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The aim was to investigate the effect of cryopreservation on the enamel bonding properties of orthodontic brackets. Sixty-six human premolars were randomly allocated to a control group or a cryopreserved group. Conventional stainless-steel orthodontic brackets were bonded with a light cure adhesive on the buccal side of the premolars. The shear bond strength (SBS) was determined at a crosshead speed of 1 mm/min. The SBS and adhesive remnant index (ARI) were evaluated respectively by an independent samples t test and Fisher's exact test (α≤0.05). The mean failure load was lower in the cryopreserved group. However, this difference in SBS was not significant (p=0.443). In both groups, the ARI mostly indicated a failure at the enamel-adhesive interface. The mean ARI scores for both groups were not significantly different (p=0.099). Within the limitations of this macro bond strength testing, it can be concluded that cryopreservation does not significantly affect the bonding properties of enamel.

Multicellular spheroids are important tools for studying tissue and cancer physiology in 3D and are frequently used in tissue engineering as tissue assembling units for biofabrication. While the main power of the spheroid model is in mimicking physical-chemical gradients at the tissue microscale, the real physiological environment (including dynamics of metabolic activity, oxygenation, cell death, and proliferation) inside the spheroids is generally ignored. At the same time, the effects of the growth medium composition and the formation method on the resulting spheroid phenotype are well documented. Thus, characterization and standardization of spheroid phenotype are required to ensure the reproducibility and transparency of the research results. The analysis of average spheroid oxygenation and the value of O2 gradients in three dimensions (3D) can be a simple and universal way for spheroid phenotype characterization, pointing at their metabolic activity, overall viability, and potential to recapitulate in vivo tissue microenvironment. The visualization of 3D oxygenation can be easily combined with multiparametric analysis of additional physiological parameters (such as cell death, proliferation, and cell composition) and applied for continuous oxygenation monitoring and/or end-point measurements. The loading of the O2 probe is performed during the stage of spheroid formation and is compatible with various protocols of spheroid generation. The protocol includes a high-throughput method of spheroid generation with introduced red and near-infrared emitting ratiometric fluorescent O2 nanosensors and the description of multi-parameter assessment of spheroid oxygenation and cell death before and after bioprinting. The experimental examples show comparative O2 gradients analysis in homo- and hetero-cellular spheroids as well as spheroid-based bioprinted constructs. The protocol is compatible with a conventional fluorescence microscope having multiple fluorescence filters and a light-emitting diode as a light source.

Purpose The importance of the surrounding ovarian stromal cells and extracellular matrix in the development and maturation of follicles has recently gained attention. An aberrant extracellular matrix has been described in ovaries of patients with polycystic ovary syndrome where a more rigid structural environment, possibly induced by endogenous testosterone, impairs normal folliculogenesis. In this context, we describe the textural parameters of the ovarian cortex of transgender men after prolonged testosterone administration compared to the textural parameters of the non-exposed ovarian cortex originating from female oncological patients. Methods Texture profile analysis (TPA) was performed on ovarian cortex (5 × 5 mm) of oncological and transgender patients in order to measure stiffness, hardness, cohesiveness, and springiness of the ovarian cortex (LRXplus universal testing system). Statistical analysis was performed using repeated measurements mixed models and the Spearman rank order correlation test (IBM SPSS Statistics 23). Results A total of 36 frozen-thawed cortical strips (5 × 5 mm) were subjected to TPA. The superficial part of cortex fragments originating from transgender persons (fragments < 1.4 mm; N = 10) appeared to be significantly stiffer compared to cortex derived from oncology patients (fragments < 1.4 mm; N = 7) (6.78 ± 1.38 N/mm versus 5.41 ± 0.9 N/mm respectively, p = 0.036). Conclusions This is the first application of TPA in ovarian cortex to study the physical properties. Comparing the physical properties, we objectively describe an increased cortical stiffness in the most outer part of the ovarian cortex following prolonged testosterone administration in transgender men compared to the ovarian cortex of oncological patients. This preliminary and novel approach could be the start of future research to understand the physical properties of ovarian tissue. Electronic supplementary material The online version of this article (10.1007/s10815-019-01513-x) contains supplementary material, which is available to authorized users.

The authors wish to make the following correction to the paper [...]

To date, the treatment of articular cartilage lesions remains challenging. A promising strategy for the development of new regenerative therapies is hybrid bioprinting, combining the principles of developmental biology, biomaterial science, and 3D bioprinting. In this approach, scaffold-free cartilage microtissues with small diameters are used as building blocks, combined with a photo-crosslinkable hydrogel and subsequently bioprinted. Spheroids of human bone marrow-derived mesenchymal stem cells (hBM-MSC) are created using a high-throughput microwell system and chondrogenic differentiation is induced during 42 days by applying chondrogenic culture medium and low oxygen tension (5%). Stable and homogeneous cartilage spheroids with a mean diameter of 116 ± 2.80 μm, which is compatible with bioprinting, were created after 14 days of culture and a glycosaminoglycans (GAG)- and collagen II-positive extracellular matrix (ECM) was observed. Spheroids were able to assemble at random into a macrotissue, driven by developmental biology tissue fusion processes, and after 72 h of culture, a compact macrotissue was formed. In a directed assembly approach, spheroids were assembled with high spatial control using the bio-ink based extrusion bioprinting approach. Therefore, 14-day spheroids were combined with a photo-crosslinkable methacrylamide-modified gelatin (gelMA) as viscous printing medium to ensure shape fidelity of the printed construct. The photo-initiators Irgacure 2959 and Li-TPO-L were evaluated by assessing their effect on bio-ink properties and the chondrogenic phenotype. The encapsulation in gelMA resulted in further chondrogenic maturation observed by an increased production of GAG and a reduction of collagen I. Moreover, the use of Li-TPO-L lead to constructs with lower stiffness which induced a decrease of collagen I and an increase in GAG and collagen II production. After 3D bioprinting, spheroids remained viable and the cartilage phenotype was maintained. Our findings demonstrate that hBM-MSC spheroids are able to differentiate into cartilage microtissues and display a geometry compatible with 3D bioprinting. Furthermore, for hybrid bioprinting of these spheroids, gelMA is a promising material as it exhibits favorable properties in terms of printability and it supports the viability and chondrogenic phenotype of hBM-MSC microtissues. Moreover, it was shown that a lower hydrogel stiffness enhances further chondrogenic maturation after bioprinting. ispartof: FRONTIERS IN BIOENGINEERING AND BIOTECHNOLOGY vol:8 ispartof: location:Switzerland status: published

Given the complex calcified nature of the fibrous bone tissue, a combinatorial approach merging specific topographical/biochemical cues was adopted to design bone tissue-engineered scaffolds. Coral having a Ca-enriched structure was added to electrospun chitosan (CS)/polyethylene oxide (PEO) nanofibers that were subjected to plasma surface modifications using a medium pressure Ar, air or N2 dielectric barrier discharge. Plasma incorporated oxygen- and nitrogen-containing functionalities onto the nanofibers surface thus enhancing their wettability. Plasma treatment enhanced the performance of osteoblasts and the interplay between plasma treatment and coral was shown to boost initial cell adhesion. The fibers capacity to trigger calcium phosphate growth was predicted via immersion in simulated body fluid. Globular carbonate apatite nanocrystals were deposited on plasma-treated CS/PEO NFs while thicker layers of flake-like nanocrystals were covering plasma-treated Coral/CS/PEO fibers without blocking the interfibrous pores. Overall, the exclusive multifaceted plasma-treated Coral/CS/PEO nanofibers are believed to revolutionize the bone tissue engineering field.

The prominent success of polycaprolactone (PCL) bioengineered fibrous scaffolds has expanded the use of PCL over other polymers in the wide electrospinning literature. Several highly toxic solvent systems providing a good PCL solubility-spinability are recurrently applied in the overwhelming majority of studies. One of the current major focuses revolves around the challenging generation of aligned fibers that are very desirable in numerous tissue engineering applications. Moreover, the critical influence of fiber size on cellular performance has led to the use of different solvent systems for the production of specific nano- or micro-sized PCL fibers while neglecting the solvents toxicity. Therefore, our goal is to use the unconventional solvent system acetic acid/formic acid of very low toxicity, recently defined as the system producing ultra-thin PCL fibers, in a trial to outspread the size range and to tackle fiber alignment. After profound analysis of the effect of varying collector motion and collector design on fiber alignment, a novel collector producing highly aligned PCL fibers based on synchronic mechanical and electrical effects is designed. In a subsequent step, the fiber diameter is manipulated by analyzing 3 influential parameters: polymer concentration, tip-to-collector distance and the frequently overlooked parameter humidity. The parameters fine-tuning study has resulted in very broad PCL fiber diameter ranges of 94–1548 nm and 114–1408 nm for random and aligned fibers respectively. PCL fibers properties are also characterized in this study by means of water contact angle (WCA), X-ray photoelectron spectroscopy (XPS) and tensile measurements. Despite the detection of the same surface chemical composition on all fiber conditions, the WCA values tend to decrease with increased fiber diameters, especially for aligned fibers. Moreover, aligning the fibers and decreasing their size is found to lead to considerably enhanced mechanical properties. Overall, it can be concluded that this work represents a picture-perfect reference for the electrospinning of PCL fibers having different orientations, diameters and physico-chemical properties from a benign solvent system.

To engineer tissues with clinically relevant dimensions by three-dimensional bioprinting, an extended vascular network with diameters ranging from the macro- to micro-scale needs to be integrated. Extrusion-based bioprinting is the most commonly applied bioprinting technique but due to the limited resolution of conventional bioprinters, the establishment of a microvascular network for the transfer of oxygen, nutrients and metabolic waste products remains challenging. To answer this need, this study assessed the potential and processability of spheroids, containing a capillary-like network, to be used as micron-sized prevascularized units for incorporation throughout the bioprinted construct. Prevascularized spheroids were generated by combining endothelial cells with fibroblasts and adipose tissue-derived mesenchymal stem cells as supporting cells. To serve as a viscous medium for the bioink-based deposition by extrusion printing, spheroids were combined with a photo-crosslinkable methacrylamide-modified gelatin (gelMA) and Irgacure 2959. The influence of gelMA encapsulation, the printing process and photo-crosslinking conditions on spheroid viability, proliferation and vascularization were analyzed by live/dead staining, immunohistochemistry, gene expression analysis and sprouting analysis. Stable spheroid-laden constructs, allowing spheroid outgrowth, were achieved by applying 10 min UV-A photo-curing (365 nm, 4 mW cm-2), while the construct was incubated in an additional Irgacure 2959 immersion solution. Following implantationin ovoonto a chick chorioallantoic membrane, the prevascular engineered constructs showed anastomosis with the host vasculature. This study demonstrated (a) the potential of triculture prevascularized spheroids for application as multicellular building blocks, (b) the processability of the spheroid-laden gelMA bioink by extrusion bioprinting and (c) the importance of photo-crosslinking parameters post printing, as prolonged photo-curing intervals showed to be detrimental for the angiogenic potential and complete vascularization of the construct post printing.

This study was set up to identify the native trochlear geometry and define its relationship with the rotational landmarks of the distal femur. The rotational landmarks of the distal femur were analysed on CT-scans of 281 patients with end-stage knee osteoarthritis. The anterior trochlear line (ATL) was on average 4.3° (SD 3.3°) internally rotated relative to the surgical transepicondylar axis (sTEA). The ATL was on average 2.1° (SD 3.0°) internally rotated relative to the posterior condylar line (PCL). The relationship between the ATL and the sTEA was statistically different in the different coronal alignment groups (p = 0.004): 3.9° (SD 3.0°) in varus knees, 4.0° (SD 2.9°) in neutral knees and 5.4° (SD 3.8°) in valgus knees. The lateralisation of the trochlea, represented by the distance between the perpendicular to PCL and the perpendicular to the posterior parallel line to the sTEA, was on average 2.2 mm (SD 1.8 mm). The ATL was on average 4.3° (SD 3.3°) internally rotated relative to the sTEA and 2.1° (SD 3.0°) internally rotated relative to the PCL. The ATL is more externally orientated in varus knees and more internally rotated in valgus knees. The trochlear groove is lateralised by only 2.2 mm when the femoral component is externally rotated. III.

The objective of this study was the development of Ag-rich antibacterial coatings on titanium to prevent post-operative infections. A series of Ag-doped TiO2 coatings were synthesized on Ti discs by plasma electrolytic oxidation in an electrolyte containing AgNPs. The incorporation, distribution and chemical composition of the AgNPs on Ti were determined using scanning electron microscopy-energy dispersive spectroscopy. The crystalline structure and wettability of the coating was characterized by X-ray diffraction and water contact angle analysis respectively. Surface roughness and hardness of the coating were examined using surface profilometry and Knoop indentation test respectively, while silver ion release was quantified using inductively coupled plasma-mass spectroscopy. Following PEO, the surface of the Ti substrate was converted to TiO2 composed of anatase and rutile phases. The SEM micrographs showed that the AgNPs were distributed throughout the oxide layer, without changing the morphology of the coating. The coatings also revealed an increased surface roughness, microhardness and improved surface wettability relative to untreated Ti substrates. Furthermore, the incorporation of Ag into the coating did not alter the phase component, roughness, microhardness and wettability. A series of in-vitro antibacterial assays indicated that increasing the number of AgNPs in the electrolyte led to excellent antibacterial activities.

For patients with soft tissue defects, repair with autologous in vitro engineered adipose tissue could be a promising alternative to current surgical therapies. A volume-persistent engineered adipose tissue construct under in vivo conditions can only be achieved by early vascularization after transplantation. The combination of 3D bioprinting technology with self-assembling microvascularized units as building blocks can potentially answer the need for a microvascular network. In the present study, co-culture spheroids combining adipose-derived stem cells (ASC) and human umbilical vein endothelial cells (HUVEC) were created with an ideal geometry for bioprinting. When applying the favourable seeding technique and condition, compact viable spheroids were obtained, demonstrating high adipogenic differentiation and capillary-like network formation after 7 and 14 days of culture, as shown by live/dead analysis, immunohistochemistry and RT-qPCR. Moreover, we were able to successfully 3D bioprint the encapsulated spheroids, resulting in compact viable spheroids presenting capillary-like structures, lipid droplets and spheroid outgrowth after 14 days of culture. This is the first study that generates viable high-throughput (pre-)vascularized adipose microtissues as building blocks for bioprinting applications using a novel ASC/HUVEC co-culture spheroid model, which enables both adipogenic differentiation while simultaneously supporting the formation of prevascular-like structures within engineered tissues in vitro.

The increasing number of mastectomies results in a greater demand for breast reconstruction characterized by simplicity and a low complication profile. Reconstructive surgeons are investigating tissue engineering (TE) strategies to overcome the current surgical drawbacks. 3D bioprinting is the rising technique for the fabrication of large tissue constructs which provides a potential solution for unmet clinical needs in breast reconstruction building on decades of experience in autologous fat grafting, adipose-derived mesenchymal stem cell (ASC) biology and TE. A scaffold was bioprinted using encapsulated ASC spheroids in methacrylated gelatin ink (GelMA). Uniform ASC spheroids with an ideal geometry and diameter for bioprinting were formed, using a high-throughput non-adhesive agarose microwell system. ASC spheroids in adipogenic differentiation medium (ADM) were evaluated through live/dead staining, histology (HE, Oil Red O), TEM and RT-qPCR. Viable spheroids were obtained for up to 14 days post-printing and showed multilocular microvacuoles and successful differentiation toward mature adipocytes shown by gene expression analysis. Moreover, spheroids were able to assemble at random in GelMA, creating a macrotissue. Combining the advantage of microtissues to self-assemble and the controlled organization by bioprinting technologies, these ASC spheroids can be useful as building blocks for the engineering of soft tissue implants.

Objective: The aim of this in vitro study was to determine the effects of remineralization promoting agents containing casein phosphopeptide-stabilized amorphous calcium phosphate (CPP-ACP), or CPP-ACP in combination with fluoride (CPP-ACPF) on artificial white spot lesions (WSLs) after 6 and 12 weeks. Methodology: White spot lesions were created on 123 sectioned premolars (246 specimens) with a demineralization solution during a 96 hours pH-cycling regime. Two experimental groups were created: a CPP-ACP group (Tooth Mousse (TM)), and a CPP-ACPF group (Mi Paste Plus (TM)). Additionally, two control groups were created, one using only a conventional toothpaste (1450 ppm fluoride) and another one without any working agents. All teeth were also daily brushed with the conventional toothpaste except the second control group. Tooth Mousse (TM) and Mi Paste Plus (TM) were applied for 180 seconds every day. The volume of demineralization was measured with transverse microradiography. Six lesion characteristics regarding the lesion depth and mineral content of WSLs were also determined. Results: The application of CPP-ACP and CPP-ACPF had a significant regenerative effect on the WSLs. Compared to Control group 1 and 2 the volume of demineralization after 6 weeks decreased significantly for CPP-ACP (respectively p

In hybrid bioprinting of cartilage tissue constructs, spheroids are used as cellular building blocks and combined with biomaterials for dispensing. However, biomaterial intrinsic cues can deeply affect cell fate and to date, the influence of hydrogel encapsulation on spheroid viability and phenotype has received limited attention. This study assesses this need and unravels 1) how the phenotype of spheroid-laden constructs can be tuned through adjusting the hydrogel physico-chemical properties and 2) if the spheroid maturation stage prior to encapsulation is a determining factor for the construct phenotype. Articular chondrocyte spheroids with a cartilage specific extracellular matrix (ECM) are generated and different maturation stages, early-, mid-, and late-stage (3, 7, and 14 days, respectively), are harvested and encapsulated in 10, 15, or 20 w/v% methacrylamide-modified gelatin (gelMA) for 14 days. The encapsulation of immature spheroids do not lead to a cartilage-like ECM production but when more mature mid- or late-stage spheroids are combined with a certain concentration of gelMA, a fibrocartilage-like as well as a hyaline cartilage-like phenotype can be induced. As a proof of concept, late-stage spheroids are bioprinted using a 10 w/v% gelMA-Irgacure 2959 solution with the aim to test the processing potential of the spheroid-laden bioink.

Objective Bioactive glasses (BAG) form, in contrast to formerly used implant materials, a stable bond with tissues, especially bone, when implanted. Nowadays BAGs are often mixed with a cement/composite that hardens in situ to broaden its applications in dentistry or orthopedics. The bioactivity and biocompatibility of possible BAG candidates for BAG-cement/composite development were evaluated. Methods Two fluoride containing BAGs were tested: a Na + -containing (45S5F), based on the first commercial BAG, and a Na + -free BAG (CF9), with a higher Ca 2+ and PO 4 3− content. BAGs were tested on their bioactivity upon immersion in SBF for 7 days by evaluating the surface changes by FT-IR, SEM, EDS and PO 4 3− and Ca 2+ uptake and/or release from SBF. Moreover, the biocompatibility of the BAGs was investigated with a direct contact cell viability study with HFF cells and a cell adhesion study with MG-63 cells. Results The Na + -free BAG, CF9, showed the highest potential to bioactivate cements because of its high Ca 2+ -release and apatite (Ap) formation, as evidenced by SEM pictures and corresponding EDX patterns. FT-IR confirmed the formation of an Ap layer. Moreover CF9 had a higher biocompatibility than 45S5F. Significance For the bioactivation of GICs/composites in order to enhance bonding and remineralization of surrounding tissues, fluoride containing BAG may have advantages over other BAGs as a more stable fluorapatite can be formed. CF9 may be an excellent candidate therefore.

Insufficient glenoid fixation is one of the main reasons for failure in total shoulder arthroplasty. This is predominantly caused by the inert nature of the ultra-high molecular weight polyethylene (UHMWPE) used in the glenoid component of the implant, which makes it difficult to adhesively bind to bone cement or bone. Previous studies have shown that this adhesion can be ameliorated by changing the surface chemistry using plasma technology. An atmospheric pressure plasma jet is used to treat UHMWPE substrates and to modify their surface chemistry. The modifications are investigated using several surface analysis techniques. The adhesion with bone cement is assessed using pull-out tests while osteoblast adhesion and proliferation is also tested making use of several cell viability assays. Additionally, the treated samples are put in simulated body fluid and the resulting calcium phosphate (CaP) deposition is evaluated as a measure of the in vitro bioactivity of the samples. The results show that the plasma modifications result in incorporation of oxygen in the surface, which leads to a significant improved adhesion to bone cement, an enhanced osteoblast proliferation and a more pronounced CaP deposition. The plasma-treated surfaces are therefore promising to act as a shoulder implant.

Biopolymers are often subjected to surface modification in order to improve their surface characteristics. The goal of this study is to show the use of plasma technology to enhance the adhesion of ultra-high molecular weight polyethylene (UHMWPE) shoulder prostheses. Two different plasma techniques (low pressure plasma activation and atmospheric pressure plasma polymerization) are performed on UHMWPE to increase the adhesion between (1) the polymer and polymethylmethacrylate (PMMA) bone cement and (2) the polymer and osteoblast cells. Both techniques are performed using a dielectric barrier discharge (DBD). A previous paper showed that low pressure plasma activation of UHMWPE results in the incorporation of oxygen-containing functional groups, which leads to an increased surface wettability. Atmospheric pressure plasma polymerization of methylmethacrylate (MMA) on UHMWPE results in a PMMA-like coating, which could be deposited with a high degree of control of chemical composition and layer thickness. The thin film also proved to be relatively stable upon incubation in a phosphate buffer solution (PBS). This paper discusses the next stage of the study, which includes testing the adhesion of the plasma-activated and plasma-polymerized samples to bone cement through pull-out tests and testing the cell adhesion and proliferation on the samples. In order to perform the pull-out tests, all samples were cut to standard dimensions and fixed in bone cement in a reproducible way with a sample holder specially designed for this purpose. The cell adhesion and proliferation were tested by means of an MTS assay and live/dead staining after culturing MC3T3 osteoblast cells on UHMWPE samples. The results show that both plasma activation and plasma polymerization significantly improve the adhesion to bone cement and enhance cell adhesion and proliferation. In conclusion, it can be stated that the use of plasma technology can lead to an implant with improved quality and a subsequent longer lifespan.

Background: Glass carbomers, such as GCP Glass Fill, are a type of GICs, which have nanosized apatite added to their composition. The manufacturer describes this material to have remineralizing properties. Objectives: This study aimed to evaluate the bioactivity of this material and the effect of finishing by thermocuring and gloss on its properties. Methods: Bioactivity was measured by Ca and PO4 release studies, SEM, FT-IR, as well as EDX. Mechanical properties were measured by a compressive strength test. Results: Cements of all finishing types (with/without gloss and/or thermocuring) had comparable and acceptable initial compressive strengths. After an incubation period, all strengths decreased. Conclusions: Although GCP Glass Fill should be bioactive, no signs of bioactivity after incubation in SBF were observed. Moreover, the finishing conditions with Glass and thermocuring do not improve the mechanical properties of the cement. Therefore, this material is not superior to e.g. GICs.

Morphology, crystallinity, thermal, and mechanical properties of nanofibrous mats are known to highly affect the behavior of these materials in desired applications. In this study, multiple characteristics of poly(lactic acid) (PLA) nanofibrous mats prepared from plasma-treated pre-electrospinning solutions are studied as a function of various plasma operational parameters. X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, and tensile tests are performed. In addition, the pristine and plasma-treated PLA solutions are examined with size exclusion chromatography to study the effect of the conducted pre-electrospinning plasma treatments (PEPT) on the molecular weight of PLA. Aging analysis of the pristine and plasma-treated solutions is also performed by evaluating the viscosity, conductivity, surface tension, and pH during an aging period of 10 days. To investigate if the results are only affected by the plasma treatment or also affected by the electrospinning, pristine and plasma-treated PLA cast layers are also analyzed. The results reveal that PEPT preserved the surface chemical composition of the nanofibers and the molecular weight distribution of PLA, while morphology and mechanical properties of the nanofibers are considerably enhanced. Moreover, plasma-treated polymer solutions resulted in the formation of nicely elongated nanofibers up to 4 days after plasma treatment.

Objectives Glass ionomer cements (GICs) are a subject of research because of their inferior mechanical properties, despite their advantages such as fluoride release and direct bonding to bone and teeth. Recent research aims to improve the bioactivity of the GICs and thereby improve mechanical properties on the long term. In this study, two types of bioactive glasses (BAG) (45S5F and CF9) are combined with GICs to evaluate the physico-chemical properties and biocompatibility of the BAG-GIC combinations. The effect of the addition of Al3+ to the BAG composition and the use of smaller BAG particles on the BAG-GIC properties was also investigated. Materials and methods Conventional aluminosilicate glass (ASG) and (modified) BAG were synthesized by the melt method. BAG-GIC were investigated on setting time, compressive strength and bioactivity. Surface changes were evaluated by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), EDS and PO43− -and Ca2+ uptake in SBF. Biocompatibility of selected BAG-GICs was determined by a direct toxicity assay. Results The addition of BAG improves the bioactivity of the GIC, which can be observed by the formation of an apatite (Ap) layer, especially in CF9-containing GICs. More BAG leads to more bioactivity but decreases strength. The addition of Al3+ to the BAG composition improves strength, but decreases bioactivity. BAGs with smaller particle sizes have no effect on bioactivity and decrease strength. The formation of an Ap layer seems beneficial to the biocompatibility of the BAG-GICs. Significance Bioactive GICs may have several advantages over conventional GICs, such as remineralization of demineralized tissue, adhesion and proliferation of bone- and dental cells, allowing integration in surrounding tissue. CF9 BAG-GIC combinations containing maximum 10 mol% Al3+ are most promising, when added in ≤20 wt% to a GIC.

Background. Optimal pit and fissure sealing is determined by surface preparation techniques and choice of materials. Aim. This study aimed (i) to compare the microleakage and penetration depth of a hydrophilic sealant and a conventional resin-based sealant using one of the following preparation techniques: acid etching (AE) only, a diamond bur + AE, and Er:YAG laser combined with AE, and (ii) to evaluate the microleakage and penetration depth of the hydrophilic pit and fissure sealant on different surface conditions. Design. Eighty recently extracted 3rd molars were randomly assigned to eight groups of ten teeth according to the material, preparation technique, and surface condition. For saliva contamination, 0.1 mL of fresh whole human saliva was used. All samples were submitted to 1000 thermal cycles and immersed in 2% methylene blue dye for 4 h. Sections were examined by a light microscope and analysed using image analysis software (Sigmascan (R)). Results. The combination of Er:YAG + AE + conventional sealant showed the least microleakage. The sealing ability of the hydrophilic sealant was influenced by the surface condition. Conclusion. Er:YAG ablation significantly decreased the microleakage at the toothsealant interface compared to the non-invasive technique. The hydrophilic sealant applied on different surface conditions showed.

The study evaluates the biomechanical properties of single-strand and single-loop tibialis (anterior and posterior) tendon allografts. A comparison was made with bone-patellar tendon-bone (BPTB) allografts. Sixty-four tendon allografts were evaluated in this study. Sixteen of these were single-strand tibialis anterior (TA) and 16 single-strand tibialis posterior (TP) tendons. Sixteen single-loop TA and TP tendons were also tested. The fourth group was composed of 16 BPTB allografts. The biomechanical properties determined were maximal load, stiffness, cross-sectional area and elongation. The results of this study showed that the maximal load of the single-loop tibialis tendons (1,553 +/- 62 N) was greater than of the BPTB (1,139 +/- 99 N), TA (776 +/- 43 N) and TP (888 +/- 64 N) tendons. The stiffness of the single-loop tibialis tendons (236 +/- 10 N/mm) was also greater than of the BPTB (168 +/- 13 N/mm), TA (60 +/- 2 N/mm) and TP (73 +/- 5 N/mm) tendons. The cross-sectional area of the BPTB tendons was 67 +/- 5 mm(2), of the single-loop tibialis tendons 36 +/- 2 mm(2), of the TA tendons 20 +/- 1 mm(2), and of the TP tendons 23 +/- 1 mm(2). The elongation of the single-loop tibialis tendons and of the BPTB tendons was almost similar (7 +/- 0.4 mm). The same applied to the TA and TP tendons (14 +/- 0.6 mm). The results of this in vitro mechanical study suggest that fresh-frozen single-loop TA and TP tendons, and BPTB allografts are an acceptable substitute for hamstrings in anterior cruciate ligament reconstruction.

Steyaert AE, Burssens PJ, Vercruysse CW, Vanderstraeten GG, Verbeeck RM. The effects of substance P on the biomechanic properties of the ruptured rat Achilles' tendon. Objective To determine whether injection of substance P into the paratendinous region of a ruptured and subsequently sutured rat Achilles' tendon alters the biomechanic properties of the tendon. Design Interventional animal study. Setting Animal laboratory at a university hospital. Animals Ninety-six 2-month-old, male Sprague-Dawley rats. Intervention Injection of saline, substance P (10 –6 μmol/kg of body weight [BW] or 10 –8 μmol/kg BW) associated with neutral endopeptidase inhibitors, or neutral endopeptidase inhibitors alone into the paratendinous region of ruptured and subsequently sutured rat Achilles' tendons from the second until the sixth day postoperatively. Main Outcome Measures Stress at maximal load and work to maximal load and stiffness. Results Stress at maximal load was higher in the groups injected with substance P than in the saline group in the first, second, and sixth weeks. Work to maximal load was higher from the second until the sixth weeks in the substance P–treated groups than in the saline group. Stiffness did not differ between the 4 groups in any of the weeks. Conclusions Injection of substance P into the paratendinous region of ruptured and subsequently sutured rat Achilles' tendons improved tendon healing by enhancing stress at maximal load and work to maximal load. However, stiffness was not significantly affected.

This study investigated the in vitro conversion reaction in calcium phosphate cements (CPCs) containing octacalcium phosphate (OCP) as one of the reagents. OCP is known to be a precursor for apatite formation in vivo. The reaction products were characterized using infrared spectroscopy and X-ray diffraction. Although the conversion of OCP into hydroxyapatite is thermodynamically favorable, OCP only yields apatite formation in CPC provided it is combined with a highly soluble Ca2+ and OH− releasing reaction partner. In this respect, tetracalcium phosphate is a promising compound. Adding small amounts of monocalcium phosphate monohydrate can stimulate the setting through intermediate brushite formation. The preparation method of OCP might drastically affect the performance of the cement. The reaction path of the setting of these CPC probably does not conform to the singular point principle described in the literature, and an in situ hydrolysis of OCP to apatite is conceivable. Simulation of apatite formation using OCP as the precursor and/or seed in CPC might be beneficial for some biomedical applications. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 52, 95–106, 2000.

Dental glass-ionomer cements (GIC) set by an acid-base reaction between a polyalkenoic acid and an ion-leachable glass. The exact relationship between the glass composition and the setting and final properties of GIC is not yet fully elucidated. As part of a systematic study of this relationship, we studied the leaching stoichiometry of glasses used in commercial formulations to correlate the glass composition with its leaching properties. The leaching experiments were performed in acetic acid solutions at pH = 3.4 by means of a pH-stat method. After predetermined time intervals, the suspension was filtered and the filtrate was analyzed for the glass constituents. The usefulness of the pH-stat method for the determination of glass reactivity was corroborated. The deviation of the leaching stoichiometry with respect to the pure glass stoichiometry decreased with increasing relative content of mono- and bivalent glass network dwellers and modifiers. Indications were found that the latter can be leached out independently and preferentially, while the leaching of network dwellers is coupled with the aluminum release. The F content as well as the reactivity of the glass affect the amount of fluoride available for release from a set GIC. It could be concluded that the leaching stoichiometry of GIC glasses can be correlated with their absolute and relative composition.

The glass component critically determines the properties of glass-ionomer cements (GIC). However, the exact relationship between the composition of the glass and these properties is not yet fully understood. To investigate this relationship, we studied the reactivity of glasses used in commercial GIC in acetic acid solutions, using a pH-stat method. Qualitative differences in the leaching behavior of these glasses can be explained by different pre-treatments. Acid-washing and silanization modify the surfaces of the glass particles, thus inducing a delay of the leaching process, whereas untreated glasses exhibit a fast initial leaching, but their acid reactivity slows very soon. Quantitative differences in acid reactivity can be correlated with the mean chemical composition of the glasses. In this respect, the leaching tends to increase with an increasing ratio of network-dwelling cations to Al 3+ ions. These results provide a fundamental basis for the explanation, prediction, and control of cement properties as a function of glass characteristics.

Glass ionomer cements (GIC) are clinically accepted dental restorative materials mainly due to their direct chemical adhesion to both enamel and dentin and their ability to release fluoride. However, their mechanical properties are inferior compared to those of amalgam and composite. The aim of this study is to investigate if combinations of nano- and macrogranular glass with different compositions in a glass ionomer cement can improve the mechanical and physical properties.Glasses with the composition 4.5 SiO2-3 Al2O3-1.5 P2O5-(5-x) CaO-x CaF2 (x=0 and x=2) were prepared. Of each type of glass, particles with a median size of about 0.73 μm and 6.02 μm were made.The results show that the setting time of GIC decreases when macrogranular glass particles are replaced by nanogranular glass particles, whereas the compressive strength and Young's modulus, measured after 24 h setting, increase. The effects are more pronounced when the nanogranular glass particles contain fluoride. After thermocycling, compressive strength decreases for nearly all formulations, the effect being most pronounced for cements containing nanogranular glass particles. Hence, the strength of the GIC seems mainly determined by the macrogranular glass particles. Cumulative F--release decreases when the macrogranular glass particles with fluoride are replaced by nanogranular glass particles with(out) fluoride.The present study thus shows that replacing macro- by nanogranular glass particles with different compositions can lead to cements with approximately the same physical properties (e.g. setting time, consistency), but with different physicochemical (e.g. F--release, water-uptake) and initial mechanical properties. On the long term, the mechanical properties are mainly determined by the macrogranular glass particles.

Optimal pit and fissure sealing is determined by surface preparation techniques and choice of materials.This study aimed (i) to compare the microleakage and penetration depth of a hydrophilic sealant and a conventional resin-based sealant using one of the following preparation techniques: acid etching (AE) only, a diamond bur + AE, and Er:YAG laser combined with AE, and (ii) to evaluate the microleakage and penetration depth of the hydrophilic pit and fissure sealant on different surface conditions.Eighty recently extracted 3rd molars were randomly assigned to eight groups of ten teeth according to the material, preparation technique, and surface condition. For saliva contamination, 0.1 mL of fresh whole human saliva was used. All samples were submitted to 1000 thermal cycles and immersed in 2% methylene blue dye for 4 h. Sections were examined by a light microscope and analysed using image analysis software (Sigmascan(®)).The combination of Er:YAG + AE + conventional sealant showed the least microleakage. The sealing ability of the hydrophilic sealant was influenced by the surface condition.Er:YAG ablation significantly decreased the microleakage at the tooth-sealant interface compared to the non-invasive technique. The hydrophilic sealant applied on different surface conditions showed comparable result to the conventional resin-based sealant.

Objectives: The present study aimed to compare the curing depth of polyacid-modified composite resins (PAM-C) and some representative composite resins as a function of shade and post-cure using a scraping method and a penetrometer. Methods: The curing depth of the PAM-C Hytac, F2000, Glasiosite, Dyract, Dyract AP, and Compoglass F and of the composite resins Durafill VS and Z100 were determined for shade A2 and A4 using a scraping method based on ISO 4049:2000 and a digital penetrometer. Samples were light-cured (800 mW/cm2 at 40 s) in bulk in split stainless steel molds. Immediately after light-curing or after a 24 h post-cure, the height of the cylinder of cured material was measured and taken as the curing depth. Results: For both test methods, the curing depth was independent of post-cure (P≥0.05), but differed significantly among materials and shade (P

The composition of glasses used in glass-ionomer cements affects their leaching behavior and hence the properties of the cement. The aim of this study was to correlate the composition and leaching behavior of these glasses with their infrared absorption characteristics. The wavenumber of the absorption band of the Si-O asymmetric stretching vibration ῡAS shifts to a higher value with decreasing content of mono- and bivalent cations in the glass. This effect can be ascribed to the influence of these extraneous ions on the glass network order and connectivity. Preferential leaching of these ions induces an increase of ῡAS and a general modification of the band profile. The results can be correlated with the x-ray diffraction characteristics of the glass. A decrease in the Si-O-Si angle could be caused by a decrease in the distortions in the (arrangement of the) SiO4 tetrahedra; the tetrahedra as well as their arrangement can be distorted.

Objectives: The aim of this study was to investigate the influence of the proprietary bonding agents Hytac OSB (OSB) (Espe), Prime&Bond 2.1 (PB) (Dentsply DeTrey) and Syntac Single Component (SSC) (Vivadent) on the fluoride release of the corresponding polyacid-modified composite resins Hytac (HTC), Dyract AP (DAP) and Compoglass F (CGF), respectively. Methods: Ten cylindrical specimens (6 mm diameter and 3 mm thick) of each polyacid-modified composite were prepared according to the manufacturers' instructions: five with bonding agent applied and five without bonding agent as a control. The specimens were immersed individually in 10 ml ultra-pure water at 37°C immediately after light-curing of the polyacid-modified composite resins. Over 140 days, the water was regularly renewed and the fluoride concentration eluted during each period was determined with a combined fluoride ion selective electrode. Results: The fluoride release decreases according to the sequence: CGF>DAP>HTC. The bonding agent significantly reduces the fluoride released by DAP and CGF, respectively, by a factor 2–3 and ±1.4. For HTC, the bonding agent reduces the fluoride released initially by a factor of ±2, but the difference between the fluoride release with and without bonding agent becomes insignificant after approximately 3 weeks. Significance: It can be concluded that the use of bonding agent can significantly reduce fluoride release of polyacid-modified composite resins in the long-term, and especially in the short-term. The decrease in fluoride release might reduce the material's potential to prevent recurrent caries.