Three-dimensional digital assessment of typodont activations.

OBJECTIVES: Wax typodonts are widely used as pre-clinical teaching tools to test and research the complex force systems created by archwire activations, however, a limitation is the inability to quantify the resultant statically indeterminate tooth movements. The aim of this study was to develop an analogue-to-digital typodont system to quantify the effects of archwire activations on individual typodont teeth in three dimensions. METHODS: The typodont system was developed using CAD/CAM technology. Posterior expansion, squared, tapered, asymmetrical arch forms and reversed curve of Spee activations were tested with three repeats. The resulting three-dimensional movements of individual typodont teeth were assessed with six degrees of freedom (df). Cartesian coordinate systems were set for each tooth. Mesio-distal, bucco-lingual and intrusive-extrusive movements were assessed as changes in the location of the geometrically estimated centre of resistance in the x, y and z axes, respectively. Torque, tip and rotation movements were assessed as the rotations around the mesio-distal, bucco-lingual and intrusive-extrusive axes, respectively. RESULTS: Individual typodont tooth displacements from each activation could reliably be described with six df. The transversal-to-sagittal movement ratio ranged from 2:1 to 7:1, depending on the activation. Asymmetrical arch form activations caused a midline shift and affected the lateral overjet. Reversing the curve of Spee led to intrusion of incisors and second molars, extrusion of premolars and first molars and pronounced first and third order effects. CONCLUSION: The digital typodont system is a promising teaching tool. The tested activations have implications in three dimensions, which should be considered when planning tooth movements.

Silk fibroin nanoscaffolds for neural tissue engineering.

The nervous system is a crucial component of the body and damages to this system, either by injury or disease, can result in serious or potentially lethal consequences. An important problem in neural engineering is how we can stimulate the regeneration of damaged nervous tissue given its complex physiology and limited regenerative capacity. To regenerate damaged nervous tissue, this study electrospun three-dimensional nanoscaffolds (3DNSs) from a biomaterial blend of silk fibroin (SF), polyethylene glycol (PEG), and polyvinyl alcohol (PVA). The 3DNSs were characterised to ascertain their potential suitability for direct implant into the CNS. The biological activity of 3DNSs was investigated in vitro using PC12 cells and their effects on reactive astrogliosis were assessed in vivo using a photothrombotic model of ischaemic stroke in mice. Results showed that the concentration of SF directly affected the mechanical characteristics and internal structure of the 3DNSs, with formulations presenting as either a gel-like structure (SF ≥ 50%) or a nanofibrous structure (SF ≤ 40%). In vitro assessment revealed increased cell viability in the presence of the 3DNSs and in vivo assessment resulted in a significant decrease in glial fibrillary acidic protein (GFAP) expression in the peri-infarct region (p < 0.001 for F2 and p < 0.05 for F4) after stroke, suggesting that 3DNSs could be suppressing reactive astrogliosis. The findings enhanced our understanding of physiochemical interactions between SF, PEG, and PVA, and elucidated the potential of 3DNSs as a potential therapeutic approach to stroke recovery, especially if these are used in conjunction with drug or cell treatment.

Current and novel polymeric biomaterials for neural tissue engineering.

The nervous system is a crucial component of the body and damages to this system, either by of injury or disease, can result in serious or potentially lethal consequences. Restoring the damaged nervous system is a great challenge due to the complex physiology system and limited regenerative capacity.Polymers, either synthetic or natural in origin, have been extensively evaluated as a solution for restoring functions in damaged neural tissues. Polymers offer a wide range of versatility, in particular regarding shape and mechanical characteristics, and their biocompatibility is unmatched by other biomaterials, such as metals and ceramics. Several studies have shown that polymers can be shaped into suitable support structures, including nerve conduits, scaffolds, and electrospun matrices, capable of improving the regeneration of damaged neural tissues. In general, natural polymers offer the advantage of better biocompatibility and bioactivity, while synthetic or non-natural polymers have better mechanical properties and structural stability. Often, combinations of the two allow for the development of polymeric conduits able to mimic the native physiological environment of healthy neural tissues and, consequently, regulate cell behaviour and support the regeneration of injured nervous tissues.Currently, most of neural tissue engineering applications are in pre-clinical study, in particular for use in the central nervous system, however collagen polymer conduits aimed at regeneration of peripheral nerves have already been successfully tested in clinical trials.This review highlights different types of natural and synthetic polymers used in neural tissue engineering and their advantages and disadvantages for neural regeneration.

Removal of silicone oil: prognostic factors and incidence of retinal redetachment.

PURPOSE: To evaluate the incidence of retinal redetachment after the removal of silicone oil endotamponade for complicated retinal detachment and identify possible factors affecting outcome. METHODS: This is a retrospective review of 173 patients who underwent pars plana vitrectomy with silicone oil tamponade for complex retinal detachment and subsequent removal of silicone oil (ROSO). The outcome factors studied included anatomical success, best-corrected visual acuity and intraocular pressure pre- and post-ROSO. RESULTS: Anatomical success was achieved in 167 of the 173 eyes (96.5%) after ROSO. The mean duration of silicone oil tamponade was 70 ± 48 weeks (median, 56 weeks; mode, 48 weeks). The cause for primary retinal detachment was proliferative diabetic retinopathy in 36 (20.8%) and proliferative vitreoretinopathy in 137 of 173 cases (79.2%). Best-corrected visual acuity of greater than 20/100 was achieved in 83 cases (49.4%) at 3 months after ROSO. Levene's test for equality of variances was used to determine the association between previous unsuccessful retinal surgeries and redetachment (P = 0.523) and between duration of endotamponade and anatomical success (P = 0.451). CONCLUSION: The incidence of retinal redetachment after ROSO in our study was 3.46%. Aggressive removal of the vitreous base, performing retinotomies, ensuring complete silicone oil filling for adequate tamponade, and argon retinopexy can lead to low complication rates and improved outcomes.

Investigation of a Novel Injectable Chitosan Oligosaccharide-Bovine Hydroxyapatite Hybrid Dental Biocomposite for the Purposes of Conservative Pulp Therapy.

This study aimed to develop injectable chitosan oligosaccharide (COS) and bovine hydroxyapatite (BHA) hybrid biocomposites, and characterise their physiochemical properties for use as a dental pulp-capping material. The COS powder was prepared from chitosan through hydrolytic reactions and then dissolved in 0.2% acetic acid to create a solution. BHA was obtained from waste bovine bone and milled to form a powder. The BHA powder was incorporated with the COS solution at different proportions to create the COS-BHA hybrid biocomposite. Zirconium oxide (ZrO2) powder was included in the blend as a radiopacifier. The composite was characterised to evaluate its physiochemical properties, radiopacity, setting time, solubility, and pH. Fourier-transform infrared spectroscopic analysis of the COS-BHA biocomposite shows the characteristic peaks of COS and hydroxyapatite. Compositional analysis via ICP-MS and SEM-EDX shows the predominant elements present to be the constituents of COS, BHA, and ZrO2. The hybrid biocomposite demonstrated an average setting time of 1 h and 10 min and a pH value of 10. The biocomposite demonstrated solubility when placed in a physiological solution. Radiographically, the set hybrid biocomposite appears to be more radiopaque than the commercial mineral trioxide aggregate (MTA). The developed COS-BHA hybrid biocomposite demonstrated good potential as a pulp-capping agent exhibiting high pH, with a greater radiopacity and reduced setting time compared to MTA. Solubility of the biocomposite may be addressed in future studies with the incorporation of a cross-linking agent. However, further in vitro and in vivo studies are necessary to evaluate its clinical feasibility.

Engineering and polymeric composition of drug-eluting suture: A review.

Sutures are the most popular surgical implants in the global surgical equipment market. They are used for holding tissues together to achieve wound closure. However, controlling the body's immune response to these "foreign bodies" at site of infection is challenging. Natural polymers such as collagen, silk, nylon, and cotton, and synthetic polymers such as polycaprolactone, poly(lactic-co-glycolic acid), poly(p-dioxanone) and so forth, contribute the robust foundation for the engineering of drug-eluting sutures. The incorporation of active pharmaceutical ingredients (APIs) with polymeric composition of suture materials is an efficient way to reduce inflammatory reaction in the wound site as well as to control bacterial growth, while allowing wound healing. The incorporation of polymeric composition in surgical sutures has been found to add high flexibility as well as excellent physical and mechanical properties. Fabrication processes and polymer materials allow control over drug-eluting profiles to effectively address wound healing requirements. This review outlines and discusses (a) polymer materials and APIs used in suture applications, including absorbable and nonabsorbable sutures; (b) suture structures, such as monofilament, multifilament, barded and smart sutures; and (c) the existing manufacturing techniques for drug-eluting suture production, including electrospinning, melt-extrusion and coating.

Development of an Organic-Inorganic Nanostructured Hybrid Dental Biocomposite.

Dental pathologies such as caries is one of the most prevalent diseases worldwide. Dental pulp contains stem cells capable of regenerating the dentine in the tooth, consequently, healthy dental pulp is essential for long term tooth survival. The aim of this study was to incorporate a variety of polymers that provide strength, an antibacterial substance and a protein-based polymer to provide cell support. These components were combined into a triphasic hybrid dental biocomposite (3HB), that together could provide regenerative properties for the pulp tissue. The 3HB biocomposite was incorporated into Organic-inorganic nanostructured materials such as Mineral Trioxide Aggregate (MTA) as a base to assemble a hybrid dental biocomposite. The effects of the 3HB on cytotoxicity was examined in mouse dental pulp cells, MDPC-23. In vitro studies showed that 3HB supported the proliferative growth of the cells significantly more than the no treatment control. 3HB also caused little stress to the cells and supported cell viability. Fourier transform infrared (FTIR) spectra confirmed the presence of polymer functional groups within the 3HB biocomposite. Therefore, 3HB compound has the potential to be applied as a pulp wound dressing providing superior cytocompatibility than the present options but also may be indispensable for the regeneration of dental pulp.

In-vitro degradation and toxicological assessment of pulsed electric fields crosslinked zein-chitosan-poly(vinyl alcohol) biopolymeric films.

We investigated the in vitro degradation and cytotoxic effects of edible films developed from pulsed electric fields (PEF) treated zein-chitosan-poly(vinyl alcohol) dispersions at specific energy 60-70, 385-400, and 620-650 kJ/kg. The degradation was evaluated using both simulated gastro-intestinal electrolyte solutions (SGES) and enzyme hydrolysis. The results of ortho-phthaldialdehyde (OPA) test indicated that the chemical breakdown of the films in SGES and enzyme increased with degradation time, but the product's features were unmodified. The Fourier Transform Infrared spectroscopy (FTIR) data showed enhancement of zein and chitosan transformation from ordered helices to ß-sheet conformation. Relative cell survival rates of Hepa-1c1c7 cells investigated using 3-[4,5- dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) showed that the survival remained higher than 70% in both the supernatant and the residue of the SGES degraded samples and the supernatant from enzyme hydrolysis, which suggested that there was no significant toxicity of the films in the tested system. Although the residue from pancreatic digestion (240 min) (i.e. undigested films and a cocktail of digestion enzymes) expressed cytotoxicity activity, there was limited evidence of direct toxicity of the films. The findings of the study demonstrate the potential for PEF modified zein-chitosan-poly(vinyl alcohol) films as value-added biomaterials for the application in edible food packaging.

Melt-electrowriting with novel milk protein/PCL biomaterials for skin regeneration.

Demand for skin replacements is rapidly increasing as burn and full-thickness wounds are difficult to repair due to the low regeneration capability of innate tissues, as well as the physical drawbacks associated with currently available substitutes. To address this need, an emerging 3D printing technique, melt-electrowriting (MEW) was used to create novel bioactive scaffolds to promote skin regeneration. Polycaprolactone (PCL), a bioresorbable and biocompatible, synthetic polymer with Food and Drug Administration approval for use in the human body was selected as scaffold material due to its mechanical stability, flexibility, and superior melt processing properties. In order to increase PCL's biological functionality bioactive milk proteins (MPs) were blended with PCL. To date, this is the first study of its kind detailing the tissue regenerative capacity of PCL containing MPs as bioactive additives for skin regeneration using MEW. The aim of this study was to MEW MP/PCL tissue engineered constructs (TEC) and assess their suitability for generating tissue in vitro. The MPs, lactoferrin (LF) and whey protein (WP), were mixed with PCL individually at varying concentrations (0.05%, 0.1%, 0.25%), and in combination (COMB) at concentrations of 0.25% each. TECs were characterised chemically, physically, and their biological activity assessed in vitro. Physical characterisation of MEW MP/PCL scaffolds showed that reproducible, layered micron range scaffolds could be fabricated; displaying high porosity, low degradation, and rapid protein release. Biological activity, determined via an in vitro skin model using human keratinocytes (HaCaTs) and normal human dermal fibroblasts cells, showed significantly increased cell growth, spreading, and infiltration into LF (0.25%) containing scaffolds and COMB scaffolds when compared to PCL alone (p ≤ 0.05). These findings demonstrated that the combined addition of LF and WP increased the biological activity of MEW PCL scaffolds and could be potentially used as a TEC for deep tissue dermal regeneration.

Osteoconduction in keratin-hydroxyapatite composite bone-graft substitutes.

Reconstituted keratin-hydroxyapatite (K-HA) composites have shown potential as nonload-bearing bone graft substitute material. This in vivo study investigated the bone regeneration response of keratin plus 40% HA composite materials in comparison to collagen counterparts and an unfilled defect site. The implantation site was a noncritical size defect created in the long bones (tibia) of sheep, with observations made at 1, 2, 4, 6, 8, and 12 weeks postimplantation. Porous K-HA materials displayed an excellent biocompatibility similar to collagen counterparts; however, the rate of bone regeneration at K-HA implantation sites was markedly slower than that of the collagen or unfilled defect sites. While collagen materials were undetectable by 4 weeks implantation, K-HA composite remnants were present at 12 weeks. However, there is evidence that K-HA implants participated in the natural remodelling process of bone, with bone regeneration occurring via a creeping substitution mechanism. Observations imply that the rate of bone ingrowth into the K-HA defect site was matched with the rate of K-HA resorption. These results suggest that K-HA materials may offer significant benefits as nonload-bearing bone graft substitutes where it is desirable that the degradation of the scaffolding material be well matched with the rate of bone regeneration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2034-2044, 2017.

A novel squid pen chitosan/hydroxyapatite/ß-tricalcium phosphate composite for bone tissue engineering.

Squid pen chitosan was used in the fabrication of biocomposite scaffolds for bone tissue engineering. Hydroxyapatite (HA) and beta-tricalcium phosphate (ß-TCP) obtained from waste mussel shells were used as the calcium phosphate source. The composite was prepared using 2.5% tripolyphosphate (TPP) and 1% glycerol as a cross-linker and plasticizer, respectively. The weight percent (wt.%) ratios of the ceramic components in the composite were 20/10/70, 30/20/50 and 40/30/30 (HA/ß-TCP/Chi). The biodegradation rate and structural properties of the scaffolds were investigated. Scanning electron microscopy (SEM) and microCT(µCT) results indicated that the composites have a well defined lamellar structure with an average pore size of 200 µm. The porosity of the composites decreased from 88 to 56% by increasing the ratio of HA/ß-TCP from 30 to 70%. After 28 days of incubation in a physiological solution, the scaffolds were degraded by approximately 30%. In vitro investigations showed that the composites were cytocompatible and supported the growth of L929 and Saos-2 cells. The obtained data suggests that the squid pen chitosan composites are potential candidates for bone regeneration.