Maxillofacial Reconstruction With Three Dimensional Resin Bone Substitutes as an Alternative to Transition Group of Metals: A Structured Review

In recent years, novel technologies and techniques have allowed today the production of controlled architecture materials. Although autogenous bone graft substitutes remain the gold standard, enormous defects require supplementary alloplastic substitutes for reconstruction. Polymers have lately been explored for the same purpose and their biological performance has been under research since the last decade. The aim of this review is to analyse maxillofacial reconstruction with three-dimensional resin bone substitutes. A Problem Intervention Comparison Outcomes (PICO) analysis was done and a search was carried out in the Cochrane Database, PubMed, Google Scholar etc databases and a hand search was done to collect the related literature. All articles for maxillofacial reconstruction with three-dimensional resin bone substitutes were scrutinised. The manuscripts published from 1990 till May 2021, were included in this review. A total of 106 articles were obtained from a PICO-based keyword search, and 91 manuscripts were retrieved after excluding the duplicates. Out of these 57 manuscripts were excluded on the basis of title and abstract. From the remaining 34 studies, 17 were excluded after reading the full text based on the inclusion and exclusion criteria. During data extraction, four studies were removed and finally, 13 studies were included in this research. From this scoping review, we could conclude that polymethylmethacrylate and polylactic acid formulations are very promising resin bone substitutes for 3-dimensional reconstruction of maxillofacial defects. However, rigorous long-term clinical trials are needed to validate this conclusion.

Radiographic evaluation of a novel bone adhesive for maintenance of crestal bone around implants in canine oversized osteotomies

BACKGROUND

A novel bone adhesive (tetracalcium phosphate and O-phospho-L-serine) has been developed as an osteoconductive, biodegradable bone-adherent material. The purpose of this study was to evaluate the maintenance of crestal bone/material level by standardized radiographs.

METHODS

This was a randomized, controlled, three arm, prospective study. Twenty-six mixed breed hound dogs were included in this study. Three implants were placed on either side of the mandible with either bone adhesive (BA), bovine bone mineral (BBM), or no biomaterial (negative control [NC]). Standardized periapical radiographs were taken immediately after implant placement and at every month up to 1 year. The vertical distance between the implant platform to the first radiopaque material on both the mesial and distal surfaces were measured and crestal bone/material level changes were analyzed.

RESULTS

The crestal bone/material level adjacent to BA was stable and maintained throughout the study. There were statistically significant differences found between BA and NC in terms of maintenance of crestal bone levels at any given timepoint.

CONCLUSION

This study demonstrated that BA maintained crestal bone levels and had a similar ability to maintain that level over 1 year compared with BBM.

Evaluation of biocompatibility, osteointegration and biomechanical properties of the new Calcemex® cement: An <em>in vivo</em> study

The mixture of polymethylmethacrylate (PMMA) and β-tricalciumphospate (β-TCP) is the most widely used bone graft. Common features of bone cement are the biocompatibility, bioactivity, mechanical stability and ability to fuse with the host's bone tissue. However, there are still few studies that have evaluated these characteristics in vivo. Our study aims to acquire these parameters, using an animal model with functional characteristics similar to those of humans. The analyzed cement is Calcemex^®, evaluated both in compact and fluid formulation. The chosen animal models were 5 pigs, treated with femoral and tibial implants of Calcemex^® samples. After one year, the pigs were sacrificed and the specimens explanted for morphological, histological, ultrastructural and mechanical evaluations. For both formulations, the investigation highlighted the absence of foreign body reactions in the host, the histological integration with the surrounding tissues and the preservation of mechanical compression resistance.

Reinforcement and Fatigue of a Bioinspired Mineral-Organic Bioresorbable Bone Adhesive

Bioresorbable bone adhesives may provide remarkable clinical solutions in areas ranging from fixation and osseointegration of permanent implants to the direct healing and fusion of bones without permanent fixation hardware. Mechanical properties of bone adhesives are critical for their successful application in vivo. Reinforcement of a tetracalcium phosphate-phosphoserine bone adhesive is investigated using three degradable reinforcement strategies: poly(lactic-co-glycolic) (PLGA) fibers, PLGA sutures, and chitosan lactate. All three approaches lead to higher compressive strengths of the material and better fatigue performance. Reinforcement with PLGA fibers and chitosan lactate results in a 100% probability of survival of samples at 20 MPa maximum compressive stress level, which is almost ten times higher compared to compressive loads observed in the intervertebral discs of the spine in vivo. High adhesive shear strength of 5.1 MPa is achieved for fiber-reinforced bone adhesive by tuning the surface architecture of titanium samples. Finally, biological and biomechanical performance of the fiber-reinforced adhesive is evaluated in a rabbit distal femur osteotomy model, showing the potential of the bone adhesive for clinical use.

Bioactive poly (methyl methacrylate) bone cement for the treatment of osteoporotic vertebral compression fractures

Rationale: Poly (methyl methacrylate) (PMMA) bone cement is one of the most commonly used biomaterials for augmenting/stabilizing osteoporosis-induced vertebral compression fractures (OVCFs), such as percutaneous vertebroplasty (PVP) and balloon kyphoplasty (BKP). However, its clinical applications are limited by its poor performance in high compressive modulus and weak bonding to bone. To address these issues, a bioactive composite bone cement was developed for the treatment of osteoporotic vertebral compression fractures, in which mineralized collagen (MC) was incorporated into the PMMA bone cement (MC-PMMA). Methods: The in vitro properties of PMMA and MC-PMMA composite bone cement were determined, including setting time, compressive modulus, adherence, proliferation, and osteogenic differentiation of rat bone mesenchymal stem cells. The in vivo properties of both cements were evaluated in an animal study (36 osteoporotic New Zealand female rabbits divided equally between the two bone cement groups; PVP at L5) and a small-scale and short-term clinical study (12 patients in each of the two bone cement groups; follow-up: 2 years). Results: In terms of value for PMMA bone cement, the handling properties of MC-PMMA bone cement were not significantly different. However, both compressive strength and compressive modulus were found to be significantly lower. In the rabbit model study, at 8 and 12 weeks post-surgery, bone regeneration was more significant in MC-PMMA bone cement (cortical bone thickness, osteoblast area, new bone area, and bone ingrowth %; each significantly higher). In the clinical study, at a follow-up of 2 years, both the Visual Analogue Score and Oswestry Disability Index were significantly reduced when MC-PMMA cement was used. Conclusions: MC-PMMA bone cement demonstrated good adaptive mechanical properties and biocompatibility and may be a promising alternative to commercial PMMA bone cements for the treatment of osteoporotic vertebral fractures in clinical settings. While the present results for MC-PMMA bone cement are encouraging, further study of this cement is needed to explore its viability as an ideal alternative for use in PVP and BKP.

Poly(propylene fumarate)-based materials: Synthesis, functionalization, properties, device fabrication and biomedical applications

Poly(propylene fumarate) (PPF) is a biodegradable polymer that has been investigated extensively over the last three decades. It has led many scientists to synthesize and fabricate a variety of PPF-based materials for biomedical applications due to its controllable mechanical properties, tunable degradation and biocompatibility. This review provides a comprehensive overview of the progress made in improving PPF synthesis, resin formulation, crosslinking, device fabrication and post polymerization modification. Further, we highlight the influence of these parameters on biodegradation, biocompatibility, and their use in a number of regenerative medicine applications, especially bone tissue engineering. In particular, the use of 3D printing techniques for the fabrication of PPF-based scaffolds is extensively reviewed. The recent invention of a ring-opening polymerization method affords precise control of PPF molecular mass, molecular mass distribution (Ɖ_M) and viscosity. Low Ɖ_M facilitates time-certain resorption of 3D printed structures. Novel post-polymerization and post-printing functionalization methods have accelerated the expansion of biomedical applications that utilize PPF-based materials. Finally, we shed light on evolving uses of PPF-based materials for orthopedics/bone tissue engineering and other biomedical applications, including its use as a hydrogel for bioprinting.

Bioinspired Mineral-Organic Bioresorbable Bone Adhesive

Bioresorbable bone adhesives have potential to revolutionize the clinical treatment of the human skeletal system, ranging from the fixation and osteointegration of permanent implants to the direct healing and fusion of bones without permanent fixation hardware. Despite an unmet need, there are currently no bone adhesives in clinical use that provide a strong enough bond to wet bone while possessing good osteointegration and bioresorbability. Inspired by the sandcastle worm that creates a protective tubular shell around its body using a proteinaceous adhesive, a novel bone adhesive is introduced, based on tetracalcium phosphate and phosphoserine, that cures in minutes in an aqueous environment and provides high bone-to-bone adhesive strength. The new material is measured to be 10 times more adhesive than bioresorbable calcium phosphate cement and 7.5 times more adhesive than non-resorbable poly(methyl methacrylate) bone cement, both of which are standard of care in the clinic today. The bone adhesive also demonstrates chemical adhesion to titanium approximately twice that of its adhesion to bone, unlocking the potential for adherence to metallic implants during surrounding bony incorporation. Finally, the bone adhesive is shown to demonstrate osteointegration and bioresorbability over a 52-week period in a critically sized distal femur defect in rabbits.

Functional Multichannel Poly(Propylene Fumarate)-Collagen Scaffold with Collagen-Binding Neurotrophic Factor 3 Promotes Neural Regeneration After Transected Spinal Cord Injury

Many factors contribute to the poor axonal regrowth and ineffective functional recovery after spinal cord injury (SCI). Biomaterials have been used for SCI repair by promoting bridge formation and reconnecting the neural tissue at the lesion site. The mechanical properties of biomaterials are critical for successful design to ensure the stable support as soon as possible when compressed by the surrounding spine and musculature. Poly(propylene fumarate) (PPF) scaffolds with high mechanical strength have been shown to provide firm spatial maintenance and to promote repair of tissue defects. A multichannel PPF scaffold is combined with collagen biomaterial to build a novel biocompatible delivery system coated with neurotrophin-3 containing an engineered collagen-binding domain (CBD-NT3). The parallel-aligned multichannel structure of PPF scaffolds guide the direction of neural tissue regeneration across the lesion site and promote reestablishment of bridge connectivity. The combinatorial treatment consisting of PPF and collagen loaded with CBD-NT3 improves the inhibitory microenvironment, facilitates axonal and neuronal regeneration, survival of various types of functional neurons and remyelination and synapse formation of regenerated axons following SCI. This novel treatment strategy for SCI repair effectively promotes neural tissue regeneration after transected spinal injury by providing a regrowth-supportive microenvironment and eventually induces functional improvement.

Investigations of silk fiber/calcium phosphate cement biocomposite for radial bone defect repair in rabbits

Background

This study aimed to investigate the effects of silk fiber (SF)/calcium phosphate cement (CPC) biocomposite on repairing radial bone defects in rabbits.

Methods

Four-month-old New Zealand rabbits were selected to create a bilateral radial bone defect model and divided into four groups according to implanted material: SF/CPC, SF/CPC/particulate bone (PB), PB, and control (C). The specimens were removed at four and eight postoperative weeks for general observation, X-ray examination, tissue slicing, scanning electron microscopy (SEM), and biomechanical testing.

Results

Postoperative X-ray showed no bone defect repair in group C and different degrees of bone defect repair in the other three groups. Imaging, histology, and SEM showed the following: group SF/CPC formed fine trabecular bone in week 4, while the maximum bending load in group SF/CPC in week 4 was significantly different from those in the other groups (P < 0.05).

Conclusions

SF/CPC has good biocompatibility and bone-inducing ability, demonstrating its bone defect-repairing ability.