Bioactivity of PEEK GRF30 and Ti6Al4V SLM in Simulated Body Fluid and Hank’s Balanced Salt Solution

In recent years, scientists have defined two main paths for orthopedic implant fabrication: searching for new materials with properties closest to natural bone in order to reduce the stress-shielding effect or creating individually adapted geometry of the implant with the use and Rapid Prototyping methods. Therefore, materials such as PEEK GRF30 and Ti6Al4V selective laser melting (SLM) are of interest. They are defined as materials suitable for implants, however, the knowledge of their bioactivity, a feature which is one of the most desirable properties of biomaterials, is still insufficient. Using Simulated Body Fluid and Hank’s Balanced Salt Solution, the bioactivity of PEEK GRF30 and Ti6Al4V SLM was assessed, as well as commercial Ti6Al4V as a reference material. Ten cylindrical samples of each material were prepared and immersed in solutions per period from 2 to 28 days at 37 °C. Optical analysis of the changes on the examined surfaces suggested that right after 2-day crystals with different morphologies were formed on each material. Further analysis of the chemical composition of the altered surfaces confirmed the formation of a calcium phosphate layer on them, however, the Ca/P ratio was slightly different from 1.67. On the basis of the obtained results, it can be concluded that both PEEK GRF30 and Ti6Al4V SLM are characterized by appropriate—comparable to Ti6Al4V—bioactivity.     

Preclinical evaluation of injectable bone substitute materials

Injectable bone substitutes (IBSs) represent an attractive class of ready‐to‐use biomaterials, both ceramic‐ and polymer‐based, as they offer the potential benefit of minimally invasive surgery and optimal defect filling. Although in vitro assessments are the first step in the process of development, the safety and efficacy of an IBS strongly depend on validated preclinical research prior to clinical trials. However, the selection of a suitable preclinical model for performance evaluation of an IBS remains a challenge, as no gold standard exists to define the best animal model. In order to succeed in this attempt, we identified three stages of development, including (a) proof‐of‐principle, (b) predictive validity and (c) general scientific legitimacy, and the respective criteria that should be applied for such selection. The second part of this review provides an overview of commonly used animals for IBSs. Specifically, scientific papers published between January 1996 and March 2012 were retrieved that report the use of preclinical models for the evaluation of IBSs in situations requiring bone healing and bone augmentation. This review is meant not only to describe the currently available preclinical models for IBS application, but also to address critical considerations of such multi‐factorial evaluation models (including animal species, strain, age, anatomical site, defect size and type of bone), which can be indicative but in most cases edge away from the human reality. Consequently, the ultimate goal is to guide researchers toward a more careful and meaningful interpretation of the results of experiments using animal models and their clinical applications. Copyright © 2012 John Wiley & Sons, Ltd.     

海洋生物医用材料的临床应用和安全性评价

目的： 对海洋生物医用材料在医疗领域的应用情况和海洋生物材料来源医疗器械的安全性评价趋势进行分析，为推进该材料的临床转化提供参考。方法： 归纳海洋生物医用材料的分类和应用，介绍该材料的安全性评价的程序要点，探讨其安全性评价中面临的挑战。结果与结论： 常用的海洋生物医用材料主要为多糖和蛋白质，在创伤修复和组织工程领域应用广泛。海洋生物医用材料具有生物活性和良好的生物相容性，对此类材料的安全性评价应根据材料特性和预期用途，科学制定评价程序和选择检验方法。     

Addition of platelet‐rich plasma supports immune modulation and improved mechanical integrity in Alloderm mesh for ventral hernia repair in a rat model

The recurrence of ventral hernias continues to be a problem faced by surgeons, in spite of efforts toward implementing novel repair techniques and utilizing different materials to promote healing. Cadaveric acellular dermal matrices (Alloderm) have shown some promise in numerous surgical subspecialties, but these meshes still suffer from subsequent failure and necessitation of re‐intervention. Here, it is demonstrated that the addition of platelet rich plasma to Alloderm meshes temporally modulates both the innate and cytotoxic inflammatory responses to the implanted material. This results in decreased inflammatory cytokine production at early time points, decreased matrix metalloproteinase expression, and decreased CD8+ T cell infiltration. Collectively, these immune effects result in a healing phenotype that is free from mesh thinning and characterized by increased material stiffness.     

From the Cover: A simple nutrient-dependence mechanism for predicting the stoichiometry of marine ecosystems

It is widely recognized that the stoichiometry of nutrient elements in phytoplankton varies within the ocean. However, there are many conflicting mechanistic explanations for this variability, and it is often ignored in global biogeochemical models and carbon cycle simulations. Here we show that globally distributed particulate P:C varies as a linear function of ambient phosphate concentrations, whereas the N:C varies with ambient nitrate concentrations, but only when nitrate is most scarce. This observation is consistent with the adjustment of the phytoplankton community to local nutrient availability, with greater flexibility of phytoplankton P:C because P is a less abundant cellular component than N. This simple relationship is shown to predict the large-scale, long-term average composition of surface particles throughout large parts of the ocean remarkably well. The relationship implies that most of the observed variation in N:P actually arises from a greater plasticity in the cellular P:C content, relative to N:C, such that as overall macronutrient concentrations decrease, N:P rises. Although other mechanisms are certainly also relevant, this simple relationship can be applied as a first-order basis for predicting organic matter stoichiometry in large-scale biogeochemical models, as illustrated using a simple box model. The results show that including variable P:C makes atmospheric CO₂ more sensitive to changes in low latitude export and ocean circulation than a fixed-stoichiometry model. In addition, variable P:C weakens the relationship between preformed phosphate and atmospheric CO₂ while implying a more important role for the nitrogen cycle.Nutrient elements are used by phytoplankton to synthesize molecules, in order to accomplish biochemical functions. Some of these molecules are absolutely necessary, and the nutrient elements have no substitutes. Examples are P in nucleic acids, N in amino acids, and Fe in the photosynthetic apparatus (1). However, there is a degree of plasticity in the molecular assemblage required per phytoplankton cell, which varies between species and between clades (2, 3). Furthermore, there is a capacity for plasticity in molecular composition of even a given species, as shown in culture experiments (4, 5). Such plasticity leads to variability in the elemental ratios of nutrients in marine phytoplankton, widely documented in laboratory and field measurements (2, 6, 7). Recent analyses of global nutrient and particulate observations have shown that N:P, the most commonly discussed ratio, varies regionally, including low N:P in the high-latitude Southern Ocean and high N:P in the oligotrophic regions (7–9). Explanations of high N:P in oligotrophic waters have often invoked an enhanced reliance on N-rich proteins for gathering scarce resources (1, 10), whereas low N:P in the Southern Ocean has been variously attributed to the abundance of P-rich molecules in cold, fast-growing plankton (11), or to the availability of Si, which supports P-rich diatom communities (8, 12).Despite an abundant literature on stoichiometric variability and its potential causes, no simple predictive relationship has been widely adopted in global biogeochemical models. Instead, the vast majority of global biogeochemical models assumes fixed C:N:P in organic matter, including most participants in the recent Coupled Model Intercomparison Project, CMIP5 (13). Thus, the potential impact of changes in organic matter stoichiometry on ocean carbon storage and oxygen consumption remain largely unexplored. The neglect of stoichiometric variability is due, at least in part, to the lack of a clear predictive framework.Here, it is argued that the concentration of a nutrient element in seawater can provide a suitable predictive framework, because it is a critical determinant of the rate at which that element will tend to be taken up by the organisms in the local community. This hypothesis builds on classic resource competition theory (14), which argues that if the concentration of an element is low, such that uptake is difficult, the community will be dominated by organisms that are well adapted to a low cellular quota of that nutrient (10). If, on the other hand, the concentration is high, facilitating high uptake rates, the community will be dominated by organisms that are capable of taking advantage of that nutrient to grow faster. This suggestion leads to clear predictions with significant biogeochemical consequences, as outlined below.     

Titanium allergy: could it affect dental implant integration?

Purpose: Degradation products of metallic biomaterials including titanium may result in metal hypersensitivity reaction. Hypersensitivity to biomaterials is often described in terms of vague pain, skin rashes, fatigue and malaise and in some cases implant loss. Recently, titanium hypersensitivity has been suggested as one of the factors responsible for implant failure. Although titanium hypersensitivity is a growing concern, epidemiological data on incidence of titanium‐related allergic reactions are still lacking. Materials and methods: A computer search of electronic databases primarily MEDLINE and PUBMED was performed with the following key words: ‘titanium hypersensitivity’, ‘titanium allergy’, ‘titanium release’ without any language restriction. Manual searches of the bibliographies of all the retrieved articles were also performed. In addition, a complementary hand search was also conducted to identify recent articles and case reports. Results: Most of the literature comprised case reports and prospective in vivo/in vitro trials. One hundred and twenty‐seven publications were selected for full text reading. The bulk of the literature originated from the orthopaedic discipline, reporting wear debris following knee/hip arthroplasties. The rest comprised osteosynthesis (plates/screws), oral implant/dental materials, dermatology/cardiac‐pacemaker, pathology/cancer, biomaterials and general reports. Conclusion: This review of the literature indicates that titanium can induce hypersensitivity in susceptible patients and could play a critical role in implant failure. Furthermore, this review supports the need for long‐term clinical and radiographic follow‐up of all implant patients who are sensitive to metals. At present, we know little about titanium hypersensitivity, but it cannot be excluded as a reason for implant failure. To cite this article:
Siddiqi A, Payne AGT, De Silva RK, Duncan WJ. Titanium allergy: could it affect dental implant integration?
Clin. Oral Impl. Res. 22 , 2011; 673–680
doi: 10.1111/j.1600‐0501.2010.02081.x     

Bioengineered tissues: the science, the technology, and the industry

Authors – Ahsan T, Nerem RM Objective – The bioengineering of tissues and organs, sometimes called tissue engineering and at other times regenerative medicine, is emerging as a science, as a technology, and as an industry. The goal is the repair, replacement, and/or the regeneration of tissues and organs. The objective of this paper is to identify and discuss the major issues that have become apparent. Results – One of the critical issues is that of cell source, i.e. what will be the source of the cells to be employed? Another critical issue is the development of approaches for the fabrication of substitute tissues/organs and/or vehicles for the delivery of biological active molecules for use in the repair/regeneration of tissues. A third critical issue, one very much related to cell source, is that of immune acceptance. In addition, there are technological hurdles; there are additional issues such as the scale‐up of manufacturing processes and the preservation of living‐cell products for off‐the‐shelf availability. Although the initial products have been superficially applied skin substitutes, as this fledgling industry continues to evolve, it is beginning to focus on a wider range of more invasive and complicated products. From a public health perspective, the real opportunity may be in addressing chronic diseases, as well as the transplantation crisis (i.e. the tremendous disparity between patient need for vital organs and donor availability) and, equally important is the challenge of neural repair. Conclusion – These are the grand challenges, and the scientific community, business/private sector, and federal government must mobilize itself together in this emerging area to translate the benchtop science to the patient bedside.     

One-year outcome of narrow diameter blasted implants for rehabilitation of maxillas with knife-edge resorption

Objectives: This study aimed at assessing the clinical outcome of narrow diameter implants in the treatment of knife‐edge edentulous maxillas of adequate bone height but inadequate width (class IV of Cawood and Howell). Material and methods: Twelve consecutive patients (eight women and four men, mean age 58 years) with class IV atrophic edentulous maxillas were included in the study. Seventy‐three microthreaded TiO₂‐blasted implants were placed and the resonance frequency measured. All the implants had a diameter of 3.5 mm. After 6 months of submerged healing, fixed implant‐supported prostheses were delivered to the patients and resonance frequency and radiographic examinations performed. After the first year of loading, the implant outcome was again evaluated clinically, radiographically and with resonance frequency analysis. Results: All the implants were followed up to 1 year of loading and their survival rate was 100%. Bone loss after 1 year of loading was (mean±SD) 0.30±0.13 mm. Stability values were (mean±SD) 63±5.8 ISQ at placement, 60±4.7 ISQ at the abutment connection and 61±5 ISQ after 1 year of loading. A significant difference resulted between placement and abutment connection values (P=0.03). Conclusions: According to the present study, narrow implants may be used to restore edentulous maxillas with atrophies of class IV of Cawood and Howell. When planning the treatment of edentulous maxillas with such a resorption pattern, this possibility has to be considered as an alternative to more demanding grafting techniques.     

甲壳素/壳聚糖在疝修补领域的研究综述

疝气是目前临床上1 种常见的外科疾病,随着疝气患者的日益增多,疝修补材料的不断革新成为临床疝气领域的研发热点,力求通过改善疝修补材料来促进疝修补术后的腹壁组织修复情况。目前海洋来源的甲壳素/壳聚糖是生物医用材料领域研究的热点材料,具有广阔的发展前景。综述疝修补材料和以甲壳素和壳聚糖为代表的海洋生物材料的生物学特性及其在疝修补领域的研究进展,评价其作为疝修补材料的可行性,为海洋生物材料在疝修补领域的广泛应用提供新思路。