microspheres in amorphous state. The release profiles and content did not change after a three-month accelerated stability test at 40 ℃ and 75% relative humidity. Conclusion Sustained-release silybin microspheres with a solid dispersion structure were prepared successfully in one step by a spherical crystallization technique combined with solid dispersion technique. The preparation process is simple, reproducible and inexpensive. The method is efficient for designing sustained-release microspheres with water-insoluble drugs.

Pharmacokinetics and Relative Bioavailability ofsustained-release Tablets of Diclofenac Sodiumin Male Volunteers

The pharmacokinetics of a sustained- release formulation and an enteric- coated tablet of diclofenac sodium were studied on 8 healthy male volunteers in an open,randomized crossover study.Drug level in serum was assayed by HPLC method.The changes in serum concentration were conformed to a l-compartment open model.The t_1/2 (Ke)averaged 2.15±0.17 and ll.60 ± l.95 h,and the areas under the drug concentration curves were 5.87 ± 0.67 and 5.55 ± 0.57μgh/ml for enteric-coated and sustained-release tablet of diclofenac sodium,respectively. The mean relative bioavailability of sustained-release tablet was 0.95 to that of enteric-coated tablet.

Impact of osteoporosis in dental implants:A systematic review

AIM: To assess the failure and bone-to-implant contact rate of dental implants placed on osteoporotic subjects. METHODS: Extensive examination strategies were created to classify studies for this systematic review. MEDLINE(via Pub Med) and EMBASE database were examined for studies in English up to and including May 2014. The examination presented a combination of the MeS H words described as follow: "osteoporosis" or "osteopenia" or "estrogen deficiency" AND "implant" or "dental implant" or "osseointegration". Assessment of clinical and/or histological peri-implant conditions in osteoporosis subjects treated with titanium dental implants. The examination included a combination of the MeS H terms described as follow: "osteoporosis" or "osteopenia" or "estrogen deficiency" AND "implant" or "dental implant" or "osseointegration".RESULTS: Of 943 potentially eligible articles, 12 were included in the study. A total of 133 subjects with osteoporosis, 73 subjects diagnosed with osteopenia and 708 healthy subjects were assessed in this systematic review. In these subjects were installed 367, 205, 2981 dental implants in osteoporotic, osteopenic and healthy subjects, respectively. The failure rate of dental implant was 10.9% in osteoporotic subjects, 8.29% in osteopenic and 11.43% in healthy ones. Bone-to-implant contact obtained from retrieved implants ranged between 49.96% to 47.84%, for osteoporosis and non-osteoporotic subjects. CONCLUSION: Osteoporotic subjects presented higher rates of implant loss, however, there is a lower evidence to strengthen or refute the hypothesis that osteoporosis may have detrimental effects on bone healing. Consequently, final conclusions regarding the effect of osteoporosis in dental implant therapy cannot be made at this time. There are no randomized clinical trial accessible for evaluation and the retrospectivenature of the evaluated studies shall be taken in account when interpreting this study.

Experiment research of cisplatin implants inhibiting transplantation tumor growth and regulating the expression of KLK7 and E-cad of tumor-bearing mice with gastric cancer

Objective: To study the influence of cisplatin implants on transplantation tumor growth and the expression of tissue kallikrein-7(KLK7) and E-cadherin(E-cad) in tumor-bearing mice with gastric cancer. Methods: BALB/c nude mice were collected as experimental animal and were randomly divided into model control group(Group A), tail intravenous injection of cisplatin group(Group B), intratumor injection of cisplatin group(Group C) and cisplatin implants treatment group(Group D). After the drugs intervening, the weight and volume of transplantation tumors were measured on Day 20, Day 30 and Day 40 and serum and KLK7 and E-cad contents in transplanted tumor tissue were examined. Results: On Day 20, Day 30 and Day 40 after treatment, the weight and volume of transplantation tumors of tumorbearing mice in four groups were different(Group A > Group B > Group C > Group D). The contents of KLK-7 and E-cad in tumor tissue and serum of tumor-bearing mice in four groups were different(Group A > Group B > Group C > Group D in KLK-7) and(Group A < Group B < Group C < Group D in E-cad). The weight and volume, and KLK7 and E-cad contents of transplantation tumors in four groups were significant difference(P<0.05). Conclusion: Cisplatin implants can inhibit the growth of transplanted tumor tissue and down-regulated KLK7 expression and up-regulated E-cad expression of tumor-bearing mice with gastric

Total hip replacement:A meta-analysis to evaluate survival of cemented,cementless and hybrid implants

AIM To determine whether cemented, cementless, or hybrid implant was superior to the other in terms of survival rate.METHODS Systematic searches across MEDLINE, CINAHL, and Cochrane that compared cemented, cementless and hybrid total hip replacement(THR) were performed. Two independent reviewers evaluated the risk ratios of revision due to any cause, aseptic loosening, infection, and dislocation rate of each implants with a pre-determined form. The risk ratios were pooled separately for clinical trials, cohorts and registers before pooled altogether using fixed-effect model. Meta-regressions were performed to identify the source of heterogeneity. Funnel plots were analyzed. RESULTS Twenty-seven studies comprising 5 clinical trials, 9 cohorts, and 13 registers fulfilled the research criteria and analyzed. Compared to cementless THR, cemented THR have pooled RR of 0.47(95%CI: 0.45-0.48), 0.9(0.84-0.95), 1.29(1.06-1.57) and 0.69(0.6-0.79) for revision due to any reason, revision due to aseptic loosening, revision due to infection, and dislocation respectively. Compared to hybrid THR, the pooled RRs of cemented THR were 0.82(0.76-0.89), 2.65(1.14-6.17), 0.98(0.7-1.38), and 0.67(0.57-0.79) respectively. Compared to hybrid THR, cementless THR had RRs of 0.7(0.65-0.75), 0.85(0.49-1.5), 1.47(0.93-2.34) and 1.13(0.98-1.3).CONCLUSION Despite the limitations in this study, there was some tendency that cemented fixation was still superior than other types of fixation in terms of implant survival.

After cochlear implantation: Complications related to flap around implants

Objective: To report complications related to flap around implants after cochlear implantation, possible causes of such complications and treatments. Methods and material:We performed a retrospective analysis of children in whom complications related to flap around implants occurred after undergoing cochlear implantation in our department from 2005 to 2016. Results:Complications among 1500 cochlear implantation (CI) recipients by the same surgeon included hematoma (n ? 20) and seroma around implants (n ? 15), of which most (n ? 10) recovered in 2 weeks after effective drainage, utility of antibiotics and pressure dressing, but 5 developed flap necrosis and had to undergo contralateral re-implantation. Four patients developed abscess around implants, of whom 2 recovered after 2 weeks of drainage, gentamicin irrigation and use of antibiotics, but 2 patients ended up with flap necrosis and had to receive contralateral reimplantation. Conclusions: Immediate drainage, pressure dressing and antibiotics can be used to effectively control seroma around implants. For seroma lasting for more than two weeks without improvement, surgical drainage may be need.

Additive manufacturing technologies of porous metal implants

Biomedical metal materials with good corrosion resistance and mechanical properties are widely used in orthopedic surgery and dental implant materials,but they can easily cause stress shielding due to the significant difference in elastic modulus between the implant and human bones.The elastic modulus of porous metals is lower than that of dense metals.Therefore,it is possible to adjust the pore parameters to make the elastic modulus of porous metals match or be comparable with that of the bone tissue.At the same time,the open porous metals with pores connected to each other could provide the structural condition for bone ingrowth,which is helpful in strengthening the biological combination of bone tissue with the implants.Therefore,the preparation technologies of porous metal implants and related research have been drawing more and more attention due to the excellent features of porous metals.Selective laser melting(SLM)and electron beam melting technology(EBM)are important research fields of additive manufacturing.They have the advantages of directly forming arbitrarily complex shaped metal parts which are suitable for the preparation of porous metal implants with complex shape and fine structure.As new manufacturing technologies,the applications of SLM and EBM for porous metal implants have just begun.This paper aims to understand the technology status of SLM and EBM,the research progress of porous metal implants preparation by using SLM and EBM,and the biological compatibility of the materials,individual design and manufacturing requirements.The existing problems and future research directions for porous metal implants prepared by SLM and EBM methods are discussed in the last paragraph.

Sensory innervation around immediately vs. delayed loaded implants: a pilot study

Although neurophysiological and psychophysical proof of osseoperception is accumulating, histomorphometric evidence for the neural mechanisms of functional compensation following immediate and delayed implant loading is still lacking. For this randomized split-mouth study, six mongrel dogs randomly received one of four treatment protocols at 36 implant-recipient sites over 16 weeks （third maxillary incisor, third and fourth mandibular premolar）： immediate implant placement and immediate loading （liP＋ IL）; delayed implant placement and delayed loading （DIP＋DL）; delayed implant placement and immediate loading （DIP＋IL）; and natural extraction socket healing （control）. Histomorphometry was performed in the peri-implant bone and soft tissues within 300 pm around the implants. Immunocytochemistry and transmission electron microscopy were used to confirm the presence of neural structures and to reveal their ultrastructural characteristics, respectively. Myelinated nerve fibres densely populated the peri-implant crestal gingival and apical regions, although they were also identified in the woven bone and in the osteons near the implant threads. Compared with the control group in the mandible, the group that received IIP＋IL showed a higher innervation （in N.mm^-2, 5.94±1.12 vs. 3.15±0.63, P〈0.001） and smaller fibre diameter （in pm, 1.37±0.05 vs. 1.64±0.13, P=0.016）, smaller axon diameter （in pm, 0.89±0.05 vs. 1.24±0,10, P=0.009） and g-ratio （0.64±0.04 vs. 0.76±0.05, P〈0.001） in the middle region around the implants. Compared with DIP＋IL in the mandible, IIP＋IL had a higher nerve density （in N.mm^-2, 13.23±2.54 vs. 9.64±1.86, P=0.027）, greater fibre diameter （in pm, 1.32±0.02 vs. 1.20±0.04, P=0.021）, greater axon diameter （in μm, 0.92±0.01 vs. 0.89±0.03, P=-0.035） and lower g-ratio （0.69±0.01 vs. 0.74±0.01, P=-0.033） in the apical region around the implants. It may be assumed that the treatment protocol with liP＋ IL is the preferred method to allow optimized peri-implant re-innervation, but further functional measurements are still required.

Applied Anatomic Site Study of Palatal Anchorage Implants Using Cone Beam Computed Tomography

Aim The purpose of this study was to conduct quantitative research on bone height and bone mineral density of palatal implant sites for implantation, and to provide reference sites for safe and stable palatal implants. Methodology Three-dimensional reformatting images were reconstructed by cone beam computed tomography （CBCT） in 34 patients, aged 18 to 35 years, using EZ Implant software. Bone height was measured at 20 sites of interest on the palate. Bone mineral density was measured at the 10 sites with the highest implantation rate, classified using K-mean cluster analysis based on bone height and bone mineral density. Results According to the cluster analysis, 10 sites were classified into three clusters. Significant differences in bone height and bone mineral density were detected between these three clusters （P〈0.05）. The greatest bone height was obtained in cluster 2, followed by cluster 1 and cluster 3. The highest bone mineral density was found in cluster 3, followed by cluster 1 and cluster 2. Conclusion CBCT plays an important role in pre-surgical treatment planning. CBCT is helpful in identifying safe and stable implantation sites for palatal anchorage.