Optimized bone grafting.

Bone grafting is routinely performed in periodontology and oral surgery to fill bone voids. While autogenous bone is considered the gold standard because of its regenerative properties, allografts and xenografts have more commonly been utilized owing to their availability as well as their differential regenerative/biomechanical properties. In particular, xenografts are sintered at high temperatures, which allows for their slower degradation and resorption rates and/or nonresorbable features. As a result, clinicians have combined xenografts with other classes of bone grafts (most notably allografts and autografts in various ratios) for procedures requiring better long-term stability, such as contour grafting, sinus elevation procedures, and vertical bone augmentations. This review addresses the regenerative properties of each class of bone grafts and then highlights the importance of understanding each of their biomechanical and regenerative properties for clinical applications, including extraction site management, contour augmentation, sinus grafting, and horizontal and vertical augmentation procedures. Thereafter, an introduction toward the novel production of nonresorbable bone allografts (NRBAs) via high-temperature sintering is presented. These NRBAs not only pose the advantage of being more biocompatible than xenografts owing to their origin (human vs. animal bone) but also display nonresorbable properties similar to those of xenografts. Thus, while packaging allografts with xenografts in premixtures specific to various clinical indications has never been permitted owing to cross-species contamination and FDA/CE requirements, the discovery and production of NRBAs allows premixing with standard allografts in various ratios without regulatory restrictions. Therefore, premixtures of allografts with NRBAs can be produced in various ratios for specific indications (e.g., a 1:1 ratio similar to an allograft/xenograft mixture for sinus grafting) without the need for purchasing separate classes of bone grafts. This optimized form of bone grafting could theoretically provide clinicians more precise ratios without the need to purchase separate bone grafts. This review highlights the future potential for simplified and optimized bone grafting in periodontology and implant dentistry

Understanding exosomes: Part 1-Characterization, quantification and isolation techniques.

Exosomes are the smallest subset of extracellular signaling vesicles secreted by most cells with a diameter in the range of 30-150 nm. Their use has gained great momentum recently due to their ability to be utilized as diagnostic tools with a vast array of therapeutic applications. Over 5000 publications are currently being published yearly on this topic, and this number is only expected to dramatically increase as novel therapeutic strategies continue to be investigated. This review article first focuses on understanding exosomes, including their cellular origin, biogenesis, function, and characterization. Thereafter, overviews of the quantification methods and isolation techniques are given with discussion over their potential use as novel therapeutics in regenerative medicine

Blood Clots versus PRF: Activating TGF-β Signaling and Inhibiting Inflammation In Vitro.

The preparation of platelet-rich fibrin (PRF) requires blood centrifugation to separate the yellow plasma from the red erythrocyte fraction. PRF membranes prepared from coagulated yellow plasma are then transferred to the defect sites to support tissue regeneration. During natural wound healing, however, it is the unfractionated blood clot (UBC) that fills the defect site. It is unclear whether centrifugation is necessary to prepare a blood-derived matrix that supports tissue regeneration. The aim of the present study was to compare lysates prepared from PRF and UBC based on bioassays and degradation of the respective membranes. We report here that lysates prepared from PRF and UBC membranes similarly activate TGF-β signaling, as indicated by the expression of interleukin 11 (IL-11), NADPH oxidase 4 (NOX-4) and proteoglycan 4 (PRG4) in gingival fibroblasts. Consistently, PRF and UBC lysates stimulated the phosphorylation and nuclear translocation of Smad3 in gingival fibroblasts. We further observed that PRF and UBC lysates have comparable anti-inflammatory activity, as shown by the reduction in lipopolysaccharide (LPS)-induced IL-6, inducible nitric oxidase synthase (iNOS) and cyclooxygenase 2 (COX-2) expression in RAW264.7 cells. Moreover, inflammation induced by Poly (1:C) HMW and FSL-1, which are agonists of Toll-like receptor (TLR) 3 and 2/6, respectively, was reduced by both PRF and UBC. PRF and UBC lysates reduced the nuclear translocation of p65 in LPS-induced RAW264.7 cells. In contrast to the similar activity observed in the bioassays, UBC membranes lack the structural integrity of PRF membranes, as indicated by the rapid and spontaneous disintegration of UBC membranes. We show here that the lysates prepared from PRF and UBC possess robust TGF-β and anti-inflammatory activity. However, visual inspection of the PRF and UBC membranes confirmed the negative impact of erythrocytes on the structural integrity of membranes prepared from whole blood. The data from the present study suggest that although both UBC and PRF have potent TGF-β and anti-inflammatory activity, UBC does not have the strength properties required to be used clinically to prepare applicable membranes. Thus, centrifugation is necessary to generate durable and clinically applicable blood-derived membranes

Fibrinogen Concentrations in Liquid PRF Using Various Centrifugation Protocols.

Liquid platelet-rich fibrin (PRF) is produced by fractionation of blood without additives that initiate coagulation. Even though liquid PRF is frequently utilized as a natural source of fibrinogen to prepare sticky bone, the concentration of fibrinogen and the overall amount of "clottable PRF" components have not been evaluated. To this aim, we prepared liquid PRF at 300, 700, and 2000 relative centrifugal force (RCF), for 8 min and quantified the fibrinogen levels by immunoassay. We report here that, independent of the RCF, the fibrinogen concentration is higher in the platelet-poor plasma (PPP) compared to the buffy coat (BC) fraction of liquid PRF and further decreases in the remaining red fraction. We then determined the weight of the clotted PRF fractions before and after removing the serum. The PPP and BC fractions consist of 10.2% and 25.3% clottable matrix suggesting that more than half of the weight of clottable BC is caused by cellular components. Our data provide insights into the distribution of fibrinogen in the different fractions of liquid PRF. These findings suggest that PPP is the main source of clottable fibrinogen, while the BC is more a cell source when it comes to the preparation of sticky bone

Osteoinduction and osteoimmunology: Emerging concepts.

The recognition and importance of immune cells during bone regeneration, including around bone biomaterials, has led to the development of an entire field termed "osteoimmunology," which focuses on the connection and interplay between the skeletal system and immune cells. Most studies have focused on the "osteogenic" capacity of various types of bone biomaterials, and much less focus has been placed on immune cells despite being the first cell type in contact with implantable devices. Thus, the amount of literature generated to date on this topic makes it challenging to extract needed information. This review article serves as a guide highlighting advancements made in the field of osteoimmunology emphasizing the role of the osteoimmunomodulatory properties of biomaterials and their impact on osteoinduction. First, the various immune cell types involved in bone biomaterial integration are discussed, including the prominent role of osteal macrophages (OsteoMacs) during bone regeneration. Thereafter, key biomaterial properties, including topography, wettability, surface charge, and adsorption of cytokines, growth factors, ions, and other bioactive molecules, are discussed in terms of their impact on immune responses. These findings highlight and recognize the importance of the immune system and osteoimmunology, leading to a shift in the traditional models used to understand and evaluate biomaterials for bone regeneration

Optimization of platelet-rich fibrin.

The use of platelet-rich fibrin (PRF) has gained tremendous popularity in recent years owing to its ability to speed wound healing postsurgery. However, to date, many clinicians are unaware of methods designed to optimize the technology. This overview article will discuss the advancements and improvements made over the years aimed at maximizing cell and growth factor concentrations. First, a general understanding explaining the differences between RPM and RCF (g-force) is introduced. Then, the low-speed centrifugation concept, fixed angle versus horizontal centrifugation, and methods to maximize platelet concentrations using optimized protocols will be discussed in detail. Thereafter, the importance of chemically modified PRF tubes without the addition of chemical additives, as well as regulation of temperature to induce/delay clotting, will be thoroughly described. This article is a first of its kind summarizing all recent literature on PRF designed to optimize PRF production for clinical treatment

Basis of bone metabolism around dental implants during osseointegration and periâ implant bone loss

Despite the growing number of publications in the field of implant dentistry, there are limited studies to date investigating the biology and metabolism of bone healing around dental implants and their implications in periâ implant marginal bone loss. The aim of this review article is to provide a thorough understanding of the biological events taking place during osseointegration and the subsequent early and late phases of bone remodeling around dental implants. An update on the coupling mechanism occurring during bone resorptionâ bone remodeling is provided, focused on the relevance of the osteocytes, bone lining cells and immune cells during bone maintenance. An electronic and manual literature search was conducted by three independent reviewers in several databases, including MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Cochrane Oral Health Group Trials Register databases for articles up to September 2016 with no language restriction. Local bone metabolism is subject to signals from systemic calciumâ phosphate homeostasis and bone remodeling. Three areas of interest were reviewed due to recent reported compromises in bone healing including the putative effects of (1) cholesterol, (2) hyperlipidemia, and (3) low vitamin D intake. Moreover, the prominent influence of osteocytes and immune cells is discussed as being key regulators during dental implant osseointegration and maintenance. These cells are of crucial importance in the presence of biofilm accumulation and their associated byproducts that leads to hard and soft tissue breakdown; the so called periâ implantitis. Factors that could negatively impact osteoclastogenesis or osteal macrophage activation should be monitored in future research including implant placement/torque protocols, bone characteristics, as well as meticulous maintenance programs to favor osseointegration and future longâ term stability and success of dental implants. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2075â 2089, 2017.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137387/1/jbma36060.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137387/2/jbma36060_am.pd

Ten years of injectable platelet-rich fibrin.

The use of platelet-rich fibrin (PRF) has seen widespread advantages over platelet-rich plasma (PRP) in many fields of medicine. However, until 2014, PRF remained clinically available only in its solid clotted form. Modifications to centrifugation protocols and tube technology have led to the development of a liquid injectable version of PRF (i-PRF). This narrative review takes a look back at the technological developments made throughout the past decade and further elaborates on their future clinical applications. Topics covered include improvements in isolation techniques and protocols, ways to further concentrate i-PRF, and the clinical impact and relevance of cooling i-PRF. Next, various uses of i-PRF are discussed, including its use in regenerative periodontology, implantology, endodontics, temporomandibular joint injections, and orthodontic tooth movement. Furthermore, various indications in medicine are also covered, including its use in sports injuries and osteoarthritis of various joints, treatment of diabetic ulcers/wound care, and facial esthetics and hair regrowth. Finally, future applications are discussed, mainly its use as a drug delivery vehicle for small biomolecules, such as growth factors, antibiotics, exosomes, and other medications that may benefit from the controlled and gradual release of biomolecules over time

Platelet-Rich Fibrin Decreases the Inflammatory Response of Mesenchymal Cells.

Chronic inflammation is a pathological process where cells of the mesenchymal lineage become a major source of inflammatory mediators. Platelet-rich fibrin (PRF) has been shown to possess potent anti-inflammatory activity in macrophages, but its impact on mesenchymal cells has not been investigated. The aim of this study was, therefore, to expose mesenchymal cells to inflammatory cytokines together with lysates generated from liquid platelet-poor plasma (PPP), the cell-rich buffy coat layer (BC; concentrated-PRF or C-PRF), and the remaining red clot layer (RC), following centrifugation of blood. Heating PPP generates an albumin gel (Alb-gel) that when mixed back with C-PRF produces Alb-PRF. Membranes prepared from solid PRF were also subjected to lysis. We report here that lysates of PPP, BC, and PRF decreased the cytokine-induced expression of interleukin 6 (IL6) and nitric oxide synthase (iNOS) in the bone marrow-derived ST2 cells. Consistently, PPP, BC, and PRF greatly decreased the phosphorylation and nuclear translocation of p65 in ST2 cells. The inflammatory response caused by Pam3CSK4 was reduced accordingly. Moreover, PPP, BC, and PRF reduced the enhanced expression of inflammatory mediators IL6 and iNOS in 3T3-L1 pre-adipocyte mesenchymal cells, and iNOS and CCL5 in murine calvarial cells. Surprisingly, PRF lysates were not effective in reducing the inflammatory response of human gingival fibroblasts and HSC2 epithelial cells. The data from the present study suggest that both liquid PRF and solid PRF exert potent anti-inflammatory activity in murine mesenchymal cells

Emerging factors affecting peri-implant bone metabolism.

Implant dentistry has evolved to the point that standard implant osseointegration is predictable. This is attributed in part to the advancements in material sciences that have led toward improvements in implant surface technology and characteristics. Nonetheless, there remain several cases where implant therapy fails (specifically at early time points), most commonly attributed to factors affecting bone metabolism. Among these patients, smokers are known to have impaired bone metabolism and thus be subject to higher risks of early implant failure and/or late complications related to the stability of the peri-implant bone and mucosal tissues. Notably, however, emerging data have unveiled other critical factors affecting osseointegration, namely, those related to the metabolism of bone tissues. The aim of this review is to shed light on the effects of implant-related factors, like implant surface or titanium particle release; surgical-related factors, like osseodensification or implanted biomaterials; various drugs, like selective serotonin reuptake inhibitors, proton pump inhibitors, anti-hypertensives, nonsteroidal anti-inflammatory medication, and statins, and host-related factors, like smoking, diet, and metabolic syndrome on bone metabolism, and aseptic peri-implant bone loss. Despite the infectious nature of peri-implant biological complications, these factors must be surveyed for the effective prevention and management of peri-implantitis