The Clinical Feasibility of Newly Developed Thin Flat-Type Bioresorbable Osteosynthesis Devices for the Internal Fixation of Zygomatic Fractures: Is There a Difference in Healing Between Bioresorbable Materials and Titanium Osteosynthesis?

Characterization of 3D printed biodegradable piezoelectric scaffolds for bone regeneration

OBJECTIVE

The primary objective of this research was to develop a poly(l-lactic acid) (PLLA) scaffold and evaluate critical characteristics essential for its biologic use as a craniofacial implant.

MATERIALS AND METHODS

PLLA scaffolds were designed and fabricated using fused deposition modeling technology. The surface morphology and microarchitecture were analyzed using scanning electron microscopy (SEM) and microCT, respectively. Crystallography, compressive modulus, and the piezoelectric potential generated upon mechanical distortion were characterized. Hydrolytic degradation was studied. MG63 osteoblast-like cell proliferation and morphology were assessed.

RESULTS

The porosity of the scaffolds was 73%, with an average pore size of 450 µm and an average scaffold fiber thickness of 130 µm. The average compressive modulus was 244 MPa, and the scaffolds generated an electric potential of 25 mV upon cyclic/repeated loading. The crystallinity reduced from 27.5% to 13.9% during the 3D printing process. The hydrolytic degradation was minimal during a 12-week period. Osteoblast-like cells did not attach to the uncoated scaffold but attached well after coating the scaffold with fibrinogen. They then proliferated to cover the complete scaffold by Day 14.

CONCLUSION

The PLLA scaffolds were designed and printed, proving the feasibility of 3D printing as a method of fabricating PLLA scaffolds. The elastic modulus was comparable to that of trabecular bone, and the piezoelectric properties of the PLLA were retained after 3D printing. The scaffolds were cytocompatible. These 3D-printed PLLA scaffolds showed promising properties akin to the natural bone, and they warrant further investigation for bone regeneration.

A novel biomimetic trabecular bone metal plate for bone repair and osseointegration

Fracture is one of the most common traumatic diseases in clinical practice, and metal plates have always been the first choice for fracture treatment because of their high strength. However, the bone plates have high elastic modulus and do not match the biomechanics of human bone, which adversely affects callus formation and fracture healing. Moreover, the complex microenvironment in the human body can induce corrosion of metallic materials and release toxic ions, which reduces the biocompatibility of the bone plate, and may necessitate surgical removal of the implant. In this study, tantalum (Ta) was deposited on porous silicon carbide (SiC) scaffolds by chemical vapor deposition technology to prepare a novel porous tantalum (pTa) trabecular bone metal plate. The function of the novel bone plate was evaluated by implantation in an animal fracture model. The results showed that the novel bone plate was effective in fracture fixation, without breakage. Both X-ray and microcomputed tomography analysis showed indirect healing by both pTa trabecular bone metal plates and titanium (Ti) plates; however, elastic fixation and obvious callus formation were observed after fixation with pTa trabecular bone metal plates, indicating better bone repair. Histology showed that pTa promoted the formation of new bone and integrated well with the host bone. Therefore, this novel pTa trabecular bone metal plate has good prospects for application in treating fractures.

Biocompatible Materials in Otorhinolaryngology and Their Antibacterial Properties

For decades, biomaterials have been commonly used in medicine for the replacement of human body tissue, precise drug-delivery systems, or as parts of medical devices that are essential for some treatment methods. Due to rapid progress in the field of new materials, updates on the state of knowledge about biomaterials are frequently needed. This article describes the clinical application of different types of biomaterials in the field of otorhinolaryngology, i.e., head and neck surgery, focusing on their antimicrobial properties. The variety of their applications includes cochlear implants, middle ear prostheses, voice prostheses, materials for osteosynthesis, and nasal packing after nasal/paranasal sinuses surgery. Ceramics, such as as hydroxyapatite, zirconia, or metals and metal alloys, still have applications in the head and neck region. Tissue engineering scaffolds and drug-eluting materials, such as polymers and polymer-based composites, are becoming more common. The restoration of life tissue and the ability to prevent microbial colonization should be taken into consideration when designing the materials to be used for implant production. The authors of this paper have reviewed publications available in PubMed from the last five years about the recent progress in this topic but also establish the state of knowledge of the most common application of biomaterials over the last few decades.

In Silico Biomechanical Evaluation of WE43 Magnesium Plates for Mandibular Fracture Fixation

Titanium fixation devices are the gold standard for the treatment of mandibular fractures; however, they present serious limitations, such as non-degradability and generation of imaging artifacts. As an alternative, biodegradable magnesium alloys have lately drawn attention due to their biodegradability and biocompatibility. In addition, magnesium alloys offer a relatively high modulus of elasticity in comparison to biodegradable polymers, being a potential option to substitute titanium in highly loaded anatomical areas, such as the mandible. This study aimed to evaluate the biomechanical competence of magnesium alloy WE43 plates for mandibular fracture fixation in comparison to the clinical standard or even softer polymer solutions. A 3D finite element model of the human mandible was developed, and four different fracture scenarios were simulated, together with physiological post-operative loading and boundary conditions. In a systematic comparison, the material properties of titanium alloy Ti-6Al-4V, magnesium alloy WE43, and polylactic acid (PLA) were assigned to the fixation devices, and two different plate thicknesses were tested. No failure was predicted in the fixation devices for any of the tested materials. Moreover, the magnesium and titanium fixation devices induced a similar amount of strain within the healing regions. On the other hand, the PLA devices led to higher mechanical strains within the healing region. Plate thickness only slightly influenced the primary fixation stability. Therefore, magnesium alloy WE43 fixation devices seem to provide a suitable biomechanical environment to support mandibular fracture healing in the early stages of bone healing. Magnesium WE43 showed a biomechanical performance similar to clinically used titanium devices with the added advantages of biodegradability and radiopacity, and at the same time it showed a remarkably higher primary stability compared to PLA fixation devices, which appear to be too unstable, especially in the posterior and more loaded mandibular fracture cases.

A Narrative Review of u-HA/PLLA, a Bioactive Resorbable Reconstruction Material: Applications in Oral and Maxillofacial Surgery

The advent of bioresorbable materials to overcome limitations and replace traditional bone-reconstruction titanium-plate systems for bone fixation, thus achieving greater efficiency and safety in medical and dental applications, has ushered in a new era in biomaterial development. Because of its bioactive osteoconductive ability and biocompatibility, the forged composite of uncalcined/unsintered hydroxyapatite and poly L-lactic acid (u-HA/PLLA) has attracted considerable interest from researchers in bone tissue engineering, as well as from clinicians, particularly for applications in maxillofacial reconstructive surgery. Thus, various in vitro studies, in vivo studies, and clinical trials have been conducted to investigate the feasibility and weaknesses of this biomaterial in oral and maxillofacial surgery. Various technical improvements have been proposed to optimize its advantages and limit its disadvantages. This narrative review presents an up-to-date, comprehensive review of u-HA/PLLA, a bioactive osteoconductive and bioresorbable bone-reconstruction and -fixation material, in the context of oral and maxillofacial surgery, notably maxillofacial trauma, orthognathic surgery, and maxillofacial reconstruction. It simultaneously introduces new trends in the development of bioresorbable materials that could used in this field. Various studies have shown the superiority of u-HA/PLLA, a third-generation bioresorbable biomaterial with high mechanical strength, biocompatibility, and bioactive osteoconductivity, compared to other bioresorbable materials. Future developments may focus on controlling its bioactivity and biodegradation rate and enhancing its mechanical strength.

Complications of Poly-l-Lactic Acid and Polyglycolic Acid (PLLA/PGA) Osteosynthesis Systems for Maxillofacial Surgery: A Retrospective Clinical Investigation

Two second-generation PLLA/PGA bioresorbable osteosynthetic plate systems for oral and maxillofacial surgery are available in Japan. The two systems have different PLLA-PGA component ratios (RapidSorb^®, 85:15; Lactosorb^®, 82:18) and plate and screw shapes. We conducted a retrospective study to compare our clinical evaluation and examine the incidence of postoperative complications between the two plate systems. A retrospective survey was conducted in 148 patients (midfacial fracture/trauma (68.2%) and dentofacial deformity patients (31.8%); males (54.7%); median age, 37.5 years) treated using maxillofacial osteosynthetic plate systems. The complications included plate exposure (7.4%), infection, (2.7%), and plate breakage (0.7%). Multivariate logistic regression analysis showed a significant correlation between sex (female), plate system (Lactosorb^®), number of plates, and pyriform aperture and periorbital sites of plate placement (p < 0.05). Additionally, the propensity score-adjusted model showed a significant correlation between Lactosorb^® and postoperative complications (odds ratio 1.007 (95% confidence interval, 1.001–1.055), p < 0.01). However, the two plate systems showed a low incidence rate of complications, and the plate integration and survivability were similar using 2.0-mm or 1.5-mm resorbable plate regardless of the plate system. Our findings suggest that female sex and a greater number of plates are risk factors for postoperative complications, whereas pyriform aperture and periorbital plate placements reduce the risk.

Feasibility of Application of the Newly Developed Nano-Biomaterial, β-TCP/PDLLA, in Maxillofacial Reconstructive Surgery: A Pilot Rat Study

This study was performed to examine the applicability of the newly developed nano-biocomposite, β-tricalcium phosphate (β-TCP)/u-HA/poly-d/l-lactide (PDLLA), to bone defects in the oral and maxillofacial area. This novel nano-biocomposite showed several advantages, including biocompatibility, biodegradability, and osteoconductivity. In addition, its optimal plasticity also allowed its utilization in irregular critical bone defect reconstructive surgery. Here, three different nano-biomaterials, i.e., β-TCP/PDLLA, β-TCP, and PDLLA, were implanted into critical bone defects in the right lateral mandible of 10-week-old Sprague–Dawley (SD) rats as bone graft substitutes. Micro-computed tomography (Micro-CT) and immunohistochemical staining for the osteogenesis biomarkers, Runx2, osteocalcin, and the leptin receptor, were performed to investigate and compare bone regeneration between the groups. Although the micro-CT results showed the highest bone mineral density (BMD) and bone volume to total volume (BV/TV) with β-TCP, immunohistochemical analysis indicated better osteogenesis-promoting ability of β-TCP/PDLLA, especially at an early stage of the bone healing process. These results confirmed that the novel nano-biocomposite, β-TCP/PDLLA, which has excellent biocompatibility, bioresorbability and bioactive/osteoconductivity, has the potential to become a next-generation biomaterial for use as a bone graft substitute in maxillofacial reconstructive surgery.

Comparison between resorbable plates vs. titanium plates for treatment of zygomatic fractures: a systematic review with meta-analysis

PURPOSE

To compare resorbable plates with titanium plates for the fixation of zygomatic fractures, taking into account postoperative complications.

METHODS

This systematic review followed the guidelines of PRISMA and the recommendations of the Cochrane Handbook and was registered in PROSPERO. The electronic search was performed in the Web of Science, PubMed, Virtual Health Library, and Cochrane Library databases and in the gray literature. The study selection and the data extraction were performed by three calibrated and independent researchers. The assessment of the risk of bias in the studies was performed using the Cochrane Risk of Bias Tool for clinical trials. Meta-analyses were performed using Review Manager Software version 5.3, using the Peto's Odds Ratios (PORs), and when I² > 30, the random effect model was used. The evaluation of the quality of the evidence was carried out through GRADE.

RESULTS

A total of 2651 studies were screened and only nine were included; 7 of which were used for quantitative assessment. The follow-up time for patients ranged from 6 months to 5 years. All studies showed a low risk of bias in the "incomplete outcome data" domain. The need for plate removal (POR: 0.11, 95% CI: 0.02 to 0.81, I² = 0%) and dehiscence (POR 0.12, 95% CI 0.02 to 0.63, I² = not applied) was lower for the group of patients who used resorbable plates than for titanium plates.

CONCLUSION

There was no difference in the occurrence of infection, diplopia, or paresthesia between the fixation methods. Resorbable plates showed better postoperative clinical performance.

Biocompatibility and Physico-Chemical Properties of Highly Porous PLA/HA Scaffolds for Bone Reconstruction

The major problem in bone tissue engineering is the development of scaffolds which can simultaneously meet the requirements of porous structure, as well as have the ability to guide the regeneration of damaged tissue by biological fixation. Composites containing biodegradable matrix and bioactive filler are the new hope in this research field. Herein we employed a simple and facile solvent casting particulate-leaching method for producing polylactide acid/hydroxyapatite (PLA/HA) composites at room temperature. FT-IR analysis confirmed the existence of necessary functional groups associated with the PLA/HA composite, whereas energy-dispersive X-ray (EDX) spectra indicated the uniform distribution of hydroxyapatite particles in the polymer matrix. The beehive-like surface morphology of the composites revealed the presence of macropores, ranged from 300 to 400 μm, whereas the thickness of the pores was noticed to be 1-2 μm. The total porosity of the scaffolds, calculated by hydrostatic weighing, was found to be 79%. The water contact angle of pure PLA was decreased from 83.6 ± 1.91° to 62.4 ± 4.17° due to the addition of hydroxyapatite in the polymer matrix. Thus, the wettability of the polymeric biomaterial could be increased by preparing their composites with hydroxyapatite. The adhesion of multipotent mesenchymal stromal cells over the surface of PLA/HA scaffolds was 3.2 times (p = 0.03) higher than the pure PLA sample. Subcutaneous implantation in mice demonstrated a good tolerance of all tested porous scaffolds and widespread ingrowth of tissue into the implant pores. HA-containing scaffolds showed a less pronounced inflammatory response after two weeks of implantation compared to pure PLA. These observations suggest that PLA/HA composites have enormous potential for hard tissue engineering and restoring maxillofacial defects.

Efficacy of bioresorbable plates in the osteosynthesis of linear mandibular fractures

Background and Objectives:

There are limited evidences available about the performance of biodegradable system in the treatment of linear mandibular fractures without the aid of postoperative maxillomandibular fixation (MMF). Hence, the present study was planned to evaluate the treatment outcomes in mandibular fractures, using 2.5 mm bioresorbable plates and screws without postoperative MMF.

Methodology:

This cohort study compares both prospective and retrospective data. The prospective study treated 20 adult patients with linear mandibular fracture using bioresorbable plates and screws, without using postoperative MMF (Group 1). Retrospective data were collected from a previous published study in which patients were treated with bioresorbable plates and screws with 2 weeks postoperative MMF (Group 2) and those treated with metal plates and screws without postoperative MMF (Group 3). Group 1 patients were followed up at 2 and 4 months to evaluate the functional outcomes in terms of fracture mobility, malocclusion, pain, and soft-tissue deformity and compared with its preoperative findings. Further, the treatment outcomes of Group 1, Group 2, and Group 3 were compared among themselves at 2-month follow-up.

Results:

Group 1 patients showed a significant improvement in the treatment outcomes at 2 and 4-month follow-up. In addition, when 2 months postoperative outcomes were compared among the three groups, no statistically significant difference was observed in the treatment outcomes.

Conclusion:

Endpoint osteosynthesis can be achieved with the bioresorbable fixation system when used in the treatment of un-displaced linear mandibular fractures, without postoperative MMF. A minor modification of using a lower size osteotomy drill can prevent screw loosening.

Biomechanical Loading Comparison between Titanium and Bioactive Resorbable Screw Systems for Fixation of Intracapsular Condylar Head Fractures

Osteosynthesis resorbable materials made of uncalcined and unsintered hydroxyapatite (u-HA) particles, poly-L-lactide (PLLA), are bioresorbable, and these materials have feasible bioactive/osteoconductive capacities. However, their strength and stability for fixation in mandibular condylar head fractures remain unclear. This in vitro study aimed to assess the biomechanical strength of u-HA/PLLA screws after the internal fixation of condylar head fractures. To evaluate their biomechanical behavior, 32 hemimandible replicas were divided into eight groups, each consisting of single-screw and double-screw fixations with titanium or u-HA/PLLA screws. A linear load was applied as vertical and horizontal load to each group to simulate the muscular forces in condylar head fractures. Samples were examined for 0.5, 1, 2, and 3-mm displacement loads. Two screws were needed for stable fixation of the mandibular condylar head fracture during biomechanical evaluation. After screw fixation for condylar head fractures, the titanium screws model was slightly more resistant to vertical and horizontal movement with a load for a small displacement than the u-HA/PLLA screws model. There was no statistically significant difference with load for large displacements. The u-HA/PLLA screw has a low mechanical resistance under small displacement loading compared with titanium within the limits of the mandibular head fracture model study.

Biomechanical Loading Comparison between Titanium and Unsintered Hydroxyapatite/Poly-L-Lactide Plate System for Fixation of Mandibular Subcondylar Fractures

Osteosynthesis absorbable materials made of uncalcined and unsintered hydroxyapatite (u-HA) particles, poly-l-lactide (PLLA), and u-HA/PLLA are bioresorbable, and these plate systems have feasible bioactive osteoconductive capacities. However, their strength and stability for fixation in mandibular subcondylar fractures remain unclear. This in vitro study aimed to assess the biomechanical strength of u-HA/PLLA bioresorbable plate systems after internal fixation of mandibular subcondylar fractures. Tensile and shear strength were measured for each u-HA/PLLA and titanium plate system. To evaluate biomechanical behavior, 20 hemimandible replicas were divided into 10 groups, each comprising a titanium plate and a bioresorbable plate. A linear load was applied anteroposteriorly and lateromedially to each group to simulate the muscular forces in mandibular condylar fractures. All samples were analyzed for each displacement load and the displacement obtained by the maximum load. Tensile and shear strength of the u-HA/PLLA plate were each approximately 45% of those of the titanium plates. Mechanical resistance was worst in the u-HA/PLLA plate initially loaded anteroposteriorly. Titanium plates showed the best mechanical resistance during lateromedial loading. Notably, both plates showed similar resistance when a lateromedially load was applied. In the biomechanical evaluation of mandibular condylar fracture treatment, the u-HA/PLLA plates had sufficiently high resistance in the two-plate fixation method.

Feasible Advantage of Bioactive/Bioresorbable Devices Made of Forged Composites of Hydroxyapatite Particles and Poly-L-lactide in Alveolar Bone Augmentation: A Preliminary Study

Purpose: We aimed to document the clinical usefulness of uncalcined and unsintered hydroxyapatite (u-HA) particles and poly-L-lactide (PLLA) composite materials and their advantageous properties. Methods: Between April 2016 and March 2018, five patients required anterior maxillary alveolar ridge augmentation using fixation with u-HA/PLLA screws for an onlay block bone graft harvested from the mandibular ramus at our institute. Bone biopsies were obtained from the dental implantation site following bone healing for histomorphometric and immunohistochemical (IHC) measurements. Results: Many stromal cells were positive for Osterix, RUNX2, and SOX9 but were negative for CD68. On cell counting, based on IHC staining for Osterix, RUNX2, SOX9 and CD68 from peripheral u-HA/PLLA screw or bone areas, both areas consistently showed no significant difference in terms of Osterix, RUNX2, and SOX9. Hematoxylin-eosin staining revealed direct bone connection to the biomaterials, and no inflammatory cells infiltrated the areas surrounding the bone or artificial material. Area between the bone and u-HA/PLLA screw was seamless with no boundary. Round small cells and immature fibroblasts were noted. The new bone showed the presence of bone lamellae, normal osteocytes, and osteoblasts. Conclusion: The u-HA/PLLA materials showed excellent biodegradability and bioactive osteoconductivity. In addition, this material induced no apparent inflammatory or foreign body reactions following implantation, and it directly bonded to the human bone. Therefore, this u-HA/PLLA material seems ideal and most suitable for use as a substitute for osteosynthesis.

Overview of innovative advances in bioresorbable plate systems for oral and maxillofacial surgery

Maxillofacial osteosynthetic surgeries require stable fixation for uneventful boney healing and optimal remodeling. Although conventional titanium plates and screws for osteofixation are considered the gold standard for rigid fixation in maxillofacial surgeries, bioresorbable implants of plates and screw systems are commonly used for various maxillofacial osteosynthetic surgeries such as orthognathic surgery, maxillofacial fractures, and reconstructive surgery. Titanium plates are limited by their palpability, mutagenic effects, and interference with imaging, which may lead to the need for subsequent removal; the use of a biologically resorbable osteofixation system could potentially address these limitations. However, several problems remain including fundamental issues involving decreased mechanical strength and stability, slow biodegradation, complex procedures, and the available bioresorbable implant materials. Major advances in bioresorbable plate systems have been made with the use of bioactive/resorbable osteoconductive materials and an accelerator of bioresorption, such as polyglycolic acid. This report presents an overview of currently available resorbable implant materials and their applications, with a focus on recent innovative advances and new developments in this field.

Complications of a poly-L-lactic acid and polyglycolic acid osteosynthesis device for internal fixation in maxillofacial surgery

The purpose of this study was to retrospectively evaluate and examine the incidence of complications using poly-L-lactic acid and polyglycolic acid (PLLA/PGA) copolymer plate system in maxillofacial osteosynthesis. The retrospective study included 87 patients (50 men, 37 women), who needed maxillofacial surgery. We examined the proportion of complications and their factors from clinical data. A comparison was also made for plate decomposition using the molecular weight of the plate without plate exposure and complications. Osteosynthesis sites healed in all patients. Ten cases (11.5%) showed plate exposure-related complications, with all occurring at intraoral surgical sites. There was no significant difference in molecular weight changes of plates in resorbable process. Statistical analysis of study variables between patients with and without exposed plates showed that the plate thickness was significantly associated with the risk of exposed plates (p < 0.05). The commercially available PLLA/PGA device could be a useful rapid resorbable material for maxillofacial osteosynthesis. When thick plates are used on the intraoral site, it may be necessary to pay attention to the complication of plate exposure. Even if exposure-related complications have occurred, resorption and degradation of this material proceeds, suggesting the ease of appropriate risk management.