Clinical orthodontic management during the COVID-19 pandemic

OBJECTIVES

To provide a comprehensive summary of the implications of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) on orthodontic treatment, contingency management, and provision of emergency orthodontic treatment, using currently available data and literature.

MATERIALS AND METHODS

Orthodontically relevant sources of information were searched using electronic databases including PubMed and Google Scholar and current reports from major health bodies such as Centers for Disease Control and Prevention, World Health Organization, National Institutes of Health, and major national orthodontic associations.

RESULTS

Where available, peer-reviewed and more recent publications were given priority. Due to the rapidly evolving nature of COVID-19 and limitations in quality of evidence, a narrative synthesis was undertaken. Relevant to orthodontics, human-to human transmission of SARS-CoV-2 occurs predominantly through the respiratory tract via droplets, secretions (cough, sneeze), and or direct contact, where the virus enters the mucous membrane of the mouth, nose, and eyes. The virus can remain stable for days on plastic and stainless steel. Most infected persons experience a mild form of disease, but those with advanced age or underlying comorbidities may suffer severe respiratory and multiorgan complications.

CONCLUSIONS

During the spread of the COVID-19 pandemic, elective orthodontic treatment should be suspended and resumed only when permitted by federal, provincial, and local health regulatory authorities. Emergency orthodontic treatment can be provided by following a contingency plan founded on effective communication and triage. Treatment advice should be delivered remotely first when possible, and where necessary, in-person treatment can be performed in a well-prepared operatory following the necessary precautions and infection prevention and control (IPAC) protocol.

Composition and characteristics of trabecular bone in osteoporosis and osteoarthritis

BACKGROUND

Bone strength depends on multiple factors such as bone density, architecture and composition turnover. However, the role these factors play in osteoporotic fractures is not well understood.

PURPOSE

The aim of this study was to analyze trabecular bone architecture, and its crystal and organic composition in humans, by comparing samples taken from patients who had a hip fracture (HF) and individuals with hip osteoarthritis (HOA).

METHODS

The study included 31 HF patients and 42 cases of HOA who underwent joint replacement surgery between 1/1/2013 and 31/12/2013. Trabecular bone samples were collected from the femoral heads and analyzed using a dual-energy X-ray absorptiometry, micro-CT, and solid-state high-resolution magic-angle-spinning nuclear magnetic resonance (MAS-NMR) spectroscopy.

RESULTS

No differences in proton or phosphorus concentration were found between the two groups using ¹H single pulse, ³¹P single pulse, ³¹P single pulse with proton decoupling NMR spectroscopy, in hydroxyapatite (HA) c-axis or a-axis crystal length. Bone volume fraction (BV/TV), trabecular number (Tb.N), and bone mineral density (BMD) were higher in the HO group than in the HF group [28.6% ± 10.5 vs 20.3% ± 6.6 (p = 0.026); 2.58 mm^-1 ± 1.57 vs 1.5 mm^-1 ± 0.79 (p = 0.005); and 0.39 g/cm² ± 0.10 vs. 0.28 g/cm² ± 0.05 (p = 0.002), respectively]. The trabecular separation (Tp.Sp) was lower in the HO group 0.42 mm ± 0.23 compared with the HF group 0.58 mm ± 0.27 (p = 0.036). In the HO group, BMD was correlated with BV/TV (r = 0.704, p < 0.001), BMC (r = 0.853, p < 0.001), Tb.N (r = 0.653, p < 0.001), Tb.Sp (-0.561, p < 0.001) and ¹H concentration (-0.580, p < 0.001) in the HO group. BMD was not correlated with BV/TV, Tb.Sp, Tb.Th, Tb.N, Tb.PF, ¹H concentration or HA crystal size in the HF group.

CONCLUSIONS

Patients with HO who did not sustain previous hip fractures had a higher femoral head BMD, BV/TV, and Tb.N than HF patients. In HO patients, BMD was positively correlated with the BV/TV and Tb.N and negatively correlated with the femoral head organic content and trabecular separation. Interestingly, these correlations were not found in HF patients with relatively lower bone densities. Therefore, osteoporotic patients with similar low bone densities could have significant microstructural differences. No differences were found between the two groups at a HA crystal level.

Improved bone regeneration using bone anabolic drug conjugates (C3 and C6) with deproteinized bovine bone mineral as a carrier in rat mandibular defects

BACKGROUND

Deproteinized bovine bone mineral (DBBM) has been extensively studied and used for bone regeneration in oral and maxillofacial surgery. However, it lacks an osteoinductive ability. We developed two novel bone anabolic conjugated drugs, known as C3 and C6, of an inactive bisphosphonate and a bone activating synthetic prostaglandin agonist. The aim was to investigate whether these drugs prebound to DBBM granules have the potential to achieve rapid and enhanced bone regeneration.

METHODS

Bilateral defects (4.3 mm diameter circular through and through) were created in mandibular angles of 24 Sprague-Dawley rats were filled with DBBM Control, DBBM with C3 or DBBM with C6 (n = 8 defects per group/ each timepoint). After 2 and 4 weeks, postmortem samples were analyzed by microcomputed tomography followed by backscattering electron microscopy and histology.

RESULTS

DBBM grafts containing the C3 and C6 conjugated drugs showed significantly more bone formation than DBBM control at 2 and 4 weeks. The C6 containing DBBM demonstrated the highest percentage of new bone formation at 4 weeks. There was no significant difference in the percentage of the remaining graft between the different groups at 2 or 4 weeks.

CONCLUSIONS

DBBM granules containing conjugated drugs C3 and C6 induced greater new bone volume generated and increased the bone formation rate more than the DBBM controls. This is expected to allow the development of clinical treatments that provide more predictable and improved bone regeneration for bone defect repair in oral and maxillofacial surgery.

Age related changes in the bone microstructure in patients with femoral neck fractures

BACKGROUND

The risk of femoral neck fracture progressively increases with age. However, the reasons behind this consistent increase in the fracture risk can't be completely justified by the decrease in the bone mineral density. The objective of this study was to analyze the correlation between various bone structural features and age.

STUDY DESIGN & METHODS

A total of 29 consecutive patients who suffered an intracapsular hip fracture and underwent joint replacement surgery between May 2012 and March 2013 were included in this study. A 2 cm × 1 cm Ø cylindrical trabecular bone sample was collected from the femoral heads and preserved in formaldehyde. Bone mineral density (BMD), microarchitecture, organic content and crystallography were analyzed using a Dual-energy X-ray absorptiometry scan, micro-CT scan, and high resolution magic-angle-spinning-nuclear magnetic resonance (MAS-NMR), respectively. Statistical correlations were made using Spearman´s or Pearson´s correlation tests depending on the distribution of the continuous variables.

RESULTS

The mean patient age was 79.83 ± 9.31 years. A moderate negative correlation was observed between age and the hydrogen content in bone (¹H), which is an indirect estimate to quantify the organic matrix (r = -0.512, p = 0.005). No correlations were observed between BMD, trabecular number, trabecular thickness, phosphorous content, apatite crystal size, and age (r = 0.06, p = 0.755; r = -0.008, p = 0.967; r = -0.046, p = 0.812; r = -0.152, p = 0.430, respectively). A weak positive correlation was observed between Charlson´s comorbidity index (CCI) and c-axis of the hydroxiapatite (HA) crystals (r = -0.400, p = 0.035).

CONCLUSION

The femoral head relative protein content progressively decreases with age. BMD was not correlated with other structural bone parameters and age. Patients with higher comorbidity scores had larger HA crystals. The present results suggest that the progressive increase in the hip fracture risk in elderly patients could be partially explained by the lower bone protein content in this age group.

Achieving enhanced bone regeneration using monetite granules with bone anabolic drug conjugates (C3 and C6) in rat mandibular defects

Bone grafting procedures are commonly used to manage bone defects in the craniofacial region. Monetite is an excellent biomaterial option for bone grafting, however, it is limited by lack of osteoinduction. Several molecules can be incorporated within the monetite matrix to promote bone regeneration. The aim was to investigate whether incorporating bone forming drug conjugates (C3 and C6) within monetite can improve their ability to regenerate bone in bone defects. Bilateral bone defects were created in the mandible of 24 Sprague-Dawley rats and were then packed with monetite control, monetite+C3 or monetite+C6. After 2 and 4 weeks, post-mortem samples were analyzed using microcomputed tomography, histology and back-scattered electron microscopy to calculate the percentages of bone formation and remaining graft material. At 2 and 4 weeks, monetite with C3 and C6 demonstrated higher bone formation than monetite control, while monetite+C6 had the highest bone formation percentage at 4 weeks. There were no significant differences in the remaining graft material between the groups at 2 or 4 weeks. Incorporating these anabolic drug conjugates within the degradable matrix of monetite present a promising bone graft alternative for bone regeneration and repair in orthopedic as well as oral and maxillofacial applications.

Chronotherapy of Non-Steroidal Anti-Inflammatory Drugs May Enhance Postoperative Recovery

Postoperative pain relief is crucial for full recovery. With the ongoing opioid epidemic and the insufficient effect of acetaminophen on severe pain; non-steroidal anti-inflammatory drugs (NSAIDs) are heavily used to alleviate this pain. However, NSAIDs are known to inhibit postoperative healing of connective tissues by inhibiting prostaglandin signaling. Pain intensity, inflammatory mediators associated with wound healing and the pharmacological action of NSAIDs vary throughout the day due to the circadian rhythm regulated by the clock genes. According to this rhythm, most of wound healing mediators and connective tissue formation occurs during the resting phase, while pain, inflammation and tissue resorption occur during the active period of the day. Here we show, in a murine tibia fracture surgical model, that NSAIDs are most effective in managing postoperative pain, healing and recovery when drug administration is limited to the active phase of the circadian rhythm. Limiting NSAID treatment to the active phase of the circadian rhythm resulted in overexpression of circadian clock genes, such as Period 2 (Per2) at the healing callus, and increased serum levels of anti-inflammatory cytokines interleukin-13 (IL-13), interleukin-4 (IL-4) and vascular endothelial growth factor. By contrast, NSAID administration during the resting phase resulted in severe bone healing impairment.

Biocompatibility and Durability of Diazonium Adhesives on Dental Alloys

PURPOSE

A new type of diazonium-based adhesive has been recently developed by our team to bind dental alloys (Titanium, stainless steel, and cobalt chromium) to dental polymers. Here, we explored the endurance of the resulting adhesive after thermal-cycling and autoclave aging.

MATERIALS AND METHODS

Polished samples of titanium (Ti), stainless steel (SS) and cobalt chromium (Co-Cr) were coated with a diazonium-based adhesive. Untreated samples served as controls (n = 12 per each condition). X-ray photoelectron spectroscopy (XPS) was performed to characterize the elemental compositions of the different surfaces. Biocompatibility of the coated alloys was assessed with human gingival fibroblasts (HGF). Inductively coupled plasma (ICP) and total organic carbon (TOC) analyses were used to quantify the ions and organic matters released from the diazonium coated alloys. Endurance of the adhesives was assessed by exposing the samples to autoclaving and thermal-cycling. The tensile strength of the poly(methylmethacrylate) (PMMA)-alloy bond was also tested.

RESULTS

Results of mechanical testing demonstrated a higher endurance of the coated CoCr, Ti, and SS compared to the uncoated alloys. The human fibroblasts cultured on the substrates remained alive and metabolically active, and the coatings did not release significant amounts of toxic chemicals in solutions.

CONCLUSIONS

The results further support the use of diazonium-based adhesives as new coupling agents for dental applications.

Low intensity pulsed ultrasound increases mandibular height and Col-II and VEGF expression in arthritic mice

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic inflammatory disease involving persistent inflammation resulting in cartilage and bone damage. RA can affect the temporomandibular joint (TMJ), and damage to the TMJ condyle can lead to craniofacial developmental disturbances, causing micrognathia, malocclusion, retrognathia, and increased overjet. Current treatments of TMJ arthritis are unsatisfactory. This pilot study aimed to investigate the effect of low intensity pulsed ultrasound (LIPUS) on the mandible and TMJ condyles in an RA mouse model using micro-computed tomography (Micro-CT), histologic, and immunohistochemical analyses.

METHODS

MRL-lpr/lpr mice received LIPUS application to their TMJs for 20 min/day for 2 and 4 weeks. Micro-CT analysis measured condylar length and width, posterior mandibular height (P.M.H), mandibular ramus length (M.R.L), effective mandibular length (Ef.M.L), angular process length (A.P.L), mandibular plane (M.P), mandibular axis (M.Ax), and lower incisor height (L.I.H). Condylar cartilage thickness was histologically measured, and type II collagen (Col-II), vascular endothelial growth factor (VEGF), nuclear factor kappa-B ligand (RANKL), and osteoprotegerin (OPG) expression was analyzed using immunohistochemistry.

RESULTS

Comparing the LIPUS-treated group with the control, P.M.H, M.R.L, and M.P were significantly greater in the LIPUS-treated group. Immunostaining for Col-II and VEGF was stronger in the LIPUS-treated group after 4 weeks. OPG showed slightly more expression in the LIPUS group.

CONCLUSIONS

LIPUS may enhance mandibular and TMJ condylar bone formation in this RA mouse model by preventing any growth disturbances involved in inflammation. Further studies are recommended to analyze the effect of LIPUS on TMJ of RA in other animal models.

Bone extracts immunomodulate and enhance the regenerative performance of dicalcium phosphates bioceramics

Immunomodulation strategies are believed to improve the integration and clinical performance of synthetic bone substitutes. One potential approach is the modification of biomaterial surface chemistry to mimic bone extracellular matrix (ECM). In this sense, we hypothesized that coating synthetic dicalcium phosphate (DCP) bioceramics with bone ECM proteins would modulate the host immune reactions and improve their regenerative performance. To test this, we evaluated the in vitro proteomic surface interactions and the in vivo performance of ECM-coated bioceramic scaffolds. Our results demonstrated that coating DCP scaffolds with bone extracts, specifically those containing calcium-binding proteins, dramatically modulated their interaction with plasma proteins in vitro, especially those relating to the innate immune response. In vivo, we observed an attenuated inflammatory response against the bioceramic scaffolds and enhanced peri-scaffold new bone formation supported by the increased osteoblastogenesis and reduced osteoclastogenesis. Furthermore, the bone extract rich in calcium-binding proteins can be 3D-printed to produce customized hydrogels with improved regeneration capabilities. In summary, bone extracts containing calcium-binding proteins can enhance the integration of synthetic biomaterials and improve their ability to regenerate bone probably by modulating the host immune reaction. This finding helps understand how bone allografts regenerate bone and opens the door for new advances in tissue engineering and bone regeneration. STATEMENT OF SIGNIFICANCE: Foreign-body reaction is an important determinant of in vivo biomaterial integration, as an undesired host immune response can compromise the performance of an implanted biomaterial. For this reason, applying immunomodulation strategies to enhance biomaterial engraftment is of great interest in the field of regenerative medicine. In this article, we illustrated that coating dicalcium phosphate bioceramic scaffolds with bone-ECM extracts, especially those rich in calcium-binding proteins, is a promising approach to improve their surface proteomic interactions and modulate the immune responses towards such biomaterials in a way that improves their bone regeneration performance. Collectively, the results of this study may provide a conceivable explanation for the mechanisms involved in presenting the excellent regenerative efficacy of natural bone grafts.

Marginal Discrepancies of Monolithic Zirconia Crowns: The Influence of Preparation Designs and Sintering Techniques

PURPOSE

The marginal fit is an essential component for the clinical success of prosthodontic restorations. The aim of this study was to investigate the influence of different abutment finish line widths and crown thicknesses on the marginal fit of zirconia crowns fabricated using either standard or fast sintering protocols.

MATERIALS AND METHODS

Six titanium abutments were fabricated for receiving zirconia molar crowns. Crowns were designed virtually and milled from partially sintered zirconia blanks and divided into 12 groups (n = 10/group). Crowns in groups 1 to 6 were sintered by standard sintering, while those in groups 7 to 12 were sintered by fast sintering. Groups were further categorized according to abutment finish line and crown thickness: G1/G7 (0.5 mm chamfer, 0.8 mm thick); G2/G8 (0.5 mm chamfer, 1.5 mm thick); G3/G9 (1.0 mm chamfer, 0.8 mm thick); G4/10 (1.0 mm chamfer, 1.5 mm thick); G5/G11 (1.2 mm chamfer, 0.8 mm thick); G6/G12 (1.2 mm chamfer, 1.5 mm thick). The marginal gaps were assessed at 8 locations using digital microscopy. The linear mixed effect model analysis was performed at a significance level of 0.05.

RESULTS

All vertical marginal gaps were within the clinically acceptable range (∼11-52 μm). G8 (FS, 0.5 mm chamfer, 1.5 mm thick) demonstrated the largest gaps (47.95 μm, 95% CI: 44.57-51.23), whereas G3 (SS, 1.0 mm chamfer, 0.8 thick) had the smallest marginal gap (14.43 μm, 95% CI: 11.15-17.71). A linear mixed effect models showed significant differences for the interaction between finish line × crown thickness × sintering (F = 18.96, p < 0.001). The lingual surfaces showed the largest gaps in both sintering protocols, while the mesial and mesiobuccal surfaces demonstrated the smallest gaps.

CONCLUSIONS

There was a significant interaction between finish line widths, crown thickness, and sintering protocol on the marginal gaps in both sintering protocols; 1.0 mm finish line preparations with either 0.8 mm or 1.5 mm occlusal reduction had better marginal fit in both sintering protocols compared to 0.5 mm or 1.2 mm finish lines. Smaller marginal discrepancies were observed for standard sintering crowns with a 0.5 mm finish line and 1.5 mm occlusal reduction. Conservative occlusal reduction should be accompanied with a 1.2 mm finish line to obtain better marginal fit for full-contoured zirconia crowns.

Combination of polyetherketoneketone scaffold and human mesenchymal stem cells from temporomandibular joint synovial fluid enhances bone regeneration

Therapies using human mesenchymal stem cells (MSCs) combined with three-dimensional (3D) printed scaffolds are a promising strategy for bone grafting. But the harvest of MSCs still remains invasive for patients. Human synovial fluid MSCs (hSF-MSCs), which can be obtained by a minimally invasive needle-aspiration procedure, have been used for cartilage repair. However, little is known of hSF-MSCs in bone regeneration. Polyetherketoneketone (PEKK) is an attractive bone scaffold due to its mechanical properties comparable to bone. In this study, 3D-printed PEKK scaffolds were fabricated using laser sintering technique. hSF-MSCs were characterized and cultured on PEKK to evaluate their cell attachment, proliferation, and osteogenic potential. Rabbit calvarial critical-sized bone defects were created to test the bone regenerative effect of PEKK with hSF-MSCs. In vitro results showed that hSF-MSCs attached, proliferated, and were osteogenic on PEKK. In vivo results indicated that PEKK seeded with hSF-MSCs regenerated twice the amount of newly formed bone when compared to PEKK seeded with osteogenically-induced hSF-MSCs or PEKK scaffolds alone. These results suggested that there was no need to induce hSF-MSCs into osteoblasts prior to their transplantations in vivo. In conclusion, the combined use of PEKK and hSF-MSCs was effective in regenerating critical-sized bone defects.

Comparative adsorption profiles of basal lamina proteome and gingival cells onto dental and titanium surfaces

Titanium (Ti) dental implants are susceptible to bacterial infections and failure due to lack of proper epithelial seal. Epithelial cells establish a strong epithelial seal around natural teeth by the deposition of basal lamina (BL) proteins that adsorb on the tooth surface. This seal can even be re-established onto cementum or dentin following injury or periodontal therapy. However, it is unclear how tooth surfaces promote this cell attachment and protein adsorption. Understanding the interactions between BL proteins and epithelial cells with dentin and Ti will facilitate the development of implant surfaces that promote the formation of an epithelial seal and improve the success of periodontal therapy and wound healing on natural teeth. To study these interactions, we used a surface proteomic approach to decipher the adsorption profile of BL proteins onto Ti and dentin, and correlated these adsorption profiles with in vitro interactions of human gingival fibroblasts and epithelial cells. Results showed that dentin adsorbed higher amounts of key BL proteins, particularly laminin and nidogen-1, and promoted more favorable interactions with epithelial cells than Ti. Next, dentin specimens were deproteinized or partially demineralized to determine if its mineral or protein component was responsible for BL adsorption and cell attachment. Deproteinized (mineral-rich) and partially demineralized (protein-rich) dentin specimens revealed BL proteins (i.e. laminin and nidogen-1) and epithelial cells interact preferentially with dentinal proteins rather than dentin mineral. These findings suggest that, unlike Ti, dentin and, in particular, dentinal proteins have a selective affinity to BL proteins that enhance epithelial cell attachment.

STATEMENT OF SIGNIFICANCE

It is remains unclear why natural teeth, unlike titanium dental implants, promote the formation of an epithelial seal that protects them against the external environment. This study used a surface screening approach to analyze the adsorption of proteins produced by epithelial tissues onto tooth-dentin and titanium surfaces, and correlate it with the behaviour of cells. This study shows that tooth-dentin, in particular its proteins, has a higher selective affinity to certain adhesion proteins, and subsequently allows more favourable interactions with epithelial cells than titanium. This knowledge could help in developing new approaches for re-establishing and maintaining the epithelial seal around teeth, and could pave the way for developing implants with surfaces that allow the formation of a true epithelial seal.

Strategies for Optimizing the Soft Tissue Seal around Osseointegrated Implants

Percutaneous and permucosal devices such as catheters, infusion pumps, orthopedic, and dental implants are commonly used in medical treatments. However, these useful devices breach the soft tissue barrier that protects the body from the outer environment, and thus increase bacterial infections resulting in morbidity and mortality. Such associated infections can be prevented if these devices are effectively integrated with the surrounding soft tissue, and thus creating a strong seal from the surrounding environment. However, so far, there are no percutaneous/permucosal medical devices able to prevent infection by achieving strong integration at the soft tissue-device interface. This review gives an insight into the current status of research into soft tissue-implant interface and the challenges associated with these interfaces. Biological soft/hard tissue interfaces may provide insights toward engineering better soft tissue interfaces around percutaneous devices. In this review, focus is put on the history and current findings as well as recent progress of the strategies aiming to develop a strong soft tissue seal around osseointegrated implants, such as orthopedic and dental implants.

Three-dimensionally printed polyetherketoneketone scaffolds with mesenchymal stem cells for the reconstruction of critical-sized mandibular defects

OBJECTIVE

Additive manufacturing offers a tailored approach to tissue engineering by providing anatomically precise scaffolds onto which stem cells and growth factors can be supplied. Polyetherketoneketone (PEKK), an ideal candidate biomaterial, is limited by a poor implant-bone interface but can be functionalized with adipose-derived stem cells (ADSC) to promote integration. This in vivo study examined the interaction of a three-dimensional printed PEKK/ADSC implant within the critical-sized mandibular defect in a rabbit model.

STUDY DESIGN/METHODS

Trapezoidal porous scaffolds with dimensions of 1.5 × 1.0 × 0.5 cm were printed using selective laser sintering. ADSCs were seeded on the scaffolds that were then implanted in marginal defects created in New Zealand rabbits. Rabbits were euthanized at 10- and 20-week intervals. Microcomputed tomography was used to characterize bone ingrowth and was correlated with histological analysis. Stress testing was performed on the scaffolds before and after implantation.

RESULTS

All scaffolds were well integrated into adjacent bone. Bone-to-tissue volume increased from 30.34% ( ± 12.46) to 61.27% ( ± 8.24), and trabecular thickness increased from 0.178 mm ( ± 0.069) to 0.331 mm ( ± 0.0306) in the 10- and 20-week groups, respectively, compared to no bone regrowth on the control side (P < 0.05). Histology confirmed integration at the bone-implant interface. Biomechanical testing revealed a compressive resistance 15 times that of bone alone (P < 0.05) CONCLUSION: 3D-printed PEKK scaffolds combined with ADSCs present a promising solution to improve the bone-implant interface and increase the resistance to forces of mastication after mandibular reconstruction.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E392-E398, 2017.

Biomaterial surface proteomic signature determines interaction with epithelial cells

Cells interact with biomaterials indirectly through extracellular matrix (ECM) proteins adsorbed onto their surface. Accordingly, it could be hypothesized that the surface proteomic signature of a biomaterial might determine its interaction with cells. Here, we present a surface proteomic approach to test this hypothesis in the specific case of biomaterial-epithelial cell interactions. In particular, we determined the surface proteomic signature of different biomaterials exposed to the ECM of epithelial cells (basal lamina). We revealed that the biomaterial surface chemistry determines the surface proteomic profile, and subsequently the interaction with epithelial cells. In addition, we found that biomaterials with surface chemistries closer to that of percutaneous tissues, such as aminated PMMA and aminated PDLLA, promoted higher selective adsorption of key basal lamina proteins (laminins, nidogen-1) and subsequently improved their interactions with epithelial cells. These findings suggest that mimicking the surface chemistry of natural percutaneous tissues can improve biomaterial-epithelial integration, and thus provide a rationale for the design of improved biomaterial surfaces for skin regeneration and percutaneous medical devices.

STATEMENT OF SIGNIFICANCE

Failure of most biomaterials originates from the inability to predict and control the influence of their surface properties on biological phenomena, particularly protein adsorption, and cellular behaviour, which subsequently results in unfavourable host response. Here, we introduce a surface-proteomic screening approach using a label-free mass spectrometry technique to decipher the adsorption profile of extracellular matrix (ECM) proteins on different biomaterials, and correlate it with cellular behaviour. We demonstrated that the way a biomaterial selectively interacts with specific ECM proteins of a given tissue seems to determine the interactions between the cells of that tissue and biomaterials. Accordingly, this approach can potentially revolutionize the screening methods for investigating the protein-cell-biomaterial interactions and pave the way for deeper understanding of these interactions.

Scaffolds for epithelial tissue engineering customized in elastomeric molds

Restoration of soft tissue defects remains a challenge for surgical reconstruction. In this study, we introduce a new approach to fabricate poly(d,l-lactic acid) (PDLLA) scaffolds with anatomical shapes customized to regenerate three-dimensional soft tissue defects. Highly concentrated polymer/salt mixtures were molded in flexible polyether molds. Microcomputed tomography showed that with this approach it was possible to produce scaffolds with clinically acceptable volume ratio maintenance (>90%). Moreover, this technique allowed us to customize the average pore size and pore interconnectivity of the scaffolds by using variations of salt particle size. In addition, this study demonstrated that with the increasing porosity and/or the decreasing of the average pore size of the PDLLA scaffolds, their mechanical properties decrease and they degrade more slowly. Cell culture results showed that PDLLA scaffolds with an average pore size of 100 µm enhance the viability and proliferation rates of human gingival epithelial cells up to 21 days. The simple method proposed in this article can be extended to fabricate porous scaffolds with customizable anatomical shapes and optimal pore structure for epithelial tissue engineering. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 880-890, 2018.

Three-Dimensional Printed Scaffolds with Multipotent Mesenchymal Stromal Cells for Rabbit Mandibular Reconstruction and Engineering

Multipotent mesenchymal stromal cells (MSC) derived from both the bone marrow and adipose tissue possess the ability to differentiate into multiple cell lineages, regulate the immune function by secreting numerous bioactive paracrine factors, and hold great potential in cell therapy and tissue engineering. When combined with three-dimensional (3D) scaffolds, MSC can be used for bone defect reconstruction and engineering. This protocol describes the isolation of bone marrow mesenchymal stromal cells (BMMSC) and adipose-tissue derived stem cells (ADSC) from rabbits for subsequent seeding on tissue-engineered 3D-printed scaffolds and transplantation into a rabbit-model with the goal of repairing large osseous mandibular defects (one quarter of the lower jaw is removed surgically). Steps to demonstrate the three cell differentiation lineage potentials of BMMSC and ADSC into osteocytes, adipocytes, and chondrocytes are described. A modified cell seeding method using syringes on scaffold is detailed. Creating a large mandibular bone defect, the rapid prototyping method to print a customized 3D-scaffold, the scaffold implantation procedure in rabbits, and microcomputed tomography (micro-CT) analysis are also described.

Two-Dimensional Magnesium Phosphate Nanosheets Form Highly Thixotropic Gels That Up-Regulate Bone Formation

Hydrogels composed of two-dimensional (2D) nanomaterials have become an important alternative to replace traditional inorganic scaffolds for tissue engineering. Here, we describe a novel nanocrystalline material with 2D morphology that was synthesized by tuning the crystallization of the sodium-magnesium-phosphate system. We discovered that the sodium ion can regulate the precipitation of magnesium phosphate by interacting with the crystal's surface causing a preferential crystal growth that results in 2D morphology. The 2D nanomaterial gave rise to a physical hydrogel that presented extreme thixotropy, injectability, biocompatibility, bioresorption, and long-term stability. The nanocrystalline material was characterized in vitro and in vivo and we discovered that it presented unique biological properties. Magnesium phosphate nanosheets accelerated bone healing and osseointegration by enhancing collagen formation, osteoblasts differentiation, and osteoclasts proliferation through up-regulation of COL1A1, RunX2, ALP, OCN, and OPN. In summary, the 2D magnesium phosphate nanosheets could bring a paradigm shift in the field of minimally invasive orthopedic and craniofacial interventions because it is the only material available that can be injected through high gauge needles into bone defects in order to accelerate bone healing and osseointegration.

Controlling Bone Graft Substitute Microstructure to Improve Bone Augmentation

Vertical bone augmentation procedures are frequently carried out to allow successful placement of dental implants in otherwise atrophic ridges and represent one of the most common bone grafting procedures currently performed. Onlay autografting is one of the most prevalent and predictable techniques to achieve this; however, there are several well documented complications and drawbacks associated with it and synthetic alternatives are being sought. Monetite is a bioresorbable dicalcium phosphate with osteoconductive and osteoinductive potential that has been previously investigated for onlay bone grafting and it is routinely made by autoclaving brushite to simultaneously sterilize and phase convert. In this study, monetite disc-shaped grafts are produced by both wet and dry heating methods which alter their physical properties such as porosity, surface area, and mechanical strength. Histological observations after 12 weeks of onlay grafting on rabbit calvaria reveal higher bone volume (38%) in autoclaved monetite grafts in comparison with the dry heated monetite grafts (26%). The vertical bone height gained is similar for both the types of monetite grafts (up to 3.2 mm). However, it is observed that the augmented bone height is greater in the lateral than the medial areas of both types of monetite grafts. It is also noted that the higher porosity of autoclaved monetite grafts increases the bioresorbability, whereas the dry heated monetite grafts having lower porosity but higher surface area resorb to a significantly lesser extent. This study provides information regarding two types of monetite onlay grafts prepared with different physical properties that can be further investigated for clinical vertical bone augmentation applications.

Diagenesis-inspired reaction of magnesium ions with surface enamel mineral modifies properties of human teeth

Mineralized tissues such as teeth and bones consist primarily of highly organized apatitic calcium-phosphate crystallites within a complex organic matrix. The dimensions and organization of these apatite crystallites at the nanoscale level determine in part the physical properties of mineralized tissues. After death, geological processes such as diagenesis and dolomitization can alter the crystallographic properties of mineralized tissues through cycles of dissolution and re-precipitation occurring in highly saline environments. Inspired by these natural exchange phenomena, we investigated the effect of hypersalinity on tooth enamel. We discovered that magnesium ions reacted with human tooth enamel through a process of dissolution and re-precipitation, reducing enamel crystal size at the surface of the tooth. This change in crystallographic structure made the teeth harder and whiter. Salt-water rinses have been used for centuries to ameliorate oral infections; however, our discovery suggests that this ancient practice could have additional unexpected benefits.

STATEMENT OF SIGNIFICANCE

Here we describe an approach inspired by natural geological processes to modify the properties of a biomineral - human tooth enamel. In this study we showed that treatment of human tooth enamel with solutions saturated with magnesium induced changes in the nanocrystals at the outer surface of the protective enamel layer. As a consequence, the physical properties of the tooth were modified; tooth microhardness increased and the color shade became whiter, thus suggesting that this method could be used as a clinical treatment to improve dental mechanical properties and esthetics. Such an approach is simple and straightforward, and could also be used to develop new strategies to synthesize and modify biominerals for biomedical and industrial applications.

Improving PEEK bioactivity for craniofacial reconstruction using a 3D printed scaffold embedded with mesenchymal stem cells

Objective

Polyetheretherketone (PEEK) is a bioinert thermoplastic that has been investigated for its potential use in craniofacial reconstruction; however, its use in clinical practice is limited by a poor integration with adjacent bone upon implantation. To improve the bone–implant interface, two strategies have been employed: to modify its surface or to impregnate PEEK with bioactive materials. This study attempts to combine and improve upon the two approaches by modifying the internal structure into a trabecular network and to impregnate PEEK with mesenchymal stem cells. Furthermore, we compare the newly designed PEEK scaffolds' interactions with both bone-derived (BMSC) and adipose (ADSC) stem cells.

Design

Customized PEEK scaffolds were designed to incorporate a trabecular microstructure using a computer-aided design program and then printed via selective laser sintering (SLS), a 3D-printing process with exceptional accuracy. The scaffold structure was evaluated using microCT. Scanning electron microscopy (SEM) was used to evaluate scaffold morphology with and without mesenchymal stem cells (MSCs). Adipose and bone marrow mesenchymal cells were isolated from rats and cultured on scaffolds. Cell proliferation and differentiation were assessed using alamarBlue and alkaline phosphatase assays, respectively. Cell morphology after one week of co-culturing cells with PEEK scaffolds was evaluated using SEM.

Results

SLS 3D printing fabricated scaffolds with a porosity of 36.38% ± 6.66 and density of 1.309 g/cm2. Cell morphology resembled viable fibroblasts attaching to the surface and micropores of the scaffold. PEEK scaffolds maintained the viability of both ADSCs and BMSCs; however, ADSCs demonstrated higher osteodifferentiation than BMSCs ( p < 0.05).

Conclusions

This study demonstrates for the first time that SLS 3D printing can be used to fabricate customized porous PEEK scaffolds that maintain the viability of adipose and bone marrow-derived MSCs and induce the osteodifferentiation of the adipose-derived MSCs. The combination of 3D printed PEEK scaffolds with MSCs could overcome some of the limitations using PEEK biopolymers for load-bearing bone regeneration in craniofacial reconstruction.

Mechanisms of in Vivo Degradation and Resorption of Calcium Phosphate Based Biomaterials

Calcium phosphate ceramic materials are extensively used for bone replacement and regeneration in orthopedic, dental, and maxillofacial surgical applications. In order for these biomaterials to work effectively it is imperative that they undergo the process of degradation and resorption in vivo. This allows for the space to be created for the new bone tissue to form and infiltrate within the implanted graft material. Several factors affect the biodegradation and resorption of calcium phosphate materials after implantation. Various cell types are involved in the degradation process by phagocytic mechanisms (monocytes/macrophages, fibroblasts, osteoblasts) or via an acidic mechanism to reduce the micro-environmental pH which results in demineralization of the cement matrix and resorption via osteoclasts. These cells exert their degradation effects directly or indirectly through the cytokine growth factor secretion and their sensitivity and response to these biomolecules. This article discusses the mechanisms of calcium phosphate material degradation in vivo.

Rehabilitation of a Completely Edentulous Patient with Nonreducible Bilateral Anterior Dislocation of the Temporomandibular Joint: A Prosthodontic Challenge-Clinical Report

Nonreduced bilateral anterior dislocation of the temporomandibular joint (TMJ) is an extremely rare condition, and its prosthodontic rehabilitation is a clinical challenge, especially in patients who refuse to or cannot undergo surgery. There are no previous clinical reports of successful or standardized prosthetic rehabilitation approaches for patients with this condition. This clinical report describes the successful prosthodontic management of an edentulous patient with nonreduced bilateral anterior dislocation of the TMJ.

Anti-VEGFs hinder bone healing and implant osseointegration in rat tibiae

AIM

To assess the effect of anti-vascular endothelial growth factors (VEGF) on bone healing (defect volume) and implant osseointegration (bone-implant contact per cent) in rat tibia.

MATERIALS AND METHODS

In Sprague-Dawley rats (n = 36), a unicortical defect was created in the right tibia and a titanium implant was placed in the left tibia of each rat. Rats were assigned into three groups and received either anti-vascular endothelial growth factor neutralizing antibody, Ranibizumab or saline (control). Two weeks following surgery, rats were euthanized and bone samples were retrieved. Bone healing and osseointegration were assessed using micro-CT and histomorphometry. One-way anova followed by the Tukey's test was used for data analyses.

RESULTS

The volume of the bone defects in the anti-VEGF group (2.48 ± 0.33 mm(3) ) was larger (p = 0.026) than in the controls (2.11 ± 0.36 mm(3) ) as measured by μ-CT. Bone-implant contact percent in the anti-VEGF (19.9 ± 9.4%) and Ranibizumab (21.7 ± 9.2%) groups were lower (p < 0.00) than in the control group (41.8 ± 12.4%).

CONCLUSIONS

The results of this study suggest that drugs that inhibit the activity of vascular endothelial growth factor (i.e. anti-VEGF) may hinder bone healing and implant osseointegration in rat tibiae.

Are interventions for accelerating orthodontic tooth movement effective?

DATA SOURCES

Pubmed, Embase, Sciences Citation Index, Cochrane Central Register of Controlled Trials (CENTRAL) and grey literature database of SIGLE were searched from January 1, 1990 to August 20, 2011 with no language restrictions.

STUDY SELECTION

Randomised controlled trials (RCTs) or quasi-RCTs in which the participants were healthy and received additional interventions to conventional orthodontic treatment for accelerating tooth movements were included. Subjects with defects in oral and maxillofacial regions (ie, cleft lip/palate), dental pathologies and medical conditions were excluded.

DATA EXTRACTION AND SYNTHESIS

Studies were selected by two independent reviewers and disagreements were resolved by discussion with a third reviewer. The primary outcomes included accumulative moved distance (AMD) or movement rate (MR) and time required to move the tooth to its destination. Secondary outcomes were pain improvement, anchorage loss, periodontal health, orthodontic caries, pulp vitality and root resorption. The reviewers performed statistical pooling, where possible, according to a priori criteria on the basis of comparability of patient type, treatments and outcomes measured and risk of bias. The reviewers tested for heterogeneity, publication bias and sensitivity. A quality assessment test was conducted to evaluate the method used to measure AMD.

RESULTS

The authors selected seven RCTs and two quasi-RCTs, which included a total of 101 patients with an age range of 12-26.3 years. Eight studies compared four intervention methods to no intervention group (control group). From them, four studies assessed low laser therapy (LLL), two evaluated corticotomy (CC), one assessed electrical current therapy (EC) and one evaluated pulsed electromagnetic field (PEF). Another study compared dentoalveolar distraction (DAD) vs periodontal distraction (PDD).Quality assessment scores showed that only two studies were of high quality, five studies were of medium quality, while two studies were of low quality. All studies, except one, compared left and right sides of the same participant (split mouth design), and measured the AMD.The method for measuring AMD was reliable in three studies, relatively reliable in one study and unreliable in four studies. The authors only performed pooled AMD mean meta-analysis for the LLL studies. The meta-analysis showed pooled mean AMD of 0.32 (95% confidence interval (CI), 20.04, 0.68), 0.76 (95% CI, 20.14, 1.65), and 0.73 (95% CI, 20.68, 2.14) for one month, two months and three months, respectively. Two LLL studies showed no differences regarding periodontal health and two LLL studies showed no differences in root resorption between LLL intervention and control groups. Compared to control group, one study reported that CS had significantly higher MR and another study showed that CS exhibited larger AMD for one month, two months, three months and four months. Two studies revealed that CS did not show any difference in the periodontal health status. One study reported the EC showed significantly larger AMD for one month, whereas another study reported that PEF induced larger AMD for five + 0.6 months. DAD showed faster MR and less anchorage loss compared to PDD. Teeth remained vital in both DAD and PDD interventions and one out of six cases presented root resorption in the PDD group.

CONCLUSIONS

Among the five interventions corticotomy is effective and safe to accelerate orthodontic tooth movement, low-level laser therapy was unable to accelerate orthodontic tooth movement. The level of evidence does not support whether electrical current and pulsed electromagnetic fields are effective in accelerating orthodontic tooth movement and dentoalveolar or periodontal distraction is promising in accelerating orthodontic tooth movement.

Matrix metalloproteinases and their pathological upregulation in multiple sclerosis: an overview

Matrix metalloproteinases (MMPs) are a family of extracellular proteases associated with extracellular matrix remodeling. They are involved in many physiological and reparative processes. MMPs can break down all extracellular constituents; therefore, their expression is very tightly regulated and their abnormal activity or over production has been linked to many diseases including multiple sclerosis (MS) which is a leading cause of non-traumatic disability in young adults in North America. Recently many studies, both in animals and humans, have been conducted to better elucidate the underlying causes, mechanisms and pathophysiology of MS. In this review, we discuss the potential role of pathological upregulation of MMPs in MS and future challenges which if properly addressed might help in development of potential cure for this disease.